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11

Managing CoverCrops Profitably

Handbook Series Book 9Published by the Sustainable Agriculture Network, Beltsville, MD

A publication of the Sustainable Agriculture Network withfunding by the Sustainable Agriculture Research and Education

Program of CSREES, U.S. Department of Agriculture

THIRD EDITION

SUSTAINABLEAGRICULTURE NETWORK

This book was published in 2007 by the SustainableAgriculture Network (SAN) under cooperative agreementswith the Cooperative State Research, Education, andExtension Service,USDA, the University of Maryland and theUniversity of Vermont.

Every effort has been made to make this book as accurate aspossible and to educate the reader.This text is only a guide,however, and should be used in conjunction with other infor-mation sources on farm management.No single cover cropmanagement strategy will be appropriate and effective for allconditions.The editor/authors and publisher disclaim any lia-bility, loss or risk, personal or otherwise,which is incurred asa consequence, directly or indirectly, of the use and applica-tion of any of the contents of this book.

Mention, visual representation or inferred reference of aproduct, service,manufacturer or organization in this publi-cation does not imply endorsement by the USDA, the SAREprogram or the authors. Exclusion does not imply a negativeevaluation.

SARE works to increase knowledge about—and help farmersand ranchers adopt—practices that are profitable, environ-mentally sound and good for communities. For more informa-tion about SARE grant opportunities and informationalresources, go to www.sare.org. SAN is the national outreacharm of SARE. For more information, contact:

Sustainable Agriculture Network10300 Baltimore Ave.Bldg. 046 BARC-WESTBeltsville,MD 20705-2350(301) 504-5236; (301) 504-5207 (fax)[email protected]

To order copies of this book, ($19.00 plus $5.95 s/h)contact (301) 374-9696, [email protected], or order online atwww.sare.org.

Project manager and editor:Andy ClarkGraphic design and layout:Diane BuricInterior illustrations:Marianne Sarrantonio and Elayne SearsCopy editing:Andy ClarkProofreading:Aneeqa ChowdhuryIndexing:Claire BrannenPrinting:United Book Press, Inc.

Library of Congress Cataloging-in-Publication Data

Managing cover crops profitably / project manager andeditor, Andy Clark.—3rd ed.

p.cm. -- (SustainableAgriculture Network handbook series ;bk.9)

“A publication of the Sustainable Agriculture Networkwith funding by the Sustainable Agriculture Research andEducation Program of CSREES,U.S.Department ofAgriculture.”

Includes bibliographical references and index.ISBN 978-1-888626-12-4 (pbk.)1. Cover crops—United States—Handbooks,manuals, etc.

I. Clark, Andy. II. Sustainable Agriculture Network. III. Series.

SB284.3.U6M36 2007631.5'82—dc22

2007024273

Cover photos (clockwise from top left):Annual ryegrass overseeded into kale is already providingcover crop benefits before cash crop harvest. Photo byVern Grubinger,Univ. of VT.

Jeff Moyer, farm manager for The Rodale Institute, kills a hairyvetch cover crop with a newly designed, front-mountedroller while a no-till planter drops seed corn behind thetractor. Photo by Matthew Ryan for the Rodale Institute.

“Purple Bounty”hairy vetch, an early-maturing,winter hardyvariety for the Northeast,was developed by Dr.Tom Devine,USDA-ARS in collaboration withThe Rodale Institute,Pennsylvania State University and Cornell UniversityAgricultural Experiment Stations. Photo by Greg Bowman,NewFarm.org.

Guihua Chen, a Univ. of MD graduate student, studies theability of forage radish to alleviate soil compaction. Photo byRayWeil, Univ. of MD.

Red clover, frostseeded into winter wheat, is well establishedjust prior to wheat harvest. Photo by Steve Deming,MSU Kellogg Biological Station.

Back cover photo: Sorghum-sudangrass increased irrigatedpotato yield and tuber quality in Colorado,whether it washarvested for hay or incorporated prior to potato planting.Photo by Jorge A.Delgado,USDA-ARS.

Printed in the United States of America on recycled paper.

FOREWORD 3

Cover crops slow erosion, improve soil,smother weeds, enhance nutrient andmoisture availability, help control many

pests and bring a host of other benefits to yourfarm. At the same time, they can reduce costs,increase profits and even create new sources ofincome. You’ll reap dividends on your cover cropinvestments for years,because their benefits accu-mulate over the long term.

Increasing energy costs will have a profoundeffect on farm economics in coming years.As wego to press, it is impossible to predict how fastenergy costs will increase, but since cover cropeconomics are rooted in nitrogen dynamics (howmuch N you save or produce with cover crops),fuel costs (the cost of N and trips across the field)and commodity prices, energy prices will certain-ly impact the economics of cover crop use.

Economic comparisons in the 2nd edition werebased on the old economy of two-dollar corn,twenty-cent nitrogen and cheap gas. Some studiesshowed that cover crops become more profitableas the price of nitrogen increases. We retainedsome of these excellent studies because data fromnew studies is not yet available.What we do knowis that cover crops can help you to increase yields,save on nitrogen costs,reduce trips across the fieldand also reap many additional agronomic benefits.

There is a cover crop to fit just about everyfarming situation.The purpose of this book is tohelp you find which ones are right for you.

Farmers around the country are increasinglylooking at the long-term contributions of covercrops to their whole farm system. Some of themost successful are those who have seen the ben-efits and are committed to making cover cropswork for them.They are re-tooling their croppingsystems to better fit cover crop growth patterns,rather than squeezing cover crops into their exist-ing system, time permitting.

This 3rd edition of Managing Cover CropsProfitably aims to capture farmer and otherresearch results from the past ten years.We verifiedthe information from the 2nd edition, added new

results and updated farmer profiles and researchdata throughout.We also added two new chapters.Brassicas and Mustards (p. 81) lays out the

current theory and management of cover crops inthe BRASSICACEAE family. Brassica cover crops arethought to play a role in management of nema-todes, weeds and disease by releasing chemicalcompounds from decomposing residue. Resultsare promising but inconsistent. Try brassicas onsmall plots and consult local expertise for addi-tional information.Managing Cover Crops in Conservation

Tillage Systems (p.44) addresses the managementcomplexities of reduced tillage systems. If you arealready using cover crops, the chapter will helpyou reduce tillage. If you are already using con-servation tillage, it shows you how to add or bet-ter manage cover crops. Cover crops andconservation tillage team up to reduce energy useon your farm and that means more profits.

We have tried to include enough informationfor you to select and use cover crops appropriateto your operation.We recommend that you defineyour reasons for growing a cover crop—the sec-tion, Selecting the Best Cover Crops for YourFarm (p. 12) can help with this—and take asmuch care in selecting and managing cover cropsas you would a cash crop.

Regional and site-specific factors can complicatecover crop management. No book can adequatelyaddress all the variables that make up a crop pro-duction system.Before planting a cover crop, learnas much as you can from this book and talk to oth-ers who are experienced with that cover crop.

We hope that this updated and expanded edi-tion of Managing Cover Crops Profitably willlead to the successful use of cover crops on awider scale as we continue to increase the sus-tainability of our farming systems.

Andy Clark, CoordinatorSustainable Agriculture Network (SAN)June, 2007

FOREWORD

4 MANAGING COVER CROPS PROFITABLY

MANAGING COVER CROPS PROFITABLYTHIRD EDITION

Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 5How to Use this Book . . . . . . . . . . . . . . . . . . . . 7Benefits of Cover Crops . . . . . . . . . . . . . . . . . . 9Selecting the Best Cover Crops

forYour Farm. . . . . . . . . . . . . . . . . . . . . . . . 12Building Soil Fertility andTilth

with Cover Crops . . . . . . . . . . . . . . . . . . . . 16• Cover Crops Can StabilizeYour Soil . . . . 19• How Much N? . . . . . . . . . . . . . . . . . . . . . . 22

Managing Pests with Cover Crops . . . . . . . . . 25• Georgia Cotton, Peanut FarmersUse Cover Crops to Control Pests . . . . . . 26

• Select Covers that Balance Pests,Problems of Farm . . . . . . . . . . . . . . . . . . . 30

Crop Rotations with Cover Crops. . . . . . . . . . 34• Full-Year Covers Tackle ToughWeeds . . . 38• StartWhereYou Are . . . . . . . . . . . . . . . . . 41

Managing Cover Crops in ConservationTillage Systems. . . . . . . . . . . . . . . . . . . . . . . 44• After 25Years, ImprovementsKeep Coming . . . . . . . . . . . . . . . . . . . . . . . 52

Introduction to Charts. . . . . . . . . . . . . . . . . . . 62Chart 1: Top Regional Cover Crop Species . . 66Chart 2: Performance and Roles. . . . . . . . . . . 67Chart 3A: Cultural Traits . . . . . . . . . . . . . . . . . 69Chart 3B: Planting . . . . . . . . . . . . . . . . . . . . . . 70Chart 4A: Potential Advantages. . . . . . . . . . . . 71Chart 4B: Potential Disadvantages.. . . . . . . . . 72

COVER CROP SPECIESOverview of Nonlegume Cover Crops . . . 73Annual Ryegrass. . . . . . . . . . . . . . . . . . . . . . . . 74Barley . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77Brassicas and Mustards . . . . . . . . . . . . . . . . . . 81• Mustard Mix Manages Nematodes inPotato/Wheat System . . . . . . . . . . . . . . . . 86

Buckwheat . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90Oats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93• Oats, Rye Feed Soil inCorn/Bean Rotation. . . . . . . . . . . . . . . . . 96

Rye . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98• Cereal Rye: Cover CropWorkhorse . . . . 102• Rye SmothersWeeds Before Soybeans . 104

Sorghum Sudangrass Hybrids . . . . . . . . . . . . 106• Summer Covers Relieve Compaction . . 110

WinterWheat. . . . . . . . . . . . . . . . . . . . . . . . . 111•Wheat Boosts Income andSoil Protection . . . . . . . . . . . . . . . . . . . . . 113

•Wheat Offers High-VolumeWeed Control Too . . . . . . . . . . . . . . . . . . 114

Overview of Legume Cover Crops . . . . . 116Cover Crop Mixtures ExpandPossibilities . . . . . . . . . . . . . . . . . . . . . . . 117

Berseem Clover . . . . . . . . . . . . . . . . . . . . . . . 118• Nodulation:Match Inoculant toMaximize N . . . . . . . . . . . . . . . . . . . . . . . 122

Cowpeas . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125• Cowpeas Provide Elegant Solutionto Awkward Niche . . . . . . . . . . . . . . . . . 128

Crimson Clover . . . . . . . . . . . . . . . . . . . . . . . 130Field Peas . . . . . . . . . . . . . . . . . . . . . . . . . . . 135• Peas Do Double Duty for KansasFarmer . . . . . . . . . . . . . . . . . . . . . . . . . . . 140

Hairy Vetch. . . . . . . . . . . . . . . . . . . . . . . . . . . 142• Cover Crop Roller Design HoldsPromise for No-Tillers. . . . . . . . . . . . . . . 146

•Vetch Beats Plastic . . . . . . . . . . . . . . . . . . 150Medics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152• Jess Counts on GEORGE for N andFeed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153

• Southern Spotted Bur Medic offersReseeding Persistence . . . . . . . . . . . . . . . 154

ACKNOWLEDGMENTS 5

This 3rd edition could not have been written without the help of many cover crop experts. It isbased in large part on the content of the 2nd edition, researched and written by Greg Bowman,Craig Cramer and Christopher Shirley.The following people reviewed the 2nd edition, suggested

revisions and updates and contributed new content.

Aref Abdul-Baki, retired,USDA-ARSWesley Adams, Ladonia,TXKenneth A.Albrecht,Univ. ofWisconsinJess Alger, Stanford,MTRobert G. Bailey,USDA Forest ServiceKipling Balkcom,USDA-ARSRonnie Barentine,Univ. of GeorgiaPhil Bauer,USDA-ARSR. Louis Baumhardt,USDA-ARSRich and Nancy Bennett,Napoleon,OHValerie Berton, SARERobert Blackshaw,Agriculture andAgri-Food CanadaGreg Bowman,NewFarmRick Boydston,USDA-ARSLois Braun,Univ. of MinnesotaEric B. Brennan,USDA-ARSPat Carr,North Dakota State Univ.Max Carter,Douglas,GA

Guihua Chen,Univ. of MarylandAneeqa Chowdhury, SAREHal Collins,USDA-ARSCraig Cramer,Cornell Univ.Nancy Creamer,North Carolina State Univ.William S.Curran, The Pennsylvania State Univ.Seth Dabney,USDA-ARSBryan Davis,Grinnell, IAJorge Delgado,USDA-ARSJuan Carlos Diaz-Perez,Univ. of GeorgiaRichard Dick,Ohio State Univ.SjoerdW.Duiker, The Pennsylvania State Univ.GeraldW.Evers, Texas A&M Univ.Rick Exner, Iowa State Univ. ExtensionRichard Fasching,NRCSJim French, Partridge,KSEric Gallandt,Univ. of MaineHelen Garst, SARE

ACKNOWLEDGMENTS

Red Clover . . . . . . . . . . . . . . . . . . . . . . . . . . . 159Subterranean Clovers . . . . . . . . . . . . . . . . . . 164Sweetclovers . . . . . . . . . . . . . . . . . . . . . . . . . 171• Sweetclover: Good Grazing, GreatGreen Manure. . . . . . . . . . . . . . . . . . . . . 174

White Clover . . . . . . . . . . . . . . . . . . . . . . . . . 179• Clovers Build Soil, BlueberryProduction . . . . . . . . . . . . . . . . . . . . . . . . 182

WoollypodVetch . . . . . . . . . . . . . . . . . . . . . . 185

APPENDICESA.Testing Cover Crops onYour Farm . . . . . . 189B.Up-and-Coming Cover Crops. . . . . . . . . . . 191C. Seed Suppliers . . . . . . . . . . . . . . . . . . . . . . 195D. Farming Organizations with

Cover Crop Expertise . . . . . . . . . . . . . . . . 200E. Regional Experts . . . . . . . . . . . . . . . . . . . . 202F.Citations Bibliography . . . . . . . . . . . . . . . . 280G.Resources from the Sustainable

Agriculture Network . . . . . . . . . . . . . . . . . 230H.Reader Response Form . . . . . . . . . . . . . . . 232

INDEX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233


Dale Gies,Moses Lake,WABill Granzow,Herington,KSStephen Green, Arkansas State Univ.Tim Griffin,USDA-ARSSteve Groff,Holtwood, PAGary Guthrie,Nevada, IAMatthew Harbur,Univ. of MinnesotaTimothy M.Harrigan,Michigan State Univ.Andy Hart, Elgin,MNZane Helsel, Rutgers Univ.Paul Hepperly, The Rodale InstituteMichelle Infante-Casella, Rutgers Univ.Chuck Ingels, Univ. of CaliforniaLouise E. Jackson,Univ. of CaliforniaPeter Jeranyama, South Dakota State Univ.Nan Johnson,Univ. of MississippiHans Kandel, Univ. of Minnesota ExtensionTom Kaspar,USDA-ARSAlina Kelman, SARERose Koenig,Gainesville, FLJames Krall, Univ. ofWyomingAmy Kremen,Univ. of MarylandRoger Lansink,Odebolt, IAYvonne Lawley,Univ. of MarylandFrank Lessiter,No-Till FarmerJohn Luna,Oregon State Univ.Barry Martin,Hawkinsville,GATodd Martin,MSU Kellogg Biological StationMilt McGiffen,Univ. of CaliforniaAndy McGuire,Washington State Univ.George McManus, Benton Harbor,MIJohn J.Meisinger,USDA/ARSHenry Miller, Constantin,MIJeffrey Mitchell, Univ. of CaliforniaHassan Mojtahedi, USDA-ARSGaylon Morgan,Texas A&M Univ.Matthew J.Morra,Univ. of Idaho

Vicki Morrone,Michigan State Univ.Jeff Moyer, The Rodale InstitutePaul Mugge, Sutherland, IADale Mutch,MSU Kellogg Biological StationRob Myers, Jefferson InstituteLloyd Nelson, Texas Agric. Experiment StationMathieu Ngouajio,Michigan State Univ.Eric andAnne Nordell, Trout Run, PASharad Phatak,Univ. of GeorgiaDavid Podoll, Fullerton,NDPaul Porter,Univ. of MinnesotaAndrew Price,USDA-ARSEd Quigley, Spruce Creek, PARJ Rant,Grand Haven,MIBob Rawlins, Rebecca,GAWayne Reeves,USDA-ARSEkaterini Riga,Washington State Univ.Lee Rinehart, ATTRAAmanda Rodrigues, SARERon Ross,No-Till FarmerMarianne Sarrantonio,Univ. of MaineHarry H. Schomberg,USDA-ARSPat Sheridan, Fairgrove,Mich.Jeremy Singer,USDA-ARSRichard Smith,Univ. of CaliforniaSieglinde Snapp,Kellogg Biological StationLisa Stocking,Univ. of MarylandJames Stute,Univ. ofWisconsin ExtensionAlan Sundermeier,Ohio State Univ. ExtensionJohnTeasdale,USDA-ARSLee and NoreenThomas,Moorhead,MNDick and SharonThompson, Boone, IAEdzard van Santen, Auburn Univ.RayWeil, Univ. of MarylandCharlieWhite,Univ. of MarylandDaveWilson, The Rodale InstituteDavidWolfe, Cornell Univ.

HOW TO USE THIS BOOK 7

Think of this book as a tool chest,not a cook-book.You won’t find the one simple recipeto meet your farming goals. You will find

the tools to select and manage the best covercrops for the unique needs of your farm.

In this tool chest you will find helpful maps andcharts, detailed narratives about individual covercrop species, chapters about specific aspects ofcover cropping and extensive appendices thatwill lead you to even more information.

1. Start with Top Regional Cover Crop Species(p. 66). This chart will help you narrow yoursearch by listing the benefits you can expect fromthe top cover crops adapted to your region.You’lldiscover which are the best nitrogen (N) sources,soil builders, erosion fighters, subsoil looseners,weed fighters and pest fighters.

2.Next, find out more about the performance andmanagement of the cover crops that look likegood candidates for your farm. You’ll find twostreams of information:

• Charts quickly provide you with details tohelp you compare cover crops. Performance andRoles (p.67) lists ranges for N and dry matter pro-duction and ranks each cover crop’s potential forproviding 11 benefits.Cultural Traits (p. 69) andPlanting (p. 70) explains the growth, environ-mental tolerances, seeding preferences and estab-lishment costs for each crop.

• Narratives. The Table of Contents (p. 4)and the page numbers accompanying eachspecies in Charts 2,3 and 4 direct you to the heartof the book, the chapters on each cover crop.Thechapters offer even more practical descriptions ofhow to plant, manage, kill and make the best useof each species. Don’t overlook Up-and-ComingCover Crops (p. 191) that briefly describespromising but lesser known cover crops. One ofthem may be right for your farm.

3.With some particular cover crops in mind, stepback and look at the big picture of how you canfit cover crops into your farming operations. Sitdown with a highlighter and explore thesechapters:

• Benefits of Cover Crops (p.9) explains impor-tant cover crop roles such as reducing costs,improving soil and managing pests.

• Selecting the Best Cover Crops (p. 12) helpsyou evaluate your operation’s needs and niches(seasonal, cash-crop related, and profit potential).Several examples show how to fit crops todetailed situations.

• Building Soil Fertility andTilth (p.16) showshow cover crops add organic matter and greaterproductivity to the biological, chemical and phys-ical components of soil.

HOW TO USE THIS BOOK

SORGHUM-SUDANGRASS is a tall, warm-season grassthat stifles weeds and decomposes to build soil organicmatter.


• Managing Pests withCover Crops (p. 25)explores how covercrops change fieldenvironments toprotect cash cropsfrom insects, dis-ease, weeds andnematodes.

• New this edition:Managing Cover Cropsin Conservation TillageSystems (p. 44) provides man-agement details for cover crops inreduced tillage systems.

• Crop Rotations (p. 34) explains how to inte-grate cover crops and cash crops in sequencefrom year to year for optimum productivity fromon-farm resources.

• Citations Bibliography (p. 208) lists many ofthe publications and specialists cited in the book.Citations within the book are numbered in paren-theses. Refer to the numbered citation in the bib-liography if you want to dig deeper into a topic.

• Climatic Zone Maps inside the front andback covers help you understand differences incover crop performance from location to loca-tion. You may find that some cover crops haveperformed well in tests far from where you farm,but under comparable climatic conditions.

The USDA Plant Hardiness Zone Map (insidefront cover) shows whether a crop will survivethe average winter in your area.We refer to theUSDA hardiness zones throughout the book.Readers’ note: A new version of this map isexpected in 2008. See the online version of thisbook at www.sare.org.

The U.S. Forest Service map, Ecoregions ofthe United States (inside back cover), served inpart as the basis for the adaptation maps includedat the beginning of each cover crop chapter.Thisecosystem map, while designed to classify forestgrowth, shows localized climate differences, suchas rainfall and elevation, within a region. SeeBailey (citation #17 in Appendix F, p. 209) formore information about ecoregions.

4. Now that you’vetried out most of thetools, revisit the

charts and narrativesto zero in on the cover

crops you want to try.The Appendices include infor-

mation to help you run reliable on-farm cover crop comparison trials.You’ll also

find contact information for cover crop expertsin your region, seed and inoculant suppliers, ref-erences to books and academic papers cited inthis book and websites with more cover cropinformation.

5. Finally, share your cover crop plans with farm-ers in your area who have experience with covercrops.Your local Extension staff, regional IPM spe-cialist or a sustainable farming group in your areamay be able to provide contacts. Be sure to taplocal wisdom. You can find out the cover croppractices that have worked traditionally, and thenew wrinkles or crops that innovative practition-ers have discovered.

Abbreviations used in this bookA = acre or acresbu. = bushel or bushelsDM = dry matter, or dry weight of plant materialF = (degrees) Fahrenheit in. = inch or inchesK = potassium lb. = pound or poundsN = nitrogenOM = organic matterP = phosphorusp. = pagepp.= pagesT = ton or tons> = progression to another crop/ = a mixture of crops growing together

Cultivars of SUBTERRANEANCLOVER, a low-growing,

reseeding annual legume, areadapted to many climates.

BENEFITS OF COVER CROPS 9

BENEFITS OF COVER CROPS

Cover crops can boost your profits the firstyear you plant them. They can improveyour bottom line even more over the years

as their soil-improving effects accumulate. Otherbenefits—reducing pollution, erosion and weedand insect pressure—may be difficult to quantifyor may not appear in your financial statements.Identifying these benefits, however, can help youmake sound, long-term decisions for your wholefarm.

What follows are some important ways to eval-uate the economic and ecological aspects ofcover crops. These significant benefits (detailedbelow) vary by location and season, but at leasttwo or three usually occur with any cover crop.Consult local farming groups and agencies withcover crop experience to figure more precisecrop budgets.• Cut fertilizer costs• Reduce the need for herbicides and other

pesticides• Improve yields by enhancing soil health• Prevent soil erosion• Conserve soil moisture• Protect water quality• Help safeguard personal health

Evaluate a cover crop’s impact as you would anyother crop, balancing costs against returns in allforms. Don’t limit your calculations, however, tothe target cover crop benefit. A cover often hasseveral benefits. Many cover crops offer harvestpossibilities as forage, grazing or seed that workwell in systems with multiple crop enterprisesand livestock.

SPELLING IT OUT

Here’s a quick overview of benefits you can growon your farm.Cover crops can:

Cut fertilizer costs by contributing N to cashcrops and by scavenging and mining soil nutrients.

Legume cover crops convert nitrogen gas inthe atmosphere into soil nitrogen that plants canuse. See Nodulation: Match Inoculant toMaximize N (p. 122). Crops grown in fields afterlegumes can take up at least 30 to 60 percent ofthe N that the legume produced. You can reduceN fertilizer applications accordingly. For moreinformation on nitrogen dynamics and how tocalculate fertilizer reductions, see Building SoilFertility and Tilth with Cover Crops (p. 16).TheN value of legumes is the easiest cover cropbenefit to evaluate, both agronomically and eco-nomically. This natural fertility input alone canjustify cover crop use.

• Hairy vetch boosted yield for no-till cornmore than enough to cover its establishmentcosts, a three-year study in Maryland showed.Further, the vetch can reduce economic risk andusually will be more profitable than no-till cornafter a winter wheat cover crop (1993 data).Theresult held true even if corn were priced as low as$1.80 per bushel, or N fertilizer ($0.30/lb.) wasapplied at the rate of 180 lb.N/A (173).

•Medium red clover companion seeded withoats and hairy vetch had estimated fertilizerreplacement value of 65 to 103 lb. N/A in a four-year study inWisconsin,based on a two year rota-tion of oats/legume > corn.Mean corn grain yieldfollowing these legumes was 163 bu./A for red

RED CLOVER is an annual or multi-year legume thatimproves topsoil. It is easily overseeded into standingcrops or frostseeded into grains in early spring.

clover and 167 bu./A for hairy vetch, comparedwith a no legume/no N fertilizer yield of 134bu./A (400).

• Austrian winter peas, hairy vetch andNITRO alfalfa can provide 80 to 100 percent of asubsequent potato crop’s nitrogen requirement, astudy in the Pacific Northwest showed (394).

• Fibrous-rooted cereal grains or grasses areparticularly good at scavenging excess nutri-ents—especially N—left in the soil after cash cropharvest. Much of the N is held within the plantsuntil they decompose. Fall-seeded grains or grass-es can absorb up to 71 lb. N/A within threemonths of planting, a Maryland study showed(46). Addition of cover crops to corn>soybeanand corn>peanut>cotton rotations and appropri-ate timing of fertilizer application usually reducetotal N losses,without causing yield losses in sub-sequent crops, a USDA-ARS computer modelingstudy confirms (354).

Reduce the Need for HerbicidesCover crops suppress weeds and reduce damageby diseases, insects and nematodes. Many covercrops effectively suppress weeds as:• A smother crop that outcompetes weeds for

water and nutrients• Residue or growing leaf canopy that blocks

light, alters the frequency of light waves andchanges soil surface temperature

• A source of root exudates or compounds thatprovide natural herbicidal effects

Managing Pests with Cover Crops (p. 25)describes how cover crops can:• Host beneficial microbial life that discourages

disease• Create an inhospitable soil environment for

many soilborne diseases• Encourage beneficial insect predators and par-

asitoids that can reduce insect damage beloweconomic thresholds

• Produce compounds that reduce nematodepest populations

• Encourage beneficial nematode species

Using a rotation ofmalting barley>covercrop radish>sugarbeets has successfullyreduced sugar beetcyst nematodes toincrease yield of sugarbeets in a Wyomingtest. Using this brassi-ca cover crop aftermalting barley orsilage corn substitut-ed profitably forchemical nematicides when nematode levelswere moderate (231). A corn>rye>soybeans>wheat>hairy vetch rotation that has reducedpesticide costs is at least as profitable as conven-tional grain rotations without cover crops,a studyin southeastern Pennsylvania shows (174). Fall-planted brassica cover crops coupled withmechanical cultivation help potato growers witha long growing season maintain marketable yieldand reduce herbicide applications by 25 percentor more, a study in the inland Pacific Northwestshowed (394).

Improve Yields by Enhancing Soil HealthCover crops improve soil by:• Speeding infiltration of excess surface water• Relieving compaction and improving struc-

ture of overtilled soil• Adding organic matter that encourages

beneficial soil microbial life• Enhancing nutrient cycling

Building Soil Fertility and Tilth with CoverCrops (p. 16) details the biological and chemicalprocesses of how cover crops improve soil healthand nutrient cycling. Leading soil-building cropsinclude rye (residue adds organic matter and con-serves moisture); sorghum-sudangrass (deep pen-etrating roots can break compaction); andryegrass (stabilizes field roads, inter-row areas andborders when soil is wet).


To estimate

your potential N

fertilizer savings

from a cover

crop, see the

sidebar, How

Much N? (p. 22).

Prevent Soil ErosionQuick-growing cover crops hold soil in place,reduce crusting and protect against erosion dueto wind and rain.The aboveground portion of cov-ers also helps protect soil from the impact of rain-drops. Long-term use of cover crops increaseswater infiltration and reduces runoff that cancarry away soil.The key is to have enough stalkand leaf growth to guard against soil loss.Succulent legumes decompose quickly, especiallyin warm weather. Winter cereals andmany brassicas have a better chanceof overwintering in colder climates.These late-summer or fall-plantedcrops often put on significant growtheven when temperatures drop intothe 50s,and often are more winter-hardy than legumes (361). In a no-till cotton system, use of covercrops such as winter wheat,crimsonclover and hairy vetch can reduce soilerosion while maintaining high cot-ton yields, a Mississippi study shows(35).

Conserve Soil MoistureResidue from killed cover crops increaseswater infiltration and reduces evap-oration, resulting in less moisture stressduring drought. Lightly incorporatedcover crops serve dual roles. Theytrap surface water and add organicmatter to increase infiltration to theroot zone. Especially effective atcovering the soil surface are grass-type cover crops such as rye,wheat, and sorghum-sudangrasshybrid. Some water-efficientlegumes such as medic andINDIANHEAD lentils provide covercrop benefits in dryland areaswhile conserving more moisture

than conventional bare fallow (383). Timelyspring termination of a cover crop avoids the neg-ative impact of opposite water conditions: excessresidue holding in too much moisture for plantingin wet years, or living plants drawing too muchmoisture from the soil in dry years.

Protect Water QualityBy slowing erosion and runoff, cover cropsreduce nonpoint source pollution caused by sed-iments, nutrients and agricultural chemicals. Bytaking up excess soil nitrogen, cover crops pre-vent N leaching to groundwater. Cover crops

also provide habitat for wildlife. A ryecover crop scavenged from 25 to 100percent of residual N from conven-tional and no-till Georgia cornfields, one study showed. Up to180 lb. N/A had been applied. Abarley cover crop removed 64 per-

cent of soil nitrogen when appliedN averaged 107 lb./A (220).

Help Safeguard Personal HealthBy reducing reliance on agrichemicalsfor cash crop production, cover cropshelp protect the health of your family,neighbors and farm workers. Theyalso help address community healthand ecological concerns arising fromnonpoint source pollution attributedto farming activities.

Cumulative BenefitsYou can increase the range of ben-efits by increasing the diversity ofcover crops grown, the frequen-cy of use between cash cropsand the length of time thatcover crops are growing in thefield.

BENEFITS OF COVER CROPS 11

WINTER WHEAT grows well in fall, then provides forage and protects soil over winter.


Cover crops provide many benefits, butthey’re not do-it-all“wonder crops.” To finda suitable cover crop or mix of covers:

• Clarify your primary needs• Identify the best time and place for a cover

crop in your system• Test a few options

This book makes selection of cover crops a little eas-ier by focusing on some proven ones.Thousands ofspecies and varieties exist, however. The steps thatfollow can help you find crops that will work bestwith a minimum of risk and expense.

1. Identify Your Problem or UseReview Benefits of Cover Crops (p. 9) to decidewhat you want most from a cover crop.Narrowing your goals to one or two primary andperhaps a few secondary goals will greatly simpli-fy your search for the best cover species. Somecommon goals for cover crops are to:• Provide nitrogen• Add organic matter• Improve soil structure• Reduce soil erosion• Provide weed control• Manage nutrients• Furnish moisture-conserving mulch

You might also want the cover crops to providehabitat for beneficial organisms, better tractionduring harvest, faster drainage or another benefit.

2. Identify the Best Place and TimeSometimes it’s obvious where and when to use acover crop.You might want some nitrogen beforea corn crop,or a perennial ground cover in a vine-yard or orchard to reduce erosion or improveweed control. For some goals, such as buildingsoil, it may be hard to decide where and when toschedule cover crops.

To plan how and where to use cover crops, trythe following exercise:

Look at your rotation.Make a timeline of 18 to36 monthly increments across a piece of paper.For each field, pencil in current or probable rota-tions, showing when you typically seed crops andwhen you harvest them.

If possible, add other key information, such asrainfall, frost-free periods and times of heavy laboror equipment demand.

Look for open periods in each field that corre-spond to good conditions for cover crop estab-lishment, underutilized spaces on your farm, aswell as opportunities in your seasonal workschedule. Also consider ways to extend or overlapcropping windows.

Here are examples of common niches in somesystems, and some tips:Winter fallow niche. In many regions, seed

winter covers at least six weeks before a hardfrost.Winter cereals, especially rye, are an excep-tion and can be planted a little later. If groundcover and N recycling needs are minimal, rye canbe planted as late as the frost period for success-ful overwintering.

You might seed a cover right after harvesting asummer crop, when the weather is still mild. Incooler climates, consider extending the windowby overseeding (some call this undersowing) ashade-tolerant cover before cash crop harvest.White clover, annual ryegrass, rye, hairy vetch,crimson clover, red clover and sweetclover toler-ate some shading.

If overseeding, irrigate afterwards if possible,orseed just before a soaking rain is forecast. Specieswith small seeds, such as clovers, don’t need a lotof moisture to germinate and can work their waythrough tiny gaps in residue, but larger-seededspecies need several days of moist conditions togerminate.

SELECTING THE BEST COVER CROPSFOR YOUR FARMby Marianne Sarrantonio

SELECTING THE BEST COVER CROPS 13

When overseeding into cash crops early in theseason, vigorous growth of the cover crop maycause water stress, increase disease risks due tolower air circulation or create new insect pestrisks. Changing cover crop seeding rate, seedingtime, or the rotation sequence may lessen thisrisk. To ensure adequate sunlight for the covercrop, overseed before full canopy closure of theprimary crop (at last cultivation of field corn, forexample) or just before the canopy starts to openagain as the cash crop starts to die (as soybeanleaves turn yellow, for example).

Expect excessive field traffic around harvesttime? Choose tough, low-growing covers such asgrasses or clovers. Limit foot traffic to alternaterows, or delay a field operation to allow for covercrop establishment.

Another option could be to use a reseedingwinter annual that dies back and drops seed eachsummer but reestablishes in fall. Subcloversreseed well in regions south of Hardiness Zone 6.Shorter-season crimson clovers—especially vari-eties with a high hard-seed percentage that ger-minate over an extended period—work well inthe Southeast where moisture is sufficient. Evenrye and vetch can reseed if managed properly.Summer fallow niche. Many vegetable rota-

tions present cover crop opportunities—andchallenges. When double cropping, you mighthave fields with a three- to eight-week summer fal-low period between early planted and late plant-ed crops.Quick-growing summer annuals provideerosion control, weed management, organic mat-ter and perhaps some N.

Consider overseeding a spring crop with aquick-growing summer grain such as buckwheat,millet or sorghum-sudangrass, or a warm-seasonlegume such as cowpeas. Or, you might till outstrips in the cover crop for planting a fall veg-etable crop and control the remaining coverbetween the crop rows with mowing or light cul-tivation.Small grain rotation niche. Companion seed a

winter annual cover cropwith a spring grain,or frostseed (broadcasting seed onto frozen ground) a coverinto winter grains. Soil freezing and thawing pullsseed into the soil and helps germination. Anotheroption if soil moisture isn’t a limiting factor in your

region: broadcast a coverbefore the grain entersboot stage (when seed-heads start elongating)later in spring or plantafter harvest.Full-year improved

fallow niche. To rebuildfertility or organic matterover a longer period,perennials or biennials—or mixtures—requirethe least amount of maintenance. Spring-seededyellow blossom sweetclover flowers the follow-ing summer, has a deep taproot and gives plentyof aboveground biomass.Also consider perennialforages recommended for your area. The below-ground benefit of a tap rooted perennial can havetremendous soil improving benefits whenallowed to grow for several years.

Another option is sequential cover cropping.Plant hairy vetch or a grass-legume mixture in fall,terminate it the following spring at flowering,andplant sorghum-sudangrass.The winter cover cropprovides weed suppression and ground cover,butalso nitrogen for the high-N sorghum-sudangrass,which can produce tons of biomass to build soilorganic matter.

Properly managed, living mulches give manygrowers year-round erosion protection, weedcontrol, nutrient cycling and even some nitrogenif they include a legume. Some tillage,mowing orherbicides can help manage the mulch (to keep itfrom using too much soil moisture, for example)before crops are strip-tilled into the cover orresidue.White clover could be a good choice forsweet corn and tomatoes. Perennial ryegrass orsome less aggressive turfgrasses such as sheep fes-cue may work for beans, tomatoes and other veg-etables.Create new opportunities. Have you honed

a rotation that seems to have few open time slots?Plant a cover in strips the width of a bed or wider,alternating with your annual vegetable, herb orfield crop. Switch the strips the next year. Mowthe strips periodically and blow the topgrowthonto adjoining cash crops as mulch. In a bedsystem, rotate out every third or fourth bed for asoil-building cover crop.

Look for open

periods in

each field or

open spaces

on your farm.


Another option: Band a cover or some insect-attracting shrubs around fields or alonghedgerows to suppress weeds or provide benefi-cial habitat where you can’t grow cash crops.These hedgerows could also be used to producemarketable products such as nuts,berries or evencraft materials.

3. Describe the NicheRefer to your timeline chart and ask questionssuch as:• How will I seed the cover?• What’s the weather likely to be then?• What will soil temperature and moisture

conditions be like?• How vigorous will other crops (or pests) be?• Should the cover be low-growing and

spreading, or tall and vigorous?• What weather extremes and field traffic must

it tolerate?• Will it winterkill in my area?• Should it winterkill, to meet my goals?• What kind of regrowth can I expect?• How do I kill it and plant into it?• Will I have the time to make this work?• What’s my contingency plan—and risks—if

the crop doesn’t establish or doesn’t die onschedule?

• Do I have the needed equipment and labor?

4. Select the Best Cover CropYou have identified a goal,a time and a place,nowspecify the traits a cover crop would need towork well.

Example 1. A sloping orchard needs a groundcover to reduce erosion. You’d like it to con-tribute N and organic matter and attract ben-eficial organisms but not rodents,nematodes orother pests. The cover can’t use too muchwater or tie up nutrients at key periods. Toomuch N might stimulate excessive tree leafgrowth or prevent hardening off before winter.Finally you want a cover crop that is easy to main-tain. It should:• be a perennial or reseeding annual• be low-growing, needing minimal

management

• use water efficiently• have a soil-improving root system• release some nutrients during the year, but not

too much N• not harbor or attract pests

For this orchard scenario,white clover is probablythe best option north of Zone 8. A mixture oflow-growing legumes or a legume and grass mixcould also work. In warm regions, low-growingclovers such as strawberry clover and white cloverwork well together, although these species mayattract pocket gophers. BLANDO brome and annualryegrass are two quick-growing, reseeding grassesoften suitable for orchard floors,but they will prob-ably need some control with mowing. Or, try areseeding winter annual legume such as crimsonclover, rose clover, subclover,an annual vetch or anannual medic,depending on your climate.

Example 2. A dairy lacks adequate storage in falland winter for the manure it generates, whichexceeds the nutrient needs for its silage cornand grass/legume hay rotation. The cover cropneeds to:• establish effectively after (or tolerate) silage

corn harvest• take up a lot of N and P from fall-applied

manure and hold it until spring

For this dairy scenario, rye is usually the bestchoice. Other cereal grains or brassicas couldwork if planted early enough.

HAIRY VETCH is an winter annual legume thatgrows slowly in fall, then fixes a lot of N in spring.

SELECTING THE BEST COVER CROPS 15

Example 3. In a moderate rainfall region aftersmall grain harvest in late summer, you want asoil-protecting winter cover that can supplyN for no-till corn next spring.You want to kill thecover without herbicides.You need a legume that:• can be drilled in late summer and put on a lot

of fall growth• will overwinter• will fix a lot of N• can be mow-killed shortly before (or after)

corn planting• could provide some weed-controlling,

moisture-conserving residue

Hairy vetch works well in the Northeast, Midwestand parts of the mid-South. Mixing it with rye oranother cereal improves its weed-management andmoisture-conservation potential. Crimson clovermay be an appropriate choice for the southeasternPiedmont. Austrian winter pea could be considered,alone or in a mix, in coastal plain environments,butwill winterkill in Zone 7 and below.Where grain har-vest occurs in late spring or early summer, LANAwoollypod vetch might be a better choice.

Example 4. After a spring broccoli crop, youneed a weed-suppressing cover that adds Nand organic matter, and perhaps mulch, intowhich you will no-till seed fall lettuce or spinach.You want a cover that:• is very versatile• grows fast in hot weather• can be overseeded into broccoli• germinates on the soil surface under dry

conditions• fixes N• persists until you’re ready to kill it

Here,a quick-growing,warm-season legume such ascowpeas may work, especially if you can irrigate tohasten establishment during dry conditions.

5. Settle for the Best Available Cover. It’s like-ly the “wonder crop”you want doesn’t exist.Oneor more species could come close, as the aboveexamples indicate. Top Regional Cover CropSpecies (p.66) can provide a starting point.Check

with regional experts. Keep in mind that you canmix two or more species,or try several options insmall areas.

6. Or Build a Rotation Around Cover Crops.It’s hard to decide in advance every field’s crops,planting dates, fieldwork or managementspecifics. One alternative is to find out whichcover crops provide the best results on your farm,then build a rotation around those covers, espe-cially when trying to tackle some tough soilimprovement or weed control issues. See Full-Year Covers Tackle ToughWeeds (p. 38).

With this “reverse” strategy, you plan coversaccording to their optimum field timing,and thendetermine the best windows for cash crops. Acover crop’s strengths help you decide whichcash crops would benefit the most.

For now,however,you probably want to fit oneor more cover crops into your existing rotations.The charts and narratives in this book can helpyou select some of the most suitable species foryour farming system and objectives. See CropRotations with Cover Crops (p. 34) to get youthinking more. When you’ve narrowed yourchoices, refer to Appendix A,Testing Cover Cropson Your Farm (p. 189) for some straightforwardtips on what to do next.

Adapted fromNortheast Cover Crop Handbook byMarianne Sarrantonio, Rodale Institute, 1994.

WINTER (cereal) RYE is an annual grain thatprevents soil and wind erosion. Its killed vegetationsuppresses weeds for no-till planting.


Soil is an incredibly complex substance. It hasphysical and chemical properties that allowit to sustain living organisms—not just plant

roots and earthworms,but hundreds of thousandsof different insects, wormlike creatures andmicroorganisms.When these organisms are in bal-ance, your soil cycles nutrients efficiently, storeswater and drains the excess, and maintains anenvironment in which plants can thrive.

To recognize that a soil can be healthy, one hasonly to think of the soil as a living entity. Itbreathes, it transports and transforms nutrients, itinteracts with its environment, and it can evenpurify itself and grow over time. If you view soilas a dynamic part of your farming system, unsus-tainable crop management practices amount tosoil neglect.That neglect could worsen as the soilsickens and loses its life functions one by one.

Regardless of how healthy or alive your soil isright now, cover crops can play a vital role inensuring that your soil provides a strong founda-tion for your farming system.While the most com-mon reasons for including cover crops in afarming system may relate to the immediate short-term need, the continued practice of cover crop-ping becomes an investment in building healthysoil over the long term.

Cover crops improve soil in a number of ways.Protection against soil loss from erosion is per-haps the most obvious soil benefit of cover crops,but providing organic matter is a more long-termand equally important goal. Cover crops con-tribute indirectly to overall soil health by catchingnutrients before they can leach out of the soilprofile or, in the case of legumes, by addingnitrogen to the soil. Their roots can even helpunlock some nutrients, converting them to moreavailable forms. Cover crops provide habitat or afood source for some important soil organisms,break up compacted layers in the soil and helpdry out wet soils.

EROSION PROTECTION

Erosion of topsoil occurs on many farms, depriv-ing fields of the most fertile portion, that contain-ing the highest percentage of organic matter andnutrients. Cover crops can play a major role infighting soil erosion.

A raindrop falling at high speed can dislodgesoil particles and cause them to move as far as 6feet (42). Once a soil particle is loose, it is muchmore vulnerable to being carried away by run-ning water.Any aboveground soil cover can takesome of the punch out of a heavy rainfall simplyby acting as a cushion for raindrops.

A cover crop also can:• Slow the action of moving water, thus reduc-

ing its soil-carrying capacity, by creating anobstacle course of leaves, stems and rootsthrough which the water must maneuver onits way downhill

• Increase the soil’s ability to absorb and holdwater, through improvement in pore structure,thereby preventing large quantities of waterfrom moving across the soil surface

• Help stabilize soil particles in the cover croproot system

The reduction in soil erosion due to cover crop-ping will be roughly proportional to the amountof cover on the soil. The Revised Universal SoilLoss Equation developed by the NaturalResources Conservation Service predicts that asoil cover of just 40 percent when winter arrivescan reduce erosion substantially until spring.

It’s worthwhile to get covers established early,to ensure that maximum soil cover developsbefore winter rains. Consider overseeding coversat layby cultivation,aerial seeding or hand spread-ing before harvest, or planting as soon as possibleafter harvest. It’s always a good idea to maintainyear-round soil cover whenever possible.

BUILDING SOIL FERTILITY AND TILTHWITH COVER CROPSby Marianne Sarrantonio

BUILDING SOIL FERTILITY AND TILTH 17

ORGANIC MATTER ADDITIONS

The benefits of organic matter include improvedsoil structure, increased infiltration andwater-holding capacity, increased cationexchange capacity (the ability of the soil to actas a short-term storage bank for positively chargedplant nutrients) and more efficient long-termstorage of nutrients.Without organic matter, youhave no soil to speak of, only a dead mixture ofground-up and weathered rocks.

Organic matter includes thousands of differentsubstances derived from decayed leaves, roots,microorganisms, manure and even groundhogsthat died in their burrows.These substances func-tion in different ways to build healthy soil.Different plants leave behind different kinds oforganic matter as they decompose,so your choiceof cover crop will largely determine which soilbenefits you will receive.

Soil scientists may argue over how to classifythe various soil organic components. Most willagree,however, that there is a portion that can becalled the “active” fraction, and one that mightbe called the “stable” fraction,which is roughlyequivalent to humus.There are many categoriesin between the active and stable fractions.

The active fraction represents the most easilydecomposed parts of soil organic matter. It tendsto be rich in simple sugars and proteins and con-sists largely of recently added fresh residues,microbial cells and the simpler waste productsfrom microbial decay.

Because microorganisms, like human organ-isms, crave sweet stuff, compounds containingsimple sugars disappear quickly. Proteins also areselected quickly from the menu of edible soilgoodies. When these compounds are digested,many of the nutrients that they contain arereleased into the soil.Proteins are nitrogen-rich,sothe active fraction is responsible for the releaseof most N, as well as some K, P and other nutri-ents, from organic matter into the soil.The easi-ly decomposed proteins and sugars burn upalmost completely as energy sources, and don’tleave much behind to contribute to organicmatter building.

After the microorganisms have devoured theportions of the active fraction that are easiest todigest, a more dedicated subset of these micro-organisms will start munching on the morecomplex and tough material, such as cellulosesand lignins, the structural materials of plants.Since cellulose is tougher than simple sugars, andlignin breaks down very slowly, they contributemore to the humus or stable fraction. Humus isresponsible for giving the soil that rich, dark,spongy feeling and for properties such as waterretention and cation exchange capacity.Plant materials that are succulent and rich

in proteins and sugars will release nutrients rapid-ly but leave behind little long-term organic matter.Plant materials that are woodier or morefibrous will release nutrients much more slowly,perhaps even tie up nutrients temporarily (seeTillage, No Tillage and N Cycling, p. 21), but willpromote more stable organic matter, or humus,leading to better soil physical conditions,increased nutrient-holding capacity and highercation exchange capacity.

In general, annual legumes are succulent.Theyrelease nitrogen and other nutrients quicklythrough the active fraction,but are not very effec-tive at building up humus.Long-term use of annu-al legumes can increase soil humus, however,some research suggests (429).

Grains and other grasses and nonlegumes willcontribute to humus production, but won’trelease nutrients very rapidly or in large quantitiesif incorporated as they approach maturity.Perennial legumes such as white and red clovermay fall in both categories—their leaves willbreak down quickly, but their stems and rootsystems may become tough and fibrous and cancontribute to humus accumulation.

Cover Crops Help “Glue” SoilAs soil microorganisms digest plant material, theyproduce some compounds in addition to theactive and stable fractions of the organic matter.One group of these by-products is known aspolysaccharides.These are complex sugars thatact as glues in the soil to cement small soil parti-cles into clusters or aggregates. Many farmers


use the term “crumb” to describe soil clustersabout the size of a grain of rice.A well-aggregatedor “crumby” soil—not to be confused with crum-my or depleted soil—has good aeration. It allowsbetter infiltration and retention of water.

Cover crops can promote good aggregation inthe soil through increased production of theseand other microbial glues. See Cover Crops CanStabilize Your Soil (p. 19). Well-aggregated soilsalso are less prone to compaction, which hasbeen shown to reduce yields of vegetables suchas snap beans, cabbage and cucumber by 50 per-cent or more (451).

As they decompose, leguminous cover cropsseem to be better than grasses for production ofpolysaccharides (9). However, polysaccharideswill decompose in a matter of months, so theiraggregation effect is likely to last only the seasonafter the use of the cover crop.

Grass species also promote good aggregation,but by a different mechanism. Grasses have a‘fibrous’ root system—made of numerous fineroots spreading out from the base of the plant.These roots may release compounds that helpaggregate the soil between roots.

Organic matter builds up very slowly in thesoil. A soil with 3 percent organic matter mightonly increase to 4 percent after a decade or moreof soil building.The benefits of increased organicmatter, however, are likely to be apparent longbefore increased quantities are detectable. Some,such as enhanced aggregation, water infiltrationrates and nutrient release, will be apparent thefirst season; others may take several years tobecome noticeable (429).

Your tillage method is an important considera-tion when using cover crops to build soil,becausetillage will affect the rate of organic matter accu-mulation. It is difficult to build up organic mat-ter under conventional tillage regimes. Tillagespeeds up organic matter decomposition byexposing more surface area to oxygen, warmingand drying the soil, and breaking residue intosmaller pieces with more surfaces that can beattacked by decomposers. Like fanning a fire,tillage rapidly “burns up” or “oxidizes” the fuel,which in this case is organic matter.The resultingloss of organic matter causes the breakdown of

soil aggregates and the poor soil structure oftenseen in overtilled soil.

When adding cover crops to a system, mini-mize tillage to maximize the long-term soil bene-fits. Many of the cover crops discussed in thisbook are ones you can seed into growing crops orno-till plant into crop residues. Otherwise, thegain in organic matter may be counteracted byhigher decomposition rates.

TIGHTENING THE NUTRIENT LOOP

In addition to reducing topsoil erosion andimproving soil structure, cover crops enhancenutrient cycling in your farming system by takingup nutrients that otherwise might leach out of thesoil profile. These excess nutrients have thepotential to pollute groundwater or local streamsand ponds,not to mention impoverishing the soilthey came from.

Of the common plant nutrients,nitrogen in thenitrate form is the most water-soluble and there-fore the most vulnerable to leaching. Anytimesoil is bare and appreciable rain falls, nitrates areon the move.Nitrate can be present in the soil atthe end of a cropping season if the crop did notuse all the N applied. Decomposing organic mat-ter (including plant residues, compost and animalmanures) also can supply nitrate-N, as long as thesoil temperature is above freezing. Even in a fieldwhere the yearly application of N is well-suited tocrop needs, nitrates can accumulate after cropsare harvested and leach when it rains.

Cover crops reduce nitrate leaching in twoways. They soak up available nitrate for theirown needs. They also use some soil moisture,reducing the amount of water available to leachnutrients.

The best cover crops to use for nitrate conser-vation are nonlegumes that form deep, extensiveroot systems quickly after cash crops are harvest-ed. For much of the continental U.S., cereal rye isthe best choice for catching nutrients after a sum-mer crop.Its cold tolerance is a big advantage thatallows rye to continue to grow in late fall and putdown roots to a depth of three feet or more.Where winters are mild,rye can grow through thewinter months.


Research with soil high in residual N in themid-Atlantic’s coastal plain showed that cereal ryetook up more than 70 lb. N/A in fall when plant-ed by October 1. Other grasses, including wheat,oats, barley and ryegrass, were only able to takeup about half that amount in fall. Legumes werepractically useless for this purpose in theChesapeake Bay study (46). Legumes tend toestablish slowly in fall and are mediocre N scav-engers, as they can fix much of their own N.

To maximize N uptake and prevent leaching,plant nonlegumes as early as possible. In theabove study, rye took up only 15 lb. N/A whenplanting was delayed until November. It is impor-tant to give cover crops the same respect as anyother crop in the rotation and plant them in atimely manner.

Not Just Nitrogen CyclingCover crops help bring other nutrients back intothe upper soil profile from deep soil layers.Calcium and potassium are two macronutrientswith a tendency to travel with water, though not

Cover Crops Can Stabilize Your SoilThe more you use cover crops, the betteryour soil tilth, research continues to show.One reason is that cover crops, especiallylegumes, encourage populations of beneficialfungi and other microorganisms that helpbind soil aggregates.

The fungi, called mycorrhizae, produce awater-insoluble protein known as glomalin,which catches and glues together particles oforganic matter, plant cells, bacteria and otherfungi (453).Glomalin may be one of the mostimportant substances in promoting andstabilizing soil aggregates.

Most plant roots, not just those of covercrops, develop beneficial mycorrhizalrelationships.The fungi send out rootlikeextensions called hyphae,which take upwater and soil nutrients to help feed plants. Inlow-phosphorus soils, for example, thehyphae can increase the amount of

phosphorus that plants obtain. In return, thefungi receive energy in the form of sugarsthat plants produce in their leaves and senddown to the roots.

Growing a cover crop increases theabundance of mycorrhizal spores. Legumes inparticular can contribute to mycorrhizaldiversity and abundance, because their rootstend to develop large populations of thesebeneficial fungi.

By having their own mycorrhizal fungi andby promoting mycorrhizal relationships insubsequent crops, cover crops therefore canplay a key role in improving soil tilth.Theoverall increase in glomalin production alsocould help explain why cover crops canimprove water infiltration into soil andenhance storage of water and soil nutrients,even when there has been no detectableincrease in the amount of soil organic matter.

generally on the express route with N. Thesenutrients can be brought up from deeper soil lay-ers by any deep-rooted cover crop.The nutrientsare then released back into the active organicmatter when the cover crop dies and decomposes.

Although phosphorus (P) doesn’t generallyleach, as it is only slightly water-soluble, covercrops may play a role in increasing its availabilityin the soil. Some covers, such as buckwheat andlupins, are thought to secrete acids into the soilthat put P into a more soluble, plant-usable form.

Some cover crops enhance P availability inanother manner. The roots of many commoncover crops, particularly legumes, house benefi-cial fungi known as mycorrhizae. The mycor-rhizal fungi have evolved efficient means ofabsorbing P from the soil, which they pass on totheir plant host.The filaments (hyphae) of thesefungi effectively extend the root system and helpthe plants tap more soil P.

Keeping phosphorus in an organic form is themost efficient way to keep it cycling in the soil.Sothe return of any plant or animal residue to the


soil helps maintain P availability. Cover crops alsohelp retain P in your fields by reducing erosion.

Adding NitrogenOne of nature’s most gracious gifts to plants andsoil is the way that legumes,with the help of rhi-zobial bacteria, can add N to enrich your soil. Ifyou are not familiar with how this remarkableprocess works, see Nodulation:Match Inoculantto Maximize N (p. 122).

The nitrogen provided by N-fixation is usedefficiently in natural ecosystems, thanks to thesoil’s complex web of interacting physical, chem-ical and biological processes. In an agriculturalsystem, however, soil and crop management fac-tors often interfere with nature’s ultra-efficientuse of organic or inorganic N.Learning a bit aboutthe factors affecting N-use efficiency from legumeplants will help build the most sustainable crop-ping system possible within your constraints.

How Much N is Fixed?A number of factors determine how much of theN in your legume came from “free”N, fixed fromN2 gas:

• Is the symbiosis (the interdependence ofthe rhizobia and the plant roots) effective? SeeNodulation: Match Inoculant to Maximize N(p. 122). Use the correct rhizobial inoculant forthe legume you’re growing. Make sure it’s fresh,was stored properly, and that you apply it with aneffective sticking agent. Otherwise, there will befew nodules and N-fixation will be low.

• Is the soil fertile? N-fixation requiresmolybdenum, iron, potassium, sulfur and zinc tofunction properly. Soils depleted of these micro-nutrients will not support efficient fixation.Tissuetesting your cash crops can help you decide if youneed to adjust micronutrient levels.

• Is the soil getting enough air? N-fixationrequires that N-rich air get to the legume roots.Waterlogging or compaction hampers the move-ment of air into the soil.Deep-rooted cover cropscan help alleviate subsoil compaction (451).

• Is the pH adequate? Rhizobia generally willnot live long in soils below pH 5.

• Does the legume/rhizobial pair have high fix-ation potential? Not all legumes were created

equal—some are genetically challenged when itcomes to fixation. Beans (Phaseolus spp.) arenotoriously incapable of a good symbiotic rela-tionship and are rarely able to fix much more than40 lb. N/A in a whole season. Cowpeas (Vignaunguiculata) and vetches (Vicia spp.), on theother hand, are generally capable of high fixationrates. Check Chart 2 Performances and Roles(p.67) and the sections on individual cover cropsfor information about their N-fixation potential.

Even under the best of conditions, legumesrarely fix more than 80 percent of the nitrogenthey need to grow,and may only fix as much as 40or 50 percent. The legume removes the rest ofwhat it needs from the soil like any other plant.Legumes have to feed the bacteria to get them towork, so if there is ample nitrate already availablein the soil,a legume will remove much of that firstbefore expending the energy to get N-fixationgoing. In soils with high N fertility, legumes mayfix little or no nitrogen. See How Much N?(p. 22).

While it is tempting to think of legume nodules aslittle fertilizer factories pumping N into the sur-rounding soil, that isn’t what happens.The fixedN is almost immediately shunted up into thestems and leaves of the growing legume to formproteins, chlorophyll and other N-containingcompounds.The fixed nitrogen will not becomeavailable to the next crop until the legumedecomposes. Consequently, if the abovegroundpart of the legume is removed for hay, the majori-ty of the fixed nitrogen also leaves the field.

What about the legume roots? Under condi-tions favoring optimal N fixation, a good rule ofthumb is to think of the nitrogen left in the plantroots (15 to 30 percent of plant N) as beingroughly equivalent to the amount the legumeremoved directly from the soil, and the amount inthe stems and leaves as being equivalent to whatwas fixed.

Annual legumes that are allowed to flower andmature will transport a large portion of their bio-mass nitrogen into the seeds or beans.Also, oncethe legume has stopped actively growing, it willshut down the N-fixing symbiosis. In annuallegumes this occurs at the time of flowering; no


additional N gain will occur after that point.Unlessyou want a legume to reseed itself, it’s generally agood idea to kill a legume cover crop in the early-to mid-blossom stage. You’ll have obtained maxi-mum legume N and need not delay planting of thefollowing cash crop any further, aside from anyperiod you may want for residue decomposition aspart of your seedbed preparation.

How Nitrogen is ReleasedHow much N will soil really acquire from alegume cover crop? Let’s take it from the point ofa freshly killed, annual legume, cut down in itsprime at mid-bloom.The management and climat-ic events following the death of that legume willgreatly affect the amount and timing of N releasefrom the legume to the soil.

Most soil bacteria will feast on and rapidlydecompose green manures such as annuallegumes, which contain many simple sugars andproteins as energy sources. Soil bacteria love toparty and when there is lots to eat, they do some-thing that no party guest you’ve ever invited cando—they reproduce themselves, rapidly andrepeatedly,doubling their population in as little asseven days under field conditions (306). Even arelatively inactive soil can come to life quicklywith addition of a delectable green manure.

The result can be a very rapid and large releaseof nitrate into the soil within a week of the greenmanure’s demise. This N release is more rapidwhen covers are plowed down than when left onthe surface. As much as 140 lb. N/A has beenmeasured 7 to 10 days after plowdown of hairyvetch (363). Green manures that are less protein-rich (N-rich) will take longer to release N.Thosethat are old and fibrous or woody are generallyleft for hard-working but somewhat sluggish fungito convert slowly to humus over the years, gradu-ally releasing small amounts of nutrients.

Other factors contribute significantly to howquickly a green manure releases its N.Weather has ahuge influence.The soil organisms responsible fordecomposition work best at warm temperaturesand are less energetic during cool spring months.

Soil moisture also has a dramatic effect.Research shows that soil microbial activity peakswhen 60 percent of the soil pores are filled with

water, and declines significantly when moisturelevels are higher or lower (244).This 60 percentwater-filled pore space roughly corresponds tofield capacity, or the amount of water left in thesoil when it is allowed to drain for 24 hours aftera good soaking rain.

Microbes are sensitive to soil chemistry as well.Most soil bacteria need a pH of between 6 and 8to perform at peak; fungi (the slow decomposers)are still active at very low pH.Soil microorganismsalso need most of the same nutrients that plantsrequire, so low-fertility soils support smaller pop-ulations of primary decomposers, compared withhigh-fertility soils. Don’t expect N-release rates orfertilizer replacement values for a given covercrop to be identical in fields of different fertility.

Many of these environmental factors are out ofyour direct control in the near term.Managementfactors such as fertilization, liming and tillage,however, also influence production and availabili-ty of legume N.

Tillage, No-Tillage and N-CyclingTillage affects decomposition of plant residues ina number of ways. First, any tillage increases soilcontact with residues and increases the microbes’access to them. The plow layer is a hospitableenvironment for microbes, as they’re shelteredfrom extremes of temperature and moisture.Second, tillage breaks the residue into smallerpieces, providing more edges for microbes tomunch.Third, tillage will temporarily decrease thedensity of the soil, generally allowing it to drainand therefore warm up more quickly. All told,residues incorporated into the soil tend to decom-pose and release nutrients much faster than thoseleft on the surface, as in a no-till system.That’s notnecessarily good news, however.

A real challenge of farming efficiently is to keepas much of the N as possible in a stable, storableform until it’s needed by the crop. The beststorage form of N is the organic form: the unde-composed residue, the humus or the microorgan-isms themselves.

Let’s consider the N contained in the microbes.Nitrogen is a nutrient the microbes need for build-ing proteins and other compounds. Carbon-con-taining compounds such as sugars are mainly


How Much N?To find out if you might need more N thanyour green manure will supply, you need toestimate the amount of N in your cover crop.To do this, assess the total yield of the greenmanure and the percentage of N in the plantsjust before they die.

To estimate yield, take cuttings from severalareas in the field, dry and weigh them.Use ayardstick or metal frame of known dimensions(1 ft. x 2 ft.,which equals 2 ft2 works well)and clip the plants at ground level within theknown area.Dry them out in the sun for a fewconsecutive days, or use an oven at about140° F for 24 to 48 hours until they are“crunchy dry.”Use the following equationto determine per-acre yield of dry matter:Yield (lb.)/Acre = Total weight of dried samples (lb.)

X43,560 sq. ft.

# square feet you sampled 1 Acre

While actually sampling is more accurate,you can estimate your yield from the height ofyour green manure crop and its percentgroundcover.Use these estimators:

At 100 percent groundcover and 6-inchheight*,most nonwoody legumes will containroughly 2,000 lb./A of dry matter. For eachadditional inch, add 150 lb. So, a legume that is18 inches tall and 100 percent groundcoverwill weigh roughly:

Inches >6: 18 in.–6 in. = 12 in.

x 150 lb./in.: 12 in. x 150 lb./in. = 1,800 lb.

Add 2,000 lb.: 2,000 lb. + 1,800 lb. = 3,800 lb.

If the stand has less than 100 percentgroundcover,multiply by (the percent groundcover / 100). In this example, for 60 percentgroundcover, you would obtain:3,800 x (60/100) = 2,280 lb.

Keep in mind that these are roughestimates to give you a quick guide for theproductivity of your green manure.To knowthe exact percent N in your plant tissue, youwould have to send it to a lab for analysis.Even with a delay for processing, the resultscould be helpful for the crop if you use splitapplications of N.Testing is always a good idea,as it can help you refine your N estimates forsubsequent growing seasons.

The following rules of thumb may help here:• Annual legumes typically have between

3.5 and 4 percent N in their abovegroundparts prior to flowering (for young material,use the higher end of the range), and 3 to 3.5percent at flowering.After flowering,N in theleaves decreases quickly as it accumulates inthe growing seeds.

energy sources,which the microorganisms use asfuel to live.The process of burning this fuel sendsmost of the carbon back into the atmosphere ascarbon dioxide, or CO2.

Suppose a lot of new food is suddenly put intothe soil system, as when a green manure isplowed down. Bacteria will expand their popula-tions quickly to tap the carbon-based energythat’s available.All the new bacteria, though, willneed some N, as well as other nutrients, for bodybuilding before they can even begin to eat.So anynewly released or existing mineral N in soil getsscavenged by new bacteria.

Materials with a high carbon to nitrogen (C:N)ratio, such as mature grass cover crops, straw orany fibrous,woody residue,have a low N content.They can“tie up” soil N, keeping it immobilized(and unavailable) to crops until the carbon “fuelsupply” starts depleting.Tie-up may last for sever-al weeks in the early part of the growing season,and crop plants may show the yellowing charac-teristic of N deficiencies. That is why it oftenmakes sense to wait one to three weeks afterkilling a low-N cover before planting the nextcrop, or to supplement with a more readily avail-able N source when a delay is not practical.

* For cereal rye, the height relationship is a bit different. Cereal ryeweighs approximately 2,000 lb./A of dry matter at an 8-inch heightand 100 percent groundcover. For each additional inch, add 150lb., as before, and multiply by (percent groundcover/100). For mostsmall grains and other annual grasses, start with 2,000 lb./A at 6inches and 100 percent ground cover.Add 300 lb. for eachadditional inch and multiply by (percent groundcover/100).


• For perennial legumes that have asignificant number of thick, fibrous or woodystems, reduce these estimates by 1 percent.

• Most cover crop grasses contain 2 to 3percent N before flowering and 1.5 to 2.5percent after flowering.

• Other covers, such as brassicas andbuckwheat,will generally be similar to, orslightly below, grasses in their N content.Toput it all together:Total N in green manure (lb./A) = yield (lb./A) x % N

100

To estimate what will be available to yourcrop this year, divide this quantity of N by:• 2, if the green manure will be conventionally

tilled;• 4, if it will be left on the surface in a no-till

system in Northern climates;• 2, if it will be left on the surface in a no-till

system in Southern climates.

Bear in mind that in cold climates,N willmineralize more slowly than in warm climates,as discussed above. So these are grossestimates and a bit on the conservative side.

Of course, cover crops will not be the onlyN sources for your crops.Your soil will releasebetween 10 and 40 lb.N/A for each 1 percentorganic matter. Cold,wet clays will be at thelow end of the scale and warm,well-drainedsoils will be at the high end.You also mayreceive benefits from last year’s manure, greenmanure or compost application.

Other tools could help you refine yournitrogen needs.On-farm test strips of covercrops receiving different N rates would be anexample. Refer to Appendix A,Testing CoverCrops onYour Farm (p. 189) for some tips ondesigning an on-farm trial. In some regions, apre-sidedress N test in spring could help youestimate if supplemental N will be cost-effective. Bear in mind that pre-sidedresstesting does not work well when fresh plantresidues have been turned in—too muchmicrobial interference relating to N tie-up maygive misleading results.

For more information on determining yourN from green manures and other amendments,see the Northeast Cover Crop Handbook(361).—Marianne Sarrantonio, Ph.D.

Annual legumes have low C:N ratios, such as10:1 or 15:1.When pure stands of annual legumesare plowed down, the N tie-up may be so briefyou will never know it occurred.

Mixed materials, such as legume-grass mixtures,may cause a short tie-up, depending on the C:Nratio of the mixture. Some N storage in the micro-bial population may be advantageous in keepingexcess N tied up when no crop roots are there toabsorb it.

Fall-planted mixtures are more effective inmopping up excess soil N than pure legumes and,as stated earlier, the N is mineralized more rapidlyfrom mixtures than from pure grass.A fall-seededmixture will adjust to residual soil N levels.Whenthe N levels are high, the grass will dominate andwhen N levels are low, the legume will dominate

the mixtures. This can be an effective manage-ment tool to reduce leaching while making the Nmore available to the next crop.

Potential LossesA common misunderstanding about using greenmanure crops is that the N is used more efficient-ly because it’s from a plant source.This is not nec-essarily true. Nitrogen can be lost from a greenmanure system almost as easily as from chemicalfertilizers,and in comparable amounts.The reasonis that the legume organic N may be converted toammonium (NH4), then to ammonia (NH3) ornitrate (NO3) before plants can take it up. Underno-till systems where killed cover crops remainon the surface, some ammonia (NH3) gas can belost right back into the atmosphere.


Nitrate is the form of N that most plants prefer.Unfortunately, it is also the most water-solubleform of N.Whenever there is more nitrate thanplant roots can absorb, the excess may leach withheavy rain or irrigation water.

As noted earlier, nitrates in excess of 140 lb./Amay be released into warm,moist soil within as littleas seven to 10 days after plowing down a high-Nlegume, such as a hairy vetch stand. Since the fol-lowing crop is unlikely to have much of a root sys-tem at that point, the N has a ticket for Leachville.Consider also that the green manure may have beenplowed down to as deep as 12 inches—much deep-er than anyone would consider applying chemicalfertilizer. Moreover, green manures sometimes con-tinue to decompose after the cash crop no longerneeds N.This N also is prone to leaching.

To summarize, conventional plowing and aggres-sive disking can cause a rapid decomposition ofgreen manures, which could provide too much Ntoo soon in the cropping season.No-till systems willhave a reduced and more gradual release of N,but some of that N may be vulnerable to gaseousloss, either by ammonia volatilization or by deni-trification, which occurs when NO3- converts togases under low O2 (flooded) conditions. Thus,depending on management, soil and weather situa-tions, N from legume cover crops may not be moreefficiently used than N from fertilizer.

Some possible solutions to this cover cropnitrogen-cycling dilemma:

•A shallow incorporation of the green manure,as with a disk,may reduce the risk of gaseous loss.

• It may be feasible to no-till plant or transplantinto the green manure, then mow or incorporateit between the rows 10-14 days later, when cashcrop roots are more developed and able to takeup N. This has some risk, especially when soilmoisture is limiting, but can provide satisfactoryresults if seedling survival is assured.

• Residue from a grass/legume mix will have ahigher C:N than the legume alone, slowing therelease of N so it’s not as vulnerable to loss.

Consider also that some portion of the N in thegreen manure will be conserved in the soil in an

organic form for gradual release in a number ofsubsequent growing seasons.

OTHER SOIL-IMPROVING BENEFITS

Cover crops can be very useful as living plows topenetrate and break up compacted layers in thesoil. Some of the covers discussed in this book,such as sweetclover and forage radish,have rootsthat reach as deep as three feet in the soil with-in one cropping season.The action of numerouspointy little taproots with the hydraulic force ofa determined plant behind them can penetratesoil where plowshares fear to go. Grasses, withtheir tremendously extensive root systems, mayrelieve compacted surface soil layers. Sorghum-sudangrass can be managed to powerfully frac-ture subsoil. See Summer Covers RelieveCompaction (p. 110).

One of the less appreciated soil benefits ofcover crops is an increase in the total numbersand diversity of soil organisms.As discussed ear-lier, diversity is the key to a healthy, well-func-tioning soil. Living covers help supplyyear-round food for organisms that feed off rootby-products or that need the habitat provided ona residue-littered soil surface. Dead covers sup-ply a more varied and increased soil diet formany organisms.

Of course, unwanted pests may be lured to thefield. Effective crop rotations that include covercrops, however, tend to reduce rather thanincrease pest concerns. Pest-management consid-erations due to the presence of a cover crop arediscussed in the next chapter, Managing Pestswith Cover Crops (p. 25).

Finally, cover crops may have an added advan-tage of drying out and therefore warming soilsduring a cold, wet season.The flip side of this isthat they may dry the soil out too much and robthe following crop of needed moisture.

There are no over-the-counter elixirs for renew-ing soil. A long-term farm plan that includes covercrops,however,can help ensure your soil’s healthand productivity for as long as you farm.

MANAGING PESTS WITH COVER CROPS 25

MANAGING PESTS WITH COVER CROPSBy Sharad C.Phatak and Juan Carlos Diaz-Perez

Cover crops are poised to play increasinglyimportant roles on North American farms.In addition to slowing erosion, improving

soil structure and providing fertility,we are learn-ing how cover crops help farmers to managepests (390).With limited tillage and careful atten-tion to cultivar choice, placement and timing,cover crops can reduce infestations by insects,diseases, nematodes and weeds. Pest-fightingcover crop systems help minimize reliance onpesticides, and as a result cut costs, reduce yourchemical exposure, protect the environment, andincrease consumer confidence in the food youproduce.

Farmers and researchers are using cover cropsto design new strategies that preserve a farm’snatural resources while remaining profitable. Keyto this approach is to see a farm as an “agro-ecosystem”—a dynamic relationship of the min-eral, biological, weather and human resourcesinvolved in producing crops or livestock. Ourgoal is to learn agricultural practices that areenvironmentally sound,economically feasible andsocially acceptable.

Environmentally sustainable pest managementstarts with building healthy soils. Research insouth Georgia (see Georgia Cotton, PeanutFarmers, p. 26) shows that crops grown on bio-logically active soils resist pest pressures betterthan those grown on soils of low fertility,extremepH, low biological activity and poor soil structure.

There are many ways to increase biologicalactivity in soil. Adding more organic material bygrowing cover crops or by applying manure orcompost helps. Reducing or eliminating pesti-cides favors diverse, healthy populations of bene-ficial soil flora and fauna. So does reducing oreliminating tillage that causes losses of soil struc-ture, biological life or organic matter.These lossesmake crops more vulnerable to pest damage.

Farming on newly cleared land shows theprocess well. Land that has been in a“cover crop”

of trees or pastures for at least 10 years remainsproductive for row crops and vegetables for thefirst two to three years. High yields of agronomicand horticultural crops are profitable, with com-paratively few pesticide and fertilizer inputs.After that period—under conventional systemswith customary clean tillage—annual cropsrequire higher inputs. The first several years ofexcessive tillage destroys the food sources andmicro-niches on which the soil organisms thathelp suppress pests depend.When protective nat-ural biological systems are disrupted, pests havenew openings and crops are much more at risk.

Cover crop farming is different from clean-fieldmonocropping,where perfection is rows of cornor cotton with no thought given to encouragingbiological diversity.Cover crops bring more formsof life into the picture and into your managementplan. By working with a more diverse range ofcrops,some growing at the same time in the samefield,you’ve got a lot more options.Here’s a quickoverview of how these systems work.

Insect ManagementIn balanced ecosystems, insect pests are kept incheck by their natural enemies (409).These nat-ural pest control organisms —called beneficials inagricultural systems—include predator and para-sitoid insects and diseases. Predators kill and eatother insects; parasitoids spend their larval stageinside another insect, which then dies as theinvader’s larval stage ends. However, in conven-tional agricultural systems, synthetic chemicaltreatments that kill insect pests also typically killthe natural enemies of the insects. Conservingand encouraging beneficial organisms is a key toachieving sustainable pest management.

You should aim to combine strategies thatmake each farm field more hospitable to benefi-cials. Reduce pesticide use, and, when use isessential, select materials that are least harmful tobeneficials. Avoid or minimize cultural practices


TIFTON,Ga.—Here in southwestern Georgia,I’mworking with farmers who have had dramaticsuccess creating biologically active soil in fieldsthat have been conventionally tilled for genera-tions. We still grow the traditional cash crops ofcotton and peanuts, but with a difference.We’veadded cover crops,virtually eliminated tillage,andadded new cash crops that substitute for cottonand peanuts some years to break disease cyclesand allow for more biodiversity.

Our strategies include no-till planting (usingmodified conventional planters), permanentplanting beds, controlled implement traffic,crop rotation and annual high-residue wintercover crops.We incorporate fertilizer and limeprior to the first planting of rye in the conver-sion year.This is usually the last tillage we planto do on these fields for many years.Together,these practices give us significant pest manage-ment benefits within three years.

Growers are experimenting with a basic win-ter cover crop>summer cash crop rotation.Ourcover crops are ones we know grow well here.Rye provides control of disease, weed andnematode threats. Legume crops are crimsonclover, subterranean clover or cahaba vetch.They are planted with the rye or along field bor-ders, around ponds, near irrigation lines and inother non-cropped areas as close as possible tofields to provide the food needed to supportbeneficials at higher populations.

When I work with area cotton and peanutgrowers who want to diversify their farms, weset up a program that looks like this:

• Year 1. Fall—Adjust fertility and pHaccording to soil test. Deep till if necessary torelieve subsurface soil compaction. Plant acover crop of rye, crimson clover, cahaba vetchor subterranean clover.

Georgia Cotton, Peanut Farmers Use Cover Crops to Control PestsSpring—Strip-till rows 18 to 24 inches wide,

leaving the cover crop growing between thestrips.Three weeks later, plant cotton.

• Year 2. Fall—Replant cereal rye or cahabavetch, allow crimson or subclover hard seed togerminate.Spring—Strip-till cotton.• Year 3. Fall—Plant rye.Spring—Desiccate rye with herbicides.

No-till plant peanuts.• Year 4.The cycle starts again at year 1.

Vegetable farmers frequently use fall-plantedcereal rye plowed down before vegetables, orcrimson clover strip-tilled before planting veg-etables.The crimson clover matures,drops hardseed, then dies. Most of the seed germinates inthe fall. Cereal/legume mixes have not beenmore successful than single-crop cover cropplantings in our area.

Some vegetable farmers strip-till rows intorye in April.The strips are planted in early Mayto Southern peas, lima beans or snap beans.Ryein row middles will be dead or nearly dead.Ryeor crimson clover can continue the rotation.

Vegetable farmers also broadcast crimsonclover in early March.They desiccate the cover,strip-till rows, then plant squash in April. Theclover in the row middles will set seed then dieback through summer.The crimson strips willbegin to regrow in the fall from the droppedseed, and fall vegetables may be planted in thetilled areas after the July squash harvest.

Insecticide and herbicide reduction beginsthe first year, with no applications needed bythe third or fourth year in many cases.

The farmers get weed control by flail mow-ing herbicide-killed, fall-planted rye, leavingabout 6 inches of stubble. Alternatively, they

such as tilling and burning that kill beneficials anddestroy their habitat.Build up the sustenance andhabitat that beneficials need.Properlymanagedcovercrops supply moisture, physical niches and food inthe form of insects,pollen,honeydew and nectar.

By including cover crops in your rotations andnot spraying insecticides, beneficials often arealready in place when you plant spring or sum-mer crops.However,if you fully incorporate covercrops into the soil, you destroy or disperse most


of the beneficials that were present.Conservationtillage is a better option because it leaves more ofthe cover crop residue on the surface. No-tillplanting only disturbs an area 2 to 4 inches wide,while strip-tilling disturbs an area up to about 24inches wide between undisturbed row middles.

Cover crops left on the surface may be living,temporarily suppressed, dying or dead. In anyevent, their presence protects beneficials andtheir habitat. The farmer-helpful organisms arehungry, ready to eat the pests of cash crops thatare planted into the cover-crop residue.The ulti-

could use a roller to kill the rye crop. One ortwo post-emerge herbicide applications shouldsuffice in the first few years. I don’t recom-mend cultivation for weed control because itincreases risks of soil erosion and damages theprotective outer leaf surface layer (cuticle) thathelps prevent plant diseases.

We see changes on farms where the rota-tions stay in place for three or more years:

• Insects. Insecticide costs under con-servation tillage are $50 to $100/A lessthan conventional crop management in thearea for all kinds of crops. The farmers usingthe alternative system often substitute withinsect control materials such as Bacillusthuringiensis (Bt), pyrethroids, and insectgrowth regulators that have less severe envi-ronmental impact than chemical pesticides.These products are less persistent in the fieldenvironment, more targeted to specific pestsand do less harm to beneficials. By plantingcover crops on field edges and in othernon-crop areas, these farmers are increasingthe numbers of beneficials in the fieldenvironments.

Pests that are no longer a problem on thecover-cropped farms include thrips, bollworm,budworm, aphids, fall armyworm, beet army-worm and white flies. On my no-till researchplots with cover crops and long rotations, I’venot used insecticides for six years on peanuts,for eight years on cotton and for 12 years onvegetables. I’m working with growers who usecover crops and crop rotations to economic-ally produce cucumbers, squash, peppers, egg-plant, cabbage, peanuts, soybeans and cottonwith only one or two applications of insecti-cide—sometimes with none.

• Weeds. Strip-tilling into over-winteredcover crops provides acceptable weed controlfor relay-cropped cucumbers (325). Convent-ional management of rye in our area is usuallyto disk or kill it with broad-spectrum herbi-cides such as paraquat or glyphosate. Rye canalso be killed with a roller,providing an accept-able level of weed control for the subsequentcash crop.

• Diseases. I’ve been strip-tilling crimsonclover since 1985 to raise tomatoes, peppers,eggplant, cucumbers, cantaloupes, lima beans,snap beans, Southern peas and cabbages. I’musing no fungicides. Our research staff hasraised peanuts no-tilled into cereal rye for thepast six years, also without fungicides.

• Nematodes. If we start on land where pestnematodes are not a major problem,this systemkeeps them from becoming a limiting factor.

Even though the conventional wisdom saysyou can’t build organic matter in our climateand soils, we have top-inch readings of 4 per-cent organic matter in a field that tested 0.5percent four years ago.

We are still learning, but know that we canrotate crops, use cover crops and cut tillage togreatly improve our sustainability. In our expe-rience, we’ve reduced total costs by as muchas $200 per acre for purchased inputs andtillage. Parts of our system will work in manyplaces. Experiment on a small scale to lookmore closely at what’s really going in your soiland on your crops. As you compare insightsand share information with other growers andresearchers in your area,you’ll find cover cropsthat help you control pests, too.—Sharad C.Phatak


mate goal is to provide year-round food and habi-tat for beneficials to ensure their presence withinor near primary crops.

We’re just beginning to understand the effectsof cropping sequences and cover crops on bene-ficial and insect pest populations. Researchershave found that generalist predators, whichfeed on many species, may be an important bio-logical control. During periods when pests arescarce or absent, several important generalistpredators can subsist on nectar, pollen and alter-native prey afforded by cover crops.This suggestsyou can enhance the biological control of pestsby using cover crops as habitat or food for thebeneficials in your area.

This strategy is important for farmers in theSouth, where pest pressure can be especiallyheavy. In south Georgia, research showed thatpopulations of beneficial insects such as insidiousflower bugs (Orius insidiosus), bigeyed bugs(Geocoris spp.) and various lady beetles(Coleoptera coccinellidae) can attain high densi-ties in various vetches, clovers and certain crucif-erous crops. These predators subsisted andreproduced on nectar, pollen, thrips and aphids,and were established before key pests arrived.Research throughout Georgia, Alabama andMississippi showed that when summer vegetableswere planted amid“dying mulches”of cool-seasoncover crops, some beneficial insects moved in toattack crop pests.

When crops are attacked by pests, they sendchemical signals that attract beneficial insects.Thebeneficials move in to find their prey (420).

Maximizing natural predator-pest interaction isthe primary goal of biologically based IntegratedPest Management (IPM),and cover crops can playa leading role. For example:

• Colorado potato beetles were observed at 9a.m. attacking eggplant that had been strip-tillplanted into crimson clover. By noon, assassinbugs had clustered around the feeding beetles.The beneficial bugs destroyed all the beetles byevening.

• Cucumber beetles seen attacking cucumberplants were similarly destroyed by beneficialswithin a day.

• Lady beetles in cover crop systems help tocontrol aphids attacking many crops.

Properly selected and managed, cover crops canenhance the soil and field environment to favorbeneficials. Success depends on properly manag-ing the cover crop species matched with the cashcrops and anticipated pest threats.While we don’tyet have prescription plantings guaranteed tobring in all the needed beneficials—and only ben-eficials—for long lists of cash crops, we knowsome associations:

• We identified 13 known beneficial insectsassociated with cover crops during one growingseason in south Georgia vegetable plantings (53,55, 57).

• In cotton fields in south Georgia whereresidues are left on the surface and insecticidesare not applied,more than 120 species of benefi-cial arthropods, spiders and ants have beenobserved.

• Fall-sown and spring-sown insectory mixeswith 10 to 20 different cover crops work wellunder orchard systems. These covers providehabitat and alternative food sources for beneficialinsects.This approach has been used successfullyby California almond and walnut growers partici-pating in the Biologically Intensive OrchardSystems (BIOS) project of the University ofCalifornia (184).

BUCKWHEAT grows quickly in cool, moist weather.


The level of ecological sustainability dependson the grower’s interests, management skills andsituation. Some use no insecticides while othershave substantially reduced insecticide applica-tions on peanut, cotton and vegetable crops.

• In Georgia, Mississippi and South Carolina,minimally tilled crimson clover or cahaba vetchbefore cotton planting have been successful inreducing fertilizer N up to 50 percent and insecti-cide inputs by 30 to 100 percent.

• Many farmers are adopting a system of trans-planting tomatoes, peppers and eggplant into akilled hairy vetch or vetch/rye cover crop.Benefits include weed, insect and disease sup-pression, improved fruit quality and overall lowerproduction cost.

• Leaving “remnant strips” of a cover whenmost of the crop is mowed or incorporated pro-vides a continuing refuge and food source for ben-eficials, which might otherwise leave the area ordie. This method is used in orchards when con-tinued growth of cover crops would cause mois-ture competition with trees.

• Insect movement is orchestrated in a systemdeveloped by Oklahoma State University forpecan growers.As legume mixtures senesce, ben-eficials migrate into trees to help suppress harm-ful insects.Not mowing the covers fromAugust 1until shuck split of the developing pecans lessensthe unwanted movement of stink bugs, a pestwhich can damage green pecans (261). InCalifornia, lygus bugs on berseem clover or alfalfaare pests of cash crops.Be careful that cover cropmaturity or killing a cover doesn’t force pests intoa neighboring cash crop.

Disease ManagementGrowers traditionally have been advised to turnunder plant debris by moldboard plowing to min-imize crop losses due to diseases (321, 322, 403,405,406).Now we realize that burying cover cropresidues and disrupting the entire soil profileeliminates beneficial insect habitats and the bene-fits of weed control by crop residues. Theincreased use of conservation tillage increases theneed to manage crop disease without buryingcover crops.

In the field, althoughplants are exposed to awide diversity of micro-organisms, plant infec-tion by microorganismsis rare (314). A patho-gen has to cross manyplant barriers before itcan cause disease toroots, stem or leaves.You can use covercrops to reinforce two of these barriers.Plant cuticle layer. This often waxy surface

layer is the first physical barrier to plant pene-tration. Many pathogens and all bacteria enterthe plant through breaks, such as wounds,or nat-ural openings, such as stomata, in this cuticlelayer. This protective layer can be physicallydamaged by cultivation, manipulation, sprayingand sand-blasting from wind erosion, as well asby the impact and soil splashing from raindropsand overhead irrigation. Spray adjuvants mayalso damage the waxes of the cuticle resulting inmore disease, as with Botritys cinerea rot ingrapes (356, 367). In well-developed minimum-till or no-till crop systems with cover crops, youmay not need cultivation for weed control (seebelow) and you can minimize spraying. Organicmulches form living, dying or killed covers thathold soil, stop soil splashing and protect cropsfrom injury to the cuticle.Plant surface microflora. Many benign

organisms are present on the leaf and stem sur-face. They compete with pathogens for a limitedsupply of nutrients. Some of these organisms pro-duce natural antibiotics.Epiphytic bacteria adhereto plant surfaces forming multicellular structuresknown as biofilms (339). These biofilms play animportant role in plant disease. Pesticides, soaps,surfactants, spreaders and sticking agents can killor disrupt these beneficial microorganisms,weak-ening the plant’s defenses against pathogens(356,367). Cover crops can help this natural pro-tection process work by reducing the need forapplication of synthetic crop protection materi-als. Further,cover crop plant surfaces can supporthealthy populations of beneficial microorgan-

Cover crops

can enhance

the soil and field

environment to

favor beneficial

insects.


Many crops can be managed as cover crops,butonly a few have been studied specifically fortheir pest-related benefits on cash crops andfield environments.

Learn all you can about the impacts of acover crop species to help you manage it inyour situation. Here are several widely usedcover crops described by their effects underconservation tillage in relation to insects,diseases, nematodes and weeds.

• Cereal Rye (Secale cereale)—This winterannual grain is perhaps the most versatile covercrop used in the continental United States.Properly managed under conservation tillage,rye has the ability to reduce soil-borne diseases,nematodes and weeds. Rye is a non-host plantfor root-knot nematodes and soil-borne dis-eases. It produces significant biomass thatsmothers weeds when it is left on the surfaceand also controls weeds allelopathicallythrough natural weed-suppressing compounds.

As it grows, rye provides habitat, but notfood, for beneficial insects. Thus, only a smallnumber of beneficial insects are found on rye.

Fall-planted rye works well in reducing soil-borne diseases, root-knot nematodes andbroadleaf weeds in all cash crops that follow,

including cotton, soybean and most vegetables.Rye will not control weedy grasses. Because itcan increase numbers of cut worms and wireworms in no-till planting conditions, rye is notthe most suitable cover where those worms area problem ahead of grass crops like corn, sweetcorn, sorghum or pearl millet.

• Wheat (Triticum aestivum)—A winterannual grain, wheat is widely adapted andworks much like rye in controlling diseases,nematodes and broadleaf weeds.Wheat is notas effective as rye in controlling weeds becauseit produces less biomass and has less allelo-pathic effect.

• Crimson Clover (Trifolium incarnatum)—Used as a self-reseeding winter annual legumethroughout the Southeast, fall-planted crimsonclover supports and increases soil-borne dis-eases, such as the pythium-rhizoctonia complex,and root-knot nematodes. It suppresses weedseffectively by forming a thick mulch. Crimsonclover supports high densities of beneficialinsects by providing food and habitat. Becausesome cultivars produce “hard seed” that resistsimmediate germination, crimson clover can bemanaged in late spring so that it reseeds in latesummer and fall.

isms, including types of yeasts that can migrateonto a cash crop after planting or transplanting.

Soilborne pathogenic fungi limit production ofvegetables and cotton in the southern U.S. (404,405, 406, 407). Rhizoctonia solani, Pythiummyriotylum, Pythium phanidermatum andPythium irregulare are the most virulent patho-genic fungi that cause damping-off on cucum-bers, snap beans, and other vegetables.Sclerotium rolfsii causes rot in all vegetables andin peanuts and cotton. Infected plants that do notdie may be stunted because of lesions caused byfungi on primary or secondary roots, hypocotylsand stems, and may have reduced yields of lowquality. But after two or three years in covercropped, no-till systems, damping-off is not a seri-

ous disease,as experience on south Georgia farmsand research plots shows. Increased soil organicmatter levels may help in reducing plant diseaseincidence and severity by enhancing natural dis-ease suppression (252, 424).

In soils with high levels of disease inoculum,however, it takes time to reduce population levelsof soil pathogens using only cover crops. Aftertests in Maine with oats, broccoli, white lupine(Lupinus albus) and field peas (Pisum sativum)researchers cautioned it may take three to fiveyears to effectively reduce stem lesion losses onpotatoes caused by R. solani (240).Yet there aresingle-season improvements, too. For example, inan Idaho study, Verticillium wilt of potato wasreduced by 24 to 29 percent following sudangrass

Select Covers that Balance Pests, Problems of Farm


• Subterranean Clover (Trifolium subter-raneum)—A self-reseeding annual legume, fall-planted subterranean clover carries the samerisks as crimson clover with soil-borne diseasesand nematodes. It suppresses weeds moreeffectively in the deep South,however, becauseof its thick and low growth habit. Subcloversupports a high level of beneficial insects.

• Cahaba White Vetch (Vica sativa X V.cordata)—This cool-season annual legume is ahybrid vetch that increases soilborne diseasesyet suppresses root-knot nematodes.It supportsbeneficial insects, yet attracts very high num-bers of the tarnished plant bug, a serious pest.

• Buckwheat (Fagopyrum esculentum)—Asummer annual non-legume, buckwheat is veryeffective in suppressing weeds when plantedthickly. It also supports high densities of benefi-cial insects. It is suitable for sequential plantingaround non-crop areas to provide food andhabitat for beneficial insects. It is very attractiveto honeybees.

A well-planned crop rotation maximizes bene-fits and compensates for the risks of covercrops and cash crops. Planting rye in a no-till

system substantially reduces root-knot nema-todes, soil-borne diseases and broadleaf weeds.By using clovers and vetches in your fields andadding beneficial habitat in non-cultivatedareas, you can increase populations of benefi-cial insects that help to keep insects pestsunder control. Mixed plantings of small grainsand legumes combine benefits of both whilereducing their shortcomings.

As pesticides of all types (fungicides, herbi-cides, nematicides and insecticides) arereduced, the field environment becomesincreasingly resilient in keeping pest outbreaksin check. Plantings to further increase benefi-cial habitat in non-cultivated areas can helpmaintain pollinating insects and pest predators,but should be monitored to avoid build-ups ofpotential pests. Researchers are only beginningto understand how to manage these “insectaryplantings.”Editor’s Note: Each cover crop listed here,

except for cahaba vetch, is included in thecharts (p. 62 and following) and is fullydescribed in its respective section. Check theTable of Contents (p. 4) for location.—Sharad C.Phatak

green manure. Yield of U.S. No.1 potatoesincreased by 24 to 38 percent compared withpotatoes following barley or fallow (394).

Nematode ManagementNematodes are minute roundworms that interactdirectly and indirectly with plants. Some speciesfeed on roots and weaker plants,and also introducedisease through feeding wounds. Most nematodesare not plant parasites, but feed on and interactwith many soil-borne microorganisms, includingfungi, bacteria and protozoa. Damage to the cropfrom plant-parasitic nematodes results in a break-down of plant tissue, such as lesions or yellowfoliage; retarded growth of cells, seen as stuntedgrowth or shoots;or excessive growth such as rootgalls,swollen root tips or unnatural root branching.

If the community of nematodes containsdiverse species, no single species will dominate.

This coexistence would be the case in theundisturbed field or woodland described above.

In conventional crop systems, pest nematodeshave abundant food and the soil environment isconducive to their growth.This can lead to rapidexpansion of plant parasitic species, plant diseaseand yield loss. Cropping systems that increase bio-logical diversity over time usually prevent the onsetof nematode problems. Reasons may include adynamic soil ecological balance and improved,healthier soil structure with higher organic matter(5, 245, 424). In Michigan, to limit nematodesbetween potato crops,some potato growers reportthat two years of radish improves potato produc-tion and lowers pest control costs (270,271).


Once a nematode species is established in afield, it is usually impossible to eliminate it. Somecovers can enhance a resident parasitic nematodepopulation if they are grown before or afteranother crop that hosts a plant-damaging nema-tode species.

If a nematode pest species is absent from thesoil, planting a susceptible cover crop will notgive rise to a problem,assuming the species is notintroduced on seed, transplants or machinery(357). Iowa farmer Dick Thompson reports thatresearchers analyzing his fields found no evidencethat hairy vetch, a host for soybean cyst nema-tode, caused any problem with the pest in hissoybeans.This may be due to his use of compostin strip-cropped fields with an oats/hairyvetch>corn>soybean rotation.

You can gradually reduce a field’s nematodepest population or limit nematode impact oncrops by using specific cover crops. Nematodecontrol tactics involving covers include:• Manipulating soil structure or soil humus• Rotating with non-host crops• Using crops with nematicidal effects, such as

brassicas

Cover crops may also improve overall plant vitali-ty to lessen the nematode impact on yield. But ifyou suspect nematode trouble, send a soil samplefor laboratory analysis to positively identify thenematode species.Then be sure any cover cropsyou try aren’t alternate hosts for that pest species.Area IPM specialists can help you.

Using brassicas and many grasses as covercrops can help you manage nematodes. Covercrops with documented nematicidal propertiesagainst at least one nematode species includesorghum-sudangrass hybrids (Sorghum bicolor XS. bicolor var. sudanese), marigold (Tagetes patu-la), hairy indigo (Indigofera hirsuta), showy cro-talaria (Crotolaria spectabilis), sunn hemp(Crotalaria juncea), velvetbean (Mucunadeeringiana),rapeseed (Brassica rapa),mustardsand radish (Raphanus satiuus).

You must match specific cover crop specieswith the particular nematode pest species, thenmanage it correctly. For example, cereal ryeresidue left on the surface or incorporated to a

depth of several inches suppressed Columbialance nematodes in North Carolina cotton fieldsbetter than if the cover was buried more deeplyby moldboard plowing. Associated greenhousetests in the study showed that incorporated ryewas effective against root-knot,reniform and stub-by root nematodes, as well (20).

Malt barley,corn,radishes and mustard sometimesworked aswell as the standard nematicide to controlsugar beet nematode in Wyoming sugar beets, a1994 study showed. Increased production morethan offset the cover crop cost, and lamb grazing ofthe brassicas increased profit without diminishingnematode suppression. The success is conditionalupon a limited nematode density. The cover croptreatment was effective only if there were fewerthan 10 eggs or juveniles per cubic centimeter ofsoil. A moderate sugar beet nematode level wasreduced 54 to 75percent in about 11weeks,increas-ing yield by nearly 4 tons per acre (231).

Weed ManagementCover crops are widely used as smother crops toshade and out-compete weeds (412). Cerealgrains establish quickly as they use up the mois-ture, fertility and light that weeds need to survive.Sorghum-sudangrass hybrids and buckwheat arewarm-season crops that suppress weeds throughthese physical means and by plant-produced nat-ural herbicides (allelopathy).

Cereal rye is an overwintering crop that sup-presses weeds both physically and chemically. Ifrye residue is left on the soil surface, it releasesallelochemicals that inhibit seedling growth ofmany annual small-seeded broadleaf weeds, suchas pigweed and lambsquarters. The response ofgrassy weeds to rye is more variable. Rye is amajor component in the killed organic mulchesused in no-till vegetable transplanting systems.

Killed cover crop mulches last longer if thestalks are left intact, providing weed control wellinto the season for summer vegetables. Twoimplements have been modified specifically toenhance weed suppression by cover crops. Theundercutter uses a wide blade to slice just underthe surface of raised beds, severing cover cropplants from their root mass. An attached rollingharrow increases effectiveness (95, 96, 97). A


Buffalo rolling stalk chopper does no directtillage, but aggressively bends and cuts crops atthe surface (303). Both tools work well on mostlegumes when they are in mid-bloom stage orbeyond.

Killed mulch of a cover crop mix of rye, hairyvetch, crimson clover and barley kept processingtomatoes nearly weed-free for six weeks in anOhio test. This length of time is significant,because other research has shown that tomatofields kept weed-free for 36 days yield as much asfields kept weed-free all season (97, 150). Theroller is another method used to terminate thecover crop (13). The roller flattens and crimpsthe cover crop, forming a flat mat of cover cropresidue that effectively control weeds.

Cover crops can also serve as a“living mulch”tomanage weeds in vegetable production. Covercrops are left to grow between rows of the cashcrop to suppress weeds by blocking light and out-competing weeds for nutrients and water. Theymay also provide organic matter, nitrogen (iflegumes) and other nutrients mined from under-neath the soil surface, beneficial insect habitat,erosion prevention, wind protection and a toughsod to support field traffic.

To avoid competition with the cash crop, livingmulches can be chemically or mechanically sup-pressed. In the Southeast, some cool-season covercrops such as crimson clover die out naturallyduring summer crop growth and do not competefor water or nutrients. However, cover crops thatregrow during spring and summer—such as sub-terranean clover, white clover and red clover—can compete strongly for water with spring-planted crops unless the covers are adequatelysuppressed.

In New York, growing cover crops overseededwithin three weeks of potato planting providedgood weed suppression, using 70 percent lessherbicide. Yield was the same as, or moderatelyreduced from, the standard herbicide controlplots in the two-year study. Hairy vetch, woolly-pod vetch, oats, barley, red clover and an oats/hairy vetch mix were suppressed as needed withfluazifop and metribuzin (341).

Cover crops often suppress weeds early, thenprevent erosion or supply fertility later in the

season. For example, shade-tolerant legumes suchas red clover or sweetclover that are planted withspring grains grow rapidly after grain harvest toprevent weeds from dominating fields in late sum-mer. Overseeding annual ryegrass or oats at soy-bean leaf yellowing provides a weed-suppressingcover crop before frost and a light mulch to sup-press winter annuals, as well.

Healthy soils grow healthy weeds as well ashealthy crops,making it difficult to manage weedsin conservation tillage without herbicides. Longterm strategies for weed management shouldinclude:• Reducing the weed seed bank• Preventing weeds from going to seed• Cleaning equipment before moving to differ-

ent fields and farms• Planting cover crops to help manage weeds in

conservation tillage

Cover crops can play a pest-suppressing role onvirtually any farm. As we find out more aboutthe pest management benefits of cover crop sys-tems, they will become even more attractive fromboth an economic and an environmental per-spective. Traditional research will identify somenew pieces of these biologically based systems.However, growers who understand how allthe elements of their farm fit together will bethe people who will really bring cover crops intothe prominence they deserve in sustainablefarming.

CRIMSON CLOVER, a winter annual legume, growsrapidly in spring to fix high levels of nitrogen.


Readers’ note: > indicates progression to anoth-er crop; / indicates a mixture of crops growingat the same time.

One of the biggest challenges of covercropping is to fit cover crops into yourcurrent rotations,or to develop new rota-

tions that take full advantage of their benefits.Thissection will explore some of the systems usedsuccessfully by farmers in different regions of theU.S.One might be easily adapted to fit your exist-ing crops, equipment and management. Otherexamples may point out ways that you can modi-fy your rotation to make the addition of covercrops more profitable and practical.

Whether you add cover crops to your existingrotations or totally revamp your farming system,you should devote as much planning and atten-tion to your cover crops as you do to your cashcrops. Failure to do so can lead to failure of thecover crop and cause problems in other parts ofyour system. Also remember that there is likelyno single cover crop that is right for your farm.

Before you start:• Review Benefits of Cover Crops (p. 7) andSelecting the Best Cover Crops forYour Farm(p. 9).

• Decide which benefits are most important toyou.

• Read the examples below, then consider howthese cover crop rotations might be adaptedto your particular conditions.

• Talk to your neighbors and the other “experts”in your area, including the contact people list-ed in Regional Experts (p. 202).

• Start small on an easily accessible plot thatyou will see often.

• Be an opportunist—and an optimist. If yourcropping plans for a field are disrupted byweather or other conditions outside of yourcontrol, this may be the ideal window forestablishing a cover crop.

• Consider using an early-maturing cash crop toallow for timely planting of the cover crop.

• Cover crops can be used for feed.Considerharvesting or grazing for forage or alternativelivestock such as sheep and goats.

The ideas in this book will help you see covercrop opportunities, no matter what your system.For more in-depth scientific analysis of covercrops in diverse cropping systems, see severalcomprehensive reviews listed in Appendix F (77,106, 362, 390).

COVER CROPS FOR CORN BELTGRAIN AND OILSEED PRODUCTION

In addition to providing winter cover and build-ing soil structure, nitrogen (N) management willprobably be a major factor in your cover cropdecisions for the corn>soybean rotation. A fall-planted grass or small grain will scavenge leftoverN from the previous corn or soybean crop.Legumes are much less efficient at scavenging N,but will add N to the system for the followingcrop. Legume/grass mixtures are quite good atboth.

Corn>Soybean SystemsKeep in mind that corn is a heavy N feeder, soy-beans benefit little, if at all, from cover crop N andthat you have a shorter time for spring cover cropgrowth before corn than before soybeans.

▼ Precaution. If you use herbicides, be sure tocheck labels for plant-back or rotation intervals toensure that your cover crop isn’t adversely affected.

Cover crop features: rye provides wintercover,scavenges N after corn,becomes a long-last-ing (6 to 12 week) residue to hold moisture andsuppress weeds for your soybeans; hairy vetchprovides spring ground cover, abundant N and amoderate-term (4 to 8 week) mulch for a no-tillcorn crop; field peas are similar to vetch, butresidue breaks down faster; red clover is alsosimilar, but produces slightly less N and has less

CROP ROTATION WITH COVER CROPS

CROP ROTATION WITH COVER CROPS 35

vigorous spring regrowth; berseem clovergrows quickly to provide several cuttings for high-N green manure.

Here are some options to consider adapting toyour system:

Corn>Rye>Soybeans>Hairy Vetch.In Zone 7 and warmer,you can grow a cover cropevery year between your corn and full-seasonbeans.Also, you can use wheat or another smallgrain to replace the cover crop before beans, in athree-crop, two-year rotation (corn>wheat>dou-blecrop beans). In all cases, another legume or agrass/legume mixture can be used instead of a sin-gle species cover crop.Where it is adapted, youcan use crimson clover or a crimson/grass mix-ture instead of vetch.

In cooler areas, plant rye as soon as possibleafter corn harvest. If you need more time in thefall, try overseeding in rowed beans at drydown“yellow leaf”stage in early fall, or in early summerat the last cultivation of corn. Seeding optionsinclude aerial application where the service iseconomical, using a specialty high-body tractorwith narrow tires,or attaching a broadcast seeder,air seeder or seed boxes to a cultivator.

▼Precaution. Broadcast seeding of cover cropsinto standing crops is less dependable than otherseeding methods. Success will depend on manyfactors, including adequate rainfall amount anddistribution after seeding.

Kill the rye once it is about knee-high, or let itgo a bit longer,killing it a couple of weeks beforeplanting beans. Killing the rye with herbicidesand no-tilling beans in narrow rows allows moretime for cover crop growth, since you don’t haveto work the ground. If soil moisture is low, con-sider killing the rye earlier. Follow the beans withhairy vetch or a vetch/small grain mixture.

Legumes must be seeded at least 6 weeksbefore hard frost to ensure winter survival. Seedby drilling after soybean harvest, or by over-seeding before leaf drop. Allow the vetch (ormixture) to grow as long as possible in spring formaximum N fixation.

Harvesting sweet corn, seed corn or silage cornopens a window for timely cover crop planting.Harvest or graze the small grain or legume / smallgrain mixture in spring if needed for feed.See indi-vidual cover crop chapters for management details.

In Pennsylvania,Ed Quigley seeds rye or springoats after corn silage harvest.The oats can be cutfor silage in fall if planted by early September.Ryecan bemade into rylage or sprayed before no-till cornthe following spring.Worried about

planting your corna bit late becauseyou’re waiting foryour cover crop tomature? Research inMaryland, Illinois andelsewhere suggeststhat no-tilling corntowards the end ofthe usual window when using a legume covercrop has its rewards. The delay can result ingreater yields than earlier planting, due to greatermoisture conservation and more N produced bythe cover crop, or due to the timing of summerdrought (82, 84, 300). In Pennsylvania, however,delayed planting sometimes reduced corn yieldsfollowing rye (118).

Check your state variety trial data for a shorterseason corn hybrid that yields nearly as well asslightly longer season corn.The cover crop bene-fit should overcome many yield differences.Worried about soil moisture? There’s no

question that growing cover crops may consumesoil moisture needed by the next crop. In humidregions, this is a problem only in an unusually dryspring.Time permitting, allow 2 to 3 weeks afterkilling the cover crop to alleviate this problem.While spring rainfall may compensate for themoisture demand of most cover crops by normalplanting dates, cover crops can quickly dry out afield. Later in the season, killed cover cropresidues in conservation tillage systems can con-serve moisture and increase yields.

In dryland areas of the Southern Great Plains,lack of water limits cover crop use. (See DrylandCereal Cropping Systems, p. 42).

Growers are

looking to add

a small grain to

their corn>soybean

rotation.


In any system where you are using accumulat-ed soil moisture to grow your cash crop,you needto be extra careful. However, as noted in this sec-tion and elsewhere in the book, farmers andresearchers are finding that water-thrifty covercrops may be able to replace even a fallow yearwithout adversely affecting the cash crop.

Corn>Rye>Soybeans>Small Grain>Hairy Vetch.This rotation is similar to the corn>rye>soybeansrotation described above,except you add a year ofsmall grains following the beans. In crop rotationresearch from different areas, many benefitsaccrue as the rotation becomes longer. This isbecause weed, disease and insect pest problemsgenerally decrease with an increase in yearsbetween repeat plantings of the same crop.

Residue from small grains provides good organ-ic matter for soil building, and in the case of win-ter grains, the plants help to prevent erosion overwinter after soybeans loosen up the soil.

The length of the growing season will deter-mine how you fit in cover crops after full-seasonsoybeans in the rotation. Consider using a short-season bean if needed in order to achieve timelyplanting after soybean harvest.Calculate whethercover crop benefits will compensate for a possi-ble yield loss on the shorter season beans. If thereis not enough time to seed a legume after harvest,use a small grain rather than no cover crop at all.

The small grain scavenges leftover N followingbeans. Legume cover crops reduce fertilizer Nneeded by corn, a heavy N feeder. If you cannotseed the legume at least six weeks before a hardfrost, consider overseeding before leaf drop or atlast cultivation.

▼ Precaution. Because hairy vetch is hard seed-ed, it will volunteer in subsequent small graincrops.

An alternate rotation for the lower mid-South iscorn>crimson clover (allowed to go to seed) >soybeans > crimson clover (reseeded) > corn.Allow the crimson clover to go to seed beforeplanting beans. The clover germinates in latesummer under the beans. Kill the cover crop

before corn the next spring. If possible, choose adifferent cover crop following the corn this timeto avoid potential pest and disease problems withthe crimson clover.

▼Precaution. In selecting a cover crop to inter-seed, do not jeopardize your cash crop if soilmoisture is usually limiting during the rest of thecorn season! Banding cover crop seed in rowmiddles by using insecticide boxes or otherdevices can reduce cover crop competition withthe cash crop.

3 Year: Corn>Soybean>Wheat/Red Clover.This well-tested Wisconsin sequence provides Nfor corn as well as weed suppression and naturalcontrol of disease and insect pests. It was moreprofitable in recent years as the cost of syntheticN increased. Corn benefits from legume-fixed N,and from the improved cation exchange capacityin the soil that comes with increasing organicmatter levels.

Growers in the upper Midwest can add a smallgrain to their corn>bean rotation.The small grain,seeded after soybeans, can be used as a covercrop, or it can be grown to maturity for grain.When growing wheat or oats for grain, frost-seedred clover or sweet-clover in March, harvest thegrain, then let the clover grow until it goes dor-mant in late fall.Follow with corn the next spring.Some secondary tillage can be done in the fall, ifconditions allow. One option is to attach sweepsto your chisel plow and run them about 2 inchesdeep, cutting the clover crowns.

Alternatively, grow the small grain to maturity,harvest, then immediately plant a legume covercrop such as hairy vetch or berseem clover in JulyorAugust. Soil moisture is critical for quick germi-nation and good growth before frost. For much ofthe northern U.S., there is not time to plant alegume after soybean harvest, unless it can beseeded aerially or at the last cultivation.If growingspring grains, seed red clover or sweet-cloverdirectly with the small grain.

An Iowa study compared no-till and conven-tional tillage corn>soybean>wheat/clover rota-tion with annual applications of composted


swine manure. Berseem clover or red clover wasfrostseeded into wheat in March. Corn and soy-bean yields were lower in no-till plots the firstyear,while wheat yield was not affected by tillage.With yearly application of composted swinemanure, however, yield of both corn and soybeanwere the same for both systems beginning in yeartwo of the 4-year study (385).

Adding a small grain to the corn>soybean rota-tion helps control white mold on soybeans, sincetwo years out of beans are needed to reducepathogen populations. Using a grain/legume mixwill scavenge available N from the bean crop,hold soil over winter and begin fixing N for thecorn. Clovers or vetch can be harvested for seed,and red or yellow clover can be left for the secondyear as a green manure crop.

Using a spring seeding of oats and berseemclover has proved effective on Iowa farms thatalso have livestock. The mix tends to favor oatgrain production in dry years and berseem pro-duction in wetter years. Either way the mixtureprovides biomass to increase organic matter andbuild soil.You can clip the berseem several timesbefore flowering for green manure.

▼ Precaution. Planting hairy vetch with smallgrains may make it difficult to harvest a clean graincrop. Instead, seed vetch after small grain harvest.Be sure to watch for volunteer vetch in subsequentsmall grain crops. It is easily controlled with herbi-cides but will result in significant penalties if foundin wheat grain at the elevator.

COVER CROPS FOR VEGETABLEPRODUCTION

Vegetable systems have many windows for covercrops.Periods of one to two months between har-vest of early planted spring crops and planting offall crops can be filled using fast-growing warm-season cover crops such as buckwheat, cowpeas,sorghum-sudangrass hybrid, or another cropadapted to your conditions. As with other crop-ping systems,plant a winter annual cover crop onfields that otherwise would lie fallow.

Where moisture is sufficient, many vegetablecrops can be overseeded with a cover crop,which will then be established and growing aftervegetable harvest. Select cover crops that tolerateshade and harvest traffic, especially where therewill be multiple pickings.Cover crop features: Oats add lots of bio-

mass, are a good nurse crop for spring-seededlegumes, and winterkill,doing away with theneed for spring killingand tilling. Sorghum-sudangrass hybridproduces deep roots andtall, leafy stalks that diewith the first frost.Yellow sweetclover isa deep rooting legumethat provides cuttings ofgreen manure in its sec-ond year. White cloveris a persistent perennialand good N source. Brassicas and mustardscan play a role in pest suppression and nutrientmanagement. Mixtures of hairy vetch andcereal rye are increasing used in vegetablesystems to scavenge nutrients and add N to thesystem.

In Zone 5 and cooler, plant rye, oats or a sum-mer annual (in August) after snap bean or sweetcorn harvest for organic matter production anderosion control,especially on sandy soils. Spray orincorporate the following spring,or leave unkilledstrips for continued control of wind erosion.

If you have the option of a full year of covercrops in the East or Midwest, plant hairy vetch inthe spring, allow to grow all year, and it will dieback in the fall. Come back with no-till sweet orfield corn or another N-demanding crop thefollowing spring. Or, hairy vetch planted afterabout August 1 will overwinter in most zoneswith adequate snow coverage. Allow it to growuntil early flower the following spring to achievefull N value. Kill for use as an organic mulch forno-till transplants or incorporate and plant a sum-mer crop.

Residue from

small grains

provides organic

matter for soil

building. . . to

prevent erosion

over winter.


You can sow annual ryegrass right after har-vesting an early-spring vegetable crop, allow it togrow for a month or two, then kill, incorporateand plant a fall vegetable.

Some farmers maximize the complementaryweed-suppressing effects of various cover cropspecies by orchestrating peak growth periods,rooting depth and shape, topgrowth differencesand species mixes. See Full-Year Covers TackleToughWeeds (above).

3 Year: Winter Wheat/Legume Interseed>Legume>Potatoes. This eastern Idaho rotationconditions soil, helps fight soil disease and pro-vides N. Sufficient N for standard potatoesdepends on rainfall being average or lower to pre-vent leaching that would put the soil N below theshallow-rooted cash crop.2 Year Options: For vegetable systems in the

Pacific Northwest and elsewhere, plant a winterwheat cover crop followed by sweet corn or

Full-Year Covers Tackle Tough WeedsTROUT RUN, Pa.—Growing cover crops for afull year between cash crops, combined withintensive tillage, helps Eric and Anne Nordellcontrol virtually every type of weed naturethrows at their vegetable farm—even quack-grass. They are also manipulating the system toaddress insects.

The couple experimented with many differentcover crops on their north-central Pennsylvaniafarm while adapting a system to battle quackgrass.Originally modeled on practices developed on acommercial herb farm in the Pacific Northwest,theNordells continue tomakemodifications to fit theirever-changing conditions.

In the fallow year between cash crops, theNordells grow winter cover crops to smotherweeds and improve soil. Combined with sum-mer tillage, the cover crops keep annual weedsfrom setting seed. Cognizant of the benefits ofreduced tillage, they continue to modify theirtillage practices—reducing tillage intensitywhenever possible.

Regular use of cover crops in the year beforevegetables also improves soil quality and mois-ture retention while reducing erosion.“Vegetablecrops return very little to the soil as far as a rootsystem,”says Eric,a frequent speaker on the con-ference circuit. “You cut a head of lettuce andhave nothing left behind. Growing vegetables,we’re always trying to rebuild the soil.”

Continual modification to their system is thename of the game.When they set up their orig-inal 4-year rotation in the early 80’s, tarnished

plant bugs were not an issue on their farm, butin the 90’s they became a major problem in let-tuce. The problem—and the solution!—was intheir management of yellow sweetclover.

In their original rotation, sweetclover wasoverseeded into early cash crops such as let-tuce. After overwintering, the sweetclover wasmowed several times the following year beforeplowing it under and planting late vegetablecrops. When the tarnished plant bugs beganmoving in—possibly attracted by the floweringsweetclover—the Nordells realized that mow-ing the sweetclover caused the plant bugs tomove to the adjacent lettuce fields. It was timeto change their system.

Fully committed to the use of cover crops,they first tried to delay mowing of the sweet-clover until after lettuce harvest. Eventually,they decided to revamp their clover manage-ment completely.They now plant sweetcloverin June of the second or fallow year of the rota-tion. This still gives the sweetclover plenty oftime to produce a soil-building root systembefore late vegetables. It flowers later, so theyare no longer mowing it and forcing tarnishedplant bugs into lettuce fields.

Yellow blossom sweetclover—one of thebest cover crop choices for warm-season nitro-gen production—puts down a deep taprootbefore winter if seeded in June or July,observesEric. “That root system loosens the soil, fixesnitrogen, and may even bring up minerals fromthe subsoil with its long tap root.”


onions.Another 2-yr. option is green peas > sum-mer sorghum-sudangrass cover crop > potatoes(in year 2). Or, seed mustard green manure afterwinter or spring wheat.Come back with potatoesthe following year. For maximum biofumigationeffect, incorporate the mustard in the fall (seeBrassicas and Mustards, pp. 81).1 Year: Lettuce>Buckwheat>Buckwheat>

Broccoli>White Clover/Annual Ryegrass.The

Northeast’s early spring vegetable crops oftenleave little residue after their early summer har-vest. Sequential buckwheat plantings suppressweeds, loosen topsoil and attract beneficialinsects. Buckwheat is easy to kill by mowing inpreparation for fall transplants.With light tillage toincorporate the relatively small amount of fast-degrading buckwheat residue,you can then sow awinter grass/legume cover mix to hold soil

Originally part of their weed managementprogram, Eric points out that the clover alonewould not suppress weeds. It works on theirfarm because of their successful managementefforts over a decade to suppress overall weedpressure using intensive tillage, crop rotationand varied cover crops. The same conceptapplies to the tarnished plant bug.Never satis-fied with a single strategy rather than a whole-system approach, the Nordells also beganinterseeding a single row of buckwheat intosuccessive planting of short term cash cropslike lettuce, spinach and peas.

The idea was to create a full-season insec-tiary in the market garden, moderating theboom and bust cycle of good and bad insects.They also hoped that the buckwheat wouldprovide an alternate host for the plant bugs.The strategy seems to be working. Data col-lected as part of a research project with theNortheast Organic Network (NEON) foundvery few tarnished plant bugs in their lettucebut lots in the buckwheat insectiary.

The two pronged cover crop approachusing buckwheat and a different managementregime for sweetclover seems to be doing thetrick.The next step, currently being evaluated,is to mix Italian ryegrass with the sweetcloverto increase root mass and sod developmentbetween June planting and frost.

Rye and vetch are a popular combination tomanage nitrogen. The rye takes up excess Nfrom the soil, preventing leaching. The vetchfixes additional nitrogen which it releases afterit’s killed the following spring.With theAugust

seeding, the Nordells’ rye/vetch mixture pro-duces“a tremendous root system”and much ofits biomass in fall.

The Nordells plow the rye/vetch mix after itgreens up in late March to early April,workingshallowly so as not to turn up as many weedseeds. They understand that such early kill sac-rifices some biomass and N for earlier plantingof their cash crop—tomatoes, peppers, sum-mer broccoli or leeks—around the end of May.

Thanks to their weed-suppressing covercrops, the Nordells typically spend less than 10hours a season hand-weeding their three acresof cash crops, and never need to hire outsideweeding help. “Don’t overlook the covercrops’ role in improving soil tilth and makingcultivation easier,”adds Eric.Before cover crop-ping, he noticed that their silty soils deterio-rated whenever they grew two cash crops ina row. “When the soil structure declines, itdoesn’t hold moisture and we get a buildup ofannual weeds,”he notes.

The Nordells can afford to keep half theirland in cover crops because their tax bills andland value are not as high as market gardenersin a more urban setting. “We take some landout of production,but in our situation,we havethe land,” Eric says. “If we had to hire peoplefor weed control, it would be more costly.”

To order a video describing this system ($10postpaid) or a booklet of articles from theSmall Farmers’ Journal ($12 postpaid),write toEric and Anne Nordell, Beech Grove Farm,3410 Route 184,Trout Run, PA 17771.Updated in 2007 by Andy Clark


throughout the fall and over winter. Planted atleast 40 days before frost, the white clover shouldoverwinter and provide green manure or a livingmulch the next year.California Vegetable Crop Systems

Innovative work in California includes rotatingcover crops as well as cash crops, adding diversi-ty to the system.This was done in response to anincrease in Alternaria blight in LANA vetch ifplanted year after year.4 Year: LANA Vetch>Corn>Oats/Vetch>

Dry Beans>Common Vetch>Tomatoes>S-SHybrid/ Cowpea>Safflower. The N needs ofthe cash crops of sweet corn,dry beans,safflowerand canning tomatoes determine, in part, whichcovers to grow.Corn,with the highest N demand,is preceded by LANA vetch,which produces moreN than other covers. Before tomatoes, commonvetch works best. A mixture of purple vetchand oats is grown before dry beans, and a mixof sorghum-sudangrass and cowpeas precedessafflower.

In order to get maximum biomass and N pro-duction byApril 1,LANA vetch is best planted earlyenough (6 to 8 weeks before frost) to have goodgrowth before“winter.” Disked in earlyApril, LANA

provides all but about 40 lb. N/A to the sweetcorn crop. Common vetch, seeded after the corn,can fix most of the N required by the subsequenttomato crop,with about 30 to 40 lb.N/A added asstarter.

A mixture of sorghum-sudangrass and cowpeasis planted following tomato harvest.The mixtureresponds to residual N levels with N-scavengingby the grass component to prevent winter leach-ing. The cowpeas fix enough N for early growthof the subsequent safflower cash crop,which hasrelatively low initial N demands.The cover cropbreaks down fast enough to supply safflower’slater-season N demand.

▼ Precaution. If you are not using any herbi-cides, vetch could become a problem in theCalifornia system.Earlier kill sacrifices N,but doesnot allow for the production of hard seed thatstays viable for several seasons.

COVERCROPS FORCOTTONPRODUCTION

In what wouldotherwise be con-tinuous cotton pro-duction, any winterannual cover crop addedto the system can addrotation benefits,help maintain soilproductivity, andprovide the manyother benefits of cover crops highlightedthroughout this book.

Hairy vetch, crimson clover, or mixtures withrye or another small grain can reduce erosion,addN and organic matter to the system. Drill aftershredding stalks in the fall and kill by spraying ormowing prior to no-till seeding of cotton in May.Or,aerially seed just before application of defoliant.The dropping leaves mulch the cover crop seed,aiding germination. Rye works better than wheat.Yields are usually equal to,or greater than yields inconventional tillage systems with winter fallow.

Balansa clover, a promising cover crop for theSouth, reseeds well in no-till cotton systems (seeUp-and-Coming Cover Crops, p. 191).1 Year: Rye/Legume>Cotton. Plant the

rye/legume mix in early October, or early enoughto allow the legume to establish well before cool-er winter temperatures. Kill by late April, and ifsoil moisture permits, no-till plant cotton withinthree to five days using tined-wheel row cleanerattachments to clear residue. Band-spray normalpreemergent herbicides over the cleaned andplanted row area. Cotton will need additional

ANNUAL and PERENNIAL MEDICcultivars can fix N on low moistureand can reduce erosion in drylandareas compared with bare fallowbetween crop seasons.


weed control toward layby using flaming, cultiva-tion or directed herbicides. Crimson clover, hairyvetch, Cahaba vetch and Austrian winter peas areeffective legumes in this system.Multiyear: Reseeding Legume>No-Till

Cotton> Legume>No-Till Cotton. Subterraneanclover, Southern spotted burclover, balansa cloverand some crimson clover cultivars set seed quick-ly enough in some areas to become perpetuallyreseeding when cotton planting dates are lateenough in spring.Germination of hard seed in latesummer provides soil erosion protection overwinter, N for the following crop and an organicmulch at planting.

Strip planting into reseeding legumes works formany crops in the South, including cotton, corn,sweet potatoes, peanuts, peppers, cucumbers,cabbage and snap beans. Tillage or herbicidesare used to create strips 12 to 30 inches wide.Wider killed strips reduce moisture competitionby the cover crop before it dies back naturally,butalso reduce the amount of seed set, biomass andN produced. Wider strips also decrease themulching effect from the cover crop residue.The remaining strips of living cover crop act asin-field insectary areas to increase overall insectpopulations, resulting in more beneficial insectsto control pest insects.

Start Where You AreIn many instances, you can begin using covercrops without substantially altering your cashcrop mix or planting times or buying newmachinery. Later, you might want to changeyour rotation or other practices to take betteradvantage of cover crop benefits.

We’ll use a basic Corn Belt situation as amodel. From a corn>soybean rotation, you canexpand to:Corn>Cover>Soybean>Cover. Most popu-

lar choices are rye or rye/vetch mixture follow-ing corn; vetch or rye/vetch mixture followingbeans. Broadcast or drill covers immediatelyafter harvest.Hairy vetch needs at least 15 daysbefore frost in 60° F soil. Rye will germinate aslong as soil is just above freezing.Drill for quick-er germination.Consider overseeding at leaf-yel-lowing if your post-harvest planting window istoo short.

If you want to make certain the legume iswell established for maximum spring N and bio-mass production, consider adding a small grainto your rotation.Corn>Soybean>Small Grain/Cover. Small

grains could be oats, wheat or barley. Covercould be vetch, field peas or red clover. If youwant the legume to winterkill to eliminate

spring cover crop killing, try a non-hardy cul-tivar of berseem clover or annual alfalfa.

If you have livestock, a forage/hay marketoption or want more soil benefits, choose alonger-lived legume cover.Corn>Soybean>Small Grain/Legume>

Legume Hay, Pasture or Green Manure.Yellow sweetclover or red clover are popularforage choices. An oats/berseem interseedingprovides a forage option the first year.Harvesting the cover crop or terminating itearly in its second season opens up newoptions for cash crops or a second cover crop.

Late-season tomatoes, peppers, vine crops orsweet corn all thrive in the warm,enriched soilfollowing a green manure.Two heat-loving cov-ers that could be planted after killing a cool-sea-son legume green manure are buckwheat (usedto smother weeds, attract beneficial insects orfor grain harvest) and sorghum-sudangrasshybrid (for quick plow-down biomass or tofracture compacted subsoil).

These crops would work most places in theCorn Belt.To get started in your area, check TopRegional Cover Crop Species (p.66) to fill variousroles, or Cultural Traits and Planting (p. 69) tofind which cover crops fit best in your system.


▼Precautions•Watch for moisture depletion if spring is

unusually dry.• Be sure to plant cotton by soil temperature

(65° F is required), because cover crops maykeep soil cool in the spring.Don’t plant tooearly!

• A delay of two to three weeks between covercrop kill and cotton planting reduces theseproblems, and reduces the chance of standlosses due to insects (cutworm), diseases orallelopathic chemicals.

• Additional mid-summer weed protection isneeded during the hot-season“down time” forthe reseeding legumes.

• Reseeding depends on adequate hard seed pro-duction by the clovers.Dry summer weatherfavors hard seed production while wet sum-mers reduce the percentage of hard seed.

DRYLAND CEREAL-LEGUMECROPPING SYSTEMS

Soil moisture availability and use by cover cropsare the dominant concerns in dryland productionsystems.Yet more and more innovators are findingthat carefully managed and selected cover cropsin their rotations result in increased soil moistureavailability to their cash crops. They are findingways to incorporate cover crops into flexible rota-tions that can be modified to capitalize on soilmoisture when available while preventingadverse effects on cash crops. This delicate bal-ance between water use by the cover crop andwater conservation—particularly in conservationtillage systems—will dictate, in part, how covercrops work in your rotation. See also ManagingCover Crops in Conservation Tillage Systems(p. 44).

Perennial legumes provide numerous benefitsto grain cropping systems in the Northern Plains,including increased grain yield, nutrient scaveng-ing, carbon sequestration, breaking weed andinsects cycles and for use as feed (129).

Cover crop features:perennial medics persistdue to hard seed (of concern in some systems),

providing green manure and erosion control;field peas and lentils (grain legumes) are shal-low-rooted yet produce crops and additional N inyears of good rainfall.

An excellent resource describing these rota-tions in detail is Cereal-Legume CroppingSystems:Nine Farm Case Studies in the DrylandNorthern Plains, Canadian Prairies andIntermountain Northwest (258).7 to 13 Years: Flax>Winter Wheat>Spring

Barley>Buckwheat>Spring Wheat>WinterWheat>Alfalfa (up to 6 years) >Fallow

System sequences are:• Flax or other spring crops (buckwheat,wheat,

barley) are followed by fall-seeded wheat(sometimes rye), harvested in July, leavingstubble over the winter;

• Spring-seeded barley or oats, harvested inAugust, leaving stubble over the winter;

• Buckwheat, seeded in June and harvested inOctober, helps to control weeds;

• A spring small grain,which outcompetes anyvolunteer buckwheat (alternately, fall-seededwheat, or fall-seeded sweetclover for seed orhay).

The rotation closes with up to 6 years of alfalfa,plowdown of sweetclover seeded with the previ-ous year’s wheat or an annual legume greenmanure such as Austrian winter peas or berseemclover.

There are many points during this rotationwhere a different cash crop or cover crop canbe substituted,particularly in response to marketconditions. Furthermore, with cattle on theranch, many of the crops can be grazed or cutfor hay.

Moving into areas with more than 12 inches ofrain a year opens additional windows for incor-porating cover crops into dryland systems.9 Year: Winter Wheat>Spring Wheat>

Spring Grain/Legume Interseed>LegumeGreen Manure/Fallow>Winter Wheat>Spring Wheat>Grain/Legume Interseed>Legume> Legume. In this rotation, one year of


winter wheat and two years of spring-seededcrops follow a two or three-year legume break.Each legume sequence ends with an early sum-mer incorporation of the legume to save moisturefollowed by minimal surface tillage to controlweeds. Deep-rooted winter wheat follows sweet-clover, which can leave surface soil layers fairlydry. Spring-seeded grains prevent weeds thatshow up with successive winter grain cycles andhave shallower roots that allow soil moisture tobuild up deeper in the profile.

In the second spring-grain year, using a low-Ndemanding crop such as kamut wheat reducesthe risk of N-deficiency. Sweetclover seeded withthe kamut provides regrowth the next spring thathelps to take up enough soil water to preventsaline seep. Black medic, INDIANHEAD lentils andfield peas are water-efficient substitutes for thedeep-rooted—and water hungry—alfalfa andsweetclover. These peas and lentils are spring-sown, providing back-up N production if the for-age legumes fail to establish.

While moisture levels fluctuate critically fromyear to year in dryland systems,N levels tend to bemore stable than in the hot, humid South, andadding crop residue builds up soil organic mattermore easily.Careful management of low-water usecover crops can minimize soil water loss whileadding organic matter and N. Consequently, dry-land rotations can have a significant impact onsoils and the field environment when used over anumber of years.

These improved soils have higher organic mat-ter, a crumbly structure,and good water retentionand infiltration.They also resist compaction andeffectively cycle nutrients from residue to subse-quent crops.

Remember, the benefits of cover crops accrueover several years.You will see improvements incrop yield, pest management and soil tilth if youcommit to cover crop use whenever and wherev-er possible in your rotations.


INTRODUCTION

Conservation tillage is defined as a system thatleaves enough crop residue on the soil surfaceafter planting to provide 30% soil cover, theamount needed to reduce erosion below toler-ance levels (SSSA). Today, however, most conser-vation tillage practitioners aim for greater soilcover because of additional benefits of cropresidue.Cover crops are critical to producing thisresidue and have the potential to maximize con-servation tillage benefits.

Benefits of conservation tillage systems include:• reduced soil erosion• decreased labor and energy inputs• increased availability of water for crop production• improved soil quality

Cover crops further benefit conservation tillagesystems by:• producing crop residues that increase soil

organic matter and help control weeds• improving soil structure and increasing infiltration• protecting the soil surface and dissipating rain-

drop energy• reducing the velocity of water moving over

the soil surface• anchoring soil and adding carbon deep in the

soil profile (via roots)

Conservation tillage has been adopted on moreand more acres since the 1970’s thanks toimprovements in equipment, herbicides andother technologies. Several long-term, incremen-tal benefits of conservation tillage have emerged.The most important benefits have been attributedto the accumulation of organic matter at the soilsurface.

This accumulation of surface organic matterresults in:• increased aggregate stability,which helps to

increase soil water infiltration and resist erosion• improved nutrient cycling and water quality,

due to keeping nutrients in the field• increased biological activity,which improves

nutrient cycling and can influence diseasesand pests

Additional benefits from conservation tillage sys-tems compared to intensive or conventionaltillage systems (89) include:• Reduced labor and time—one or two trips to

prepare land and plant compared to three ormore reduces labor and fuel costs by 50% ormore.

• Reduced machinery wear—fewer trips meanfewer repairs.

• Increased wildlife—crop residues provideshelter and food for wildlife, such as gamebirds and small animals,which can result inadditional farm revenue.

• Improved air quality—by reducing winderosion (amount of dust in the air), fossil fuelemissions from tractors (fewer trips) andrelease of carbon dioxide into the atmosphere(tillage stimulates the release of carbon fromorganic matter).

In an Iowa study comparing no-till and conven-tional tillage in a corn>soybean>wheat/cloverrotation, corn and soybean yields were lower inno-till plots the first year.With yearly applicationof composted swine manure, however, yield ofboth corn and soybean were the same for bothsystems beginning in year two of the study.Wheatyields were not affected by tillage, but increasedwith compost application (385).

MANAGING COVER CROPS IN CONSERVATIONTILLAGE SYSTEMSby Kipling Balkcom, Harry Schomberg,Wayne Reeves and Andy Clarkwith Louis Baumhardt, Hal Collins, Jorge Delgado, Sjoerd Duiker, Tom Kaspar and Jeffrey Mitchell

MANAGING COVER CROPS IN CONSERVATION TILLAGE SYSTEMS 45

Cover crop contributions toconservation tillage systemsBiomass. Conservation tillage systems dependon having crop residues on the soil surface formost of the year. Cover crops help provide theadditional biomass needed to meet this year-round requirement. A typical high residue covercrop should contain at least 4000 lb. biomass/A.

In low-fertility soils, you can increase biomassproduction of grass cover crops with the additionof a small amount of N fertilizer. Cover cropsgrown in soils with higher levels of organic mat-ter, or following a legume summer crop like soy-bean, may not need additional N fertilizer.Remember, minimal cover crop residue or bio-mass translates into minimal benefits.Soil improvement. Cover crop biomass is a

source of organic matter that stimulates soil bio-logical activity.Soil organic matter and cover cropresidues improve soil physical properties, result-ing in:• greater water infiltration, due to direct effects

of the residue coverage or to changes in soilstructure

• greater soil aggregation or tilth, resulting inbetter nutrient and moisture management

• less surface sealing, because residue interceptsrain drops, reducing the dispersal of clay parti-cles during a rainfall or irrigation event

• greater soil porosity, due to the macroporesthat are formed as roots die and decompose

Improvements in soil physical properties dependon soil type, crops grown and residue manage-ment system, as well as temperature and rainfall.Regardless of soil type, however, tillage will veryquickly negate cover crop benefits associatedwith increased soil organic matter. Simply put,tillage breaks down organic matter much fasterthan no-till.

Improvements in soil physical properties dueto cover crops have been documented widely inconservation tillage systems (25,52,106,114,115,119, 238, 318, 419).Erosion control. Cover crops and conserva-

tion tillage combine to reduce soil erosion andwind erosion (26, 115, 119, 223, 267).

In Kentucky,on a Maury silt loam soil with a 5%slope, soil loss was 8 tons/A for conventionallytilled corn with the corn residue and cover cropturned under in the spring. In contrast, for no-tillage corn with 3 tons/A of corn residue remain-ing on the soil surface,soil loss was 1 ton/Awithout a cover crop and0.9 tons/A with a wintercover crop (91,151).

In Missouri, on aMexico series silt loamsoil with a claypan,inclusion of a rye orwheat cover crop reduced soil loss in no-tillagesilage corn from 9.8 to 0.4 tons/A/year (437).Rotation effects. Crop rotation provides

numerous benefits to any cropping system. It iscritical to reducing the incidence of diseases andpests,and is also credited with improving nutrientuse and reducing weeds.Cover crops increase thecomplexity and intensity of crop rotations, effec-tively increasing crop rotation benefits. Note,however, as addressed throughout this book, thatcover crops can adversely affect other crops inthe rotation.

Cover crop management inconservation tillage systemsNutrient management. Nitrogen and phospho-rus are the two macronutrients most likely to belost from cropping systems. Cover crops helpreduce losses of these nutrients by:• increasing infiltration—thus reducing surface

runoff and erosion• taking up nutrients—or acting as a ‘catch crop’• using water for cover crop growth during

peak leaching season (late fall through earlyspring)—reducing the amount of water avail-able to leach nutrients

Grasses and brassicas are better than legumes atreducing N leaching (106, 234, 265). Cereal rye isvery effective at reducing N leaching because it iscold tolerant, has rapid growth, and produces alarge quantity of biomass (111). Winter annualweeds do not effectively reduce N losses.

Tillage breaks

down organic

matter much

faster than no-till.


Cover crops may reduce the efficiency of N fer-tilizer in no-till systems,depending on the methodof application. Surface applications of urea-con-taining fertilizers to soils with large amounts ofcover crop residues can result in large losses ofammonia N.When applied to the soil surface,ureaand urea-ammonium nitrate (UAN) solutionsvolatilize more than ammonium nitrate and sub-sequently lose more N to the atmosphere.

Injecting urea-containing fertilizers into the soileliminates volatilization losses. Banding urea-con-taining fertilizers also reduces volatilization lossesbecause banding minimizes fertilizer and residuecontact,while increasing fertilizer and soil contact.Nitrogen dynamics with nonlegume cover

crops. Differences between nonlegumes andlegume cover crops are mostly related to nitrogenmanagement. Legumes fix N while nonlegumescan only use N already in the soil. Legumeresidues usually contain more total N that is morereadily available to subsequent crops.

The addition of fresh crop residues stimulatesgrowth of soil microbes and increases microbialdemand for nutrients, particularly N. Micro-organisms use C, N and other nutrients as a foodsource in order to break down the residues. If theamount of N in the residues is too low, themicroorganisms use soil N instead, reducing Navailability to the cash crop. This is called Nimmobilization. If the amount of N in theresidues is greater than microbial demand, N isreleased and N availability for plant growth isincreased, a process called N mineralization.

Small grain and other grass cover crops usuallyresult in an initial, if not persistent, immobilizationof N during the cash crop season.The N contentof small grain cover crop residues varies greatly,but generally ranges from 20 to 50 lb./A for theaboveground biomass and 8 to 20 lb./A in theroots.The N contribution from small grain covercrops depends on N availability during the covercrop growing period, the total amount of biomassproduced and the growth stage when the cover isterminated.

The carbon to nitrogen ratio (C:N ratio) ofcover crop residue is a good indicator of whetherimmobilization or mineralization will occur.

Values exceeding 30 parts carbon to one partnitrogen (C:N ratio of 30:1) are generally expect-ed to immobilize N during the early stages of thedecomposition process. For more informationabout C:N ratios and cover crop nutrient dynam-ics, see Building Soil Fertility and Tilth withCover Crops (pp. 16).

The C:N ratio of small grain residues is mostlydependent on time of termination. Early termina-tion of grass cover crops results in a narrower C:Nratio, typical of young plant tissue. If killed tooearly, this narrower C:N ratio results in rapiddecomposition of a smaller amount of residue,reducing ground coverage.

Because of the need for residue in conservationtillage systems, small grain cover crops are oftenallowed to grow as long as possible.Terminationdate depends on crop rotation and climate.Whensmall grain cover crops are killed at flowering, theC:N ratio is usually greater than 30:1.

In Pennsylvania, delaying rye termination datefrom early to late boot stage increased averageabove-ground dry matter accumulation from 1200to 3700 lb./A with no negative effect on cornyield (118).

In Alabama, rye, black oat and wheat covercrops were terminated at different growth stageswith a roller or roller-herbicide combinations.Biomass production was about 2.0 – 2.6 tons/A atthe flag leaf stage and corresponding C:N ratioaveraged 25:1, regardless of cover crop species.

At flowering,biomass averaged 4.2,3.8, and 3.3tons/A for black oat, rye and wheat, respectively,and the C:N ratio for all covers was 36:1.Killing atsoft dough stage did not increase biomass pro-duction for any of the covers,but did increase theC:N ratios, which would increase N immobiliza-tion (13).

The wide C:N ratio of small grain residues mustbe taken into account for best N management.Nitrogen fertilizer rates for cash crops may needto be increased 25 to 30 lb./A following a highresidue cereal cover crop.

In N-limited soils, early-season growth of thecash crop is usually enhanced if this N is appliedas starter fertilizer.Although yield increases fromstarter N applications are dependent on rainfall


and crop, they occur frequently enough to justifythe practice. Starter fertilizer promotes morerapid canopy development, which reduces weedcompetition and can offset the negative effects ofcool, wet soils often experienced with conserva-tion tillage systems. Ideally, starter fertilizersshould be placed near the seeding row in a 2 X 2band, i.e. 2 inches to the side and 2 inches belowthe seed.Legumes add N. Legume cover crops obtain

nitrogen from the atmosphere through a symbiot-ic relationship with nitrogen fixing bacteria.TheN content of legume cover crops and the amountof N available to subsequent crops is affected by:• Legume species and adaptation to soil and

climatic conditions• residual soil N• planting date• termination date

Cover crop management affects the N content oflegume cover crops and the contribution of N tothe following cash crop. Early establishment oflegume cover crops results in greater biomassproduction and N production.The nitrogen con-tent of legume cover crops is optimized at theflowering stage. Legumes can contribute from 15to 200 lb. N/A to the subsequent crop, with typi-cal values of 50 to 100 lb./A.

In North Carolina,delaying the kill date of crim-son clover 2 weeks beyond 50% bloom,and hairyvetch 2 weeks beyond 25% bloom increased thebiomass of clover by 41% and vetch by 61%.Corresponding increases in N content were 23%for clover and 41% for vetch (427). In Maryland,hairy vetch fixed about 2 lb. N/acre/day fromApril 10 to May 5, resulting in an additional 60 lb.N/A in aboveground biomass (82, 83, 86).

The C:N ratio of mature legume residues variesfrom 25:l to 9:1 and is typically well below 20:1,the guideline threshold where rapid mineraliza-tion of the N in the residue occurs. Residueson the soil surface decompose more slowlythan those incorporated in conventional tillagesystems.Consequently, in conservation tillage sys-tems, legume-residue N may not be readily avail-able during the early part of the growing season.

Due to the initial lag in availability of N fromlegume cover crop residues, any additional fertil-izer N should be applied to cash crops at plantingin conservation-tillage winter annual legume sys-tems. Splitting N applications to corn grown inthese systems, as is generally recommended forconventional-tilled corn grown without legumecover crops, is not necessary (347).Grass-legume mixtures. Mixtures of grass

and legume cover crops provide the same bene-fits to conservation tillage but often mitigate thenitrogen immobilization of pure grass covercrops. The grass component scavenges residualnitrogen effectively, while the legume adds fixednitrogen that is more readily available to the cashcrop (86, 343, 344, 345).

The C:N ratio of grass-legume mixtures is usu-ally intermediate to that of pure stands. In severalstudies in Maryland, the C:N ratio of mixtures ofhairy vetch and rye never exceeded 25:1; the C:Nratio of pure rye ranged from 30:1 to 66:1 acrossseveral spring kill dates (81, 83, 84, 85, 86).Water availability. Cover crops use soil water

while they are growing.This can negatively affectcash crop yields.Once killed, however, cover cropresidues may increase water availability by increas-ing infiltration and reducing evaporation losses.

Short-term soil water depletion at planting mayor may not be offset by soil water conservationlater in the growing season.This is dependent onrainfall distribution in relation to crop develop-ment. A rainfall event following cover crop termi-nation enables soil surface water recharge,whichusually provides adequate soil moisture in humidregions to facilitate cash crop planting. Time oftermination becomes more critical as the proba-bility of precipitation decreases (423).

Cover crops increase water availability by:• decreasing evaporation due to a mulching

effect• increasing infiltration of rainfall by decreasing

runoff velocity• increasing organic matter,which increases

water-holding capacity• improving soil structure and consequently

increasing root interception of soil water


• protecting the soil surface from raindropimpact, thus reducing development of a sur-face seal or crust,which can greatly reduceinfiltration

InAlabama,cover crop residue left on the soil sur-face reduced runoff and increased infiltration by50 to 800% compared to removing or incorporat-ing the residues (418,419). In Georgia, infiltrationrates were 100% greater even after removal ofcrop residues for a Cecil sandy loam when grainsorghum was no-till planted into crimson clovercompared to a tilled seedbed without a covercrop (52).

In Maryland, pure and mixed stands of hairyvetch and rye did not deplete soil water oradversely affect corn yield. Rather, the additionalresidue from cover crops killed in early May con-served soil moisture and contributed to greatercorn yield (84, 85).

In Kentucky, surface evaporation from May toSeptember was five times less under no-till(which leaves a surface mulch) than with con-ventional tillage. Because less water was lost toevaporation, more water was available for thecrop (91).

Cover crop use in dryland systems is oftenlimited by moisture availability. A literaturereview of dryland cover crop studies on the GreatPlains concluded that use of cover crops on dry-land cropping systems of the Great Plainsreduced yields of subsequent crops. However, insemi-aridTexas,5 tons/A of wheat straw increasedavailable soil water by 73% and more than dou-bled grain sorghum yields from 26 to 59bushels/A (423).

The risk for early-season soil water depletion bycover crops is the same regardless of the tillagesystem.However, the full potential of cover cropsto increase infiltration and conserve soil watercan only be achieved in a conservation systemwhere cover crop residues are left on the surface.Conservation tillage increased water use efficien-cy compared to a traditional wheat>fallow systemwith tillage (319, 135).

One way to reduce the risk of early-season soilwater depletion by cover crops is to desiccate thecover some time prior to planting the cash crop.

For example, yield reductions due to early-seasondepletion of soil water can be reduced by killingthe cover crop 2 to 3 weeks before planting thecash crop (428, 290, 348).Depending on your sit-uation, you could extend this window to termi-nate cover crops in conservation systems from 4to 6 weeks prior to planting the cash crop.

Cover crops can sometimes be used to depletesoil water on poorly drained soils,allowing an ear-lier planting date for the cash crop, but the prac-tical advantage of this practice is not certain.Soil temperature. Cover crop residues keep

the soil cooler, reduce daily fluctuations of soiltemperature, and reduce soil temperature maxi-mums and minimums. The cooler soil tempera-tures, which benefit the cash crop throughoutthe summer, can delay spring planting comparedto a system without a cover crop.

Spring soil temperature is particularly impor-tant in cover crop/conservation tillage systems.Where possible, plant your cash crop accordingto soil temperature rather than the calendar.Follow local recommendations about the appro-priate soil temperature for your cash crop. Asnoted below, the use of row cleaners will allowfaster soil warmup.

The harmful effects of planting when the soiltemperature is too low were demonstrated inColorado for conservation tillage with continuouscorn (but not cover crops).Low soil temperaturescontributed to reduced corn yields over 5 years(171, 172).Insects and diseases. Conservation tillage sys-

tems alter pest dynamics, due in large part toresidues left on the soil surface. Conservationtillage systems with surface residues create amore diverse plant/soil ecosystem than conven-tional tillage systems (137, 185, 416).

Cover crops may harbor insects, diseases, andnematodes that could be harmful to the cashcrop. Before planting a cover crop, be sure toinvestigate specific pest/crop interactions thatmay become a problem (100). Understandingthese interactions and the conditions that favorthem helps you make good management deci-sions. For example:• Cereal rye, orchardgrass and crimson clover

may attract armyworms.


• Clover root curculio, a common pest of redclover, can attack alfalfa.

• Chickweed can attract black cutworm orslugs.

• Johnsongrass is a host to maize dwarf mosaicvirus (MDMV),which also infects corn.

Conversely, cover crops can be used in conserva-tion tillage systems to attract beneficial insects.One approach is to allow a live strip of covercrops to remain between crop rows to serve ashabitat and a food source until the main crop isestablished. This approach resulted in one lessinsecticide application in conservation-tilled cot-ton compared to conventional cotton in SouthGeorgia (368, 416).

For more information about cover crops andbeneficial insects, see Manage Insects on YourFarm: A Guide to Ecological Strategies (409,http://www.sare.org/publications/insect.htm).

Cover crop residues have been shown toreduce the incidence of several diseases in manydifferent cash crop systems by reducing splashdispersal of pathogens. Small grain cover crops inconservation tillage have also been shown toreduce peanut yield losses from Tomato SpottedWilt Virus (TSWV), with greater residue amountsresulting in lower incidence of TSWV. Thisbenefit was directly related to less incidence ofdamage from thrips, the vector of TSWV (49).

Some cover crops can serve as an overwinter-ing host for nematodes and may thus increase theseverity of nematode damage. This may be agreater concern where crops are not rotated, likecontinuous cotton in some areas of the South.Onthe other hand, cover crops such as brassicas canreduce nematode populations (48, 231, 283, 284,285, 353, 430).

On a Maryland sandy soil, winterkilled forageradish increased bacteria-eating nematodes, ryeand rapeseed increased the proportion of fungalfeeding nematodes,while nematode communitieswithout cover crops were intermediate. TheEnrichment Index, which indicates a greaterabundance of opportunistic bacteria–eatingnematodes, was 23% higher in soils that hadbrassica cover crops than the unweeded controlplots.These samples, taken in November, June (a

month after springcover crop kill), andAugust (under corn),suggest that the covercrops, living or dead,increased bacterialactivity and may haveenhanced nitrogencycling through the food web (432).

The need for sound crop rotation is greater inconservation systems than in conventional sys-tems. Cover crops should be a key component ofany conservation rotation system. With the vastnumber of potential combinations of crops,covercrops, and diseases, consult local experts toensure that you manage cover crops in conserva-tion tillage systems to minimize the potential forpest problems.Weed management. Cover crops affect

weeds and weed management in conservationtillage systems in several ways:• Cover crops compete with weeds for light,

water and nutrients.• Cover crop residue can suppress weed seed

germination; the more residue the better.• Grass cover crops (high C:N ratio) usually pro-

vide longer-lasting residue than legumes.• Some cover crops release weed-suppressing

allelopathic compounds.• Conservation tillage does not continually turn

up new weed seeds for germination.• Cover crops can become weeds.

Some legume, cereal and brassica cover cropsrelease allelopathic compounds that can reduceweed populations and/or suppress weed growth(39, 45, 176, 177, 178, 336, 359, 410, 422).Unfortunately, these same allelopathic com-pounds can also stunt and/or kill cash cropseedlings,particularly cotton (24) and some smallseeded vegetable crops. Allowing time betweenthe termination date and the cash crop plantingdate reduces the risk to cash crops because thesechemicals leach out of the cover crop residue andare decomposed by soil microorganisms.

Cereal rye is known to release phenolic andbenzoic acids that can inhibit weed seed germi-nation and development. InArkansas, the concen-

Consult local

experts to minimize

the potential for

pest problems


tration of these allelopathic chemicals varied 100-fold among ten varieties of rye in the boot stage,with the cultivar BONEL having the greatest con-centration and PASTAR the least. Factoring in theyield of each cultivar with the concentration andactivity of the inhibitors, BONEL,MATON and ELBON

were considered the best rye cultivars for allelo-pathic use (66).

Conservation tillage and the allelopathic effectsof cover crop residue can both contribute to thesuppression of weeds in these systems (452). InAlabama, a conservation tillage system using ryeor black oat cover crops eliminated the need forpost-emergence herbicides in soybean and cotton(335, 349). Including rye or black oat increasedyields of non-transgenic cotton in 2 of 3 years,com-pared to conservation tillage without a cover crop.

Economics of cover cropestablishment and useUsing cover crops in any tillage system usuallycosts more time and money than not using covercrops. Depending on your particular system, youmay or may not be repaid for your investmentover the short term. If you are already using covercrops but are considering switching to conserva-tion tillage, the economics are similar to usingcover crops in conventional tillage systems, butthe benefits may be expressed more in the con-servation system (51).

Factors affecting the economics of cover cropuse include:• the cash crop grown• the cover crop selected• time and method of establishment• method of termination• the cash value applied to the environment, soil

productivity and soil protection benefitsderived from the cover crop.

• the cost of nitrogen fertilizer and the fertilizervalue of the cover crop

• the cost of fuel

The economic picture is most affected by seedcosts,energy costs and nitrogen fertility dynamicsin cover crop systems.Cover crop seed costs varyconsiderably from year to year and from region toregion, but historically, legume cover crops cost

about twice as much to establish as small graincovers. The increased cost of the legume covercrop seed can be offset by the value of N thatlegumes can replace.

Depending on your system, legume covercrops can replace 45 to 100 lb. N/A. On theother hand, a rye cover crop terminated at a latestage of growth might require 20-30 lb. moreN/A due to N immobilization by the wide C:Nratio rye residue. Thus, the difference in costbetween a rye cover crop and a legume covercrop would be offset by the value of 65 to 125lb. N/A. At a price of $0.45/lb. N, this would beworth $29 to $56/A.

Cover crop establishment inconservation tillage systemsThe major challenges to cover crop adoption inboth tilled and conservation tillage systemsinclude seeding time and method,killing time andmethod, and cover crop residue management toensure good stands of the cash crop.Success withcover crops requires adequate attention to each.Plant cover crops on time. In order to maxi-

mize benefits—or to work at all—cover crops needto be planted early, sometimes before the summercrop is harvested.Timely planting results in:• good root establishment and topgrowth

before the crops go dormant• reduced chance of winter kill• more biomass production compared to later

planting dates• greater uptake of residual soil N

Timely fall planting is particularly importantbefore early vegetables or corn. Corn is typicallyplanted early in the spring,which forces an earlycover crop termination date. A late planted covercrop that must be terminated early will not pro-duce sufficient biomass to provide adequate soilprotection and enhance soil quality.Planting methods. Cover crops in conserva-

tion tillage systems are usually planted with a drillor broadcast on the soil surface, but several alter-nate methods can be used.Good soil-seed contactis required for germination and emergence. Mostsmall seeded legumes require shallow seed place-ment (1/4 inch),while larger seeded legumes and


small grains are generally planted up to 1.5 inch-es deep (see CHARTS, p. 62).Conservation tillage drills can handle residue

and provide uniform seeding depth and adequateseed-soil contact, even with small seeded covercrops. In some situations, preplant tillage can beused to control weeds and disrupt insect and dis-ease life cycles.Broadcast seeding requires an increase in the

seeding rate compared to other methods (seeCHARTS, p. 62). Broadcasting is often the leastsuccessful seeding method. Small-seeded speciessuch as clovers tend to establish better by broad-casting than larger seed species. A drop-type orcyclone-type seeder can be used on small acreageand provides a uniform distribution of seed.Conventional drills work adequately in some con-servation tillage systems—depending on theamount of residue—and may be more successfulthan broadcast seeding.

On larger areas, aerial seeding by fixed-wingaircraft or helicopter in late summer during cropdie-down can be effective. As the leaves of thesummer crop drop off, they aid germination bycovering the seed, retaining moisture and pro-tecting the soil.

In colder climates, frost-seeding can be usedfor some cover crop species (see individualcover crop chapters in this book). Seed is broad-cast during late fall or early spring when theground has been“honeycombed”by freezing andthawing. The seed falls into the soil cracks andgerminates when the temperature rises in thespring.

Some legumes can be managed to reseed thefollowing year. This reduces economic risks andseeding costs. Reseeding systems generallydepend on well-planned rotations such as thatreported in Alabama (311),where crimson cloverwas followed with strip-tilled soybean plantedlate enough to let the clover reseed. Corn wasgrown the next year in the reseeded clover. In thissystem,the cover crop is planted every other yearrather than annually.Grain sorghum can be plant-ed late enough in the South to allow crimsonclover to reseed in a conservation-tillage system.

The introduction of legume cover crops thatbloom and set seed earlier also improves their util-

ity for reseeding inconservation-tillage sys-tems. Auburn Universityin cooperation withUSDA-NRCS has releasedseveral legume covercrops that flower early,including AU ROBIN

and AU SUNRISE crimsonclover, and AU EARLY

COVER hairy vetch (288). Leaving 25 to 50% of therow area alive when desiccating the cover cropallows reseeding without reducing corn grainyields. However, the strips of live cover crop maycompete with the cash crop for water, a potentialproblem during a spring drought.

Spring management of cover cropsin conservation tillage systemsKill date. Timing of cover crop terminationaffects soil temperature, soil moisture, nutrientcycling, tillage and planting operations, and theeffects of allelopathic compounds on the subse-quent cash crop. Because of the many factorsinvolved, decisions about when to kill the covercrop must be site- and situation-specific.

There are a number of pros and cons of killinga cover crop early vs. late. Early killing:• allows time to replenish soil water• increases the rate of soil warming• reduces phytotoxic effects of residues on cash

crops• reduces survival of disease inoculum• speeds decomposition of residues, decreasing

potential interference with planter operation• increases N mineralization from lower C:N

ratio cover crops

Advantages for later kill include:• more residue available for soil and water con-

servation• better weed control from allelopathic com-

pounds and mulch affect• greater N contribution from legumes• better potential for reseeding of the cover

crop

Decisions about

when to kill the

cover crop must

be site- and

situation-specific.


Talk to 10 no-tillers and you’ll probably hear 10different viewpoints on why it pays to quit dis-turbing and start building the soil.At SheridanFarms,we’ve got our list, too.We are able to bet-ter time planting, weed control and other pro-duction chores. And we’ve got the potentialfor sediment and nutrient runoff into SaginawBay on Lake Huron under control.

Like a lot of no-tillers would testify, however,these changes didn’t come quickly,nor withoutsome reluctance and skepticism along the way.In our first years of no-tilling, starting in 1982,we did just about everything wrong and had anabsolute train wreck.We overcame a few hur-dles early on, started adding more no-till acresand were 100% continuous no-till by 1990.

Cover Crop SuccessWe started working with cover crops about 20years ago.We deal with about a dozen differentsoil types, 80 percent of which are clay loam.And much of our land is poorly drained, low-organic-matter lake bed soils.

Cereal rye has been a good cover crop yearin and year out for this mixture of soils.We likethe AROOSTOCK variety from Maine because itprovides fast fall and spring growth and itssmaller seed size makes it more economical toplant.

In late August, we fly rye into standing cornand also into soybeans if we’re coming backwith soybeans the following year. We learnedthat rye is easier to burn down when it’s morethan 2 feet tall than when it has grown only afoot or less.

The rye crop also helps us effectively managesoil moisture. If it looks like we’re going to geta dry spring,we burn down rye with Roundup

After 25 Years, Improvements Keep ComingBy Pat Sheridan, Sheridan Farms, Fairgrove, Mich as interviewed by Ron Ross for the No-Till Farmer

as soon as we can; but if it’s wet,we let the ryegrow to suck up excess moisture. We can bevery wet in the spring, but Michigan alsoreceives less rain during the growing seasonthan any other Great Lakes state, on average.Moisture management is critical to us.

We’ve seen less whitemold in no-tilled soy-beans wherever we haveheavy residue.We’ve hadyears with zero whitemold when our conven-tional till neighborsfaced a costly problem.It’s become a simpleequation: the heavier theresidue mat, the lesswhite mold.

Deep-Rooted CropsWe’re looking for a covercrop that will help establish a more diverserotation, so we can always follow a broadleafcrop behind a grass crop and vice-versa.Oilseedradish is beginning to show real promise. It hasabout the same tremendous appetite for nitro-gen as wheat, and it develops a very deep rootmass. It’s an excellent nutrient scavenger.

This combination enables the cover crop tocapture maximum nitrogen from deep in thesoil profile to feed the following corn crop.Noone has ever proven to me that we need nutri-ents down deep. It sounds good to have a plantfood layer at 16 to 18 inches, but I much preferthe nitrogen and other nutrients near the sur-face where the crop can use them.

Deep-rooted cover crops like oilseed radishcan help reverse the traditional theory of nitro-

An open mind

welcomes a lot

of ideas that,

with a little

tweaking, can

deliver even

more success

to your fields.


gen stratification. Nitrogen allowed to concen-trate deep in the soil scares us because it ismore likely to leach into the tile lines and reachLake Huron.

We’ve also tried wheat, hairy vetch, crimsonclover and a dry bean and soybean mix forcover crops, and we’ll keep experimenting.Recently, I traded oilseed radish seed to Kansasno-tillers Red and David Sutherland forAustrianwinter pea seed.The Sutherlands have reportedgood moisture retention and nitrogen fixationwith the peas.We like what we’ve seen with thepeas, as well.

Less Nitrogen, More CornWe partly credit the cover crop program withsharply reducing our fertilizer bills. In fact, thefirst time I hit a 200-bushel corn yield, I did itwith only 140 to 150 pounds of nitrogen peracre, or about 0.7 to 0.8 pounds of nitrogenper bushel. As anyone who has been growingcorn knows, the typical nitrogen recommenda-tion has been about a pound-plus per bushel.Oversupplying nitrogen has absolutely novalue. I think the whole nutrient cycle conceptis intriguing; no-till in conjunction with covercrops really makes it work.

Organic Matter BoostWhen we started no-tilling, we had heard sto-ries from farmers and others that we couldexpect to see increased organic matter contentin our soils after a few years. But some soilexperts cautioned that this likely wouldn’t hap-pen. Fortunately, we’ve triggered significanthumus development during the past 20 years,with organic matter increasing from about 0.5to as much as 2.5 percent. This is a real bonusin addition to all the other benefits from no-till-ing, and we expect to see even more improve-ment as we include more cover crops in ourrotation.

What Works At Home?Our county is part of the Saginaw Bay water-shed, the largest in the state with more than8,700 square miles. Everything we do as farm-ers can affect the water quality of the bay, andwe’re very conscious of that.

A group of about 150 farmers from threecounties formed the Innovative Farmers ofMichigan in 1994. Our objectives have been toreduce the amount of sediment entering thebay and change our farming practices toreduce nutrient and pesticide runoff. Wedon’t want our soils in the bay. After a 3-yearstudy, financed with an EPA 319 grant in 1996,we came up with some pretty dramatic results.We found that conservation tillage does notreduce yields; in fact we saw significant yieldincreases in corn.

Also, reduced tillage increases the soil’scapacity to supply nitrogen and phosphorus toa growing crop. Water-holding capacity andwater infiltration rates were higher on no-tillfields.We reduced the potential for soil erosionfrom water by up to 70 percent and from windby up to 60 percent, compared to conventionaltillage.At the end of the project, we were get-ting a lot better handle on what no-till systemswork best in our three-county area.

At Sheridan Farms, we’ll keep looking formore diversity and hope to get back to a four-or five-crop continuous no-till system.The mostvaluable lesson we learned is there is no uni-versal truth or no-till game plan that will applyfor everyone. Eventually, we adapted a no-tillsystem that fits our particular soil types, crops,climate, long-range goals and farming style.

—Adapted with permission from “The No-TillFarmer,”May 2006. www.no-tillfarmer.com


As a general rule, cover crops,particularly cereals,need to be terminated 2-3 weeks ahead of planti-ng to allow plant material to dry out and becomebrittle. Dry brittle cover crop residue allowstillage and planting equipment to cut through theresidue more easily, as opposed to semi-dry covercrop residue. Semi-dry residue is tough and hardto cut, which can result in considerable draggingof the residue as implements traverse the field.

Allelopathic compounds can be a greater prob-lem with crop establishment when fresh residuesbecome trapped in the seed furrow, a conditionknown as “hairpinning.” Hairpinning can be aproblem even for residues that have been on thesurface for a number of weeks if planting in themorning when residues are still moist from pre-cipitation or dew.Hairpinning can reduce seed tosoil contact and cash crop stands.

You can sometimes plant the cash crop directlyinto standing (live) cover crop, then kill the covercrop.This allows more time for cover crop growthand biomass production, and usually side-steps theproblem of planting into tough cover crop residue.However, planting into standing green residue canincrease the risk of allelopathic chemicals affectingsensitive cash crop seedlings,and can make it diffi-cult to align rows when planting.

Killing methodsMany kill methods have been developed and test-ed. Some are described below. Be sure to checkwith Extension or other farmers for recommend-ed methods for your area and crop system.Killing with an herbicide. Killing cover

crops with a non-selective herbicide is the stan-dard method used by conservation tillage grow-ers.They favor this option because they can covermany acres quickly and herbicides are relativelycheap. Herbicides can be applied at any time orgrowth stage to terminate the cover crop.Killing with a roller-crimper. Cover crops

can be killed using a mechanical roller (oftencalled a roller-crimper).The roller kills the covercrop by breaking (crimping) the stems. Thecrimping action aids in cover crop desiccation.

The cover crop is rolled down parallel to thedirection of planting to form a dense mat on thesoil surface, facilitating planter operation and aid-

ing in early season weed control.When using aroller alone for cover crop termination, bestresults are obtained when rolling is delayed untilflowering stage or later.

Roller-crimpers work best with tall-growing covercrops. Small weeds are not killed by rolling. Weedsuppression by the mat of rolled cover crop residuedepends on cover crop,weed species and height,andthe density (thickness) of the cover crop mat.

Rollers can be front- or rear-mounted.They usu-ally consist of a round drum with equally spacedblunt blades around the drum. Blunt blades areused to crimp the cover crop.This is preferable tosharp blades that would cut the cover crop anddislodge residue that might interfere with seedsoil contact at planting.

The roller-crimper is a viable way to kill covercrops without using herbicides. It also helps pre-vent planter problems that can occur when tall-growing cover crops lodge in many differentdirections after chemical termination

InAlabama, a mechanical roller was used to killblack oat, rye and wheat cover crops.The rollercombined with glyphosate at one-half the recom-mended rate was as effective as using glyphosateat the full recommended rate to kill all covercrops.The key was to use the roller at flowering.Herbicides can be eliminated if the roller opera-tion occurs at the soft dough stage or later,a goodoption for organic growers (13).

▼Precaution: Applying non-selective herbicidesat reduced rates could lead to weed resistance.The half rate of herbicide may not completelyeradicate the weed,increasing the chance that theweed will produce seed. Under these circum-stances, such seeds are more likely to be resistantto the herbicide. Therefore, it is safer to com-pletely eliminate the use of the non-selectiveherbicide with a roller or use the non-selectiveherbicide at the labeled rate,with or without theroller.

Growers and researchers are addressing severalbarriers to the use of rollers:• Operation speed was hampered by vibration.

Using curved blades on the roller drum allevi-ates this problem.


• Most rollers are 8 rows or smaller, but growershave built wider rollers that can be folded fortransportation.

• Rolling and planting can be done in one oper-ation by using a front-mounted roller and rear-mounted drill, saving time and energy.

For more information about cover crop rollers,see ATTRA (11) and Cover Crop Roller DesignHolds Promise for No-Tillers, p. 146.Mowing/chopping. Mowing and chopping

are quick methods to manage large amounts ofcover crop residue by cutting it into smallerpieces.An alternative to the use of herbicides, it ismore energy intensive.

In humid climates, mowed residues breakdown faster,negating some of the residue benefitsof conservation tillage. In drier climates, covercrop residues do not decompose as fast,but windand water may cause residue to accumulate inlow areas or remove it from the field altogether.

Cutting residue into smaller pieces mayadversely affect the performance of tillage andplanting equipment because coulters designed tocut through residue may instead push smallresidue pieces into the soil.Use“row cleaners”or“trash whippers” to prevent this problem.Living mulch. Living mulches are cover crops

that co-exist with the cash crop during the grow-ing season and continue to grow after the crop isharvested. Living mulches do not need to bereseeded each year (182). They can be chosenand managed to minimize competition with themain cash crop yet maximize competition withweeds. The living mulch can be an annual orperennial plant established each year, or it can bean existing perennial grass or legume stand intowhich a crop is planted.

Living mulch systems are dependent on adequatemoisture for the cash crop.They can be viable forvineyards, orchards, agronomic crops, such as corn,soybean, and small grains, and many vegetables.Legumes are often used because they fix nitrogen,aportion of which will be available for the compan-ion crop. If excess nitrogen is a problem, livingmulches (especially grasses) can serve as a sink to tieup some of this excess nitrogen and hold it until thenext growing season.

In conservation tillage systems,livingmulches canimprove nitrogen budgets, provide weed and ero-sion control, and may contribute to pest manage-ment and help mitigate environmental problems.

Living mulch systems are feasible in Midwestalfalfa-corn rotations (386). Use in corn-soybeanrotations was also feasible but more challengingbecause soybean is more susceptible to competi-tion from the living mulch. With adequate sup-pression, living mulches can be managed tominimize competition with corn with little or noreduction in yield.The system requires close mon-itoring and careful control of competitionbetween the living mulch and grain crop to main-tain crop yields.Cash crop establishment. Cash crop estab-

lishment can be complicated by the use of covercrops in conservation-tillage systems.Cover cropscan reduce cotton,corn and soybean stands if notmanaged well.Possible causes of stand reductionsinclude:• poor seed-soil contact due to residue interfer-

ence with planter operations• soil water depletion• wet soils due to residue cover• cold soils due to residue cover• allelopathic effects of cover crop residues• increased levels of soilborne pathogens• increased predation by insects and other pests• free ammonia (in the case of legume covers)

To prevent stand problems following cover crops:• Check for good seed-soil contact and seed

placement, particularly seeding depth.• Be sure that coulters are cutting through

cover crop residue rather than pushing it intothe soil along with the seed.

• Desiccate the cover crop at least 2 to 3 weeksbefore planting the cash crop.

• Monitor the emerging crop for early seasoninsect problems such as cutworms.

Small seeded crops like vegetables and cotton areespecially susceptible to stand reductions follow-ing cover crops.Winter annual legumes may causemore problems due to allelopathic effects and/orincreased populations of plant pathogens.


Residue management systems that leave covercrop residue on the surface can reduce the risk ofstand problems provided the residue does notinterfere with planter operation.

Good seed placement is more challengingwhere residues remain on the soil surface.However, improvements in no-till planter designhave helped. Equipment that removes cropresidue from the immediate seeding area can helpto reduce stand losses (see equipment discussion,below).

Surface residues reduce soil temperature. Therelative influence of this temperature reductionon crop growth is greater in northern areas of acrop’s adapted zone.Removal of residue from thezone of seed placement will increase soil temper-ature in the seed zone and also decrease theamount of residue that comes in contact with theseed. This will result in better seed-soil contactand less allelopathic effects from residue to thedeveloping seedling.No-till planters. The key to successful no-till

cash crop establishment in cover crop residues isadequate seed to soil contact at a desired seedingdepth. No-till planters are heavier than conven-tional planters.The additional weight allows theplanter to maintain desired seeding depth inrough soil conditions and prevents the planterfrom floating across the soil surface and creatinguneven seed placement. Individual planter rowunits are typically equipped with heavy-dutydown-pressure springs that allow the operator toapply down pressure in uneven soil conditions tomaintain depth control.

Row cleaners are designed to operate in heavycover crop residue. Manufacturers have devel-oped different types of row cleaners that can bematched to various planters.All row cleaners aredesigned to sweep residue away from the open-ing disks of the planter units. Removing thisresidue reduces the chance of pushing residueinto the seed furrow (hairpinning).

All row cleaners can be adjusted to match spe-cific field conditions. Row cleaners should beadjusted to move residue but not soil. If too muchsoil is disturbed in the row, the soil will dry outand can crust over,which will hinder emergence.In addition, disturbed soil can promote weed

emergence in the row creating unnecessary com-petition between weeds and the cash crop.

Spoked closing wheels improve establishmentin poorly drained or fine-textured soils. On thesesoils, traditional cast-iron or smooth rubber clos-ing wheels can result in soil crusting.Spoked clos-ing wheels crumble the seed trench closed foradequate seed to soil contact, but leave the soilloose and friable for plant emergence.

Additional planter attachments to ensure ade-quate seed to soil contact in rough soil conditionsinclude V-slice inserts and seed firmers. V-sliceinserts clean the seed trench created by the open-ing disks. Seed firmers press the seed into the soilat the bottom of the seed trench.Strip-tillage equipment. Strip-tillage equip-

ment is designed to manage residue and performsome non-inversion tillage in the row. In theSouth, strip-tillage refers to in-row subsoiling (14-16 inches deep) to reduce compaction,with min-imal disturbance of residue on the soil surface. Inthe Midwest, zone-tillage typically refers to shal-low tillage within the row designed to removeresidue and enhance soil warming in the seedzone.

Regardless of manufacturer, strip tillage imple-ments typically consist of a coulter that runsahead of a shank,followed by such attachments asadditional coulters, rolling baskets, drag chains, orpress wheels. Depending on conditions, theseattachments are used alone or in various combi-nations to achieve different degrees of tillage.

When strip-tilling in cover crop residue, thecoulter should be positioned as far forward of theshank as possible and centered on the shank.Thisallows the coulter to operate in firm soil enablingit to cut residue ahead of the shank.By cutting theresidue ahead of the shank, the residue can flowthrough the shanks more easily and not wrap upor drag behind the implement.

Fine-textured soils sometimes stick to theshank and may accumulate there, disturbing toomuch soil and making the slit too wide.This canimpede planter operations and is referred to as“blowout.” Plastic shields that fit over the shankhelp prevent blowout. Another way to reduceblowout is to install splitter points on the subsoilshanks. The splitter points look like shark fins


that attach vertically upright to the tips of theshank points.They fracture the soil at the bottomof the trench, preventing soil upheaval to the soilsurface.The soil fracture created is analogous tostress cracks in concrete.

Row cleaners can be used on cool, poorlydrained soils to enable faster soil-warming inspring.This may allow earlier planting and helpsensure optimal plant emergence conditions.Available for most strip-tillage implements, rowcleaners function much like row cleaners forplanters, sweeping cover crop residue away fromthe row. Adjustments for strip tillage row cleanersare not as flexible as those on planters.Vegetable establishment. Adoption of no-

tillage systems for transplanted vegetable cropswas limited by equipment and stand establish-ment problems. This problem was overcome inthe 1990’s with the development of the Subsur-face Tiller-Transplanter (287). The SST-T is a“hybrid,” combining subsurface soil loosening toalleviate soil compaction and effective setting oftransplants, in one operation with minimumdisturbance of surface residues or surface soil.

The spring-loaded soil-loosening component ofthe subsurface tiller tills a narrow strip of soilahead of the double disk shoe of the transplanter.The double-disk shoe moves through the residueand the tilled strip with relatively little resistance.In addition, the planter can be equipped with fer-tilizer and pesticide applicators to reduce thenumber of trips required for a planting operation.

Regional Roundup: Cover Crop Usein Conservation Tillage Systems

Midwest—Tom KasparSoils. Soils of the Midwest contain high levels oforganic matter compared to other regions.Research has yet to confirm if cover crops canincrease soil organic matter contents beyond cur-rent levels.The possibility of using corn stover as abioenergy source would leave the soil unprotectedand much more vulnerable to degradation, butcover crops could offset any detrimental effectsassociated with corn stover removal. The degreeto which cover crops could protect the soil follow-ing corn stover removal has not been investigated.

Farm systems. Midwest farms are large, aver-aging 350 acres. Cover crops and conservationtillage are most common in corn and soybean sys-tems, with or without livestock. Cover crops arealso commonly used in vegetable systems.Cover crop species. Rye and other small

grains are the primary cover crops used in theMidwest. Legume cover crop include red clover,hairy vetch and sweetclovers.Cover crop benefits. Advantages of cover

crops in the Midwest include reducing erosion,anchoring residues in no-till systems, suppressingwinter annual weeds and nutrient management.The ability of cover crops to scavenge nitrates isparticularly beneficial in the Midwest, where themajority of United States corn is produced,because the high N requirement of corn increas-es the potential for nitrate loss.Drawbacks. Cover crops have reduced corn

(but not soybean) yields when they are terminat-ed at planting. Earlier termination helps reducethis problem, but residue benefits are reduced.The potential biomass production is complicatedby the already short,cold cover crop growing sea-son between harvest and planting of corn andsoybean crops. Cash crop planting and harvestcoincide with cover crop kill and planting dates.Management. Cover crops need to be planted

at the same time farmers are harvesting corn andsoybean to ensure adequate biomass production.Producers would benefit from alternative covercrop establishment methods, such as overseedingbefore harvest, seeding at weed cultivation withdelayed emergence, or frost seeding after harvest.Environmental payments or incentives may enticegrowers to try alternative practices.

Northeast—Sjoerd DuikerCover crops are becoming an integral part of cropproduction in the Northeast. This is due in largepart to the increasing adoption of no-tillage sys-tems, because cover crops can be managed moreeasily than with tillage, while cover crop residuesin no-till systems lead to multiple benefits.Soils. There are many soil types in the

Northeast, including soils developed in glacialdeposits or from melt water lakes; sedimentarysoils formed from the sedimentary rocks sand-


stone, shale and limestone; Piedmont soils, rem-nants of a coastal mountain range with complexgeology,characterized by a gently to strongly undu-lating landscape;and coastal plain soils,developedin unconsolidated material deposited by rivers andthe ocean,often sandy with a shallow water table.

Soil and nutrient management in the region aimto address soil erosion, clay subsoils, fragipans,shallow water tables and the nutrient enrichmentcaused by the high density of animal production.Farm systems. Farms in the Northeast are

diverse, tend to be small, and include cash grain,perennial forage, dairy, hog, poultry, fruit and veg-etable operations. Nutrient management regula-tions in some states encourage the use of covercrops and conservation tillage practices, particu-larly for the application of manure. Farmer orga-nizations such as the Pennsylvania No-TillAllianceactively promote cover crops for their soil-improving benefits, while government programssuch as the 2006 Maryland cover crop subsidy of$30-$50 per acre led to a dramatic increase incover crop acreage.Cover crop species. Cover crop options and

niches are as diverse as the farming systems in theregion.Rye,wheat, oats and ryegrass are the mostcommon grass cover crops; hairy vetch, crimsonclover and Austrian winter pea are importantlegumes; buckwheat finds a place in many veg-etable systems and brassica crops such as forageradish are increasingly being tested and used inthe region.Cover crop benefits. Cover crops are planted

for erosion control, soil improvement, moistureconservation, forage and nutrient management,particularly the nitrogen and phosphorus fromintensive animal agriculture. Cover crops can fitinto many different niches in the region, particu-larly fruit and vegetable systems (1,2,3,4).Recentwork with forage radish (Raphanus sativus L.)suggests that its large taproot can penetrate deepsoil layers and alleviate compaction (446).Drawbacks. Barriers to the adoption of cover

crops include the time and cost of establishmentand management, water use, and, for some sys-tems, the length of the growing season.Management. Farmers and other researchers

fit cover crops into many different niches using:

• timely seeding, overseeding into standingcrops, or interseeding, including some use ofliving mulches

• various termination methods, including mow-ing or rolling standing cover crops

• manipulation of cover crop kill and cash cropplanting dates to maximize cover crop benefits

Southeast—Kipling BalkcomHigh-residue cover crops are essential to the suc-cess of conservation systems in the Southeast.Soils. Soils in the Southeast are highly weath-

ered, acidic, and often susceptible to erosion dueto their low organic matter content. Decades ofconventional tillage practices have exacerbatedtheir poor physical and chemical condition.Farm systems. Southeast farms raise various

combinations of cotton, soybeans, corn, peanutsand small grains. Some include livestock, haveaccess to irrigation or raise fruit and vegetables.Cover crop species. Rye, wheat, oats, hairy

vetch and crimson clover are the cover cropmainstays for grain and oil crop systems.Cover crop benefits. Cover crop biomass is

needed on the weathered soils of the Southeast toadd organic matter and improve soil physical,chemical, and biological properties. Cover cropresidues reduce soil erosion and runoff, increaseinfiltration and conserve soil moisture, particularlybeneficial in dry years or on drought-prone soils.Drawbacks. Major concerns are:

• water management• integration of different cover crop species into

southeastern crop production• reduced effectiveness of pre-emergence herbi-

cides in high-residue systems

Producers are also concerned about residue inter-ference with efficient equipment operation, ade-quate soil moisture at planting, and standestablishment problems. In addition, some are notwilling to commit to the additional managementlevel or perceived costs.Management. Producers like the idea of

reducing trips across the field,which reduces fueland labor costs and saves time.Significant increas-es in the use of cover crops and conservationtillage systems in the Southeast have paralleled


the adoption of new genetic varieties of corn,soy-bean and cotton that are herbicide resistant orhave incorporated genes for improved insectresistance.These genetic changes reduced someof the challenges associated with weed and insectmanagement,making the conservation tillage sys-tems easier to manage.The relatively longer grow-ing season usually allows ample time to plantcover crops after cash crops.

Northern Plains—Jorge DelgadoRainfall and moisture availability are the major fac-tors affecting the use of cover crops in conserva-tion tillage systems.Soils. Soils of the Northern Great Plains are

exposed to high wind conditions with enoughforce to move soil particles off site in minimumtillage conditions where soil cover is low. Cropsystems do not, in general, leave substantialresidue on the soil surface, due in part to lowannual rainfall in non-irrigated systems.Farm systems. Farms in the Northern Plains

tend to be large and can be divided into irrigatedand non-irrigated systems.Crops rotations includepotato, safflower, dry bean, sunflower, canola,crambe, flax, soybean, dry pea,wheat and barley.Cover crop species. Rye, field pea (Austrian

winter pea, trapper spring pea), sweetclover andsorghum-sudangrass are commonly grown.Cover crop benefits. Cover crop residues

improve water retention, helping to increase soilwater content and yields. Cover crops reduce winderosion and nutrient loss, and increase soil carbon.High crop residue and winter cover crops alsosequester carbon and nitrogen and increase the avail-ability of other macro- and micronutrients (7,113).Drawbacks. Rainfall amount, the availability of

irrigation and water use by cover crops are criti-cal considerations for the region.Cool,wet springweather is exacerbated by cover crop residuesthat delay soil-warming. Cover crops and conser-vation tillage often reduce cash crop yields, evenin irrigated systems (171, 172).Management. Management is key to increas-

ing nutrient use efficiencies and reduce nutrientlosses to the environment (112, 113, 114, 371).Management is also the key to increasing wateruse efficiency.

Southern Plains —Louis BaumhardtConservation tillage was first introduced for soilerosion control on the Great Plains. It followedinversion tillage that incorporated crop residueand degraded the soil’s natural cohesiveness andaggregation. Combined with the 1930’s dry andwindy conditions, this intensive tillage producedcatastrophic wind erosion known historically asthe “Dust Bowl” (26). Use of conservation tillagepractices for much of the Southern Great Plainsseems to lag behind other regions, but may beunderestimated, in part, because insufficientresidue is produced in dryland areas to qualify asconservation tillage acres.Soils. Soils of the Southern Great Plains were

formed from a range of materials including, forexample, an almost flat aeolian mantle in thenorth (Texas High Plains and western Kansas) andreworked Permian sediments of theTexas RollingPlains extending towards western Oklahoma.These soils have varied mineralogy, are frequentlycalcareous, and generally have poor structure andlow organic matter content (37). All SouthernGreat Plains soils are managed for wind erosioncontrol and water conservation.Farm systems. Farm systems on the Southern

Great Plains vary with irrigation.They are largerand more diverse as irrigation declines to distrib-ute risk and meet production requirements.Principal crops include cotton,corn,peanut,grainsorghum, soybean, and sunflower. Grain and for-age crops support the regional cattle industry.

Wheat-sorghum-fallow is a common rotationand permits cattle grazing on wheat forage andsorghum stubble (27). This and similar rotationsmay include additional years of sorghum or awheat green fallow before cotton.Cover crop species. Water governs cover

crop species selection, but wheat, rye, and oatsare most common.Wheat is commonly grown forgrain or forage and as a green fallow cropbetween annual cotton crops (29).Cover crop benefits. Cover crop residue

helps meet the 30% cover requirement for con-servation tillage, helps control wind erosion inlow residue crops, and provides other water infil-tration and storage benefits.


Drawbacks. Cover crop use in the regiondepends on precipitation or the availability andeconomy of irrigation to produce residue. Somecrops such as cotton produce insufficient residuefor soil cover, but establishing cover crops com-petes for water needed by the subsequent cottoncrop (28). Grazing crop residues and cover cropsalso limits the amount of crop residue left on thesoil surface and must be balanced against thevalue of the forage.Management. Southern Great Plains produc-

ers often use cover crops to control wind erosionin annual crops like cotton that produce insuffi-cient cover to protect the soil. During years withlimited precipitation, cover crops compete forwater resources needed to establish primary cashcrops (28). Nevertheless, producers wishing togrow cotton on soils subject to wind erosion havesuccessfully introduced residue producing wintercereal crops with minimum irrigation input.

Conservation tillage increases storage of pre-cipitation in the soil through increased infiltrationand reduced evaporation. This additional watersupplements growing season precipitation andirrigation to meet crop water needs on the semi-arid Southern Great Plains.

Pacific Northwest —Hal CollinsUnder dryland conservation tillage systems in thePacific Northwest (PNW), winter precipitationand limited water availability are major factorsaffecting the use of cover crops.With irrigation,heavy crop residues from previous grain cropscan negatively impact cover crop stand establish-ment. Annual precipitation in agricultural regionsof the PNW ranges from 15 to 76 cm, due to oro-graphic effects of the Cascade and Blue MountainRanges that strongly influence total precipitationand distribution patterns in Washington, Oregonand Idaho.Soils. Soils of the PNW have developed from

aeolian and flood deposits originating from vol-canic activity and the last continental glaciations(~12,000 years BP) under shrub-steppe vegeta-tion. Soils that developed on wind blown loessaldeposits are typically silt loams with moderate tostrong structure and soil organic C contents rang-

ing from 1-2%. Soils developing on the flooddeposits of Glacial Lakes’Missoula and Bonnevillein the Columbia Basin ofWashington,Oregon andIdaho are predominately sands to silt loams withweak soil structure and low soil organic C (<1%).Cultivated soils of the region are exposed tosevere soil erosion from water and snow melt inthe higher precipitation zones and due to highwind conditions in low rainfall areas (ColumbiaBasin).Farm systems. Farms in the dryland and irri-

gated regions of the PNW tend to be large(2,000+ acres on average). Dryland regions arecommonly cropped to wheat, barely, canola, oats,grass seed and dry peas. Crop rotations under irri-gation are diverse, vegetable based rotations thatinclude potato, onion, carrots, field corn, sweetcorn, fresh beans and peas, sugar beets, mint,canola, mustards, safflower, dry pea, grass seed,alfalfa,wheat and barley.Cover crop species. Field pea (Austrian

winter pea), sweetclover, hairy vetch, sudangrass,small grains (wheat, triticale) and a variety ofbrassica species are used in the region.Cover crop benefits. Cover crop residues

improve water retention, infiltration and storage,soil structure, soil carbon reserves, microbialactivity and crop yields.Cover crop residues havebeen shown to reduce water and wind erosionand nutrient loss from leaching and overland flowof sediments. High crop residues and the use ofwinter cover crops under irrigation sequester car-bon and nitrogen and increase the availability ofother macro and micronutrients. Cover cropresidues can meet or exceed the 30% coverrequirement for conservation tillage in low rain-fed areas.Drawbacks. Rainfall amount and distribution,

the availability of irrigation and water use by covercrops are critical considerations for the drylandregions. Heavy residues under irrigation inhibitstand establishment.Cool,wet spring weather exac-erbated by cover crop residues delay soil warmingand seedling emergence of cash crops. Absenteeland owners combined with the diversity of crop-ping under irrigation of high value vegetable crop-ping has limited adoption of conservation tillage


and cover crop use. Cover crops and conservationtillage can reduce economic benefits and cropyields under some situations.Management. Management of cover crops is

complex and differs in dryland and irrigated sys-tems. Cover crops are managed to reduce nutri-ent losses, increase nutrient use efficiencies andreduce severity of soil pathogens (88, 111, 115,430).Management is also key to increasing wateruse efficiency and can affect protein content ofsmall grains.

California —Jeffrey MitchellDespite the many benefits of cover cropping andconservation tillage, adoption by row crop pro-ducers in California has been limited.Cover cropsare used on less than 5% of California’s annualcrop acreage and conservation tillage practicesare used on less than 2% of annual cropland.Soils. A wide range of soil types are used for

agricultural production in California. Cover cropsand conservation tillage are used predominantlyon finer-textured clay loams or loam soils. Morerecently, conservation tillage is increasingly usedin dairy forage production systems on coarser soiltypes.Farm systems. Most cover crop use in con-

servation tillage systems in California has been forprocessing and fresh market commercial tomatoproduction systems (187). Research is underwayevaluating cover crops in CT corn and cotton sys-tems (281).Cover crop species. In tomato systems, the

most successful and manageable cover crops aremixtures of triticale, rye and pea.Vetches are usedfor field corn.Cover crop benefits. California farmers use

cover crops to reduce intercrop tillage, suppresswinter weeds, reduce pathogen buildup and man-age nutrients.Drawbacks. Producers are most concerned

about cooler temperatures above and belowmulch, slower maturing crops, cover cropregrowth and specialized management required.In-season weed management options may be lim-ited in conservation tillage systems.Management. Cover crops are normally

grown from mid-October to mid-March in

California’s Central Valley. Aboveground biomassproduction can reach 11,000 lb. of abovegrounddry matter/A without irrigation (279, 280).The cover crops are mowed or chopped inMarch using ground-driven stalk choppers, ormerely allowed to collapse following herbicideapplication.

Tomatoes can be no-till transplanted directlyinto the mulch or transplanted following a strip-till pass using either narrow PTO-driven rotarymulchers or ground-driven strip-till implementsmodified for tomato beds (250). Because of inad-equate weed control by the cover crop mulchitself,high residue cultivators that effectively slicethrough residues while cultivating weeds are nec-essary for in-season weed control.

Field corn has also been successfully directseeded into flail mowed vetch cover crops in theSacramento Valley. Corn yield is similar to “greenmanure”systems in which winter cover crops areincorporated.

SUMMARY AND RECOMMENDATIONS

Cover crops benefit conservation tillage systemsby:• decreasing soil erosion• providing crop residues to increase soil

organic matter• improving soil structure and increasing

infiltration• increasing availability of water for crop

production• improving soil quality• aiding in early season weed control• breaking disease cycles

To enhance the beneficial effects of cover crops:• Plant in a timely fashion.• Consider additional N fertilizer for small grain

covers only if residual N is low.• Terminate covers 2-3 weeks ahead of antici-

pated planting date to allow soil moisturerecharge and reduce problems associated withallelopathy, pests, and planter operation.

• Take advantage of equipment modificationsdesigned for tillage and/or planter operationsin heavy residue.


The four comprehensive charts that followcan help orient you to the major covercrops most appropriate to your needs and

region.Bear in mind that choice of cultivar,weath-er extremes and other factors may affect a covercrop’s performance in a given year.

CHART 1: TOP REGIONAL COVERCROP SPECIES

This chart lists up to five cover crop recommen-dations per broad bioregion for six differentmajor purposes: N Source, Soil Builder, ErosionFighter, Subsoil Loosener,Weed Fighter and PestFighter. If you know your main goal for a covercrop, Chart 1 can suggest which cover cropentries to examine in the charts that follow andhelp you determine which major cover narra-tive(s) to read first.Disclaimer. The crops recommended here

will not be the most successful in all cases withina bioregion, and others may work better in somelocations and in some years. The listed covercrops are, however, thought by reviewers to havethe best chance of success in most years undercurrent management regimes.

CHART 2: PERFORMANCE AND ROLES

This chart provides relative ratings (with theexception of two columns having quantitativeranges) of what the top covers do best, such assupply or scavenge nitrogen, build soil or fighterosion.

Seasonality has a bearing on some of these rat-ings. A cover that grows best in spring could sup-press weeds better than in fall. Unless otherwisefootnoted,however,the chart would rate a cover’sperformance (relative to the other covers) for theentire time period it is likely to be in the field.Ratings are general for the species, based on mea-sured results and observations over a range ofconditions. The individual narratives provide

more seasonal details.The added effect of a nursecrop is included in the “Weed Fighter” ratings forlegumes usually planted with a grain or grassnurse crop.

Column headingsLegume N Source. Rates legume cover crops fortheir relative ability to supply fixed N.(Nonlegumes have not been rated for their bio-mass nitrogen content,so this column is left blankfor nonlegumes.)

Total N. A quantitative estimate of the reason-ably expected range of total N provided by alegume stand (from all biomass,above- and belowground) in lb. N/A, based mostly on publishedresearch.This is total N, not the fertilizer replace-ment value.Grasses have not been rated for theirbiomass nitrogen content because mature grassresidues tend to immobilize N. Brassicas are lesslikely to immobilize N than grasses.

Dry Matter.A quantitative estimate of the rangeof dry matter in lb./A/yr., based largely on pub-lished research.As some of this data is based onresearch plots, irrigated systems or multicut sys-tems, your on-farm result probably would be inthe low to midpoint of the dry matter range cited.This estimate is based on fully dry material.“Dry”alfalfa hay is often about 20 percent moisture, so aton of hay would only be 1,600 lb. of“dry matter.”

N Scavenger. Rates a cover crop’s ability to takeup and store excess nitrogen. Bear in mind thatthe sooner you plant a cover after main crop har-vest—or overseed a cover into the standingcrop—the more N it will be able to absorb.

Soil Builder. Rates a cover crop’s ability to pro-duce organic matter and improve soil structure.The ratings assume that you plan to use covercrops regularly in your cropping system to pro-vide ongoing additions to soil organic matter.

INTRODUCTION TO CHARTS

CHARTS 63

Erosion Fighter. Rates how extensive and howquickly a root system develops, how well it holdssoil against sheet and wind erosion and the influ-ence the growth habit may have on fighting winderosion.

Weed Fighter. Rates how well the cover cropoutcompetes weeds by any means through its lifecycle, including killed residue. Note that ratingsfor the legumes assume they are established witha small-grain nurse crop.

Good Grazing. Rates relative production, nutrit-ional quality and palatability of the cover as a for-age.

Quick Growth. Rates the speed of establishmentand growth.

Lasting Residue. Rates the effectiveness of thecover crop in providing a long-lasting mulch.

Duration. Rates how well the stand can providelong-season growth.

Harvest Value. Rates the cover crop’s economicvalue as a forage (F) or as a seed or grain crop (S),bearing in mind the relative market value andprobable yields.

Cash Crop Interseed. Rates whether the covercrop would hinder or help while serving as acompanion crop.

CHART 3A: CULTURAL TRAITS

This chart shows a cover crop’s characteristicssuch as life cycle, drought tolerance, preferredsoils and growth habits.The ratings are general forthe species,based on measured results and obser-vations over a range of conditions. Choice of cul-tivar, weather extremes and other factors mayaffect a cover crop’s performance in a given year.

Column headingsAliases. Provides a few common names for thecover crop.

Type. Describes the general life cycle of the crop.

B = Biennial. Grows vegetatively during its firstyear and, if it successfully overwinters, sets seedduring its second year.

CSA = Cool-Season Annual. Prefers cool tem-peratures and depending on which HardinessZone it is grown in,could serve as a fall,winter orspring cover crop.

SA = Summer Annual. Germinates and matureswithout a cold snap and usually tolerates warmtemperatures.

WA = Winter Annual. Cold-tolerant, usuallyplanted in fall and often requires freezing temper-atures or a cold period to set seed.

LP = Long-lived Perennial. Can endure formany growing seasons.

SP = Short-lived Perennial. Usually does notpersist more than a few years, if that long.

Hardy Through Zone. Refers to the standardUSDA Hardiness Zones. See map on inside frontcover. Bear in mind that regional microclimate,weather variations, and other near-term manage-ment factors such as planting date and compan-ion species can influence plant performanceexpectations.

Tolerances. How well a crop is likely to enduredespite stress from heat, drought, shade, floodingor low fertility.The best rating would mean thatthe crop is expected to be fully tolerant.

Habit. How plants develop.C = ClimbingU = UprightP = ProstrateSP = Semi-ProstrateSU = Semi-Upright

pH Preferred. The pH range in which a speciescan be expected to perform reasonably well.


Best Established. The season in which a covercrop is best suited for planting and early growth.Note that this can vary by region and that it’simportant to ascertain local planting date rec-ommendations for specific cover crops.Season: F = Fall ; Sp = Spring; Su = Summer;

W =WinterTime: E = Early; L = Late;M = Mid

Minimum Germination Temperature. Theminimum soil temperature (F) generally requiredfor successful germination and establishment.

CHART 3B: PLANTING

Depth. The recommended range of seedingdepth (in inches), to avoid either overexposure orburying too deeply.

Rate. Recommended seeding rate for drilling andbroadcasting a pure stand in lb./A, bu/A. andoz./100 sq. ft., assuming legal standards for germi-nation percentage. Seeding rate will depend onthe cover crop’s primary purpose and other fac-tors. See the narratives for more detail aboutestablishing a given cover crop. Pre-inoculated(“rhizo-coated”) legume seed weighs about one-third more than raw seed. Increase seeding rateby one-third to plant the same amount of seed perarea.

Cost.Material costs (seed cost only) in dollars perpound, based usually on a 50-lb. bag as of fall2006. Individual species vary markedly with sup-ply and demand.Always confirm seed price andavailability before ordering, and before planningto use less common seed types.

Cost/A. Seed cost per acre based on the midpointbetween the high and low of reported seed pricesas of fall 1997 and the midpoint recommendedseeding rate for drilling and broadcasting. Yourcost will depend on actual seed cost and seedingrate. Estimate excludes associated costs such aslabor, fuel and equipment.

Inoculant Type. The recommended inoculantfor each legume. Your seed supplier may onlycarry one or two common inoculants. You mayneed to order inoculant in advance. See SeedSuppliers, p. 195.

Reseeds. Rates the likelihood of a cover crop re-establishing through self-reseeding if it’s allowedto mature and set seed.Aggressive tillage will buryseed and reduce germination. Ratings assume thetillage system has minimal effect on reseeding.Dependable reseeding ability is valued in someorchard, dryland grain and cotton systems, butcan cause weed problems in other systems. Seethe narratives for more detail.

CHARTS 4A AND 4B

These charts provide relative ratings of othermanagement considerations—benefits and possi-ble drawbacks—that could affect your selectionof cover crop species.

The till-kill rating assumes tillage at an appro-priate stage.The mow-kill ratings assume mowingat flowering,but before seedheads start maturing.See sectional narratives for details.

Ratings are based largely on a combination ofpublished research and observations of farmerswho have grown specific covers.Your experiencewith a given cover could be influenced by site-specific factors, such as your soil condition, croprotation, proximity to other farms, weatherextremes, etc.

CHART 4A: POTENTIAL ADVANTAGES

Soil Impact. Assesses a cover’s relative ability toloosen subsoil, make soil P and K more readilyavailable to crops, or improve topsoil.

Soil Ecology. Rates a cover’s ability to fight pestsby suppressing or limiting damage from nema-todes, soil disease from fungal or bacterial infec-tion, or weeds by natural herbicidal (allelopathic)or competition/smothering action. Researchers

CHARTS 65

rarely causes pest problems, but certain covercrops may contribute to particular pest,disease ornematode problems in localized areas, for exam-ple by serving as an alternate host to the pest. Seethe narratives for more detail.

▼ Readers note the shift in meaning for symbolson this chart only.

Management Challenges. Relative ease or diffi-culty of establishing, killing or incorporating astand.“Till-kill”refers to killing by plowing,diskingor other tillage. “Mature incorporation” rates thedifficulty of incorporating a relatively maturestand.Incorporation will be easier when a stand iskilled before maturity or after some time elapsesbetween killing and incorporating.

report difficulty in conclusively documentingallelopathic activity distinct from other covercrop effects, and nematicidal impacts are variable,studies show.These are general, tentative ratingsin these emerging aspects of cover crop influ-ence.

Other. Indicates likelihood of attracting benefi-cial insects,of accommodating field traffic (foot orvehicle) and of fitting growing windows or shortduration.

CHART 4B: POTENTIALDISADVANTAGES

Increase Pest Risks. Relative likelihood of acover crop becoming a weed,or contributing to alikely pest risk. Overall, growing a cover crop


Northeast red cl,hairy v, ryegrs, swt cl, rye, ryegrs, sorghyb, sorghyb, rye,berseem, sorghyb, sub cl, swt cl, ryegrs, rye, sorghyb,swt cl rye oats forad buckwheat rape

Mid-Atlantic hairy v, red cl, ryegrs, rye, sub cl, sorghyb, rye, ryegrs, rye,berseem, swt cl, cowpeas, swt cl, oats, sorghyb,crim cl sorghyb rye, ryegrs forad buckwheat rape

Mid-South hairy v, sub cl, ryegrs, rye, sub cl, sorghyb, buckwheat, rye,berseem, sub cl, cowpeas, swt cl ryegrs, sub cl, sorghybcrim cl sorghyb rye, ryegrs rye

Southeast Uplands hairy v, red cl, ryegrs, rye, sub cl, sorghyb, buckwheat, rye,berseem, sorghyb, cowpeas, rye, swt cl ryegrs, sub cl, sorghybcrim cl swt cl ryegrs rye

Southeast Lowlands winter peas, ryegrs, sub cl, sorghyb berseem, rye, rye,sub cl,hairy v, rye, cowpeas, wheat, sorghyb

berseem, sorghyb, rye, ryegrs, cowpeas,crim cl sub cl sorghyb oats, ryegrs

Great Lakes hairy v, red cl, ryegrs, rye, oats, sorghyb, berseem, rye,berseem, sorghyb, rye, swt cl, ryegrs, rye, sorghyb,crim cl ryegrs, swt cl ryegrs forad buckwht,oats rape

Midwest Corn Belt hairy v, red cl, rye,barley, wht cl, rye, sorghyb, rye, ryegrs, rye,berseem, sorghyb, ryegrs, swt cl, wheat, sorghybcrim cl swt cl barley forad buckwht,oats

Northern Plains hairy v, swt cl, rye,barley, rye, sorghyb, medic, rye, rye,medics medic, swt cl barley swt cl barley sorghyb

Southern Plains winter peas, rye,barley, rye, sorghyb, rye, rye,medic,hairy v medic barley swt cl barley sorghyb

Inland Northwest winter peas, medic, swt cl, rye, sorghyb, rye,wheat, rye,mustards,hairy v rye,barley barley swt cl barley sorghyb

Northwest Maritime berseem, ryegrs, rye, wht cl, rye, sorghyb, ryegrs, rye,sub cl, lana v, sorghyb, ryegrs, swt cl lana v,oats, mustards

crim cl lana v barley wht clCoastal California berseem, ryegrs, rye, wht cl, sorghyb, rye, ryegrs, sorghyb,

sub cl, sorghyb, cowpeas, swt cl berseem, crim cl,lana v,medic lana v rye, ryegrs wht cl rye

Calif. Central Valley winter peas, medic, wht cl, sorghyb, ryegrs, sorghyb,lana v, sub cl, sub cl barley, rye, swt cl wht cl, rye, crim cl,

medic ryegrs lana v ryeSouthwest medic, sub cl, barley, medic,

sub cl medic,barley sorghyb barley

Chart 1 TOP REGIONAL COVER CROP SPECIES1

Soil Erosion Subsoil Weed PestBioregion N Source Builder Fighter Loosener Fighter Fighter

1ryegrs=annual ryegrass. buckwht=buckwheat. forad=forage radish. rape=rapeseed. sorghyb=sorghum-sudangrass hybrid.berseem=berseem clover. winter peas=Austrian winter pea. crim cl=crimson clover. hairy v=hairy vetch. red cl=red clover.sub cl=subterranean clover. swt cl=sweetclover. wht cl=white clover. lana v=LANA woollypod vetch.

CHARTS 67

Chart 2 PERFORMANCE AND ROLES

Legume Total N Dry Matter N Soil Erosion Weed Good QuickSpecies N Source (lb./A)1 (lb./A/yr.) Scavenger2 Builder3 Fighter4 Fighter Grazing5 Growth

Annual ryegrass p. 74 2,000–9,000

Barley p. 77 2,000–10,000

Oats p. 93 2,000–10,000

Rye p. 98 3,000–10,000

Wheat p. 111 3,000–8,000

Buckwheat p. 90 2,000–4,000

Sorghum–sudan.p. 106 8,000–10,000

Mustards p.81 30–120 3,000–9,000

Radish p. 81 50–200 4,000–7,000

Rapeseed p. 81 40–160 2,000–5,000

Berseem clover p. 118 75–220 6,000–10,000

Cowpeas p. 125 100–150 2,500–4,500

Crimson clover p. 130 70–130 3,500–5,500

Field peas p. 135 90–150 4,000–5,000

Hairy vetch p. 142 90–200 2,300–5,000

Medics p. 152 50–120 1,500–4,000

Red clover p. 159 70–150 2,000–5,000

Subterranean clovers p.164 75–200 3,000–8,500

Sweetclovers p. 171 90–170 3,000–5,000

White clover p. 179 80–200 2,000–6,000

Woollypod vetch p. 185 100–250 4,000–8,000

1Total N—Total N from all plant. Grasses not considered N source. 2N Scavenger—Ability to take up/store excess nitrogen.3Soil Builder—Organic matter yield and soil structure improvement. 4Erosion Fighter—Soil-holding ability of roots and total plant.5Good Grazing—Production, nutritional quality and palatability. Feeding pure legumes can cause bloat.

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=Poor; =Fair; =Good; =Very Good; =Excellent


1Lasting Residue—Rates how long the killed residue remains on the surface. 2Duration—Length of vegetative stage.3Harvest Value—Economic value as a forage (F) or as seed (S) or grain. 4Cash Crop Interseed—Rates how well the cover cropwill perform with an appropriate companion crop.

Chart 2 PERFORMANCE AND ROLES continued

Lasting Harvest Cash CropSpecies Residue1 Duration2 Value3 Interseed4 Comments

Annual ryegrass Heavy N and H20 user; cutting boostsdry matter significantly.

Barley Tolerates moderately alkaline conditions butdoes poorly in acid soil < pH 6.0.

Oats Prone to lodging in N-rich soil.

Rye Tolerates triazine herbicides.

Wheat Heavy N and H20 user in spring.

Buckwheat Summer smother crop; breaks down quickly.

Sorghum–sudangrass Mid-season cutting increases yield & root penetration.

Mustards Suppresses nematodes and weeds.

Radish Good N scavenging and weed control;N releasedrapidly.

Rapeseed Suppresses Rhizoctonia.

Berseem clover Very flexible cover crop, green manure, forage.

Cowpeas Season length, habit vary by cultivar.

Crimson clover Established easily, grows quickly if planted earlyin fall;matures early in spring.

Field peas Biomass breaks down quickly.

Hairy vetch Bi-culture with small grain expands seasonaladaptability.

Medics Use annual medics for interseeding.

Red clover Excellent forage, easily established;widely adapted.

Subterranean clover Strong seedlings, quick to nodulate.

Sweetclovers Tall stalks, deep roots in second year.

White clover Persistent after first year.

Woollypod vetch Reseeds poorly if mowed within 2 months ofseeddrop; overgrazing can be toxic.

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CHARTS 69

Chart 3A CULTURAL TRAITSHardy Tolerances Min.through pH Best Germin.

Species Aliases Type1 Zone2 Habit3 (Pref.) Established4 Temp.

heat

drought

shade

flood lowfert

Annual ryegrass p. 74 Italian ryegrass WA 6 U 6.0–7.0 ESp, LSu, 40FEF, F

Barley p. 77 WA 7 U 6.0–8.5 F,W, Sp 38F

Oats p. 93 spring oats CSA 8 U 4.5–7.5 LSu, ESp 38FW in 8+

Rye p. 98 winter, cereal, CSA 3 U 5.0–7.0 LSu, F 34For grain rye

Wheat p. 111 WA 4 U 6.0–7.5 LSu, F 38F

Buckwheat p. 90 SA NFT U/SU 5.0–7.0 Sp to LSu 50FSU

Sorghum–sudan.p. 106 Sudax SA NFT U 6.0–7.0 LSp, ES 65F

Mustards p.81 brown, oriental WA, 7 U 5.5–7.5 Sp, LSu 40Fwhite, yellow CSA

Radish p. 81 oilseed,Daikon, CSA 6 U 6.0–7.5 Sp, LSu, EF 45Fforage radish

Rapeseed p. 81 rape, canola WA 7 U 5.5–8 F, Sp 41F

Berseem clover p. 118 BIGBEE, SA,WA 7 U/SU 6.2–7.0 ESp, EF 42Fmulticut SU

Cowpeas p. 125 crowder peas, SA NFT SU/C 5.5–6.5 ESu 58Fsouthern peas

Crimson clover p. 130 WA, SA 7 U/SU 5.5–7.0 LSu/ESu

Field peas p. 135 winter peas, WA 7 C 6.0–7.0 F, ESp 41Fblack peas

Hairy vetch p. 142 winter vetch WA,CSA 4 C 5.5–7.5 EF, ESp 60F

Medics p. 152 SP, SA 4/7 P/Su 6.0–7.0 EF, ESp, ES 45F

Red clover p. 159 SP, B 4 U 6.2–7.0 LSu; ESp 41F

Subterranean cl.p. 164 subclover CSA 7 P/SP 5.5–7.0 LSu, EF 38F

Sweetclovers p. 171 B, SA 4 U 6.5–7.5 Sp/S 42F

White clover p. 179 white dutch LP,WA 4 P/SU 6.0–7.0 LW,E to 40Fladino LSp, EF

Woollypod vetch p. 185 Lana CSA 7 SP/C 6.0–8.0 F

1B=Biennial; CSA=Cool season annual; LP=Long-lived perennial; SA=Summer annual; SP=Short-lived perennial;WA=Winter annual2See USDA Hardiness Zone Map, inside front cover.NFT=Not frost tolerant. 3C=Climbing;U=Upright; P=Prostrate; SP=Semi-prostrate;SU=Semi-upright. 4E=Early;M=Mid; L=Late; F=Fall; Sp=Spring; Su=Summer;W=Winter

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Chart 3B PLANTING

Cost Cost/A Inoc.Species Depth Seeding Rate ($/lb.)1 (median)2 Type Reseeds3

Annual ryegrass 0–1/2 10–20 .4–.8 20–30 .8–1.25 1 .70–1.30 12 24 U

Barley 3/4–2 50–100 1–2 80–125 1.6–2.5 3-5 .17–.37 20 27 S

Oats 1/2–11/2 80–110 2.5–3.5 110–140 3.5–4.5 4–6 .13–.37 25 33 S

Rye 3/4–2 60–120 1-2 90–160 1.5–3.0 4–6 .18–.50 25 35 S

Wheat 1/2–11/2 60–120 1–2 60–150 1–2.5 3–6 .10–.30 18 22 S

Buckwheat 1/2–11/2 48–70 1–1.4 50–90 1.2–1.5 3–4 .30–.75 32 38 R

Sorghum-sudangrass 1/2–11/2 35 1 40–50 1–1.25 2 .40–1.00 26 34 S

Mustards 1/4–3/4 5–12 10–15 1 1.50–3.00 16 24 U

Radish 1/4–1/2 8–13 10–20 1 1.50–2.50 22 32 S

Rapeseed 1/4–3/4 5–10 8–14 1 1.00–2.00 11 16 S

Berseem clover 1/4–1/2 8–12 15–20 2 1.70– 22 39 crimson, N2.50 berseem

Cowpeas 1–11/2 30–90 70–120 5 .85– 71 113 cowpeas, S1.50 lespedeza

Crimson clover 1/4–1/2 15-20 22–30 2–3 1.25– 27 40 crimson, U2.00 berseem

Field peas 11/2–3 50–80 90–100 4 .61–1.20 50 75 pea, vetch S

Hairy vetch 1/2-11/2 15–20 25–40 2 1.70–2.50 35 65 pea, vetch S

Medics 1/4–1/2 8–22 12–26 2/3 2.50– 58 75 annual R4.00 medics

Red clover 1/4–1/2 8–10 10–12 3 1.40– 23 28 red cl, S3.30 wht cl

Subterranean clover 1/4–1/2 10–20 20–30 3 2.50– 45 75 clovers, U3.50 sub, rose

Sweetclovers 1/4–1.0 6–10 10–20 1.5 1.00– 16 32 alfalfa, U3.00 swt cl

White clover 1/4–1/2 3–9 5–14 1.5 1.10– 19 30 red cl, R4.00 wht cl

Woollypod vetch 1/2–1 10–30 30–60 2-3 1.25–1.60 30 65 pea, vetch S

Drilledlb./A bu/A lb./A bu/A

Broadcastoz./100 ft2 drilled broadcast

1Per pound in 50-lb. bags as of summer/fall 2006;To locate places to buy seed, see Seed Suppliers (p. 166).2Mid-point price at mid-point rate, seed cost only. 3R=Reliably;U=Usually;S=Sometimes;N=Never (reseeds).

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Annual ryegrass p. 74

Barley p. 77

Oats p. 93

Rye p. 98

Wheat p. 111

Buckwheat p. 90

Sorghum–sudangrass p. 106

Mustards p.81

Radish p. 81

Rapeseed p. 81

Berseem clover p. 118

Cowpeas p. 125

Crimson clover p. 130

Field peas p. 135

Hairy vetch p. 142

Medics p. 152

Red clover p. 159

Subterranean clover p. 164

Sweetclovers p. 171

White clover p. 179

Woollypod vetch p. 185

CHARTS 71

Chart 4A POTENTIAL ADVANTAGES


Soil Impact Soil Ecology Otherfree loosen choke attract bears short

Species subsoiler P&K topsoil nematodes disease allelopathic weeds beneficials traffic windows

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Chart 4B POTENTIAL DISADVANTAGESIncrease Pest Risks Management Challenges

Species Comments Pro/Con

Annual ryegrass If mowing, leave 3-4" to ensureregrowth.

Barley Can be harder than rye toincorporate when mature.

Oats Cleaned, bin-run seed will suffice.

Rye Can become a weed if tilled atwrong stage.

Wheat Absorbs N and H20 heavily duringstem growth, so kill before then.

Buckwheat Buckwheat sets seed quickly.

Sorghum–sudangrass Mature, frost-killed plants becomequite woody.

Mustards Great biofumigation potential;winterkills at 25° F.

Radish Winter kills at 25° F; cultivars varywidely.

Rapeseed Canola has less biotoxic activitythan rape.

Berseem clover Multiple cuttingsneeded to achieve maximum N.

Cowpeas Some cultivars, nematode resistant.

Crimson clover Good for underseeding, easy tokill by tillage or mowing.

Field peas Susceptible to sclerotinia in East.

Hairy vetch Tolerates low fertility,wide pHrange, cold or fluctuating winters.

Medics Perennials easily become weedy.

Red clover Grows best where corn grows well.

Subterranean clover Cultivars vary greatly.

Sweetclovers Hard seed possible problem; does nottolerate seeding year mowing

White clover Can be invasive; survives tillage.

Woollypod vetch Hard seed can be problematic;resident vegetation eventually displaces.

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1Note change in symbols, this page only: = problem. = Could be a moderate problem. = Could be a minor problem.

= Occasionally a minor problem. = not a problem

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Note change in symbols = problem = not a problem

OVERVIEW OF NONLEGUME COVER CROPS 73

Commonly used nonlegume cover crops include:• Annual cereals (rye,wheat, barley, oats)• Annual or perennial forage grasses such asryegrass

• Warm-season grasses like sorghum-sudangrass• Brassicas and mustards

Nonlegume cover crops are most useful for:• Scavenging nutrients—especially N—left overfrom a previous crop

• Reducing or preventing erosion• Producing large amounts of residue andadding organic matter to the soil

• Suppressing weeds

Annual cereal grain crops have been used suc-cessfully in many different climates and croppingsystems.Winter annuals usually are seeded in latesummer or fall, establish and produce good rootand topgrowth biomass before going dormantduring the winter, then green up and produce sig-nificant biomass before maturing.Rye,wheat, andhardy triticale all follow this pattern, with somerelatively small differences that will be addressedin the section for each cover crop.There is growing interest in the use of brassica

and mustard cover crops due to their “biofumiga-tion” characteristics.They release biotoxic chemi-cals as they break down, and have been found toreduce disease, weed and nematode pressure inthe subsequent crop. Brassicas and mustards pro-vide most of the benefits of other nonlegumecover crops,while some (forage radish, for exam-ple) are thought to alleviate soil compaction. Seethe chapter,Brassicas and Mustards (pp. 81), formore information.Perennial and warm-season forage grasses also

can serve well as cover crops. Forage grasses, likesod crops, are excellent for nutrient scavenging,erosion control, biomass production and weedcontrol. Perennials used as cover crops are usual-ly grown for about one year. Summer-annual(warm-season) grasses may fill a niche for biomassproduction and weed or erosion control if the

OVERVIEW OF NONLEGUME COVER CROPS

ground would otherwise be left fallow (betweenvegetable crops, for example). Buckwheat, whilenot a grass, is also a warm-season plant used in thesame ways as summer-annual grasses.Nonlegume cover crops are higher in carbon

than legume cover crops. Because of their highcarbon content, grasses break down more slowlythan legumes, resulting in longer-lasting residue.As grasses mature, the carbon-to-nitrogen ratio(C:N) increases. This has two tangible results:The higher carbon residue is harder for soilmicrobes to break down, so the process takeslonger, and the nutrients contained in the covercrop residue usually are less available to the nextcrop.So although grass cover crops take up leftover

N from the previous crop,as they mature the N isless likely to be released for use by a crop grownimmediately after the grass cover crop. As anexample of this, think of how long it takes forstraw to decompose in the field. Over time, theresidue does break down and nutrients arereleased. In general, this slower decompositionand the higher carbon content of grasses can leadto increased soil organic matter, compared tolegumes.The carbon content and breakdown rate of

brassicas is usually intermediate to grasses andlegumes, depending on maturity when terminat-ed. Brassicas and mustards can take up as much Nas grass cover crops, but may release that N morereadily to the subsequent crop.Nonlegume cover crops can produce a lot of

residue,which contributes to their ability to preventerosion and suppress weeds while they are growingor when left on the soil surface as a mulch.Although grasses and other nonlegumes con-

tain some nitrogen in their plant tissues, they gen-erally are not significant sources of N for yourcropping system.They do, however, keep excesssoil N from leaching, and prevent the loss of soilorganic matter through erosion.Management of nonlegumes in your cropping

system may involve balancing the amount of


Lolium multiflorum

Also called: Italian ryegrass

Type: cool season annual grass

Roles: prevent erosion, improvesoil structure and drainage, addorganic matter, suppress weeds,scavenge nutrients

Mix with: legumes, grasses

See charts, pp. 66 to 72, for rankingand management summary.

BENEFITS

Erosion fighter. Ryegrass has an extensive, soil-holding root system. The cover crop establishesquickly even in poor, rocky or wet soils and toler-ates some flooding once established.It’s well-suitedfor field strips, grass waterways or exposed areas.

Soil builder. Ryegrass’s dense yet shallow rootsystem improves water infiltration and enhancessoil tilth. Rapid aboveground growth helpssupply organic matter. Expect about 4,000 to8,000 lb. dry matter/A on average with a multicutregimen, climbing as high as 9,000 lb. DM/A overa full field season with high moisture and fertility.

ANNUAL RYEGRASS

If you want to build soil without investingmuch in a cover crop, consider annual rye-grass. A quick-growing, nonspreading bunch

grass, annual ryegrass is a reliable, versatile per-former almost anywhere, assuming adequatemoisture and fertility. It does a fine job of holdingsoil, taking up excess N and outcompeting weeds.Ryegrass is an excellent choice for building soil

structure in orchards, vineyards and other crop-land to enhance water infiltration, water-holdingcapacity or irrigation efficiency. It can reduce soilsplash on solanaceous crops and small fruit crops,decreasing disease and increasing forage quality.You also can overseed ryegrass readily into corn,soybeans and many high-value crops.

residue produced with the possibility of tying upN for more than one season.Mixtures of grass andlegume cover crops can alleviate the N-immobi-lization effect, can produce as much or more drymatter as a pure grass stand and may provide bet-ter erosion control due to the differences ingrowth habit.Suggestions for cover crop mixturesare found in the individual cover crop sections.

In addition to grasses, another summer non-legume is buckwheat,which is described in detailin its own section (p. 90). Buckwheat is usuallyclassed as a non-grass coarse grain.While it is man-aged like a quick-growing grain, it has a succulentstem, large leaves and white blossoms.

ANNUAL RYEGRASS 75

Weed suppressor. Mixed with legumes or grass-es, annual ryegrass usually establishes first andimproves early-season weed control. With ade-quate moisture, it serves well in Hardiness Zone 6and warmer as a living mulch in high-valuesystems where you can mow it regularly. It maywinterkill elsewhere, especially without pro-tective snow cover during prolonged cold snaps.Even so, its quick establishment in fall still wouldprovide an excellent,winterkilled mulch for early-spring weed suppression.

Nutrient catch crop.A high N user, ryegrass cancapture leftover N and reduce nitrate leachingover winter. Provided it survives the winter, itsextensive, fibrous root system can take up asmuch as 43 lb. N/A, a University of Californiastudy showed (445). It took up about 60 lb. N/Aby mid-May following corn in a Maryland study.Cereal rye scavenged the same amount of N bymid-April on this silt loam soil (372). Ryegrassworks well ahead of no-till corn or soybeans inthe Corn Belt, sometimes winterkilling,or spray itfor a weed-controlling mulch (302).

Nurse/companion crop. Ryegrass helps slow-growing, fall-seeded legumes establish and over-winter in the northern U.S., even if the ryegrasswinterkills. It tends to outcompete legumes in theSouth, although low N fertility favors the legume.

Emergency forage. Ryegrass is a very palatableforage (132).You can extend the grazing period inlate fall and early spring by letting livestock grazecover crops of ryegrass or a ryegrass-based mix.Annual ryegrass can be used as emergency forage ifalfalfa winterkills. It establishes quickly and pro-duces a lot of forage in a short amount of time.

MANAGEMENT

Ryegrass prefers fertile,well-drained loam or sandyloam soils, but establishes well on many soil types,including poor or rocky soils. It tolerates clay orpoorly-drained soils in a range of climates and willoutperform small grains on wet soils (132,421).Annual ryegrass has a biennial tendency in cool

regions. If it overwinters, it will regrow quicklyand produce seed in late spring. Although few

plants survive more than a year, this reseedingcharacteristic can create a weed problem in someareas, such as the mid-Atlantic or other areas withmild winters. In the Midwest and Southern Plains,it can be a serious weed problem in oat andwheat crops. It has also been shown to developherbicide resistance, compounding possibleweed problems (161).

Establishment & FieldworkAnnual ryegrass germinates and establishes welleven in cool soil (421).Broadcast seed at 20 to 30lb./A.You needn’t incorporate seed when broad-casting onto freshly cultivated soil—the first goodshower ensures seed coverage and good germina-tion. Cultipacking can reduce soil heaving, how-ever, especially with late-fall plantings. Drill 10 to20 lb./A, 1/4 to 1/2 inch deep.Noncertified seed will reduce seeding cost,

although it can introduce weeds. Annual ryegrassalso cross-pollinates with perennial ryegrass andturf-type annual ryegrass species, so don’t expecta pure stand if seeding common annual ryegrass.

Winter annual use. Seed in fall in Zone 6 orwarmer. In Zone 5 and colder, seed from mid-summer to early fall—but at least 40 days beforeyour area’s first killing frost (194). Late seedingincreases the probability of winterkill.

ANNUAL RYEGRASS (Lolium multiflorum)

MarianneSarrantonio


If aerially seeding, increase rates at least 30 per-cent compared to broadcast seeding rate (18).Youcan overseed into corn at last cultivation or later(consider adding 5 to 10 pounds of red or whiteclover with it) or plant right after corn silage har-vest. Overseed into soybeans at leaf-yellowing orlater (191, 194). When overseeding into solana-ceous crops such as peppers, tomatoes and egg-plant, wait until early to full bloom.

Spring seeding. Sow ryegrass right after smallgrains or an early-spring vegetable crop, for a four-to eight-week summer period before a fall veg-etable crop (361).

Mixed seeding. Plant ryegrass at 8 to 15 lb./Awith a legume or small grain, either in fall or earlyin spring. Ryegrass will dominate the mixtureunless you plant at low rates or mow regularly.The legume will compete better in low-N condi-tions. Seed the legume at about two-thirds its nor-mal rate. Adequate P and K levels are importantwhen growing annual ryegrass with a legume.In vineyards,a fall-seeded,50:50 mix of ryegrass

and crimson clover works well, some Californiagrowers have found (211).Although not a frequent pairing, drilling rye-

grass in early spring at 20 lb./A with an oatsnurse crop or frost seeding 10 lb./A into over-wintered small grains can provide some fine fallgrazing. Frost seeding with red clover or otherlarge-seeded, cool-season legumes also can workwell, although the ryegrass could winterkill insome conditions.

Maintenance. Avoid overgrazing or mowing rye-grass closer than 3 to 4 inches. A stand can persistmany years in orchards,vineyards,and other areasif allowed to reseed naturally and not subject toprolonged heat, cold or drought.That’s rarely thecase in Zone 5 and colder, however, where cli-mate extremes take their toll. Perennial ryegrassmay be a smarter choice if persistence is impor-tant. Otherwise, plan on incorporating the coverwithin a year of planting.Annual ryegrass is a rel-atively late maturing plant, so in vineyards it mayuse excessive water and N if left too long.

Killing & ControllingYou can kill annual ryegrass mechanically by disk-ing or plowing, preferably during early bloom(usually in spring), before it sets seed (361, 422).Mowing may not kill ryegrass completely (103).You also can kill annual ryegrass with non-persistent contact herbicides, although someusers report incomplete kill and/or resistance toglyphosate (161, 302).To minimize N tie-up as the biomass decom-

poses, wait a few weeks after incorporationbefore you seed a subsequent crop.Growing rye-grass with a legume such as red clover would min-imize the N concern. By letting the cover residuedecompose a bit,you’ll also have a seedbed that iseasier to manage.

Pest ManagementWeed potential. Ryegrass can become a weed ifallowed to set seed (361).It often volunteers in vine-yards or orchards if there is high fertility and mayrequire regular mowing to reduce competition withvines (422). A local weed management specialistmay be able to recommend a herbicide that canreduce ryegrass germination if the cover is becominga weed in perennial grass stands. Chlorsulfuron issometimes used for this purpose in California (422).

Insect and other pests. Ryegrass attracts fewinsect pests and generally can help reduce insectpest levels in legume stands and many vegetablecrops, such as root crops and brassicas. Rodentsare occasionally a problem when ryegrass is usedas a living mulch.Rust occasionally can be a problem with annu-

al ryegrasses, especially crown and brown (stem)rust. Look for resistant, regionally adapted vari-eties. Annual ryegrass also can host high densitiesof pin nematodes (Paratylenchus projectus) andbromegrass mosaic virus, which plant-parasiticnematodes (Xiphinema spp.) transmit (422).

Other OptionsRyegrass provides a good grazing option that canextend the grazing season for almost any kind of live-stock.Although very small-seeded, ryegrass does nottiller heavily,so seed at high rates if you expect a rye-

BARLEY 77

grass cover crop also to serve as a pasture.Some vari-eties tolerate heat fairly well and can persist for sev-eral years under sound grazing practices that allowthe grass to reseed.As a hay option, annual ryegrasscan provide 2,000 to 6,000 pounds of dry forage peracre,depending onmoisture and fertility levels (422).For highest quality hay, cut no later than the earlybloom stage and consider growing it with a legume.When using ryegrass for grass waterways and con-servation strips on highly erodible slopes, applying3,000 to 4,000pounds of strawper acre after seedingat medium to high rates can help keep soil and seedin place until the stand establishes (422).

Management CautionsRyegrass is a heavy user of moisture and N. It per-forms poorly during drought or long periods ofhigh or low temperature, and in low-fertility soils.It can compete heavily for soil moisture whenused as living mulch. It also can become a weedproblem (361).

COMPARATIVE NOTES

• Establishes faster than perennial ryegrass butis less cold-hardy

• Less persistent but easier to incorporate thanperennial ryegrass

• About half as expensive as perennial ryegrass• In Southern USA, annual is more adapted andproduces much greater biomass

Cultivars. Many varieties are widely available.Improved cultivars should be considered if grow-ing for forage.There are diploid (2n = 14 chromo-somes) and tetraploid (4n = 28 chromosomes)cultivars. Tetraploids produce larger plants withwider leaves and mature later.

Seed sources. See Seed Suppliers (p. 195).

Hordeum vulgare

Type: cool season annualcereal grain

Roles: prevent erosion, suppressweeds, scavenge excess nutrients,add organic matter

Mix with: annual legumes, ryegrassor other small grains


grains and can sop up excess subsoil moisture tohelp prevent saline seep formation (136).It’s a fine choice for reclaiming overworked,weedy

or eroded fields, or as part of a cover crop mix forimproving soil tilth and nutrient cycling in perennialcropping systems in Hardiness Zone 8 or warmer.

BARLEY

Inexpensive and easy to grow, barley providesexceptional erosion control and weed sup-pression in semi-arid regions and in light soils.It

also can fill short rotation niches or serve as a top-soil-protecting crop during droughty conditions inany region. It is more salt tolerant than other small


Barley prefers cool, dry growing areas. As aspring cover crop, it can be grown farther norththan any other cereal grain, largely because of itsshort growing period. It also can produce morebiomass in a shorter time than any other cerealcrop (273).

BENEFITS

Erosion control. Use barley as an overwinteringcover crop for erosion control in Zone 8 andwarmer, including much of California, western

Oregon and westernWashington. It’s well-suited for vineyardsand orchards, or aspart of a mixed seed-ing.As a winter annual,

barley develops a deep,fibrous root system.The roots can reach asdeep as 6.5 feet. As aspring crop, barley hasa comparatively shal-low root system butholds soil strongly to

minimize erosion during droughty conditions (71).

Nutrient recycler. Barley can scavenge significantamounts of nitrogen. It captured 32 lb. N/A as awinter cover crop following a stand of fava beans(Vicia faba) in a California study, compared with20 lb./A for annual ryegrass. A barley cover cropreduced soil N an average of 64 percent at eightsites throughout North America that had receivedan average of 107 lb.N/A (265). Intercropping bar-ley with field peas (Pisum sativum) can increasethe amount of N absorbed by barley and returnedto the soil in barley residue, other studies show(215, 218). Barley improves P and K cycling if theresidue isn’t removed.

Weed suppressor. Quick to establish,barley out-competes weeds largely by absorbing soil mois-ture during its early growing stages. It also shadesout weeds and releases allelopathic chemicalsthat help suppress them.

Tilth-improving organic matter. Barley is aquick source of abundant biomass that, along withits thick root system, can improve soil structureand water infiltration (273,445). In California crop-ping systems, cultivars such as UC476 or COSINAcan produce as much as 12,900 lb.biomass/A.

Nurse crop. Barley has an upright posture andrelatively open canopy that makes it a fine nursecrop for establishing a forage or legume stand.Less competitive than other small grains, barleyalso uses less water than other covers crops. Inweedy fields, wait to broadcast the forage orlegume until after you’ve mechanically weededbarley at the four- or five-leaf stage to reduceweed competition.As an inexpensive, easy-to-kill companion crop,

barley can protect sugarbeet seedlings during theirfirst two months while also serving as a soil pro-tectant during droughty periods (details below).

Pest suppression. Barley can reduce incidence ofleafhoppers, aphids, armyworms, root-knot nema-todes and other pests, a number of studies suggest.

MANAGEMENT

Establishment & FieldworkBarley establishes readily in prepared seedbeds,and can also be successfully no-tilled. It prefersadequate but not excessive moisture and doespoorly in waterlogged soils. It grows best in well-drained, fertile loams or light, clay soils in areashaving cool,dry,mild winters. It also does well onlight, droughty soils and tolerates somewhat alka-line soils better than other cereal crops.With many varieties of barley to choose from,

be sure to select a regionally adapted one. Manyare well-adapted to high altitudes and cold, shortgrowing seasons.

Spring annual use.Drill at 50 to 100 lb./A (1 to 2bushels) from 3/4 to 2 inches deep into a preparedseedbed,or no-till using the same seeding rate.If broadcasting, prepare the seedbed with at

least a light field cultivation. Sow 80 to 125 lb./A(1.5 to 2.5 bushels) and harrow, cultipack or disklightly to cover. Use a lower rate (25 to 50

A fast-growing

barley can be

grown farther

north and produce

more biomass in

a shorter time

than any other

cereal grain.

BARLEY 79

pounds) if overseeding as a companion crop or ahigher rate (140 pounds) for very weedy fields.When broadcasting, consider seeding half in onedirection, then the rest in a perpendicular direc-tion for better coverage (71).

Winter annual use. Barley can be used as a win-ter annual cover crop wherever it is grown as awinter grain crop. It is less winter-hardy than rye.In Zone 8 or warmer, it grows throughout thewinter if planted from September throughFebruary. Plantings before November 1 generallyfare best, largely due to warmer soil conditions.Expect mixed results if trying to use barley as a

self-reseeding cover crop.

Mixed seedings. Barley works well in mixtureswith other grasses or legumes.In low-fertility soilsor where you’re trying to minimize tie-up of soilnitrogen, growing barley with one or morelegumes can be helpful. Your seeding cost perpound will increase,but the reduced seeding ratecan offset some of this. A short-season Canadianfield pea would be a good companion, or try anoat/barley/pea mix, suggests organic farmer JackLazor,Westfield,Vt.In northern California, Phil LaRocca (LaRocca

Vineyards, Forest Ranch, Calif.) lightly disks hisupper vineyard’s soil before broadcasting a mixof barley, fescue, brome, LANA vetch, and crimson,red and subterranean clovers, usually duringOctober.He seeds at 30 to 35 lb./A,with 10 to 20percent being barley. “I’ve always added morebarley to the seeding rate than recommended.More is better, especially with barley, if you wantbiomass and weed suppression,”he says.After broadcasting, LaRocca covers erosion-

prone areas with 2 tons of rice straw per acre,which is “cheaper than oat straw here and hasfewer weed seeds,” he notes.“The straw decom-poses quickly and holds seed and soil well.”Besides contributing to soil humus (as the covercrop also does), the straw helps keep the seedbedwarm and moist. That can be very helpful inLaRocca’s upper vineyard, where it sometimessnows in winter.In his other, less-erodible vineyard, LaRocca

disks up the cover vegetation, then runs a harrow

quickly on top of the diskedalleyways to set a seedbedbefore broadcasting andcultipacking a similarmix of cover crops.

Field ManagementAlthough barley absorbs alot of water in its earlystages, it uses moisturemore efficiently than othercereals and can be grownwithout irrigation insome situations.Abouthalf of the commer-cial barley acreagein dryland areas isirrigated, however.California croppingsystems that includebarley tend to beirrigated as well.Low seeding rateswon’t necessarilyconserve moisture, as vegetative growth oftenincreases.LaRocca hasn’t had any moisture problems or

grape-yield concerns from growing barley orother cover crops, even in the 40 percent of hisupper vineyard that isn’t furrow-irrigated.“Onceyour vines are established, their root system isdeeper and much more competitive than a typicalcover crop’s root system,”he observes.Mowing can postpone and prolong barley

flowering, as with other cereal grains. As a springcover, barley puts on biomass quickly, so you cankill it in plenty of time for seeding a followingcrop. If you want barley to reseed, don’t mowuntil most of the stand has headed and seed isabout to fall off.To encourage reseeding of his cover mix, Phil

LaRocca allows every other row in his upper vine-yard to go to seed, then disks it down.That letshim skip reseeding some blocks.If you’re concerned about barley reseeding or

crop competition when intercropped, however,plant a lighter stand,suggestsAlan Brutlag,Wendell,Minn. During droughty conditions, he broadcasts

BARLEY (Hordeum vulgare)

ElayneSears


25 to 30 pounds of barley per acre as a soil-protec-tive companion crop for sugarbeet seedlings.Thelow-density stand is easy to stunt or kill a monthlater with the combination of herbicides and cropoil that he uses for weed control in his sugarbeets.Another control option is a single application of anherbicide labeled for grass control.

KillingKill barley with a grass herbicide in late spring, orby rolling disking or mowing at the mid- to late-bloom stage but before it starts setting seed.If plant-parasitic nematodes have been a prob-

lem, incorporate overwintered barley early inspring, before warm temperatures encouragenematode populations.

Pest ManagementAnnual weeds and lodging can occur when grow-ing barley in high-fertility soils, although thesewouldn’t pose problems in a barley cover crop.Despite their less dense canopy, six-rowed vari-eties tend to be taller and more competitiveagainst weeds than two-rowed varieties. If you’reconsidering a grain option, harrowing or hoeingjust before barley emergence could reduce weedsthat already have sprouted.Barley produces alkaloids that have been

shown to inhibit germination and growth ofwhite mustard (247).These exudates also protectbarley plants from fungus, armyworm larvae, bac-teria and aphids (248, 455).Barley seems to reduce the incidence of grape

leafhoppers in vineyards and increase levels ofbeneficial spiders, one California growerobserved (211). Growing high-biomass covercrops such as barley or rye increased populationsof centipedes,predator mites and other importantpredators, independent of tillage system used, astudy in the Pacific Northwest found (444).Cutworms and other small grain pests can be

occasional problems. Some perennial crop grow-ers in California report increased incidence ofgophers when growing cover crop mixes and tryto minimize this by encouraging owl populations.Avoid seeding in cold, damp soils, which makes

barley more prone to fungus and disease. Assumingadequate soil moisture, shallow seeding can hasten

emergence and lessen incidence of root rot disease,if this has been a problem in your area (397).Varieties resistant to leaf diseases are available.Two-rowed varieties are more resistant to leaf rust andmildew. Also avoid planting barley after wheat.If nematodes are likely to be a problem, plant

late in fall or during winter to avoid warm-seasongrowth and incorporate early in spring in Zone 8and warmer. Barley can be a host for a nematodespecies (Meloidogyne javanica) that adverselyaffects Thompson seedless grapes.Barley drastically reduced root-knot nematode

(Meloidogyne hapla M. Chitwood) populationsand increased marketable carrot yields by at leastseventeen-fold in a Quebec study comparingthree-year rotations (242).

Other OptionsBarley can be grazed lightly in winter or spring orcut for hay/haylage (191). It has greater forage nutri-tive value than oats,wheat or triticale. It also can begrown as a specialty grain for malting, soups, breadand other uses.As a feed grain (in a hog ration, forexample), it can replace some costlier corn.

COMPARATIVE NOTES

• Barley tillers more than oats and also is moredrought-tolerant, but oats generally performbetter as a companion crop or winterkillednurse crop because they are less competitivethan barley (397).

• Barley tolerates alkaline soils better than anyother cereal.

• Winter cultivars are less winterhardy thanwinter wheat, triticale or cereal rye.

Cultivars. Many commercial varieties are avail-able. Look for low-cost, regionally adapted culti-vars with at least 95-percent germination.Six-rowed cultivars are better for overseeding,and

are more heat- and drought-tolerant. Two-rowedtypes have more symmetrical kernels and are moredisease-resistant (e.g. leaf rust and mildew) than six-rowed types, in which two-thirds of the lateral rowsof the spike are smaller and twisted.


BRASSICAS AND MUSTARDS 81

Type: Annual (usually winter or spring;summer use possible)

Roles: Prevent erosion, suppress weeds andsoilborne pests, alleviate soil compaction andscavenge nutrients

Mix with: Other brassicas or mustards, smallgrains or crimson clover

Species: Brassica napus, Brassica rapa,Brassica juncea, Brassica hirta, Raphanussativus, Sinapsis alba

See charts, pp. 66 to 72, for ranking andmanagement summary.

Adaptation Note: This chapter addresses man-agement of eight different cover crop specieswith varying degrees of winterhardiness. Somecan be managed as winter or spring annuals.Others are best planted in late summer for covercrop use but will winterkill. Consult the infor-mation on management, winterhardiness andwinter vs. spring use (pp. 87-88) and the exam-ples throughout the chapter, then check withlocal experts for specific adaptation informationfor your brassica cover crop of choice.

BRASSICAS AND MUSTARDS

Nomenclature Note: The cover cropsdescribed in this chapter all belong to thefamily BRASSICACEAE. Most but not all of thespecies belong to the genus Brassica. In com-mon usage, the various species are sometimeslumped together as “brassicas” and sometimesdistinguished as “brassicas” vs. “mustards.” Inthis book, we will use brassicas as an umbrellaterm for all species; mustards will be used todistinguish that subgroup, which has someunique characteristics.

RAPE or CANOLA (Brassica rapa)

MarianneSarrantonio

Brassica and mustard cover crops are knownfor their rapid fall growth, great biomassproduction and nutrient scavenging ability.

However, they are attracting renewed interest pri-marily because of their pest management charac-teristics. Most Brassica species release chemicalcompounds that may be toxic to soil bornepathogens and pests, such as nematodes, fungiand some weeds. The mustards usually havehigher concentrations of these chemicals.Brassicas are increasingly used as winter or rota-

tional cover crops in vegetable and specialty cropproduction,such as potatoes and tree fruits.There isalso growing interest in their use in row crop pro-duction, primarily for nutrient capture, nematode

trapping, and biotoxic or biofumigation activity.Some brassicas have a large taproot that can breakthrough plow pans better than the fibrous roots ofcereal cover crops or the mustards.Those brassicasthat winterkill decompose very quickly and leave aseedbed that is mellow and easy to plant in.With a number of different species to consider,

you will likely find one or more that can fit yourfarming system. Don’t expect brassicas to elimi-nate your pest problems, however. They are agood tool and an excellent rotation crop,but pestmanagement results are inconsistent. Moreresearch is needed to further clarify the variablesaffecting the release and toxicity of the chemicalcompounds involved (see p. 82).


BENEFITS

Erosion control and nutrient scavenging.Brassicas can provide greater than 80% soil cover-age when used as a winter cover crop (176).Depending on location, planting date and soil fer-tility, they produce up to 8,000 lb. biomass/A.Because of their fast fall growth,brassicas are well-suited to capture soil nitrogen (N) remaining aftercrop harvest.The amount of nitrogen captured ismainly related to biomass accumulation and theamount of N available in the soil profile.Because they immobilize less nitrogen than

some cereal cover crops,much of the N taken upcan become available for uptake by main crops inearly to late spring (see also Building Soil Fertility

and Tilth with CoverCrops, pp. 16–24).Brassicas can root todepths of six feet ormore, scavenging nutri-ents from below therooting depth of mostcrops.To maximize bio-mass production andnutrient scavenging inthe fall, brassicas must

be planted earlier than winter cereal cover cropsin most regions,making them more difficult to fitinto grain production rotations.

Pest management.All brassicas have been shownto release bio-toxic compounds or metabolic by-products that exhibit broad activity against bacte-ria, fungi, insects, nematodes, and weeds. Brassicacover crops are often mowed and incorporated tomaximize their natural fumigant potential.This isbecause the fumigant chemicals are produced onlywhen individual plant cells are ruptured.Pest suppression is believed to be the result of

glucosinolate degradation into biologically activesulfur containing compounds call thiocyanates(152, 320).To maximize pest suppression, incor-poration should occur during vulnerable life-stages of the pest (446).The biotoxic activity of brassica and mustard

cover crops is low compared to the activity of

commercial fumigants (388). It varies dependingon species, planting date, growth stage whenkilled, climate and tillage system. Be sure to con-sult local expertise for best results.

▼Precaution. The use of brassicas for pest man-agement is in its infancy. Results are inconsistentfrom year to year and in different geographicregions. Different species and varieties containdifferent amounts of bioactive chemicals. Be sureto consult local expertise and begin with smalltest plots on your farm.

DiseaseIn Washington, a SARE-funded study of brassicagreen manures in potato cropping systems com-pared winter rape (Brassica napus) and whitemustard (Sinapis alba) to no green manure,withand without herbicides and fungicides.The win-ter rape system had a greater proportion ofRhizoctonia-free tubers (64%) than the whitemustard (27%) and no green manure (28%) treat-ments in the non-fumigated plots.There was lessVerticillium wilt incidence with winter rapeincorporation (7%) than with white mustard(21%) or no green manure incorporation (22%) innon-fumigated plots (88).In Maine, researchers have documented consis-

tent reductions in Rhizoctonia (canker and blackscurf) on potato following either rapeseed greenmanure or canola grown for grain (459, 460).They have also observed significant reductions inpowdery scab (caused by Spongospora subter-ranea) and common scab (Streptomyces scabiei)following brassica green manures, especially anIndianmustard (B.juncea) greenmanure (458,459).

NematodesInWashington state, a series of studies addressedthe effect of various brassica and mustard covercrops on nematodes in potato systems (260, 266,353, 283, 284, 285).The Columbia root-knot nematode (Meloi-

dogyne chitwoodi) is a major pest in the PacificNorthwest.It is usually treated with soil fumigantscosting $20 million inWashington alone.

Brassicas must

be planted earlier

than winter cereal

cover crops in

most regions.


Rapeseed, arugula and mustard were studied asalternatives to fumigation. The brassica covercrops are usually planted in late summer (August)or early fall and incorporated in spring beforeplanting mustard.Results are promising,with nematodes reduced

up to 80%, but—because of the very low damagethreshold—green manures alone cannot be rec-ommended for adequate control ofMeloidogynechitwoodi in potatoes. The current recommend-ed alternative to fumigation is the use of rapeseedor mustard cover crop plus the application ofMOCAP. This regimen costs about the same asfumigation (2006 prices).Several brassicas are hosts for plant parasitic

nematodes and can be used as trap crops followedby an application of a synthetic nematicide.Washington State University nematologist EkateriniRiga has been planting arugula in the end ofAugustand incorporating it in the end of October.Nematicides are applied two weeks after incor-

poration, either at a reduced rate using Telone orthe full rate of Mocap and Temik. Two years offield trials have shown that arugula in combina-tion with synthetic nematicides reduced M. chit-woodi to economic thresholds.Longer crop rotations that include mustards

and non-host crops are also effective for nema-tode management. For example, a 3-year rotationof potatoes>corn>wheat provides nearly com-plete control of the northern root-knot nematode(Meloidogyne hapla) compared to methyl bro-mide and other broad-spectrum nematicides.However,because the rotation crops are less prof-

itable than potatoes, they are less commonly used.Not until growers better appreciate the less tangiblelong-term cover crop benefits of soil improvement,nutrient management and pest suppression willsuch practices be more widely adopted.InWyoming,oilseed radish (Raphanus sativus)

and yellow mustard (Sinapsis alba) reduced thesugar beet cyst nematode populations by 19-75%,with greater suppression related to greateramount of cover crop biomass (231).In Maryland, rapeseed, forage radish and a mus-

tard blend did not significantly reduce incidenceof soybean cyst nematode (which is closely relat-

ed to the sugar beet cyst nematode). The samespecies, when grown with rye or clover, didreduce incidence of stubby root nematode (432).Also in Maryland, in no-till corn on a sandy soil,

winterkilled forage radish increased bacteria-eat-ing nematodes, rye and rapeseed increased theproportion of fungal feeding nematodes, whilenematode communities without cover cropswere intermediate.The Enrichment Index,whichindicates a greater abundance of opportunisticbacteria–eating nematodes, was 23% higher insoils that had brassica cover crops than theunweeded control plots.These samples, taken in November, June (a

month after spring cover crop kill), and August(under no-till corn), suggest that the cover crops,living or dead,increased bacterial activity and mayhave enhanced nitrogen cycling through the foodweb (432).

WeedsLike most green manures, brassica cover cropssuppress weeds in the fall with their rapid growthand canopy closure. In spring, brassica residuescan inhibit small seeded annual weeds such as,pigweed, shepherds purse, green foxtail, kochia,hairy nightshade, puncturevine, longspine sand-bur, and barnyardgrass (293), although pigweedwas not inhibited by yellow mustard (178).In most cases, early season weed suppression

obtained with brassica cover crops must be sup-plemented with herbicides or cultivation to avoidcrop yield losses from weed competition later inthe season. As a component of integrated weedmanagement, using brassica cover crops in veg-etable rotations could improve weed control andreduce reliance on herbicides (39).In Maine, the density of sixteen weed and crop

species was reduced 23 to 34% following incorpo-ration of brassica green manures, and weed estab-lishment was delayed by 2 days, compared to afallow treatment.However,other short-season greenmanure crops including oat, crimson clover andbuckwheat similarly affected establishment (176).In Maryland and Pennsylvania, forage radish is

planted in late August and dies with the first hardfrost (usually December). The living cover crop


and the decomposing residues suppress winterannual weeds until April and result in a mellow,weed-free seedbed into which corn can be no-tilled without any preplant herbicides. Preliminarydata show summer suppression of horseweed butnot lambsquarters,pigweed,or green foxtail (432).Mustard cover crops have been extremely effec-

tive at suppressing winter weeds in tillage inten-sive, high value vegetable production systems inSalinas, California. Mustards work well in tillageintensive systems because they are relatively easyto incorporate into the soil prior to planting veg-etables. However, the growth and biomass pro-duction by mustards in the winter is not usually asreliable as that of other cover crops such as cerealrye and legume/cereal mixtures (45).

Deep tillage. Some brassicas (forage radish, rape-seed, turnip) produce large taproots that can pen-etrate up to six feet to alleviate soil compaction(432).This so-called “biodrilling” is most effectivewhen the plants are growing at a time of yearwhen the soil is moist and easier to penetrate.Their deep rooting also allows these crops to

scavenge nutrients from deep in the soil profile.As the large tap roots decompose, they leavechannels open to the surface that increase waterinfiltration and improve the subsequent growthand soil penetration of crop roots. Smaller rootsdecompose and leave channels through the plowplan and improve the soil penetration by theroots of subsequent crops (446).Most mustards have a fibrous root system, and

rooting effects are similar to small grain covercrops in that they do not root so deeply but devel-op a large root mass more confined to the soilsurface profile.

SPECIES

Rapeseed (or Canola). Two Brassica species arecommonly grown as rapeseed,Brassica napus andBrassica rapa. Rapeseed that has been bred tohave low concentrations of both erucic acid andglucosinolates in the seed is called canola,which isa word derived from Canadian Oil.Annual or spring type rapeseed belongs to the

species B.napus,whereas winter-type or biennial

rapeseed cultivars belong to the species B. rapa.Rapeseed is used as industrial oil while canola isused for a wider range of products includingcooking oils and biodiesel.Besides their use as an oil crop, these species

are also used for forage. If pest suppression is anobjective, rapeseed should be used rather thancanola since the breakdown products of glucosi-nolates are thought to be a principal mechanismfor pest control with these cover crops.Rapeseed has been shown to have biological

activity against plant parasitic nematodes as wellas weeds (176, 365).Due to its rapid fall growth, rapeseed captured

as much as 120 lb.of residual nitrogen per acre inMaryland (6). In Oregon, aboveground biomassaccumulation reached 6,000 lb./A and N accumu-lation was 80 lb./A.Some winter-type cultivars are able to withstand

quite low temperatures (10° F) (352). This makesrapeseed one of themost versatile cruciferous covercrops, because it can be used either as a spring- orsummer-seeded cover crop or a fall-seeded wintercover crop.Rapeseed grows 3 to 5 feet tall.

Mustard. Mustard is a name that is applied tomany different botanical species, including whiteor yellow mustard (Sinapis alba, sometimesreferred to as Brassica hirta), brown or Indianmustard (Brassica juncea)—sometimes erro-neously referred to as canola—and black mustard(B.nigra (L.) (231).The glucosinolate content of most mustards is

very high compared to the true Brassicas.In the SalinasValley,California,mustard biomass

reached 8,500 lb./A. Nitrogen content on highresidual N vegetable ground reached 328 lb. N/A(388, 422).Because mustards are sensitive to freezing,win-

terkilling at about 25º F, they are used either as aspring/summer crop or they winter kill except inareas with little freeze danger. Brown and fieldmustard both can grow to 6 feet tall.In Washington, a wheat/mustard-potato system

shows promise for reducing or eliminating thesoil fumigant metam sodium.White mustard andoriental mustard both suppressed potato earlydying (Verticillium dahliae) and resulted in tuber


yields equivalent to fumigated soils, while alsoimproving infiltration, all at a cost savings ofabout $66/acre (see www.plantmanagementnetwork.org/pub/cm/research/2003/mustard/).Mustards have also been shown to suppress

growth of weeds (See “Weeds” p. 99 and 39, 176,365).

Radish. The true radish or forage radish(Raphanus sativus) does not exist in the wildand has only been known as a cultivated speciessince ancient times. Cultivars developed for highforage biomass or high oilseed yield are also use-ful for cover crop purposes. Common typesinclude oilseed and forage radish.Their rapid fall growth has the potential to cap-

ture nitrogen in large amounts and from deep inthe soil profile (170 lb./acre in Maryland (234).Above ground dry biomass accumulation reached8,000 lb./acre and N accumulation reached 140lb./acre in Michigan (304).Below ground biomassof radishes can be as high as 3,700 lb./acre.Oilseed radish is less affected by frost than for-

age radish,but may be killed by heavy frost below25° F. Radish grows about 2–3 feet tall.Radishes have been shown to alleviate soil

compaction and suppress weeds (177, 446).

Turnips. Turnips (B. rapa L. var. rapa (L.) Thell)are used for human and animal food because oftheir edible root. Turnip has been shown toalleviate soil compaction.While they usually donot produce as much biomass as other brassicas,they provide many macrochannels that facilitatewater infiltration (359). Similar to radish, turnip isunaffected by early frost but will likely be killedby temperatures below 25° F.In anAlabama study of 50 cultivars belonging to

the generaBrassica, Raphanus,and Sinapis,forageand oilseed radish cultivars produced the largestamount of biomass in central and south Alabama,whereas winter-type rapeseed cultivars had thehighest production in NorthAlabama (425).

Some brassicas are also used as vegetables(greens). Cultivated varieties of Brassica rapainclude bok choy (chinensis group),mizuna (nip-posinica group), flowering cabbage (parachinen-

sis group), chinese cabbage (pekinensis group)and turnip (rapa group). Varieties of Brassicanapus include Canadian turnip, kale, rutabaga,rape, swede, swedish turnip and yellow turnip.Collard, another vegetable, is a cabbage, B. oler-acea var. acephala, and B. juncea is consumed asmustard greens.A grower in Maryland reported harvesting the

larger roots of forage radish (cultivar DAIKON)cover crop to sell as a vegetable. In California,broccoli reduced the incidence of lettuce dropcaused by Sclerotinia minor (175).

AGRONOMIC SYSTEMS

Brassicas must be planted earlier than small graincover crops for maximum benefits, making it dif-ficult to integrate them into cash grain rotations.Broadcasting seeding (including aerial seed-

ing) into standing crops of corn or soybean hasbeen successful in some regions (235). See alsoAfter 25 Years, Improvements Keep Coming,(p. 52). Brassica growth does not normally inter-fere with soybean harvest, although could be aproblem if soybean harvest is delayed.The shad-ing by the crop canopy results in less cover cropbiomass and especially less root growth, so thisoption is not recommended where thebrassica cover crop is intended for compactionalleviation.In a Maryland SARE-funded project, dairy

farmers planted forage radish immediately aftercorn silage harvest.With a good stand of forageradish, which winterkills, corn can be plantedin early spring without tillage or herbicides,resulting in considerable savings. The N releasedby the decomposed forage radish residuesincreased corn yield boost in most years.This practice is particularly useful whenmanure is fall-applied to corn silage fields. (Formore information see SARE project reportLNE03-192 http://www.sare.org/reporting/report_viewer.asp?pn=LNE03-192).

▼ Precaution: Brassica cover crops may be sus-ceptible to carry-over from broadleaf herbicidesapplied to the previous grain crop.

Looking for a green manure crop to maintainsoil quality in his intensive potato/wheatrotation,Dale Gies not only improvedinfiltration and irrigation efficiency, he alsofound biofumigation, a new concept in pestmanagement.Farming 750 irrigated acres with two sons

and a son-in-law in the Columbia basin of GrantCounty,Wash.,Gies started growing greenmanure crops in 1990 because he wanted toimprove his soils for future generations. Sincethen,he has reduced his use of soil fumigantsthanks to the biocidal properties of Brassicacover crops. In particular,Gies is most excitedabout results using a mixture of white ororiental mustard and arugula (Eruca sativa),also a brassica, to manage nematodes andpotato early dying disease.“We use the mustards to augment other

good management practices,”Gies cautions.“Don’t expect a silver bullet that will solveyour pest problems with one use.”Controlling nematodes is essential to

quality potato production, both for thedomestic and the international market.Farmers typically manage root knotnematodes (Meloidogyne chitwoodi) andfungal diseases with pesticides, such asMetam sodium, a fumigant used routinely to

control early dying disease (Verticilliumdahliae), that cost that up to $500 per acre.Farmers are especially vulnerable to earlydying disease if their rotations contain fewerthan three years between potato crops.However,with potato prices dropping,

potato farmers inWashington and elsewherestarted looking for ways to reduce costs. Giescontacted Andy McGuire atWashington StateUniversity Extension for help documentingthe results he was seeing with brassicas.With research funding from SARE,McGuireconfirmed that the mustards improvedinfiltration. He also showed that whitemustard was as effective as metam sodiumin controlling potato early dying disease.“The findings suggest that mustard green

manures may be a viable alternative to thefumigant metam sodium in some potatocropping systems,” says McGuire.“The practicecan also improve water infiltration rates andprovide substantial savings to farmers.Untilmore research is done, however,mustardcover crops should be used to enhance, noteliminate, chemical control of nematodes.”Researchers have found that mustards can

also suppress common root rot (Aphano-myces euteiches) and the northern root-knotnematode (Meloidogyne hapla).


Mustard Mix Manages Nematodes in Potato/Wheat System

Vegetable Systems. Fall-planted brassica covercrops fit well into vegetable cropping systems fol-lowing early harvested crops.White mustard andbrown mustard have become popular fall-plantedcover crops in the potato producing regions ofthe Columbia Basin of easternWashington.Planted in mid to late August, white mustard

emerges quickly and produces a large amount ofbiomass before succumbing to freezing tempera-tures. As a component of integrated weed man-agement, using brassica cover crops in vegetablerotations could improve weed control and reducereliance on herbicides (39).

Winter-killed forage radish leaves a nearlyweed- and residue-free seedbed, excellent forearly spring “no-till” seeding of crops such as car-rots, lettuce, peas and sweet corn.This approachcan save several tillage passes or herbicide appli-cations for weed control in early spring and cantake advantage of the early nitrogen release by theforage radish. Soils warm up faster than underheavy residue, and because no seedbed prepara-tion or weed control is needed, the cash crop canbe seeded earlier than normal.


Two types of mustard commonly used inthe Columbia Basin are white mustard(Sinapis alba, also called Brassica hirta oryellow mustard), and Oriental mustard(Brassica juncea, also called Indian or brownmustard). Blends of the two are often plantedas green manures. Fall incorporation seems tobe best to control nematodes and soil-bornediseases, and Oriental mustard may be betterat it than white mustard.Gies plants a mix of mustards and NEMAT,

an arugula variety developed in Italy fornematode suppression.The arugula attractsnematodes but they cannot reproduce on itsroots, so nematode populations reduce,according toWashington State Universityresearcher Ekaterini Riga.Riga’s greenhouse studies showed that

arugula reduced Columbia root knotnematode (Meloidogyne chitwoodi)populations compared to the control or othergreen manure treatments. Subsequent fieldtrial in 2005 and 2006 showed that arugula incombination with half the recommended rateof Telone (another fumigant) or full rates ofMocap andTemik reduced root knotnematode populations from 700 nematodesper gram of soil to zero.The combination alsoimproved potato yield and tuber quality and itis still affordable by the growers.

“Arugula acts both as a green manure and anematode trap crop,” says Riga.“It contains chemicals with high biocidal

activity that mimic synthetic fumigants. Sincenematodes are attracted to the roots ofArugula, it can be managed as a trap crop.”What causes brassicas to have biocidal

properties? Researchers are keying in on thepresence of glucosinolates in mustards.Whenthe crop is incorporated into the soil, thebreakdown of glucosinolates produces otherchemicals that act against pests.Thosesecondary chemicals behave like the activechemical in commercial fumigants like metamsodium.More research is needed to better

determine site- and species-specific brassicacover crop effects on pests. It seems to beworking for Dale Gies, however,“whose shortseason fresh market potato system probablyfunctions differently than processing potatoes”according toWSU’s Andy McGuire.To stayupdated on cover crop work inWashingtonState, see www.grant-adams.wsu.edu/agriculture/ covercrops/green_manures/.For Gies, however,“Tying the whole system

together makes it work economically,and itimproves the soil.”—Andy Clark

MANAGEMENT

EstablishmentMost Brassica species grow best on well drainedsoils with a pH range of 5.5–8.5. Brassicas do notgrow well on poorly drained soils, especially duringestablishment.Winter cover crops should be estab-lished as early as possible. A good rule of thumbis to establish brassicas about 4 weeks prior to theaverage date of the first 28° F freeze. The minimumsoil temperature for planting is 45° F; the maximumis 85° F.

Winter hardinessSome brassicas and most mustards may winterkill,depending on climate and species. Forage radishnormally winter kills when air temperatures dropbelow 23° F for several nights in a row.Winter har-diness is higher for most brassicas if plants reacha rosette stage between six to eight leaves beforethe first killing frost.Some winter-type cultivars of rapeseed are

able to withstand quite low temperatures (10° F)(352).


Late planting will likely result in stand failureand will certainly reduce biomass production andnutrient scavenging. Planting too early, however,may increase winterkill in northern zones (166).In Washington (Zone 6), canola and rapeseed

usually overwinter,mustards do not. Recent workwith arugula (Eruca sativa) shows that it doesoverwinter and may provide similar benefits asthe mustards (430).In Michigan, mustards are planted in mid-

August, and winterkill with the first hard frost,usually in October.When possible, plant anotherwinter cover crop such as rye or leave strips ofuntilled brassica cover crop rather than leave thesoil without growing cover over the winter (391).In Maine, all brassica and mustards used as

cover crops winterkill (166).

Winter vs. spring annual useBrassica and mustard cover crops can be plantedin spring or fall. Some species can be managed towinterkill, leaving a mellow seedbed requiring lit-tle or no seedbed preparation. For the maximumbenefits offered by brassicas as cover crops, fall-planting is usually preferable because plantingconditions (soil temperature and moisture) aremore reliable and the cover crops produce moredry matter.In Maryland, rapeseed and forage radish were

more successful as winter- rather than spring-annual cover crops.The early spring planted bras-sicas achieved about half the quantities ofbiomass and did not root as deeply,before boltingin spring (432).In Michigan,mustards can be planted in spring

following corn or potatoes or in fall into wheatresidue or after snap beans. Fall seedings needabout 900 growing-degree-days to produceacceptable biomass,which is usually incorporatedat first frost (usually October). Spring seeding isless reliable due to cool soil temperatures, and itsuse is limited mostly to late-planted vegetablecrops (391).In Maine, brassicas are either planted in late

summer after the cash crop and winterkill,or theyare spring-seeded for a summer cover crop (166).Rapeseed planted in late spring to summer has

been used with some success in the mid-Atlantic

region to produce high biomass for incorporationto biofumigate soil for nematodes and diseasesprior to planting strawberries and fruit trees.

Mixtures. Mix with small grains (oats, rye), otherbrassicas or legumes (e.g.clover).Brassicas are verycompetitive and can overwhelm the other speciesin the mixture.The seeding rate must be adjustedso ensure adequate growth of the companionspecies.Consult local expertise and start with smallplots or experiment with several seeding rates.Washington farmers use mixtures of white and

brown mustard, usually with a greater proportionof brown mustard.In Maryland and Pennsylvania, farmers and

researchers seed the small grain and forage radishin separate drill rows rather than mixing the seed.This is done by taping closed alternate holes inthe two seeding boxes of a grain drill with bothsmall seed and large seed boxes.Two rows of oatsbetween each row of forage radish has alsoproven successful (432). Rye (sown at 48 lb./A)can be grown successfully as a mixture with win-ter-killing forage radish (13 lb./A).

KillingBrassica cover crops that do not winterkill canbe terminated in spring by spraying with anappropriate herbicide, mowing, and/or incorpo-rating above-ground biomass by tillage beforethe cover crop has reached full flower. Rollingmay also be used to kill these covers if they arein flower.Rapeseed has proved difficult to kill with

glyphosate, requiring a higher than normal rate ofapplication—at least 1 quart/acre of glyphosate—and possibly multiple applications. Radish, mus-tard, and turnip can be killed using a full rate ofparaquat, multiple applications of glyphosate, orglyphosate plus 1pt/acre 2,4-D.In Alabama and Georgia, brassica cover crops

were reportedly harder to chemically kill thanwinter cereals.Timely management and multipleherbicide applications may be necessary for suc-cessful termination. If not completely killed, rape-seed volunteers can be a problem in thesubsequent crop. Always check herbicide rota-tion restrictions before applying.


Another no-till method for terminating maturebrassicas is flail mowing. Be sure to evenly dis-tribute residue to facilitate planting operationsand reduce allelopathic risk for cash crop. Asmentioned above, many producers incorporatebrassica residues using conventional tillage meth-ods to enhance soil biotoxic activity especially inplasticulture systems.Brassica pest suppression may be more effec-

tive if the cover crop is incorporated.

Seed and PlantingBecause Brassica spp. seed may be scarce, it isbest to call seed suppliers a few months prior toplanting to check on availability.Brassica seeds ingeneral are relatively small;a small volume of seedgoes a long way.• Rapeseed (Canola).Drill 5-10 lb./A no deeperthan ¾ in. or broadcast 8–14 lb./A.

• Mustard.Drill 5-12 lb./A ¼–¾ in. deep orbroadcast 10-15 lb./A.

• Radish.Drill 8 to 12 lb/A.¼–½ in. deep, orbroadcast 12-20 lb./A. Plant in late summer orearly fall after the daytime average tempera-ture is below 80° F.

• Turnip.Drill 4-7 lb./A about ½ in. deep orbroadcast 10-12 lb./A. Plant in the fall after thedaytime average temperature is below 80° F.

Nutrient ManagementBrassicas and mustards need adequate nitrogenand sulfur fertility. Brassica sulfur (S) nutritionneeds and S uptake capacity exceed those ofmany other plant species, because S is requiredfor oil and glucosinolate production. A 7:1 N/Sratio in soils is optimum for growing rape, whileN/S ratios ranging from 4:1 to 8:1 work well forbrassica species in general.Ensuring sufficient N supply to brassicas during

establishment will enhance their N uptake andearly growth. Some brassicas, notably rape, canscavenge P by making insoluble P more availableto them via the excretion of organic acids in theirroot zone (168).Brassicas decompose quickly. Decomposition

and nutrient turnover from roots (C:N ratios 20-30) is expected to be slower than that fromshoots (C:N ratios 10-20), but overall faster than

that of winter rye. A winter-killed radish covercrop releases plant available nitrogen especiallyearly in spring, so it should be followed by anearly planted nitrogen demanding crop to avoidleaching losses (432).

COMPARATIVE NOTES

Canola is more prone to insect problems thanmustards, probably because of its lower concen-tration of glucosinolates.In the Salinas Valley, which has much milder

summer and winter temperatures than theCentral Valley of California, brassica cover cropsare generally less tolerant of suboptimal condi-tions (i.e. abnormally low winter temperatures,low soil nitrogen, and waterlogging), and henceare more likely to produce a nonuniform standthan other common cover crops (45).

▼ Precautions. The use of brassicas for pestmanagement is in its infancy. Results are inconsis-tent from year to year and in different geographicregions. Be sure to consult local expertise andbegin with small test plots on your farm.Bio-toxic activity can stunt cash crop growth,

thus avoid direct planting into just-killed greenresidue.Brassica cover crops should NOT be planted in

rotation with other brassica crops such as cab-bage, broccoli, and radish because the latter aresusceptible to similar diseases. Also, scatteredvolunteer brassica may appear in subsequentcrops. Controlling brassica cover crop volunteersthat come up in brassica cash crops would bechallenging if not impossible.Black mustard (Brassica nigra) is hardseeded

and could cause weed problems in subsequentcrops (39).Rapeseed contains erucic acid and glucosino-

lates, naturally occurring internal toxicants.Thesecompounds are anti-nutritional and are a concernwhen feeding to livestock. Human consumptionof brassicas has been linked to reducing inci-dence of cancer. All canola cultivars have beenimproved through plant breeding to contain lessthan 2% erucic acid.

Buckwheat is the speedy short-seasoncover crop. It establishes, blooms andreaches maturity in just 70 to 90 days and

its residue breaks down quickly. Buckwheat sup-presses weeds and attracts beneficial insects andpollinators with its abundant blossoms. It is easyto kill, and reportedly extracts soil phosphorusfrom soil better than most grain-type covercrops.Buckwheat thrives in cool, moist conditions

but it is not frost tolerant. Even in the South, it isnot grown as a winter annual. Buckwheat is notparticularly drought tolerant, and readily wiltsunder hot, dry conditions. Its short growing sea-son may allow it to avoid droughts, however.

BENEFITS

Quick cover. Few cover crops establish as rapid-ly and as easily as buckwheat. Its rounded pyra-mid-shaped seeds germinate in just three to fivedays. Leaves up to 3 inches wide can developwithin two weeks to create a relatively dense,soilshading canopy. Buckwheat typically producesonly 2 to 3 tons of dry matter per acre,but it doesso quickly—in just six to eight weeks (257).Buckwheat residue also decomposes quickly,releasing nutrients to the next crop.

Weed suppressor. Buckwheat’s strong weed-suppressing ability makes it ideal for smothering

BUCKWHEAT

summer or cool-season annualtoo dry, cool

Fagopyrum esculentum

Type: summer or cool-seasonannual broadleaf grain

Roles: quick soil cover, weed sup-pressor, nectar for pollinators andbeneficial insects, topsoil loosener,rejuvenator for low-fertility soils

Mix with: sorghum-sudangrasshybrids, sunn hemp



Winter rape is a host for root lesion nematode.In a SARE funded study inWashington, root lesionnematode populations were 3.8 times higher inthe winter rape treatment than in the white mus-tard and no green manure treatments after greenmanure incorporation in unfumigated plots.However, populations in the unfumigated winterrape treatment were below the economic thresh-old both years of the study. For more information,

go to www.sare.org/projects/ and search forSW95-021. See also SW02-037).Rapeseed may provide overwintering sites for

harlequin bug in Maryland (432).

Contributors: Guihua Chen, Andy Clark,Amy Kremen,Yvonne Lawley, Andrew Price,Lisa Stocking, RayWeil

BUCKWHEAT 91

warm-season annual weeds. It’s also planted afterintensive, weed-weakening tillage to crowd outperennials.A mix of tillage and successive denseseedings of buckwheat can effectively suppressCanada thistle, sowthistle, creeping jenny, leafyspurge, Russian knapweed and perennial pepper-grass (257). While living buckwheat may have anallelopathic weed-suppressing effect (351), its pri-mary impact on weeds is through shading andcompetition.

Phosphorus scavenger. Buckwheat takes upphosphorus and some minor nutrients (possiblyincluding calcium) that are otherwise unavailableto crops, then releasing these nutrients to latercrops as the residue breaks down. The roots ofthe plants produce mild acids that release nutri-ents from the soil. These acids also activateslow-releasing organic fertilizers, such as rockphosphate. Buckwheat’s dense,fibrous roots clus-ter in the top 10 inches of soil,providing an exten-sive root surface area for nutrient uptake.

Thrives in poor soils. Buckwheat performsbetter than cereal grains on low-fertility soils andsoils with high levels of decaying organic matter.That’s why it was often the first crop planted oncleared land during the settlement of woodlandareas and is still a good first crop for rejuvenatingover-farmed soils. However, buckwheat does notdo well in compacted, droughty or excessivelywet soils.

Quick regrowth. Buckwheat will regrow aftermowing if cut before it reaches 25 percentbloom. It also can be lightly tilled after themidpoint of its long flowering period to reseed asecond crop. Some growers bring new land intoproduction by raising three successive buck-wheat crops this way.

Soil conditioner. Buckwheat’s abundant, fineroots leave topsoil loose and friable after only min-imal tillage,making it a great mid-summer soil con-ditioner preceding fall crops in temperate areas.

Nectar source. Buckwheat’s shallow white blos-soms attract beneficial insects that attack or para-

sitize aphids,mites and other pests.These benefi-cials include hover flies (Syrphidae), predatorywasps, minute pirate bugs, insidious flower bugs,tachinid flies and lady beetles. Flowering maystart within three weeks of planting and continuefor up to 10 weeks.

Nurse crop. Due to its quick, aggressive start,buckwheat is rarely used as a nurse crop,although it can be used anytime you want quickcover. It is sometimes used to protect late-fallplantings of slow-starting, winter-hardy legumeswherever freezing temperatures are sure to killthe buckwheat.

MANAGEMENT

Buckwheat prefers light to medium,well-drainedsoils—sandy loams, loams, and silt loams. It per-forms poorly on heavy,wet soils or soils with highlevels of limestone. Buckwheat grows best incool, moist conditions, but is not frost-tolerant. Itis also not drought tolerant. Extreme afternoonheat will cause wilting, but plants bounce backovernight.

EstablishmentPlant buckwheat after all danger of frost. Inuntilled, minimally tilled or clean-tilled soils, drill50 to 60 lb./A at 1/2 to 11/2 inches deep in 6 to 8

BUCKWHEAT (Fagopyrum esculentum)

MarianneSarrantonio


inch rows. Use heavier rates for quicker canopydevelopment. For a fast smother crop, broadcastup to 96 lb./A (2 bu./A) onto a firm seedbed andincorporate with a harrow, tine weeder, disk orfield cultivator. Overall vigor is usually better indrilled seedings. As a nurse-crop for slow-

growing, winter annuallegumes planted in latesummer or fall, seed atone-quarter to one-thirdof the normal rate.Buckwheat compen-

sates for lower seedingrates by developingmore branches per plantand more seeds per blos-som. However, skimpingtoo much on seedmakes stands more vul-nerable to early weed

competition until the canopy fills in. Usingcleaned, bin-run or even birdseed-grade seed canlower establishment costs, but increases the riskof weeds.As denser stands mature, stalks becomespindly and are more likely to lodge from wind orheavy rain.

RotationsBuckwheat is used most commonly as a mid-sum-mer cover crop to suppress weeds and replacebare fallow. In the Northeast and Midwest, it isoften planted after harvest of early vegetable crops,then followed by a fall vegetable, winter grain, orcool-season cover crop. Planted later,winterkilledresidue provides decent soil cover and is easy tono-till into. In many areas, it can be planted fol-lowing harvest of winter wheat or canola.In parts of California, buckwheat grows and

flowers between the killing of winter annuallegume cover crops in spring and their re-estab-lishment in fall. Some California vineyard man-agers seed 3-foot strips of buckwheat in rowmiddles, alternating it and another summer covercrop, such as sorghum-sudangrass.

Buckwheat is sensitive to herbicide residuesfrom previous crops, especially in no-tillseedbeds. Residue from trifluralin and from tri-azine and sulfonylurea herbicides have damagedor killed buckwheat seedlings (79). When indoubt, sow and water a small test plot of the fast-germinating seed to detect stunting or mortality.

Pest ManagementFew pests or diseases bother buckwheat. Its mostserious weed competitors are often small grainsfrom preceding crops, which only add to thecover crop biomass. Other grass weeds can be aproblem, especially in thin stands.Weeds also canincrease after seed set and leaf drop. Diseasesinclude a leaf spot caused by the fungusRamularia and Rhizoctonia root rot.

Other OptionsPlant buckwheat as an emergency cover crop toprotect soil and suppress weeds when your maincrop fails or cannot be planted in time due tounfavorable conditions.To assure its role as habitat for beneficial

insects, allow buckwheat to flower for at least 20days—the time needed for minute pirate bugs toproduce another generation.Buckwheat can be double cropped for grain

after harvesting early crops if planted by mid-Julyin northern states or by early August in the South.It requires a two-month period of relatively cool,moist conditions to prevent blasting of the blos-soms. There is modest demand for organic andspecially raised food-grade buckwheat in domes-tic and overseas markets. Exporters usuallyspecify variety, so investigate before plantingbuckwheat for grain.

Management CautionsBuckwheat can become a weed.Kill within 7 to 10days after flowering begins, before the first seedsbegin to harden and turn brown.Earliest maturingseed can shatter before plants finish blooming.Some seed may overwinter in milder regions.Buckwheat can harbor insect pests including

Lygus bugs,tarnished plant bugs and Pratylynchuspenetrans root lesion nematodes (256).

Buckwheat

germinates and

grows quickly,

producing 2 to 3

tons of dry

matter in just

6 to 8 weeks.

OATS 93

COMPARATIVE NOTES

• Buckwheat has only about half the root massas a percent of total biomass as small grains(355). Its succulent stems break down quickly,leaving soils loose and vulnerable to erosion,particularly after tillage. Plant a soil-holdingcrop as soon as possible.

• Buckwheat is nearly three times as effective asbarley in extracting phosphorus, and morethan 10 times more effective than rye—thepoorest P scavenger of the cereal grains (355).

• As a cash crop, buckwheat uses only half asmuch soil moisture as soybeans (299).


If you need a low-cost,reliable fall cover that win-terkills inHardiness Zone 6 and colder andmuchof Zone 7, look no further. Oats provide quick,

weed-suppressing biomass,take up excess soil nutri-ents and can improve the productivity of legumeswhen planted in mixtures.The cover’s fibrous rootsystem also holds soil during cool-weather gaps inrotations, and the ground cover provides a mellowmulch before low-till or no-till crops.An upright, annual grass,oats thrive under cool,

moist conditions on well-drained soil. Plants canreach heights in excess of 4 feet. Stands generallyfare poorly in hot, dry weather.

BENEFITS

You can depend on oats as a versatile,quick-grow-ing cover for many benefits:

Affordable biomass.With good growing condi-tions and sound management (including timelyplanting), expect 2,000 to 4,000 pounds of drymatter per acre from late-summer/early fall-seed-ed oats and up to 8,000 pounds per acre fromspring stands.

Nutrient catch crop. Oats take up excess N andsmall amounts of P and K when planted early

OATS

nonsummer use

cool season annual

Avena sativa

Also called: spring oats

Type: cool season annual cereal

Roles: suppress weeds, preventerosion, scavenge excess nutrients,add biomass, nurse crop

Mix with: clover, pea, vetch, otherlegumes or other small grains



enough. Late-summer plantings can absorb asmuch as 77 lb. N/A in an eight- to ten-week peri-od, studies in the Northeast and Midwest haveshown (313, 329).Where the plant winterkills, some farmers use

oats as a nitrogen catch crop after summerlegume plowdowns, to hold some N over winterwithout needing to kill the cover in spring. Some

of the N in the win-terkilled oats may still belost by spring, eitherthrough denitrificationinto the atmosphere orby leaching from the soilprofile. Consider mixingoats with an overwinter-ing legume if your objec-tive is to maximize Ncontribution to the nextcrop.

Smother crop. Quick to germinate, oats are agreat smother crop that outcompetes weeds andalso provides allelopathic residue that can hindergermination of many weeds—and some crops (seebelow)—for a few weeks. Reduce crop sup-pression concerns by waiting two- to three weeksafter killing oats before planting a subsequent crop.

Fall legume nurse crop. Oats have few equalsas a legume nurse crop or companion crop.Theycan increase the fertilizer replacement value oflegumes.Adding about 35 to 75 lb. oats/A to theseeding mix helps slow-establishing legumes suchas hairy vetch, clovers or winter peas, whileincreasing biomass. It also helps reduce fallweeds. The oats will winterkill in many areaswhile improving the legume’s winter survival.

Spring green manure or companion crop.Spring-seeded with a legume, oats can providehay or grain and excellent straw in the NorthernU.S., while the legume remains as a summer—oreven later—cover. There’s also a haylage optionwith a fast-growing legume if you harvest whenoats are in the dough stage.The oats will increasethe dry matter yield and boost the total protein,

but, because of its relatively high nitrogen con-tent, could pose a nitrate-poisoning threat to live-stock, especially if you delay harvesting until oatsare nearing the flowering stage.The climbing growth habit of some viny

legumes such as vetch can contribute to lodgingand make oat grain harvest difficult. If you’regrowing the legume for seed,the oats can serve asa natural trellis that eases combining.

MANAGEMENT

Establishment & FieldworkTime seeding to allow at least six to 10 weeks ofcool-season growth. Moderately fertile soil givesthe best stands.

Late-summer/early-fall planting. For a win-terkilled cover, spring oats usually are seeded inlate summer or early fall in Zone 7 or colder.Broadcasting or overseeding will give the bestresults for the least cost,unless seeding into heavyresidue.Cleaned, bin-run seed will suffice.If broadcasting and you want a thick win-

terkilled mulch, seed at the highest locally recom-mended rate (probably 3 to 4 bushels per acre) atleast 40 to 60 days before your area’s first killingfrost.Assuming adequate moisture for quick ger-mination, the stand should provide some soil-pro-tecting, weed-suppressing mulch.Disk lightly to incorporate. In many regions,

you’ll have the option of letting it winterkill orsending in cattle for some fall grazing.If seeding oats as a fall nurse crop for a legume,

a low rate (1 to 2 bushels per acre) works well.If drilling oats, seed at 2 to 3 bushels per acre

1/2 to 1 inch deep, or 11/2 inches when growinggrain you plan to harrow for weed control.Shallow seeding in moist soil provides rapid emer-

gence and reduces incidence of root rot disease.Timing is critical when you want plenty of bio-

mass or a thick ground cover. As a winter coverfollowing soybeans in the Northeast or Midwest,overseeding spring oats at the leaf-yellowing orearly leaf-drop stage (and with little residue pre-sent) can give a combined ground cover as highas 80 percent through early winter (200). If you

Oats are a

reliable, low-cost

cover that

winterkill in

Zone 6 and

much of Zone 7.

OATS 95

wait until closer to or after soybean harvest, how-ever, you’ll obtain much less oat biomass to helpretain bean residue, Iowa and Pennsylvania stud-ies have shown.Delaying planting by as little as twoweeks in late

summer also can reduce the cover’s effectivenessas a spring weed fighter, a study in upstate NewYork showed. By spring, oat plots that had beenplanted on August 25 had 39 percent fewer weedplants and one-seventh the weed biomass of con-trol plots with no oat cover,while oats planted twoweeks later had just 10 percent fewer weed plantsin spring and 81 percent of the weed biomass ofcontrol plots (329,330).

No-hassle fieldwork. As a winterkilled cover,just light disking in spring will break up the brit-tle oat residue. That exposes enough soil forwarming and timely planting. Or, no-till directlyinto the mulch, as the residue will decomposereadily early in the season.

Winter planting. As a fall or winter cover cropin Zone 8 or warmer, seed oats at low to mediumrates. You can kill winter-planted oats with springplowing,or with herbicides in reduced-tillage sys-tems.

Spring planting. Seeding rate depends on yourintended use: medium to high rates for a springgreen manure and weed suppressor, low rates formixtures or as a legume companion crop.Higherrates may be needed for wet soils or thickerground cover. Excessive fertility can encouragelodging, but if you’re growing oats just for itscover value,that can be an added benefit for weedsuppression and moisture conservation.

Easy to kill. Oats will winterkill in most of zone7 or colder.Otherwise,kill by mowing or sprayingsoon after the vegetative stage,such as the milk orsoft dough stage. In no-till systems, rolling/crimp-ing will also work (best at dough stage or later).See Cover Crop Roller Design Holds Promise ForNo-Tillers, p. 146. If speed of spring soil-warmingis not an issue,you can spray or mow the oats andleave on the soil surface for mulch.

If you want to incorporate the stand, allowat least two to three weeks before planting thenext crop.Killing too early reduces the biomass potential

and you could see some regrowth if killingmechanically. But waiting too long could maketillage of the heavier growth more difficult in aconventional tillage system and could deplete soilmoisture needed for the next crop.Timely killingalso is important because mature oat stands cantie up nitrogen.

Pest ManagementAllelopathic (naturally occurring herbicidal)compounds in oat roots and residue can hinderweed growth for a few weeks.These compoundsalso can slow germination or root growth of somesubsequent crops, such as lettuce, cress, timothy,rice,wheat and peas.Minimize this effect by wait-ing three weeks after oat killing before seeding asusceptible crop, or by following with an alter-nate crop. Rotary hoeing or other pre-emergemechanical weeding of solo-seeded oats canimprove annual broadleaf control.Oats are less prone to insect problems than

wheat or barley. If you’re growing oats for grain orforage, armyworms, various grain aphids andmites, wireworms, cutworms, thrips, leafhoppers,grubs and billbugs could present occasionalproblems.

OATS (Avena sativa)

MarianneSarrantonio


Bryan and Donna Davis like what cover cropshave done for their corn/soybean rotation.They use less grass herbicide, have appliedinsecticides only once in the last six years, andthey have seen organic matter content almostdouble from less than 2% to almost 4%.Rye and oats are the cover crop mainstays on

the nearly 1,000 acres they farm near Grinnell,Iowa.Bryan and Donna purchased the farm—inthe family since 1929—in 1987 and almost im-mediately put most of the operation under 100%no-till,a system they had experimented with overthe years.They now till some acres and are also inthe process of transitioning 300 acres to organic.Moving 1/3 of their acreage toward organic

seems the logical culmination of the Davis’makeover of their farm that started with adesire to“get away from the chemicals.” Thatwas what motivated them to start using covercrops to feed the soil and help manage pests.“We were trying to get away from the idea

that every bug and weed must be exterminated.Rather,we need to‘manage’ the system andtolerate some weed and insect pressure. It shouldbe more of a balance,”says Bryan.Bryan and Donna are practitioners and

proponents of “biological farming,” a systemsapproach based on such principles as feedingthe soil to keep it biologically active, reducingchemical inputs and paying attention to traceelements or micronutrients in order tomaintain balance in the system.Cover cropsplay an integral role in this system.They seed oats at 2-3 bu/A in spring or fall,

depending on time and labor availability.Donnadoes most of the combining and planting,buteven with a lot of acres for two people tomanage,cover crops are a high priority on theirschedule.Fall-seeded oats are planted aftersoybean harvest and“need rain on them soonafter planting to get them started.” They’ll put onabout a foot of growth before winterkilling,usually in December in their south-central Iowaconditions.

Spring oats are broadcast in mid or late Marchwith a fertilizer cart and then rotary harrowed.Ifgoing back to corn,they seed at a heavier,3.5 burate,expecting only about 5 or 6 weeks of growthbefore they work down the cover crop with a soilfinisher and plant corn in early May.For soybeans,they either kill chemically and no-till the beans,orwork down and seed conventionally.They have managed rye in different ways over

the years depending on its place in the rotation,but prefer to seed into killed or tilled rye ratherthan a living cover crop.They figure that they getabout 35 lb.N from oats and up to 60 lb.from rye.On their organic transition acres they are

applying chicken manure (2 tons/A), andcover crops are crucial to sopping up excessnutrients and crowding out the weeds thatcrop up in response to the extra nutrients.They feel that their efforts to balance nutrientsare also helping with weed control, becauseweeds feed on nutrient imbalances.In addition to the increase in soil organic

matter,attributed to cover crops and no-tillage,they’ve also seen improvements in soil moistureand infiltration.Fields that used to pond afterheavy rains no longer do.Soybeans are weatheringdrought better,and corn stays green longer duringa“more natural”drying down process.“Our system takes more time and is more labor

intensive,but if you look at the whole budget,weare doing much better now.We have cut ourchemical costs dramatically,and have reducedfertility costs—in some fields—by 1/3 to ½,”saysBryan.“With energy costs these days,you can’tafford not to do this.”Davis is careful to note that this is not just

about adding one component such as covercrops.“You need to address the whole system,notjust one piece of the pie.To be able to have asustaining system,you must work with the livingsystem.Feed the soil and give it a roof over itshead.”Cover crops play a crucial role in thatsystem.—Andy Clark

Oats, Rye Feed Soil in Corn/Bean Rotation

OATS 97

Resistant oat varieties can minimize rusts,smuts and blights if they are a concern in yourarea or for your cropping system. Cover cropssuch as oats help reduce root-knot nematodes andvegetable crop diseases caused by Rhizoctonia,results of a producer study in South Carolinashow (448), although brassicas are better. Toreduce harmful nematodes that oats couldencourage, avoid planting oats two years in a rowor after nematode-susceptible small grains such aswheat, rye or triticale (71).

Other OptionsThere are many low-cost, regionally adapted andwidely available oat varieties, so you have hay,straw, forage or grain options. Select for cul-tural and local considerations that best fit yourintended uses. Day-length, stalk height, resistanceto disease, dry matter yield, grain test weight andother traits may be important considerations. Inthe Deep South, fast-growing black oats (Avenastrigosa) look promising as a weed-suppressivecover for soybeans. See Up-and-Coming CoverCrops (p. 191).Aside from their value as a cover crop, oats are

a great feed supplement, says grain and hogfarmer Carmen Fernholz, Madison, Minn.A niche

market for organic oats also could exist in yourarea, he observes.Oats are more palatable than rye and easily

overgrazed. If using controlled grazing in oatstands, watch for high protein levels, which canvary from 12 to 25 percent (434).The potassiumlevel of oat hay also is sometimes very high andcould cause metabolic problems in milking cowsif it’s the primary forage. Underseeding a legumeenhances the forage option for oats by increasingthe biomass (compared with solo-cropped oats)and providing nitrogen for a subsequent crop.

COMPARATIVE NOTES

• Fall brassicas grow faster, accumulate moreN and may suppress weeds, nematodes anddisease better than oats.

• Rye grows more in fall and early spring,absorbs more N and matures faster, but isharder to establish, to kill and to till than oats.

• As a legume companion/nurse crop, oats out-perform most varieties of other cereal grains.

• Oats are more tolerant of wet soil than is bar-ley, but require more moisture.



Secale cereale

Also called: cereal rye, winter rye,grain rye

Type: cool season annual cerealgrain

Roles: scavenge excess N, preventerosion, add organic matter, sup-press weeds

Mix with: legumes, grasses or othercereal grains


• A Maryland study credited rye with holding60 percent of the residual N that could haveleached from a silt loam soil following inten-tionally over-fertilized corn (372).

• A Georgia study estimated rye captured from69 to 100 percent of the residual N after acorn crop (220).

• In an Iowa study, overseeding rye or a rye/oatsmix into soybeans in August limited leachingloss from September to May to less than 5 lb.N/A (313).

Rye increases the concentration of exchangeablepotassium (K) near the soil surface, by bringing itup from lower in the soil profile (123).Rye’s rapid growth (even in cool fall weather)

helps trap snow in winter, further boosting win-terhardiness. The root system promotes betterdrainage, while rye’s quick maturity in spring—compared with other cover crops—can help con-serve late-spring soil moisture.

Reduces erosion. Along with conservationtillage practices, rye provides soil protection onsloping fields and holds soil loss to a tolerablelevel (124).

RYE

The hardiest of cereals, rye can be seededlater in fall than other cover crops and stillprovide considerable dry matter, an exten-

sive soil-holding root system, significant reductionof nitrate leaching and exceptional weed sup-pression. Inexpensive and easy to establish,rye out-performs all other cover crops on infertile,sandy oracidic soil or on poorly prepared land. It is widelyadapted,but grows best in cool, temperate zones.Taller and quicker-growing than wheat, rye can

serve as a windbreak and trap snow or hold rain-fall over winter. It overseeds readily into manyhigh-value and agronomic crops and resumesgrowth quickly in spring, allowing timely killingby rolling, mowing or herbicides. Pair rye with awinter annual legume such as hairy vetch to off-set rye’s tendency to tie up soil nitrogen in spring.

BENEFITS

Nutrient catch crop. Rye is the best cool-seasoncereal cover for absorbing unused soil N. It has notaproot, but rye’s quick-growing, fibrous root sys-tem can take up and hold as much as 100 lb.N/Auntil spring, with 25 to 50 lb. N/A more typical(422). Early seeding is better than late seeding forscavenging N (46).

RYE 99

Fits many rotations. In most regions, rye canserve as an overwintering cover crop after cornor before or after soybeans, fruits or vegetables.It’s not the best choice before a small grain cropsuch as wheat or barley unless you can kill ryereliably and completely, as volunteer rye seedwould lower the value of other grains.Rye also works well as a strip cover crop and

windbreak within vegetables or fruit crops and asa quick cover for rotation gaps or if another cropfails.You can overseed rye into vegetables and tas-

seling or silking corn with consistently goodresults. You also can overseed rye into brassicas(369, 422), into soybeans just before leaf drop orbetween pecan tree rows (61).

Plentiful organic matter. An excellent sourceof residue in no-till and minimum-tillage systemsand as a straw source, rye provides up to 10,000pounds of dry matter per acre, with 3,000 to4,000 pounds typical in the Northeast (118, 361).A rye cover crop might yield too much residue,depending on your tillage system, so be sure yourplanting regime for subsequent crops can handlethis. Rye overseeded into cabbage August 26 cov-ered nearly 80 percent of the between-row plotsby mid-October and, despite some summer heat,already had accumulated nearly half a ton of bio-mass per acre in a NewYork study.By the May 19plowdown, rye provided 2.5 tons of dry matterper acre and had accumulated 80 lb. N/A.Cabbage yields weren’t affected, so competitionwasn’t a problem (329).

Weed suppressor. Rye is one of the best coolseason cover crops for outcompeting weeds,especially small-seeded, light-sensitive annualssuch as lambsquarters, redroot pigweed, vel-vetleaf, chickweed and foxtail. Rye also suppress-es many weeds allelopathically (as a naturalherbicide), including dandelions and Canada this-tle and has been shown to inhibit germination ofsome triazine-resistant weeds (336).Rye reduced total weed density an average of 78

percent when rye residue covered more than 90percent of soil in a Maryland no-till study (410),and

by 99 percent in a California study (422).You canincrease rye’s weed-suppressing effect before no-till corn by planting rye with an annual legumesuch as hairy vetch. Don’t expect complete weedcontrol, however. You’ll probably need comple-mentary weed management measures.

Pest suppressor. While rye is susceptible to thesame insects that attack other cereals, seriousinfestations are rare. Rye reduces insect pestproblems in rotations (448)and attracts significant num-bers of beneficials such aslady beetles (56).Fewer diseases affect rye

than other cereals. Rye canhelp reduce root-knot nema-todes and other harmfulnematodes, research in theSouth suggests (20, 448).

Companion crop/legume mixtures. Sow ryewith legumes or other grasses in fall or overseeda legume in spring. A legume helps offset rye’stendency to tie up N. A legume/rye mixtureadjusts to residual soil N levels. If there’s plenty ofN, rye tends to do better; if there is insufficient N,the legume component grows better, Marylandresearch shows (86). Hairy vetch and rye are apopular mix, allowing an N credit before corn of50 to 100 lb. N/A. Rye also helps protect the lesshardy vetch seedlings through winter.

MANAGEMENT

Establishment & FieldworkRye prefers light loams or sandy soils and will ger-minate even in fairly dry soil. It also will grow inheavy clays and poorly drained soils, and manycultivars tolerate waterlogging (63).Rye can establish in very cool weather. It

will germinate at temperatures as low as 34° F.Vegetative growth requires 38° F or higher (361).

Winter annual use. Seed from late summer tomidfall in Hardiness Zones 3 to 7 and from fall tomidwinter in Zones 8 and warmer. In the Upper

Rye can beplanted laterin fall thanother covercrops.


Midwest and cool New England states,seed two toeight weeks earlier than a wheat or rye grain cropto ensure maximum fall, winter and springgrowth. Elsewhere, your tillage system and theamount of fall growth you prefer will help deter-mine planting date. Early planting increases theamount of N taken up before winter,but can makefield management (especially killing the covercrop and tillage) more difficult in spring. See RyeSmothersWeeds Before Soybeans (p. 104).Rye is more sensitive to seeding depth than other

cereals, so plant no deeper than 2 inches (71).Drill60 to 120 lb./A (1 to 2 bushels) into a preparedseedbed or broadcast 90 to 160 lb./A (1.5 to 3bushels) and disk lightly or cultipack (361,422).If broadcasting late in fall and your scale and

budget allow, you can increase the seeding rate toas high as 300 or 350 lb./A (about 6 bushels) toensure an adequate stand.Rye can be overseed byair more consistently than many other cover crops.“I use a Buffalo Rolling Stalk Chopper to help

shake rye seeds down to the soil surface,” saysSteve Groff, a Holtwood, Pa., vegetable grower.“It’s a very consistent, fast and economical wayto establish rye in fall.” (Groff’s farming systemis described in detail at www.cedarmeadowfarm.com).

Mixed seeding. Plant rye at the lowest locallyrecommended rate when seeding with a legume(361), and at low to medium rates with othergrasses.In a Maryland study,a mix of 42 pounds ofrye and 19 pounds of hairy vetch per acre was theoptimum fall seeding rate before no-till corn on asilt loam soil (81). If planting with clovers, seedrye at a slightly higher rate, about 56 lb. per acre.For transplanting tomatoes into hilly, erosion-

prone soil, Steve Groff fall-seeds a per-acre mix of30 pounds rye, 25 pounds hairy vetch and 10pounds crimson clover. He likes how the three-way mix guarantees biomass, builds soil and pro-vides N.

Spring seeding. Although it’s not a commonpractice, you can spring seed cereals such as ryeas a weed-suppressing companion, relay crop orearly forage. Because it won’t have a chance tovernalize (be exposed to extended cold after ger-

mination), the rye can’t set seed and dies on itsown within a few months in many areas.This pro-vides good weed control in asparagus, says RichdeWilde,Viroqua,Wis.After drilling a large-seeded summer crop such

as soybeans,try broadcasting rye.The cover growswell if it’s a cool spring, and the summer croptakes off as the temperature warms up.Secondarytillage or herbicides would be necessary to keepthe rye in check and to limit the cover crop’s useof soil moisture.

Killing & ControllingNutrient availability concern. Rye grows andmatures rapidly in spring, but its maturity datevaries depending on soil moisture and tempera-ture. Tall and stemmy, rye immobilizes N as itdecomposes.The N tie-up varies directly with thematurity of the rye. Mineralization of N is veryslow, so don’t count on rye’s overwintered Nbecoming available quickly.Killing rye early,while it’s still succulent, is one

way to minimize N tie-up and conserve soil mois-ture. But spring rains can be problematic withrye, especially before an N-demanding crop, suchas corn. Even if plentiful moisture hastens theoptimal kill period, you still might get too muchrain in the following weeks and have significantnitrate leaching, a Maryland study showed (109).Soil compaction also could be a problem if you’remowing rye with heavy equipment.

CEREAL RYE (Secale cereale)

MarianneSarrantonio

RYE 101

Late killing of rye can deplete soil moisture andcould produce more residue than your tillage sys-tem can handle.For no-till corn in humid climates,however, summer soil-water conservation bycover crop residues often was more importantthan spring moisture depletion by growing covercrops,Maryland studies showed (82, 84, 85).

Legume combo maintains yield. One way tooffset yield reductions from rye’s immobilizationof N would be to increase your N application.Here’s another option: Growing rye with alegume allows you to delay killing the covers by afew weeks and sustain yields, especially if thelegume is at least half the mix. This gives thelegume more time to fix N (in some cases dou-bling the N contribution) and rye more time toscavenge a little more leachable N. Base the killdate on your area’s normal kill date for a purestand of the legume (109).A legume/rye mix generally increases total dry

matter, compared with a pure rye stand.The high-er residue level can conserve soil moisture. Forbest results, wait about 10 days after killing thecovers before planting a crop.This ensures ade-quate soil warming, dry enough conditions forplanter coulters to cut cleanly and minimizesallelopathic effects from rye residue (84, 109). Ifusing a herbicide, you might need a higher sprayvolume or added pressure for adequate coverage.Legume/rye mixes can be rolled once the legumeis at full bloom (303).

Kill before it matures. Tilling under rye usu-ally eliminates regrowth,unless the rye is less than12 inches tall (361, 422). Rye often is plowed ordisked in the Midwest when it’s about 20 inchestall (307). Incorporating the rye before it’s 18 in.high could decrease tie-up of soil N (361, 422). InPennsylvania (118) and elsewhere, kill at least 10days before planting corn.For best results when mow-killing rye, wait

until it has begun flowering.A long-day plant, ryeis encouraged to flower by 14 hours of daylightand a temperature of at least 40° F. A sickle barmower can give better results than a flail mower,which causes matting that can hinder emergenceof subsequent crops (116).

Mow-kill works well in the South after ryesheds pollen in late April (101). If soil moisture isadequate, you can plant cotton three to five daysafter mowing rye when row cleaners are used inreduced-tillage systems.Some farmers prefer to chop or mow rye by

late boot stage,before it heads orflowers. “If rye getsaway from you,you’d be better offbaling it or harvest-ing it for seed,”cautions southernIllinois organic grainfarmer Jack Erisman(38). He often over-winters cattle in ryefields that precede soybeans. But he prefers thatsoil temperature be at least 60° F before plantingbeans, which is too late for him to no-till beansinto standing rye.“If rye is at least 24 inches tall, I control it with

a rolling stalk chopper that thoroughly flattensand crimps the rye stems,” says Pennsylvania veg-etable grower Steve Groff. “That can sometimeseliminate a burndown herbicide, depending onthe rye growth stage and next crop.”A heavy duty rotavator set to only 2 inches

deep does a good job of tilling rye, says Rich deWilde,Viroqua,Wis.Can’t delay a summer planting by a few weeks

while waiting for rye to flower? If early rye culti-vars aren’t available in your area and you’re inZone 5 or colder, you could plow the rye and usesecondary tillage. Alternately, try a knockdownherbicide and post-emergent herbicide or spot-spraying for residual weed control.For quicker growth of a subsequent crop such

as corn or soybeans, leave the residue uprightafter killing (rather than flat). That hastens cropdevelopment—unless it’s a dry year—via warmersoil temperatures and a warmer seed zone,according to a three-year Ontario study (146).This rarely influences overall crop yield, however,unless you plant too early and rye residue or lowsoil temperature inhibits crop germination.

Rye is the best

cool-season cover

crop for scavenging

N, typically carrying

25 to 50 lb. N/A

over to spring.


Cereal Rye: Cover Crop Workhorse

Talk to farmers across America about covercrops and you’ll find that most of them haveplanted a cereal rye cover crop. Almostcertainly the most commonly planted covercrop, cereal rye can now be seen growing onmillions of acres of farmland each year.There are almost as many ways to manage

cover crop rye as there are farmers using it.Climate, production system, soil type,equipment and labor are the principal factorsthat will determine how you manage rye.Yourown practical experience will ultimatelydetermine what works best for you.Check out how others are managing rye in

this book, on theWeb and around your region.Test alternatives management practices thatallow you to seed earlier or manage covercrop residue differently. Add a legume, abrassica or another grass to increase diversityon your farm.Reasons for rye’s widespread use include:

• It is winter-hardy, allowing it to grow longerinto fall and resume growth earlier in thespring than most other cover crops.

• It produces a lot of biomass,which trans-lates into a long-lasting residue cover in con-servation tillage systems.

• It crowds out and out-competes winterannual weeds,while rye residue helps sup-press summer weeds.

• It scavenges nutrients—particularly nitrogen—very effectively, helping keep nutrients onthe farm and out of surface and groundwater.

• It is relatively inexpensive and easy to seed.• It works well in mixtures with legumes,resulting in greater biomass production andmore complete fall/winter ground cover.

• It can be used as high-quality forage, eithergrazed or harvest as ryelage.

• It can fit into many different crop and live-stock systems, including corn/soybean rota-tions, early or late vegetable crops, and dairyor beef operations.

Fall management (planting):• While results are best if you plant rye byearly fall, it also can be planted inNovember or December in much of thecountry—even into January in the deepSouth—and still provide tangible benefits.

• It can be drilled or broadcast after maincrop harvest,with or without cultivation.

• It can be seeded before main crop harvest,usually by broadcasting, sometimes by planeor helicopter, and in northern climates, atlast cultivation of the cash crop. Soil mois-ture availability is crucial to many of thesepre-harvest seeding methods,either for ger-mination of the cover crop or to avoid com-petition for water with the main crop.

Spring management (termination) is evenmore diverse:• Rye can be killed with tillage,mowing,rolling or spraying.

• It can be killed before or after planting thecash crop,which can be drilled into stand-ing cover crops in conservation tillagesystems.

• Some want to leave rye growing as long aspossible; others insist on terminating it assoon as possible in spring.

• Vegetable growers may leave walls of stand-ing rye all season long between crop rows,usually to alleviate wind erosion.

Some examples of rye management wisdomfrom practitioners around the country:• Pat Sheridan Jr., Fairgrove,Mich.Continuousno-till corn, sugar beets, soybeans, drybeans:“In late August,we fly rye into stand-ing corn (or soybeans if we’re coming backwith soybeans the following year).Welearned that rye is easier to burn downwhen it’s more than two feet tall thanwhen it has grown only a foot or less.”

• Barry Martin,Hawksville,Ga. Peanuts andcotton.“After cotton, in late October or

RYE 103

Pest ManagementThick stands ensure excellent weedsuppression.To extend rye’s weed-managementbenefits, you can allow its allelopathic effects topersist longer by leaving killed residue on the sur-face rather than incorporating it. Allelopathiceffects usually taper off after about 30 days.Afterkilling rye, it’s best to wait three to four weeksbefore planting small-seeded crops such as car-rots or onions. If strip tilling vegetables into rye,be aware that rye seedlings have more allelopath-ic compounds than more mature rye residue.Transplanted vegetables, such as tomatoes, andlarger-seeded species, especially legumes, are lesssusceptible to rye’s allelopathic effects (117).In an Ohio study,use of a mechanical under-cut-

ter to sever roots when rye was at mid- to latebloom—and leaving residue intact on the soil sur-face (as whole plants)—increased weed suppres-sion, compared with incorporation or mowing.The broadleaf weed reduction was comparable tothat seen when sickle-bar mowing, and betterthan flail-mowing or conventional tillage (96).If weed suppression is an important objective

when planting a rye/legume mixture, plant earlyenough for the legume to establish well. Other-wise, you’re probably better off with a pure stand.Overseeding may not be cost-effective before acrop such as field corn,however. A mix of rye and

bigflower vetch (a quick-establishing, self-seed-ing, winter-annual legume that flowers andmatures weeks ahead of hairy vetch) can sup-press weeds signifi-cantly more thanrye alone, whilealso allowing high-er N accumulations(110).“Rye can provide

the best and clean-est mulch youcould want if it’s cut or baled in spring before pro-ducing viable seed,” says Rich de Wilde. Rye canbecome a volunteer weed if tilled before it’s 8inches high, however, or if seedheads start matur-ing before you kill it. Minimize regrowth by wait-ing until rye is at least 12 inches high beforeincorporating or by mow-killing after floweringbut before grain fill begins.

Insect pests rarely a problem. Rye can reduceinsect pest problems in crop rotations, southernresearch suggests (448). In a number of mid-Atlantic locations, Colorado potato beetles havebeen virtually absent in tomatoes no-till trans-planted into a mix of rye/vetch/crimson clover,perhaps because the beetles can’t navigatethrough the residue.

November,we use a broadcast spreader(two bushels of rye per acre), then shred ormow to cover the seed.We usually getenough moisture in November andDecember for germination. After peanuts,we use a double disc grain drill (1.5 bushelsof rye per acre) in mid-September to mid-October.”

• Bryan and Donna Davis,Grinell, Iowa.Corn,soybeans, hay.“We tried to no-till corn andbeans into rye three feet tall, but failed.TheC:N ratio was way out of whack.The cornlooked like it had been sprayed. If you don’tkill before planting, you will invite insects.”See also Oats, Rye Feed Soil in Corn/BeanRotation, p. 96.

• Ed Quigley, Spruce Creek,PA.Dairy.“We seedcereal rye (two bushels per acre) immediate-ly after corn silage.We allow as much springgrowth as possible up to about 10 inches, atwhich point it becomes more difficult to kill,especially with cool/overcast conditions.Wewill also wait to make rylage in spring if weneed feed, and then plant corn a bit later.”

In some areas, farmers substitute other smallgrain cover crops for rye.They are doing so tobetter fit their particular niches, better managetheir systems, or to cut costs by saving smallgrain seeds.Wheat is a popular alternative torye. Look around and experiment!—Andy Clark

Rye can effectively

suppress weeds by

shading, competition

and allelopathy.


Rye Smothers Weeds Before Soybeans

An easy-to-establish rye cover crop helpsNapoleon,Ohio, farmer Rich Bennett enrich hissandy soil while trimming input costs in no-tillsoybeans. Bennett broadcasts rye at 2 bushelsper acre on corn stubble in late October. Heincorporates the seed with a disc and roller.The rye usually breaks through the ground

but shows little growth before winterdormancy. Seeded earlier in fall, rye wouldprovide more residue than Bennett prefersby bean planting—and more effort to kill thecover.“Even if I don’t see any rye in fall, I knowit’ll be there in spring, even if it’s a cold or wetone,”he says.By early May, the rye is usually at least 1.5

feet tall and hasn’t started heading.He no-tillssoybeans at 70 pounds per acre on 30-inchrows directly into standing rye cover crop.Then, depending on the amount of rye growth,he kills the rye with herbicide immediatelyafter planting, or waits for more rye growth.“If it’s shorter than 15 to 18 inches, rye

won’t do a good enough job of shading outbroadleaf weeds,”notes Bennett,who likeshow rye suppresses foxtail, pigweed andlambsquarters.“I sometimes wait up to twoweeks to get more rye residue,”he says.“I kill the rye with 1.5 pints of Roundup

per acre—about half the recommended rate.Adding 1.7 pounds of ammonium sulfate and

13 ounces of surfactant per acre makes iteasier for Roundup to penetrate rye leaves,”he explains.The cover dies in about two weeks.The

slow kill helps rye suppress weeds whilesoybeans establish. In this system,Bennettdoesn’t have to worry about rye regrowing.Roundup Ready® beans have given him

greater flexibility in this system.He used tocultivate beans twice using a Buffalo no-tillcultivator.Now,depending on weed pressure(often giant ragweed and velvetleaf) he willspot treat or spray the whole field once withRoundup. Bennett figures the rye saves him$15 to $30 per acre in material costs andfieldwork, compared with conventional no-tillsystems for soybeans.Rye doesn’t hurt his bean yields, either.

Usually at or above county average, his yieldsrange from 45 to 63 bushels per acre,depending on rainfall, says Bennett.“I really like rye’s soil-saving benefits,”he

says.“Rye reduces our winter wind erosion,improves soil structure, conserves soilmoisture and reduces runoff.”Although hefigures the rye’s restrained growth (from thelate fall seeding) provides only limitedscavenging of leftover N, any that it doesabsorb and hold overwinter is a bonus.Updated in 2007 by Andy Clark

While insect infestations are rarely serious withrye,as with any cereal grain crop occasional prob-lems occur. If armyworms have been a problem,for example, burning down rye before a corncrop could move the pests into the corn. PurdueExtension entomologists note many northeasternIndiana corn farmers reported this in 1997. Croprotations and IPM can resolve most pest problemsyou might encounter with rye.

Few diseases. Expect very few diseases whengrowing rye as a cover crop. A rye-based mulch

can reduce diseases in some cropping systems.No-till transplanting tomatoes into a mix ofrye/vetch/crimson clover, for example,consistent-ly has been shown to delay the onset of earlyblight in several locations in the Northeast. Themulch presumably reduces soil splashing onto theleaves of the tomato plants.If you want the option of harvesting rye as a

grain crop, use of resistant varieties, crop rotationand plowing under crop residues can minimizerust, stem smut and anthracnose.

RYE 105

Other OptionsQuick to establish and easy to incorporate whensucculent, rye can fill rotation gaps in reduced-tillage, semi-permanent bed systems withoutincreasing pest concerns or delaying crop plant-ings, a California study showed (216).Erol Maddox, a Hebron, Md. grower, takes

advantage of rye’s relatively slow decompositionwhen double cropping. He likes transplantingspring cole crops into rye/vetch sod, choppingthe cover mix at bloom stage and letting it layuntil August,when he plants fall cole crops.Mature rye isn’t very palatable and provides

poor-quality forage.It makes high quality hay or bal-age at boot stage,however, or grain can be groundand fed with other grains. Avoid feeding ergot-infected grain because it may cause abortions.Rye can extend the grazing season in late fall

and early spring. It tolerates fall grazing or mow-ing with little effect on spring regrowth in manyareas (210).Growing a mixture of more palatablecover crops (clovers, vetch or ryegrass) canencourage regrowth even further by discouragingovergrazing (329).

Management CautionsAlthough rye’s extensive root system providesquick weed suppression and helps soil structure,

don’t expect dramatic soil improvement from asingle stand’s growth. Left in a poorly drainingfield too long, a rye cover could slow soiland warming even further, delaying crop planti-ng. It’s also not a silver bullet for eliminatingherbicides. Expect to deal with some late-seasonweeds in subsequent crops (410).

COMPARATIVE NOTES

• Rye is more cold- and drought-tolerant thanwheat.

• Oats and barley do better than rye in hotweather.

• Rye is taller than wheat and tillers less. It canproduce more dry matter than wheat and afew other cereals on poor, droughty soils butis harder to burn down than wheat or triticale(241, 361).

• Rye is a better soil renovator than oats (422),but brassicas and sudangrass provide deepersoil penetration (451).

• Brassicas generally contain more N than rye,scavenge N nearly as well and are less likelyto tie up N because they decompose morerapidly.



Sorghum-sudangrass hybrids are unrivaled foradding organic matter to worn-out soils.These tall, fast-growing, heat-loving summer

annual grasses can smother weeds,suppress somenematode species and penetrate compacted sub-soil if mowed once.Seed cost is modest.Followedby a legume cover crop, sorghum-sudangrasshybrids are a top choice for renovating over-farmed or compacted fields.The hybrids are crosses between forage-type

sorghums and sundangrass. Compared with corn,they have less leaf area,more secondary roots anda waxier leaf surface, traits that help them with-stand drought (361). Like corn, they require goodfertility—and usually supplemental nitrogen—forbest growth. Compared with sudangrass, thesehybrids are taller, coarser and more productive.Forage-type sorghum plants are larger, leafier

and mature later than grain sorghum plants.Compared with sorghum-sudangrass hybrids,theyare shorter, less drought tolerant, and don’tregrow as well. Still, forage sorghums as well asmost forms of sudangrass can be used in the samecover-cropping roles as sorghum-sudangrasshybrids. All sorghum- and sudangrass-relatedspecies produce compounds that inhibit certain

plants and nematodes.They are not frost tolerant,and should be planted after the soil warms inspring or in summer at least six weeks before firstfrost.

BENEFITS

Biomass producer. Sorghum-sudangrass grows5 to 12 feet tall with long,slender leaves, stalks upto one-half inch in diameter and aggressive rootsystems. These features combine to produceample biomass, usually about 4,000 to 5,000 lb.DM/A.Up to 18,000 lb.DM/A has been measuredwith multiple cuttings on fertile soils with ade-quate moisture.

Subsoil aerator. Mowing whenever stalks reach3 to 4 feet tall increases root mass five to eighttimes compared with unmowed stalks, and forcesthe roots to penetrate deeper.In addition, tops grow back green and vegeta-

tive until frost and tillering creates up to six new,thicker stalks per plant. A single mowing on NewYork muck soils caused roots to burrow 10 to 16inches deep compared to 6 to 8 inches deep forunmowed plants.The roots of mowed plants frac-

SORGHUM-SUDANGRASS HYBRIDSSorghum bicolor x S. bicolorvar. sudanese

Also called: Sudex, Sudax

Type: summer annual grass

Roles: soil builder, weed andnematode suppressor, subsoilloosener

Mix with: buckwheat, sesbania,sunnhemp, forage soybeans orcowpeas


summer annual

summer annual irrigated

year-round crop

limited by cool temps

SORGHUM-SUDANGRASS HYBRIDS 107

tured subsoil compaction with wormhole-likeopenings that improved surface drainage.However, four mowings at shorter heights causedplants to behave more like a grass and significant-ly decreased the mass, depth and diameter ofroots (277, 450, 451).

Weed suppressor. When sown at higher ratesthan normally used for forage crops, sorghum-sudangrass hybrids make an effective smothercrop. Their seedlings, shoots, leaves and rootssecrete allelopathic compounds that suppressmany weeds. The main root exudate, sor-goleone, is strongly active at extremely low con-centrations, comparable to those of somesynthetic herbicides (370). As early as five daysafter germination, roots begin secreting this alle-lochemical, which persists for weeks and has visi-ble effects on lettuce seedlings even at 10 partsper million (440).Sorghum-sudangrass hybrids suppress such

annual weeds as velvetleaf, large crabgrass, barn-yardgrass (126, 305), green foxtail, smooth pig-weed (190), common ragweed, redroot pigweedand purslane (316). They also suppressed pine(214) and redbud tree seedlings in nursery tests(154). The residual weed-killing effects of theseallelochemicals increased when sorghum-sudan-grass hybrids were treated with the herbicidessethoxydim, glyphosate or paraquat, in descend-ing order of magnitude (144).

Nematode and disease fighter. Plantingsorghum-sudangrass hybrids instead of a hostcrop is a great way to disrupt the life cycles ofmany diseases, nematodes and other pests. Forexample, when sorghum-sudangrass or sorghumalone were no-tilled into endophyte-infected fes-cue pastures in Missouri that had received twoherbicide applications, the disease was controllednearly 100 percent. No-till reseeding with endo-phyte-free fescue completed this cost-effectiverenovation that significantly improved the rate ofgain of yearling steers (16).

Renews farmed-out soils. The combination ofabundant biomass production,subsoiling root sys-

tems, and weed and nematode suppression canproduce dramatic results.On a low-producing muck field in New York

where onion yields had fallen to less than a thirdof the local average, a single year of a dense plant-ing of sorghum-sudangrass hybrid restored thesoil to a condition close to that of newly clearedland (217).

Widely adapted. Sorghum-sudangrass hybridscan be grown throughout the U.S.wherever rain-fall is adequate and soil temperature reaches65° F to 70° F at least two months before frost.Once established, they can withstand drought bygoing nearly dormant. Sorghum-sudangrasshybrids tolerate pH as high as 9.0, and are oftenused in rotation with barley to reclaim alkalinesoil (421).They tolerate pH as low as 5.0.

Quick forage. Sorghum-sudangrass is prized assummer forage. It can provide quick cover to pre-vent weeds or erosion where legume forages havebeen winterkilled or flooded out. Use carebecause these hybrids and other sorghums canproduce prussic acid poisoning in livestock.Grazing poses the most risk to livestock whenplants are young (up to 24 inches tall), droughtstressed or killed by frost.Toxicity danger variesbetween cultivars.

SORGHUM-SUDANGRASS (Sorghum bicolor X S.bicolor var. sudanese

MarianneSarrantonio


MANAGEMENT

EstablishmentPlant sorghum-sudangrass when soils are warmand moist, usually at least two weeks after theprime corn-planting date for your area. It will tol-erate low-fertility,moderate acidity and high alka-linity, but prefers good fertility and near-neutralpH (361). Standard biomass production usuallyrequires 75 to 100 lb.N/A .With sufficient surface moisture, broadcast 40

to 50 lb./A,or drill 35 to 40 lb./A as deep as 2 inch-es to reach moist soil.These rates provide aquicker canopy tosmother weeds thanlower rates usedfor forage produc-tion, but they requiremowing or grazingto prevent lodging.

Herbicide treatment or a pass with a mechanicalweeder may be necessary if germination is spottyor perennial weeds are a problem. New York on-farm tests show that a stale seedbed method—tilling, then retilling to kill the first flush of weedsjust before planting—provides effective weedcontrol.

Warm season mixtures. Plant sorghum-sudan-grass in cover crop mixtures with buckwheat orwith the legumes sesbania (Sesbania exaltata),sunnhemp (Crotolaria juncea), forage soybeans(Glycine max) or cowpeas (Vigna unguiculata).Broadcast these large-seeded cover crops withthe sorghum-sudangrass, then incorporate about1 inch deep. Fast-germinating buckwheat helpssuppress early weeds. Sorghum-sudangrass sup-ports the sprawling sesbania, forage soybeansand cowpeas. Sunnhemp has an upright habit,but could compete well for light if matchedwith a sorghum-sudangrass cultivar of a similarheight.

Field ManagementPlants grow very tall (up to 12 feet),produce tonsof dry matter and become woody as they mature.

This can result in an unmanageable amount oftough residue that interferes with early plantingthe following spring (277).Mowing or grazing when stalks are 3 to 4 feet

tall encourages tillering and deeper root growth,and keeps regrowth vegetative and less fibrousuntil frost. For mid-summer cuttings, leave at least6 inches of stubble to ensure good regrowth andcontinued weed suppression. Delayed plantingwithin seven weeks of frost makes mowingunnecessary and still allows for good growthbefore winterkilling (277, 361).Disking while plants are still vegetative will

speed decomposition.Make several passes with aheavy disk or combination tillage tool to handlethe dense root masses (277).Sicklebar mowing orflail chopping before tillage will reduce the num-ber of field operations required to incorporate thecrop and speed decomposition.Sicklebar mowerscut more cleanly but leave the stalks whole.Usinga front-mounted flail chopper avoids the problemof skips where tractor tires flatten the plants,putting them out of reach of a rear-mountedchopper.Any operations that decrease the residue size

shortens the period during which the decompos-ing residue will tie up soil nitrogen and hinderearly planted crops in spring. Even when mowed,residue will become tough and slower to breakdown if left on the surface.Flail chopping after frost or killing the cover

crop with herbicide will create a suitable mulchfor no-till planting, preserving soil life and soilstructure in non-compacted fields.

Pest ManagementWeeds. Use sorghum-sudangrass to help controlnutsedge infestations, suggests Cornell ExtensionIPM vegetable specialist John Mishanec. Allowthe nutsedge to grow until it’s about 4 to 5 inch-es tall but before nutlets form, about mid-June inNewYork. Kill the nutsedge with herbicide, thenplant the weed-smothering hybrid.To extend weed suppressive effects into the

second season, select a cultivar known for weedsuppression and leave roots undisturbed whenthe stalks are mowed or grazed (440).

These heat-loving

plants are unrivaled

for adding organic

matter to soils.

SORGHUM-SUDANGRASS HYBRIDS 109

Beneficial habitat. Some related sorghum culti-vars harbor beneficial insects such as seven-spot-ted lady beetles (Coccinella septempunctata) andlacewings (Chrysopa carnea) (421).

Nematodes. Sorghum-sudangrass hybrids andother sorghum-related crops and cultivars sup-press some species of nematodes. Specific culti-vars vary in their effectiveness on different racesof nematodes. These high-biomass-producingcrops have a general suppressive effect due totheir organic matter contributions. But they alsoproduce natural nematicidal compounds thatchemically suppress some nematodes,many stud-ies show.Timing of cutting and tillage is very important

to the effectiveness of nematode suppression.Thecover crop needs to be tilled before frost while itis still green. Otherwise, the nematicidal effect islost. For maximum suppression of soilborne dis-eases, cut or chopped sudangrass must be wellincorporated immediately (308).For suppressing root-knot nematodes in Idaho

potato fields, rapeseed has proven slightly moreeffective and more dependable than sorghum-sudangrass hybrids (394).In an Oregon potato trial, TRUDAN 8 sudangrass

controlled Columbia root-knot nematodes(Meloidogoyne Chitwoodi), a serious pest ofmany vegetable crops.Control extended through-out the zone of residue incorporation.The covercrop’s effect prevented upward migration of thenematodes into the zone for six weeks, workingas well as the nematicide ethoprop. Both treat-ments allowed infection later in the season (285).In the study, TRUDAN 8 sudangrass and the

sorghum-sudangrass hybrid cultivars SORDAN 79and SS-222 all reduced populations of root-knotnematodes. These cultivars are poor nematodehosts and their leaves—not roots—have a nemati-cidal effect. TRUDAN 8 should be used if the cropwill be grazed due to its lower potential for prus-sic acid poisoning.The sorghum-sudangrass culti-vars are useful if the cover crop is intended foranti-nematicidal effects only (285). In otherOregon andWashington trials, the cover crop sup-pression required supplemental chemical nemati-cide to produce profitable levels of U.S. No. 1potatoes (285). These same sudangrass and

sorghum-sudangrass hybrid cultivars failed toshow any significant nematicidal effects in a laterexperiment inWisconsin potato fields (249).When faced with infestations of the nematodes

Meloidogoyne incognita and M. arenaria,Oswego, N.Y., onion growerDan Dunsmoor found that awell-incorporated sorghum-sudangrass cover crop wasmore effective than fumiga-tion. Further, the nematicidaleffect continued into the nextseason,while the conditions ayear after fumigation seemedworse than before the applica-tion. He reports that thesorghum-sudangrass covercrop also controls onion mag-got, thrips and Botrytis leafblight (217).

Insect pests. Chinch bug (Blissus leucopterus),sorghum midge (Contarinia sorghicola), cornleaf aphid (Rhopalosiphum maidis), corn ear-worm (Heliothis zea), greenbugs (Schizaphisgraminum) and sorghum webworm (Celamasorghiella) sometimes attack sorghum-sudangrasshybrids. Early planting helps control the first twopests, and may reduce damage from webworms.Some cultivars and hybrids are resistant to chinchbugs and some biotypes of greenbugs (361). InGeorgia, some hybrids hosted corn leaf aphid,greenbug, southern green stinkbugs (Nezaraviridula) and leaffooted bug (Leptoglossus phyl-lopus).

Crop SystemsThere are several strategies for reducing nitrogentie-up from residue:• Interplant a legume with the sorghum-sudan-grass hybrid.

• Plant a legume cover crop after the sorghum-sudangrass hybrid, in either late summer orthe following spring.

• Apply nitrogen fertilizer or some other Nsource at incorporation and leave the land fal-low for a few months when soil is not frozento allow decomposition of the residue.

These plants

produce

chemicals

that inhibit

certain

weeds and

nematodes.


If you kill the cover crop early enough in fall,the residue will partially break down before coldtemperatures slow biological action (361).Wherepossible, use sorghum-sudangrass ahead of later-planted crops to allow more time in spring forresidue to decompose.Planting sorghum-sudangrass every third year

on NewYork potato and onion farms will rejuve-nate soil, suppress weeds and may suppress soilpathogens and nematodes.Working a legume intothe rotation will further build soil health and addnitrogen. Sorghum-sudangrass hybrids can pro-

vide needed soil structure benefits whereverintensive systems cause compaction and loss ofsoil organic matter reserves. See Summer CoversRelieve Compaction, above.Grown as a summer cover crop that is cut once

and then suppressed or killed, sorghum-sudan-grass can reduce weeds in fall-planted alfalfa.Sorghum-sudangrass suppressed alfalfa rootgrowth significantly in a Virginia greenhousestudy (144), but no effect was observed on alfalfagermination when alfalfa was no-till planted intokilled or living sorghum-sudangrass (145).

Summer Covers Relieve Compaction

A summer planting of sudangrass was the bestsingle-season cover crop for relieving soilcompaction in vegetable fields, a team ofCornell researchers found.Yellow mustard,HUBAM annual white sweetclover andperennial ryegrass also were effectiveto some extent in the multi-year study.“Butsudangrass has proven the most promising sofar,” says project coordinator DavidWolfe.“Ithas shown the fastest root growth.”“Sudangrass is best managed with one

mowing during the season,” Wolfe adds.Mowingpromotes tillering and a deep,penetrating rootsystem. Mowing also makes it easier toincorporate the large amount of biomassproduced by this crop.With its high C:N ratio,it adds to soil organic matter.Farmers and researchers have long known

that alfalfa’s deep root system is a greatcompaction-buster. But alfalfa does notestablish easily on wet compacted fields, andmost vegetable growers can’t afford to removeland from production for two to three years togrow it, notesWolfe.Many also lack theequipment to subsoil their fields,which isoften only a temporary solution, at best.That’swhyWolfe geared his study to identify covercrops that can produce results in a singleseason. In the case of heat-loving sudangrass,it also may be possible to squeeze a spring or

fall cash crop into the rotation while stillgrowing the cover during summer.Heavy equipment, frequent tillage and lack

of organic matter contribute to compactionproblems for vegetable growers in theNortheast,where frequent rains often forcegrowers into the fields when soils are wet.Compacted soils slow root development,hinder nutrient uptake, stunt plants, delaymaturity and can worsen pest and diseaseproblems (451). For example, the Cornellresearchers found that slow-growing cabbagesdirect-seeded into compacted soils werevulnerable to flea beetle infestations (450).Brassica cover crops such as yellow mustard

were solid challengers to sudangrass as acompaction reliever, but it was sometimesdifficult to establish these crops in the test.“We still have a lot to learn about how bestto grow brassicas and fit them into rotationswith vegetables,”Wolfe says.Wolfe and his team assessed the cover

crops’ effectiveness by measuring yields ofsubsequent crops and conducting a host ofsoil quality measurements, includinginfiltration rates,water-holding capacity,aggregate stability and organic matter levels.For more information, contact DavidWolfe,

607-255-7888; [email protected] in 2007 by Andy Clark

WINTER WHEAT 111

Although typically grown as a cash grain,winter wheat can provide most of thecover crop benefits of other cereal crops,

as well as a grazing option prior to spring tillerelongation. It’s less likely than barley or rye tobecome a weed and is easier to kill.Wheat also isslower to mature than some cereals,so there is no

rush to kill it early in spring and risk compactingsoil in wet conditions. It is increasingly growninstead of rye because it is cheaper and easier tomanage in spring.Whether grown as a cover crop or for grain,

winter wheat adds rotation options forunderseeding a legume (such as red clover or

WINTER WHEATTriticum aestivum

Type: winter annual cereal grain;can be spring-planted

Roles: prevent erosion, suppressweeds, scavenge excess nutrients,add organic matter

Mix with: annual legumes, ryegrassor other small grains


In Colorado,sorghum-sudangrass increased irri-gated potato tuber quality and total marketableyield compared. It also increased nutrient uptakeefficiency on the sandy, high pH soils. In this sys-tem, the sorghum-sudangrass is grown with limit-ed irrigation, but with enough water so that thebiomass could be harvested for hay or incorpo-rated as green manure (112, 113).In California, some table grape growers use

sorghum-sudangrass to add organic matter and toreduce the reflection of light and heat from thesoil, reducing sunburn to the grapes.

COMPARATIVE NOTES

Sorghum-sudangrass hybrids can produce moreorganic matter per acre, and at a lower seed cost,than any major cover crop grown in the U.S.Incorporated sorghum-sudangrass residue

reduces N availability to young crops more thanoat residue but less than wheat residue (389).

Cultivars.When comparing sorghum-sudangrasscultivars, consider traits such as biomass yieldpotential, tillering and regrowth ability, diseaseresistance, insect resistance (especially if green-bugs are a problem) and tolerance to iron defi-ciency chlorosis.If you plan to graze the cover crop, select

sorghum-sudangrass hybrids and related cropswith lower levels of dhurrin, the compoundresponsible for prussic acid poisoning. For maxi-mum weed control, choose types high in sor-goleone, the root exudate that suppresses weeds.Sterile cultivars are best where escapes could bea problem, especially where crossing with john-songrass (Sorghum halpense) is possible.


without underseed-ing a legume orlegume-grass mix,winter wheatprovides greatgrazing andnutritional valueand can extend thegrazing season.

• In Colorado vegetablesystems,wheatreduced wind erosionand scavenged Nfrom 5 feet deep inthe profile (111,114).

• In parts of Zone 6and warmer, youalso have a depend-able double-cropoption. See WheatBoosts Incomeand Soil Protection(p. 113).

Weed suppressor. As a fall-sown cereal, wheatcompetes well with most weeds once it is estab-lished (71). Its rapid spring growth also helpschoke weeds, especially with an underseededlegume competing for light and surface nutrients.

Soil builder and organic matter source.Wheat is a plentiful source of straw and stubble.Wheat’s fine root system also improves topsoiltilth.Although it generally produces less than ryeor barley, the residue can be easier to manage andincorporate.When selecting a locally adapted variety for use

as a cover crop, you might not need premiumseed. A Maryland study of 25 wheat cultivarsshowed no major differences in overall biomassproduction at maturity (92). Also in Maryland,wheat produced up to 12,500 lb. biomass/Afollowing high rates of broiler litter (87).In Colorado,wheat planted inAugust after early

vegetables produced more than 4,000 lb. bio-mass/A, but if planted in October, yielded onlyone-tenth as much biomass and consequentlyscavenged less N (114).


sweet-clover) for forage or nitrogen. It works wellin no-till or reduced-tillage systems, and for weedcontrol in potatoes grown with irrigation in semi-arid regions.

BENEFITS

Erosion control. Winter wheat can serve as anoverwintering cover crop for erosion control inmost of the continental U.S.

Nutrient catch crop.Wheat enhances cycling ofN, P and K. A heavy N feeder in spring, wheattakes up N relatively slowly in autumn. It adds up,however.A September-seeded stand absorbed 40lb. N/A by December, a Maryland study showed(46).As an overwintering cover rather than a graincrop,wheat wouldn’t need fall or spring fertilizer.A 50 bushel wheat crop can take up 20 to 25

lb. P2O5 and 60 lb. K2O per acre by boot stage.About 80 percent of the K is recycled if the stemsand leaves aren’t removed from the field at har-vest. All the nutrients are recycled when wheat ismanaged as a cover crop, giving it a role in scav-enging excess nitrogen.“Cash and Cover” crop.Winter wheat can begrown as a cash crop or a cover crop, althoughyou should manage each differently. It provides acash-grain option while also opening a spot for awinter annual legume in a corn>soybean or simi-lar rotation. For example:• In the Cotton Belt,wheat and crimson cloverwould be a good mix.

• In Hardiness Zone 6 and parts of Zone 7, planthairy vetch after wheat harvest, giving thelegume plenty of time to establish in fall.Vetchgrowth in spring may provide most of the Nnecessary for heavy feeders such as corn, orall of the N for sorghum, in areas northward tosouthern Illinois,where early spring warm-upallows time for development.

• In much of Zone 7, cowpeas would be a goodchoice after wheat harvest in early July orbefore planting winter wheat in fall.

• In the Corn Belt and northern U.S., undersowred clover or frostseed sweetclover into awheat nurse crop if you want the option of ayear of hay before going back to corn.With or

WINTER WHEAT(Triticum aestivum)

ElayneSears

WINTER WHEAT 113

If weed control is important in your system,look for a regional cultivar that can produce earlyspring growth.To scavenge N,select a variety withgood fall growth before winter dormancy.

MANAGEMENT

Establishment & FieldworkWheat prefers well-drained soils of medium tex-ture and moderate fertility. It tolerates poorlydrained, heavier soils better than barley or oats,but flooding can easily drown a wheat stand. Ryemay be a better choice for some poor soils.Biomass production and N uptake are fairly

slow in autumn. Tillering resumes in late win-ter/early spring and N uptake increases quicklyduring stem extension.Adequate but not excessive N is important dur-

ing wheat’s early growth stages (prior to stemgrowth) to ensure adequate tillering and rootgrowth prior to winter dormancy. In low-fertilityor light-textured soils, consider a mixed seedingwith a legume (80). SeeWheat Offers HighValueWeed Control, Too (p. 114).A firm seedbed helps reduce winterkill of

wheat. Minimize tillage in semiarid regions to

avoid pulverizing topsoil (358) and depleting soilmoisture.

Winter annual use. Seed from late summer toearly fall in Zone 3 to 7—a few weeks earlier thana rye or wheat grain crop—and from fall to earlywinter in Zone 8 and warmer. If you are consider-ing harvesting as a grain crop, you should waituntil the Hessian fly-free date, however. If covercrop planting is delayed, consider sowing ryeinstead.Drill 60 to 120 lb./A (1 to 2 bushels) into a firm

seedbed at a 1/2- to 11/2-inch depth or broadcast 60to 160 lb./A (1 to 2.5 bushels) and disk lightly orcultipack to cover. Plant at a high rate if seedinglate, when overseeding into soybeans at the leaf-yellowing stage,when planting into a dry seedbedor when you require a thick, weed-suppressingstand. Seed at a low to medium rate when soilmoisture is plentiful (71).After cotton harvest in Zone 8 and warmer,

no-till drill 2 bushels of wheat per acre without anyseedbed preparation.In the Southern Plains,1 bushelis sufficient if drilling in a timely fashion (302).With irrigation or in humid regions, you could

harvest 45- to 60-bushel wheat, then double crop

Wheat Boosts Income and Soil Protection

Wheat is an ideal fall cover crop that you canlater decide to harvest as a cash crop, cottonfarmer Max Carter has found.“It’s easier tomanage than rye, still leaves plenty of residueto keep topsoil from washing away—and isan excellent double crop,” says Carter.The southeastern Georgia farmer no-till

drills winter wheat at 2 bushels per acre rightafter cotton harvest,without any seedbedpreparation.“It gives a good, thick stand,”hesays.“We usually get wheat in byThanksgiving,

but as long as it’s planted by Christmas, Iknow it’ll do fine,”he adds. After drillingwheat, Carter goes back and mows the cottonstalks to leave some field residue until thewheat establishes.

Disease or pests rarely have been a problem,he notes.“It’s a very easy system,with wheat always

serving as a fall cover crop for us. It builds soiland encourages helpful soil microorganisms.It can be grazed, or we can burn some downin March for planting early corn or peanutsanytime from March to June,”he says.For a double crop before 2-bale-an-acre

cotton,Carter irrigates the stand once inspring with a center pivot and harvests 45-to 60-bushel wheat by the end of May.“Thechopper on the rear of the combine puts thestraw right back on the soil as an even blanketand we’re back planting cotton on June 1.”“It sure beats idling land and losing topsoil.”


with soybeans, cotton or another summer crop.See Wheat Boosts Income and Soil Protection(p. 113). You also could overseed winter wheatprior to cotton defoliation and harvesting.Another possibility for Zone 7 and cooler:Plant

full-season soybeans into wheat cover cropresidue, and plant a wheat cover crop after beanharvest.

Mixed seeding or nurse crop. Winter wheatworks well in mixtures with other small grains orwith legumes such as hairy vetch. It is an excel-lent nurse crop for frostseeding red clover orsweetclover, if rainfall is sufficient. In the CornBelt, the legume is usually sown in winter, beforewheat’s vegetative growth resumes. If frostseed-ing, use the full seeding rates for both species,

Wheat Offers High-Value Weed Control

Pairing a winter wheat cover crop with areduced herbicide program in the inlandPacific Northwest could provide excellentweed control in potatoes grown on light soilsin irrigated, semiarid regions. A SARE-fundedstudy showed that winter wheat providedeffective competition against annual weedsthat infest irrigated potato fields inWashington,Oregon and Idaho.Banding herbicide over the row when

planting potatoes improved the system’seffectiveness, subsequent research shows, saysproject coordinator Dr.Charlotte Eberlein atthe University of Idaho’s Aberdeen Researchand Extension Center.“In our initial study,wewere effectively no-tilling potatoes into theRoundup-killed wheat,” says Eberlein.“In thisstudy we killed the cover crop and plantedpotatoes with a regular potato planter,whichrips the wheat out of the potato row.”Agrower then can band a herbicide mixtureover the row and depend on the wheat mulchto control between-row weeds.“If you have sandy soil to start with and can

kill winter wheat early enough to reducewater-management concerns for the potatoes,the system works well,” says Eberlein.“Winter rye would be a slightly better cover

crop for suppressing weeds in a system likethis,” she notes.“Volunteer rye, however, is aserious problem in wheat grown in theWest,and wheat is a common rotation crop forpotato growers in the Pacific Northwest.”She recommends drilling winter wheat at

90 lb./A into a good seedbed, generally in mid-September in Idaho.“In our area, growers candeep rip in fall, disk and build the beds (hills),then drill wheat directly into the beds,” shesays. Some starter N (50 to 60 lb./A) can helpthe wheat establish. If indicated by soil testing,P or K also would be fall-applied for thefollowing potato crop.The wheat usually does well and shows

good winter survival.Amount of spring rainfalland soil moisture and the wheat growth ratedetermine the optimal dates for killing wheatand planting potatoes.Some years, you might plant into the wheat

and broadcast Roundup about a week later.Other years, if a wet spring delays potatoplanting, you could kill wheat before it getsout of hand (before the boot stage), then waitfor better potato-planting conditions.Moisture management is important,

especially during dry springs, she says.“Weusually kill the wheat from early to mid May—a week or two after planting potatoes.That’ssoon enough to maintain adequate moisture inthe hills for potatoes to sprout.”An irrigation option ensures adequate soil

moisture—for the wheat stand in fall or thepotato crop in spring, she adds.“You want agood, competitive wheat stand and a vigorouspotato crop if you’re depending on a bandedherbicide mix and wheat mulch for weedcontrol,” says Eberlein.That combination givescompetitive yields, she observes, based onresearch station trials.

WINTER WHEAT 115

according to recent work in Iowa (34). If you sowsweetclover in fall with winter wheat, it couldoutgrow the wheat. If you want a grain option,that could make harvest difficult.

Spring annual use. Although it’s not a commonpractice, winter wheat can be planted in thespring as a weed-suppressing companion crop orearly forage.You sacrifice fall nutrient scavenging,however.Reasons for spring planting include win-ter kill or spotty overwintering, or when you justdidn’t have time to fall-seed it. It won’t have achance to vernalize (be exposed to extended coldafter germination),so it will not head out and usu-ally dies on its own within a few months,withoutsetting seed. This eliminates the possibility of itbecoming a weed problem in subsequent crops.By sowing when field conditions permit in earlyspring,within a couple months you could have a6- to 10-inch tall cover crop into which you canno-till your cash crop.You might not need a burn-down herbicide, either.Early spring planting of spring wheat, with or

without a legume companion, is an option, espe-cially if you have a longer rotation niche available.

Field ManagementYou needn’t spring fertilize a winter wheat standbeing grown as a cover crop rather than a graincrop.That would defeat the primary purpose (N-scavenging) of growing a small grain cover crop.As with any overwintering small grain crop, how-ever, you will want to ensure the wheat standdoesn’t adversely affect soil moisture or nutrientavailability for the following crop.

KillingKill wheat with a roller crimper at soft-doughstage or later, with a grass herbicide, or by plow-ing, disking or mowing before seed matures. Aswith other small grain cover crops, it is safest tokill about 2-3 weeks before planting your cashcrop, although this will depend on local condi-tions and your killing and tillage system.

Because of its slower springgrowth, there is less need torush to kill wheat in spring asis sometimes required forrye. That’s one reason veg-etable grower Will Stevens ofShoreham, Vt., prefers wheatto rye as a winter cover on hisheavy, clay-loam soils. Thewheat goes to seed slower andcan provide more biomassthan an earlier killing of rye would,he’s found.Withrye, he has to disk two to three weeks earlier inspring to incorporate the biomass,which can be aproblem in wet conditions. “I only chisel plowwheat if it’s really rank,”he notes.

Pest ManagementWheat is less likely than rye or barley to becomea weed problem in a rotation, but is a little moresusceptible than rye or oats to insects and disease.Managed as a cover crop, wheat rarely poses aninsect or disease risk. Diseases can be more of aproblem the earlier wheat is planted in fall, espe-cially if you farm in a humid area.Growing winter wheat could influence the

buildup of pathogens and affect future small-graincash crops,however.Use of resistant varieties andother IPM practices can avoid many pest prob-lems in wheat grown for grain. If wheat diseasesor pests are a major concern in your area, rye orbarley might be a better choice as an overwinter-ing cover crop that provides a grain option,despite their lower grain yield.

Other OptionsChoosing wheat as a small-grain cover crop offersthe flexibility in late spring or early summer toharvest a grain crop. Spring management such asremoving grazing livestock prior to heading andtopdressing with N is essential for the grain cropoption.


Wheat is less

likely than

barley or rye

to become a

weed, and is

easier to kill.


OVERVIEW OF LEGUME COVER CROPS

Commonly used legume cover crops include:• Winter annuals, such as crimson clover, hairyvetch, field peas, subterranean clover andmany others

• Perennials like red clover,white clover andsome medics

• Biennials such as sweetclover• Summer annuals (in colder climates, the win-ter annuals are often grown in the summer)

Legume cover crops are used to:• Fix atmospheric nitrogen (N) for use bysubsequent crops

• Reduce or prevent erosion• Produce biomass and add organic matter tothe soil

• Attract beneficial insects

Legumes vary widely in their ability to preventerosion, suppress weeds and add organic matterto the soil. In general, legume cover crops do notscavenge N as well as grasses. If you need a covercrop to take up excess nutrients after manure orfertilizer applications, a grass, a brassica or a mix-ture is usually a better choice.Winter-annual legumes, while established in

the fall,usually produce most of their biomass andN in spring.Winter-annual legumes must be plant-ed earlier than cereal crops in order to survive thewinter in many regions. Depending on your cli-mate, spring management of legumes will ofteninvolve balancing early planting of the cash cropwith waiting to allow more biomass and N pro-duction by the legume.Perennial or biennial legumes can fit many dif-

ferent niches, as described in greater detail in theindividual sections for those cover crops.Sometimes grown for a short period between

cash crops,these forage crops also can be used formore than one year and often are harvested forfeed during this time. They can be establishedalong with—or overseeded into—other cropssuch as wheat or oats, then be left to grow aftercash crop harvest and used as a forage.Here theyare functioning more as a rotation crop than acover crop, but as such provide many benefitsincluding erosion and weed control, organic mat-ter and N production.They also can break weed,disease and insect cycles.Summer-annual use of legume crops includes,

in colder climates, the use of the winter-annualcrops listed above, as well as warm-seasonlegumes such as cowpeas. Grown as summerannuals, these crops produce N and provideground cover for weed and erosion control, aswell as other benefits of growing cover crops.Establishment and management varies widelydepending on climate, cropping system and thelegume itself.These topics will be covered in theindividual sections for each legume.Legumes are generally lower in carbon and

higher in nitrogen than grasses. This lower C:Nratio results in faster breakdown of legumeresidues.Therefore,the N and other nutrients con-tained in legume residues are usually releasedfaster than from grasses.Weed control by legumeresidues may not last as long as for an equivalentamount of grass residue.Legumes do not increasesoil organic matter as much as grasses.Mixtures of legume and grass cover crops com-

bine the benefits of both, including biomass pro-duction, N scavenging and additions to thesystem,as well as weed and erosion control.Somecover crop mixtures are described in the individ-ual cover crop sections.

COVER CROP MIXTURES 117

Mixtures of two or more cover crops areoften more effective than planting a sin-gle species. Cover crop mixtures offer

the best of both worlds,combining the benefits ofgrasses and legumes,or using the different growthcharacteristics of several species to fit your needs.You can use cover crop mixtures to improve:

•Winter survival• Ground cover• Use of solar energy• Biomass and N production•Weed control• Duration of active growing period• Range of beneficial insects attracted•Tolerance of adverse conditions• Forage options• Response to variable soil traits

Disadvantages of cover crop mixtures mayinclude:• Higher seed cost•Too much residue• More complicated management• Difficult to seed

Crop mixtures can reduce risk in cropping sys-tems because each crop in the mix may responddifferently to soil, pest and weather conditions. Inforage or grazing systems, for example, a mix ofrye, wheat and barley is more nutritious, can begrazed over a longer period of time and is lesslikely to be devastated by a single disease.Using drought-tolerant plants in a perennial

mix builds in persistence for dry years. Using anumber of cover crops with“hard seed”that takesmany months to germinate also improves cover-age over a broader range of conditions.Mixing cultivars of a single species with varied

maturity dates and growth habits maintains opti-mum benefits for a longer time. Orchardists inCalifornia mix subclovers to keep weeds at bay allseason.One cultivar comes on early, then dies backas two later cultivars—one tall and one short—

COVER CROP MIXTURES EXPAND POSSIBILITIES

come on strong. Because they reseed themselves,the cooperative trio persists year after year.Sometimes you don’t know how much N may

be left after cash crop harvest.Do you need a grassto scavenge leftover N,or a legume to provide fixedN? A grass/legume cover crop mixture adjusts tothe amount of available soil N: If there is a lot of N,the grass dominates; if there is not much availablesoil N, the legume will tend to dominate a mixture.In either case, you get the combined benefit of Nscavenging by the grass cover crop and N additionsfrom the legume cover crop.Mixing low-growing and taller crops, or fast-

starting grasses and slow-developing legumes,usually provides better erosion control becausemore of the ground is covered. The vegetationintercepts more raindrops before they can dis-lodge soil particles. Sunlight is used more effi-ciently because light that passes through the tallcrop is captured by the low-growing crop.Adding grasses to a fall-seeded legume

improves soil coverage over winter and increasesthe root mass to stabilize topsoil. A viny crop likevetch will climb a grass, so it can get more lightand fix more N, or so it can be harvested moreeasily for seed.A faster-growing crop serves as anurse crop for a slow-growing crop,while cover-ing the ground quickly for erosion control. Thepossibilities are endless!Mixtures can complicate management, how-

ever. For example:• They may cost more to seed. Seeding rates foreach component of the mix are usually lowerthan for sole-crop plantings, but the total seedcost may still be more.

• The best time to kill one crop may not be thebest for another crop, so a compromise datemay be used.

• If you use herbicides, your choices may belimited when you plant a mixture of legumesand nonlegumes.

• Sometimes you can end up with more residuethan your equipment can handle.


The benefits of a mixture will usually outweighthese disadvantages,but you need to be prepared tomanage the mixture carefully to prevent problems.Each cover crop chapter gives examples of spe-

cific mixtures that have been tested and workwell. Try some of the proven cover crop mix-

BERSEEM CLOVERTrifolium alexandrinum

Also called: Egyptian clover

Type: summer annual or winterannual legume

Roles: suppress weeds, preventerosion, green manure, choppedforage, grazing

Mix with: oats, ryegrass, smallgrains as nurse crops; as nurse cropfor alfalfa

See charts, p. 66 to 72, for rankingand management summary.

summer annualwinter annual

Afast-growing summer annual, berseemclover can produce up to 8 tons of forageunder irrigation. It’s a heavy N producer

and the least winter hardy of all true annualclovers.This makes it an ideal winterkilled coverbefore corn or other nitrogen-demanding crops inCorn Belt rotations. Berseem clover draws downsoil N early in its cycle. Once soil reserves areused up, it can fix 100 to 200 lb. N/A or more. Itestablishes well with an oat nurse crop,making itan excellent cover for small grain>corn>soybeanrotations in the Midwest.In Iowa, the cultivar BIGBEE compares favorably

with alfalfa in its regrowth following small grainharvest, its feed value and its tolerance to droughtand excess moisture (156). As a winter annual inCalifornia, irrigation usually is needed to allowberseem to achieve its full potential. Its peak

growth period during the West Coast’s rainy sea-son and its highly efficient water use comparefavorably to alfalfa as a high-producing forage andgreen manure.

BENEFITS

Green manure. Berseem clover is the fertilityfoundation of agriculture in the Nile Delta, andhas nourished soils in the Mediterranean regionfor millennia. MULTICUT berseem clover averaged280 lb.N/A in a six-year trial in California with sixcuttings per year (162), and grew faster thanBIGBEE in one Iowa report (155). Berseem is lessprone to possible N leaching if grown to maturitywithout cutting, when it produces 100 to 125 lb.N/A.Top N fixation occurs when soils have lessthan 150 lb. N/A (162).A single cutting can yield

tures, and create your own tailor-made mixtures.Remember that adding another crop increasesthe diversity on your farm,and is likely to increasethe many proven benefits of rotations overmonocropping.

BERSEEM CLOVER 119

50 to 100 lb. topgrowth N/A. Berseem’s dry mat-ter N concentration is about 2.5 percent (162).

Biomass. Berseem clover produced the mostbiomass (6,550 lb./A) of five winter annuallegumes in a two-year Louisiana test, and came insecond to arrowleaf clover (Trifolium vesiculo-sum) in N, accumulating 190 lb. N/A toarrowleaf’s 203 lb. N/A. Also tested were TIBBEEcrimson clover, WOOGENELUP subterraneumclover and WOODFORD bigflower vetch. All butarrowleaf clover were able to set seed by May 13and regrow in the fall,despite the herbicides usedto suppress them in spring and to control weedsduring summer (36).In Alberta legume trials, berseem clover aver-

aged 3,750 lb. dry matter/A over three years at asite where hairy vetch and field peas produced5,300 and 4,160 lb./A, respectively. With irriga-tion, berseem clover topped 19 other legumes atthe same site with a mean yield of 5,500 lb.DM/A.

Smother crop. Planted with oats or annual rye-grass, berseem clover suppresses weeds well dur-ing establishment and regrowth after oat harvest.

Companion crop. Planted with oat, the twocrops can be harvested together as silage,haylageor hay, depending on the crop’s developmentstage. Berseem/oat haylage has very high feedquality if cut at oats’boot stage (157).Dry seasonsfavor development of an oat grain crop, afterwhich berseem clover can be cut one, two orthree times in the Midwest.

Quick growing.At 60° F, berseem clover will beready to cut about 60 days after planting.

Legume nurse crop. Because of its quick germi-nation (seven days), quick growth and win-terkilling tendency,berseem clover can be used asa nurse crop for alfalfa.

Seed crop. Berseem produces up to 1,000 lb.seed/A if it is left to mature.Only BIGBEE berseemclover has hard seed that allows natural self-reseeding, and it reseeds too late for timely plant-ing of most summer crops (103).

Grazing and forage crop. At 18 to 28 percentprotein, young berseem clover is comparable toor better than crimson clover or alfalfa as feed.No cases of bloat from grazing berseem cloverhave been reported (158, 278). Forage qualityremains acceptable until the onset of seedproduction. BIGBEE berseem clover and TIBBEEcrimson produce more fall and winter growththan do other winter annual clovers in theSouth. BIGBEE con-tinues producinglonger into thespring than otherlegumes, extendingcuttings into lateMay or early June inMississippi (225).

MANAGEMENT

EstablishmentBerseem prefers slightly alkaline loam and siltysoils but grows in all soil types except sands.Soil phosphorus can limit berseem clovergrowth. Fertilize with 60 to 100 lb. P2O5/A ifsoil tests below 20 ppm (162). Boron alsomay limit growth, so test soil to maintain levels(278). Berseem tolerates saline conditions betterthan alfalfa and red clover (120). Use R-typeinoculant suitable for berseem clover and crim-son clovers.Broadcast or drill berseem seed alone or with

spring grains onto a firm, well-prepared seedbedor closely cropped sod so that it is 1/4-inch deepwith a light soil covering. To improve seed-soilcontact and to maintain seed-zone moisture, culti-pack or roll soil before and after broadcastseeding (162).Dry, loose soil will suppress germi-nation.Recommended seeding rates are 8 to 12 lb./A

drilled or 15 to 20 lb./A broadcast.Excessive rateswill create an overly thick stand that preventstillering and spreading of the root crowns.Montana trials set the optimum seeding rate atabout 8 lb./A drilled in 12-inch rows,with a high-er rate in narrower rows where herbicides are notused to control weeds (442).

MULTICUT berseem

clover averaged 280

lb. N/A in a six-year

California trial.


BERSEEM CLOVER (Trifolium alexandrinum)

MarianneSarrantonio

Midwest. Seed after April 15 to avoid crop lossdue to a late frost.Berseem frostseeded at 15 lb./Ayields well in the upper Midwest. In southernMichigan, frostseeded berseem clover produced1.5 T dry matter/A and 85 lb. N/A (373, 376), butfrost risk is significant.Iowa tests over four years showed that inter-

seeded berseem and oats averaged 76 percentmore dry matter (ranging from 19 to 150 percent)than oats alone.Underseeding berseem clover didnot significantly reduce oat yields in another Iowastudy. Seed early- to mid-April in Iowa (159).When seeding a mixture, harvest goals affect

variety selection and seeding rates, Iowa research-ers have found. If establishment of an optimumberseem clover stand for green manure is mostimportant,oat or other small grain crop seeded atabout 1 bushel per acre will protect the youngclover and help to break the soil crust. If earlyforage before green manuring is the goal, seed amixture of 4 bu. oats and 15 lb.berseem/A. Ifbiomass quantity is foremost, use a short-stalked,long-season oat.If oat grain production isprimary, keep oat seeding rate the same, butselect a short-season, tall variety to reduce thelikelihood of berseem clover interfering withgrain harvest (156).Berseem clover also can be a late-summer crop.

Planted in mid-August in the Corn Belt, it should

grow about 15 inches before frost,provide wintererosion protection and break down quickly inspring to deliver N from its topgrowth and roots.You can overseed berseem clover into standing

small-grain crops, a method that has worked wellin a series of on-farm tests in Iowa (155).Plant theberseem as late as three weeks after the graincrop germinates or after the tillering stage of win-ter-seeded small grains. Use a heavy seeding rateto compensate for reduced seed-soil contact.Frostseeding in late winter into winter wheat hasnot worked in several attempts in Pennsylvania(361) and Iowa.

Southeast. Fall planting in mild regions provideseffective weed control as well as N and organicmatter for a spring crop.SeedAug.25 to Oct.15 inMississippi or up to Dec.1 in Florida. For a cool-season grass mixture, plant 12 lb. berseem cloverseed with 10 lb. orchardgrass or 20 lb. annual orperennial ryegrass/A (225).

West. Berseem does best in California’s CentralValley when planted by the first or second weekof October. If planting is delayed until November,seedlings will start more slowly in the cool ofwinter (162).

Field ManagementMowing for green manure. Clip wheneverplants are 12 to 15 inches tall and basal shootsbegin to grow. This will be 30 to 60 days afterplanting, depending on weather, field and mois-ture conditions.Mow again every 25 to 30 days toencourage growth of up to 4 T/A. Keep stubbleheight at least 3 to 4 inches tall, because plantsregrow from lower stem branches.To maximize dry matter production,cut as soon

as basal bud regrowth reaches 2 inches (162).Atthe latest,clip before early flowering stage or plantswill not regrow. Berseem clover responds bestwhen field traffic is minimized (156).Mowed berseem clover left in the field as green

manure can hinder regrowth of the legume fromits lower stems. To lessen this problem, flail orsickle-bar mow then rake or fluff with a tedder atintervals until regrowth commences.

BERSEEM CLOVER 121

Remember that berseem clover has a tap rootand shallow 6- to 8-inch feeder root system (156).In thin plantings or well-drained soils, it can besusceptible to drought, a trait that could triggermowing, grazing or killing earlier than originallyplanned (186).Abundant soil N will restrict N fixation by

berseem clover, but moderate amounts up to 150lb.N/A did not limit annual fixation in north cen-tral California. Researchers explain that berseemclover draws heavily on soil N during earlygrowth. When soil N was depleted in this test,berseem began fixing N rapidly until it producedseed and died (447).Berseem made its N contribution to soil in the

final third of its cutting cycle—regardless of initialsoil N availability—in all six years of the study.Nitrogen fixation was closely correlated to a dropin water-use efficiency in the trial. After produc-ing from 400 to 640 lb.of dry matter per acre-inchof water in the first four cuttings, productiondropped to 300 lb.DM/A-in. for the final two cut-tings (447).

Small grain companion. Underseededberseem clover provided about 1.2 T forage drymatter/A after oat harvest in Iowa. Removing theforage decreases the soil-saving ground cover andN contribution (159), trading soil and N benefitsfor attractive near-term income.In the Midwest, greenchop an oat/berseem

clover mixture when oat is at the pre-boot stageto avoid berseem clover going to seed early and,therefore,not producing maximum nitrogen.Oatshave high crude protein at this stage. Monitorcarefully during warm periods to avoid nitrogentoxicity.A Montana study found that spring plantings of

berseem clover will produce the most legume drymatter and N if clear seeded.If,however,you wishto maximize total dry matter and protein, seedingwith oats is recommended. The oat nurse cropsuppressed weeds well and increased total drymatter production by 50 to 100 percent regard-less of whether plots were cut two, three or fourtimes (434).

KillingBerseem dies when exposed to temperatures be-low 20° F for several days, making winterkill avirtual certainty in Zone 7 and colder.This elimi-nates the need for herbicides or mechanicalkilling after a cold winter, and hastens delivery ofnutrients to the soil.To kill berseem

clover ahead of fall-planted crops, waitfor it to die afterblooming, use mul-tiple diskings orapply herbicides.In mild areas, ber-seem clover growsvigorously throughlate spring. BIGBEEberseem clover re-mained vegetativeuntil early May orlater in an experiment at a northern Mississippi(Zone 7) site. Until it reaches full bloom, it willrequire either tillage or a combination of herbicidesand mechanical controls to kill it.In a northern Mississippi mechanical control

study, BIGBEE berseem clover added the most drymatter after mid-April compared to hairy vetch,MT. BARKER subterranean clover and TIBBEE crim-son clover. Berseem and hairy vetch remainedvegetative until mid-May, but by early May, ber-seem clover and crimson had a considerableamount of stems laying down (105).Rolling with 4-inch rollers killed less berseem

clover than hairy vetch or crimson when thelegumes had more than 10 inches of stem layingon the ground. Kill rate was more than 80 per-cent for the latter two crops,but only 53 percentfor berseem clover. Without an application ofatrazine two weeks prior to either flail mowingor rolling with coulters, the mechanical controlsfailed to kill more than 64 percent of theberseem clover until early May, when flailingachieved 93-percent control. Atrazine alonereduced the stand by 68 percent in early April,72 percent in mid-April and 88 percent in earlyMay (105).

The least winter hardy

of the true annual

clovers, berseem can

be planted with oats

in the Corn Belt and

produce abundant N

before winterkilling.


Pest ManagementAvoid direct seeding small-seeded vegetables intofields where you have incorporated berseemclover within the past month, due to allelopathiccompounds in the residue. Berseem clover, crim-son clover and hairy vetch residue incorporateddirectly into the seed zone may suppress germi-

nation and seedling development of onion, carrotand tomato, based on lab tests (40).Lygus bugs have been a serious problem in

California seed production, and virus outbreakscan cause serious damage during wet springswhere berseem grows as a winter annual.Wherevirus is a concern, use JOE BURTON, a resistant cul-

With the help of nitrogen-fixing bacteria,legume cover crops can supply some or allof the N needed by succeeding crops.Thisnitrogen-producing team can’t do the job rightunless you carefully match the correctbacterial inoculant with your legume covercrop species.Like other plants, legumes need nitrogen to

grow.They can take it from the soil if enoughis present in forms they can use. Legume rootsalso seek out specific strains of soil-dwellingbacteria that can“fix”nitrogen gas from theair for use by the plant.While many kinds ofbacteria compete for space on legume roots,the root tissues will only begin this symbioticN-fixing process when they encounter aspecific species of rhizobium bacteria.Onlyparticular strains of rhizobia provide optimumN production for each group of legumes.When the root hairs find an acceptable

bacterial match, they encircle the bacteria tocreate a nodule.These variously shaped lumpson the root surfaces range in size from a BBpellet to a kernel of corn.Their pinkishinteriors are the visible sign that nitrogenfixation is at work.Nitrogen gas (N2) from air in the spaces

between soil particles enters the nodule.Thebacteria contribute an enzyme that helpsconvert the gas to ammonia (NH3).The plantuses this form of N to make amino acids, thebuilding blocks for proteins. In return, the hostlegume supplies the bacteria withcarbohydrates to fuel the N-fixation process.

The rate of N fixation is determined largelyby the genetic potential of the legume speciesand by the amount of plant-available N in thesoil.Other environmental factors such as heatand moisture play a big role, as well. Fueling Nfixation is an expensive proposition for thelegume host,which may contribute up to 20percent of its carbohydrate production to theroot-dwelling bacteria. If the legume can takeup free N from the soil, it won’t put as muchenergy into producing nodules and feedingbacteria to fix nitrogen from the air.Perennial legumes fix N during any time of

active growth. In annual legumes,N fixationpeaks at flowering.With seed formation, itceases and the nodules slough from the roots.Rhizobia return to the soil environment toawait their next encounter with legume roots.These bacteria remain viable in the soil forthree to five years,but often at too low a levelto provide optimum N-fixation when legumesreturn to the field.If legume roots don’t encounter their ideal

bacterial match, they work with the beststrains they can find.They just don’t work asefficiently together and they produce less N.Inoculating seeds with the correct strainbefore planting is inexpensive insuranceto make sure legumes perform up to theirgenetic potential. Clover inoculum, forexample, costs just a few cents per pound ofseed treated, or more for an enhanced stickerthat buffers and feeds the seedling.

Nodulation: Match Inoculant to Maximize N

BERSEEM CLOVER 123

While they are alive, legumes release littleor no nitrogen to the soil.The N in their roots,stalks, leaves and seeds becomes availablewhen the plants die naturally or are killed bytillage,mowing or herbicide. This plantmaterial becomes food for microbes,worms,insects and other decomposers.Microorganisms mineralize, or convert, the

complex“organic” forms of nitrogen in theplant material into inorganic ammonium andnitrate forms, once again making the Navailable to plants.How quickly themineralization of N occurs is determined bya host of environmental and chemical factors.These will affect how much of that legume Nis available to the next crop or has thepotential to leach from the soil.For more information about mineralization

and how much you can reduce your Nfertilizer rate for crops following legumes, seeHow Much N? (p. 22).To get the most from your legume/bacteria

combination:• Choose appropriate legume species foryour climate, soils and cropping system.Also, consider the amount of N it candeliver when you will need it.

• Match inoculant to the species of legumeyou are growing. See Chart 3B,Planting(p.70) to determine the best inoculant to use.

• Coat seedwith the inoculant just beforeplanting.Use milk,weak sugar water or acommercial sticking agent to help the materialstick to the seeds.Use only fresh inoculant(check the package’s expiration date),and do

not expose packages or inoculated seed toexcessive heat or direct sunlight.

Mix the sticker with non-chlorinated waterand add the inoculant to create a slurry, thenthoroughly coat seeds. Seed should be dryenough to plant within half an hour.Re-inoculate if you don’t plant the seed within

48 hours.Mix small quantities in a five-gallonbucket or tub,either by hand or using a drillequipped with a paint-mixer attachment.Forlarger quantities,use special inoculant mixinghoppers or a cement mixer without baffles.Gum arabic stickers with sugars and liming

agents boost the chances for optimumnodulation over water-applied inoculant alone.Pre-inoculated (“rhizo-coated”) seed weighsabout one-third more than raw seed, soincrease seeding rates accordingly.

Check nodulation as the plants approachbloom stage. Push a spade in the soil about 6inches below the plant. Carefully lift the plantand soil, gently exposing roots and nodules.(Yanking roots from the soil usually strips offnodules).Wash gently in a bucket of water tosee the extent of nodulation. Slice opennodules.A pink or reddish interior indicatesactive N-fixation. Remember, anoverabundance of soil nitrogen from fertilizer,manure or compost can reduce nodulation.For more information about nodulation, see

two books by Marianne Sarrantonio:NortheastCover Crop Handbook (361) andMethodologies for Screening Soil-ImprovingLegumes (360).

tivar. BIGBEE is susceptible to crown rot and otherroot diseases common to forage legume species(162).Berseem, like other clovers, shows little resis-

tance to root-knot nematode (Meloidogyne spp.).It seems to be particularly favored by rabbits(361).

Crop SystemsFlexible oats booster. In the Corn Belt,berseemclover seeded with oats helps diversify corn>soy-bean rotations, breaks pest cycles and providessome combination of grain and/or forage harvest,erosion control and N to the following corn crop.An added benefit is that it requires no tillage orherbicide to kill it in spring (159).Plant 4 bu.oatswith 12 lb. berseem/A.


In a four-year Iowa study, planting berseemclover with oats increased net profit comparedwith oats alone.The clover was baled for forageand the underseeded oats were harvested forgrain. Not calculated in the benefit were the 40to 60 lb. N/A provided to the following corncrop or other soil-improvement benefits. The

oats/ berseem mix pro-duced 70 percent morebiomass, increased sub-sequent corn yields by10 percent and reducedweed competition com-pared with a year ofoats alone (159).Pure berseem clover

regrowth averaged 1.2T dry matter/A, whichcan be used as forage orgreen manure. Theseoptions could help oats

become an economically viable crop for Midwestcrop/livestock farms in an era of decreasinggovernment payments for corn and soybeans(159, 160).

Wheat companion. Berseem was one of sixlegume intercrops that improved productivityand profit of wheat and barley crops in low-Nsoils under irrigated conditions in northwesternMexico. All of the legumes (including commonand hairy vetch,crimson clover,New Zealand andLadino white clover, and fava beans) providedmultiple benefits without decreasing grain yieldof 15 to 60 bu./A on the heavy clay soil.Wheat and legumes were planted at normal

monoculture rates with wheat in double rowsabout 8 inches apart atop 30-inch beds, andlegumes in the furrows. In a second, relatedexperiment, researchers found they could morethan double total wheat productivity (grain andtotal dry matter) by interplanting 24-inch strips ofberseem clover or hairy vetch with double rowsof wheat 8 inches apart. Control plots showedwheat planted at a greater density did notincrease yield (350).

Vegetable overseeding. Berseem can be over-seeded into spring vegetables in northern cli-mates where it thrives at moderate temperaturesand moisture. Berseem is well suited to a “mowand blow” system where strips of green manureare chopped and transferred to adjacent cropstrips as a green manure and mulch (361).Boost the N plow-down potential of old pas-

tures or winter-killed alfalfa by no-tilling or inter-seeding berseem clover. Or, broadcast seed thenincorporate with light harrowing.

COMPARATIVE NOTES

Berseem clover is:• Not as drought-tolerant as alfalfa. Some culti-vars can tolerate more soil moisture—but notwaterlogging—than alfalfa or sweet clover

• Similar in seed size to crimson clover• Bee-friendly because its white or ivory blos-soms have no tripping mechanism.

• Because of its short roots, berseem cloverdoes not use phosphorus to the depth thatmature, perennial alfalfa does.

• Winterkilled berseem allows for earlier springplanting than winter-hardy annuals. As a deadorganic mulch, it poses no moisture depletionrisk, but may slow soil warming and dryingcompared to erosion-prone bare fallow.

Cultivars. BIGBEE berseem clover was selectedfrom other traditional cultivars for its cold-toler-ance, which is similar to crimson clover. Some ofthe strong winter production tendency found innon-winter hardy berseem clover was sacrificedto obtain BIGBEE’s winter hardiness (162). MatureBIGBEE plants hold their seeds well and produceadequate hard seed for reseeding.Other berseemclover cultivars have less hard seed and will notdependably reseed (278).California tests show MULTICUT berseem clover

produces 20 to 25 percent more dry matter thanBIGBEE. It has greater N-fixing ability, blooms later,and has a longer growing period than other vari-eties, but is not as cold tolerant as BIGBEE (162).JOE BURTON, developed from MULTICUT, is morecold tolerant.

Mow strips of

berseem between

vegetable rows

and blow the

clippings around

the plants

for mulch.

COWPEAS 125

In California, BIGBEE begins to flower in mid-May, about two weeks ahead of MULTICUT.MULTICUT grows faster and produces more drymatter in California conditions, averaging about1.6 T/A more in a six-year study.When the five orsix cuttings per year were clipped and removed,

MULTICUT was about 6 inches taller at each clip-ping than other varieties (447). In Montana tests,BIGBEE out-yielded MULTICUT in eight of 13 loca-tions (381).


Cowpeas are the most productive heat-adapted legume used agronomically in theU.S. (275).They thrive in hot, moist zones

where corn flourishes, but require more heat foroptimum growth (263).Cowpea varieties have di-verse growth habits. Some are short,upright bushtypes. Taller,viny types are more vigorous and bet-ter suited for use as cover crops.Cowpeas protectsoil from erosion, smother weeds and produce100 to 150 lb. N/A. Dense residue helps toimprove soil texture but breaks down quickly inhot weather. Excellent drought resistance com-bined with good tolerance of heat, low fertilityand a range of soils make cowpeas viable through-out the temperate U.S.where summers are warmor hot but frequently dry.

Cowpeas make an excellent N source ahead offall-planted crops and attract many beneficialinsects that prey on pests. Used in California invegetable systems and sometimes in tree crops,cowpeas also can be used on poor land as part ofa soil-building cover crop sequence.

BENEFITS

Weed-smothering biomass. Drilled or broadcastcowpea plantings quickly shade the soil to blockout weeds.Typical biomass production is 3,000 to4,000 lb./A (361). Cowpeas produced about 5,100lb. drymatter/A in a two-year Nebraska screening ofcover crops while soybeans averaged about 7,800lb.DM/A in comparison plots (332).

COWPEASVigna unguiculata

Also called: southern peas, black-eye peas, crowder peas

Type: summer annual legume

Roles: suppress weeds, N source,build soil, prevent erosion, forage

Mix with: sorghum-sudangrasshybrid or foxtail hay-type millet formulch or plow-down before veg-etables; interseeded with corn orsorghum


summer annual


Thick stands that grow well can outcompetebermudagrass where it does not produce seedand has been plowed down before cowpeaplanting (263). In New York, both cowpea andsoybean provided some weed-suppressing bene-fits. Neither adequately controlled weeds, butmixing with buckwheat or sorghum-sudangrassimproved performance as a weed managementtool (43).In California, cowpea mulch decreased weed

pressure in fall-planted lettuce, while incorporat-ed cowpea was less effec-tive. An excellent desertcover crop, cowpea alsoreduced weed pressurein California pepper pro-duction (209).The weed-suppressing

activity of cowpea maybe due, in part, to allelo-pathic compounds in theresidue. The same com-pounds could adversely

impact your main crop. Be sure to consult localinformation about impacts on cash crops.

Quick green manure. Cowpeas nodulate pro-fusely, producing an average of about 130 lb.N/Ain the East, and 200 lb.N/A in California. Properlyinoculated in nitrogen deficient soils, cowpeascan produce more than 300 lb. N/A (120).Plowdown often comes 60 to 90 days after plant-ing in California (275).Higher moisture and moresoil N favor vegetative growth rather than seedproduction. Unlike many other grain legumes,cowpeas can leave a net gain of nitrogen in thefield even if seed is harvested (361).

IPM insectary crop. Cowpeas have “extrafloralnectaries”—nectar-release sites on petioles andleaflets—that attract beneficial insects, includingmany types of wasps,honeybees,lady beetles,antsand soft-winged flower beetles (422). Plants havelong, slender round pods often borne on barepetioles above the leaf canopy.Intercropping cotton with cowpeas in India

increased levels of predatory ladybugs andparasitism of bollworms by beneficial wasps.

Intercropping with soybeans also increased para-sitism of the bollworms compared with plotsintercropped with onions or cotton without anintercrop.No effects on overall aphid, leafhopperor bollworm populations were observed (422).

Companion crop. Thanks to its moderate shadetolerance and attractiveness to beneficial insects,cowpeas find a place in summer cover crop mix-tures in orchards and vineyards in the moretemperate areas of California. Avoid use under aheavy tree canopy, however, as cowpeas are sus-ceptible to mildew if heavily shaded (263).As inmuch of the tropical world where cowpeas are apopular food crop, they can be underseeded intocorn for late-season weed suppression and post-harvest soil coverage (361).

Seed and feed options. Cowpea seed (yieldrange 350 to 2,700 lb./A) is valued as a nutrition-al supplement to cereals because of complemen-tary protein types.Seed matures in 90 to 140 days.Cowpeas make hay or forage of highest feed valuewhen pods are fully formed and the first haveripened (120).A regular sickle-bar mower worksfor the more upright-growing cultivars (120,422).Crimping speeds drying of the rather fleshy stemsto avoid over-drying of leaves before baling.

Low moisture need. Once they have enoughsoil moisture to become established, cowpeas area rugged survivor of drought. Cowpeas’ delayedleaf senescence allows them to survive and recov-er from midseason dry spells (21).Plants can sendtaproots down nearly 8 feet in eight weeks toreach moisture deep in the soil profile (107).

Cultivars for diverse niches. Cover crop culti-vars include CHINESE RED, CALHOUN and REDRIPPER, all viny cultivars noted for superior resis-tance to rodent damage (317). IRON CLAY, a mix-ture of two formerly separate cultivars widelyused in the Southeast, combines semi-bushy andviny plants and resistance to rootknot nematodesand wilt.Most of the 50-plus commercial cowpea culti-

vars are horticultural. These include “crowderpeas” (seeds are crowded into pods), grownthroughout the temperate Southeast for fresh pro-

Cowpeas thrive

under hot, moist

conditions, but

also tolerate

drought and low

soil fertility.

COWPEAS 127

cessing,and“blackeye peas,”grown for dry seed inCalifornia.Watch for the release of new varietiesfor cover crop use.Use leafy,prostrate cultivars for the best erosion

prevention in a solid planting. Cultivars vary sig-nificantly in response to environmental condi-tions. Enormous genetic diversity in more than7,000 cultivars (120) throughout West Africa,SouthAmerica andAsia suggests that breeding forforage production would result in improved culti-vars (21, 422) and cover crop performance.

Easy to establish. Cowpeas germinate quickly andyoung plants are robust, but they have more diffi-culty emerging from crusted soils than soybeans.

MANAGEMENT

EstablishmentDon’t plant cowpeas until soil temperature is aconsistent 65° F and soil moisture is adequate forgermination—the same conditions soybeansneed. Seed will rot in cool, wet soils (107).Cowpeas for green manure can be sown later insummer (361), until about nine weeks beforefrost. Cowpeas grow in a range of well-drainedsoils from highly acid to neutral, but are less welladapted to alkaline soils.They will not survive inwaterlogged soils or flooded conditions (120).In a moist seedbed, drill cowpeas 1 to 2 inches

deep at about 30 to 90 lb./A,using the higher ratein drier or cooler areas or for larger-seeded culti-vars (361, 422).While 6- to 7-inch row spacingsare best for rapid groundcover or a short growingseason,viny types can be planted in 15- to 30-inchrows. Pay particular attention to pre-plant weedcontrol if you go with rows, using pre-cultivationand/or herbicides.If you broadcast seed, increase the rate to about

100 lb./A and till lightly to cover seed. A lowerrate of 70 lb./A can work with good moisture andeffective incorporation (361). Broadcast seedingusually isn’t as effective as drilling, due to cow-peas’ large seed size.You can plant cowpeas afterharvesting small grain, usually with a single disk-ing if weed pressure is low.No-till planting is alsoan option. Use special “cowpea” inoculant whichalso is used for sunn hemp (Crotolaria juncea),

another warm-season annual legume.See Up-and-Coming Cover Crops (p. 191).

Field ManagementCowpea plants are sometimes mowed or rolled tosuppress regrowth before being incorporated forgreen manure. It’s best to incorporate cowpeaswhile the entire crop is still green (361) for quick-est release of plant nutrients. Pods turn cream orbrown upon maturity and become quite brittle.Stems become more woody and leaves eventuallydrop.Crop duration and yield are markedly affected

by night and day temperatures as well as daylength. Dry matter production peaks at tempera-tures of 81° F day and 72° F night (120).

KillingMowing at any point stops vegetative develop-ment, but may not kill plants without shallowtillage. Mowing and rolling alone do not consis-tently kill cowpeas (95). Herbicides can also beused. If allowed to go to seed, cowpeas canvolunteer in subsequent crops.

Pest ManagementFarmers using cowpeas as cover crops do notreport problems with insects that are pests incommercial cowpea production, such as Lygusbugs and 11-spotted cucumber beetle (95, 83).Insect damage to cowpea cover crops is mostlikely to occur at the seedling stage.

COWPEAS (Vigna unguiculata) MarianneSarrantonio


PARTRIDGE,Kan.—Cowpeas fill a rotationalrough spot between milo (grain sorghum) andwheat for Jim French,who farms about 640acres near Partridge,Kan.“I miss almost a full season after we take off

the milo in late October or November until weplant wheat the following October,” saysFrench.“Some people use cash crops such asoats or soybeans. But with cowpeas, I get winderosion control, add organic matter to improvesoil tilth, save on fertilizer and suppress weedsfor the wheat crop. Plus I have the options ofhaying or grazing.”He chisel plows the milo stubble in late

April, disks in May and field cultivates justbefore planting about the first week of June.He drills 30 to 40 lb./A of CHINESE REDcowpeas 1 to 2 inches deep when soiltemperature reaches 70° F.Growth is rapid,and by early August he kills the cowpeas bymaking hay, having his cattle graze them off orby incorporating them for maximum soilbenefit.French says cowpeas usually produce about

90 to 120 lb.N/A—relatively modest for alegume cover—but he feels his soil greatlybenefits from the residue,which measured8,000 lb./A in one of his better fields.He disksthe sprawling, leafy legume once, then does ashallow chisel plowing to stop growth andsave moisture. Breakdown of the somewhattough stems depends on moisture.When he leaves all the cowpea biomass in

the field, he disks a second time to speed

decomposition.He runs an S-tine fieldcultivator 1 to 2 inches deep just beforeplanting wheat to set back fall weeds, targetinga 20 to 25 percent residue cover.The cowpeasimprove rainfall infiltration and the overallability of the soil to hold moisture.French observes that the timing of rainfall

after cowpea planting largely determines theweediness of the cover crop.“If I get a weekto 10 days of dry weather after I plant intomoisture, the cowpeas will out-compete theweeds. But if I get rain a few days afterplanting, they’ll be weedy.”French manages his legumes to stay in

compliance with USDA farm programprovisions.The Freedom to FarmAct allowsvegetables used as green manure, haying orgrazing to be planted on program acres, butprohibits planting vegetables for seed harveston those acres.The rules list cowpeas as avegetable, even though different cultivars areused for culinary production.Use of grainlegumes such as lentils,mung beans and drypeas (including Austrian winter peas) is notrestricted by the act, opening flexible rotationoptions.French cooperated with Rhonda Janke of

Kansas State University to define soil healthmore precisely.He can tell that covers improvethe“flow”of his soil, and he is studying rootgrowth after covers. But he feels her workmeasuring enzymes and carbon dioxide levelswill give farmers new ways to evaluatemicrobial activity and overall soil health.

Cowpeas Provide Elegant Solution to Awkward Niche

Once cowpea plants form pods, they mayattract stinkbugs,a serious economic pest in partsof the lower Southeast. However, no significantstinkbug presence was reported in three years ofscreening in North Carolina. If stinkbugs are aconcern, remember these points:• Flail mowing or incorporating cowpeas atpod set will prevent a stinkbug invasion. Bythat time, cowpeas can provide good weed

suppression and about 90 percent of theirnitrogen contribution.However,waiting toolong before mowing or incorporation willflush stinkbugs into adjacent crops. Leavingremnant strips of cowpeas to attract stinkbugsmay reduce movement into other crops, aslong as the cowpeas keep producing enoughnew pods until the cash crop is no longerthreatened.

COWPEAS 129

• Plan crop rotations so the preceding, adjacentand succeeding crops are not vulnerable orare resistant to stinkbugs.

• If you plan to use an insecticide to controlanother pest, the application may also helpmanage stinkbugs.

No cowpea cultivar is resistant to root rot, butthere is some resistance to stem rot. Persistentwet weather before development of the first trueleaf and crowding of seedlings due to poor seedspacing may increase damping off.To reduce dis-ease and nematode risks, rotate with four or fiveyears of crops that aren’t hosts. Also plant seedinto warm soils and use certified seed of tolerantvarieties (107). IRON and other nematode-tolerantcowpea cultivars reduced soybean cyst and root-knot nematode levels in greenhouse experiments(422). Despite some research (422) showing anincreased nematode risk after cowpeas,Californiafarmers report no such problem.

Crop SystemsCowpeas’ heat-loving nature makes them an idealmid-summer replenisher of soil organic matterand mineralizable nitrogen. Cowpeas set podsover a period of several weeks.Viny varieties con-tinue to increase dry matter yields during thattime.A mix of 15 lb. cowpeas and 30 lb. buck-

wheat/A makes it possible to incorporate thecover crop in just six weeks while still providingsome nitrogen. Replacing 10 percent of the nor-mal cowpea seeding rate with a fast-growing,drought-tolerant sorghum-sudangrass hybridincreases dry matter production and helps sup-port the cowpea plants for mowing. Cowpeasalso can be seeded with other tall annual cropssuch as pearl millet. Overseeding cowpeas intonearly mature spring broccoli in June in Zones 5and 6 of the Northeast suppresses weeds whileimproving soil (361). Planting cowpeas in lateJune or early July in the upper Midwest afterspring canning peas provides green manure or anemergency forage crop (422).

Cowpeas can fill a mid-summer fallow niche ininland North Carolinabetween spring and sum-mer vegetable crops. A mixof IRON AND CLAY cowpeas(50 lb./A) and German mil-let (15 lb./A) planted in lateJune can be killed mechani-cally before no-till trans-planted fall broccoli. Inseveral years of screeningtrials at the same sites, cow-pea dry matter (3,780 lb./A) out yielded soybeans(3,540 lb. DM/A), but plots of sesbania (Sesbaniaexaltata) had top yields at about 5,000 lb.DM/A (95).

COMPARATIVE NOTES

Cowpeas are more drought tolerant than soy-beans, but less tolerant of waterlogging (361) andfrost (263). Sown in July, the cowpea canopyclosed more rapidly and suppressed weeds betterthan lespedeza (Lespedeza cuneata), Americanjointvetch (Aeschynomene americana), sesbaniaand alyceclover (Alysicarpus spp.), the otherwarm-season legumes tested (422).Cowpeas per-form better than clovers and alfalfa on poor oracid soils. Cowpea residue breaks down fasterthan white sweetclover (361) but not as fast asAustrian winter peas.Warm-season alternatives to cowpeas include

two crops that retain some cowpea benefits.Buckwheat provides good beneficial habitat andweed control without attracting stinkbugs.Velvetbeans (Mucuna deeringiana) providenitrogen, soil protection and late-season forage inhot, long-season areas. They do not attractstinkbugs and are resistant to nematodes (107).

Cultivars. See Cultivars for diverse niches(p. 126).


Unlike many

grain legumes,

cowpeas can

leave a net N

gain even if

seeds are

harvested.


With its rapid, robust growth, crimsonclover provides early spring nitrogenfor full-season crops. Rapid fall growth,

or summer growth in cool areas, also makes it atop choice for short-rotation niches as a weed-suppressing green manure. Popular as a stapleforage and roadside cover crop throughout theSoutheast, crimson clover is gaining increasedrecognition as a versatile summer-annual cover incolder regions. Its spectacular beauty when flow-ering keeps it visible even in a mix with otherflowering legumes, a common use in Californianut groves and orchards. In Michigan, it is usedsuccessfully between rows of blueberries.

BENEFITS

Nitrogen source.Whether you use it as a springor fall N source or capitalize on its vigorousreseeding ability depends on your location.Growers in the “crimson clover zone”—east ofthe Mississippi, from southern Pennsylvania andsouthern Illinois south—choose winter annualcrimson clover to provide a strong, early N boost.In Hardiness Zone 8—the warmer half of theSoutheast—crimson clover will overwinterdependably with only infrequent winterkill. Its Ncontribution is 70 to 150 lb./A.

Reseeding cultivars provide natural fertility tocorn and cotton.Crimson clover works especiallywell before grain sorghum,which is planted laterthan corn. It is being tested extensively in no-tilland zone-till systems.One goal is to let the legumereseed yearly for no-cost, season-long erosion con-trol, weed suppression and nitrogen banking forthe next year.Along the northern edge of the“crimson clover

zone,”winterkill and fungal diseases will be moreof a problem. Hairy vetch is the less risky over-wintering winter annual legume, here and innorthern areas. Crimson clover often can survivewinters throughout the lower reaches of Zone 6,especially from southeastern Pennsylvania north-east to coastal New England (195).Crimson clover is gaining popularity as a win-

ter-killed annual, like oats, in Zones 5 and colder.Planted in late summer, it provides good ground-cover and weed control as it fixes nitrogen fromthe atmosphere and scavenges nitrogen from thesoil. Its winterkilled residue is easy to manage inspring.

Biomass. As a winter annual, crimson clover canproduce 3,500 to 5,500 lb.dry matter/A and fix 70to 150 lb. N/A by mid-May in Zone 8 (the inlandDeep South). In a Mississippi study, crimson clover

CRIMSON CLOVERTrifolium incarnatum

Type: winter annual or summerannual legume

Roles: N source, soil builder,erosion prevention, reseedinginter-row ground cover, forage

Mix with: rye and other cereals,vetches, annual ryegrass, subclover,red clover, black medic


not recommended

winter annual

summer annual

marginal (limited by heat, rainfall, short season)

CRIMSON CLOVER 131

had produced mature seed by April 21, as well as5,500 lb.DM and 135 lb.N/A.The study concludedthat crimson clover is one of several winter annuallegumes that can provide adequate but not exces-sive amounts of N for southern grain sorghum pro-duction (22,36,105).Crimson clover has producedmore than 7,000 lb.DM/A several times at a USDA-ARS site in Beltsville, Md., where it produced 180lb.N and 7,800 lb.DM/A in 1996 (412).In field trials of six annual legumes in

Mississippi, crimson clover was found to producethe most dry matter (5,600 to 6,000 lb./A) com-pared to hairy vetch, bigflower vetch, berseemclover, arrowleaf clover (Trifolium vesiculosum)and winter peas. It produced 99 to 130 lb. N/Aand is recommended for soil erosion controlbecause of its high early-autumn dry matter pro-duction (426).As a summer annual in lower Michigan, a mid-

summer planting of crimson clover seeded at 20lb./A produced 1,500–2,000 lb.dry matter and 50-60 lb.N/A by late November (270).

Mixtures. Crimson clover grows well in mixtureswith small grains, grasses and other clovers. Anoats crop is a frequent companion, either as anurse crop to establish a clear stand of crimsonclover, or as a high-biomass, nutrient-scavengingpartner. In California, crimson clover is plantedwith rose clover and medics in orchards and nutgroves to minimize erosion and provide some Nto tree crops (422).

Beneficial habitat and nectar source. Crimsonclover has showy,deep red blossoms 1/2 to 1 inchlong.They produce abundant nectar, and are visit-ed frequently by various types of bees. Theblooms may contain many minute pirate bugs, animportant beneficial insect that preys on manysmall pests, especially thrips (422). In Michigan,crimson increased blueberry pollination whenplanted in row middles. Georgia research showsthat crimson clover sustains populations of peaaphids and blue alfalfa aphids.These species arenot pests of pecans, but provide alternative foodfor beneficial predators such as lady beetles,which later attack pecan aphids.

Nutrient cycler. Crimson clover adds to the soilorganic N pool by scavenging mineralized N andby normal legume N fixation. The scavengingprocess, accomplished most effectively by grass-es, helps reduce the potential for N leaching intogroundwater during winter and spring (181,265).Mixed with annual ryegrass in a simulated rainfallstudy, crimson clover reduced runoff from theherbicide lactofen by 94 percent and norflurazonand fluometuron by 100 percent (346). Thegrass/legume mixture combines fibrous surfaceroots with short tap roots.

MANAGEMENT

Establishment & FieldworkCrimson clover will grow well in about any typeof well drained soil, especially sandy loam. It mayfare poorly on heavy clay,waterlogged, extremelyacid or alkaline soils. Once established, it thrivesin cool, moist conditions. Dry soil often hindersfall plantings in the South.Inoculate crimson clover if it hasn’t been

grown before. Research in Alabama showed thatdeficiencies of phosphorus or potassium—orstrongly acidic soil with a pH of less than 5.0—can virtually shut down N fixation. Noduleswere not even formed at pH 5.0 in the test.Phosphorus deficiency causes many small butinactive nodules to form (188).

CRIMSON CLOVER (Trifolium incarnatum)

MarianneSarrantonio


Winter annual use. Seed six to eight weeksbefore the average date of first frost at 15 to 18lb./A drilled, 22 to 30 lb./A broadcast. As withother winter legumes, the ideal date varies withelevation. In North Carolina, for example, the rec-ommended seeding dates are three weeks lateralong the coast than in the mountains.Don’t plant too early or crimson clover will go

to seed in the fall and not regrow in spring untilthe soil warms up enoughto germinate seeds.Early tomid-August seeding is com-mon in the northern partof crimson clover’s winter-annual range. In southernMichigan (Zone 5b - 6a)crimson clover, no-tilledinto wheat stubble in mid-July, not only grew wellinto fall,but thrived the fol-lowing spring, performingnearly as well as hairyvetch (270).

While October plantings are possible in thelower Mississippi Delta,anAugust 15 planting in anorthern Mississippi test led to higher yields thanlater dates (228). In the lower Coastal Plain of theGulf South, crimson clover can be planted untilmid-November.Nutrient release from crimson clover residue—

and that of other winter annual legumes—isquicker if the cover crop is tilled lightly into thesoil. Apart from erosion concerns, this fertilityenhancing step adds cost and decreases theweed-suppression effect early in the subsequentcrop’s cycle.

Summer annual use. In general,plant as soon asall danger of frost is past. Spring sowing establish-es crimson clover for a rotation with potatoes inMaine. In Michigan, researchers have successfullyestablished crimson clover after short-seasoncrops such as snap beans (229, 270).In Northern corn fields, Michigan studies

showed that crimson clover can be overseeded atfinal cultivation (layby) when corn is 16 to 24inches tall. Crimson clover was overseeded at 15lb./A in 20-inch bands between 30-inch rows

using insecticide boxes and an air seeder. Theclover established well and caused no corn yieldloss (295).Crimson clover has proved to be morepromising in this niche than black medic, redclover or annual ryegrass, averaging 1,500 lb.DM/A and more than 50 lb.N/A (270).In Maine, spring-seeded crimson clover can

yield 4,000 to 5,000 lb.DM/A by July,adding 80 lb.N/A for fall vegetables. Mid-July seedings haveyielded 5,500 lb./A of weed-suppressing biomassby late October. Summer-annual use is plannedwith the expectation of winterkill. It sometimessurvives the winter even in southern Michigan(270), however, so northern experimentersshould maintain a spring-kill option if icy windsand heaving don’t do the job.In California, spring sowing often results in

stunting, poor flowering and reduced seed yield,and usually requires irrigation (422).

Rotations. In the South, crops harvested in earlyfall or sown in late spring are ideal in sequencewith crimson clover.Timely planting of crimsonclover and its rapid spring growth can enable it toachieve its maximumN contribution,and perhapsreseed.While corn’s early planting date and cot-ton’s late harvest limit a traditional winter-annualrole for crimson clover, strip planting and zonetillage create new niches. By leaving unkilledstrips of crimson clover to mature between zone-tilled crop rows, the legume sets seed in May.The majority of its hard seed will germinate in fall.Kill crimson clover before seed set and use

longer season cultivars where regrowth fromhard seed would cause a weed problem.Researchers have successfully strip-tilled into

standing crimson clover when 25 to 80 percent ofthe row width is desiccated with a herbicide ormechanically tilled for the planting area.Narrower strips of crimson clover increasedweed pressure but reduced moisture competi-tion, while wider strips favored reseeding of thecover (236).In a crimson clover-before-corn system, grow-

ers can optimize grain yields by no-tilling into thecrimson clover and leaving the residue on the sur-face, or optimize total forage yield by harvestingthe crimson clover immediately before planting

In Hardiness

Zone 5 and

colder, crimson

clover can

provide a

winterkilled

mulch.

CRIMSON CLOVER 133

corn for grain or silage (204). In Mississippi, sweetpotatoes and peanuts suffered no yield or qualitypenalty when they were no-tilled into killed crim-son clover.The system reduced soil erosion anddecreased weed competition (35).In Ohio, crimson clover mixed with hairy

vetch, rye and barley provided a fertility enhanc-ing mulch for no-till processing tomato trans-plants. Use of a prototype undercutter implementwith a rolling harrow provided a good kill.Because the wide blades cut just under the soilsurface on raised beds, they do not break stalks,thus lengthening residue durability.The long-last-ing residue gave excellent results, even underorganic management without the herbicides,insecticides or fungicides used on parallel plotsunder different management regimes. NancyCreamer at the University of North Carolina iscontinuing work on the undercutter and on covercrops in organic vegetable systems (96).

Mixed seeding. For cover crop mixtures, sowcrimson clover at about two-thirds of its normalrate and the other crop at one third to one-half ofits monoculture rate. Crimson clover develop-ment is similar to tall fescue. It even can be estab-lished with light incorporation in existing standsof aggressive grasses after they have been closelymowed or grazed.

Reseeding. Overwintered crimson clover needssufficient moisture at least throughout April toproduce seed (130). Cultivar selection is criticalwhen early spring maturity is needed.DIXIE and CHIEF are full-season standards. AU

ROBIN and FLAME beat them by about two weeks;a new cultivar, AU SUNRISE, is reportedly 1-3weeks earlier; the popular TIBBEE is about a weekahead of the standards. Price varies more byseasonal supply than by cultivar.

Killing. Its simple taproot makes crimson clovereasy to kill mechanically. Mowing after early budstage will kill crimson clover.Maximum N is avail-able at late bloom or early seed set,even before theplant dies naturally.Killing earlier yields less N—upto 50 lb.N/A less at its late vegetative stage,whichis about 30 days before early seed set (342).

A rolling stalk chopper flattens a mix of crim-son clover,hairy vetch and rye ahead of no-till veg-etable transplanting at Steve Groff’s farm insoutheastern Pennsylvania. The crimson is killedcompletely if it is in full bloom; and even earlybloom is killed better than vegetative crimson.

Pest ManagementCrimson clover is a secondary host to plant pestsof the Heliothus species,which include cornearworm and cottonbollworm. Despite itsknown benefits,crimsonclover has been eradicat-ed from many miles ofroadsides in Mississippiat the request of someDelta farmers who sus-pect it worsens prob-lems from those pests (106).Crimson clover doesn’t significantly increase

risk of Southern corn rootworm in no-till corn,while hairy vetch does (67). It is more resistant todiseases (422) and to some nematodes than otherclovers (337). Crimson clover is said to tolerateviral diseases, but it succumbed to virus in Julyplantings in Mississippi (228) and to Sclerotiniain fall plantings in Maryland (108).In lab tests, crimson clover,berseem clover and

hairy vetch have been shown to inhibit germina-tion and seedling development of onion, carrotand tomato (40).However,this interference hasn’tbeen observed in North Carolina field cropswhere strips are mechanically tilled, or in otherstudies with crimson clover as part of a killedorganic mulch.No-till vegetable transplanting hasbeen done successfully on the same day asmechanically killing the cover crop mix on SteveGroff’s Lancaster County, Pa., farm with no nega-tive effects.Wait two to three weeks after killing before

planting seeds, to allow the biomass to begin todecompose and the soil biological life to stabilize.During this time, a flush of bacteria such asPythium and Rhizoctonia attack rapidly decayingplants. These bacteria also can attack seedlingcrops.To plant more quickly,mow the clover and

In Mississippi,

crimson clover

produced mature

seed and 135 lb.

N/A by April 21.


use row cleaners to clear the tops from theseed zone. The mow/wait/plant cycle also maybe influenced by the need to wait for rain toincrease seedbed moisture.Mixed with hairy vetch,crimson clover attracts

beneficial insects, provides nitrogen and sup-presses weeds in Oklahoma’s native and planta-tion pecan groves. Both legumes go to seed andthen are harvested for forage. Arrowleaf cloverprovided more biomass and N,but didn’t work aswell for insect pest management and is very sus-ceptible to root knot nematode.Crimson clover harbors flower thrips and is a

more likely host for tarnished plant bug thanhairy vetch or subterranean clover (56). Intensivescreenings show less abundant arthropod herbi-vores and predators on crimson clover than onhairy vetch (206).Tillage practices and residue management vari-

ations (no-till, incorporate, removal) of covercropped lupin, rye, hairy vetch or crimson cloverhad little consistent effect on nematodes in northFlorida corn fields (264).

Other OptionsPasture and hay crop. Crimson clover is excel-lent for grazing and haying.It will regrow if grazedor mowed no lower than 3 or 4 inches before the

early bud stage. Mixing with grass reduces itsrelatively low bloat risk even further. Timelymowing four to six weeks before bloom improvesgrowth, reduces lodging and will cause more uni-form flowering and seed ripening on highly fertilesoils (120, 422).Crimson clover can be grazed lightly in the fall,

more intensively in the spring and still be left toaccumulate N and/or set seed with little reduc-tion in its soil N contribution, provided livestockare removed before flowering (80).

COMPARATIVE NOTES

Crimson clover is:• less tolerant of mowing than are subclovers ormedics (422)

• similar to hairy vetch andAustrian winter peain the Southeast for total N production

• a better weed suppressor in fall than hairyvetch

• earlier to mature in spring than hairy vetch

Cultivars. See Reseeding (p. 154) for cultivarcomparisons.

Seed Sources. See Seed Suppliers (p. 195).

FIELD PEAS 135

Pisum sativum subsp. arvense

Also called: Austrian winter peas(black peas), Canadian field peas(spring peas)

Type: summer annual and winterannual legume

Roles: plow-down N source, weedsuppressor, forage

Mix with: strong-stemmed wheat,rye, triticale or barley for verticalsupport


the mid-Atlantic area.Risk of infection increases ifpea crops are grown on the same land in closerotation.Canadian field peas are a related strain of vining

pea. These annual “spring peas” can outgrowspring-planted winter peas. They often are seed-ed with triticale or another small grain. Springpeas have larger seeds, so there are fewer seedsper pound and seeding rates are higher,about 100to 160 lb./A.However, spring pea seed is a bit lessexpensive than Austrian winter pea seed. TRAPPERis the most common Canadian field pea cultivar.This section focuses on the widely grown

Austrian winter pea.“Field peas”refers to both thewinter and spring types.

BENEFITS

Bountiful biomass. Under a long, cool, moistseason during their vegetative stages, Austrianwinter peas produce more than 5,000 lb.dry mat-ter/A, even when planted in spring in colder cli-mates. Idaho farmers regularly produce 6,000 to8,000 lb. DM/A from fall-planted Austrian winterpeas. Because the residue breaks down quickly,only peas in the high-production areas build up

FIELD PEAS

summer annual

winter annual

High N-fixers, field peas produce abundantvining forage and contribute to short-termsoil conditioning. Succulent stems break

down easily and are a quick source of available N(361). Field peas grow rapidly in the cool, moistweather they encounter as winter annuals in theSouth and in parts of Idaho, and as early-sownsummer annuals in the Northeast, North Centraland Northern Plains areas. Harvest options ashigh-quality forage and seed increase their value.Winter-hardy types of field peas, especially

Austrian winter peas, can withstand tempera-tures as low as 10° F with only minor injury, butthey don’t overwinter consistently in areas colderthan moderate Hardiness Zone 6. They are sensi-tive to heat, particularly in combination withhumidity. They tend to languish in mid-summereven in the cool Northeast (361), where averagesummers have fewer than 30 days exceeding86° F. Temperatures greater than 90° F cause flow-ers to blast and reduce seed yield.On humus-richblack soils, field peas will produce abundant vinygrowth with few seed pods.Use in the East and Southeast is limited by field

peas’ susceptibility to Sclerotinia crown rot,which can destroy whole fields during winter in


much long-term organic matter.Peas do not makea good organic mulch for weed control (361).

Nitrogen source.Austrian winter peas are top Nproducers, yielding from 90 to 150 lb.N/A, and attimes up to 300 lb.N/A.Plowed down as green manure, fall-planted

legume crops of Austrian winter pea, alfalfa andhairy vetch each produced enough N for the pro-duction of high-quality muskmelons under plasticmulch and drip irrigation in a Kansas study.Melonyields produced with the legumes were similar tothose receiving synthetic fertilizer at 63 and 90 lb.N/A.The winter peas in the experiment produced96 lb. N/A the first year and 207 lb. N/A the sec-ond (387).Austrian winter peas harvested as hay then

applied as mulch mineralized N at more than dou-ble the rate of alfalfa hay.The N contribution wasmeasured the summer after a fall plowdown ofthe residue.The estimated N recovery of Austrianwinter pea material 10 months after incorpora-tion was 77 percent—58 percent through springwheat and 19 percent in the soil (254).Austrian winter pea green manure provided the

highest spring wheat yield the following year in aMontana trial comparing 10 types of medics,seven clovers, yellow biennial sweet clover andthree grains.Crops that produced higher tonnageof green manure usually had a negative effect onthe subsequent wheat crop due to moisture defi-ciency that continued over the winter betweenthe crops (381). Field peas can leave 80 lb.N/A ifterminated at mid-season in lieu of summer fallowin dryland areas, or leave more than 30 lb. N/Aafter pea harvest at season’s end (74).A winter pea green manure consistently result-

ed in higher malting barley protein content thanthat following other legumes or fallow in aMontana trial. Annual legumes harvested for seedleft less soil N than did plots in fallow. Also testedwere fava bean,lentil,chickpea,spring pea,winterpea hay and dry bean (262).

Rotational effects. Pulse crops (grain legumessuch as field peas, fava beans and lentils) improv-ed sustainability of dryland crop rotations by pro-

viding disease suppression, better tilth and otherenhancements to soil quality in a Saskatchewanstudy. Even at rates of 180 lb. N/A, fertilizer alonewas unable to bring yields of barley planted intobarley residue to the maximum achieved fromthese pulse residues (163).

Water thrifty. In a comparison of water usealongside INDIANHEAD lentils and GEORGE blackmedic, Austrian winter pea was the most mois-ture-efficient crop in producing biomass. Eachcrop had used 4 inches of water when Austrianwinter pea vines were 16 inches long, the lentilswere 6 to 8 inches tall and the black medic cen-tral tillers were 4 inches tall (383).Austrian winter peas grown in a controlled set-

ting at 50° F recorded more than 75 percent of itsN2 fixed per unit of water used by the 63rd day ofgrowth. White clover, crimson clover and hairyvetch reached the same level of water efficiency,but it took 105 days (334).

Quick growing. Rapid spring growth helps peasout compete weeds and make an N contributionin time for summer cash crops in some areas.

Forage booster. Field peas grown with barley,oat, triticale or wheat provide excellent livestockforage. Peas slightly improve forage yield, but sig-nificantly boost protein and relative feed value ofsmall grain hay.

Seed crop. Seed production in Montana is about2,000 lb./A and about 1,500 lb./A in the PacificNorthwest. Demand is growing for field peas asfood and livestock feed (74).

Long-term bloomer.The purple and white blos-soms of field peas are an early and extendedsource of nectar for honeybees.

Chill tolerant. Austrian winter pea plants maylose some of their topgrowth during freezes, butcan continue growing after temperatures fall aslow as 10° F. Their shallow roots and succulentstems limit their overwintering ability, however.Sustained cold below 18° F without snow cover

FIELD PEAS 137

usually kills Austrian winter pea (202). To maxi-mize winter survival:• Select the most winter-hardy cultivars avail-able—GRANGER, MELROSE and COMMONWINTER.

• Seed early enough so that plants are 6 to 8inches tall before soil freezes, because peas areshallow rooted and susceptible to heaving.Try to plant from mid-August to mid-September in Zone 5.

• Plant into grain stubble or a rough seedbed, orinterseed into a winter grain.These environ-ments protect young pea roots by suppressingsoil heaving during freezing and thawing.Trapped snow insulates plants, as well.

MANAGEMENT

Establishment & FieldworkPeas prefer well-limed,well-drained clay or heavyloam soils,near-neutral pH or above and moderatefertility. They also do well on loamy sands inNorth Carolina. Field peas usually are drilled 1 to3 inches deep to ensure contact with moist soiland good anchoring for plants.If you broadcast peas, incorporation will great-

ly improve stands, as seed left exposed on thesurface generally does not germinate well. Long-vined plants that are shallow-seeded at low seed-ing rates tend to fall over (lodge), lay against thesoil and rot. Combat this tendency by plantingwith a small grain nurse crop such as oats,wheat,barley,rye or triticale.Reduce the pea seeding rateby about one quarter—and grain by about onethird—when planting a pea/grain mix.Planted at 60 to 80 lb./A in Minnesota, Austrian

winter peas make a good nurse crop for alfalfa.Field pea seed has a short shelf life compared

with other crops.Run a germination test if seed ismore than two years old and adjust seeding rateaccordingly. If you haven’t grown peas in theseeded area for several years, inoculate immedi-ately before seeding.

West. In mild winter areas of California andIdaho, fall-plant for maximum yield. In those areas,you can expect spring-planted winter peas toproduce about half the biomass as those that are

fall-planted. Seed by September 15 in Zone 5 ofthe Inter-Mountain region in protected valleyswhere you’d expect mild winter weather andgood, long-term snow cover. October-plantedAustrian winter pea in the Zone 9 SacramentoValley of California thrive on cool, moist condi-tions and can contribute 150 lb. N/A by earlyApril.The general rule for other parts of the semi-arid

West where snow cover is dependable is to plantpeas in the fall after grain harvest. In these dryregions of Montana and Idaho, overseed peas at90 to 100 lb./A by “frostseeding” any time soilshave become too cold for pea germination. Besure residue cover is not too dense to allow seedto work into the soil through freeze/thaw cyclesas the soil warms (383).In the low-rainfall Northern Plains, broadcast

clear stands of peas in early spring at a similar ratefor the “Flexible Green Manure” cropping system(below). Seeding at about 100 lb./A compensatessomewhat for the lack of incorporation and pro-vides strong early competition with weeds (383).Plant as soon as soil in the top inch reaches 40° Fto make the most of spring moisture (74).A mixture of Austrian winter peas and a small

grain is suitable for dryland forage productionbecause it traps snow and uses spring moisture toproduce high yields earlier than spring-seededannual forages (74). With sufficient moisture,spring peas typically produce higher forage yieldsthan Austrian winter peas.

FIELD PEAS (Pisum sativum subsp. arvense)

MarianneSarrantonio


East. Planted as a companion crop in early springin the Northeast, Austrian winter peas may pro-vide appreciable N for summer crops byMemorial Day (361). In the mid-Atlantic,Austrianwinter peas and hairy vetch planted October 1and killed May 1 produced about the same total Nand corn yields (108).

Southeast. Seed by October 1 in the inland Zone8 areas of the South so that root crowns canbecome established to resist heaving. Peas pro-duce more biomass in the cooler areas of theSouth than where temperatures rise quickly inspring (74, 361). Peas planted in late October inSouth Carolina’s Zone 8 and terminated in mid- tolateApril produce 2,700 to 4,000 lb.dry matter/A(23).

KillingPeas are easily killed any time with herbicides, orby disking or mowing after full bloom,the stage ofmaturity that provides the optimum N contri-bution. Disk lightly to preserve the tender residuefor some short-term erosion control.

The downside to thequick breakdown of peavines is their slimy condi-tion in spring if they win-terkill, especially in dense,pure stands. Planting with awinter grain provides someprotection from winterkilland reduces matting ofdead pea vegetation.

Pest ManagementWinter peas break crop disease cycles, BenBurkett of Petal, Miss., has found. Septoria leafspot problems on his cash crops are reducedwhen he plants Austrian winter pea in fall aftersnap beans and ahead of collards and mustardgreens the next summer.Between October 15 andNovember 15, Burkett broadcasts just 50 lb./Athen incorporates the seed with a shallow pass ofhis field cultivator. They grow 3 to 6 inches tallbefore going dormant in late December in hisZone 8 location about 75 miles north of the Gulf

of Mexico. Quick regrowth starts about the thirdweek in January. He kills them in mid-April bydisking, then shallow plows to incorporate theheavy residue (202).Farmers and researchers note several IPM cau-

tions, because Austrian winter peas:• Host some races of nematodes• Are susceptible to winter Sclerotinia crownrot,Fusarium root rot as well as seed rot andblights of the stem, leaf or pod

• Are variably susceptible to the Ascochytablight (MELROSE cultivar has some resistance)

• Host the pathogen Sclerotinia minor. Therewas a higher incidence of leaf drop inCalifornia lettuce planted after Austrian winterpeas in one year of a two-year test (232).

Austrian winter peas were heavily damaged bySclerotinia trifoliorum Eriks in several years of afour-year study in Maryland,but the crop still pro-duced from 2,600 to 5,000 lb. dry matter/A peryear in four out of five years. One year DMproduction was only 730 lb./A.Mean N contribu-tion despite the disease was 134 lb. N/A. Overall,Austrian winter peas were rated as being moresuited for Maryland Coastal Plain use than in thePiedmont, due to harsher winters in the latterlocation (204).To combat disease, rotate cover crops to avoid

growing peas in the same field in successive years.To minimize disease risk, waiting several years isbest.To minimize risk of losing cover crop benefitsto Sclerotinia disease in any given season,mixwithanother cover crop such as cereal rye.

Crop SystemsNorthern Plains. Austrian winter peas (andother grain legumes) are increasingly used insteadof fallow in dryland cereal rotations. The legumeshelp prevent saline seeps by using excess soilmoisture between cereal crops.They also add Nto the system.The legume>cereal sequence startswith a spring- or fall-planted grain legume(instead of fallow), followed by a small grain.Peas work well in this system because they are

shallow-rooted and therefore do not extract deepsoil moisture.The pea crop is managed according

Winter pea

residue breaks

down and

releases N

quickly.

FIELD PEAS 139

to soil moisture conditions. Depending on grow-ing season precipitation, the peas can be grazed,terminated or grown to grain harvest. Growersterminate the crop when about 4 inches of plant-available water remains in the soil, as follows:• Below-normal rainfall—terminate the grainlegume early.

• Adequate rainfall—terminate the grainlegume when about 4 inches of soil waterremains. Residue is maintained for greenmanure,moisture retention and erosionprevention.

• Above-average rainfall—grow the crop tomaturity for grain harvest.

In conventional fallow systems, fields are leftunplanted to accumulate soil moisture for thecash crop.Weeds are controlled using tillage orherbicides.Grain legumes provide a soil-protecting alter-

native to fallow that can be managed to ensureadequate moisture for the cereal crop. Legumesprovide long-term benefits by producing N forthe subsequent crop, disrupting disease, insectand weed cycles and building soil.Austrian winter peas work in these rotations

where there is at least 18 inches of rain per year.INDIANHEAD lentils (Lens culinaris Medik), a spe-cialty lentil for cover crop use, are also widelyused in this system.Montana research shows that when soil mois-

ture is replenished by winter precipitation, annu-al legumes can substitute for fallow withoutsignificantly reducing the yield of the next barleycrop. Montana rainfall averages 12-16 inches,so peas are planted but can only be taken tograin harvest in above-normal rainfall years. Thelegume can generate income from harvest of itshay or grain or through fertilizer N savings fromthe legume’s contribution to the small grain crop(136).In Idaho, fall-seeded Austrian winter peas har-

vested for seed provided income, residual N fromthe pea straw and soil disease suppression in astudy of efficient uses of the legume cover. A croprotation of Austrian winter pea (for grain)>winterwheat>spring barley produced similar wheat

yields as did using the peas as green manure orleaving the field fallow in the first year. Whileneither Austrian winter pea green manure nor fal-low produced income, the green manureimproved soil organic matter and added more Nfor wheat than did summer fallow. Fallow causeda net soil capacity loss by “mining” finite soilorganic matter reserves (253).In a northern Alberta comparison of conven-

tional (tilled), chemical (herbicide) and green(field pea) fallow systems, spring-planted fieldpeas provided 72 lb. N/A, significantly more thanthe other systems.The field pea system was alsomore profitable when all inputs were considered,providing higher yield for two subsequentcash crops, higher incomeand improvement of soilquality (12).

Southeast. Fall-seededAustrian winter peas out-produced hairy vetch byabout 18 percent in bothdry matter and N produc-tion in a three-year test inthe Coastal Plain of NorthCarolina. When legumeswere grown with rye, wheat or spring oats,Austrian winter pea mixtures also had the highestdry matter yields. Over the three years, Austrianwinter peas ranked the highest (dry-matter andN) in the legume-only trials and as the legumecomponent of the legume/grain mixtures. Indescending order after the peas were hairy vetch,common vetch and crimson clover. The peaswere sown at 54 lb./A in the pure seedings and 41lb./A in mixtures (344).In the year of greatest N fixation, soil N in the

Austrian winter pea mixture treatments was 50percent greater than the average of all other treat-ments. Researchers noted that the bottom leavesof pea vines were more decomposed than otherlegumes, giving the crop an earlier start in N con-tribution. Further, soil N in the upper 6 inches ofsoil under the Austrian winter peas held 30 to 50percent of the total soil inorganic N in the winterpea treatments, compared with levels of less than

In the

Northeast,

spring-planted

peas can be

incorporated by

Memorial Day.


30 percent in the top soil layer for all other treat-ments. In situations where the early-summer Nrelease from peas could be excessive, mixingAustrian winter peas with a grain can moderatethe N contribution and slow down its release intothe soil (344).The carbon to nitrogen (C:N) ratio of plant mat-

ter is an indication of how rapidly vegetation will

break down. Mixtures of small grains withAustrian winter peas and the vetches had C:N val-ues from 13 to 34,but were generally under 25 to30,the accepted threshold for avoiding net immo-bilization of N (344).Austrian winter peas and crimson clover can

provide adequate N for conventionally planted cot-ton in South Carolina. In a three-year trial, fertilizer

Peas Do Double Duty for Kansas Farmer

PARTRIDGE,Kan.—Jim French figures Austrianwinter peas provide free grazing, free nitrogen,or both.The vining legume produces just asmuch N for the following grain sorghum cropeven if he lets his registered Gelbvieh herd eatall they want of the winter annual’s springgrowth.French farms on flat,well-drained sandy

loam soil near Partridge,Kan.He managesabout 640 acres each of cash crops (winterwheat and grain sorghum) and forages (alfalfa,sudangrass,winter peas and cowpeas, and anequal area in grass pasture). Peas follow wheatin the three-year crop rotation on his south-central Kansas farm.He chisel plows thewheat stubble twice about 7 inches deep,disks once to seal the surface, then controlsweeds as necessary with a light field cultivator.Between mid-September and mid-October he

inoculates about 30 lb./A of the peas and drillsthem with an old John Deere double-run diskdrill in 8-inch rows.Establishment is usuallygood,with his only anxiety coming duringfreeze-thaw cycles in spring.“Each time the peasbreak dormancy,start to grow,then get zappedwith cold again they lose some of their rootreserves and don’t have quite the resistance tofreezing they did.They’ll sprout back even ifthere’s vegetative freeze damage as long as theirfood reserves hold out,”French reports.Ironically, this spring freezing is less of a

problem further north where fields stay frozenlonger before a slower thaw.This works aslong as snow cover protects the peas from the

colder early and mid-winter temperatures. Inmost years, he sets up temporary fence andturns his cattle into the peas about April 1 atthe stocking rate of two animal units per acre.During the best years of mild weather andadequate moisture,“the cattle have a hard timekeeping up,” says French.Depending on hisneed for forage or organic matter, he leavesthe cattle in until he incorporates the peastubble, or gives it time to regrow.One reason he gets about the same 90 to 120

lb.N/A contribution with or without grazing isthat the winter pea plants apparently continueN fixation and root growth while being grazed.Soil tests show that 25 to 30 lb.N/A areavailable in the nitrate form at incorporation inlate spring,with the balance in an organic formthat mineralizes over the summer.Grazing thepeas helps to contain cheatgrass,which tendsto tie up N if it’s incorporated just ahead of hissorghum crop.French is sold on winter peas ahead of his

grain sorghum because it provides N whilereducing weed pressure from cheatgrass andpigweed and decreasing lodging from charcoalroot rot.The option to use the peas asforage—while still achieving adequatesorghum yield—lets him buy less processedfeed, improves livestock health and acceleratesconversion of the peas’ organic material intoavailable soil nutrients.“Winter peas work best where you integrate

crops and livestock,” says French.“They giveyou so many benefits.”

FIELD PEAS 141

rates of up to 150 lb. N/A made no improvementto cotton yield on the pea plots. The evaluationshowed that soil nitrate underAustrian winter peaspeaked about nine weeks after incorporation (22).Austrian winter peas achieved 50 to 60 percent

groundcover when they were overseeded atabout 75 lb./A into soybeans at leaf yellowing insoutheastern Pennsylvania, where they can sur-vive some winters. The peas produced nearly 2tons of dry matter and 130 lb. N/A by May 20 inthis test (191).Overseeding peas into corn at lastcultivation is not recommended due to poorshade tolerance.Austrian winter peas, like other hollow-

stemmed succulent covers such as vetch and favabeans, do not respond well to mowing or cuttingafter they begin to bloom. In their earlier stages,Austrian winter peas will regrow even whengrazed several times. See Peas Do Double Dutyfor Kansas Farmer (p. 140).After three years of moisture testing, Kansas

farmer Jim French can explain why he sees moresoil moisture after spring grazing than when thepeas are left to grow undisturbed.“There’s decreas-ing overall transpiration because there’s less leafarea to move moisture out of the soil into the air.Yet the root mass is about the same.”Ungrazed peaspump more water as they keep growing.

Other Options.Harvest field peas for hay when most of the podsare well formed. Use a mower with lifting guardsand a windrow attachment to handle the sprawl-ing vines.

COMPARATIVE NOTES

Field peas won’t tolerate field traffic due tosucculent stems (191). When selecting types,remember that long-vined varieties are better forweed control than short-vined types.

Cultivars. MELROSE,known for its winter-hardiness, is a cultivarof the Austrian winterpea type. Plantedthe first week ofSeptember in Idaho,MELROSE peas yielded300 lb.N/A and 6 tonsof dry matter the nextJune. Planted in mid-April, the cultivar yielded “just” 175 lb. N/A and3.5T dry matter/A (202).GRANGER is an improved winter pea that has

fewer leaves and more tendrils, which are stifferthan standard cultivars. It is more upright and itspods dry more quickly than other winter peatypes. MAGNUS field peas have out-producedAustrian winter peas in California and bloom upto 60 days earlier.


In dryland

systems, winter

peas produce

abundant biomass

with limited

moisture.


Few legumes match hairy vetch for springresidue production or nitrogen contribu-tion. Widely adapted and winter hardy

through Hardiness Zone 4 and into Zone 3 (withsnow cover), hairy vetch is a top N provider intemperate and subtropical regions.The cover grows slowly in fall, but root devel-

opment continues over winter. Growth quickensin spring,when hairy vetch becomes a sprawlingvine up to 12 feet long.Field height rarely exceeds3 feet unless the vetch is supported by anothercrop. Its abundant,viney biomass can be a benefitand a challenge. The stand smothers springweeds, however, and can help you replace all ormost N fertilizer needs for late-planted crops.

BENEFITS

Nitrogen source. Hairy vetch delivers heavycontributions of mineralized N (readily availableto the following cash crop). It can provide suffi-cient N for many vegetable crops,partially replaceN fertilizer for corn or cotton and increase cashcrop N efficiency for higher yield.In some parts of California and the East in Zone

6, hairy vetch provides its maximum N by safecorn planting dates. In Zone 7 areas of theSoutheast, the fit is not quite as good, but sub-stantial N from vetch is often available beforecorn planting.

Corn planting date comparison trials withcover crops in Maryland show that planting aslate as May 15 (the very end of the month-longlocal planting period) optimizes corn yield andprofit from the system. Spring soil moisture washigher under the vetch or a vetch-rye mixturethan under cereal rye or no cover crop. Killedvetch left on the surface conserved summer mois-ture for improved corn production (80,82,84,85,173, 243).Even without crediting its soil-improving bene-

fits, hairy vetch increases N response and pro-duces enough N to pay its way in many systems.Hairy vetch without fertilizer was the preferredoption for “risk-averse” no-till corn farmers inGeorgia, according to calculations comparingcosts, production and markets during the study.The economic risk comparison included crimsonclover,wheat and winter fallow.Profit was higher,but less predictable,if 50 pounds of N were addedto the vetch system (310).Hairy vetch ahead of no-till corn was also the

preferred option for risk averse farmers in a three-

HAIRY VETCHVicia villosa

Type: winter annual or summerannual legume

Roles: N source, weed suppressor,topsoil conditioner, reduce erosion

Mix with: small grains, field peas,bell beans, crimson clover, buck-wheat


vetch superior

vetch viable crimson clover superior

vetch, crimson transition zone

hairy vetch viable w/irrigation

Note: To roughly estimate hairy vetch N contri-bution in pounds per acre, cut and weigh freshvetch top growth from a 4-foot by 4-foot area.Multiply pounds of fresh vetch by 12 to gaugeavailable N,by 24 to find total N (377).For a moreaccurate estimate, see How Much N? (p. 22).

HAIRY VETCH 143

year Maryland study that also included fallow andwinter wheat ahead of the corn. The vetch-cornsystem maintained its economic advantage whenthe cost of vetch was projected at maximum his-toric levels, fertilizer N price was decreased, andthe herbicide cost to control future volunteervetch was factored in (173). In a related study onthe Maryland Coastal Plain, hairy vetch proved tobe the most profitable fall-planted, spring desiccat-ed legume ahead of no-till corn, compared withAustrian winter peas and crimson clover (243).In Wisconsin’s shorter growing season, hairy

vetch planted after oat harvest provided a grossmargin of $153/A in an oat/legume/corn rotation(1995 data).Profit was similar to using 160 lb.N/Ain continuous corn, but with savings on fertilizerand corn rootworm insecticide (400).Hairy vetch provides yield improvements

beyond those attributable to N alone.These maybe due to mulching effects, soil structureimprovements leading to better moisture reten-tion and crop root development, soil biologicalactivity and/or enhanced insect populations justbelow and just above the soil surface.

Soil conditioner. Hairy vetch can improve rootzone water recharge over winter by reducingrunoff and allowing more water to penetrate thesoil profile through macropores created by thecrop residue (143). Adding grasses that take up alot of water can reduce the amount of infiltrationand reduce the risk of leaching in soils with excessnutrients. Hairy vetch, especially an oats/hairyvetch mix, decreased surface ponding and soilcrusting in loam and sandy loam soils.Researchersattribute this to dual cover crop benefits: their abil-ity to enhance the stability of soil aggregates (par-ticles), and to decrease the likelihood that theaggregates will disintegrate in water (143).Hairy vetch improves topsoil tilth, creating a

loose and friable soil structure. Vetch doesn’tbuild up long-term soil organic matter due to itstendency to break down completely. Vetch is asucculent crop, with a relatively “low” carbon tonitrogen ratio. Its C:N ratio ranges from 8:1 to15:1, expressed as parts of C for each part of N.Rye C:N ratios range from 25:1 to 55:1, showingwhy it persists much longer under similar condi-

tions than does vetch.Residue with a C:N ratio of25:1 or more tends to immobilize N. For moreinformation, see How Much N? (p. 22), and therest of that section, Building Soil Fertility andTilth with Cover Crops (p. 16).

Early weed suppression. The vigorous springgrowth of fall-seeded hairy vetch out-competesweeds, filling in where germination may be a bitspotty. Residue from killed hairy vetch has a weakallelopathic effect, but it smothers early weedsmostly by shading the soil. Its effectiveness wanesas it decomposes,falling off significantly after aboutthree or four weeks.For optimal weed control witha hairy vetch mulch, select crops that form a quickcanopy to compensate for the thinning mulch oruse high-residue cultivators made to handle it.Mixing rye and crimson clover with hairy vetch

(seeding rates of 30,10,and 20 lb./A,respectively)extends weed control to five or six weeks, aboutthe same as an all-rye mulch. Even better, the mixprovides a legume N boost,protects soil in fall andwinter better than legumes, yet avoids the poten-tial crop-suppressing effect of a pure rye mulchon some vegetables.

Good with grains. For greater control of winterannual weeds and longer-lasting residue, mixhairy vetch with winter cereal grains such as rye,wheat or oats.

HAIRY VETCH (Vicia villosa)

MarianneSarrantonio


Growing grain in a mixture with a legume notonly lowers the overall C:N ratio of the combinedresidue compared with that of the grain, it mayactually lower the C:N ratio of the small grainresidue as well. This internal change causes thegrain residue to break down faster, while accu-mulating the same levels of N as it did in a mono-culture (344).

Moisture-thrifty. Hairy vetch is more drought-tolerant than other vetches. It needs a bit of mois-ture to establish in fall and to resume vegetativegrowth in spring, but relatively little over winterwhen above-ground growth is minimal.

Phosphorus scavenger. Hairy vetch showedhigher plant phosphorus (P) concentrations thancrimson clover, red clover or a crimson/ryegrassmixture in aTexas trial.Soil under hairy vetch alsohad the lowest level of P remaining after growersapplied high amounts of poultry litter prior tovegetable crops (121).

Fits many systems. Hairy vetch is ideal ahead ofearly-summer planted or transplanted crops, pro-viding N and an organic mulch. Some Zone 5Midwestern farmers with access to low-costseed plant vetch after winter grain harvest in mid-summer to produce whatever N it can until itwinterkills or survives to regrow in spring.

Widely adapted. Its high N production, vigorousgrowth, tolerance of diverse soil conditions, low fer-tility need and winter hardiness make hairy vetchthe most widely used of winter annual legumes.

MANAGEMENT

Establishment & FieldworkHairy vetch can be no-tilled, drilled into a pre-pared seedbed or broadcast.Dry conditions oftenreduce germination of hairy vetch.Drill seed at 15to 20 lb./A,broadcast 25 to 30 lb./A.Select a high-er rate if you are seeding in spring, late in the fall,or into a weedy or sloped field.Irrigation will help

germination, particularly if broadcast seeded.Plant vetch 30 to 45 days before killing frost for

winter annual management; in early spring forsummer growth; or in July if you want to kill orincorporate it in fall or for a winter-killed mulch.Hairy vetch has a relatively high P and K

requirement and, like all legumes,needs sufficientsulfur and prefers a pH between 6.0 and 7.0.However, it can survive through a broad pH rangeof 5.0 to 7.5 (120).An Illinois farmer successfully no-tills hairy

vetch in late August at 22 lb./A into closelymowed stands of fescue on former ConservationReserve Program land (417). Using a herbicide tokill the fescue is cheaper than mowing, but itmust be done about a month later when the grassis actively growing for the chemical to be effec-tive. Vetch also can be no-tilled into soybean orcorn stubble (50, 80).In Minnesota, vetch can be interseeded into

sunflower or corn at last cultivation. Sunflowershould have at least 4 expanded leaves or yieldwill be reduced (221, 222).Farmers in the Northeast’s warmer areas plant

vetch by mid-September to net 100 lb. availableN/A by mid-May. Sown mid-August, an oats/hairyvetch mix can provide heavy residue (180).Rye/hairy vetch mixtures mingle and moderate

the effects of each crop.The result is a “hybrid”cover crop that takes up and holds excess soilnitrate, fixes N, stops erosion, smothers weeds inspring and on into summer if not incorporated,contributes a moderate amount of N over a longerperiod than vetch alone,and offsets the N limitingeffects of rye (81, 83, 84, 86, 377).Seed vetch/rye mixtures, at 15-25 lb. hairy

vetch with 40-70 lb. rye/A (81, 361).Overseeding (40 lb./A) at leaf-yellowing into

soybeans can work if adequate rainfall and soilmoisture are available prior to the onset of freez-ing weather. Overseeding into ripening corn (40lb./A) or seeding at layby has not worked as con-sistently. Late overseeding into vegetables is pos-sible, but remember that hairy vetch will notstand heavy traffic (361).

HAIRY VETCH 145

KillingYour mode of killing hairy vetch and managingresidue will depend on which of its benefits aremost important to you. Incorporation of hairyvetch vegetation favors first-year N contribution,but takes significant energy and labor. Keepingvetch residue on the surface favors weed sup-pression, moisture retention, and insect habitat,but may reduce N contribution.However, even inno-till systems, hairy vetch consistently providesvery large N input (replacing up to 100 lb.N/A).In spring, hairy vetch continues to add N

through its “seed set” stage after blooming.Biomass and N increase until maturity, givingeither greater benefit or a dilemma,depending onyour ability to deal with vines that become moresprawling and matted as they mature.Mulch-retaining options include strip-tilling

or strip chemical desiccation (leaving vetchuntreated between the strips), mechanical killing(rotary mowing, flailing, cutting, sub-soil shearingwith an undercutter, or chopping/flatteningwith a roller/crimper) or broadcast herbicideapplication.

No-till corn into killed vetch.The best time forno-till corn planting into hairy vetch varies withlocal rainfall patterns, soil type, desired N contri-bution, season length and vetch maturity.In southern Illinois, hairy vetch no-tilled into

fescue provided 40 to 180 lb. N/A per year over15 years for one researcher/farmer. He used her-bicide to kill the vetch about two weeks beforethe area’s traditional mid-May corn planting date.The 14-day interval was critical to rid the field ofprairie voles, present due to the field’s thick fes-cue thatch.He kills the vetch when it is in its pre-bloom or

bloom stage, nearing its peak N-accumulationcapacity. Further delay would risk loss of soilmoisture in the dry period customary there inearly June.When the no-tilled vetch was left togrow one season until seed set, it produced 6 tonsof dry matter and contributed a potentially pol-luting 385 lb.N/A (417).This high dose of N mustbe managed carefully during the next year to pre-vent leaching or surface runoff of nitrates.

A series of trials in Maryland showed a differ-ent mix of conditions. Corn planting in late-Aprilis common there, but early killing of vetch toplant corn then had the surprising effect ofdecreasing soil moisture and corn yield,as well aspredictably lowering N contribution.The earlier-planted corn had less moisture-conservingresidue. Late April or early May kill dates, withcorn no-tilled 10 days later, consistently resultedin higher corn yields than earlier kill dates (82,83,84, 85).With hairy vetch and a vetch/rye mixture,summer soil water conservation by the covercrop residue had a greater impact than springmoisture depletion by the growing cover crop indetermining corn yield (84, 85).Results in the other trials, which also included

a pure rye cover, demonstrated the managementflexibility of a legume/grain mix. Early killed ryeprotects the soil as it conserves water and N,while vetch killed late can meet a large part of theN requirement for corn. The vetch/rye mixturecan conserve N and soil moisture while fixing Nfor the subsequent crop.The vetch and vetch/ryemixture accumulated N at 130 to 180 lb./A.Themixture contained as much N or more than vetchalone (85, 86).In an Ohio trial, corn no-tilled into hairy vetch

at mid-bloom in May received better early seasonweed control from vetch mulch than corn seededinto vetch killed earlier. The late planting datedecreased yield,however (189), requiring calcula-tion to determine if lower costs for tillage, weedcontrol, and N outweigh the yield loss.Once vetch reaches about 50% bloom, it is easily

killed by any mechanical treatment.To mow-kill formulch, rye grown with hairy vetch improves cut-ting by holding the vetch off the ground to allowmore complete severing of stems from roots. Ryealso increases the density of residue covering thevetch stubble to prevent regrowth.Much quicker and more energy-efficient than

mowing is use of a modified Buffalo rolling stalkchopper, an implement designed to shatter stand-ing corn stubble. The chopper’s rolling bladesbreak over, crimp and cut crop stems at groundlevel, and handle thick residue of hairy vetch at 8to 10 mph (169).


with a 3-inch overlap on each end.The originaldesign has already been modified to include a15-foot, 6-inch model suitable for use with a 6-row planter on 30-inch rows. It can be adaptedto fit a 4-row planter on 38-inch rows, and a 5-foot version for 2-row vegetable planters.“We realize that 6-row equipment is small

by today’s standards, and work is under wayon a system that mounts one section of theroller in front of the tractor with theremainder mounted on the planter ahead ofthe row units.This design will allow as wide aroller system as a farmer needs,”Moyer says.

Chevron Pattern. The chevron pattern onthe face of the roller came about after thedesigners realized that mounting the rollerblades in a straight line would cause excessivebouncing,while just curving the blades in ascrew pattern would act like an auger andcreate a pulling effect.“If you were driving upa hill that might be fine, but we don’t needhelp pulling our tractors down the steepslopes we farm. The chevron patternneutralizes any forces that might pull thetractor in either direction,”Moyer explains. Itovercomes both the bounce of straight-lineblades and the auguring effect of corkscrewblades.“In addition,with the twisted blade design,

only a very small portion of the blade touchesthe ground at any one time as it turns, so thefull pressure of the roller is applied 1 inch at atime.This roller design works better thananything we’ve ever used,”he adds.Prior to settling on theTRI prototype,Moyer

and Brubaker studied stalk choppers with ninerolling drums arranged in two parallel rows.This design required 18 bearings and providedlots of places for green plant material to bunch

THE POSSIBILITY of using rollers to reduceherbicide use isn’t new,but advances arebeing made to improve the machines in waysthat could make them practical for controllingno-till cover crops.Cover crop rolling is gaining visibility and

credibility in tests by eight university/farmerresearch teams across the country.The testrollers were designed and contributed byTheRodale Institute (TRI), a Pennsylvania-basedorganization focused on organic agriculturalresearch and education.The control achievedwith the roller is comparable to a rollercombined with a glyphosate application,according toTRI.The Rodale crop rollers were delivered to

state and federal cooperative research teams inVirginia,Michigan,Mississippi,North Dakota,Pennsylvania,Georgia, California and Iowa inSpring, 2005. Funding for the program comesfrom grants and contributions from theNatural Resources Conservation Service andprivate donors. I&J Manufacturing in Gap, Pa.,fabricated the models distributed to theresearch teams.“The requirement is that each research

leader partners with a farmer cooperator toadapt the rollers to local conditions and covercropping systems,”explains Jeff Moyer,TRI’sfarm manager.“Our goal is to gain moreknowledge about the soil building and weedmanagement effects of cover crops whilereducing the need for herbicides,”he says.

Farmer Built. Moyer designed and builtthe first front-mountedTRI roller prototype in2002 in conjunction with Pennsylvania farmerJohn Brubaker,whose land abuts theTRIproperty.The original 10-foot, 6-inch rollerwidth is equal to 4 rows on 30-inch spacing,

Cover Crop Roller Design Holds Promise For No-TillersHowever, timing of control and planting in a single pass could limit adoption; hope lies inbreeding cover crops that flower in time for traditional planting window.

HAIRY VETCH 147

up.TheTRI ground-driven roller has a singlecylinder and two offset bearings inset 3 incheson either side and fronted with a shield.Theblades are welded onto the 16-inch-diameterdrum,but replacement blades can bepurchased from the manufacturer and boltedon as needed.The 10-foot, 6-inch roller weighs1,200 pounds empty and 2,000 pounds if filledwith water.

Front Mount Benefits. The biggestadvantage of the front-mounted roller is thatthe operator can roll the cover crop and no-tillthe cash crop in a single field pass,Moyerexplains. InTRI trials, simultaneous rolling andno-till planting eliminated seven of the eightfield passes usually necessary withconventional organic corn production,including plowing, discing, packing, planting,two rotary hoe passes and two cultivations.Rolling the field and no-tilling in one pass

also eliminates the problem of creating a thickgreen cover crop mat that makes it difficult tosee a row marker line on a second pass forplanting.Also, planting in a second pass in the

opposite direction from which the cover cropwas rolled makes getting uniform seedingdepth and spacing more difficult because theplanter tends to stand the plant material backup.“Think of it as combing the hair on yourdog backwards,”Moyer says.“Another disadvantage of rear-mounted

machines like stalk choppers is that the tractortire is the first thing touching the cover crop.If the soil is even a little spongy, the covercrop will be pushed into the tire tracks andbecause the roller is running flat, it can’tcrimp the depressed plant material. A weeklater the plants missed by the roller will beback up and growing again.”

Crop Versatility. TheTRI roller concepthas been tested in a wide range of winterannual cover crops, including cereal rye, hairy

vetch,wheat, triticale, oats, buckwheat, clover,winter peas and other species.Timing is thekey to success,Moyer emphasizes, and a lot offarmers don’t have the patience to make itwork right.“The bottom line is that winter annuals

want to die anyway, but if you time it wrong,they’re hard to kill,”he says.“If you try to roll awinter annual before it has flowered—beforeit has physiologically reproduced—the plantwill try to stand up again and complete thejob of reproduction, the most important stageof its life cycle. But, if you roll it after it hasflowered, it will dry up and die.”At least a 50 percent, and preferably a 75 to

100 percent bloom, is recommended beforerolling.Moyer hopes to see plant breedersrecognize the need to develop cover cropvarieties with blooming characteristics thatcoincide with preferred crop plantingwindows.“We really like to use hairy vetch on our

farm, for example, because it’s a great sourceof nitrogen and is a very suitable crop to plantcorn into.The roller crimps the stem of thehairy vetch every 7 inches, closing the plant’svascular system and ensuring its demise.“The problem is we would like it to flower

a couple weeks earlier to fit our growingseason. It’s hard for farmers to understandwhen it’s planting time and we’re telling themto wait a couple more weeks for their covercrop to flower,”he says.“We need to identify the characteristics we

want in cover crops and encourage plantbreeders to focus on some of those. It shouldbe a relatively easy task to get an annual cropto mature a couple weeks earlier, compared tosome of the breakthrough plant breedingwe’ve seen recently,”Moyer says.

continued on page 148


For More Information. Updates on rollerresearch,more farmer stories and plans for theTRI no-till cover crop roller can be accessed atwww.newfarm.org/depts/notill.To askquestions of The Rodale Institute, e-mail [email protected] also“Where can I find information

about the mechanical roller-crimper used inno-till production?”http://attra.ncat.org/calendar/question.php/2006/05/08/p2221.To contact the manufacturer of

commercially available cover crop rollers,visit www.croproller.com.

Editor’s Note: PURPLE BOUNTY, a new, earliervariety of hairy vetch,was released in 2006 bythe USDA-Agricultural Research Service,Beltsville,MD in collaboration with the RodaleInstitute, Pennsylvania State University andCornell University.—Ron Ross.Adapted with permission fromwww.no-tillfarmer.com

No-till vegetable transplanting. Vetch that issuppressed or killed without disturbing the soilmaintains moisture well for transplanted vegeta-bles. No-till innovator Steve Groff of LancasterCounty, Pa., uses the rolling stalk chopper to cre-ate a killed organic mulch. His favorite mix is 25

lb.hairy vetch,30 lb. ryeand 10 lb. crimsonclover/A.

No-till, delayed kill.Farmers and researchersare increasingly using aroller/crimper to killhairy vetch and othercover crops (11). JeffMoyer and others at theRodale Institute inKutztown, Pa., roll hairyvetch and other covercrops in late May or

early June (at about 50% flower). The modifiedroller is front-mounted, and corn is no-tilled onthe same pass (303). See Cover Crop RollerDesign Holds Promise For No-Tillers, p. 146.Also useful in killing hairy vetch on raised beds

for vegetables and cotton is the improved proto-type of an undercutter that leaves severed residuevirtually undisturbed on the surface (96). Theundercutter tool includes a flat roller attachment,which, by itself, usually provides only partial sup-pression unless used after flowering.

Herbicides will kill vetch in three to 30 days,depending on the material used, rate, growthstage and weather conditions.

Vetch incorporation. As a rule, to gauge theoptimum hairy vetch kill date, credit vetch withadding two to three pounds of N per acre persunny day after full spring growth begins.Usually,N contribution will be maximized by early bloom(10-25 percent) stage.Cutting hairy vetch close to the ground at full

bloom stage usually will kill it. However, waitingthis long means it will have maximum topgrowth,and the tangled mass of mature vetch canoverwhelm many smaller mowers or disks. Flailmowing before tillage helps,but that is a time andhorsepower intensive process. Sickle-bar mowersshould only be used when the vetch is well sup-ported by a cereal companion crop and the mate-rial is dry (422).

Management CautionsAbout 10 to 20 percent of vetch seed is “hard”seed that lays ungerminated in the soil for one ormore seasons. This can cause a weed problem,especially in winter grains. In wheat, a variety ofherbicides are available, depending on cropgrowth stage. After a corn crop that can utilizethe vetch-produced N, you could establish a hayor pasture crop for several years.Don’t plant hairy vetch with a winter grain if

you want to harvest grain for feed or sale.

Winter hardy

through the

warmer parts of

Zone 4, few

legumes can rival

hairy vetch’s N

contributions.

HAIRY VETCH 149

Production is difficult because vetch vines willpull down all but the strongest stalks. Grain cont-amination also is likely if the vetch goes to seedbefore grain harvest.Vetch seed is about the samesize as wheat and barley kernels, making it hardand expensive to separate during seed cleaning(361). Grain price can be markedly reduced byonly a few vetch seeds per bushel.A severe freeze with temperatures less than

5° F may kill hairy vetch if there is no snow cover,reducing or eliminating the stand and most of itsN value.If winterkill is possible in your area,plant-ing vetch with a hardy grain such as rye ensuresspring soil protection.

Pest ManagementIn legume comparison trials, hairy vetch usuallyhosts numerous small insects and soil organisms(206). Many are beneficial to crop production,(see below) but others are pests. Soybean cystnematode (Heterodera glycines) and root-knotnematode (Meliodogyne spp.) sometimesincrease under hairy vetch. If you suspect that afield has nematodes,carefully sample the soil afterhairy vetch. If the pests reach an economicthreshold, plant nematode-resistant crops andconsider using another cover crop.Other pests include cutworms (361) and south-

ern corn rootworm (67),which can be problemsin no-till corn, tarnished plant bug, noted incoastal Massachusetts (56),which readily dispers-es to other crops, and two-spotted spider mites inOregon pear orchards (142). Leaving unmowedremnant strips can lessen movement of disruptivepests while still allowing you to kill most of thecover crop (56).Prominent among beneficial predators associ-

ated with hairy vetch are lady beetles, seven-spot-ted ladybeetles (56) and bigeyed bugs (Geocarisspp.). Vetch harbors pea aphids (Acyrthosiphonpisum) and blue alfalfa aphids (Acyrthosiphonkondoi) that do not attack pecans but provide afood source for aphid-eating insects that can dis-perse into pecans (58). Similarly, hairy vetch blos-soms harbor flower thrips (Frankliniella spp.),which in turn attract important thrip predatorssuch as insidious flower bugs (Orius insidiosus)

and minute pirate bugs (Orius tristicolor).Two insects may reduce hairy vetch seed yield

in heavy infestations: the vetch weevil or vetchbruchid.Rotate crops to alleviate buildup of thesepests (361).

CROP SYSTEMS

In no-till systems, killed hairy vetch creates ashort-term but effective spring/summer mulch,especially for transplants.The mulch retains mois-ture, allowing plants to use mineralized nutrientsbetter than unmulched fields. The managementchallenge is that the mulch also lowers soil tem-perature, which may delay early season growth(361). One option is to capitalize on high quality,low-cost tomatoes that capture the late-seasonmarket premiums. See Vetch Beats Plastic(p. 150).How you kill hairy vetch

influences its ability tosuppress weeds. Durabilityand effectiveness as a light-blocking mulch are great-est where the stalks are leftwhole.Hairy vetch severedat the roots or sickle-barmowed lasts longer andblocks more light thanflailed vetch, preventing more weed seeds fromgerminating (96, 411).Southern farmers can use an overwintering

hairy vetch crop in continuous no-till cotton.Vetch mixed with rye has provided similar oreven increased yields compared with systemsthat include conventional tillage, winter fallowweed cover and up to 60 pounds of N fertilizerper acre. Typically, the cover crops are no-tilldrilled after shredding cotton stalks in lateOctober. Covers are spray killed in mid-Aprilahead of cotton planting in May.With the relative-ly late fall planting, hairy vetch delivers only part

Note:An unmowed rye/hairy vetch mix sustaineda population of aphid-eating predators that wassix times that of the unmowed volunteer weedsand 87 times that of mown grass and weeds (57).

Mix hairy vetch

with cereal

grains to

reduce the risk

of N leaching.


of its potential N in this system. It adds cost, butsupplies erosion control and long-term soilimprovement (35).Cotton yields following incorporated hairy

vetch were perennial winners for 35 years at anorthwestern Louisiana USDA site. Soil organicmatter improvement and erosion control wereadditional benefits (276).

Other OptionsSpring sowing is possible, but less desirable thanfall establishment because it yields significantlyless biomass than overwintering stands. Hotweather causes plants to languish.Hairy vetch makes only fair grazing—livestock

do not relish it.

Vetch Beats Plastic

BELTSVILLE,Md.—Killed cover crop mulchescan deliver multiple benefits for no-tillvegetable crops (1, 2, 3, 4).The system canprovide its own N, quell erosion andleaching, and displace herbicides. It’s alsomore profitable than conventionalcommercial production using black plasticmulch.A budget analysis showed it alsoshould be the first choice of “risk averse”farmers,who prefer certain although moremodest profit over higher average profit thatis less certain (224).The key to the economic certainty of a

successful hairy vetch planting is its low costcompared with the black plastic purchase,installation and removal.From refining his own research and on-farm

tests in the mid-Atlantic region for severalyears,Aref Abdul-Baki, formerly of the USDA’sBeltsville (Md.) Agricultural Research Center,outlines his approach:• Prepare beds—just as you would for plantingtomatoes—at your prime time to seed hairyvetch.

• Drill hairy vetch at 40 lb./A, and expectabout 4 inches of top growth beforedormancy,which stretches from mid-December to mid-March in Maryland.

• After two months’ spring growth, flail mowor use other mechanical means to suppressthe hairy vetch. Be ready to remow or useherbicides to clean up trouble spots wherehairy vetch regrows or weeds appear.

•Transplant seedlings using a minimum tillageplanter able to cut through the mulch andfirm soil around the plants.

The hairy vetch mulch suppresses early seasonweeds. It improves tomato health bypreventing soil splashing onto the plants, andkeeps tomatoes from soil contact, improvingquality.Hairy vetch-mulched plants may needmore water.Their growth is more vigorous andmay yield up to 20 percent more than thoseon plastic. Completing harvest by mid-September allows the field to be immediatelyreseeded to hairy vetch.Waiting for vetch tobloom in spring before killing it and the tightfall turnaround may make this system lessuseful in areas with a shorter growing seasonthan this Zone 7,mid-Atlantic site.Abdul-Baki rotates season-long cash crops of

tomatoes,peppers and cantaloupe through thesame plot between fall hairy vetch seedings.Heshallow plows the third year after cantaloupeharvest and seeds hairy vetch for flat-field crops ofsweet corn or snap beans the following summer.He suggests seeding rye (40 lb./A) with the

vetch for greater biomass and longer-lastingmulch.Adding 10-12 lb./A of crimson cloverwill aid in weed suppression and N value.Rolling the covers before planting provideslonger-lasting residue than does mowing them.Some weeds, particularly perennial or winterannual weeds, can still escape this mixture,and may require additional management (4).

HAIRY VETCH 151

Harvesting seed. Plant hairy vetch with grains ifyou intend to harvest the vetch for seed. Use amoderate seeding rate of 10-20 lb./A to keep thestand from getting too rank.Vetch seed pods willgrow above the twining vetch vines and use thegrain as a trellis,allowing you to run the cutter barhigher to reduce plugging of the combine.Directcombine at mid-bloom to minimize shattering, orswath up to a week later. Seed is viable for at leastfive years if properly stored (361).If you want to save dollars by growing your

own seed, be aware that the mature pods shattereasily, increasing the risk of volunteer weeds.Tokeep vetch with its nurse crop,harvest vetch witha winter cereal and keep seed co-mingled forplanting.Check the mix carefully for weed seeds.

COMPARATIVE NOTES

Hairy vetch is better adapted to sandy soils than crim-son clover (344), but is less heat-tolerant than LANAwoollypod vetch.SeeWoollypodVetch (p.185).

Cultivars. MADISON—developed in Nebraska—tolerates cold better than other varieties. Hairyvetches produced in Oregon and California tendto be heat tolerant.This has resulted in two appar-ent types, both usually sold as “common”or “vari-ety not stated” (VNS). One has noticeably hairy,bluish-green foliage with bluish flowers and ismore cold-tolerant.The other type has smoother,deep-green foliage and pink to violet flowers.A closely related species—LANA woollypod

vetch (Vicia dasycarpa)—was developed inOregon and is less cold tolerant than Vicia villosa.Trials in southeastern Pennsylvania with manyaccessions of hairy vetch showed big flowervetch (Vicia grandiflora, cv WOODFORD) was theonly vetch species hardier than hairy vetch.EARLYCOVER hairy vetch is about 10 days earlier thanregular common seed.PURPLE BOUNTY, released in2006, is a few days earlier and provides more bio-mass and better ground cover than EARLY COVER.



MEDICS

Medicago spp.

Also called: black medic, burr (orbur) medic, burclover

Type: Winter annual or summerannual legume

Roles: N source, soil qualitybuilder, weed suppressor, erosionfighter

Mix with: Other medics; cloversand grasses; small grains


annual medics

annual medics marginal utility

perennial medics (dryland)

Once established, few other legumes out-perform medics in soil-saving, soil-build-ing and—in some systems—forage,when

summer rainfall is less than 15 inches.They servewell in seasonally dry areas from mild Californiato the harsh Northern Plains.With more rainfall,however, they can produce almost as much bio-mass and N as clovers. Perennial medics are self-reseeding with abundant“hard seed”that can takeseveral years to germinate. This makes medicsideal for long rotations of forages and cash cropsin the Northern Plains and in cover crop mixturesin the drier areas of California.

Annual medics include 35 known speciesthat vary widely in plant habit, maturity date andcold tolerance. Most upright varieties resemblealfalfa in their seeding year with a single stalk andshort taproot.Medics can produce more than 100lb. N/A in the Midwest under favorable condi-tions, but have the potential for 200 lb. N/Awhere the plants grow over winter.They germi-nate and grow quickly when soil moisture is ade-quate, forming a thick ground cover that holdssoil in place.The more prostrate species of annu-al medic provide better ground cover.Significant annual types include: burr medic

(M. polymorpha), which grows up to 14 inches

tall, is semi-erect or prostrate, hairless, and offersgreat seed production and N-fixing ability; barrelmedic (M. truncatula), about 16 inches tall, withmany mid-season cultivars; and snail medic (M.scutellata), which is a good biomass and N pro-ducer.Southern spotted burr medic is a native M.

polymorpha cultivar with more winterhardinessthan most of the current burr medics, which areimported from Australia. See Southern BurrMedic Offers Reseeding Persistence (p. 154).Naturalized burr medic seed is traded locally inCalifornia.Annual medics broadcast in spring over wheat

stubble in Michigan reduced weed number andgrowth of spring annual weeds prior to no-tillcorn planting the following spring.Spring-plantedannual medics produced dry matter yields similarto or greater than alfalfa by July (373, 376).

Black medic (M. lupulina) is usually called aperennial. It can improve soil, reduce diseases,save moisture and boost grain protein whengrown in rotations with grains in the NorthernPlains.GEORGE is the most widely used cultivar indryland areas of the Northern Plains. Black medicproduces abundant seed.Up to 96 percent of it ishard seed,much of it so hard seeded that it won’t

MEDICS 153

germinate for two years. Second-year growth maybe modest, but coverage improves in years threeand four after the initial seeding if competition isnot excessive (422) and grazing management istimely.

BENEFITS

Good N on low moisture. In dryland areas,most legumes offer a choice between N produc-tion and excessive water use.Medics earn a placein dryland crop rotations because they provide Nwhile conserving moisture comparable to bare-ground fallow (230, 380).Fallow is the intentional resting of soil for a sea-

son so it will build up moisture and gain fertilityby biological breakdown of organic matter. Black

medic increased spring wheat yield by about 92percent compared with spring wheat followingfallow, and also appreciably raised the grain pro-tein level (379). GEORGE grows in a prostrate toascending fashion and overwinters well withsnow cover in the Northern Plains.April soil N value after black medic in one

Montana test was 117 lb./A, about 2.5 times thefallow N level and the best of six cultivars tested,all of which used less water than the fallow treat-ment (378). In North Dakota, however, unrestrict-ed medic growth depressed yield of a followingwheat crop (73).

Great N from more water. Under normal dry-land conditions, medics usually produce about 1T dry matter/A, depending on available soil mois-

STANFORD,Mon.—Jess Alger can count on13 inches of rainfall or less on his centralMontana farm, occasional hail damage, too fewsolar units to raise safflower or millet, somebone-chilling winters without snow cover—and George.That’s GEORGE black medic.On-farm tests showed he got 87 lb.N/A and

3 percent organic matter on his Judith clayloam soils.He initially seeded the medic on 10-inch row spacings with barley at 10 lb./A,hisstandard rate and seeding method.He grazedthe medic early in the second year, and then letit go to seed. InYear 3,he sprayed it withglyphosate in order to establish a sorghum-sudangrass hybrid as emergency forage on May15.He had several inches of growth when frosthit about June 10 and killed the tender grass.The medic came on strong.He let it mature

to its full 12 inches to harvest it for seed.“Itwas already laying over, but the pickup guardson my combine helped to gather in about halfthe seed.” The other half pumped up the seedbank for years ahead.He did a comparison with side-by-side fields

of spring wheat.One followed a spring wheatcrop, the other he planted into a six-year-old

stand of GEORGE medic.The medic/wheatinterplant yielded 29 bushels per acre—sixbushels less than the other field. But theinterplanted grain tested at 15 percent protein,a full percentage point higher. Those are highyields for Alger’s area, partly due to timelysummer rain.“The yield drop with medic wasmostly a weed problem with Persian darnel,”Alger explains,“but I now have that mostlyunder control.”Jess continues to fine-tune his system to

maximize income and weed management.Hebecame certified organic in 1999.He maintainsthe medic seed bank with no-till plantings ofGEORGE with a nurse crop ofAustrian winterpeas.He is experimenting successfully with ryeinstead of summer fallow.If weed pressure is high,medic fields are

grazed closely to prevent weeds from going toseed, then plowed.Otherwise, he no-tillswinter wheat into standing medic so he canleave most of the medic in place, bury lessseed and allow GEORGE to rest more securelyin his field.Updated in 2007 by Andy Clark

Jess Counts on GEORGE for N and Feed


ture and fertility. When moisture is abundant,medics can reach their full potential of 3 T/A of3.5 to 4 percent plant-tissue nitrogen, contribut-ing more than 200 lb.N/A (201, 422).

Fight weeds. Quick spring regrowth suppressesearly weeds. Fall weeds are controlled by medicregrowth after harvest, whether the medic standis overseeded or interplanted with the grain, orthe grain is seeded into an established medic

stand. In California orchards and vineyards wherewinters are rainy instead of frigid, medics mixedwith other grasses and legumes provide a contin-uous cover that crowds out weeds. In those situa-tions, medics help reduce weed seed productionfor the long-term.

Boost organic matter. Good stands of medics inwell drained soil can contribute sufficient residueto build soil organic matter levels. One Indiana

While annual medics, in general, are hardseeded, they usually cannot tolerate wintersnorth of the Gulf South. Southern spotted burrmedic (Medicago arabica) shows promise asa winter legume that can reseed for severalyears from a single seed crop in HardinessZone 7 of the Southeast.Once as widely grown as hairy vetch in the

mid-South region of the U.S., burr medicpersists in non-cropland areas because it iswell adapted to the region (326, 327). A localaccession collected in northern Mississippiexhibits better cold hardiness and insectresistance than commercially available(Australian) annual medics.In a replicated cold-hardiness trial spanning

several states, spotted burr medic flowered inmid-March, about two weeks after SERENA,CIRCLE VALLEY or SANTIAGO burclover, but twoweeks before TIBBEE crimson clover.The burrmedic flowered over a longer period thancrimson,matured seed slightly sooner thanTIBBEE but generally did not produce as muchbiomass.The big advantage of spotted burr medic

over crimson clover was its ability to reseedfor several years from a single seed crop. Instudies in several states, the native medicsuccessfully reseeded for at least two yearswhen growth was terminated two weeks afterTIBBEE bloomed.Only balansa clover (see Up-and-Coming Cover Crops, p. 191) reseeded aswell as spotted burclover (105).The burr

Southern Spotted Burr Medic Offers Reseeding Persistence

medic cultivar CIRCLE VALLEY successfullyreseeded in a Louisiana no-till cotton field formore than 10 years without specialmanagement to maintain it (103).Research in the Southeast showed that if

Southern spotted burr medic begins bloomingMarch 23, it would form viable seed by May 2,and reach maximum seed formation by May12. By allowing the cover crop to grow until40 to 50 days after first bloom and managingthe cropping system without tillage thatwould bury burclover seeds too deeply,Southern spotted burclover shouldsuccessfully reseed for several years.Native medic seed is being increased in

cooperation with the USDA-Natural ResourcesConservation Service’s JamieWhitten PlantMaterials Center, Coffeeville,Miss., for possibleaccelerated release to seed growers as a“source-identified”cover crop.Insect pests such as clover leaf weevil

(Hypera punctata Fabricius) and the alfalfaweevil (Hypera postica Gyllenhal)preferentially attack medics over other winterlegume cover crops in the Southeast, andcould jeopardize seed production.Theseinsects are easily controlled with pyrethroidinsecticides when weevils are in their secondinstar growth stage.While not usually neededfor single-season cover crop benefits, insect-icides may be warranted in the seeding year toensure a reseeding crop for years to come.

MEDICS 155

test reported a yield ofmore than 9,000 lb. drymatter/A from a spring-sown barrel medic (164).

Reduce soil erosion.Medics can survive insummer drought-proneareas where few othercultivated forage legumeswould, thanks to theirhard-seeded tendency

and drought tolerance. Low, dense vegetationbreaks raindrop impact while roots may pene-trate 5 feet deep to hold soil in place.

Tolerate regular mowing. Medics can be grazedor mowed at intervals with no ill effects. Theyshould be mowed regularly to a height of 3 to 5inches during the growing season for best seed setand weed suppression. To increase the soil seedbank,rest medic from blooming to seed maturation,then resume clipping or grazing (285,422,435).

Provide good grazing. Green plants, dry plantsand burs of burr medic provide good forage, butsolid stands can cause bloat in cattle (422). Theburs are concentrated nutrition for winter forage,but lower the value of fleece when they becomeembedded in wool. Annual medics overseededinto row crops or vegetables can be grazed in fallafter cash crop harvest (376).

Reseeding. Black medic has a high percentage ofhard seed.Up to 90 percent has an outer shell thatresists the softening by water and soil chemicalsthat triggers germination (286). Scarified seed willachieve 95 percent germination, and 10-year oldraw seed may still be 50 percent viable (422).Burrmedic seed in the intact bur remains viable for alonger time than hulled seed (120).Their status as a resilient, reseeding forage

makes medics the basis for the“ley system”devel-oped in dry areas of Australia. Medics or subter-ranean clover pastured for several years onAustralian dry-lands help to store moisture andbuild up soil productivity for a year of small grainproduction before being returned to pasture.Thisuse requires livestock for maximum economic

benefit. GEORGE black medic isprostrate, allowing other grassesand forbs to become the over-story for grazing. It is well-suited to cold winterareas of HardinessZone 4, where it canstay green much ofthe winter (6).

Quick starting.Blackmedic can germinatewithin three days ofplanting (286). About45 days after mid-April planting in south-ern Illinois, two annualmedics were 20 inch-es tall and blooming.In the upper Mid-west, snail and burrmedics achieve peakbiomass about 60days after planting. An earlyAugust seeding of theannuals in southern Illinois germinated well,stopped growing during a hot spell, then restart-ed. Growth was similar to the spring-plantedplots by September 29 when frost hit.The plantsstayed green until the temperature dipped to theupper teens (201).

Widely acclimated. Species and cultivars varyby up to seven weeks in their estimated length oftime to flowering.Be sure to select a species to fityour weather and crop rotation.

MANAGEMENT

EstablishmentAnnual medics offer great potential as a substitutefor fallow in dry northern regions of the U.S.withlonger day length. Annual medics need to fix asmuch N as winter peas or lentils and have a com-petitive establishment cost per acre to be as valu-able as these better-known legume greenmanures (383).Medics are widely adapted to soils that are rea-

sonably fertile, but not distinctly acid or alkaline.Excessive field moisture early in the season can

Hard-seeded

medics are ideal

for reseeding

systems in

orchards and

vineyards.

BLACK MEDIC(Medicago lupulina)

ElayneSears


significantly reduce medic stands (373). Acid-tol-erant rhizobial strains may help some cool-seasonmedics, especially barrel medic, to grow on sitesthat otherwise would be inhospitable (422).To reduce economic risk in fields where you’ve

never grown medic, sow a mixture of medicswith variable seed size and maturation dates. Indry areas of California, medic monocultures areplanted at a rate of 2 to 6 lb./A,while the rate withgrasses or clovers is 6 to 12 lb./A (422).Establishment options vary depending on cli-

mate and crop system:• Early spring—clear seed. Drill 1/4 to 1/2

inch deep (using a double-disk or hoe-type drill)into a firm seed bed asyou would for alfalfa.Rolling is recommend-ed before or after seed-ing to improve seed-soilcontact and moisture inthe seed zone. Seedingrate is 8 to 10 lb./A forblack medic, 12 to 20lb./A for larger-seeded(snail, gamma and burr)annual medics. In the

arid Northern Plains, fall germination and wintersurvival are dependable, although spring plantingalso has worked.• Spring grain nurse crop. Barley, oats,

spring wheat and flax can serve as nurse crops formedic, greatly reducing weed pressure in theseeding year. The drawback is that nurse cropswill reduce first-year seed production if you aretrying to establish a black medic seed bank. Toincrease the soil seed reserve for a long-termblack medic stand (germinating from hard seed),allow the medic to blossom, mature and reseedduring its second year.• Corn overseed. SANTIAGO burr medic and

SAVA snail medic were successfully established inno-till corn three to six weeks after corn plantingduring a two-year trial in Michigan.Corn yield wasreduced if medics were seeded up to 14 days aftercorn planting.Waiting 28 days did not affect cornyield,but medic biomass production was reducedby 50% (219).

Where medic and corn work together, such asCalifornia, maximize medic survival during thecorn canopy period by seeding early (when cornis eight to 16 inches tall) and heavy (15 to 20lb./A) to build up medic root reserves (47, 422).• After wheat harvest. MOGUL barrel medic

seeded after wheat harvest produced 119 lb.N/Ain southern Michigan, more than double the Nproduction of red clover seeded at the same time(373). In Montana, mid-season establishment ofsnail medic after wheat works only in years withadequate precipitation, when it smothers weeds,builds up N, then winterkills for a soil-holdingorganic mulch (72).• Autumn seeding.Where winters are rainy in

California, medics are planted in October as win-ter annuals (436). Plant about the same time ascrimson clover in the Southeast, Zones 7 and 8.

KillingMedics are easy to control by light tillage or her-bicides. They reseed up to three times per sum-mer, dying back naturally each time.Medics in thevegetative stage do not tolerate field traffic.

Field ManagementBlack medic>small grain rotations developed inMontana count on successful self-reseeding ofmedic stands for grazing by sheep or cattle. Amonth of summer grazing improves the econom-ics of rotation by supplying forage for about oneanimal unit per acre. In this system, establishedself-reseeding black medic plowed down as greenmanure in alternate years improved spring wheatyield by about 50 percent compared to fallow(380).Black medic is a dual-use legume in this adapt-

ed“ley”system.Livestock graze the legume in the“medic years” when the cover crop accumulatesbiomass and contributes N to the soil.Cash cropscan be no-tilled into killed medic, or the legumecan be incorporated.A well-established black medic stand can

reduce costs compared with annual crops bycoming back for many years. However, withoutthe livestock grazing benefit to supply additionalutilization, water-efficient legumes such as lentils

Medics earn a

place in dryland

rotations because

they provide N

while conserving

moisture.

MEDICS 157

and Austrian winter peas will probably be moreeffective N sources. Further, the long-lived seedbank that black medic establishes may be unde-sirable for some cash crop rotations (383).Use of medics for grain production in the

upper Midwest has given inconsistent results.Berseem clover may be a better choice in manysituations. In a series of trials in Ohio, Michigan,Wisconsin and Minnesota, medic sometimesreduced corn yield and did not provide enoughweed control or N to justify its use under currentcash grain prices, even when premiums for pesti-cide-free corn were evaluated (141, 219, 373, 374,376, 456, 457).One Michigan farmer’s situation isfairly typical. He established annual medic at 10lb./A when his ridge-tilled corn was about knee-high. The legume germinated, but didn’t growwell or provide weed suppression until aftercorn dry-down in mid-September. The medic puton about 10 inches of growth before win-terkilling, enough for effective winter erosionprotection (201).Black medic and two annual medics produced

50 to 150 lb. N/A when interplanted with stan-dard and semi-dwarf barley in a Minnesota trial.Annual MOGUL produced the most biomass byfall, but also reduced barley yields. GEORGE wasthe least competitive and fixed 55 to 120 lb.N/A.The taller barley was more competitive,indicatingthat taller small grain cultivars should be used tofavor grain production over medic stand develop-ment (289).Midwestern farmers can overseed annual

medic or a medic/grass mixture into wheat invery early spring for excellent early summer graz-ing. With timely moisture, you can get a hay cut-ting within nine to 10 weeks after germination,and some species will keep working to produce asecond cutting. Regrowth comes from lateralstems, so don’t clip or graze lower than 4 or 5inches if you want regrowth.To avoid bloat,man-age as you would alfalfa (201).Annual medics can achieve their full potential

when planted after a short-season springcrop such as processing peas or lettuce.Wisconsin tests at six locations showed medicproduced an average of 2.2T/A when sown in thelate June or early July (399). Early planting in this

window with a late frost could give both forageand N-bearing residue, protecting soil and addingspring fertility. Take steps to reduce weed pres-sure in solid seedings, especially in early July.In another Michigan comparison,winter canola

(Brassica napus) yields were similar after a greenmanure comparison of two medics, berseemclover and NITRO annualalfalfa. All the covers wereclear (sole-crop) seeded inearly May after pre-plantincorporated herbicidetreatment, and wereplowed down 90 days later.Harvesting the medics at 60days as forage did notsignificantly lessen theirgreen manure value (373).In the mid-Atlantic at the

USDA Beltsville, Md. site, medics have been diffi-cult to establish by over-seeding at vegetableplanting or at final cultivation of sweet corn.

Pest ManagementUnder water logged conditions for which they areill-suited, annual medics are susceptible to diseaseslike Rhizoctonia, Phytophthora and Fusarium.

Burr medic harbors abundant lygus bugs inspring. It also appears to be particularly prone tooutbreaks of the two-spotted spider mite, a pestfound in manyWest Coast orchards (422).Pods and viable seeds develop without pollina-

tors because most annual medics have no floralnectaries (120).

COMPARATIVE NOTES

Snail medic produced about the same biomassand N as red clover when both legumes werespring sown with an oats nurse crop into a diskedseedbed in Wisconsin. Yields averaged over onewet year and one dry year were about 1T dry mat-ter and 60 lb.N/A (141).Medics can establish and survive better than

subterranean clover in times of low rainfall, andare more competitive with grasses. A short peri-od of moisture will allow medic to germinate andsend down its fast-growing taproot, while sub-

With abundant

moisture,

medics can

produce more

than 200 lb.

N/A.


clover needs more consistent moisture for its shal-lower, slower growing roots (422). Medics aremore susceptible than subclover to seed produc-tion loss from closely mowing densely plantederect stalks. Burr and barrel medics are not aseffective as subclover at absorbing phosphorus(422).Medics may survive where true clovers

(Trifolium spp.) fail due to droughty conditions(422) if there is at least 12 in. of rain per year(292).

Medics grow well inmixtures with grasses andclovers, but don’t per-form well with red clover(422, 263). Once estab-lished, black medic han-dles frost better thancrimson or red clover.GEORGE grows more

slowly than yellow blossom sweetclover in springof the second year,but it starts flowering earlier. Ituses less water in the 2- to 4-foot depth thansweetclover, soybeans or hairy vetch seeded atthe same time.

Annual Medic Cultivars. Species and cultivarsof annual medic vary significantly in their dry mat-ter production, crude protein concentration andtotal N. Check with local or regional forage spe-cialists for cultivar recommendations

Burr medic (also called burclover) cultivarsare the best known of the annual medics. Theybranch profusely at the base, and send out pros-trate stems that grow more erect in dense stands(422). They grow quickly in response to fallCalifornia rains and fix from 55 to 90 lb. N/A,near-ly as much as true clovers (294, 422).Most standsare volunteer and can be encouraged by propergrazing, cultivation or fertilization.Selected cultivars include SERENA (an early

bloomer), and CIRCLE VALLEY, both of which havefair tolerance to Egyptian alfalfa weevil (435).SANTIAGO blooms later than SERENA. Early burrmedics flower in about 62 days in California,rang-ing up to 96 days for mid-season cultivars (422).Naturalized and imported burr medic proved

the best type of burclover for self-reseeding cover

crops in several years of trials run from northernCalifornia into Mexico in the 1990s.While someof the naturalized strains have been self-reseedingfor 30 years in some orchards, Extension special-ists say the commercial cultivars may be prefer-able because they are widely available and betterdocumented.Established burr medic tolerates shade as a

common volunteer in the understories ofCalifornia walnut orchards, which are heavilyshaded from April through November. However,in Michigan trials over several years, SANTIAGO (aburr medic with no spines on its burs) failed toestablish satisfactorily when it was overseededinto corn and soybeans at layby. Researchers sus-pect the crop canopy shaded the medic too soonafter planting, and that earlier overseeding mayhave allowed the medic to establish.There are at least 10 cultivars of barrel medic.

Dates of first flowering for barrel medics rangefrom 80 to 105 days after germination, and seedcount per pound ranges from 110,000 forHANAFORD to 260,000 for SEPHI (422). A leadingnew cultivar, SEPHI, flowers about a week earlierthan JEMALONG,commonly used in California (251,422).SEPHI, a mid-season cultivar, has a more erecthabit for better winter production, is adapted tohigh- and low-rainfall areas, yields more seed andbiomass than others, has good tolerance toEgyptian alfalfa weevil and high tolerance to spot-ted alfalfa aphid and blue green aphid. It is sus-ceptible to pea aphid.

Snail medic (M. scutellata) is a prolific seedproducer. Quick germination and maturity canlead to three crops (two reseedings) in a singleseason from a spring planting in the Midwest(373). MOGUL barrel medic grew the most bio-mass in a barley intercrop, compared withSANTIAGO burr medic and GEORGE black medic ina four-site Minnesota trial. It frequently reducedbarley yields, particularly those of a semi-dwarfbarley variety, but increased weed suppressionand N and biomass production (289).In a Michigan test of forage legumes for emer-

gency forage use,MOGUL barrel medic produced1.5 T dry matter/A compared to about 1 T/A forSAVA snail medic and SANTIAGO burr medic (M.polymorpha). Nitrogen production was 66 lb./A

Medics are easy

to kill with light

tillage or most

herbicides.

RED CLOVER 159

for MOGUL, 46 for SAVA and 22 for SANTIAGO.Theseeding rate for SAVA medic is 29 lb./A,more thantwice the 13 lb./A recommended for clear seed-ings of MOGUL and SANTIAGO (373, 376).In a California pasture comparison of three

annual medics, JEMALONG barrel had the highestlevel of seed reserves in the soil after six years,butdidn’t continue into the seventh year after the ini-

tial seeding. GAMMA medic (M. rugosa) had thehighest first-year seed production but re-estab-lished poorly, apparently due to a low hard seedcontent. All the medics re-established betterunder permanent pasture than under any rota-tional system involving tillage (94, 422).


Red clover is a dependable, low-cost, readilyavailable workhorse that is winter hardy inmuch of the U.S. (Hardiness Zone 4 and

warmer). Easily overseeded or frostseeded intostanding crops, it creates loamy topsoil, adds amoderate amount of N, helps to suppress weedsand breaks up heavy soil. Its most common usesinclude forage,grazing,seed harvest,plowdown Nand, in warmer areas, hay. It’s a great legume tofrostseed or interseed with small grains whereyou can harvest grain as well as provide weedsuppression and manage N.

BENEFITS

Crop fertility.As a cover crop, red clover is usedprimarily as a legume green manure killed aheadof corn or vegetable crops planted in early sum-mer. Full-season, over-wintered red clover canproduce 2 to 4 T dry matter/A and fix 70 to 150lb. N/A. In Ohio, over-wintered mammoth andmedium red clover contained about 75 lb.N/A byMay 15, increasing to 130 lb.N by June 22 (366).Two years of testing inWisconsin showed that

conventionally planted corn following red clover

RED CLOVERTrifolium pratense

Also called: medium red clover(multi-cut, early blooming, Juneclover); mammoth clover (singlecut,late blooming, Michigan red)

Type: short-lived perennial, biennialor winter annual legume

Roles: N source, soil builder, weedsuppressor, insectary crop, forage

Mix with: small grains, sweetclover,corn, soybeans, vegetables, grassforages

See charts, p. 66 to 72, for rankingsand management summary.

spring seeded biennial

winter annual


yielded the same as corn supplied with 160 lb.N/A, with less risk of post-harvest N leaching.Corn and the soil testing showed that 50 percentof the cover crop N was released in the firstmonth after incorporation, corresponding wellwith corn’s fertility demand. Post-harvest soil Nlevels in the clover plots were the same or lessthan the fertilized plots, and about the same asunfertilized plots (401).

Widely adapted.While many other legumes cangrow quicker, produce more biomass and fixmore nitrogen, few are adapted to as many soiltypes and temperate climatic niches as red clover.As a rule, red clover grows well wherever corn

grows well. It doesbest in cool condi-tions.In southern Canada

and the northern U.S.,and in the higher ele-vations of the South-east and West, redclover grows as a bien-

nial or short-lived perennial.At lower elevations inthe Southeast, it grows as a winter annual, and atlower elevations in theWest and Canada, it growsunder irrigation as a biennial (120). It grows inany loam or clay soil, responding best to well-drained, fertile soils, but also tolerates less well-drained conditions.

Many economic uses. Red clover has been apopular,multi-use crop since European immigrantfarmers brought it to NorthAmerica in the 1500s.It remains an important crop thanks to its greateradaptability, lower seeding cost and easier estab-lishment than alfalfa. It can produce up to 8,000lb. biomass/A.A red clover/small grain mix has been a tradi-

tional pairing that continues to be profitable. Arotation of corn and oats companion-seeded withred clover proved as profitable as continuouscorn receiving 160 lb. N/A in a four-yearWisconsin study (400). For more information, seethe Wisconsin Integrated Cropping Systems Trial(449) and the final report of this project, partiallyfunded by SARE (328).

Red clover was the most profitable of fivelegumes under both seeding methods in thetrial—sequentially planted after oats harvest orcompanion planted with oats in early spring.Thecompanion seedings yielded nearly twice asmuch estimated fertilizer replacement value asthe sequential seedings. The work showed thatred clover holds great potential to reduce fertiliz-er N use for corn grown in rotation (401).In Michigan, red clover frost-seeded into winter

wheat suppressed common ragweed growththrough wheat harvest and into the summer.Thered clover did not provide complete ragweedcontrol,but there was no adverse effect on wheatyield (297).Red clover sown as a companion with spring

oats outperformed the other legumes, which suf-fered from insect damage, mechanical damageduring oat harvest and slow subsequentregrowth.The short season proved inadequate forsequentially seeded legumes with the exceptionof hairy vetch, which was nearly as profitable asthe red clover (400).The role of red clover’s N contribution in the

rotation grew more significant as N pricesincreased in the late 1990s (and 2007!), eventhough clover seed price also increased from theoriginal 1989 calculations (398).

Soil conditioner. Red clover is an excellent soilconditioner, with an extensive root system thatpermeates the topsoil. Its taproot may penetrateseveral feet.

Attracts beneficial insects. Red clover earned aco-starring role with LOUISIANA S-1 white cloverin pecan orchard recommendations fromOklahoma State University. Red clover attractsmore beneficials than white clover, which fea-tures higher N fixation and greater flood toler-ance than red clover (261).

Two TypesTwo distinct types of red clover have evolvedfrom the same species. Be sure you plant a multi-cut cultivar if you plan to make more than onegreen manure cutting, or to maintain the stand toprepare for a late-summer vegetable planting.

Red clover can

yield 2 to 3 tons of

dry matter and 70

to 150 lb. N/A

RED CLOVER 161

Medium red clover. Medium red (some call itmulti-cut) grows back quickly, and can be cutonce late in the seeding year and twice the fol-lowing year. For optimum N benefit and flexiblecropping options from the planting (allowing it tooverwinter as a soil-protecting mulch), you canuse it for hay, grazing or seed throughout the sec-ond season. Seed may be up to 25 percent moreexpensive than single-cut. See Chart 3B:Planting(p. 70).

Mammoth red clover produces significantbiomass and as much N as medium red in a singlefirst cutting, but does not produce as much totalbiomass and N as medium red’s multiple cuttingsover time.Use this “single-cut” red clover where afield will be all-clover just during the seeding year.Slow-growing mammoth doesn’t bloom the estab-lishment year and regrows quite slowly after cut-ting, but can provide good biomass by the end ofeven one growing season.A single cutting of mammoth will give slightly

more biomass—at a slightly lower cost—than asingle cutting of medium red.Where multiple cut-tings or groundcover are needed in the secondseason, medium red clover’s higher seed cost iseasily justified (197).Some types of mammoth do better overseeded

into wheat than into oats. ALTASWEDE (Canadian)mammoth is not as shade tolerant as MICHIGANmammoth, but works well when seeded withoats. MICHIGAN mammoth shows the best vigorwhen frostseeded into wheat, but is not as pro-ductive as medium red (229).

MANAGEMENT

Establishment & FieldworkIn spring in cool climates, red clover germinatesin about seven days—quicker than manylegumes—but seedlings develop slowly, similar towinter annual legumes.Traditionally it is drilled at10 to 12 lb./A with spring-sown grains, usingauxiliary or “grass seed” drill boxes. Wisconsinresearchers who have worked for several years tooptimize returns from red clover/oats interseed-ings say planting oats at 3 to 4 bu./A gives goodstands of clover without sacrificing grain yield(398).

Red clover’s tolerance of shade and its ability togerminate down to 41° F give it a remarkablerange of establishment niches.It can be overseeded at 10 to 12 lb./A into:• Dormant winter grains before ground

thaws. This “frostseeding”method relies on move-ment of the freeze-thaw cycle to work seed into suf-ficient seed-soil contact for germination.If the soil islevel and firm, you can broadcast seed over snowcover on level terrain.You can seed the clover withurea if fertilizer application is uniform (229). Usejust enough N fertilizer to support proven small-grain yields, because excess N application will hin-der clover establishment. To reduce small graincompetition with clover in early spring, graze orclip the small grain in early spring just before thestems begin to grow (120).Hoof impact from graz-ing also helps ensure seed-to-soil contact.• Summer annuals such as oats, barley, spelt

or spring wheat before grain emergence.• Corn at layby. Wait until corn is 10 to 12

inches tall, and at least 6 weeks (check labels!)after application of pre-emergent herbicides suchas atrazine. Clover sown earlier in favorable cool-er conditions with more light may compete toomuch for water. Later, the clover will grow moreslowly and not add substantial biomass until aftercorn harvest lets light enter (197). Dairy produc-ers often broadcast red clover after corn silageharvest.• After wheat harvest. Red clover logged a

fertilizer replacement value of 36 lb.N/A in a two-year Michigan trial that used N isotopes to tracknitrogen fixation. Red clover and three otherlegumes were no-till drilled into wheat stubble inAugust, then chemically killed by mid-May justahead of no-till corn. Clover even in this shortniche shows good potential to suppress weedsand reduce N fertilizer application (140).• Soybeans at leaf-yellowing. Sowing the

clover seed with annual or perennial ryegrass as anurse crop keeps the soil from drying out untilthe clover becomes established (197).

Whenever possible, lightly incorporate cloverseed with a harrow.Wait at least six weeks (checklabels!) to establish a red clover stand in soil treat-ed with pre-emergent herbicides such as atrazine.


KillingFor peak N contribution, kill red clover at aboutmid-bloom in spring of its second season. If youcan’t wait that long, kill it earlier to plant fieldcorn or early vegetables. If you want to harvestthe first cutting for hay,compost or mulch,kill theregrowth in late summer as green manure for fallvegetables (197). If avoiding escapes or cloverregrowth is most important, terminate as soon assoil conditions allow.Actively growing red clover can be difficult to

kill mechanically, but light fall chisel plowing fol-lowed by a second such treatment has workedwell in sandy loam Michigan soils.To kill clover mechanically in spring, you can

till,chop or mow it any time after blooming starts.You can also shallow plow, or use a moldboardplow.Chop (using a rolling stalk chopper), flail orsicklebar mow about seven to 10 days ahead ofno-till planting, or use herbicides. RoundupReady® soybeans can be drilled into living redclover and sprayed later.A summer mowing can make it easier to kill red

clover with herbicides in fall. Michigan recom-mendations call for mowing (from mid-August innorthern Michigan to early September in south-ern Michigan), then allowing regrowth for fourweeks before spraying.The daytime high air tem-

perature should be above 60° F (so that the plantsare actively growing). When soil temperaturedrops below 50° F,biological decomposition slowsto the point that mineralization of N from theclover roots and top-growth nearly stops (229).

Field EvaluationIn Michigan, about half of the total N fixed by alegume will mineralize during the followinggrowing season and be available to that season’scrop (229). However,Wisconsin research showsrelease may be faster.There, red clover and hairyvetch released 70 to 75 percent of their N in thefirst season (401).

RotationsRotation niches for red clover are usually betweentwo non-leguminous crops.Spring seedingwith oatsor frostseeding into wheat or barley are commonoptions (34).The intersowing allows economic useof the land while the clover is developing. Thisgrain/red clover combination often follows corn,butalso can follow rice,sugar beets,tobacco or potatoesin two-year rotations.For three-year rotations includ-ing two full years of red clover, the clover can beincorporated or surface-applied (clipped and left onthe field) for green manure, cut for mulch or har-vested for hay (120).Red clover in a corn>soybean>wheat/red

clover rotation in a reduced-input system out-per-formed continuous corn in a four-yearWisconsinstudy. The legume cover crop system used nocommercial fertilizer, no insecticides and herbi-cides on only two occasions—once to-spot sprayCanada thistles and once as a rescue treatment forsoybeans. Rotary hoeing and cultivating providedweed control.Gross margins were $169 for the corn>soy-

beans>wheat/red clover and $126 for continuouscorn using standard agricultural fertilizers, insecti-cides and herbicides.Top profit in the study wentto a corn>soybean rotation with a gross margin of$186, using standard inputs (272, 398, 167).Ohio farmer Rich Bennett frostseeds redclover

(10-12 lb./A) into wheat in February. He gets adecent stand of clover that keeps weeds down insummer after wheat harvest.The clover overwin-

RED CLOVER (Trifolium pratense)

MarianneSarrantonio

RED CLOVER 163

ters and continues to grow in spring. He waits aslong as possible, and then kills the clover with adisc and roll (two passes) in late April and plantscorn.He doesn’t add any fertilizer N and the cornaverages 165 bu/A on his Ottokee fine sandy soil.If summer annual grasses are a problem, red

clover is not your best option because it allowsthe grasses to set seed, even under a mowingregime.

Pest ManagementIf poor establishment or winterkill leads to weedgrowth that can’t be suppressed with clipping orgrazing, evaluate whether the anticipated covercrop benefits warrant weed control. Take care tocompletely kill the cover crop when planting drybeans or soybeans after clover. Unless you areusing herbicide-tolerant crops, you have limitedherbicide options to control clover escapes thatsurvive in the bean crop (229).Root rots and foliar diseases typically kill com-

monmedium red clover in its second year,makingit function more like a biennial than a perennial.Disease-resistant cultivars that persist three tofour years cost 20 to 40 cents more per poundand are unnecessary for most green manure appli-cations. When fertilizer N cost is high, however,remember that second-year production for someimproved varieties is up to 50 percent greaterthan for common varieties.Bud blight can be transmitted to soybeans by

volunteer clover plants.

Other Management OptionsMow or allow grazing of red clover four to sixweeks before frost in its establishment year toprepare it for overwintering. Remove clippingsfor green manure or forage to prevent plant dis-ease. Red clover reaches its prime feeding value atfive to 15 days after first bloom.Under ideal conditions,medium red clover can

be cut four times,mammoth only once.Maximumcutting of medium one year will come at theexpense of second-year yield and stand longevity.Red clover and red clover/grass mixtures makegood silage if wilted slightly before ensiling or ifother preservative techniques are used (120).

If an emergency for-age cut is needed, har-vest red clover in earlysummer, then broad-cast and lightly incor-porate millet seed witha tine harrow or disk.Millet is a heat-lovinggrass used as a coverand forage in warm-soilareas of Zone 6 andwarmer.

COMPARATIVE NOTES

Medium red clover has similar upper-limit pH tol-erance as other clovers at about 7.2. It is general-ly listed as tolerating a minimum pH of 6.0—notquite as low as mammoth, white or alsike(Trifolium hybridum) clovers at 5.5—but it issaid to do well in Florida at the lower pH. Redclover and sweetclover both perform best onwell-drained soils, but will tolerate poorly drainedsoils. Alsike thrives in wet soils.Red clover has less tendency to leach phos-

phorus (P) in fall than some non-legume covers. Itreleased only one-third to one-fifth the P of annu-al ryegrass and oilseed radish, which is a winter-annual brassica cover crop that scavenges largeamounts of N. Figuring the radish release rates—even balanced somewhat by the erosion suppres-sion of the covers—researchers determined thatP runoff potential from a quick-leaching covercrop can be as great as for unincorporatedmanure (274).For early fall plowdown,alsike clover may be a

cheaper N source than mammoth, assuming simi-lar N yields.Red clover and alfalfa showed multi-year bene-

fits to succeeding corn crops, justifying a credit of90 lb. N/A the first year for red clover (197) and50 lb. N/A the second year.The third legume inthe trial, birdsfoot trefoil (Lotus corniculatus),was the only one of the three that had enoughthird-year N contribution to warrant a credit of 25lb.N/A (148).

Few legumes are

as widely adapted

as red clover,

which can be used

as green manure,

forage or seed

crop.

Subterranean clovers offer a range of low-growing, self-reseeding legumes with highN contribution, excellent weed suppres-

sion and strong persistence in orchards and pas-tures. Fall-planted subclovers thrive inMediterranean conditions of mild,moist wintersand dry summers on soils of low to moderate fer-tility, and from moderately acidic to slightlyalkaline pH.Subclover mixtures are used on thousands of

acres of California almond orchards. It holdspromise in the coastal mid-Atlantic and Southeast

(Hardiness Zone 7 and warmer) as a killed or liv-ing mulch for summer or fall crops.Most cultivars require at least 12 inches of

growing-season rainfall per year. A summer dryperiod limits vegetative growth, but increaseshard seed tendency that leads to self-reseeding forfall reestablishment (131).Subclovers generally grow close to the ground,

piling up their biomass in a compact layer. AMississippi test showed that subclover stolons wereabout 6, 10 and 17 inches long when the canopywas 5,7 and 9 inches tall, respectively (105).

SUBTERRANEAN CLOVERSTrifolium subterraneum,T. yanninicum,T. brachycalcycinum

Also called: Subclover

Type: reseeding cool season annuallegume

Roles: weed and erosion suppres-sor, N source, living or dyingmulch, continuous orchard floorcover, forage

Mix with: other clovers and sub-clovers


cool season annual spring seeded

reseeding cool season annual fall seeded


Cultivars. KENLAND, KENSTAR, ARLINGTON, andMARATHON are improved varieties of medium redclover with specific resistance to anthracnose andmosaic virus strains. They can persist three oreven four years with ideal winter snow cover

(90).CHEROKEE has performed well in Iowa (384),is suited to the Coastal Plain and lower South,andhas superior resistance to rootknot nematode.


SUBTERRANEAN CLOVERS 165

Diversity of Types, CultivarsSelect among the many subclover cultivars that fityour climate and your cover crop goals. Identifyyour need for biomass (for mulch or greenmanure), time of natural dying to fit your spring-planting schedule and prominence of seed set fora persistent stand.Subclovers comprise three Trifolium species:

• T. subterraneum.The most common cultivarsthat thrive in acid to neutral soils (pH=5.5-7.5)and a Mediterranean climate

• T. yanninicum. Cultivars best adapted towater-logged soils

• T. brachycalcycinum. Cultivars adapted toalkaline soils and milder winters

Primary differences between these species aretheir moisture requirements, seed production anddays to maturity (21).Other variables include:• Overall dry matter yield• Dry matter yield at low moisture or low fertility• Season of best growth (fall,winter or spring)• Hard-seeding tendency• Grazing tolerance

Subclover cultivars often are described by theirdays to maturity. Seed production is dependenton maturity and weather.The wetter it is duringseed set, the lower the percentage of hard seed –important for reseeding systems (131).• Short season subclovers tend to set seed

quickly. They need only 8 to 10 inches of grow-ing-season rainfall and set seed about 85 days afterplanting. Early subclovers tend to be less winterhardy (103).• Intermediate types thrive with 14 to 20 inch-

es of rain and set mature seed in about 100 days.• Long-season cultivars perform best with

18 to 26 inches of rainfall, setting seed in about130 days.

BENEFITS

Weed suppressor. Subclover can produce 3,000to 8,500 lb. dry matter/A in a thick mat of stems,petioles (structures connecting leaves to stems)and leaves. Denser and less viny than hairy vetch,it also persists longer as a weed-controlling mulch.

Subclover mixtures helpWest Coast orchardistsachieve season-long weed management. InCoastal California, fast-growing TRIKKALA, a midsea-son cultivar with a moderate moisture require-ment, jumps out first to suppress weeds andproduces about twice as much winter growth dur-ing January and February as the other subclovers.Itdies back naturally as KOALA, (tall) and KARRIDALE(short) come on strong in March and April. Thethree cultivars complement each other spatiallyand temporally for high solar efficiency, similar tothe interplanting of peas, purple vetch, bell beansand oats in California vegetable fields where a high-residue,high-N cover is desired.In legume test plots

along the Maryland shore,subclover mulch controlledweeds better than con-ventional herbicide treat-ments. The only weed topenetrate the subcloverwas a fall infestation of yel-low nutsedge. The covercrop regrew in fall fromhard seed in the second andthird years of the experi-ment (31).

Green manure. In east Texas trials, subcloverdelivered 100 to 200 lb. N/A after spring plow-down. Grain sorghum planted into incorporatedsubclover or berseem clover with no additional Nyielded about the same as sorghum planted intodisked and fertilized soil without a cover crop inthree out of four years. The fertilized fields hadreceived 54 lb.N/A (243).

Versatile mulch. Subclover provides two oppor-tunities for use as a mulch in vegetable systems.Inspring, you can no-till early planted crops aftersubclover has been mechanically or chemicallykilled, or plant later, after subclover has set seedand dried down naturally (31). In fall, you canmanage new growth from self reseeding to pro-vide a green living mulch for cold-weather cropssuch as broccoli and cauliflower.Conventionally tilled corn without a cover crop

in a New Jersey test leached up to 150 lb. N/A

Subclovers

thrive in

Mediterranean

climates of

mild, moist

winters and

dry summers.


over winter while living subclover prevented Nloss (128). Mowing was effective in controlling aliving mulch of subclover in a two-year Californiatrial with late-spring, direct-seeded sweet cornand lettuce.This held true where subclover standswere dense and weed pressure was low. Plantinginto the subclover mulch was difficult, but wasdone without no-till equipment (239).

Soil loosener. In an Australian study in com-paction-prone sandy loam soil, lettuce yield dou-bled following a crop of subclover. Without theclover, lettuce yields were reduced 60 percent onthe compacted soil.Soil improvement was creditedto macropores left by decomposing clover rootsand earthworms feeding on dead mulch (395).

Great grazing. Subclovers are highly palatableand relished by all livestock (120). Seeded withperennial ryegrass, tall fescue or orchardgrass,subclovers add feed value as they improveproductivity of the grasses by fixing nitrogen. InCalifornia, subclover is used in pasture mixtureson non-irrigated hills. Perennial ryegrass is pre-ferred for pasture through early summer,especial-ly for sheep (309).

Insect pest protection. In the Netherlands,subclover and white clover in cabbage sup-pressed pest insect egg laying and larval popula-tions enough to improve cabbage quality and

profit compared with monocropped controlplots. Eliminating pesticide costs offset thereduced weight of the cabbages in the under-sown plots. Primary pests were Mamestra bras-sicae, Brevicoryne brassicae and Deliabrassicae. Undersowing leeks with subclover inthe Netherlands greatly reduced thrips that can-not be controlled by labeled insecticides, andslightly reduced leek rust, a disease that is diffi-cult to control.While leek quality improved, thequantity of leeks produced was reduced consid-erably (415).When tarnished plant bug (Lygus lineolaris) is

a potential pest, subclover may be the legumecover crop of choice, based on a Georgia com-parison among subclovers, hybrid vetches andcrimson clover. MT. BARKER had particularly lowlevels, and nine other subclover cultivars hadlower levels than the crimson (56).

Home for beneficial insects. In tests of eightcover crops or mixtures intercropped with canta-lope in Georgia, MT. BARKER subclover had thehighest population of big-eyed bugs (Geocoruspunctipes), a pest predator. Subclover had signifi-cantly higher numbers of egg masses of the preda-tor than rye, crimson clover and a polyculture ofsix other cover crops, but not significantly higherthan for VANTAGE vetch or weedy fallow.While thecovers made a significant difference in the preda-tor level, they did not make a significant differ-ence in control of the target pest, fall armyworm(Spodoptera frugiperda) (56).

Erosion fighter. Subclover’s soil-hugging, dense,matted canopy is excellent for holding soil.

Disease-free. No major diseases restrict sub-clover acreage in the U.S. (21).

MANAGEMENT

EstablishmentSubclovers grow best when they are planted inlate summer or early autumn and grow until earlywinter. They go dormant over winter and resume

SUBTERRANEAN CLOVER (Trifolium subterraneum)

ElayneSears


growth in early spring. In late spring, plantsflower and seeds mature in a bur at or below thesoil surface (hence the name subterranean clover)as the plant dries up and dies.A dense mulch ofdead clover leaves and long petioles covers theseeds, which germinate in late summer to estab-lish the next winter’s stand (127). Their persis-tence over many seasons justifies the investmentin seed and careful establishment.In California, sow in September or early

October to get plants well established before coolweather (309). Planting continues throughNovember in the most protected areas.In marginally mild areas, establish with grasses

for winter protection. Subclover stimulates thegrasses by improving soil fertility. You can over-seed pasture or range land without tillage,but youcan improve germination by having livestocktrample in the seed. Subclover often is aeriallyapplied to burned or cleared land. Initial growthwill be a little slower than that of crimson, but alittle faster than white clover (120).Broadcast at 20-30 lb./A in a firm, weed-free

seedbed. Cover seed with a light, trailing harrowor with other light surface tillage to a depth of lessthan one-half inch. Add lime if soil is highly acid—below pH 5.5 (309). Soils low in pH may requiresupplemental molybdenum for proper growth,and phosphorus and sulfur may also be limitingnutrients. Only the T. yanninicum cultivars willtolerate standing water or seepage areas (21,309).Subclover often is planted with rose clover and

crimson clover in California orchard mixes.Crimson and subclover usually dominate, buthard-seeded rose clover persists when dry weath-er knocks out the other two (447).In the East,central Mississippi plantings are rec-

ommended Sept. 1 to Oct. 15, although earlierplantings produce the earliest foliage in spring(120). In coastal Maryland where MT. BARKERplants were tallest and most lush, winterkill(caused when the temperature dropped to 15° For below) has been most severe. Planting in thisarea of Zone 7 should be delayed until the firsttwo weeks of October. Plant at about 22 lb./A forcover crop use in the mid-Atlantic (31) and

Southeast (103). This is about double the usualrecommended rate for pastures in the warmersoils of the Southeast.Small plants of ground-hugging subclover

benefit more from heat radiating from the soilthan larger plants,but are more vulnerable duringtimes of freezing and thawing. Where frostheaving is expected, earlier planting and well-established plants usually survive better thansmaller ones (103).

KillingSubclover dies naturally in early summer afterblooming and seed set. It is relatively difficult tokill without deep tillage before mid-bloom stage.After stems get long and seed sets, you can killplants with a grain drill or a knife roller (95).In northern Mississippi, subclover was the least

controlled of four legumes in a mechanical killtest. The cover crops wererolled with coulters spaced 4inches apart when the plantshad at least 10 inches ofprostrate growth. Whilehairy vetch and crimsonclover were 80 to 100 per-cent controlled, berseemcontrol was 53 percent andsubclover was controlledonly 26 to 61 percent (105).Researchers in Ohio had

no trouble killing post-bloomsubclover with a custom-builtundercutter.The specialized tool is made to slice1 to 2 inches below the surface of raised beds.Theundercutter consisted of two blades that aremounted on upright standards on either side of thebed and slant backward at 45 degrees toward thecenter of the bed.A mounted rolling harrow wasattached to lay the cover crop flat on the surfaceafter being cut (96). The tool severs stalks fromroots while above-ground residue is undamaged,greatly slowing residue decomposition (95).Subclover tolerance to herbicides varies with

cultivar and growth stage. Generally, subclover iseasier to kill after it has set some seed (104, 165).

Subclover

mixes help

keep weeds

in check all

season long

in West Coast

orchards.


Reseeding ManagementThe“over-summering”fate of reseeding subcloverplantings is as critical to their success as is theover-wintering of winter-annual legumes. Thethick mat of vegetation formed by dead residuecan keep subclover seeds dormant if it is not dis-turbed by grazing, tillage,burning or seed harvest.Where cover crop subclover is to be grazedbefore another year’s growth is turned under,intensive grazing management works best toreduce residue but to avoid excess seed bur con-sumption (309).Grazing or mowing in late springor early summer helps control weeds that growthrough the mulch (292).You can improve volunteer regrowth of sub-

clover in warm-season grass mixes by limiting Nfertilization during summer, and by grazing thegrass shorter until cold temperatures limit grassgrowth. This helps even though subcloverseedlings may emerge earlier (21). Subclover flow-ers are inconspicuous and will go unnoticed with-out careful, eye-to-the-ground inspection (103).After plants mature, livestock will eagerly eat

seed heads (120). In dry years when you want tomaintain the stand, limit grazing over summer toavoid over-consumption of seed heads and deple-tion of the seed bank. Close mowing or grazingcan be done any time.

Management ChallengesPossible crop seedling suppression. Theallelopathic compounds that help subclover sup-press weeds also can hurt germination of somecrops.To avoid problems with these crops, delayplanting or remove subclover residue. No-tillplanters equipped with tine-wheel row cleanerscan reduce the recommended 21-day waitingperiod that allows allelopathic compounds todrop to levels that won’t harm crops (101). Killsubclover at least a year before planting peachtrees to avoid a negative effect on seedling vigor.It’s best to wait until August of the trees’ secondsummer to plant subclover in row middles, anArkansas study found (61).The degree to which a cover crop mulch hin-

ders vegetable seedlings is crop specific. Plant-toxic compounds from subclover mulch

suppressed lettuce,broccoli and tomato seedlingsfor eight weeks, but not as severely or as long asdid compounds from ryegrass (Lolium rigidumcv.WIMMERA) mulch. An alfalfa mulch showed nosuch allelopathic effect in an Australian study(395).Guard against moisture competition from sub-

clover at planting. Without irrigation to ensurecrop seeds will have enough soil moisture to ger-minate in a dry year, be sure that the subclover iskilled seven to 14 days prior to planting to allowrainfall to replenish soil moisture naturally (31).

Soil-borne crop seedling disease. In northMississippi tests, residue and leachate fromlegume cover crops (including subclover) causedgreater harm to grain sorghum seedlings, com-pared to nonlegumes. Rhizoctonia solani, a soil-borne fungus, infected more than half thesorghum seedlings for more than a month,but dis-appeared seven to 13 days after legume residueswere removed (101).

N-leaching. The early and profuse nodulation ofsubclovers that helps grass pastures also has adownside—excess N in the form of nitrate cancontaminate water supplies. Topgrowth of sub-clover, black medic and white clover leached 12to 26 lb. N/A over winter, a rate far higher thanred clover and berseem clover, which leachedonly 2 to 4 lb.N/A in a Swedish test (227).

Pest ManagementSubclovers showed little resistance to root-knotnematodes in Florida tests on 134 subclover linesin three years of testing the most promising vari-eties (233).Lygus species, important pests of field, row and

orchard crops in California and parts of theSoutheast, were notably scarce on subcloverplants in a south Georgia comparison. Otherlegumes harboring more of the pests were, indescending order, CAHABA and VANTAGE vetch,hairy vetch, turnip and monoculture crimsonclover (56).Most cultivars imported to the U.S. are low in

estrogen, which is present in sufficient levels in


someAustralian cultivars to reduce fertility in ewes,but not in goats or cattle. Confirm estrogen statusof a cultivar if you plan to graze sheep on it (309).

Crop SystemsInterseeded with wheat. NANGEELA subcloverprovided 59 lb. N/A when it was grown as aninterseeded legume in soft red winter wheat ineastern Texas. That extra N helped boost thewheat yield 283 percent from the previous year’syield when four subclover cultivars were firstestablished and actually decreased yield, com-pared with a control plot. NANGEELA, MT. BARKER,WOOLGENELLUP and NUNGARIN cultivars boostedwheat yield by 24, 18, 18, and 11 bu./A, respec-tively, in the second year of the study. Over allthree years, the four cultivars added 59,51,38 and24 lb.N/A, respectively (44).Plant breeder Gerald Ray Smith of Texas A&M

University worked with several subclovers in east-ernTexas.While the subclovers grew well the firstyear,he concluded that those cultivars need a pro-longed dry period at maturity to live up to theirreseeding performance inAustralia and California.Surface moisture at seed set reduces seed harden-ing and increases seed decay. Midsummer rainscause premature germination that robs the sub-clover seed bank, especially in pastures wheregrasses tend to create moist soil. Most summer-germinating plants die when dry weather returns.In Mississippi, subclover hard seed develop-

ment has been quite variable from year to year. Indry years, close to 100 percent hard seed is devel-oped. Dormancy of the seed breaks down morerapidly on bare soil with wider temperatureswings than it does on mulched soils (133, 134).To facilitate reseeding or to seed into pastures,thegrasses must be mowed back or grazed quiteshort for the subclover to establish (103).

Mix for persistence. California almond growersneed a firm, flat orchard floor from which to pickup almonds.Many growers use a mix of moisture-tolerant TRIKKALA, alkaline-tolerant KOALA, andKARRIDALE,which likes neutral to acid soils.Theseblended subclovers give an even cover acrossmoist swails and alkaline pockets.

Rice N-source. In Louisiana trials, subcloverregrew well in fall when allowed to set seedbefore spring flooding of rice fields. Comparedwith planting new seed, this method yields largerseedling populations, and growth usually beginsearlier in the fall. The flood period seems toenhance dormancy of both subclover and crim-son clover, and germination is robust when thefields are drained (103). Formerly, some Louisianarice farmers seeded the crop into dry soil then letit develop for 30 days before flooding. Early vari-eties such as DALKIETH and NORTHAM may makeseed prior to the recommended rice plantingdate. In recent decades,“water planting”has beenused to control red rice, a weedy relative ofdomestic rice. Water seeding into cover cropresidues has not been successful (36).

Fertility, weed control for corn. In the humidmid-Atlantic region,grain and silage corn no-tilledinto NANGEELA subclover did well in a six-yearNew Jersey trial. With no additional N, the sub-clover plots eventually out-yielded comparisonplots of rye mulch and bare-soil that were con-ventionally tilled or minimum-tilled with fertilizerat up to 250 lb. N/A.The subclover contributedup to 370 lb. N/A (128), an N supply requiringcareful management after the subclover dies toprevent leaching.Control of fall panicum was poor in the first

year, but much better the next two years. Controlof the field’s other significant weed, ivyleaf morn-ing glory, was excellent in all years. Even thoughno herbicide was used in the subclover plots,weed biomass was lowest there (128).Central New Jersey had mild winters during

these experiments. Early spring thaws triggeredsubclover regrowth followed by plungingtemperatures that dropped below 15° F. Thisweakened the plants and thinned the stands.The surviving plants, which formed dense standsat times, were mowed or strip-killed using herbi-cides or tillage. Mowing often induced strongregrowth, so strips at least 12 inches wide provedto be the best to prevent moisture competitionbetween the subclover and the cabbage andzucchini transplants.


Sustainable sweet corn. On Maryland’s EasternShore (one USDA hardiness zone warmer thanNew Jersey), University of Maryland weed spe-cialist Ed Beste reported good reseeding in fourconsecutive years and no problems with standloss from premature spring regrowth.Overwintering MT.BARKER plants sent out stolonsacross the soil surface to quickly re-establish agood stand ahead of sweet corn plantings (31).Beste believes the sandy loam soil with a sand

underlayer at his site is better for subclover thanthe heavier clay soils at the USDA Beltsville stationsome 80 miles north, where hairy vetch usuallyout-performs subclover as a killed organic mulchin transplanted vegetable systems. Winterkillreduced the subclover stand on top of beddedrows one year of the comparison, yet survivingplants between the beds produced nearly as muchbiomass per square foot as did hairy vetch (2).Beste has worked with subclover at his

Salisbury, Md., site for several years, seeding veg-etables in spring, early summer and mid-summerinto the killed or naturally dead cover cropmulch. For three years, subclover at Beste’s sweetcorn system comparison site yielded about 5,400lb. DM/A.Without added N, the subclover plotsyielded as much sweet corn as conventional plotsreceiving 160 lb.N/A.Weed suppression also wasbetter than in the conventional plots. He sprayedglyphosate on yellow nutsedge in fall to preventtuber formation by the grassy weed, the onlyweed that penetrated the subclover mulch (31).Beste sprays paraquat twice to control sub-

clover ahead of no-till, direct seeded zucchini inthe first week of June.His MT.BARKER will set seedand die back naturally at the end of June—still intime to seed pumpkins, fall cucumbers, snapbeans or fall zucchini planted without herbicides(31).Such a no-chemical/dying mulch/perpetuallyreseeding legume system is the goal of cultivarand system trials in California.Seed production in subclovers normally is trig-

gered by increasing day length in spring after theplant experiences decreasing fall day length.Thisexplains why spring-planted subclover inMontana tests produced profuse vegetative

growth,especially when fall rains began,but failedto set any seed (383). Stress from drought andheat also can trigger seed set.

COMPARATIVE NOTES

White and arrowleaf clovers have proved to bebetter self-reseeding clovers than subclover in thehumid South because their seed is held in the air,giving them a better chance to harden. Topreseeding contenders are balansa clover (see Up-and-Coming Cover Crops, p. 191) and southernspotted burr medic (see Southern Spotted BurrMedic Offers Reseeding Persistence, p. 154).While mid-season subclovers generally pro-

duced more dry matter and N than medics fordryland cereal-legume rotations in Montana(381), they did not set seed when grown as sum-mer annuals in the region. Summer growth con-tinued as long as moisture held up in trials there.Vegetative growth increased until frost, as cool,moist fall weather mimicks the Mediterraneanwinter conditions where subclover thrives (383).CLARE is a cultivar of the subclover subspecies

brachycalycinum.Compared with the more com-mon subspecies subterranean (SEATON PARK andDALIAK), CLARE has vigorous seedlings, robustgrowth when mowed monthly and is said to tol-erate neutral to alkaline soils.However, it appearsto be less persistent than other types (61).Subclover,rye and crimson clover provided grass

weed control that was 46 to 61 percent better thana no-cover/no-till system at two North Carolinalocations. Subclover topped the other covers insuppressing weeds in plots where no herbicideswere used.None of the cover crop treatments elim-inated the need for pre-emergent herbicides foreconomic levels of weed control (454).Subclover creates a tighter mat of topgrowth

than vetch (31) or crimson clover (103).

Cultivars. See Comparative Notes, above, andDiversity of Types, Cultivars (p. 165).


SWEETCLOVERS 171

Within a single season on even marginal-ly fertile soils, this tall-growing biennialproduces abundant biomass and mod-

erate amounts of nitrogen as it thrusts a taprootand branches deep into subsoil layers. Given fer-tile soils and a second season, it lives up to its fullpotential for nitrogen and organic matter produc-tion. Early in the second year it provides new topgrowth to protect the soil surface as its rootsanchor the soil profile. It is the most drought-tol-erant of forage legumes, is quite winter-hardy andcan extract from the soil then release phospho-rus, potassium and other micronutrients that areotherwise unavailable to crops.Sweetclover thrives in temperate regions wher-

ever summers are mild. Annual sweetclovers(HUBAM is the most well known) work best in theDeep South, from Texas to Georgia. There, theyestablish more quickly than the biennial types andproduce more biomass in the seeding year insouthern regions.In this chapter,“sweetclover” refers to biennial

types unless otherwise noted.Sweetclover was the king of green manures

and grazing legumes in the South and laterthroughout the Midwest in the first half of thiscentury. Sweetclover is used as a cover crop mostcommonly now in the Plains region,with little usein California.

TypesBiennial yellow sweetclover can produce up to 24inches of vegetative growth and 2.5 tons dry mat-ter/A in its establishment year.During the secondyear, plants may reach 8 feet tall. Root mass andpenetration (to 5 feet) are greatest at the end ofdormancy in early spring, then gradually dissipatethrough the season (443).A distinguishing sweetclover feature is bracts of

tiny blooms through much of its second year.White biennial sweetclovers are taller, morecoarsely stemmed, less drought tolerant, and pro-duce less biomass in both the seeding and secondyears.White types bloom 10 to 14 days later thanyellow, but bloom for a longer season. Theyreportedly establish more readily in New York(450). Tall, stemmy cultivars are better for soilimprovement (120, 361, 422).

SWEETCLOVERSYellow sweetclover (Melilotusofficinalis) and white sweet-clover (M. alba)

Also called: HUBAM (actuallya cultivar of annual whitesweetclover)

Type: biennial, summer annual orwinter annual legume

Roles: soil builder, fertility source,subsoil aerator, weed suppressor,erosion preventer

Mix with: small grains, red clover


biennial spring sown

marginal area

biennial fall sown


Both yellow and white sweetclover have culti-vars bred for low levels of coumarin. This com-pound exists in bound form in the plant andposes no problem during grazing. However,coumarin can cause internal injury to cattle whenthey eat spoiled sweetclover hay or silage.Annual sweetclover (Melilotus alba var.

annua) is not frost tolerant, but can produce upto 9,000 lb. dry matter/A over a summer afterbeing oversown into a grain crop or direct seed-ed with a spring grain nurse crop.The best-knownannual sweetclover cultivar is HUBAM, a nameoften used for all annual white sweetclover.Whileits taproot is shorter and more slender than thatof its biennial cousins, it still loosens subsoil com-paction.

BENEFITS

Nutrient scavenger. Sweetclover appears tohave a greater ability to extract potassium, phos-phorus and other soil nutrients from insolubleminerals than most other cover crops. Rootbranches take in minerals from seldom-disturbedsoil horizons, nutrients that become available asthe tops and roots decompose (361).Research in Saskatchewan during a 34-year

period showed that phosphorus (P) availabilityincreased in subsoil layers relative to surface lay-ers, peaking at an 8-foot depth.Winter wheat andsafflower, with deeper root systems than spring

wheat, could tap the deep P buildup from thelegume roots and fallow leaching,whereas springwheat could not.The vesicular-arbuscular mycor-rhizal (VAM) fungi associated with legume rootscontribute to the increased P availability associat-ed with sweetclover (69, 70).

N source. A traditional green manure crop in theupper Midwest before nitrogen fertilizer becamewidely available, sweetclover usually producesabout 100 lb. N/A, but can produce up to 200 lb.N/A with good fertility and rainfall. In Ohio, it con-tained about 125 lb.N/A by May 15, increasing to155 lb. by June 22. Illinois researchers reportedmore than 290 lb.N/A.

Abundant biomass. If planted in spring andthen given two full seasons,biennial sweetcloverscan produce 7,500 to 9,000 lb. dry matter/A(3,000 to 3,500 lb./A in the seeding year, and4,500 to 5,500 lb./A the second). Second-yearyields may go as high as 8,500 lb./A.

Hot-weather producer. Sweetclover has thegreatest warm-weather biomass production ofany legume, exceeding even alfalfa.

Soil structure builder. Kansas farmer BillGranzow says sweetclover gives his soils higherorganic matter, looser structure and better tilth.See Sweetclover: Good Grazing, Great GreenManure (p. 174). HUBAM annual sweetclover alsoimproved soil quality and increased yield poten-tial in 1996 NewYork trials (451).

Compaction fighter. Yellow sweetclover hasa determinate taproot root up to 1 foot long withextensive branches that may penetrate 5 feet toaerate subsoils and lessen the negative effects ofcompaction on crops.White types have a strongtap root that is not determinate.

Drought survivor. Once established, sweet-clover is the most drought tolerant of all covercrops that produce as much biomass. It is espe-cially resilient in its second year,when it could dowell in a dry spring during which it would be dif-ficult to establish annual cover crops.The yellowtype is less sensitive to drought and easier toestablish in dry soils than the white type.

YELLOW SWEETCLOVER (Melilotus officinalis)

MarianneSarrantonio

SWEETCLOVERS 173

Attracts beneficial insects. Blossoms attracthoneybees, tachinid flies and large predatorywasps, but not small wasps.

Widely acclimated. Self-reseeding sweetclovercan be seen growing on nearly barren slopes,roadrights-of-way, mining spoils and soils that havelow fertility, moderate salinity or a pH above 6.0(183). It also can tolerate a wide range of envi-ronments from sea level to 4,000 feet in altitude,including heavy soil, heat, insects, plant diseases(120) and as little as 6 inches of rain per year.

Livestock grazing or hay. If you need emer-gency forage, sweetclover has a first-year feedvalue similar to alfalfa,with greater volume of less-er quality in the second year.

MANAGEMENT

Establishment & Field ManagementSweetclover does well in the same soils as alfalfa.Loam soils with near-neutral pH are best. Likealfalfa, it will not thrive on poorly drained soils.For high yields, sweetclover needs P and K in themedium to high range. Deficient sulfur may limitits growth (153). Use an alfalfa/sweetcloverinoculant.In temperate areas of the Corn Belt,drill yellow

sweetclover in pure stands at 8 to 15 lb./A orbroadcast 15 to 20 lb./A, using the higher rate indry or loose soils or if not incorporating.In drier areas such as eastern North Dakota,trials

of seeding rates from 2 to 20 lb./A showed that just4 lb./A, broadcast or drilled, created an adequatesole-crop stand for maximum yield.Recommendedrates in North Dakota are 4 to 6 lb./A drilled withsmall grains at small-grain planting, 5 to 8 lb./Abroadcast and harrowed (sometimes in overseed-ing sunflowers), and 6 to 10 lb./A. broadcast with-out incorporating tillage (183).An excessively dense stand will create spindly

stalks that don’t branch or root to the degree thatplants do in normal seedings. Further, the plantswill tend to lodge and lay over, increasing the riskof diseases. So for maximum effect of subsoil pen-etration or snow trapping, go with a lighter seed-ing rate.

Sweetclover produces 50 percent or more hardseed that can lie in soil for 20 years without ger-minating. Commercial seed is scarified to breakthis non-porous seedcoat and allow moisture totrigger germination. If you use unscarified seed,check hardseed count on the tag and do notcount on more than 25 percent germination fromthe hardseed portion.The need for scarifica-tion to produce anadequate stand maybe over-rated, howev-er.The process had noeffect on germinationin six years of fieldtesting in NorthDakota—even whenplanting 70 percenthard seed still in seedpods.Seed at a depth of 1/4 to 1/2 inch in medium to

heavy textured soils, and 1/2 to 1.0 inch on sandysoils. Seeding too deeply is a common cause ofpoor establishment.Seed annual white sweetclover at 15 to 30

pounds per acre. Expect 70 to 90 lb. N/A from4,000 to 5,000 lb. dry matter/A on well-drained,clay loam soils with neutral to alkaline pH.A press-wheel drill with a grass seed attach-

ment and a seed agitator is suitable for plantingsweetclover into a firm seedbed. If the seedbed istoo loose to allow the drill to regulate seedingdepth, run the seed spouts from the grass andlegume boxes to drop seed behind the double-disk opener and in front of the press wheels.Light, shallow harrowing can safely firm theseedbed and incorporate seed (183).In the Canadian Northern Plains, dribble the

seed through drill box hoses directly in front ofthe presswheels for quick and easy establishment(32).If your press-wheel drill has no legume box or

grass-seed attachment, you can mix the legumeand small grain seed, but mix seed often due tosettling. Reduce competition between the cropsby seeding a part of the companion crop first,then seed a mix of the clover seed and the bal-ance of the grain seed at right angles (183).

Winter-hardy and

drought tolerant,

this biennial can

produce up to 200

lb. N/A with good

fertility and rainfall.


Bill Granzow taps biennial yellow sweetcloverto enhance soil tilth, control erosion andprevent subsoil from becoming compacted.Heuses common varieties, either from theelevator or one his father originally boughtfrom a neighbor.Granzow,of Herington,Kan., produces no-

till grain and runs cattle in an area midwaybetweenWichita and Manhattan in the east-central part of the state.Granzow overseedssweetclover into winter wheat in Decemberor January at 12 to 15 lb./A using a rotarybroadcaster mounted on his pickup.Sometimes he asks the local grain cooperativeto mix the seed with his urea fertilizer for thewheat. There’s no extra charge for seedapplication. Alternately,Granzow plantssweetclover at the same rate with March-seeded oats.Yellow sweetclover has overgrown

Granzow’s wheat only when the wheat standis thin and abnormally heavy rains delayharvest.The minimal problem is even rarer inoats, he says.He uses yellow sweetclover with the

companion wheat crop in four possible ways,depending on what the field needs or whatother value he wants to maximize. For each,he lets the clover grow untouched after wheatharvest for the duration of the seeding year.Heused to disk the sweetclover at least twice tokill it. Now 100% no-till, he sprays withRoundup and“a little bit of 2,4-D.” Second-yearoptions include:• Grazing/green manure.Turn in livestockwhen the clover reaches 4 inches tall, letthem graze for several weeks, spray to kill,then plant grain sorghum within a couple ofdays.He feeds an anti-bloat medication to

keep cattle healthy on the lush legumeforage.

• Quick green manure. Spray after it hasgrown 3 to 4 inches, then plant sorghum.This method contributes about 60 poundsof N to the soil. He knocks back persistentre-growing sweetclover crowns in thesorghum by adding 2, 4-D or Banvel to thepostemerge herbicide mix.

• Green manure/fallow. Kill at mid- to fullbloom, leave fallow over summer, then plantwheat again in fall.This method providesabout 120 lb.N/A, according to estimatesfrom Kansas State University.

• Seed crop. He windrows the plants whenabout 50 percent of the seedpods haveturned black, then runs the stalks throughhis combine.To remove all of the hulls, heruns the seed through the combine asecond or third time.

Despite the heavy growth in the second year,yellow sweetclover matures and dies backnaturally. If the residue is heavy, he sets thedrill a bit deeper for planting.He rates fall sweetclover hay from the

seeding year as “acceptable forage.”He’s awarethat moldy sweetclover hay containscoumarin, a compound that can kill cattle, buthe’s never encountered the problem. Second-year yellow sweetclover makes silage at initialto mid-bloom stage with 16 percent proteinon a dry matter basis.“Mixed with grass hay or other silage, it

makes an excellent feed,”he says, adding valueto its cover crop benefits and giving himfarming flexiblity.Updated in 2007 by Andy Clark

Sweetclover: Good Grazing, Great Green Manure

SWEETCLOVERS 175

Spring seeding provides yellow sweetcloverample time to develop an extensive root systemand store high levels of nutrients and carbohy-drates necessary for over-wintering and robustspring growth. It grows slowly the first 60 days(153).Where weeds would be controlled by mow-ing, no-till spring seeding in small grain stubbleworks well.Broadcast seeding for pure sweetclover stands

works in higher rainfall areas in early springwhere soil moisture is adequate for seven to 10days after planting. No-till seeding works well insmall grain stubble.Frostseeding into winter grains allows a harvest

of at least one crop during the life cycle of thesweetclover and helps control weeds while thesweetclover establishes. Apply sweetclover seedbefore rapid stem elongation of the grain. Cutgrain rate about one-third when planting thecrops together.Sweetclover spring seeded with oats exhibited

poor regrowth after oat harvest in two years of aWisconsin study. To establish a sweetclover covercrop in this way, the researchers found sweet-clover did not fare well in years when the com-bine head had to be run low to pick up lodgedoats. When oats remained upright (sacrificingsome straw for a higher cut), sweetclover grewadequately (402).You can plow down spring-planted yellow

sweetclover in late fall of the planting year to cashin early on up to half its N contribution and a bitless than half its biomass.Plant biennial sweetclover through late sum-

mer where winters are mild, north through Zone6.Plant at least six weeks before frost so roots candevelop enough to avoid winter heaving. In theNorthern Plains into Canada, it should be plantedby late August.

First-year management. Seeding year harvestor clipping is usually discouraged, because theenergy for first-year regrowth comes directly fromphotosynthesis (provided by the few remainingleaves), not root reserves (361, 402).Top growth peaks in late summer as the plant’s

main taproot continues to grow and thicken.

Second-year growth comes from crown buds thatform about an inch below the soil surface.Avoidmowing or grazing of sweetclover in the six- toseven-week period prior to frost when it is build-ing final winter reserves. Root production practi-cally doubles between Oct.1 and freeze-up.Sweetclover establishes well when sown with

winter grains in fall, but it can outgrow the grainin a wet season and complicate harvest.

Second-year management. After it breaks win-ter dormancy,sweetclover adds explosive and vig-orous growth. Stems can reach 8 feet beforeflowering,but if left to mature, the stems becomewoody and difficult to manage. Plants may growextremely tall in a “sweetclover year” with highrainfall and moderate temperatures.Nearly all growth the second year is topgrowth,

and it seems to come at the expense of root mass.From March toAugust in Ohio, records show top-growth increasing tenfold while root productiondecreased by 75 percent (443). All crown budsinitiate growth in spring. If you want regrowthafter cutting, leave plenty of stem buds on 6 to 12inches of stubble.You increase the risk of killingthe sweetclover plant by mowing heavier stands,at shorter heights, and/or at later growth stages,especially after bloom (183).Before it breaks dormancy, sweetclover can

withstand flooding for about 10 days withoutsignificant stand loss. Once it starts growing,however, flooding will kill the plants (183).

KillingFor best results ahead of a summer crop or fallow,kill sweetclover in the second year after seedingwhen stalks are 6 to 10 inches tall (183, 361). Itcan be killed by mowing, cultivating or diskingonce it reaches late bloom stage (32). Killingsweetclover before bud stage has several benefits:80 percent of the potential N is present;N releaseis quick because the plant is still quite vegetativewith a high N percentage in young stalks androots; and moisture loss is halted without reduc-ing N contribution.Sweetclover may regrow fromhealthy crowns if incorporated before the end ofdormancy. For optimum full-season organic mat-


ter contribution, mow prior to blossom stagewhenever sweetclover reaches 12 to 24 incheshigh before final incorporation or termination(361). Mowing or grazing at bloom can kill theplants.In dryland areas, the optimum termination date

for a green manure varies with moisture condi-tions. In a spring wheat>fallow rotation in

Saskatchewan, sweetcloverincorporated in mid-Juneof a dry year provided 80percent more N the fol-lowing spring than it didwhen incorporated inearly July or mid-July—even though it yielded upto a third less biomass atthe June date. Mineraliz-ation from sweetcloverusually peaks about a yearafter it is killed. Thepotential rate of N release

decreases as plants mature and is affected by soilmoisture content (147).In this study, the differences in N release were

consistent in years of normal precipitation, butwere less pronounced. Little N mineralizationoccurred in the incorporation year.Nitrogen addi-tion peaked in the following year, and has beenshown to continue over seven years following yel-low sweetclover (147).In northern spring wheat areas of North

Dakota, yellow sweetclover is usually terminatedin early June just at the onset of bloom,when itreaches 2 to 3 feet tall. This point is a compro-mise between cover crop gain (in dry matterand N) and water consumption.A quick kill fromtillage or haying is more expensive and labor-intensive than chemical desiccation, but it stopsmoisture-robbing transpiration more quickly(153).Grazing is another way to manage second-year

sweetclover before incorporation. Start early inthe season with a high stocking rate of cattle tostay ahead of rapid growth. Bloat potential isslightly less than with alfalfa (153).

Pest ManagementSweetclover is a rather poor competitor in itsestablishment year,making it difficult to establishpure sweetclover in a field with significant weedpressure. Once established, it provides effectiveweed control during the first fall and spring of fal-low, whether or not it is harvested for hay, incor-porated or left on the soil surface (33).Sweetclover residue is said to be allelopathic

against kochia,Russia thistle, dandelion,perennialsowthistle, stinkweed and green foxtail. Repeatedmowing of yellow sweetclover that is then left tomature is reported to have eradicated Canada this-tle. Letting sweetclover bloom and go to seeddries out soil throughout the profile,depleting theroot reserves of weeds.Sweetclover weevil (Sitonia cylindricollis) is a

major pest in some areas, destroying stands bydefoliating newly emerged seedlings. Long rota-tions can reduce damage, an important factor fororganic farmers who depend on sweetclover fer-tility and soil improvements. In the worst years ofan apparent 12 to 15-year weevil cycle in his area,“every sweetclover plant across the countrysideis destroyed,” according to organic farmer DavidPodoll, Fullerton, N.D. “Then the weevil popula-tion crashes, followed by a few years wherethey’re not a problem, then they begin to rebuild.”Cultural practices have not helped change the

cycle, but planting early with a non-competitivenurse crop (flax or small grains) gives sweetcloverplants the best chance to survive weevil foraging,Podoll says. Further research is needed to developmanagement techniques to control the weevil.In a three-year Michigan trial of crop rotations

to decrease economic losses to nematodes, a yel-low sweetclover (YSC)>YSC>potato sequenceout-yielded other combinations of rye, corn,sorghum-sudangrass and alfalfa. Two years ofclover or alfalfa followed by potatoes led to a yieldresponse equivalent to application of a nemati-cide for control of premature potato vine death(78). Legume-supplied N coupled with an overallnutrient balance and enhanced cation exchangecapacity from the cover crop are thought to beinvolved in suppressing nematode damage (271).

During its

second season,

yellow sweet-

clover can grow

8 feet tall while

roots penetrate

5 feet deep.

SWEETCLOVERS 177

Crop SystemsIn the moderately dry regions of the central andnorthern Great Plains,“green fallow”systems withwater-efficient legumes can be substituted forbare-ground or stubble mulch fallow. In fallowyears, no cash crop is planted with the intent ofrecovering soil moisture, breaking disease orweed cycles and maximizing yields of followingcash crops. The retained residue of “brown” fal-low lessens the erosion and evaporation of tillage-intensive “black fallow,” but “green fallow” offerseven more benefits in terms of soil biological life,biodiversity,beneficial insect habitat,possible har-vestable crops and alternate forages.Rapeseed (Brassica campestris) is a summer

annual cash crop in the dryland West that canserve as a nurse crop for sweetclover. ASaskatchewan study of seeding rates showed opti-mum clover yield came when sweetclover wassown at 9 lb./A and rapeseed was sown at 4.5lb./A. The mixture allows an adequate stand ofsweetclover that provides soil protection after thelow-residue rapeseed (255).Sole-cropped oilseed species (rapeseed, sun-

flower, crambe and safflower) require herbicidesfor weed control. Many of these materials arecompatible with legumes, offering a post-emer-gent weed-control option if the covers do not ade-quately suppress weeds. The covers greatlyreduce the erosion potential after oilseed crops,which leave little residue over winter (153).

Interplanting works with tall crops. AWisconsin researcher reported success drillingsweetclover between the rows when corn was 6to 12 inches tall. Overseeding sweetclover intosweet corn works even better due to greater lightpenetration.Soil water availability at cover crop planting

and depletion during growth are always a con-cern in semi-arid regions. The potential benefitsmust be balanced against possible negative effectson the cash crop.Sweetclover overseeded into sunflowers at last

cultivation succeed about half the time, NorthDakota trials show. Dry conditions or poor seed-to-soil contact were the main reasons for not get-ting a stand. A heavier seeding rate or earlier

planting will tend to increase stand.Band-seedingsweetclover over the row with an insecticide boxat sunflower planting proved more successful inthe trial. The method also permits between-rowcultivation (153).Even though legume green manures in another

North Dakota study used about 2.8 inches (rain-fall equivalent) more water than fallow, they ledto a 1-inch equiva-lent increase overfallow in soil watercontent in the top 3inches of soil the fol-lowing spring (14).One green fallow

option is plantingyellow sweetcloverwith spring barleyor spring peas. Thisis challenging, however, because barley can beoverly competitive while herbicide compatibilityis a concern with the peas.Further north into the Canadian Great Plains,

sweetclover depleted soil moisture by Septemberof year 1, but by May of year 2, soil moisture wasgreater due to snow trapping, increased infiltra-tion and reduced evaporation (32).Fred Kirschenmann of Windsor, N.D., controls

spring weed flushes on his fallow after sunflow-ers with an initial shallow chisel plowing then arod weeder pass or two before planting sweet-clover with a nurse crop of buckwheat or oats(or millet, if there is less soil moisture). He har-vests buckwheat, hoping for a 900 lb./A yield,then lets the clover grow and overwinter. Inearly summer, when he begins to see yellowblossoms,he disks the cover, lets it dry, then runsa wide-blade sweep plow just below the surfaceto cut apart the crowns.The biomass contribu-tion of the sweetclover fallow builds up organicmatter, he says, in contrast to the black-fallowroute of burning up organic matter to release N.Preventing humus depletion holds back thedreaded kochia weed.In temperate areas you can overseed spring

broccoli with HUBAM annual sweetclover, let thecover grow during summer, then till it in before

Sweetclover is the

best producing

warm-season forage

legume, even

topping alfalfa.


planting a fall crop.Alternatively, you can allow itto winterkill for a thick, lasting mulch.In Pennsylvania, Eric and Anne Nordell seed

sweetclover after early vegetables (in June or July)and allow it to grow throughout the summer. Itputs down a deep taproot before winter, fixesnitrogen and may bring nutrients to the soil sur-face from deep in the soil profile. See Full-YearCovers Tackle ToughWeeds, p. 38.

Other OptionsFirst-year forage has the same palatability andfeeding value as alfalfa, although harvest canreduce second-year vigor. Second-year forage is of

lower quality andbecomes less palatable asplants mature, but maytotal 2 to 3 tons per acre(120).Growers report seed

yield of 200 to 400 lb./Ain North Dakota.Minimizeshattering of seedpodsby swathing sweetcloverwhen 30 to 60 percent ofits pods are brown or

black. Pollinating insects are required for goodseed yield (183).Hard seed that escapes harvest will remain

in the soil seed bank, but organic farmerRich Mazour of Deweese,Neb.,sees that as a plus.A 20- to 30-percent stand in his native grass pas-tures comes on early each spring,giving his cattleearly grazing. Once warm-season grasses start togrow, they keep the clover in check. In tilledfields, sweep cultivators and residue-managementtillage implements take care of sweetclovers withother tap-rooted “resident vegetation,” Mazoursays.

COMPARATIVE NOTES

Sweetclover and other deep-rooted biennial andperennial legumes are not suited for the mostseverely drought-prone soils, as their excessivesoil moisture use will depress yield of subsequentwheat crops for years to come (163).When planting sweetclover after wheat har-

vest, weeds can become a problem. An organicfarmer in northeastern Kansas reports that to killcocklebur, he has to mow lower than the sweet-clover can tolerate. Annual alfalfa can tolerate lowmowing (205).After 90 days’growth in a North Dakota dryland

legume comparison, a June planting of yellowsweetclover produced dry matter and N compara-ble to alfalfa and lespedeza (Lespedeza stipulaceaMaxim). Subclover, fava beans (Vicia faba) andfield peas had the best overall N-fixing efficiency inthe dryland setting because of quick early seasongrowth and good water use efficiency (331).

Cultivars. Yellow cultivars include MADRID,whichis noted for its good vigor and production, and itsrelative resistance to fall freezes. GOLDTOP hasexcellent seedling vigor, matures two weeks later,provides larger yields of higher quality forage andhas a larger seed than MADRID (361).Yellow com-mon and YUKON joined GOLDTOP and MADRID—allhigh-coumarin types—as the highest yielding culti-vars in a six-year North Dakota test (269).Leading white biennial cultivars are DENTA,

POLARA and ARCTIC. POLARA and ARCTIC are adapt-ed to very cold winters. Best for grazing are thelower-producing, low-coumarin cultivars DENTAand POLARA (white) and NORGOLD (yellow).


Sweetclover

tolerates a wide

range of harsh

environments,

poor soils and

pests.

WHITE CLOVER 179

White clovers are a top choice for “livingmulch” systems planted between rowsof irrigated vegetables, fruit bushes or

trees.They are persistent, widely adapted peren-nial nitrogen producers with tough stems and adense shallow root mass that protects soil fromerosion and suppresses weeds.Depending on thetype,plants grow just 6 to 12 inches tall,but thrivewhen mowed or grazed. Once established, theystand up well to heavy field traffic and thriveunder cool,moist conditions and shade.

Three types: Cultivars of white clover aregrouped into three types by size. The lowestgrowing type (Wild White) best survives heavytraffic and grazing. Intermediate sizes (DutchWhite, New Zealand White and Louisiana S-1)flower earlier and more profusely than the largertypes, are more heat-tolerant and include most ofthe economically important varieties. The large(Ladino) types produce the most N per acre ofany white types, and are valued for forage quality,especially on poorly drained soil.They are gener-ally less durable, but may be two to four timestaller than intermediate types.Intermediate types of white clover include many

cultivated varieties, most originally bred for forage.

The best of 36 varieties tested in north-centralMississippi for cover crop usewere ARAN,GRASSLANDKOPU and KITAOOHA.These ranked high for all traitstested, including plant vigor, leaf area, dry matteryield, number of seed-heads, lateness of floweringand upright stems to prevent soil contact. Rankinghigh were ANGEL GALLARDO,CALIFORNIA LADINO andwidely used LOUISIANA S-1 (392).White clover performs best when it has plenty

of lime, potash, calcium and phosphorus, but ittolerates poor conditions better than mostclovers. Its perennial nature depends on newplants continually being formed by its creepingstolons and, if it reaches maturity, by reseeding.White clover is raised as a winter annual in the

South, where drought and diseases weakenstands. It exhibits its perennial abilities norththrough Hardiness Zone 4. The short and inter-mediate types are low biomass producers, whilethe large ladino types popular with graziers canproduce as much biomass as any clover species.

BENEFITS

Fixes N.A healthy stand of white clover can pro-duce 80 to 130 lb.N/A when killed the year afterestablishment. In established stands, it also may

WHITE CLOVERTrifolium repens

Also called: Dutch White, NewZealand White, Ladino

Type: long-lived perennial or winterannual legume

Roles: living mulch, erosion protec-tion, green manure, beneficial insectattraction

Mix with: annual ryegrass, redclover, hard fescue or red fescue


summer annual

perennial


provide some N togrowing crops whenit is managed as a liv-ing mulch betweencrop rows.Because itcontains more of itstotal N in its rootsthan other legumes,partial tilling is anespecially effectiveway to trigger N

release. The low C:N ratio of stems and leavescauses them to decompose rapidly to release N.

Tolerates traffic. Wherever there’s intensivefield traffic and adequate soil moisture, whiteclover makes a good soil covering that keepsalleyways green. It reduces compaction and dustwhile protecting wet soil against trauma fromvehicle wheels.White clover converts vulnerablebare soil into biologically active soil with habitatfor beneficial organisms above and below the soilsurface.

Premier living mulch. Their ability to grow inshade,maintain a low profile, thrive when repeat-edly mowed and withstand field traffic makesintermediate and even short-stemmed whiteclovers ideal candidates for living mulch systems.To be effective, the mulch crop must be managedso it doesn’t compete with the cash crop for light,nutrients and moisture.White clover’s persistencein the face of some herbicides and minor tillage isused to advantage in these systems (describedbelow) for vegetables, orchards and vineyards.

Value-added forage. Grazed white clover ishighly palatable and digestible with high crudeprotein (about 28 percent), but it poses a bloatrisk in ruminants without careful grazing manage-ment practices.

Spreading soil protector. Because each whiteclover plant extends itself by sending out root-likestolons at ground level, the legume spreads overtime to cover and protect more soil surface.Dropped leaves and clipped biomass effectivelymulch stolons, encouraging new plants to take

root each season.Reseeding increases the numberof new plants if you allow blossoms to mature.

Fits long, cool springs. In selecting a fall-seed-ed N-producer, consider white clover in areaswith extended cool springs. MERIT ladino cloverwas the most efficient of eight major legumesevaluated in a Nebraska greenhouse for N2 fixedper unit of water at 50° F.Ladino clover, as well ashairy vetch and fava beans (Vicia faba) were theonly legumes to grow well at the 50° F tempera-ture (334).

Overseeded companion crop. Whether frost-seeded in early spring into standing grain, broad-cast over vegetables in late spring or into sweetcorn in early summer, white clover germinatesand establishes well under the primary crop. Itgrows slowly while shaded as it develops its rootsystem, then grows rapidly when it receives morelight.

MANAGEMENT

Establishment & FieldworkWidely adapted. White clover can tolerate wetsoil—even short flooding—and short dry spells,and survives on medium to acid soils down to pH5.5. It volunteers on a wider range of soils thanmost legumes, but grows better in clay and loamsoils than on sandy soils (120). Ladino preferssandy loam or medium loam soils.Use higher seeding rates (5 to 9 lb./A drilled, 7

to 14 lb./A broadcast) when you overseed inadverse situations caused by drought, cropresidue or vegetative competition. Drill 4 to 6lb./A when mixing white clover with otherlegumes or grasses to reduce competition forlight,moisture and nutrients.Frostseeding of small-seeded clovers (such as

alsike and white) should be done early in themorning when frost is still in the soil. Later in theday,when soil is slippery, stand establishment willbe poor.Frostseed early enough in spring to allowfor several freeze-thaw cycles.Late-summer seeding must be early enough to

give white clover time to become well estab-lished, because fall freezing and thawing can read-

Tough, low-growing

and shade tolerant,

this perennial

is often used as a

living mulch in

vegetable systems.

WHITE CLOVER 181

ily heave the small, shallow-rooted plants. Seedingabout 40 days before the first killing frost is usu-ally enough time. Best conditions for summerestablishment are humid, cool and shaded (120,361). Legumes suffer less root damage from frostheaving when they are planted with a grass.In warmer regions of the U.S. (Zone 8 and

warmer), every seeding should be inoculated. Incooler areas,where N-fixing bacteria persist in thesoil for up to three years, even volunteer wildwhite clover should leave enough bacteria behindto eliminate the need for inoculation (120).Mowing no lower than 2 to 3 inches will keep

white clover healthy.To safely overwinter whiteclover, leave 3 to 4 inches (6 to 8 inches for tallertypes) to prevent frost damage.

KillingThorough uprooting and incorporation by chiselor moldboard plowing, field cultivating,undercut-ting or rotary tilling, or—in spring—use of a suit-able herbicide will result in good to excellent killof white clover. Extremely close mowing and par-tial tillage that leaves any roots undisturbed willsuppress, but not kill,white clover.

Pest ManagementPrized by bees. Bees work white clover blos-soms for both nectar and pollen. Select insect-management measures that minimize negativeimpact on bees and other pollinators. Michiganblueberry growers find that it improves pollina-tion, as does crimson clover (see Clovers BuildSoil, Blueberry Production, p. 182).

Insect/disease risks.White clovers are fairly tol-erant of nematodes and leaf diseases, but are sus-ceptible to root and stolon rots. Leading insectpests are the potato leafhopper (Empoasca fabae),meadow spittlebug (Philaenis spumarius), cloverleaf weevil (Hypera punctata), alfalfa weevil(Hypera postica) and Lygus bug (Lygus spp.).If not cut or grazed to stimulate new growth, the

buildup of vegetation on aged stolons and stems cre-ates a susceptibility to disease and insect problems.Protect against pest problems by selecting resistantcultivars,rotating crops,maintaining soil fertility andemploying proper cutting schedules (361).

Crop SystemsLiving mulch systems. As a living mulch,whiteclover gives benefits above and below groundwhile it grows between rows of cash crops, pri-marily in fruits, vegetables, orchards and vine-yards. Living mulch has not proved effective inagronomic crops to this point. To receive themultiple benefits, manage the covers carefullythroughout early crop growth—to keep themfrom competing with the main crop for light,nutrients, and especially moisture—while notkilling them. Several methods can do that effec-tively.

Hand mowing/in-row mulch. Farmer AlanMatthews finds that a self-propelled 30-inchrotary mower controls a clover mix betweengreen pepper rows in a quarter-acre field.He uses40-foot wide, contour strip fields and the livingmulch to help prevent erosion on sloping landnear Pittsburgh, Pa. In his 1996 SARE on-farmresearch,he logged $500 more net profit per acreon his living mulch peppers than on his conven-tionally produced peppers (259).Matthews mulches the transplants with hay, 12

inches on each side of the row.He hand-seeds thecover mix at a heavy 30 lb./A between the rows.The mix is 50 percent white Dutch clover,30 per-cent berseem clover, and 20 percent HUIA whiteclover, which is a bit taller than the white Dutch.He mows the field in fall, then broadcasts mediumred clover early the next spring to establish a hay

WHITE CLOVER (Trifolium repens—intermediate type)

MarianneSarrantonio


Clovers Build Soil, Blueberry Production

In the heart of blueberry country in theleading blueberry state in the U.S., RichardJames“RJ”Rant and his mother, Judy Rant, arebreaking new ground and reaping greatrewards.Thanks to cover crops such as whiteand crimson clover taking center stage ontheir two family farms, the blueberry crop isthriving and the farmers are reaping significantrewards.The Rants’ soil is also on the receiving end

of the multiple benefits of white and crimsonclover cover crops.Judy and her husband, Richard Rant, planted

their first bushes in the early 1980s while bothwere still working full time off the farm.Theymanaged the farm until retirement withoutgoing into debt—something of anaccomplishment during that period—but theoperation never really took off. Still in highschool when his father passed away, RJ Rantstepped into the operation during college.Choosing farming over graduate school, RJ

began a quest to improve the blueberryoperation and its bottom line.His focus onsoil-building and cover crops proved key tothe success of their operation, now expanded

to two farms:Double-R Blueberry Farm andWind Dancer Farms, jointly operated by RJand his mother, Judy.Michigan blueberry farmers have been

using cover crops for many years, and top-producing Ottawa County farmers are noexception.Growing blueberry bushes onten-foot centers, there is a lot of spacebetween rows that farmers try to manageas economically and efficiently as possible.Seeking something that will not compete withthe cash crop,most farmers choose rye orsod. Both require significant management interms of time and labor, not to mention seedand fuel costs to plant and kill.RJ Rant took a different tack.Their sandy

loam soils were decent but not excellent, andhis research led him to focus his efforts onimproving the soil by reducing tillage andplanting cover crops.While rye, an annualcover crop, required tillage in fall beforeplanting and in spring to kill and incorporate,perennial white clover could be grown fortwo or more years without tilling. Because it islow-growing, the clover required less labor inplanting and mowing.

field and replace the berseem, which is not win-terhardy (259).New Zealand white clover provided good

weed control for winter squash in the wetter oftwo years in a New York trial. It was used in anexperimental non-chemical system relying onover-the-row compost for in-row weed control.Plants were seeded into tilled strips 16 incheswide spaced 4 feet apart.Poor seed establishmentand lagging clover growth in the drier year creat-ed weed problems, especially with perennialcompetitors. The living mulch/compost systemyielded less than a conventionally tilled andfertilized control both years, due in part todelayed crop development from the in-row com-post (282).

The research showed that in dry years,mowingalone won’t suppress a living mulch enough tokeep it from competing for soil moisture withcrops in 16-inch rows.Further,weeds can be evenmore competitive than the clover for water dur-ing these dry times (282).A California study showed that frequent mow-

ing can work with careful management.A whiteclover cover reduced levels of cabbage aphids inharvested broccoli heads compared with clean-cultivated broccoli.The clover-mulched plants, instrip-tilled rows 4 inches wide, had yield and sizecomparable to clean cultivated rows. However,only intensive irrigation and mowing preventedmoisture competition. To be profitable commer-cially, the system would require irrigation or a less

WHITE CLOVER 183

“There are so many positive things I couldsay about cover crops,”Rant says.“The reason Ikeep using them is because they save me timeand money.”Although he started his research and

planted his first Alsike clover crop on his own,RJ soon found research partners at MichiganState University.He cooperates with researcherDale Mutch to fine-tune cover crop selection,planting methods and management options.“I get really excited when I think about

improving my soils,”Rant says.“I see my fieldsas one unified system, and the biology of thesoil in the inter-rows is as important as the soiland fertility up and down my blueberry rows.”Early screening of different cover crops led

Rant to further test crimson clover, a winterannual cover crop that not only grows well infall and spring, but also shows great potentialto reseed itself, further reducing costs.Theyhave also tested red clover, small white clover,mustard, rye and spring buckwheat. Rant sayswhite clover is his favorite because it is lowgrowing and out-competes weeds.

Soil-building remains a primary objective ofRants cover crop program.Compacted soilsare a problem for blueberries,which preferloose, friable soil.To build better soil structure,Rant is working with MSU’s Mutch to improvesoil organic matter with cover crop mulchesand manures.Mutch and Rant are studying crimson clover

reseeding,another cost-saving measure,comparing mowing and tilling the crimsonclover after it has set seed.They are alsostudying pH ranges for the clovers,which prefera higher pH than the blueberry cash crop.Mutch and Michigan State researcher Rufus

Isaacs are helping to elucidate othermanagement aspects of clover cover crops,such as whether honeybees and native beessuch as mason bees and sweat bees areattracted to clovers.“The clovers work really well for blueberry

production, rather than needing to fit systemto cover crop. If you really want to do this, youcan make it work,” says RJ.—Andy Clark

thirsty legume, as well as field-scale equipmentable to mow between several rows in a singlepass (93).

Chemical suppression is unpredictable. Anapplication rate that sets back the clover suffi-ciently one year may be too harsh (killing theclover) or not suppressive the next year due tomoisture, temperature or soil conditions.

Partial rotary tillage. In a NewYork evaluation ofmechanical suppression,sweet corn planting strips20 inches wide were rotary tilled June 2 into whiteclover. Although mowing (even five times) didn’tsufficiently suppress clover, partial rotary tilling attwo weeks after emergence worked well. A stripof clover allowed to pass between the tines led toample clover regrowth. A surge of N within amonth of tilling aided the growing corn.The lossof root and nodule tissue following stress fromtillage or herbicide shock seems to release N from

the clover. Leaf smutcaused less problem on theliving-mulch corn than onthe clean-cultivated checkplot (170).

Crop shading. Sweetcorn shading can holdwhite clover in checkwhen corn is planted in15-inch rows and about 15inches apart within the row.This spacing yieldedhigher corn growth rates, more marketable earsper plant and higher crop yields than conven-tional plots without clover in an Oregon study.Corn was planted into tilled strips 4 to 6 incheswide about the same time the clover was chemi-cally suppressed. Adapted row-harvesting equip-ment and handpicking would be needed to makethe spacing practical (139).

Healthy stands

can produce

80 to 130 lb.

N/A when killed

the year after

establishment.


COMPARATIVE NOTES

• White clover is less tolerant of basic soilsabove pH 7 than are other clovers.

• In aWisconsin comparison, ladino clover bio-mass was similar to mammoth red cloverwhen spring-seeded (402).

• White clover stores up to 45 percent of its Ncontribution in its roots,more than any othermajor legume cover crop.

• Ladino and alsike are the best hay-typelegumes on poorly drained soils.

• Spring growth of fall-seeded white cloverbegins in mid-May in the Midwest, about thesame time as alfalfa.


Unsuppressed white Dutch clover establishedat asparagus planting controlled weeds and pro-vided N over time to the asparagus in aWisconsinstudy, but reduced yield significantly. Establishingthe clover in the second year or third year of anasparagus planting would be more effective(312).

Other OptionsSeed crop should be harvested when most seedheads are light brown, about 25 to 30 days afterfull bloom.Intermediate types of white clover add protein

and longevity to permanent grass pastures with-out legumes.Taller ladino types can be grazed orharvested. Living mulch fields can be overseededwith grasses or other legumes to rotate into pas-ture after vegetable crops, providing IPM optionsand economic flexibility.

WOOLLYPOD VETCH 185

WOOLLYPOD VETCH

Vicia villosa ssp. dasycarpa

Also called: LANA vetch; alsospelled woolypod vetch

Cycle: cool-season annual

Type: legume

Roles: N source, weed suppressor,erosion preventer, add organicmatter, attract bees

Mix with: other legumes, grasses


area of primary utility

viable during mild, moist seasons

Specialty vetches such as woollypod and pur-ple vetch (Vicia benghalensis) are faster-growing alternatives to hairy vetch (Vicia

villosa) in Hardiness Zone 7 and warmer.Requiring little or no irrigation as a winter coverin these areas,they provide dependable,abundantN and organic matter, as well as excellent weedsuppression.Many growers of high-value crops in California

rely on one or more vetch species as a self-reseed-ing cover crop, beneficial insect habitat andmulch. They can mow the vetch during winterand in late spring after it reseeds.Some vineyard managers seed LANA woollypod

vetch each year with oats or as part of a legumemix—common vetch, subterranean clover, amedic and LANA, for example.They plant the mixin alternate alleyways to save on seeding costsand reduce moisture competition,while ensuringsufficient cover that they can mow or disk.LANA’sclimbing tendency (even more so than purple orcommon vetch) and abundant biomass canbecome problems in vineyards and youngorchards,but can be readily managed with regularmonitoring and timely mowing.

In Zone 5 and colder and parts of Zone 6,wool-lypod vetch can serve as a winterkilled mulch—or as a quick, easy-to-mow spring cover—forweed control and N addition to vegetable trans-plants. It’s a good choice as an overwinteringcover before or after tomato crops in Zone 6 andwarmer. In California, LANA provided the most Nand suppressed the most weeds during two con-secutive but distinctly different growing seasons,compared with purple vetch and other legumemixtures (413, 414).

BENEFITS

N Source. A first-year, overwintering stand ofwoollypod vetch easily will provide more than100 pounds of N per acre in any system whenallowed to put on spring growth. The popularLANA cultivar starts fixing N in as little as oneweek after emergence.LANA can contribute as much as 300 pounds of

N its first year or two, given adequate moistureand warm spring growing conditions (273, 396).Fall-planted LANA incorporated before a corn cropcan provide a yield response equivalent to 200 lb.


N/A, a California study showed (273). Similarresults have been seen in tomato research inCalifornia (396). In western Oregon, a yieldresponse equivalent to 70 lb. N/A for sweet cornhas been observed (364).

Plenty of soil-building organic matter.Woollypod typically produces more dry matterthan any other vetch. LANA shows better earlygrowth than other vetches, even during cool latefall and winter weather in Zone 7 and warmer.LANA shows explosive growth in early spring inthe Pacific Northwest (364) and in late winter and

early spring in Californiawhen moisture is ade-quate. It can provide upto 8,000 lb. DM/A, whichbreaks down quickly andimproves soil structure(63, 273, 396).

Frost protectant. Someorchard growers havefound that keeping a thickfloor cover before the

blossom stage can help prolong a perennial crop’sdormant period by up to 10 days in spring.“Thisreduces the risk of early frost damage (to the blos-soms, by delaying blossoming) and lengthens theblossoming period of my almond trees,” notesalmond grower GlennAnderson,Hilmar,Calif.

Smother crop.Woollypod’s dense spring growthsmothers weeds and also provides some allelo-pathic benefits. Of 32 cover crops in a replicatedstudy at a California vineyard, only LANA com-pletely suppressed biomass production of thedominant winter annual weeds such as chick-weed, shepherd’s purse, rattail fescue and annualryegrass (422).

Beneficial habitat. Woollypod vetch attractsmany pollinators and beneficial insects. In someorchards, these beneficials move up into the treecanopy by late spring, so you can mow the floorcover after it reseeds and not worry about loss ofbeneficial habitat (184).

MANAGEMENT

Establishment & FieldworkWoollypod does well on many soil types—evenpoor, sandy soil—and tolerates moderately acidic tomoderately alkaline conditions. It’s well-adapted tomost orchard and vineyard soils in California (422).It establishes best in recently tilled, nutrient-

deficient fields.Tillage helps enhance the reseed-ing capability of vetches (63). LANA woollypodvetch hasn’t done as well in some no-till systemsas it was expected to.Given adequate moisture, however, broadcasting

LANA even at low to moderate rates—and with lightincorporation—can give satisfactory results from fallseedings, especially if the stand is allowed to growthroughmid-spring.If your goal is to shade out com-petition quickly, however, broadcast at medium tohigh rates and incorporate lightly.You might not recognize the emerging plant

without its characteristic multiple leaflets, saysGlenn Anderson.“You should spot it within twoweeks of planting, three at the latest, dependingon temperature and soil conditions. Even at 6inches, it’ll still look spindly.It won’t really leaf outuntil late winter and early spring, when moreaggressive growth kicks in.” That may continueuntil maturity in mid- to late May.

Fall planting.Most growers seed at low to medi-um rates, regardless of seeding method. If drilling,1/2 to 1 inch deep is best, although up to 2 incheswill work for early seedings. If broadcasting, fol-low with a cultipacker or a shallow pass of aspike-toothed harrow.Seedbed preparation is crucial for establishing

a healthy cover crop stand in vineyards.Californiaviticulturist and consultant Ron Bartolucci rec-ommends making two passes with a disk to killexisting vegetation and provide some soil distur-bance. He cautions against using a rotary tiller,which can pulverize the soil and reduce its water-holding capacity (211).Bartolucci prefers to drill rather than broadcast

cover crops, saving on seed costs and ensuringseed-to-soil contact. He recommends the eco-nomical, alternate row planting that also ensureseasy access for pruning grape vines.

Woollypod vetch

is often used

in mixes in

California

orchards and

vineyards.

WOOLLYPOD VETCH 187

Don’t wait too long in fall to seed woollypodvetch in Zone 7 and warmer,however. If you waituntil the soil starts getting cold, in mid-October inOregon and early November in parts of centralCalifornia,germination will be poor and the standdisappointing. Seed too early, though, and youmiss the early moisture benefit of the CentralValley’s fog season and will need to irrigate morebefore the rainy season.Regardless of your planting method,seed wool-

lypod vetch into moist soil or irrigate immediate-ly after seeding to help germination (273). Ifirrigation is an option but you want to conservewater costs, try seeding just before a storm is fore-cast, then irrigate if the rain misses you.

Spring planting. Planted in early spring, woolly-pod vetch can provide plowdown N by MemorialDay for a summer annual cash crop in theNortheast.

Mowing & ManagingWoollypod vetch can survive freezing conditionsfor days, but severe cold can markedly reduce itsdry matter and N production (212, 273).In most cases, main challenges for an estab-

lished woollypod vetch stand include managingits abundant growth and viny tendrils and ensur-ing adequate moisture for your primary crop. Inwet environments such as western Oregon, how-ever, LANA vetch can retard spring soil drying andseedbed preparation for summer crops (364).Woollypod responds well to mowing,as long as

you keep the stand at least 5 inches tall and avoidmowing during the two-month period just beforeit reseeds. “I can mow as late as mid-March andstill see good reseeding,” says Glenn Anderson, anorganic almond grower in California’s CentralValley.“After that, I may mow if I want to preventsome frost damage, but I know I’ll lose some ofthe vetch through reduced reseeding.”Anderson usually mows the floor cover once or

twice before mid-March and after it reseeds. Hecuts in the direction of prevailing winds—whichcan be on a diagonal to his tree rows—to facilitateair movement throughout the orchard, especiallywhen he anticipates moist air heading his way.In vineyards,“high chopping” legume mixes to

a 12-inch height can help keep them from trellis-

ing over vine cor-dons. In vine-yards withoutsprinklers forfrost protection,some growersi n c o r p o r a t elegume mixes inspring, before thesoil becomes toodry for disking.Where sprinklers areused, the covers mightbe allowed to grow for alonger period and pro-vide additional N.Timing isimportant when disking,however, as you don’t wantto make equipment accessdifficult or compact soilduring wet spring condi-tions (211).Given the high dry matter production from

woollypod vetch when it’s allowed to grow atleast until late March, two or three diskings ormowings will encourage rapid decomposition.Power spaders can reduce soil compaction whenincorporating vetches in spring conditions, com-pared with heavier disk harrows (421).

Moisture concerns. Many orchard and vineyardgrowers find it helpful to drip irrigate tree or vinerows if they are growing an aggressive cover cropsuch as LANA between the rows for the first time.In California vineyards where irrigation isn’t used,a few growers report that vines seem to lose vigorfaster when grown with cover crops. Othershaven’t observed this effect.After a few years ofgrowing leguminous covers, many find that theirsoil is holding moisture better and they need lesswater to make the system work.

Reseeding concerns. Vetch mixtures often failto reseed effectively, especially if they have beenmowed at the wrong time or soil fertility is high.Some vineyard managers expect low persistenceand reseed a vetch mix in alternate rows everyfall, or reseed spotty patches.

ElayneSears

WOOLLYPODVETCH(Vicia villosa ssp.dasycarpa)


Regardless of mowing regime, LANA’s persis-tence as a self-reseeding cover diminishes overtime, and other resident vegetation starts to takeover.That’s a sign that the cover’s water-holding,fertility- and tilth-enhancing benefits have kickedin, says GlennAnderson.It’s natural to expect a change in the resident

vegetation over time, observes Anderson. After afew years of reseeding itself—and providing

abundant dry matter andnitrogen—the LANA hehad clear seeded at lowrates between orchardrows on half his acreageeventually diminished toabout 10 percent of theresident vegetation, henotes. Subclovers andother legumes he intro-duced have becomemore prominent. Those

legumes may have better self-reseeding capabilitythan LANA, other growers note.

Pest ManagementWoollypod vetch outcompetes weeds and willquickly resolve most weed problems if seeded athigh rates. Woollypod also provides some allelo-pathic benefits. A root exudate can reduce growthin some young grasses, lettuces and peas,however.Hard seed carryover can cause LANA to become

a weed in subsequent cash crops and vineyards,however (102). Its strong climbing ability cancover grape vines or entwine sprinklers. Inorchards,it’s fairly easy to cut or pull LANA vines outof the canopy of young trees. Mowing or “highchopping”may be needed, especially in vineyards,even though this can reduce LANA’s reseeding rate.Insects pests aren’t a major problemwith wool-

lypod vetch, in part because it attracts lady bee-tles, lacewings, minute pirate bugs and otherbeneficials insects that help keep pests in check.LANA can be a host of Sclerotinia minor, a soil-

borne pathogen that causes lettuce drop, a fungaldisease affecting lettuce, basil and cauliflowercrops. In a California study involving cover cropsthat were deliberately infected with S.minor, thepathogen levels were associated with higher let-

tuce drop incidence the summer after LANA hadbeen incorporated, but wasn’t as problematic thefollowing year.Woollypod vetch probably isn’t agood choice if you’re growing crops susceptibleto this pathogen.

Other OptionsSeed.Woollypod vetch is a prolific seed producer,but its pods are prone to shattering. You canincrease seed harvest by raking the field (withoutmowing, if possible) to gather the crop intowindrows for curing, before combining with abelt-type rubber pickup attachment (421).

Forage. Like most vetches, LANA is a somewhatbitter yet palatable forage when green, and thepalatability increases with dryness (421). It is anutritious forage for rangeland use (421).For hay, it is best cut in full bloom.The leaves

dry rapidly and swaths can be gathered within aday or two (421).

COMPARATIVE NOTES

• Woollypod has slightly smaller flowers thanhairy vetch, and its seeds are more oval thanthe nearly round seeds of hairy vetch. LANAalso has a higher proportion of hard seed thanhairy vetch (422).

• LANA shows more early growth than commonvetch, although both increase their biomassdramatically by midspring.

• LANA and purple vetch are more cold-sensitivethan common vetch or hairy vetch.Onceestablished, LANA can tolerate early frosts fora few days (especially if the temperaturedoesn’t fluctuate widely or with some snowcover) and is hardier than purple vetch,whichis more susceptible to early spring dieback(149).

• LANA flowers about three weeks earlier thanpurple vetch and has a better chance of set-ting seed in dryland conditions (273).

• LANA and LANA mixes suppress weeds betterthan purple vetch (149).


LANA woollypod

vetch shows

explosive growth

in early spring

in the Pacific

Northwest.

TESTING COVER CROPS 189

To find your best cover crops, you needn’tbecome Dr. Science or devote your life toresearch. It’s not hard to set up valid,on-farm testsand make observations. Follow these steps:

A. Narrow your options.Aim for a limited-scaletrial of just two to five species or mixtures.Youcan test the best one or two in a larger trial thenext year. Unsure of the best place and time inyour rotation? Start with small plots separatedfrom cropped fields and plant over a range ofdates, under optimal soil and weather conditions.If you’re sure where and when to plant and havejust two or three covers to try, put the trial rightin your cropped fields,using your normal seedbedpreparation.This method provides rapid feedbackon how the cover crops fit into your cropping sys-tem. Keep in mind management may need sometweaking (such as seeding rate or date) to get thebest results.

B. Order small seed amounts. Many compa-nies provide 1- to 10-pound bags if you give themadvance notice. If 50-pound bags are the onlyoption, arrange to share it with other growers.Don’t eliminate a species just because seed priceseems high. If it works well, it could trim othercosts.You could consider growing your own seedeventually, and perhaps even selling it locally. Besure to obtain appropriate inoculants if you’ll betesting legumes, which require species-specificrhizobial bacteria so the cover can capture and“fix” N efficiently. See Nodulation: MatchInoculant to Maximize N (p. 122).

C. Determine plot sizes. Keep them smallenough to manage, yet large enough to yield ade-quate and reliable data. Plots two to four rowswide by 50 to 100 feet could suffice if you growvegetables for market. If you have 10 or moreacres,quarter- or half-acre plots may be feasible. If

you use field-scale machinery, establish field-length plots. For row crops, use plots at least fourrows wide, or strips based on your equipmentwidth. Keep in mind the subsequent crop’s man-agement needs.

D. Design an objective trial. Plots need to be asuniform as possible, randomly selected for eachoption you’re testing,and preferably replicated (atleast two or three plots for each option). If partsof the field have major differences (such as poor-er drainage or weedy spots),put blocks or groupsof plots together so each treatment has equal rep-resentation in each field part,or avoid those areasfor your trial entirely. Label each plot and make amap of the trial area.

E. Be timely. Regard the trial as highly as anyother crop. Do as much or as little field prepara-tion as you would for whole fields, and at anappropriate time. If possible, plant on two ormore dates at least two weeks apart. In general,seed winter annuals at least six weeks before akilling frost.Wheat and rye can be planted later,although that will reduce the N-scavenging signif-icantly.

F. Plant carefully. If seeding large plots withtractor-mounted equipment, calibrate your seed-ing equipment for each cover crop. This canprevent failures or performance differences dueto incorrect seeding rates. Keep a permanentrecord of drill settings for future reference. Ahand-crank or rotary spin seeder works well forsmall plots getting less than five pounds of seed.Weigh seed for each plot into a separate con-tainer. To calculate seeding rates for small plots,use this formula: 1 lb./acre = 0.35 oz (10 grams)/1000 ft2 area seeded. If your cover crop seedingrate calls for 30 lb/acre, multiply 0.35 oz by 30.You will need 10.5 oz (300 grams) of seed for

Appendix A

TESTING COVER CROPS ON YOUR FARMby Marianne Sarrantonio


each 1000 ft2 you seed. Put half the seed in theseeder and seed smoothly as you walk the lengthof the field and back, with a little overlap in thespread pattern.Then seed the remainder while walking in per-

pendicular directions so you crisscross the plot ina gridlike pattern. If broadcasting by hand, use asimilar distribution pattern.With small seed, mixin sand or fresh cat litter to avoid seeding toomuch at a time.

G. Collect data. Start a trial notebook or binderfor data and observations. Management informa-tion could include:• field location• field history (crops, herbicides, amendments,unusual circumstances, etc.)

• plot dimensions• field preparation and seeding method• planting date and weather conditions• rainfall after planting• timing and method of killing the cover crop• general comments

Growth data for each plot might include:• germination rating (excellent,OK,poor, etc.),seven to 14 days after seeding

• early growth or vigor rating, a month afterestablishment

• periodic height and ground cover estimates,before killing or mowing

• periodic weed assessments• a biomass or yield rating

Also rate residue before planting the next crop.Rate survival of winter annuals in early spring asthey break dormancy and begin to grow. If youplan to mow-kill an annual, log an approximateflowering date. Regrowth could occur if most ofthe crop is still vegetative. Rate overall weatherand record dates such as first frost.Note anythingyou think has a bearing on the outcome, such asweed infestations. If time allows, try killing thecover crops and continuing your expected rota-tion, at least on a small scale.You might need handtools or a lawn mower. Use field markers toidentify plots.

H. Choose the best species for the wholefarm system. Not sure which covers did best?Whatever you found, don’t be satisfied with onlya single year’s results.Weather and managementwill vary over time.Assess performance by asking some of the

questions you answered about the cover niche(see Selecting the Best Cover Crops for yourFarm, p. 12).Also ask if a cover:• was easy to establish and manage• performed its primary function well• avoided competing excessively with the pri-mary crop

• seemed versatile• is likely to do well under different conditions• fits your equipment and labor constraints• provides options that could make it evenmore affordable

In year two, expand the scale.Test your best-per-forming cover as well as a runner-up.With fieldcrops, try one-acre plots; stick with smaller plotsfor high-value crops. Also try any options thatmight improve the cover stand or its benefits.Entries for the major cover crops in this bookinclude some management tips that can help.Record your observations faithfully.

I. Fine-tune and be creative. Odds are, youwon’t be completely satisfied with one or moredetails of your “best” cover. You might need tosacrifice some potential benefits to make a coverwork better in your farm system. For example,killing a cover earlier than you’d like will reducethe amount of biomass or N it provides,but couldensure that you plant summer crops on time. Inmost cases, fine-tuning your management alsomakes it more affordable.Lowering a seeding rateor shifting the seeding date also could reduce thetillage needed. Narrower rows in your cash cropmight hinder establishment of an overseededlegume but reduce weeds and bump up the cashcrop yield. Don’t expect all of a cover’s benefitsto show up in yearly economic analyses. Somebenefits are hard to assess in dollars.Your best covers may seem well-suited to your

farm, but there could be an up-and-coming

UP-AND-COMING COVER CROPS 191

species or management technique you haven’tthought of testing. See Up-and-Coming CoverCrops (p.191) for a few examples.Overwhelmed?You needn’t be. Initiative and common sense—traits you already rely on—are fundamental to anyon-farm testing program. As a grower, you alreadytest varieties, planting dates and other manage-ment practices every year. This section offers

enough tips to start testing cover crops.You alsocan collaborate with others in your region to poolresources and share findings. There’s a goodchance others in your area could benefit fromyour cover cropping wisdom![Adapted and updated in 2006 from Northeast

Cover Crop Handbook by Marianne Sarrantonio,Rodale Institute, 1994.]

Appendix B

UP-AND-COMING COVER CROPS

Balansa cloverIdentified as a promising new cover crop inscreening trials throughout the Southeastern U.S.,balansa clover (Trifolium michelianum Savi) is asmall-seeded annual legume with superior reseed-ing potential compared with other legumes,including crimson clover.Well-adapted to a widerange of soil types, balansa performs particularlywell on silty clay soil with a pH of about 6.5.Established stands tolerate waterlogging, moder-ate salinity,and soil pH from 4.5 to 8.0. It does notdo well on highly alkaline soils (30). It is consid-ered marginal in Zone 6B.Balansa and other reseeding legumes were

screened in Zones 6,7,and 8 (from the Gulf Coastto northernTennessee, and from Georgia to west-ern Arkansas). TIBBEE crimson clover (Trifoliumincarnatum) was used as a phenological check.Growth was terminated 2 to 3 weeks after TIBBEEbloomed at each location to identify adaptedcover crops that reseed earlier than TIBBEE.Spotted burclover (Medicago arabica) and bal-ansa clover were the best reseeding legumes thatwere hardy throughout zone 7A. Of these, onlybalansa clover is commercially available.Balansa clover is open pollinated. Flowers vary

from white to pink and are attractive to bees.Ungrazed,it growsup to three feet high andproducesthickhollow stems that arepalatable andof good feedvalue.It becomes more prostrate when grazed.Balansa clover was named Trifolium miche-

lianum Savi in 1798. It is sometimes called

Trifolium balansae or Trifolium michelianumsubsp. balansae.A landrace of balansa clover col-lected in Turkey in 1937 was released in 1952 bythe Alabama office of NRCS with the name MIKE.Small amounts of seed of this accession are avail-able from the Plant Introduction station in Athens,GA.Balansa clover seed is quite small, so planting

only 5 lb./A gives a dense stand.Seed is producedcommercially only in Australia. Balansa cloverrequires a relatively rare inoculant, designated“Trifolium Special #2” by Liphatech, Inc., manu-facturer of “Nitragin” brand inoculants. KamprathSeed Co. imports balansa seed (See SeedSuppliers, p.195). Some seed suppliers offer coat-ed seed that is pre-inoculated. The price perpound of coated seed is about the same as bareseed, but 1/3 of the weight is coating so the seed-ing rate for coated seed should be increased to 8lb./A.PARADANA is the cultivar that has been most

widely tested in the U.S. It was released in 1985by the South Australia Department of Agriculture.It was derived fromTurkish introductions crossedand tested at Kangaroo Island, NSW, Australia.Seed yields over 550 lb./A have been obtained.BOLTA is 1-2 weeks later than PARADANA andFRONTIER is 2-3 weeks earlier. FRONTIER, a selectionout of PARADANA, has replaced its parent in theseed trade in recent years.While PARADANA seed matures slightly earlier

than crimson clover, it often does not produce as


much biomass. Nitrogen accumulation in aboveground biomass is about 60 lb./A at full bloom.Balansa can reseed for several years from a singleseed crop, due to its relatively high amount ofhard seed. It reseeded for four years followingmaturation of a seed crop in 1993 in Senatobia,Miss., and for at least two years in no-till systemsat several other locations inAlabama,Georgia andMississippi. Neither TIBBEE nor AU ROBIN crimsonclover reseeded for more than one year at anylocation in those tests. Balansa clover does notreseed well after tillage, probably because thesmall seeds are buried too deeply.Allowing balansa clover to grow for 40 days

past first bloom every 3 to 4 years will allowstands to persist indefinitely in no-till systems.Reseeded stands are denser,bloom 5 to 7 days ear-lier, and are more productive than planted standsbecause growth begins as soon as conditions arefavorable and seedling density is higher.However,seed cost is minor compared to opportunity costand risk associated with delaying main crop plant-ing. Waiting past the optimum planting date toencourage reseeding is only practical in rotationsthat include main crops optimally planted in Mayin the Southeastern U.S.Balansa is less likely than crimson clovers to

host root-knot nematodes (Meloidogyne incog-nita, race 3).GaryWindham,USDA-ARS,Starkville,Miss., found that balansa had egg mass indexscores between 2.3 and 2.9. For comparison, avery resistant white clover scored 1.5,most crim-son clovers score between 3 and 3.5 and very sus-ceptible crops like REGAL white clover score 5on a scale from 1 to 5.—Seth DabneyUSDA-ARS National Sedimentation LabP.O. Box 1157 Oxford,MS 38655-2900662-232-2975; [email protected]

Black oatBlack oat (Avena strigosa L.) is the No. 1 covercrop on millions of acres of conservation-tilledsoybean in southern Brazil, and has potential foruse in the southern USA (Zones 8-10).Black oat produces large amounts of biomass,

similar to rye. It maintains a narrower carbon tonitrogen (C:N) ratio than rye so it cycles nitrogen

better than rye, important for nitrogen manage-ment in conservation tillage systems. It breaks dis-ease cycles for wheat and soybean and is resistantto root-knot nematodes.It is very resistant to rustsand has exceptional allelopathic activity for weedcontrol. It is easy to kill mechanically.Black oat is adapted for use as a winter cover

crop in the lower Coastal Plain of the USA, includ-ing Zones 8b-10a. It has done well in fall plantingsin Zone 8b, but winterkilled one year of six atsome locations within this zone, dependent onplanting date.Planting dates are similar to common oat. If

planted too early, it is more susceptible to win-terkill and lodging. Planting in late winter (earlyFebruary) yielded good biomass and groundcover for late planted cash crops in the lowerCoastal Plain.Seed 50-70 lb./A for use as a cover crop, 40

lb./A for seed production. In the Southeast, fallplantings (November) result in seed ripening inmid May through early June. Seed yields rangefrom 800 to 1400 lb./A. Seed is available commer-cially in limited amounts.One cultivar, SOILSAVER, was selected for

increased cold tolerance and released by AuburnUniversity and IAPAR (Institute of Agronomy ofParaná, Brazil). Auburn University and USDA-ARSresearchers developed it from a population ofIAPAR-61-IBIPORA, a public variety from theInstitute of Agronomy of Parana, Brazil (IAPAR)and the Parananese Commission for Evaluation ofForages (CPAF).SOILSAVER black oat has several advantages as a

cover crop.It tillers well,producing good soil cov-erage in relation to total biomass produced.It sup-presses broadleaf weeds extremely well. In onestudy,weed control in conservation tillage cotton(Gossypium hirsutum L.) averaged 34% withblack oat compared to 26% for rye,19% for wheat,and 16% with no cover crop.—D.W.ReevesResearch LeaderUSDA-ARS, J. Phil Campbell Sr. Natural ResourceConservation Center1420 Experiment Station RoadWatkinsville,GA 30677

UP-AND-COMING COVER CROPS 193

706-769-5631 ext. 203fax [email protected]

Additional Information:SoilSaver—A Black OatWinter Cover Cropfor the Lower Southeastern Coastal Plain. 2002.USDA-ARS National Soil Dynamics Lab.Conservation Systems Fact Sheet No. 1.www.ars.usda.gov/SP2UserFiles/Place/64200500/csr/FactSheets/FS01.pdf

LupinLupins are cool-season annual legumes that pro-vide plenty of N and can be grown widely in theUSA and southern Canada.Lupins have aggressivetaproots, especially the narrow-leaf cultivars.Youcan kill lupins mechanically or with herbicides.Their hollow stems crush or break readily,makingit easy to plant cash crops using conservationtillage equipment.White lupin (Lupinus albus L.) and blue or nar-

row-leaf lupin (Lupinus angustifolius L.) specieswere originally named after their flower colors,but both species now have cultivars with white,blue or magenta/purple flowers. Blue lupin isadapted to the lower Coastal Plain and is morereadily identified by its narrow leaflets (about 0.5-inch wide) rather than flower color.As a fall and winter cover crop in the southeast-

ern USA, white lupin is the most cold-tolerant.Some cultivars overwinter as far north as theTennessee Valley. They typically produce 100 to150 lb. N/A when fall-planted and killed in earlyspring.Seed spring cultivars in earlyApril in the north-

ern U.S. and southern Canada. Kill in June whenthey’re at peak biomass (early-bloom to early-podstage).For use as a cover crop, drill lupins no deeper

than 1 inch at 70 lb./A for small-seeded blue vari-eties to 120 lb./A for larger-seeded white vari-eties. At $30 to $40 per acre, the seed is relativelyexpensive. Be sure to inoculate lupin seed withcompatible rhizobia.Three winter-hardy lupin cultivars are readily

available on a commercial scale. TIFWHITE-78

white lupin and TIFBLUE-78 blue or narrow-leaflupin were both released by USDA’s AgriculturalResearch Service in the 1980s. These two vari-eties, and other modern varieties, are “sweet”types as opposed to“bitter” types that were wide-ly grown in the South prior to 1950. Sweet vari-eties have a low concentration of naturallyoccurring alkaloids. Sweet lupin is favored bywildlife, especially deer. Sweet lupin cover cropsmay act as a trap crop for thrips (Frankliniellaspp.) in cotton plantings, but this has yet to beconfirmed by research.AU HOMER bitter white lupin is a new release by

Auburn University derived from Tifwhite-78. Itwas selected for increased alkaloid content foruse as a cover crop. Alkaloids make lupin seedand forage unpalatable for livestock, but also playa major role in resistance to disease, insects andnematodes.Lupins are susceptible to many fungal and viral

diseases and should not be grown in the samefield in successive years.Rather,rotate lupin covercrops with a small grain cover crop, ideally in arotation that allows three years between lupinplantings. Lupin are intolerant to poorly drainedsoils.

For information about lupins and seed sources,contact: Edzard van Santen, Professor CropScience,Agronomy & Soils Dept., 202 FunchessHall,Auburn University,Auburn,AL 36849;334-844-3975; fax [email protected]

Sunn HempA tropical legume,sunn hemp (Crotalaria junceaL.) can produce more than 5,000 lb. dry matter/Aand 120 lb.N/A in just nine to 12 weeks. It can filla narrow niche between harvest of a summercrop and planting of a fall cash or cover crop andis especially fitted to vegetable production. Sunnhemp sown by September 1 following a corncrop in Alabama, for example, can produce anaverage of 115 lb.N/A by December 1.Sunn hemp is not winter hardy and a hard

freeze easily kills it. Sow sunn hemp a minimumof nine weeks before the average date of the first


fall freeze. Seed at 40 to 50 lb./A,with a cowpea-type inoculant.Sunn hemp seed is expensive, about $2.25/lb.,

so the cost may be prohibitive for large-scaleplantings. Seed can be produced only in tropicalareas, such as Hawaii, and currently is importedonly by specialty seed companies.

A New Alternative for South FloridaProducersA study by the NRCS Plant Materials Center(PMC) in Brooksville,Florida,concluded that sunnhemp seed can be a viable alternative cash cropfor southern Florida growers. Sunn hemp is anannual legume that suppresses some types ofnematodes and can produce over 5,000 poundsof biomass and 100 pounds of nitrogen per acrewithin a few months. Because of its potential usein alternative pest management systems and as asustainable biological source of nitrogen, sunnhemp is a promising cover crop for rotation withvegetables throughout the Southeastern U.S.Unfortunately, its use has been limited by the

high seed cost—most is shipped from Hawaii asseed production requires a tropical climate. Twoyears ago, the NRCS PMC in Brooksville initiateda study to determine which zones in Floridacould most economically produce sunn hempseed.Seed was distributed to 15 growers through-out Florida and although many locations lost theircrop to frost, sunn hemp stands in coastal coun-ties below the 27th parallel consistently pro-duced up to 370 pounds of seed per acre.Growers in more southern areas, such asHomestead, obtained even higher yields.Your contact is Clarence Maura, Manager,NRCS Brookville Plant Materials Center, at352-796-9600 or [email protected].

A management caution: Many Crotalariaspecies contain alkaloids that are poisonous tolivestock.However, the sunn hemp variety TROPICSUN,developed jointly by the University of Hawaiiand USDA-NRCS, has a very low level of alkaloidand is suitable for use as a forage.Research suggests that sunn hemp is resistant

and/or suppressive to root-knot (Meloidogynespp.) and reniform (Rotylenchulus reniformis)nematodes.—D.Wayne Reeves (see p. 192)

Additional Information:Mansoer, Z.,D.W.Reeves and C.W.Wood. 1997.Suitability of sunn hemp as an alternativelate-summer legume cover crop.Soil Sci. Soc.Am. J. 61:246-253.

Balkcom,K. and D.W.Reeves. 2005. Sunnhemp utilized as a legume cover crop for cornproduction. Agron. J. 97:26-31.

Sunn Hemp:A Cover Crop for Southern andTropical Farming Systems.USDA-NRCS SoilQuality Technical Note No. 10.May 1999.Available at: http://soils.usda.gov/sqi/files/10d3.pdf

K.-H.Wang and R.McSorley.Management ofNematodes and Soil Fertility with Sunn HempCover Crop. 2004.University of FloridaCooperative Extension. Publication #ENY-717.http://edis.ifas.ufl.edu/NG043

Valenzuela,H. and J. Smith. 2002.‘Tropic Sun’Sunnhemp.University of Hawaii CooperativeExtension. Publication #SA-GM-11.www.ctahr.hawaii.edu/sustainag/GreenManures/tropicsunnhemp.asp

SEED SUPPLIERS 195

This list is for information purposes only. Inclusion does notimply endorsement, nor is criticism implied of firms notmentioned.

Adams-Briscoe Seed Co.P.O. Box 19325 E. Second St.Jackson,GA 30233-0019770-775-7826fax [email protected],winter peas, vetches, cowpeas,wheat,rye, oats, grasses, sorghums, legume inoculants

Agassiz Seed & Supply445 7th St.NWWest Fargo,ND 58078701-282-8118fax 701-282-9119www.agassizseed.comsorghum, sudangrass,millet, ryegrass, clovers,oats,wheat, vetch, legume inoculants

Agriliance-AFC, LLC.P.O. Box 2207905 Market St.Decatur, AL 35609256-560-2848fax [email protected] grasses,wheat, rye,winter peas, vetch

Albright Seed Company6155 Carpinteria Ave.Carpinteria, CA 93013-3061805-684-0436fax [email protected] in native California summer dormantperennial grasses & wild flowers, handles allseeds used in western cover crops

A.L. Gilbert—Farmers Warehouse4367 Jessup Rd.Ceres, CA 95307800-400-6377209-632-2333jan.bowman@farmerswarehouse.comwww.farmerswarehouse.comforage, grass, clovers, alfalfa, pasture

Ampac Seed Co.P.O. Box 318Tangent,OR 97389800-547-3230fax [email protected]://ampacseed.comforage grasses, legumes, annual ryegrass, turnip,rapeseed

Barenbrug33477 Hwy. 99 EastTangent,OR 97389541-926-5801800-547-4101fax 541-926-9435forage legumes, grasses

The Birkett MillsTransloading FacilityNorth Ave.PennYan,NY 14527315-536-2594custserv@thebirkettmills.comwww.thebirkettmills.combuckwheat

Cache River Valley Seed, LLCHwy. 226 EastCash, AR [email protected], oats

Appendix C

SEED SUPPLIERS


Cal/West SeedsP.O.Box 1428Woodland,CA 95776-1428800-824-8585fax 530-666-5317t.hickman@calwestseeds.comwww.calwestseeds.comclovers, alfalfa, sudangrass, sorghum

Cedar Meadow Farm679 Hilldale Rd.Holtwood PA 17532717-575-6778fax 717-284-5967steve@cedarmeadowfarm.comwww.cedarmeadowfarm.comforage radish, hairy vetch

Discount SeedsP.O.Box 842411 9th Ave SWWatertown, SD 57201605-886-5888fax 605-886-3623grains, forage/grain legumes, forage grasses

DLF OrganicP.O.Box 229175West H St.Halsey,OR [email protected]/white clover, forage peas, organic cover cropmix

Doebler’s Pennsylvania Hybrids, Inc.202TiadaghtonAve.Jersey Shore, PA 17740800-853-2676570-753-3210fax [email protected], grasses, legume inoculants

Ernst Conservation Seeds9006 Mercer PikeMeadville, PA 16335800-873-3321fax [email protected], clovers, buckwheat, ryegrass, alfalfa, barley,winter peas, rye,wheat, hairy vetch, Japanesemillet, foxtail millet

Fedco SeedsP.O.Box 520Waterville,ME 04903207-873-7333fax 207-872-8317www.fedcoseeds.comgrains, forage/grain legumes, grasses, clovers,legume inoculants

Genesee Union WarehouseP.O.Box 67Genesee, ID 83832208-285-1141fax 208-285-1716www.geneseeunion.coopOriental mustard,winter peas

Harmony Farm Supply & Nursery3244 Hwy. 116 NorthSebastopol, CA 95472707-823-9125fax [email protected], grains, grasses, legumes, legumeinoculants

High Mowing Seeds76 Quarry Rd.Wolcott,VT 05680802-472-6174fax 802-472-3201www.highmowingseeds.combuckwheat, vetch, oats, rye, peas, clover, legumeinoculants

SEED SUPPLIERS 197

Hobbs & Hopkins Ltd.1712 SE Ankeny St.Portland,OR 97214503-239-7518fax 503-230-0391info@protimelawnseed.comwww.protimelawnseed.comgrasses

Horstdale Farm Supply12286 Hollowell Church Rd.Greencastle, PA 17225-9525717-597-5151fax 717-597-5185barley,wheat, rye, oats, crimson clover,wintervetch

Hytest Seeds2827 8th Ave. SouthFort Dodge, IA 50501800-442-7391jrkrenz@landolakes.comwww.hytestseeds.comalfalfa

Johnny’s Selected Seeds955 BentonAve.Winslow,ME 04901877-564-6697fax [email protected], rye, oats,wheat, vetch, clover, fieldpeas, green manure mix, sudangrass, legumeinoculants

Kamprath Seeds, Inc.205 Stockton St.Manteca,CA 95337209-823-6242fax 209-823-2582vetches, bell beans, small grains, brassicas,subterranean clovers, balansa clover,medics,perennial clovers, grasses

Kaufman Seeds, Inc.P.O. Box 398Ashdown,AR 71822870-898-3328800-892-1082fax [email protected] grains, forage/grain legumes, grasses,summer annuals, sunn hemp

Keystone Group Ag. SeedsRR 1 Box 81ALeiser Rd.New Columbia, PA 17856570-538-1170alfalfa, forages, forage radish

King‘s Agriseeds, LLC96 Paradise Ln.Ronks, PA 17572717-687-6224866-687-6224forage radish, forages, alfalfa, clovers

Little Britain AgriSupply Inc.398 North Little Britain Rd.Quarryville, PA [email protected], barley,wheat, rye, triticale, intermediate rye-grass, perennial ryegrass, annual ryegrass, redclover, sorghum & sudangrass (other cover cropsavailable by special order)

Michigan State Seed Solutions717 N.Clinton St.Grand Ledge,MI 48837517-627-2164fsiemon@seedsolutions.comwww.seedsolutions.comforgage/grain legumes, grains, grasses

Missouri Southern Seed Corp.P.O. Box 699Rolla,MO 65402573-364-1336800-844-1336fax 573-364-5963wholesale (w/retail outlets): grains, foragelegumes, grasses, summer annuals


Moore Seed Farm, LLC8636 N.Upton Rd.Elsie,MI 48831989-862-4686rye

North Country OrganicsP.O.Box 372Bradford,VT 05033802-222-4277fax [email protected], ryegrass, oats, rye,wheat

Peaceful Valley Farm & Garden Supply125 Clydesdale Ct.P.O. Box 2209Grass Valley, CA 95945888-784-1722fax [email protected], grasses, legumes, grains, vetches, customcover crop mixes, legume inoculants

Pennington SeedsP.O.Box 290Madison,GA 30650800-285-7333seeds@penningtonseed.comwww.penningtonseed.comgrains, grasses, forage legumes

Plantation Seed Conditioners, Inc.P.O.Box 398Newton,GA 39870229-734-5466fax 229-734-7419lupin, rye, black oats

P.L. Rohrer & Bro. Inc.P.O.Box 250Smoketown, PA 17576717-299-2571fax [email protected], clovers, grasses, brassicas, vetch, rye,wildlife mix

Rupp Seeds, Inc.17919 County Rd. BWauseon,OH 43567877-591-7333fax [email protected], grasses, forage legumes, vetch

Seed Solutions2901 Packers Ave.Madison,WI 53707800-356-7333fax [email protected],wheat, rye, hairy vetch, sweetclover,berseem clover, red clover, crimson clover, foragepeas, cowpeas, ryegrass, buckwheat,millets,sorghum, sorghum-sudangrass, cover crop mixes

Seedway, LLC.P.O.Box 250Hall,NY 14463800-836-3710fax [email protected], orchardgrass, clover

Siemer/Mangelsdorf Seed Co.515West Main St.P.O. Box 580Teutopolis, IL 62401217-857-3171fax [email protected], vetch,wildlife

Southern States Cooperative, Inc.P.O.Box 26234Richmond,VA 23260-6234800-868-6273wholesale (retail outlets in 6 states): grains,forage legumes, cowpeas, summer annuals,rapeseed, clover, buckwheat, rye

SEED SUPPLIERS 199

Sweeney Seed Company110 SouthWashington St.Mount Pleasant,MI 48858989-773-5391grasses, forages, legumes

Talbot Ag SupplyP.O. Box 2252Easton,MD [email protected], barley, rapeseed, rye

Tennessee Farmers Co-op200Waldron Rd.P.O. Box 3003LaVergne,TN [email protected], grains, clover, grasses, legume inoculants

Timeless Seeds, Inc.166 Sunrise Ln.P.O. Box 881Conrad,MT 59425406-278-5722fax [email protected]://timelessfood.comdryland forage/grain legumes

The Wax Co., Inc.212 Front St.N.Amory,MS 38821662-256-3511annual ryegrass, forages

Welter Seed & Honey Co.17724 Hwy. 136Onslow, IA 52321-7549800-728-8450 or 800-470-3325fax [email protected], brassicas, rye, spring wheat,winter wheat,buckwheat, hairy vetch, sweet clovers, alfalfa, awide variety of other seeds, legume inoculants

Wolf River Valley SeedsN2976 County Hwy MWhite Lake,WI 54491800-359-2480fax [email protected], brassicas, grasses, annual forage, grain,legume inoculants

INOCULANT SUPPLIERSMany of the seed suppliers listed above sell inoculated seedand/or legume inoculants.

Agassiz Seed & Supply445 7th St.NWWest Fargo,ND 58078701-282-8118fax 701-282-9119www.agassizseed.com

Becker Underwood801 Dayton Ave.Annes, IA 50010800-232-5907request@beckerunderwood.comwww.beckerunderwood.com

HiStick801 Dayton Ave.Ames, IA 50010800-892-2013www.histick.comclick ‘Where to Buy’ for dealer locations

LiphaTech Inc. (Nitragin division)Manufacturer of Nitragin inoculant.www.nitragin.comclick ‘Recommended Links’ at bottomof page.


This list is for information purposes only. Inclusion does notimply endorsement, nor is criticism implied of organizationsnot mentioned. Note: CC denotes cover crop(s) or cover crop-ping.

ORGANIZATIONS—NORTHEAST

The Accokeek Foundation3400 Bryan Point Rd.Accokeek,MD 20607301-283-2113fax [email protected] stewardship & ecological agricultureusing CC

Chesapeake Wildlife HeritageP.O.Box 1745Easton,MD 21601410-822-5100fax [email protected] in organic & sustainable farming systems;consulting & implementation in mid-shore Mdarea as they relate to farming & wildlife

Pennsylvania Association for SustainableAgriculture (PASA)P.O.Box 419114W.Main St.Millheim, PA 16854814-349-9856fax [email protected] farm CC demonstrations

SARE Northeast Region OfficeUniversity of Vermont10 Hills Bldg.Burlington,VT 05405-0082802-656-0471fax [email protected]/~nesare

ORGANIZATIONS—NORTH CENTRAL

Center for Integrated Agricultural Systems(CIAS)University ofWisconsin-Madison1535 Observatory Dr.Madison,WI 53706608-262-5200fax [email protected] for fresh market vegetable production; rele-vant publication“Grower to grower: Creating alivelihood on a fresh market vegetable farm”available on website.

Conservation Technology InformationCenter (CTIC)1220 Potter Dr.West Lafayette, IN 47906765-494-9555fax 765-494-5969ctic@ctic.purdue.eduwww.conservationinformation.orgCTIC is a trusted, reliable source for information& technology about conservation in agriculture

Appendix D

FARMING ORGANIZATIONS WITH COVER CROPEXPERTISE

ORGANIZATIONS 201

Leopold Center for Sustainable AgricultureIowa State University209 Curtiss HallAmes, IA 50011-1050515-294-3711fax [email protected]/centers/leopoldsupport research, demos, education projects inIowa on CC systems

Northern Plains Sustainable AgricultureSocietyP.O. Box 194, 100 1Ave. SWLamoure,ND 58458-0194701-883-4304fax [email protected] systems for organic/sustainable farmers

SARE North Central Region OfficeUniversity of Minnesota120 Bio.Ag. Eng.1390 Eckles Ave.St. Paul,MN 55108612-626-3113fax [email protected]/ncrsare

ORGANIZATIONS—SOUTH

Appropriate Technology Transfer for RuralAreas (ATTRA)P.O. Box 3657Fayetteville, AR 72702800-346-9140http://attra.ncat.org/ATTRA is a leading information source forfarmers & extension agents thinking aboutsustainable farming practices

Educational Concerns for HungerOrganizationECHO17391 Durrance Rd.North Ft.Myers, FL 33917239-543-3246fax [email protected] technical information & seeds oftropical cover crops;maintains demonstrationplots on the farm of many of the most importanttropical cover crops.

The Kerr Center for SustainableAgriculture Inc.P.O. Box 588Highway 271 SouthPoteau,OK 74953918-647-9123fax [email protected] systems demonstrations & research

SARE Southern Region OfficeUniversity of Georgia1109 Experiment St.Georgia StationGriffin,GA 30223-1797770-412-4786fax [email protected]

Texas Organic Growers AssociationP.O. Box 15211Austin,TX 78761877-326-5175fax [email protected] is helping to make organic agricultureviable inTexas & offers a quarterly periodical.


ORGANIZATIONS—WEST

Center for Agroecology & Sustainable FoodSystemsUniversity of California1156 High St.Santa Cruz,CA 95064831-459-3240fax [email protected]/casfsFacilitates the training of organic farmers& gardeners,with practical hands-on & academictraining

SARE Western Region OfficeUtah State University4865 Old Main HillRoom 322Logan,UT [email protected]://wsare.usu.edu

Small Farm CenterUniversity of CaliforniaOne Shields Ave.Davis, CA 95616530-752-8136fax [email protected] as a clearinghouse for questions fromfarmers,marketers, farm advisors, trade associa-tions, government officials & agencies,& the aca-demic community

University of California SAREPOne Shields Ave.Davis, CA 95616-8716530-752-7556fax [email protected]

Appendix E

REGIONAL EXPERTSThese individuals are willing to briefly respond to specificquestions in their area of expertise, or to provide referral toothers in the sustainable agriculture field. Please respecttheir schedules and limited ability to respond. Note: CCdenotes cover crop(s) or cover cropping.

NORTHEAST

Andy ClarkSustainable Agriculture Network10300 Baltimore Ave., Bldg. 046Beltsville,MD 20705301-504-6425fax [email protected] information specialist for sustainableagriculture; legume/grass CC mixtures

Jim CrawfordNew Morning Farm22263Anderson Hollow Rd.Hustontown, PA 17229814-448-3904fax [email protected] years of CC for vegetable production

A. Morris Decker5102 Paducah Rd.College Park,MD [email protected]. Emeritus,University of Maryland40 years forage mgt., CC & agronomic croppingsystems research

REGIONAL EXPERTS 203

Eric GallandtWeed Ecology & ManagementDept. of Plant, Soil & Environmental SciencesUniversity of Maine5722 Deering HallOrono,ME [email protected]/weedecology/CC & weed management

Steve GroffCedar Meadow Farm679 Hilldale Rd.Holtwood, PA 17532717-284-5152fax [email protected]/no-till strategies for vegetable & agronomic crops

Vern GrubingerUniversity of Vermont Extension11 UniversityWayBrattleboro,VT 05301-3669802-257-7967 ext. [email protected]/vtvegandberry/Videos/covercropvideo.htmlvegetable & berry specialist

H.G. Haskell III4317 S.Creek Rd.Chadds Ford, PA 19317tel/fax 610-388-0656cell [email protected]/vetch mix for green manure & erosioncontrol;uses winter rye CC on all land;70% no-till

Zane R. HelselRutgers Cooperative Extension88 Lipman Dr.313 Martin HallNew Brunswick,NJ 08901-8525732-932-5000 x585fax [email protected] in field crops

Stephen HerbertUniversity of MassachusettsDept. of Plant Soil Insect SciencesBowditch HallAmherst,MA 01003413-545-2250fax [email protected]/cdlCC culture, soil fertility, crop nutrition & manage-ment & nitrate leaching

Jeff MoyerThe Rodale Institute611 Siegfriedale Rd.Kutztown, PA 19530610-683-1420fax [email protected] management in biologically based no-tillsystems,CC in grain crop rotations, CC as aweed management tool, rolling CC

Jack MeisingerUSDA/ARSBARC-EastBldg. 163F Rm 610300 Baltimore AveBeltsville,MD [email protected] management in CC systems

Anne & Eric Nordell3410 Rte. 184Trout Run, PA 17771570-634-3197rotational CC for weed control

Marianne SarrantonioUniversity of MaineDept. of Plant, Soil & Environmental Science5722 Deering HallOrono,ME 04473207-581-2913fax [email protected] of CC on nutrient cycling & soil qualityin diverse cropping systems


Eric SidemanMaine Organic Farmers & Gardeners Assoc.P.O. Box 1760Unity,ME 04988207-946-4402fax [email protected] in rotation with vegetables & small fruit onorganic farms

John R. TeasdaleUSDA/ARSBARC-WestBldg. 001 Rm 24510300 Baltimore AveBeltsville,MD 20705301-504-5504fax [email protected] mgmt./weed mgmt. using CC

Donald WeberResearch EntomologistInsect Biocontrol Laboratory10300 Baltimore Ave.Bldg. 011A,Rm. 107BARC-WestBeltsville,MD 20705301-504-8369fax [email protected] & pest management (vegetable crops only)

David W. WolfeCornell UniversityDept. of Horticulture168 Plant Science Bldg.Ithaca,NY 14853607-255-7888fax [email protected]/wolfeCC for improved soil quality in vegetables

NORTH-CENTRAL

Rich Bennett13 Lakeview Dr.Napoleon,OH [email protected] for soil quality & herbicide/pesticide reduction

John CardinaOhio State UniversityDept. of Horticulture & Crop Science1680 Madison Ave.Wooster,OH 44691330-263-3644fax [email protected] for no-till corn & soybeans

Stephan A. EbelharUniversity of Illinois,Dept. of Crop SciencesDixon Springs Agricultural CenterRte. 1, Box 256Simpson, IL 62985618-695-2790fax [email protected]/research/rdc/dixon-springsCC for no-till corn & soybeans

Rick (Derrick N.) Exner, Ph.D.Iowa State University ExtensionPractical Farmers of Iowa2104Agronomy Hall, ISUAmes, IA 50011515-294-5486fax [email protected] farm CC research for the upper Midwest


Carmen M. Fernholz2484 Hwy 40Madison,MN 56256320-598-3010fax [email protected] tillage, general cover crops, seedingsoybeans into standing rye

Walter GoldsteinMichael Fields Agricultural InstituteP.O. Box 990East Troy,WI 53120262-642-3303 ext. 112fax 262-642-4028wgoldstein@michaelfieldsaginst.orgwww.michaelfieldsaginst.orgCC for nutrient cycling & soil health inbiodynamic, organic & conventional systems

Frederick Kirschenmann3703WoodlandAmes, IA 50014515-294-3711fax [email protected] for cereal grains, soil quality & pest mgt.

Matt LiebmanIowa State UniversityDept. of Agronomy3405Agronomy HallAmes, IA 50011-1010515-294-7486fax [email protected]/personnel/userspage.aspx?id=646CC for cropping system diversification, soilamendments,weed ecology & management,crop rotation, green manures, intercrops, animalmanures, composts, insects & rodents thatconsume weed seeds

Todd MartinMSU Kellogg Biological StationLand &Water Program3700 E.Gull Lake Dr.Hickory Corners,MI 49060269-671-2412 ext. 226fax [email protected] for corn, soybeans, vegetables, blueberries inMichigan

Paul Mugge6190 470th St.Sutherland, IA [email protected] farmer using CC for corn & soybeans

Dale R. MutchMSU Kellogg Biological StationLand &Water Program3700 E.Gull Lake Dr.Hickory Corners,MI 49060269-671-2412 ext. 224800-521-2619fax [email protected] CC information provider

Rob MyersThomas Jefferson Agricultural Institute601West Nifong Blvd, Ste. 1DColumbia,MO 65203573-449-3518fax 573-449-2398rmyers@jeffersoninstitute.orgwww.jeffersoninstitute.orgCC & crop diversification


Sieg SnappW.K.Kellogg Biological StationMichigan State University3700 East Gull Lake Dr.Hickory Corners,MI 49060fax [email protected]/faculty/snappusing CC to enhance nitrogen fertilizer use effi-ciency & nutrient cycling in row crops

Richard ThompsonThompson On-Farm Research2035 190th St.Boone, IA [email protected] in corn-soybean-corn-oats-hay rotation

SOUTH

Philip J. BauerUSDA/ARSCotton Production Research Center2611West Lucas St.Florence, SC 29501-1241843-669-5203 x137fax [email protected] for cotton production

J.P. (Jim) Bostick, Ph.D.Southern Seed Certification Assoc.P.O. Box 357Headland, AL 36345334-693-3988fax [email protected] CC & seed development

Nancy CreamerNorth Carolina State UniversityCenter for Environmental Farming SystemsBox 7609Raleigh,NC 27695919-515-9447fax [email protected] management for no-till organic vegetableproduction

Seth DabneyUSDA-ARSNational Sedimentation LaboratoryP.O. Box 1157598 McElroy DriveOxford,MS 38655662-232-2975fax [email protected] reseeding & mechanical control of CCin the mid-South

Greg D. HoytDept. of Soil Science,NCSUMtn.Hort. Crops Res.& Ext. Center455 Research Dr.Fletcher,NC 28732828-684-3562fax [email protected] for vegetables, tobacco & corn

D. Wayne ReevesResearch LeaderUSDA/ARSJ. Phil Campbell Sr.Natural ResourceConservation Center1420 Experiment Station Rd.Watkinsville,GA 30677706-769-5631 ext. 203cell 706-296-9396fax [email protected] management & conservation tillage forsoybean, corn, cotton, peanut,& integratedgrazing-row crop systems


Kenneth H. QuesenberryUniversity of FloridaP.O. Box 110500Gainesville, FL 32611352-392-1811 ex. 213fax [email protected] legume CC in S.E.USA

Jac VarcoMississippi State UniversityPlant & Soil Sciences Dept.Box 9555Dorman Hall, Room 117Mississippi State,MS 39762662-325-2737fax [email protected] & fertilizer/nutrient management for cottonproduction

WEST

Miguel A. AltieriUniversity of California at Berkeley215 Mulford HallBerkeley,CA 94720-3112510-642-9802fax [email protected]://nature.berkeley.edu/~agroeco3CC to enhance biological pest control inperennial systems

Robert L. Bugg, Ph.DU.C. Sustainable Agriculture Research &Education ProgramUniversity of California at DavisOne Shields Ave.Davis, CA 95616-8716530-754-8549fax [email protected] selection, growth & IPM

Jorge A. DelgadoSoil ScientistSoil Plant Nutrient Research UnitUSDA/ARS2150 Centre Avenue, Building D, Suite 100Fort Collins, CO [email protected];[email protected] in irrigated potato, vegetables and small grainsystems

Richard P. DickProfessor of Soil Microbial EcologyOhio State UniversitySchool of Environment & Natural ResourcesColumbus,OH 43210614-247-7605fax [email protected] cycling & environmental applicationsof CC

Shiou KuoWashington State UniversityDept. of Crop & Soil Sciences7612 PioneerWay EastPuyallup,WA 98371-4998253-445-4573fax [email protected] & soil nitrogen accumulation & availability tocorn

John M. LunaOregon State UniversityDept. of Horticulture4107Agricultural & Life Sciences Bldg.Corvallis,OR 97331541-737-5430fax [email protected] for integrated vegetable production &agroecology


Dwain MeyerNorth Dakota State UniversityLoftsgard Hall, Room 470EExtension ServiceFargo,ND [email protected] blossom sweetclover specialist

Clara I. NichollsUniversity of CaliforniaDept. of Environmental Science Policy &ManagementDivision of Insect Ecology137 Hilgard HallBerkeley,CA 94720510-642-9802fax [email protected] for biological control in vineyards

Fred ThomasCERUS Consulting2119 ShoshoneAve.Chico,CA 95926530-891-6958fax [email protected] specialist for tree & vine crops, row crops,field crops, vegetable crops & summer CC

The publications cited in the text (in parentheses) are listedhere by reference number.

1Abdul-Baki, A.A. et al. 1997. Broccoli produc-tion in forage soybean and foxtail millet covercrop mulches.HortSci. 32:836-839.

2Abdul-Baki, A.A.and J.R.Teasdale.1993. Ano-tillage tomato production system using hairyvetch and subterranean clover mulches.HortSci.28:106-108.

3 Abdul-Baki, A.A. and J.R.Teasdale. 1997. Snapbean production in conventional tillage and inno-till hairy vetch mulch.HortSci. 32:1191-1193.

4 Abdul-Baki, A.A. and J.R.Teasdale. 1997.Sustainable Production of Fresh-MarketTomatoes and Other SummerVegetables withOrganic Mulches. Farmers’ Bulletin No. 2279,USDA/ARS, Beltsville,Md. 23 pp.www.ars.usda.gov/is/np/tomatoes.html

5 Alabouvette, C., C.Olivain and C. Steinberg.2006. Biological control of plant diseases: theEuropean situation.European J. of Plant Path.114:329-341.

6 Alger, J. 2006. Personal communication.Stanford,Mont.

7 Al-Sheikh, A. et al. 2005. Effects of potato-grainrotations on soil erosion, carbon dynamics andproperties of rangeland sandy soils. J. Soil TillageRes. 81:227-238.

8 American Forage and Grassland CouncilNational Fact Sheet Series. Subterranean clover.http://forages.orst.edu/main.cfm?PageID=33

9Angers,D.A. 1992.Changes in soil aggregationand organic carbon under corn and alfalfa. SoilSci. Soc.Am. J. 56:1244-1249.

Appendix F

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INDEX 233INDEX 233

AAgroecosystem, 25Alfalfa, 10, 42, 110, 118, 119,124, 137

Allelopathyberseem clover, 122black oats, 192brassicas, 82buckwheat, 91conservation tillage and,49–50

cowpeas, 126oats, 94, 95rye, 32, 99, 103sorghum-sudangrass hybrids,107

subterranean clover, 168sweetclover, 176woollypod vetch, 186, 188

Alsike clover, 163Annual Ryegrass. See Ryegrass, annual

Annuals. See specific cropsAtrazine, 121, 161Austrian winter peas. See Field Peas

Avena sativa. See OatsAvena strigosa. See Oats, black

BBacteria. See DiseasesBalkcom, Kipling, 58Barleyadvantages of, 32, 71benefits of, 78comparative notes, 80cultivars, 80cultural traits, 69disadvantages of, 72killing and controlling, 80management of, 78–80overview of, 77–78performance and roles,67–68, 77

planting of, 70, 78–80in rotation, 42

Barrel medic. See MedicsBees, 131, 136, 173, 181Biennials. See specific cropsBiofumigation, 39, 86Biological farming, 96Biomass. See also Organic matter; Residuebalansa clover, 192barley, 78, 79berseem clover, 119, 120, 124black oats, 192brassicas, 81buckwheat, 93cereal grains, 73in conservation tillage, 45cowpeas, 125crimson clover, 130–31field peas, 135–36medics, 157mustards, 84oats, 93, 94red clover, 160, 161rye, 99sorghum-sudangrass hybrids,13, 106

sunnhemp, 194sweetclover, 13, 172, 177winter wheat, 115

Birdsfoot trefoil, 163Black medic. See MedicsBlack oats. See Oats, blackBlackeye peas. See CowpeasBlando brome, 14Blueberries, 182–83Brassica hirta. See MustardsBrassica juncea. See MustardsBrassica napus. See RapeseedBrassica rapa. See RapeseedBrassicas. See also Mustards;Radishes; Rapeseedbenefits of, 82–84carbon content, 73

comparative notes, 89–90in dairy, 14management of, 87–89nematicides for, 83overview of, 81planting of, 87–88, 89precautions, 89in rotation, 10, 37soil erosion protection, 11species of, 84–85turnips, 85as vegetable greens, 85

Bromegrass mosaic virus, 76Buckwheatadvantages of, 19, 31, 32, 71benefits of, 90–91comparative notes, 93cultural traits, 69disadvantages of, 72management of, 91–92overseeding, 13overview of, 90performance and roles,67–68

planting of, 70, 91–92in rotation, 39–40, 42

Burclover. See MedicsBurr medic. See Medics

CCalcium, 19, 91California. See alsoWest, 61Canadian field peas. See Field Peas

Canola. See RapeseedCarbon, 73, 116, 140, 143, 144Cash cropsbrassicas, 85–86in conservation tillage, 55–56cover crops and, 11, 34–43establishing in conservationsystem, 55–56

overseeding, 13rapeseed, 177

INDEX


in rotation, 15, 26–27, 34–43winter wheat, 112

Cereal grains. See Small grains,specific crops

Cereal rye. See RyeChlorsulfuron, 76Choppers/chopping. See also Rolling stalk chopper, 108, 121, 145

Clover, alsike, 163Clover, balansa, 170, 191–92Clover, berseemadvantages of, 71benefits of, 118–19comparative notes, 124cultural traits, 69disadvantages of, 72management of, 119–24overview of, 118performance and roles,67–68

planting of, 70, 119–20in rotation, 36–37, 123–24

Clover, crimsonadvantages of, 26, 30, 71benefits of, 130–31comparative notes, 134cultivars, 133cultural traits, 69disadvantages of, 72in orchards, 14overseeding, 12overview of, 130for pasture and hay, 134performance and roles,67–68

planting of, 70, 131–33in rotation, 35, 36, 41soil erosion protection, 11winter cover, 15

Clover, redadvantages of, 71benefits of, 159–61comparative notes, 163–64cultivars, 160–61, 164cultural traits, 69disadvantages of, 72

for fertilizer reduction, 9–10management of, 161–63overseeding, 12overview of, 159performance and roles,67–68

planting of, 70, 161in rotation, 36–37, 160,162–63

Clover, rose, 14Clover, subterraneanadvantages of, 26, 31, 71benefits of, 165–66comparative notes, 170cultivars, 165, 170cultural traits, 69disadvantages of, 72management of, 166–70in orchards, 14overview of, 164–65performance and roles,67–68

planting of, 70, 166–67reseeding, 13in rotation, 41

Clover, whiteadvantages of, 71benefits of, 179–80comparative notes, 184cultivars, 179cultural traits, 69disadvantages of, 72living mulch, 13in orchards, 14overseeding, 12overview of, 179performance and roles,67–68

planting of, 70, 180–81in rotation, 37

Collins, Hal, 60–61Companion crop. See also Nurse cropberseem clover, 119, 124cowpeas, 126field peas, 138oats, 95

red clover, 160rye, 99white clover, 180

Conservation tillage. SeeTillage, conservation

Corn belt. See MidwestCorn cropping systemsberseem clover, 123–24brassicas, 83, 85, 88in conservation tillage, 55crimson clover, 132–33field peas, 141hairy vetch, 142–43, 145medics, 156oats-rye, 96, 103red clover, 159, 160, 161, 162in rotation, 9, 10, 142with soybeans, 34–37, 41, 44,53, 96, 112

subterranean clover, 165–66,169, 170

white clover, 183winter wheat, 112

Costsin corn rotation, 162cover crops, 9, 50fertilizer cost reduction, 9–10lupins, 193medics, 156pesticides, 10, 27red clover, 160reducing, 27seed, 64, 70, 189sorghum-sudangrass hybrids,106

sunnhemp, 194Cottonin conservation tillage, 55in no-till system, 149–50rotations for, 40–42soil erosion protection, 11and soybeans, 126

Cover crops. See also specific cropsadvantages of, 64–65, 71benefits of, 9–11, 16, 57, 58,59, 60, 61

INDEX 235

comparative notes, 77, 80, 93,105

for cotton, 40–42cultural traits, 63–64, 69disadvantages of, 65, 72drawbacks, 57, 58, 59, 60, 61economics of, 50for grain and oilseed, 34–36legumes, 116management of, 57, 58–59,59, 60, 61

nonlegumes, 46, 73–74performance and roles,62–63, 67

for pest management, 25–33planting of, 13, 64, 70promising species, 191–92regional species, 62, 66rotation of, 15, 96selecting, 12–15, 57, 58, 59,60, 61

soil erosion and, 11, 16summer covers, 13, 15sweetclover, 45–48testing on farm, 189–91for vegetables, 37–40winter covers, 12–13, 15

Cowpeasadvantages of, 71benefits of, 125–27comparative notes, 129cultivars, 126–27cultural traits, 69disadvantages of, 72management of, 127–29in mixtures, 108overseeding, 13, 15overview of, 125performance and roles,67–68

planting of, 70, 126, 127in rotation, 40, 41

Crop rotations. See also Crop systemsberseem clover, 123–24buckwheat, 92cash crops, 15, 26–27, 34–43in conservation tillage, 45

corn, 9, 10, 142corn-soybean, 34–37, 41, 44,53, 96, 112

crimson clover, 132–33mustards, 83planning, 12–15potato/wheat, 86–87reducing pesticides and her-bicides, 10, 24

rye in, 99sorghum-sudangrass hybrids,107

soybeans, 10, 96, 108winter wheat, 112

Crop systems. See also Crop rotationsberseem clover, 123–24in conservation systems, 45cowpeas, 129crimson clover, 132–33field peas, 138–41hairy vetch, 142–43, 144,149–50

nematodes and, 31–32sorghum-sudangrass hybrids,109–11

subterranean clover, 169sweetclover, 177–78white clover, 181–84

Crotolaria juncea. See Sunnhemp

Crowder peas. See Cowpeas

DDairy farming, 14Damping off, 30, 129Delgado, Jorge, 59Denitrification, 94Diseasesannual ryegrass, 76balansa clover, 192barley, 80berseem clover, 122–23brassicas, 82in conservation tillage, 49cover crops and, 10, 29–31crimson clover, 133field peas, 138

lupins, 193medics, 157oats, 97red clover, 163rye, 99, 104sorghum-sudangrass hybrids,107

subterranean clover, 166, 168white clover, 181winter wheat, 115woollypod vetch, 188

Disking. SeeTillageDrought. See Soil moistureDry matter. See ResidueDryland productioncereal-legume crop rotations,42–43

field peas, 136, 138medics, 153Pacific Northwest, 60–61and soil moisture, 48sweetclover, 176

Duiker, Sjoerd, 57–58Dutch white clover. See Clover, white

EEberlein, Charlotte, 114Egyptian clover. See Clover, berseem

Erosion. See Soil erosionExperts, regional, 202–8

FFagopyrum esculentum. See Buckwheat

Fallowcover crops for, 12–13, 37field peas, 138medics and, 153sweetclover, 175–76, 177Farm systems, regionalCalifornia, 61Midwest, 57Northeast, 58Northern Plains, 59Pacific Northwest, 60


Southeast, 58Southern Plains, 59

Farmer accountsAbdul-Baki, Aref-hairy vetchas mulch, 150

Alger, Jess-perennial medicfor soil quality, fertility, 153

Anderson, Glenn-woollypodvetch as frost protectantand recognizing seedlings,186

Anderson, Glenn-woollypodvetch reseeding, 187–88

Bartolucci, Ron-establishingwoollypod vetch, 186

Bennett, Rich-frostseedingred clover, 162–63

Bennett, Rich-rye for weedmanagement in soybeans,104

Beste, Ed-subterranean cloverwith corn, 170

Brubaker, John-crop rollersfor no-till, 146

Brutlag, Alan-lightly seedingbarley, 79–80

Burkett, Ben-winter peas fordisease suppression, 138

Carter, Max-wheat production, 113

Davis, Bryan and Donna-oatsand rye in corn/bean rotation, 96, 103

de Wilde, Rich-killing rye, 101de Wilde, Rich-rye for mulch,103

de Wilde, Rich-spring seedingrye, 100

Dunsmoor, Dan-sorghumsudangrass nematicidaleffect, 109

Erisman, Jack-timing rye kill,101

French, Jim-cowpeas in rotation, 128

French, Jim-field peas, 140

Farmer accountsGies, Dale-potato/wheat rotation, 86–87

Granzow, Bill-sweetcloversfor grazing and greenmanure, 174

Groff, Steve-incorporating ryeseed, 100

Groff, Steve-killing rye, 101Groff, Steve-no-till vegetabletransplanting, 103

Kirschenmann, Fred-sweet-clover with nurse crops,177

LaRocca, Phil-barley in vineyard mix, 79

Lazor, Jack-barley in mixtures, 79

Maddox, Erol-rye, 105Martin, Barry-managing rye,102–3

Matthews, Alan-white cloverin contour strips, 181

Mazour, Rich-managingsweetclover escapes, 178

Moyer, Jeff-crop rollers forno-till, 146–48

Nordell, Eric and Anne-covercrops for weeds, 38–39

Nordell, Eric and Anne-earlyseeding sweetclover, 178

Phatak, Sharad-cover cropsfor pest related benefits,30–31

Phatak, Sharad-cover crops tocontrol pests in cotton,peanuts, 26–27

Podoll, David-sweetcloverweevil cycle, 176

Quigley, Ed-managing rye,103

Quigley, Ed-seeding aftercorn harvest, 35

Rant, Richard-clover in blueberries, 182–83

Sheridan, Pat-managing rye,102

Farmer accountsSheridan, Pat-No-till farming,52–53

Stevens, Will-wheat as wintercover, 115

Thompson, Dick and Sharon-hairy vetch andnematodes, 32

Farming organizations, 200–202Fava beans, 78Fernholz, Carmen, 97Fertilizerand cover crops, 46for fallow systems, 139red clover, 161, 162, 163reducing, 9–10, 53subterranean clover, 169

Fescue, 13, 107, 144Field Peasadvantages of, 71benefits of, 135–37comparative notes, 141cultural traits, 69disadvantages of, 72for fertilizer reduction, 10management of, 137–41overview of, 135performance and roles,67–68

planting of, 70, 136, 137–41in rotation, 42winter cover, 15

Forageannual ryegrass, 75barley, 80berseem clover, 119field peas, 136, 137grasses, 73medics, 155, 156mixed seedings in, 117rapeseed, 84red clover, 163rye, 105sorghum-sudangrass hybrids,107

sweetclover, 173, 178

INDEX 237

white clover, 180winter wheat, 115woollypod vetch, 188

Freedom to Farm Act, 128Frostseeding, 161, 162, 175, 180Fruits. See also Orchards;Vineyards, 99, 182–83

GGlomalin, 19Glycine max, 108Glyphosatemedics and, 153rapeseed and, 88ryegrass and, 76sorghum-sudangrass hybridsand, 107

subterranean clover and, 170Grassescarbon content, 73forage, 73mixed seedings using, 117for moisture conservation, 11in orchards, 14

Grazingannual ryegrass, 75, 76berseem clover, 119crimson clover, 134field peas, 140hairy vetch, 150livestock poisoning, 89, 107,172, 194

medics, 153, 155, 156oats, 97red clover, 161, 163rye, 105sorghum-sudangrass hybrids,107

subterranean clover, 166, 168sweetclover, 173, 175, 176winter wheat, 115

Great Lakes, 66Green manuresberseem clover, 118–19, 120brassicas, 82, 83, 86–87cowpeas, 126, 127field peas, 136, 139nitrogen and, 21, 23–24

oats, 94, 95red clover, 159subterranean clover, 165sweetclover, 172, 174

HHairpinning, 53, 56Hayannual ryegrass, 77, 80berseem clover, 119cowpeas, 126crimson clover, 134medics, 157oats, 97sorghum-sudangrass hybrids,111

sweetclover, 173Health and safety issues, 11Herbicides. See also Killing andcontrollingatrazine, 121, 161glyphosate, 76, 88, 107, 153,170

paraquat, 88, 107, 170reducing, 10sethoxydim, 107

Hordeum vulgare. See BarleyHubam. See SweetcloversHumus. See Organic matterHyphae, 19

IInoculantsfor balansa clover, 191for cover crops, 70for cowpeas, 127for legumes, 20, 122–23, 189for white clover, 181

Insecticides, 154Insectsannual ryegrass, 76barley, 78berseem clover, 122–23brassicas, 82, 89buckwheat, 91, 92in conservation tillage, 48–49cover crops and, 10, 25–28cowpeas, 126, 127–29

crimson clover, 133–34hairy vetch, 149medics, 154, 157oats, 95predators, 25–29, 80, 149,166, 188

rye, 99, 103–4sorghum-sudangrass hybrids,109

subterranean clover, 166suppression of, 78sweetclover, 38–39, 176white clover, 181winter wheat, 115

woollypod vetch, 188Integrated Pest Management(IPM), 28, 104, 138

Interseeding. See also Seeding/Seedsberseem clover, 120cover crops and, 36hairy vetch, 144subterranean clover, 169sweetclover, 177Irrigationbarley, 79for overseeding, 12potato/wheat, 114subterranean clover, 168woollypod vetch, 187

Italian ryegrass. See Ryegrass, annual

KKaspar, Tom, 57Killing and controlling. See also Herbicidesbarley, 80berseem clover, 121brassicas, 83, 88–89buckwheat, 92in conservation tillage, 51,53–55

cowpeas, 127crimson clover, 132, 133field peas, 138hairy vetch, 145, 148medics, 156


oats, 95red clover, 162roller-crimpers, 54rye, 35, 100–101, 102ryegrass, 76sorghum-sudangrass hybrids,108

subterranean clover, 167sweetclover, 175–76white clover, 181winter wheat, 115

Ladino clover. See Clover, whiteLana vetch. SeeVetch, woollypod

Leaching. See also Nitrogen, 11,18–19, 24, 45, 94, 100

Legumes. See also specific cropsin conservation tillage, 47grass mixtures and, 47lentils, 11, 139moisture conservation, 11nitrogen and, 9, 47, 94nodulation, 122–23in orchards, 14overview of, 116in rotation, 9, 42–43, 139and rye mixtures, 40–41, 99,101, 103

soil erosion protection, 11Lentils, 11, 139Ley cropping subterraneanclover, 155

Living mulchesadvantages of, 13in conservation tillage, 55perennial ryegrass, 13rodents and, 76turfgrasses, 13for weed management, 33white clover, 180, 181

Lolium multiflorum. See Ryegrass, annual

Louisiana S-1 clover. See Clover, white

Lupin albus L.. See Lupins

Lupins, 19, 193Lupinus angustifolium L..See Lupins

MMalting barley, 10Mammoth clover. See Clover, red

Maura, Clarence, 194McGuire, Andy, 86, 87Medicago. See MedicsMedicago arabica, 154Medicsadvantages of, 71benefits of, 152–55comparative notes, 157–58cultivars, 158–59cultural traits, 69disadvantages of, 72management of, 155–57for moisture conservation, 11in orchards, 14overview of, 152–53performance and roles,67–68

planting of, 70, 155–56in rotation, 42, 156–57

Medium red clover. See Clover, red

Melilotus officinalis. See Sweetclovers

Meloidogyne hapla. See Nematodes

Meloidogyne javanica. See Nematodes

Microorganisms. See alsoBiomass; Organic matter;Residue, 17, 21, 31

Mid-Atlanticcover crops for, 66crimson clover, 132field peas, 138, 141hairy vetch, 143rye, 101weed problems, 75

Midwestberseem clover, 120buckwheat, 92cover crops for, 34–37, 41,57, 66

cowpeas, 129hairy vetch, 145medics, 155, 157oats, 94rye, 100, 101strip tillage, 56sweetclover, 172, 173weed problems, 75

Millet, 13, 163Mishanec, John, 108Mitchell, Jeffrey, 61Mixed seeding/Mixturesadvantages/disadvantages of,117–18

annual ryegrass, 76barley, 78, 79berseem clover, 120brassicas, 88cowpeas, 108crimson clover, 131, 133grass/legume, 47hairy vetch, 99, 144oats, 94red clover, 160rye, 99, 100, 101rye/legume, 40–41, 99, 101,103

sorghum-sudangrass hybrids,108

subterranean clover, 165, 169winter wheat, 114–15

Mowers/mowingbarley, 79berseem clover, 120–21brassicas, 88in conservation tillage, 55cowpeas, 127–28crimson clover, 133fescue, 144flail, 108, 120, 145hairy vetch, 145

INDEX 239

medics, 155red clover, 163sicklebar, 108, 126, 148sorghum-sudangrass hybrids,108

subterranean clover, 168, 169sweetclover, 175–76white clover, 181, 181–82woollypod vetch, 187–88

Mulch. See Living mulches;Winterkilled mulches

Mustards. See also Brassicasadvantages of, 32, 71barley and, 80cultural traits, 69disadvantages of, 72overview of, 84–85performance and roles,67–68

planting of, 70in rotation, 37weeds in, 84

Mutch, Dale, 183Mycorrhizae, 19, 172

NNatural ResourcesConservation Service, 16

Nematodesbalansa clover, 192barley, 80berseem clover, 123black oats, 192brassicas, 82–83, 86–87in conservation tillage, 49cover crops and, 10, 31–32cowpeas, 129crimson clover, 133hairy vetch, 149nematicides use, 83oats, 97pin, 76rye, 99sorghum-sudangrass hybrids,107, 109

subterranean clover, 168–69sunnhemp, 194sweetclover, 176

New Zealand white clover. See Clover, white

Nitrogenannual ryegrass, 75, 77balansa clover, 192barley, 78berseem clover, 118–19, 121black oats, 192brassicas, 81–82, 89cover crops, 9, 11, 18–24, 34,36–41, 42, 45–47

cowpeas, 126crimson clover, 130, 131in dryland systems, 43estimating need for, 22–23field peas, 136, 140–41fixation and release, 20–21, 35

hairy vetch, 142–43, 145immobilization and mineralization, 46, 47

legumes, 19, 20–21medics, 153–54mixed seedings and, 117mustards, 84nodulation, 122–23nonlegumes, 19, 73–74oats, 93–94red clover, 159–60, 161, 162rye, 98, 100, 101sorghum-sudangrass hybrids,109

subterranean clover, 168sunnhemp, 194sweetclover, 38–39, 172, 176white clover, 179–80winter wheat, 112, 113woollypod vetch, 185–86

Nodulation, 122–23Nonlegumes, 19, 46, 73–74Northeastbrassicas, 82buckwheat, 92cover crops for, 57–58, 66crimson clover, 132field peas, 135hairy vetch, 142, 144oats, 94

rye, 100sorghum-sudangrass hybrids,107, 108, 110

Northeast Organic Network, 39Northern Plainsberseem clover, 121cover crops for, 59, 66crimson clover, 132field peas, 135, 137, 138–39grain cropping systems, 42medics, 152–53subterranean clover, 170sweetclover, 171, 173,175–77

Northwest. See PacificNorthwest

No-till. See alsoTillagebarley, 78buckwheat, 92and conservation tillage, 56corn, 9, 35, 83, 142–43, 145,156

cotton, 11, 149–50cowpeas, 127crimson clover, 132farming, 52–53hairy vetch, 149–50nitrogen and, 24oats, 95, 96roller use, 146–48rye, 96, 99, 105soybeans, 104vegetable transplanting, 103,148

Nurse crop. See also Companion cropannual ryegrass, 75barley, 80berseem clover, 119buckwheat, 91, 92medics, 156oats, 94rapeseed, 177winter wheat, 114–15

Nutrients. See also Nitrogen;Phosphorus; Potassium,18–24, 45–47


OOatsadvantages of, 71benefits of, 93–94comparative notes, 97cultural traits, 69disadvantages of, 72management of, 94–97overview of, 93performance and roles,67–68

planting of, 70, 94–95, 96in rotation, 9, 37, 40

Oats, black, 46, 97, 192–93Orchards. See also Fruits;Vineyardsannual ryegrass, 74barley, 78cover crops and, 14medics, 154rye, 99subterranean clover, 164,165, 167, 169

woollypod vetch, 185, 186Organic matter. See also Biomass; Residuecover crops and, 96medics, 154–55overview of, 17rye, 99winter wheat, 112woollypod vetch, 186

Overseeding. See also Seeding/Seedsannual ryegrass, 12, 76barley, 79berseem clover, 120in crop rotation, 12field peas, 141hairy vetch, 12, 144medics, 156, 157millet, 13oats, 94red clover, 161rye, 12, 98, 100

small grains, 13sorghum-sudangrass hybrids, 13

sweetclover, 177white clover, 180

PPacific Northwestbrassicas, 80, 82cover crops for, 60–61, 66erosion control, 78

Paradana clover. See Clover, balansa

Paraquat, 88, 107, 170Paratylenchus projectus. See Nematodes

Perennials. See specific cropsPests. See Diseases; Insects;Weeds

Phosphorusbrassicas, 89buckwheat, 91cover crops, 19–20crimson clover, 131hairy vetch, 144oats, 93–94red clover, 163sweetclover, 172winter wheat, 112

Pisum sativum. See Field PeasPlanting. See Seeding/Seeds,specific crops

Plastic mulch, 150Polysaccharides, 17–18Potassiumcrimson clover, 131hairy vetch, 144oats, 93–94, 97rye, 98sweetclover, 172winter wheat, 112

Potatoes, 81, 82, 83, 84, 86–87, 88

Predators. See InsectsPrussic acid, 96, 111

RRadishes. See also Brassicasadvantages of, 24, 71cultural traits, 69overview of, 85performance and roles,67–68

planting of, 70in rotation, 10, 83Rapeseed. See also Brassicasadvantages of, 71cultural traits, 69disadvantages of, 72overview of, 84performance and roles,67–68

planting of, 70Reseedingbalansa clover, 191, 192barley, 79crimson clover, 133, 183medics, 155, 156subterranean clover, 168sweetclover, 173white clover, 180woollypod vetch, 187–88

Residue. See also Biomass;Organic matterberseem clover, 122brassicas, 83–84buckwheat, 39–40in conservation tillage, 44–45hairy vetch, 143–44, 145medics, 154–55rye, 99, 101, 103, 104small grains, 36sorghum-sudangrass hybrids,108

subterranean clover, 168sweetclover, 176

Rhizobia, 20Riga, Ekaterini, 83, 87Rodale Institute, 146, 148

INDEX 241

Rolling. See alsoChoppers/chopping; Rollingstalk chopperberseem clover, 121brassicas, 88hairy vetch, 148in no-till system, 146–48roller-crimpers, 54for weed management, 33

Rolling stalk chopper. See alsoChoppers/chopping; Rollingcrimson clover, 133hairy vetch, 145red clover, 162rye, 100, 101for weed management, 33

Roundup. See also Glyphosate, 104

Ryeadvantages of, 18–19, 26, 30,31, 32, 71

benefits of, 98–99comparative notes, 105in conservation tillage, 52–53cultural traits, 69in dairy, 14disadvantages of, 72management of, 99–105moisture conservation and, 11

for mulch, 103, 104overseeding, 12, 35overview of, 98performance and roles,67–68

planting of, 70, 99–100, 102in rotation, 10, 35–36, 37, 96,99

soil improvement and, 10Ryegrass, annualadvantages of, 71, 74–75benefits of, 74–75comparative notes, 77cultivars, 77cultural traits, 69disadvantages of, 72killing and controlling, 76

management of, 75–77in orchards, 14overseeding, 12overview of, 74performance and roles,67–68, 74

planting of, 70, 75–76in rotation, 38, 39–40soil improvement and, 10

Ryegrass, perennial, 13

SSafflower, 40Secale cereale. See RyeSeed suppliers, 195–208Seeding/Seeds. See alsoFrostseeding; Interseeding;Mixed seeding/Mixtures;Overseeding; Reseeding; spe-cific crops; Underseedingannual ryegrass, 70, 75–76balansa clover, 191–92barley, 70, 78–80berseem clover, 70, 119–20black oats, 192brassicas, 87–88, 89buckwheat, 70, 91–92in conservation tillage, 50–51cowpeas, 70, 126, 127crimson clover, 70, 131–33field peas, 70, 136, 137–41hairy vetch, 70, 144, 148–49,151

lupins, 193medics, 155–56oats, 70, 94–95, 96red clover, 161rye, 35, 70, 99–100, 102sorghum-sudangrass hybrids,70, 108

subterranean clover, 166–67sweetclover, 173, 175white clover, 180–81, 184winter wheat, 70, 113–14woollypod vetch, 186–87,188

Sesbania exaltata, 108

Sethoxydim, 107Sinapis alba. See MustardsSmall grainscover crops for, 13in dairy, 14for fertilizer reduction, 10overseeding, 13in rotation, 36soil erosion protection, 11, 36

for weed suppression, 32–33Smith, Gerald Ray, 169Snail medic. See MedicsSnap beans, 88Soil. See also Soil erosion; Soil fertility and tilth; SoilmoistureCalifornia, 61compaction, 18, 24, 110Midwest, 57Northeast, 57–58Northern Plains, 59overview of, 16–18Pacific Northwest, 60Southeast, 58Southern Plains, 59subsoil loosener, 66, 71–72,106–7

temperature, 48, 56Soil erosion. See also Soil;Soil fertility and tilth; Soilmoisture

annual ryegrass, 74barley, 78brassicas, 82in conservation tillage, 45cotton, 11medics, 155prevention, 11, 16rye, 98, 104subterranean clover, 166winter wheat, 112

Soil fertility and tilth. See alsoSoil; Soil erosion; Soil moistureannual ryegrass, 74barley, 78


buckwheat, 91in conservation tillage, 45cover crops, 11, 16–24, 39field peas, 136hairy vetch, 143improving, 10–11, 13red clover, 160rye, 104, 105ryegrass, annual, 74small grains, 36sorghum-sudangrass hybrids,106–7

subterranean clover, 166, 167sweetclover, 172, 176white clover, 180, 182–83winter wheat, 112

Soil moisture. See also Soil; Soilerosion; Soil fertility and tilthcover crops, 11, 24, 35–36,47–48, 96

field peas, 136medics, 155–56nitrogen and, 21oats, 95rye, 101, 104sweetclover, 172, 177, 178

Sorghum-sudangrass hybridsadvantages of, 24, 32, 71benefits of, 106–7comparative notes, 111cultivars, 109, 111cultural traits, 69disadvantages of, 72management of, 108–11moisture conservation and,11

overseeding, 13overview of, 106performance and roles,67–68

planting of, 70, 108in rotation, 37, 40soil improvement and, 10

Sorgoleone, 107Southcover crops for, 66crimson clover, 132

medics, 154strip tillage, 56sweetclover, 171Southeastberseem clover, 120cover crops for, 58–59, 66field peas, 135, 138, 139–40medics, 154

Southern Plainscover crops for, 59–60, 66crimson clover, 132rye, 101weed problems, 75

Southwest, 66Soybeansberseem clover, 123–24brassicas, 85in conservation tillage, 55cotton intercropping, 126crimson clover, 53crop rotation systems, 34–36,41, 44

field pea overseeding, 141hairy vetch overseeding, 53,144

nematodes and, 32red clover, 161–62in rotation, 10, 96, 108rye, 52, 98, 104winter wheat, 53, 112

Strip croppingannual ryegrass, 77berseem clover, 124in cotton, 41cowpeas, 129equipment, 56–57nematodes and, 32rye, 99white clover, 181, 182

Subclover. See Clover, subterranean

Sudax. See Sorghum-sudangrasshybrids

Sudex. See Sorghum-sudangrasshybrids

Sugarbeets, 10, 80Sulfur, 89, 144

Sunnhemp, 108, 127, 193–94Sweetcloversadvantages of, 24, 71benefits of, 172–73comparative notes, 178cultivars, 178cultural traits, 69disadvantages of, 72management of, 173, 175–76

overview of, 171–72performance and roles, 13,67–68

planting of, 70, 173, 175in rotation, 37, 176

TTillage. See also No-tillbrassicas, 84conservation, 27, 29, 30, 42,44–61

effect on organic matter, 18mustards, 84nitrogen and, 21–24sorghum-sudangrass hybrids,108, 109

strip tillage equipment,56–57

white clover, 183Trials on farm, 189–90Trifolium alexandrinum. See Clover, berseem

Trifolium balansae. See Clover, balansa

Trifolium brachycalcycinum.See Clover, subterranean

Trifolium incarnatum. See Clover, crimson

Trifolium michelianum Savi.See Clover, balansa

Trifolium pratense. See Clover, red

Trifolium repens. See Clover, white

Trifolium subterraneum. See Clover, subterranean

Trifolium yanninicum. See Clover, subterranean

INDEX 243

Triticum aestivum. SeeWheat, winter

Turfgrasses, 13Turnips, 85

UUndercutters, 32, 167Underseedingberseem clover, 120, 121cowpeas, 126legumes, 97red clover, 111sweetclover, 112

Undersowing. See Overseeding

VVegetablesannual ryegrass, 74berseem clover, 122, 124brassicas, 81, 85, 86cowpeas, 122crimson clover, 132, 133in crop rotations, 37–42disease management, 29–31establishing in conservationsystem, 57

hairy vetch, 35–36, 37, 148insect management, 25–28mustards for, 84, 86nematode management,31–32

rye for, 99, 103sorghum-sudangrass hybrids,107, 111

subterranean clover, 164,165–66, 168, 169, 170

sunnhemp, 194sweetclover, 177–78weed management, 32–33white clover, 179, 180, 181,182

woollypod vetch, 185Vetch, annual, 14Vetch, cahaba, 26, 31, 41Vetch, common, 40, 139, 188

Vetch, hairyadvantages of, 71benefits of, 142–44comparative notes, 151cultivars, 151cultural traits, 69disadvantages of, 72for fertilizer reduction, 9, 10management of, 144–45,148–49

as mulch, 150overseeding, 12overview of, 142performance and roles,67–68

planting of, 70, 144, 148–49,151

in rotation, 10, 35–36, 37, 41soil erosion protection, 11winter cover, 15

Vetch, purple, 40, 188Vetch, woollypodadvantages of, 71benefits of, 185–86comparative notes, 188cultural traits, 69disadvantages of, 72management of, 186–88overview of, 185performance and roles,67–68

planting of, 70, 186–87in rotation, 40winter cover, 15

Vicia benghalensis. SeeVetch, woollypod

Vicia faba. See Fava beansVicia villosa. SeeVetch, hairyVicia villosa ssp. dasycarpa.SeeVetch, woollypod

Vigna unguiculata. See Cowpeas

Vineyardsannual ryegrass, 74–76barley, 78, 79buckwheat, 92cowpeas, 126

medics, 154sorghum-sudangrass hybrids,111

woollypod vetch, 185, 186,187

WWeedsannual ryegrass, 75barley, 80berseem clover, 119brassicas, 83–84buckwheat, 90–91, 92in conservation tillage, 49–50cover crops and, 10, 15,32–33, 38–39

cowpeas, 125–26hairy vetch, 143medics, 154mustards, 85oats, 94, 95, 97rye, 99, 103, 104sorghum-sudangrass hybrids,107, 108–9

subterranean clover, 165, 169suppression of, 78, 90–91, 95sweetclover, 176, 178white clover, 182winter wheat, 112, 115woollypod vetch, 186, 188

Westbarley, 79berseem clover, 120buckwheat, 92cover crops for, 66cowpeas, 126crimson clover, 132crop rotation systems, 40erosion control, 78field peas, 137hairy vetch, 142medics, 154, 156, 158, 159sorghum-sudangrass hybrids,111

subterranean clover, 164–67woollypod vetch, 185–87

Wheat, winteradvantages of, 30, 71benefits of, 112–13for cash and cover crop, 112cultural traits, 69disadvantages of, 72management of, 113–15moisture conservation and,11

overview of, 111–12performance and roles,67–68

planting of, 70, 113–14in rotation, 10, 36–37, 38,42–43

soil erosion protection, 11White sweetclover. See Sweetclovers

Wild white clover. See Clover, white

Windham, Gary, 192Winter rye. See RyeWinter Wheat. SeeWheat, winter

Winterkill mulchesannual ryegrass, 75buckwheat, 92crimson clover, 130hairy vetch, 144medics, 156, 157oats, 93–94, 95sweetclover, 178

Wolfe, David, 110

YYellow mustard, 110Yellow sweetclover. See Sweetclovers


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1994

if you’re like most farmers, you probably think you’re too busy for cover crops. My advice: Just do it. Discover how cover crops can hold and improve your soil and how they can suppress weeds, deter pests and take up excess nutrients. Feel the satisfaction of beautiful green fields in fall when everything else is dead, and the soil is bare and vulnerable. Cover crops make a big difference on my farm. They can do the same for you.” Richard De Wilde, vegetable grower, Viroqua, Wis.

This is the best book i have ever read. it uses science to explain complex concepts, lays out options for different systems and climates, and allows innovative farmers to digest the information and make their own intelligent decisions. Thank you for the practical advice, acknowledgement of complex tradeoffs, specifics, details and conclusions.” Wolfgang Rougle, Twining Tree Farm, Cottonwood, Cal.

This book will be a great resource for farmers, educators, researchers and anyone who wants basic information and good ideas for how to use cover crops. i am particularly impressed with the way information is supported by personal experiences of farmers and researchers.”John R. Teasdale, research scientist, USDA-ARS, Beltsville, Md.

Managing Cover Crops ProfitablyThird EdiTion

SUSTAINABLEAGRICULTURE NETWORK

10300 Baltimore Ave., Bldg. 046Beltsville, MD 20705www.sare.org

Farmers across the U.S. are using cover crops to smother weeds, deter pests and slow erosion. They find that cover crops help them cut costs and boost profits while improving their soil and protecting natural resources.

This book distills findings from published studies and on-farm experience into a user-friendly reference tool for farmers and agricultural educators. You will find detailed information on how to select cover crops to fit your farm, and how to manage them to reap multiple benefits.

Here is what the experts say…

“

$19.00

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cover crops managing

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