managing cover crops profitably - usda · (san) published managing cover crops profitably in 1992,...

Managing Cover Crops Profitably

A publication of the Sustainable Agriculture Network

with funding by theSustainable Agriculture Research and

Education Program of CSREES,U.S. Department of Agriculture

Sustainable Agriculture NetworkNational Agricultural LibraryBeltsville, MD 20705-2351

SECOND EDITION

HANDBOOKSERIES BOOK 3

SUSTAINABLEAGRICULTURE NETWORK

THE NATIONAL OUTREACH ARM OF USDA-SARE

Copyright © 1998 by the Sustainable Agriculture Network,with funding from the Sustainable Agriculture Research andEducation (SARE) program of the Cooperative State ResearchEducation and Extension Service (CSREES),U.S.Department ofAgriculture. Reprinted in 2000.

SAN, the national outreach partner of the USDA SARE pro-gram, is a consortium of individuals, universities and govern-ment, business and nonprofit organizations dedicated to theexchange of information on sustainable agricultural systems.

For more information about the Sustainable AgricultureNetwork, or about other SAN publications, contact:

Andy ClarkSAN Coordinatorc/o AFSIC, Room 304National Agricultural Library10301 Baltimore AvenueBeltsville, MD 20705-2351PH: 301-504-6425FAX: 301-504-6409 [email protected]

SARE is a competitive grants program. It provides funding forresearch and education projects that promote agriculturalsystems that are profitable, environmentally sound andenhance the viability of rural communities nationwide.

For more information about the SARE program and SAREgrants, contact:

Office of Sustainable Agriculture ProgramsU.S. Department of Agriculture1400 Independence Ave., S.W., Stop 2223Washington, D.C. 20250-2223

Material for this book and its covers was researched written,illustrated,edited and produced for the Sustainable AgricultureNetwork.The book concept, format, and selection of featuredfarmers and content reviewers were developed under theauspices of the Sustainable Agriculture Network.

To order copies of this book, send a check or purchase orderfor $19 plus $3.95 shipping and handling to:

Sustainable Agriculture PublicationsHills Building, Room 10University of VermontBurlington,VT 05405-0082

Call 802-656-0484 to order by credit card. For first book sentoutside of N. America, please add $6. Add $2.50 for eachadditional book. Please include your mailing address andtelephone number.

The Sustainable Agriculture Network Handbook Series previ-ous titles include Book 1: Managing Cover Crops Profitably(1st Edition), edited by the staff of the Rodale Institute; andBook 2: Steel in the Field: A Farmer’s Guide to WeedManagement Tools,1997, edited by Greg Bowman.

Library of Congress Cataloguing-in-Publication Data

Managing cover crops profitably.—2nd ed.p. cm.–(Sustainable Agriculture Network handbook series

bk.3)Includes bibliographical references (p. ) and index.ISBN 1-888626-04-6 (pbk)

1. Cover crops—United States—Handbooks, manuals, etc.I. Sustainable Agriculture Network. II. Series.SB284.3.U6M36 1998631.5’82—dc2l 98-9887

CIP

2 4 6 8 9 7 5 3 1

Printed in the United States of America on recycled paper.

The U.S. Department of Agriculture (USDA) prohibits discrim-ination in all its programs and activities on the basis of race,color, national origin, gender, religion, age, disability, politicalbeliefs, sexual orientation, and marital or family status. (Not allprohibited bases apply to all programs). Persons with disabili-ties who require alternative means for communication ofprogram information (Braille, large print, audiotape, etc.)should contact USDA’s TARGET Center at 202-720-2600 (voiceand TDD).

To file a complaint of discrimination, write USDA, Director,Office of Civil Rights,Room 326-W,Whitten Building,14th andIndependence Avenue,SW,Washington,DC 20250-9410 or call(202) 720-5964 (voice or TDD). USDA is an equal opportunityprovider and employer.

Every effort has been made to make this book as complete andas accurate as possible and to educate the reader.This text isonly a guide,however,and should be used in conjunction withother information sources on crop, weed and farm manage-ment. No single cover crop strategy will be appropriate andeffective for all conditions.The editor/authors and publisherdisclaim any liability, loss,or risk,personal or otherwise,whichis incurred as a consequence, directly or indirectly, of the useand application of any of the contents of this book.

Mention, visual representation or inferred reference of a prod-uct, service, manufacturer or organization in this publicationdoes not imply endorsement by the USDA, the SARE programor the authors.Exclusion does not imply a negative evaluation.

Graphic design, interior layout and cover design: Diane Buric.Interior illustrations by: 1. Marianne Sarrantonio (reprintedwith permission from the Northeast Cover Crop Handbook.1994. Rodale Institute. Emmaus, PA); and 2. Elayne Sears.Copy Editing:Valerie Berton and Andy Clark. Indexing: NancyHopkins. Printing: Jarboe Printing, Washington, D.C.. Coverphotos by Tom Gettings;orchard photo by Chuck Ingels,Univ.of Calif. Extension.

This book was written by Greg Bowman, Christopher Shirley and Craig Cramer, of CMR Editorial Services, for the Sustainable Agriculture Network.

ACKNOWLEDGMENTS 3

This book represents a true cooperativeeffort. Most writing and research was byChristopher Shirley, Greg Bowman and

Craig Cramer, formerly writers/editors for theNew Farm Magazine. Their experience writingfor the agricultural community shows in theirability to incorporate a vast amount of researchdata and farmer experiences into this publication.Contributors Marianne Sarrantonio, University ofMaine, Orono, ME, Sharad Phatak, University ofGeorgia, and Andy Clark, Coordinator of theSustainable Agriculture Network (SAN) eachwrote sections of the book. Robert Myers,Wayne Reeves, Seth Dabney andChuck Ingels contributed toAppendix B, Up-and-ComingCover Crops.

Farmers played a majorrole in developing thebook, detailing theircropping systems andthe management ofcover crops on theirfarms. Some were con-tacted repeatedly forfurther clarification, andmany also reviewed sec-tions of the manuscript.The value of the contribu-tions by farmers using covercrops in the field cannot be under-estimated. They generously gave oftheir time to provide true ground-testing andreality-checking to strenthen this publication.

A volunteer editorial board consisted of facultyand researchers from around the country: RobMyers, Jefferson Institute,Columbia, Mo., formerlydirector of SARE; Fred Magdoff, Northeast RegionSARE, University of Vermont; Seth Dabney, USDA-ARS Soil Sedimentation Lab;Wayne Reeves, USDA-ARS National Soil Dynamics Lab; MarianneSarrantonio, University of Maine;Walter Goldstein

and Jim Stute, Michael Fields Agricultural Institute,East Troy, Wis.; Richard Dick, Oregon StateUniversity; Jim Sims, Emeritus Professor, MontanaState University; Chuck Ingels, University of California Extension Service. Andy Clark,Coordinator of the Sustainable AgricultureNetwork, oversaw the project and coordinated the efforts of the writers, the designer and theeditorial board.

The complete manuscript was reviewed at leasttwice by each member of the editorial board.It wasalso reviewed by Mark Davis, Delaware State

University;John Luna,Oregon State University;Steve Diver, Appropriate Technology

Transfer for Rural Areas (ATTRA),Fayetteville, Ark.; John and

Lorraine Merrill, Stuart Farm,Stratham,N.H.;John Teasdale,USDA-ARS, Beltsville, Md.;Phil Bauer, USDA-ARS,Florence, S.C.; MorrisDecker,Professor Emeritus,University of Maryland;Noah Ranells, NorthCarolina State University;

and Valerie Berton, SAREcommunications specialist.Individual chapters of

Managing Cover CropsProfitably, 2nd Edition were

reviewed by cover crop expertsfrom the farm and research

communities.These farmers and scientists aretoo numerous to mention here, but their contri-butions were invaluable to this effort.

In preparation for the second edition, the firstedition was critically reviewed by Morris Decker,Professor Emeritus, University of Maryland; ZaneHelsel, Rutgers University; and Andy Clark, SAN.Fred Magdoff, who was the driving force behindthe first edition, participated in planning andreviewing throughout the process.

ACKNOWLEDGMENTS

BERSEEM CLOVER, an annual legume, produces abundant vegetation with multiple cuttings.

support of the Sustainable Agriculture Network(SAN). SAN is the communications and outreacharm of the SARE program. Other SARE supportcame in the form of extensive planning, design,writing and editing by SARE communicationsspecialist Valerie Berton, College Park, Md. SANpublications committee chair Beth Holtzman,Burlington,Vt., contributed publication oversight,contract management and overall good sense

about publishing sustainable agriculture infor-mation. Other members of the SAN

Management Committee commented onearly plans for the book, helped developbudgets, and were consulted on otheraspects of the project as needed.

As SAN Coordinator, I heartily thank allmembers of the sustainable agriculturecommunity for their cooperation in provid-ing information that will strenthen our agri-culture for future generations. Such

cooperation is truly the hallmark of thesustainable agriculture movement.

Andy Clark, CoordinatorSustainable Agriculture NetworkBeltsville, Md.

May, 1998

4 MANAGING COVER CROPS PROFITABLY

The first edition, written in 1991 by MikeBrusko at Rodale Institute, was used liberally inthe development and writing of this secondedition.

Mary Gold and Abiola Adeyemi, from theAlternative Farming Systems Information Centerat the National Agricultural Library,provided com-prehensive literature searching and facilitated theduplication and lending of cover crop literatureto the writers. Abiola Adeyemi also compiledparts of the Appendices and provid-ed clerical support,particularly dur-ing the reviews of the book.

Consulted repeatedly forguidance and informationwere reviewers or authorsSeth Dabney, Sharad Phatak,Marianne Sarrantonio, Jim Sims,John Teasdale, Mary V. Gold(National Agricultural Library,Beltsville, Md.), Aref Abdul-Baki(USDA/ARS, Beltsville, Md.) and Robert Bugg (University of California,Davis, Calif.).

The USDA Sustainable AgricultureResearch and Education (SARE) programfunded the project as part of its

BARLEY, a cool season grain, controls erosion and weeds in dry years and on light soils.

FOREWORD 5

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.

Cover crops can make you a better neighbor,too. They prevent nutrient leaching and runoff,and reduce or eliminate the off-site impacts ofherbicides and pesticides.

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.

Since the Sustainable Agriculture Network(SAN) published Managing Cover CropsProfitably in 1992, more and more farmers havetried cover crops and are researching their use infarming systems. Other research by university and government scientists, agricultural profes-sionals and numerous farm organizations hascontributed more information about how covercrops can enhance traditional cropping systems.

This book distills published and unpublishedcover crop experiences into a reader-friendlyreference tool for use by farmers and agriculturalprofessionals. Our writers reviewed publishedliterature in scientific journals and talked withfarmers and researchers using cover crops. Thededicated help of a knowledgeable editorial boardand reviewers throughout the country roundedout the book.

A publication of this scope cannot possiblydescribe all the cover crops currently in use.Wehave selected the most proven crops with thewidest possible application in the continentalUnited States. Because of space and time limita-tions, several very promising species were omit-ted or not given complete coverage. Some ofthese are mentioned in Appendix B, Up-and-Coming Cover Crops (p.158).Many other species

with great potential as cover crops in particularclimates or cropping systems are accessiblethrough publications and cover crop experts list-ed in the appendices.

Many of the proven species described in thebook may be more familiar as forage or cashcrops.These crops have been adapted for use ascover crops, which, strictly speaking, are notharvested. Our primary intent in this book is todescribe the use of these crops as cover crops.Because economics plays a major role in decidingwhich crops farmers include in their rotations,wedo mention some important alternative uses thatmake growing cover crops even more rewarding.If you plant one of these cover crops and wantthe option to harvest it as a cash crop, consultother resources for more complete information.

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. 30) 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 compli-cate cover crop management. No book can ade-quately address all the variables that make up acrop production system. Before planting a covercrop,learn as much as you can from this book andtalk to others who are experienced with thatcover crop. Consult state and local resources forspecific information about adaptation and man-agement of a cover crop in your area. See alsoRecommended Resources (p. 162).

We hope that this updated and greatly expand-ed edition of Managing Cover Crops Profitablywill lead to the successful use of cover crops on a wider scale as we continue to increase thesustainability of our farming systems.

Andy Clark, CoordinatorSustainable Agriculture Network (SAN)May, 1998

FOREWORD


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

for Your Farm. . . . . . . . . . . . . . . . . . . . . . . 12Building Soil Fertility and Tilth

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

Managing Pests with Cover Crops . . . . . . . . . 25• Georgia Cotton, Peanut Farmers

Use Cover Crops to Control Pests. . . . . . 26• Select Covers that Balance Pests,

Problems of Farm . . . . . . . . . . . . . . . . . . 30Crop Rotations with Cover Crops . . . . . . . . . 34

• Full-Year Covers Tackle Tough Weeds. . . 38Overview of Charts . . . . . . . . . . . . . . . . . . . . 43Chart 1:Top Regional Cover Crop Species. . . 47Chart 2: Performance and Roles. . . . . . . . . . . 48Chart 3A: Cultural Traits . . . . . . . . . . . . . . . . . 50Chart 3B: Planting . . . . . . . . . . . . . . . . . . . . . 51Chart 4A: Potential Advantages . . . . . . . . . . . 52Chart 4B: Potential Disadvantages . . . . . . . . . 53

Cover Crop SpeciesOverview of Nonlegume Cover Crops . . . 54Annual Ryegrass . . . . . . . . . . . . . . . . . . . . . . 55Barley . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58Oats. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62Cereal Rye . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

• Rye Smothers Weeds Before Soybeans . . 67Winter wheat . . . . . . . . . . . . . . . . . . . . . . . . 72

• Wheat Boosts Income and Soil Protection. . . . . . . . . . . . . . . . . . . . . 74

• Wheat Offers High-Volume Weed Control Too . . . . . . . . . . . . . . . . . . 75

Buckwheat . . . . . . . . . . . . . . . . . . . . . . . . . . 77Sorghum Sudangrass . . . . . . . . . . . . . . . . . . . 80

• Summer Covers Relieve Compaction . . 84Overview of Legume Cover Crops . . . . . . 85Grass/Legume Mixtures Expand

Possibilities . . . . . . . . . . . . . . . . . . . . . . . 86

Berseem Clover . . . . . . . . . . . . . . . . . . . . . . . 87• Crimson-Berseem Clover Combo

Works as Corn Underseeding . . . . . . . . 89• Nodulation: Match Inoculant to

Maximize N. . . . . . . . . . . . . . . . . . . . . . . 92Cowpeas . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95

• Cowpeas Provide Elegant Solution to Awkward Niche . . . . . . . . . . . . . . . . . 98

Crimson Clover . . . . . . . . . . . . . . . . . . . . . . 100Field Peas . . . . . . . . . . . . . . . . . . . . . . . . . . 105

• Peas Do Double Duty for Kansas Farmer . . . . . . . . . . . . . . . . 110

Hairy Vetch . . . . . . . . . . . . . . . . . . . . . . . . . 112• Vetch Beats Plastic . . . . . . . . . . . . . . . . 118

Medics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119• Jess Counts on GEORGE for N and

Organic Matter. . . . . . . . . . . . . . . . . . . 121• Southern Spotted Bur Medic Offers

Reseeding Persistence . . . . . . . . . . . . . . 122Red Clover. . . . . . . . . . . . . . . . . . . . . . . . . . 127Subterranean Clover . . . . . . . . . . . . . . . . . . 132Sweetclover. . . . . . . . . . . . . . . . . . . . . . . . . 139

• Sweetclover: Good Grazing,Great Green Manure . . . . . . . . . . . . . . 142

White Clover . . . . . . . . . . . . . . . . . . . . . . . . 147Woollypod Vetch . . . . . . . . . . . . . . . . . . . . . 151

AppendicesA.Testing Cover Crops on Your Farm. . . . . . 156B. Up-and-Coming Cover Crops . . . . . . . . . . 158C. Recommended Resources . . . . . . . . . . . . 162D. Seed Suppliers . . . . . . . . . . . . . . . . . . . . . 166E. Farming Organizations with

Cover Crop Expertise . . . . . . . . . . . . . . . 170F. Regional Experts. . . . . . . . . . . . . . . . . . . . 173G. Citations Bibliography . . . . . . . . . . . . . . . 180H. Resources from the Sustainable

Agriculture Network . . . . . . . . . . . . . . . . 198I. Reader Response Form . . . . . . . . . . . . . . . 200

Index . . . . . . . . . . . . . . . . . . . . . . . . .201

MANAGING COVER CROPS PROFITABLYSECOND EDITION

HOW TO USE THIS BOOK 7

Think of this book as a tool chest, not acookbook.You won’t find the one simplerecipe to 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.

The entire text of Managing Cover CropsProfitably, 2nd Edition is available on CD-ROM.The electronic version is a great resource for agri-cultural educators and computer-savvy producersbecause it allows users to search for crops withone click of the mouse—and download sectionsinto new files for presentations and fact sheets.To order, see p. 199.

1. Start with Top Regional Cover Crop Species(p. 47). 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 and management 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.48) lists ranges for N and dry matter pro-duction and ranks each cover crop’s potential forproviding 11 benefits. Cultural Traits (p. 50) andPlanting (p. 51) explains the growth, environ-mental tolerances, seeding preferences and estab-lishment costs for each crop.

• Narratives. The Table of Contents (p. 6) and the page numbers accompanying eachspecies in Charts 2, 3 and 4 direct you to the

heart of the book, the chapters on each covercrop. The chapters offer even more practicaldescriptions of how to plant, manage, kill andmake the best use of each species.

Don’t overlook Up-and-Coming Cover Crops(p. 158) that briefly describes promising butlesser known cover crops. One of them may beright for your farm.

3. With some particular cover crops in mind,step back and look at the big picture of how youcan fit cover crops into your farming operations.Sit down with a highlighter and explore thesechapters:

• Benefits of Cover Crops (p. 9) explainsimportant cover crop roles such as reducingcosts, 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 and Tilth (p. 16) shows how cover crops add organic matter andgreater productivity to the biological, chemicaland physical components of soil.

HOW TO USE THIS BOOK

SORGHUM-SUDANGRASS is a tall, warm-season grass that stifles weeds and decomposes to build soil organic matter.


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

• Crop Rotations(p. 34) explains how tointegrate cover crops andcash crops in sequence fromyear to year for optimum produc-tivity from on-farm resources.

• Citations Bibliography (p. 180) 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(inside front cover) shows whether a crop willsurvive the average winter in your area.We referto the USDA hardiness zones throughout thebook.

The U.S. Forest Service map, Ecoregions ofthe United States (inside back cover), served in part as the basis for the adaptation maps includ-ed at the beginning of each cover crop chapter.This ecosystem map, while designed to classifyforest growth, shows localized climate differ-ences, such as rainfall and elevation, within aregion. (See Bailey in Recommended Resources,p. 162).

4. Now that you’ve tried out most of the tools,revisit the charts and narratives to zero in on the

cover crops you want totry. The Appendices

include informationto help you run reli-able on-farm covercrop comparisontrials. You’ll alsofind contact infor-

mation for covercrop experts in your

region, seed suppliersand inoculant providers,

references to books and otheracademic papers cited in this book

and World Wide Web resources with morecover crop information.

5.Finally, share your cover crop plans with farmersin your area who have experience with covercrops. Your local Extension staff, regional IPMspecialist or a sustainable farming group in yourarea may be able to provide contacts.Be sure to taplocal wisdom.You can find out the cover crop prac-tices that have worked traditionally, and the newwrinkles or crops that innovative practitionershave discovered.

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

Cultivars of SUBTERRANEAN CLOVER, a low-growing, reseeding annual legume, are adapted 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 improve your bottom line even more over the years

as their soil-improving effects accumulate. Otherbenefits—reducing pollution,erosion and weed andinsect pressure—may be difficult to quantify or maynot appear in your financial statements. Identifyingthese benefits, however, can help you make sound,long-term decisions for your whole farm.

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 wouldany other crop, balancing costs against returns inall forms. Don’t limit your calculations, however,to the target cover crop benefit. A cover often has several benefits. Many cover crops offerharvest possibilities as forage, grazing or seed that work well in systems with multiple cropenterprises and 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. 92). 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 to cal-culate fertilizer reductions, see Building SoilFertility and Tilth with Cover Crops (p. 16).

The N value of legumes is the easiest covercrop benefit to evaluate, both agronomically and economically. This natural fertility input alone can justify 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. The result held true even if corn were priced as low as $1.80per bushel, or N fertilizer was applied at the rateof 180 lb. N/A (136).

• 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 in Wisconsin, based on a two year rota-tion of oats/legume > corn.Mean corn grain yieldfollowing these legumes was 163 bu./A for redclover and 167 bu./A for hairy vetch, comparedwith a no legume/no N fertilizer yield of 134bu./A (328).

RED CLOVER is an annual or multi-year legume that improves topsoil. It is easily overseeded into standing cropsor frostseeded into grains in early spring.

• 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 (322).

• 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 plants untilthey decompose. Fall-seededgrains or grasses can absorbup to 71 lb. N/A within threemonths of planting, a Mary-land study showed (30).

Addition of cover crops tocorn>soybean and corn>peanut>cotton rotationsand appropriate timing of fertilizer applicationusually reduce total N losses, without causingyield losses in subsequent crops, a USDA-ARScomputer modeling study confirms (293).

Reduce the Need for HerbicidesCover crops suppress weeds and reduce damageby diseases, insects and nematodes.

Many cover crops 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 effectsManaging Pests with Cover Crops (p. 30)

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

parasitoids that can reduce insect damagebelow economic thresholds

• Produce compounds that reduce nematodepest populations

• Encourage beneficial nematode speciesUsing a rotation of malting barley>cover crop

radish>sugar beets has successfully reduced sugarbeet cyst nematodes to increase yield of sugar

beets in a Wyoming test. Using this brassica covercrop after malting barley or silage corn substitut-ed profitably for chemical nematicides whennematode levels were moderate (184).

A corn>rye>soybeans>wheat>hairy vetch rota-tion that has reduced pesticide costs is at least as profitable as conventional grain rotations

without cover crops, an on-going study in southeasternPennsylvania shows (137).

Fall-planted brassica covercrops coupled with mechan-ical cultivation help potatogrowers with a long growingseason maintain marketable

yield and reduce herbicide applications by 25percent or more, a study in the inland PacificNorthwest showed (322).

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

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 andconserves moisture); sorghum-sudangrass (deeppenetrating roots can break compaction); and ryegrass (stabilizes field roads, inter-row areas andborders when soil is wet).

Prevent Soil ErosionQuick-growing cover crops hold soil in place,reduce crusting and protect against erosion dueto wind and rain. The aboveground portion ofcovers also helps protect soil from the impact ofraindrops.Long-term use of cover crops increaseswater infiltration and reduces runoff that cancarry away soil.

The key is to have enough stalk and leaf growthto guard against soil loss. Succulent legumes

To estimate your potentialN fertilizer savings from acover crop, see the sidebar,How Much N? (p. 22).


decompose quickly, especially in warm weather.Winter cereals and many brassicas have a betterchance of overwintering in colder climates.Theselate-summer or fall-planted crops often put on sig-nificant growth even when temperatures dropinto the 50s,and often are more winter-hardy thanlegumes (302).

In a no-till cotton system, use of cover cropssuch as winter wheat, crimson clover and hairyvetch can reduce soil erosion while maintaininghigh cotton yields, a Mississippi study shows (21).

Conserve Soil MoistureResidue from killed cover crops increas-es water infiltration and reduces evap-oration, resulting in less moisturestress during drought. Lightlyincorporated cover crops servedual roles. They trap surfacewater and add organic matter toincrease infiltration to the rootzone. Especially effective atcovering the soil surface aregrass-type cover crops such asrye, wheat, and sorghum-Sudangrass hybrid. Some water-effi-cient legumes such as medic andINDIANHEAD lentils provide cover cropbenefits in dryland areas whileconserving more moisture than conven-tional bare fallow (316).

Timely spring termination of a covercrop avoids the negative impact ofopposite water conditions: excessresidue holding in too much mois-ture for planting in wet years, or

living plants drawing too much moisture from thesoil in dry years.

Protect Water QualityBy slowing erosion and runoff, cover cropsreduce nonpoint source pollution caused bysediments, nutrients and agricultural chemicals.By taking up excess soil nitrogen, cover cropsprevent N leaching to groundwater. Cover cropsalso provide habitat for wildlife.

A rye cover crop scavenged from 25 to 100percent of residual N from conventional and no-till Georgia corn fields, one study showed. Upto 180 lb. N/A had been applied. A barley cover crop removed 64 percent of soil nitrogenwhen applied N averaged 107 lb./A (177).

Help Safeguard Personal HealthBy reducing reliance on agrichemi-cals for cash crop production,cover crops help protect thehealth of your family, neighborsand farm workers.They also help

address community health andecological concerns arising from

nonpoint source pollution attributedto farming activities.

Cumulative BenefitsYou can increase the range of benefitsby increasing the diversity of covercrops grown, the frequency of usebetween cash crops and the length oftime that cover crops are growing inthe field.

BENEFITS OF COVER CROPS 11

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


Cover crops provide many benefits,but they’re not do-it-all “wonder crops.”To find a 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 lit-tle easier by focusing on some proven ones.Thousands of species and varieties exist,however.The steps that follow can help you find crops thatwill work best with a minimum of risk andexpense.

1. Identify Your Problem or UseReview Benefits of Cover Crops (p. 9) to decidewhat you want most from a cover crop. Thissimplifies your search.

Some common goals for covers are to:• Provide nitrogen• Add organic matter• Improve soil structure• Reduce soil erosion • Provide weed control• Manage nutrients• Furnish moisture-conserving mulch

Having one or two secondary goals can narrowthe hunt when comparable covers could satisfy aprimary role.You might want habitat for benefi-cial organisms, better traction during harvest,faster drainage or another benefit.

2. Identify the NicheSometimes 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.

Look at your rotation first. Make a timeline of18 to 24 monthly increments across a piece of

paper.For each field,pencil in current or probablerotations, showing when you typically seed cropsand when you harvest them. If possible, sketch ina rough graph showing average daily temperatureduring the timeline, and another for average rain-fall.Add other key information, such as frost-freeperiods and times of heavy labor or equipmentdemand.

Look for open periods in each field, openspaces on your farm or opportunities in your sea-sonal work schedule. Also consider ways toextend or overlap cropping windows.

Here are examples of common niches in somesystems, and some tips:

Winter fallow niche. In many regions,seed win-ter covers at least six weeks before a hard frost.Winter cereals are an exception and can be plant-ed a little later. If ground cover needs are minimal,plant rye until the frost period for successful over-wintering, although N recycling will be limited.

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 underseeding) 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 immediately if possible,or seed just before a soaking rain. Species withsmall, round seeds, such as clovers, don’t need alot of moisture to germinate and can work theirway through tiny gaps in residue.

If you want to harvest a cereal grain cover crop,interseeding a legume might increase diseaserisks due to lower air circulation or insect pestrisk, so plan accordingly.Changing seeding rate orthe rotation sequence may lessen this risk.

To ensure adequate sunlight for the cover crop,overseed before full canopy closure of the primarycrop (at last cultivation of field corn, for example)or a few weeks before the cash crop starts to die.

SELECTING THE BEST COVER CROPS FOR YOUR FARMby Marianne Sarrantonio

SELECTING THE BEST COVER CROPS 13

Expect excessive field traffic around harvest-time? Choose tough, low-growing covers such as grasses or clovers. Limit traffic or delay a fieldoperation to allow for cover crop establishment.

Another option could be a reseeding winterannual that dies back and drops seed each springbut reestablishes in fall. Subclovers reseed well in regions south of Hardiness Zone 6. Shorter-season crimson clovers—especially varieties witha high hard-seed percentage that germinate overan extended period—work well in the Southeastwhere moisture is sufficient.

Summer fallow niche. Many vegetable rota-tions present cover crop opportunities—andchallenges. When double cropping, you mighthave fields with a three- to eight-week summerfallow. Quick-growing summerannuals provide erosion control,weed management, organic mat-ter and perhaps some N.

Consider overseeding into aspring crop with buckwheat,millet or sorghum-Sudangrass, ora warm-season legume such as cowpeas. Or tillout strips in the cover crop for planting a fallvegetable crop and control the remaining coverbetween the crop rows with mowing, partialcultivation or herbicide spraying.

Small grain rotation niche. Companion seed awinter annual cover crop with a spring grain,or frost seed a cover into winter grains. Soilfreezing and thawing pulls seed into the soil andhelps germination. Another option if soil moisture isn’t a limiting factor in your region:broadcast a cover before the grain enters bootstage (when seedheads start elongating) later inspring.

Full-year improved fallow niche. To rebuildfertility or organic matter over a longer period,perennials or biennials—or mixtures—requirethe least maintenance. Spring-seeded yellowblossom sweetclover flowers in summer of Year 2, has a deep taproot and gives plenty ofaboveground biomass. Also consider perennialforages recommended for your area.

Properly managed, living mulches give manygrowers year-round erosion protection,weed con-trol, nutrient cycling and even some nitrogen ifthey 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 orother nonaggressive turfgrasses work for beans,tomatoes and other vegetables.

Creating new niches. Have you honed a rota-tion that seems to have few open time slots? Planta cover in strips alternating with your annual veg-etable, herb or field crop. Switch the strips thenext year. Mow the strips periodically and blow

the topgrowth onto adjoiningcash crops as mulch. In a bedsystem, rotate out every third orfourth bed for a soil-buildingcover crop.

Another option: Band a coveror some insect-attracting shrubs

around fields or along hedgerows to suppressweeds or provide beneficial habitat where youcan’t grow cash crops.

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 on schedule?• Do I have the needed equipment and labor?

Look for open periodsin each field or openspaces on your farm.


4. Select the Best Cover CropYou have a goal and a niche. Now specify thetraits a cover crop would need to work 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 leaf growth orprevent hardening off before winter. Finally youwant easy maintenance.

The cover crop 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 isprobably the best option north of Zone 8. Amixture of low-growing legumes or a legume andgrass mix could also work. In warm regions, low-growing clovers such as strawberry clover andwhite clover work well together, although thesespecies may attract pocket gophers. BLANDO

brome and annual ryegrass are two quick-grow-

ing, reseeding grasses often suitable for orchardfloors. One of these might fill the bill with areseeding, winter annual legume such as crimsonclover, rose clover, subclover, an annual vetch oran annual medic, depending on your climate.

Example 2. A dairy lacks adequate storage in fall and winter for the manure it generates,which exceeds the nutrient needs for its silagecorn and grass/legume hay rotation.

The cover crop needs to:• establish effectively after (or tolerate) silage

corn harvest• take up a lot of N and P in fall and hold it until

springFor this dairy scenario, rye is often recom-

mended. Other cereal grains or brassicas couldwork if planted early enough.

Example 3. In a moderate rainfall region aftersmall grain harvest in late summer, you want a soil-protecting winter cover that can supplyN for no-till corn next spring. You want to kill the cover 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 residueHairy vetch works well in the Northeast,

Midwest and parts of the mid-South. Mixing itwith rye or another cereal improves its weed-management and moisture-conservation poten-tial.Crimson clover may be an appropriate choicefor the southeastern Piedmont. Austrian winterpea could be considered, alone or in a mix, incoastal plain environments. Where grain harvestoccurs in late spring or early summer, LANA wool-lypod vetch might be a better choice.

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

SELECTING THE BEST COVER CROPS 15

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 suchas cowpeas may work, especially if you can irrigateto hasten establishment during dry conditions.

5. Settle for the Best Available Cover. . . It’s likely the “wonder crop” you want doesn’texist. One or more species could come close, asthe above examples indicate.Top Regional CoverCrop Species (p. 47) can provide a starting point.Check with regional experts. Keep in mind thatyou can mix two or more species.

6. . . .Or Build a Rotation AroundCover 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. SeeFull-Year Covers Tackle Tough Weeds (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. 156) for some straightforwardtips on what to do next.

Adapted from Northeast Cover Crop Handbook by Marianne Sarrantonio, Rodale Institute, 1994.

WINTER (cereal) RYE is an annual grain that prevents soil and wind erosion. Its killed vegetation suppressesweeds 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 inbalance, your soil cycles nutrients efficiently,stores water and drains the excess, and maintainsan environment in which plants can thrive.

To recognize that a soil can be healthy, one has only to think of the soil as a living entity. Itbreathes, it transports and transforms nutrients, itinteracts with its environment,and it can even puri-fy itself and improve over time. If you view soil as a dynamic part of your farming system,unsustainablecrop management practices amount to soil neglect.That neglect could worsen as the soil sickens andloses 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 mostcommon reasons for including cover crops in a farming system may relate to the current season, the continued practice of cover croppingbecomes an investment in building healthy soilover 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 soil pro-file or by adding nitrogen to the soil.Their rootscan even help unlock some nutrients, convertingthem to more available forms. Cover crops pro-vide habitat or a food source for some importantsoil organisms, break up compacted layers in thesoil and help dry out wet soils.

EROSION PROTECTION

Erosion of topsoil occurs on many farms, depriv-ing fields of the most fertile portion that containsthe 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 (28). Once a soil particle is loose, it is muchmore vulnerable to being carried away byrunning water. Any aboveground soil cover cantake some of the punch out of a heavy rainfallsimply by acting as a cushion for raindrops.

A cover crop also can:• Slow the action of moving water just by

creating an obstacle course of leaves, stemsand roots through which the water mustmaneuver on its way downhill

• Increase the soil’s ability to absorb and holdwater, thereby preventing large quantities ofwater from moving across the soil surface

• Help stabilize soil particles in the cover croproot systemThe reduction in soil erosion due to cover

cropping will be roughly proportional to theamount of cover on the soil. The Universal SoilLoss Equation developed by the USDA SoilConservation Service (now the Natural ResourcesConservation Service) predicts that a soil cover ofjust 40 percent when winter arrives can reduceerosion 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 before harvestor planting as soon as possible after harvest. It’salso a good idea to maintain year-round soil coverwhenever possible.

BUILDING SOIL FERTILITY AND TILTH WITH 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 storage ofnutrients. Without organic matter, you have nosoil to speak of,only a dead mixture of ground-upand weathered rocks.

Organic matter includes thousands of differentsubstances derived from decayed leaves, roots,microorganisms, manure and even groundhogsthat died in their burrows. These substancesfunction 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 andconsists largely of recently added residues, micro-bial cells and the simpler waste products frommicrobial 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,so the active fraction is responsible for therelease of most N, as well as some K, P and othernutrients, from organic matter into the soil.The easily decomposed proteins and sugars burnup almost completely as energy sources, anddon’t leave 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 microor-ganisms will start munching on the more com-plex and tough material, such as celluloses andlignins,the structural materials of plants.Since cel-lulose is tougher than simple sugars, and ligninbreaks down very slowly, they contribute more tothe humus or stable fraction. Humus is responsi-ble for giving the soil that rich, dark, spongy feel-ing and for properties such as water retention andcation exchange capacity.

Plant materials that are succulent and richin 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,but will promote more stable organic matter, orhumus, leading to better soil physical conditions,increased nutrient-holding capacity and highercation exchange capacity.

In general, annual legumes are succulent.They release nitrogen and other nutrients quick-ly through the active fraction, but are not veryeffective at building up humus. Long-term use of succulent annual legumes can increase soil humus, however, as recent research suggests (354).

Grains and other grasses and nonlegumes willcontribute to humus production, but won’trelease nutrients very rapidly or in large quantities if incorporated as they approach matu-rity. Perennial legumes such as white and redclover may fall in both categories—their leaveswill break down quickly, but their root systemsmay become tough and fibrous and can con-tribute 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 farmersuse the term “crumb” to describe soil clusters


about the size of a grain of rice. A well-aggregated or “crumby” soil—not to be confusedwith someone else’s crummy or depleted soil—has good aeration. It allows better infiltration andretention of water.

Cover crops can promote good aggregation inthe soil through increased production of theseand other microbial glues, recent research hasshown. See Cover Crops Can Stabilize Your Soil(p. 19). Well-aggregated soils also are less prone to compaction, which has been shown to reduceyields of vegetables such as snap beans, cabbageand cucumber by 50 percent or more (371).

As they decompose, leguminous cover cropsseem to be better than grasses for production ofpolysaccharides (6). 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 more of soil building. The benefits of increasedorganic matter, however, are likely to be apparentlong before increased quantities are detectable.Some, such as enhanced aggregation, water infil-tration rates and nutrient release,will be apparentthe first season; others may take several years tobecome noticeable (354).

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 organicmatter under conventional tillage regimes.Tillage speeds up organic matter decompositionby exposing more surface area to oxygen, warm-ing and 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 resulting loss of organic matter causes the break-

down of soil aggregates and the poor soil struc-ture often seen 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 and improv-ing soil structure, cover crops enhance nutrientcycling in your farming system by taking up nutri-ents that otherwise might leach out of the soil pro-file. These excess nutrients have the potential topollute groundwater or local streams and ponds.

Of the common plant nutrients,nitrogen in thenitrate form is the most water-soluble and there-fore the most vulnerable to leaching. Anytime soil is bare and appreciable rain falls, nitrates areon the move. Nitrate can be present in the soil at the 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 release 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 their own 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 areharvested. For much of the continental U.S., cere-al rye is the best choice for catching nutrientsafter a summer crop. Its cold tolerance is a bigadvantage that allows rye to continue to grow inlate fall and put down roots to a depth of threefeet or more. Where winters are mild, rye cangrow through the winter months.

Research with soil high in residual N in themid-Atlantic’s coastal plain showed that cereal rye


took 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 (30). Legumes tend toestablish slowly in fall and are mediocre Nscavengers, 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 notgenerally on the express route with N. These

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, recent research suggests (372).Glomalin may be one of the most importantsubstances in promoting and stabilizing soilaggregates.

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.In low-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 in particular 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.

nutrients can be brought up from deeper soil lay-ers by any deep-rooted cover crop.The nutrientsare then released back into the active organic mat-ter 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.So the return of any plant or animal residue to the


soil helps maintain P availability. Cover crops help 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. 92).

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 managementfactors often interfere with nature’s ultra-efficientuse of organic or inorganic N. Learning a bit about the factors affecting N-use efficiency fromlegume plants will help build the most sustainablecropping system possible within your constraints.

How Much N is Fixed?A number of factors determine how much of the N 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.92). Use the correct rhizobial inoculant for thelegume you’re growing. Make sure it’s fresh, wasstored 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 requires iron, sul-fur and molybdenum to function properly. Soilsdepleted of these micronutrients will not supportefficient fixation. Tissue testing your cash cropscan help you decide if you need to adjustmicronutrient 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 (371).

• 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 inferior 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.48) 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 nodulesas little fertilizer factories pumping N into thesurrounding soil, that isn’t what happens. Thefixed N 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 theirbiomass nitrogen into the seeds or beans. Also,once the legume has stopped actively growing, itwill shut down the N-fixing symbiosis. In annuallegumes this occurs at the time of flowering; noadditional N gain will occur after that point.Unless you want a legume to reseed itself, it’s


generally a good idea to kill a legume cover cropin the early- to mid-blossom stage. You’ll haveobtained maximum legume N and need not delayplanting of the following cash crop any further,aside from any period you may want for residue decomposition as part of your seedbedpreparation.

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 andclimatic events following the death of that legumewill greatly affect the amount and timing of Nrelease from 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 (246). 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 (303). Green manures that are less protein-rich (N-rich) will take longer to release N.Those that are old and fibrous or woody are gen-erally left for hard-working but somewhat slug-gish fungi to convert slowly to humus over theyears, gradually releasing small amounts ofnutrients.

Other factors contribute significantly to howquickly a green manure releases its N. Weather has a huge influence. The soil organisms respon-sible for decomposition work best at warmtemperatures and are less energetic during coolspring months.

Soil moisture also has a dramatic effect.Research shows that soil microbial activity peaks

when 60 percent of the soil pores are filled with water, and declines significantly when mois-ture levels are higher or lower (193). This 60percent water-filled pore space roughly corre-sponds to field capacity, or the amount of waterleft in the soil when it is allowed to drain for 24hours after a 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 as 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 the density of the soil, generally allowing it todrain and therefore warm up more quickly. Alltold, residues incorporated into the soil tend todecompose and release nutrients much fasterthan those left on the surface, as in a no-till sys-tem.That’s not necessarily 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-


How Much N?To find out if you might need more N thanyour green manure supplied, 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 dimensionsand clip the plants at ground level within theknown area. Dry them out in the sun for a fewconsecutive days, or use an oven at about 140F for 24 to 48 hours until they are “crunchydry.”Use the following equation to determineper-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.

taining compounds such as sugars are mainlyenergy sources, which the microorganisms use asfuel to live. The process of burning this fuel sends most of the carbon back into the atmos-phere as carbon 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 theirpopulations quickly to tap the carbon-basedenergy that’s available. All the new bacteria,though, will need some N, as well as other nutri-ents,for body building before they can even begin

to eat. So any newly released or existing mineral N in soil gets scavenged 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 con-tent.They can “tie up” soil N, keeping it immo-bilized (and unavailable) to crops until thecarbon “fuel supply” starts depleting.Tie-up maylast for several weeks in the early part of thegrowing season, and crop plants may show theyellowing characteristic of N deficiencies. That is why it often makes sense to wait one to three

* 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 most small grains and other annual grasses, start with 2,000 lb./A at 6 inches and 100 percent ground cover.Add 300 lb. for each additional inch and multiply by (percentgroundcover/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.

To put 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 will

mineralize more slowly than in warm climates,as discussed above.So these are gross estimatesand a bit on the conservative side.

Of course, cover crops will not be the onlyN sources for your crops.Your soil will release

between 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 on Your Farm (p. 156) 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 your N from green manures and otheramendments, see the Northeast Cover CropHandbook, or the Farmers’ FertilizerHandbook, listed in Appendix C (p. 164).—Marianne Sarrantonio, Ph.D.

weeks after killing a low-N cover before plantingthe next crop, or to supplement with a morereadily available N source when a delay is notpractical.

Annual legumes have low C:N ratios, such as 10:1 or 15:1. When pure stands of annuallegumes are plowed down,the N tie-up may be sobrief you 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 inimmobolizing excess soil N than pure legumes

and, as stated earlier, the N is mineralized morerapidly from mixtures than from pure grass. A fall-seeded mixture will adjust to residual soil Nlevels.When the N levels are high, the grass willdominate and when N levels are low, the legumewill dominate the mixtures.This can be an effec-tive management tool to reduce leaching whilemaking the N more available to the next crop.

Potential LossesA common misunderstanding about using greenmanure crops is that the N is used moreefficiently because it’s from a plant source. This is not necessarily true. Nitrogen can be lost froma green manure system almost as easily as fromchemical fertilizers, and in comparable amounts.


The reason is that the legume organic N may beconverted to ammonium (NH4

+), then to ammonia(NH3) or nitrate (NO3

-) before plants can take it up.Under no-till systems where killed cover cropsremain on the surface, some ammonia (NH3) gascan be lost 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 lit-tle as seven to 10 days after plowing down a high-N legume, such as a hairy vetch stand. Since thefollowing crop is unlikely to have much of a rootsystem at that point, the N has a ticket forLeachville. Consider also that the green manuremay have been plowed down to as deep as 12inches—much deeper than anyone would con-sider applying chemical fertilizer. Moreover,green manures sometimes continue to decom-pose after the cash crop no longer needs N.ThisN also is prone to leaching.

To summarize, conventional plowing andaggressive disking can cause a rapid decomposi-tion of green manures, which could provide toomuch N too soon in the cropping season. No-tillsystems will have a reduced and more gradualrelease of N, but some of that N may be vulnera-ble to gaseous loss, either by ammonia volatiliza-tion or by denitrification. Thus, depending onmanagement, soil and weather situations, N fromlegume cover crops may not be more efficientlyused 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 into thegreen manure, then mow or incorporate itbetween the rows several weeks 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 the

release of N so it’s not as vulnerable to loss.Consider also that some portion of the N in the

green manure will be conserved in the soil in anorganic 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, have roots that reach asdeep as three feet in the soil within one crop-ping season.The action of numerous pointy littletaproots with the hydraulic force of a deter-mined plant behind them can penetrate soilwhere plowshares fear to go. Grasses, with theirtremendously extensive root systems, mayrelieve compacted surface soil layers. Sorghum-sudangrass can be managed to powerfully frac-ture subsoil. See Summer Covers RelieveCompaction (p. 84).

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 coverssupply 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 cover crops, however, can help ensure your soil’shealth and productivity for as long as you farm.

MANAGING PESTS WITH COVER CROPS 25

MANAGING PESTS WITH COVER CROPSBy Sharad C. Phatak

Crop 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. With limited tillage and careful attention to cultivar choice, placement and timing, covercrops can reduce infestations by insects, diseases,nematodes and weeds. Pest-fighting cover cropsystems help minimize reliance on pesticides,andas a result cut costs, reduce your chemical expo-sure, protect the environment, and increase con-sumer confidence in the food you produce.

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.Our goalis to learn agricultural practices that are environ-mentally sound,economically feasible and sociallyacceptable.

Environmentally sustainable pest managementstarts with building healthy soils. Research insouth Georgia (see sidebar Georgia Cotton,Peanut Farmers, p. 26) shows that crops grownon biologically active soils resist pest pressuresbetter than those grown on soils of low fertility,extreme pH, low biological activity and poor soilstructure.

There are many ways to increase biologicalactivity in soil. Adding more organic material bygrowing cover crops or applying manure helps.Reducing or eliminating pesticides favors diverse,healthy populations of beneficial soil flora andfauna. So does reducing or eliminating tillage thatcauses losses of soil structure, biological life ororganic matter. These losses make crops morevulnerable 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 remains

productive for row crops and vegetables for thefirst two to three years. High yields of agronomicand horticultural crops are profitable, withcomparatively few pesticide and fertilizer inputs.After that—under conventional systems with cus-tomary clean tillage—annual crops require higherinputs.The first several years of excessive tillagedestroys the food sources and micro-niches onwhich the soil organisms that help suppress pestsdepend. When protective natural biologicalsystems are disrupted, pests have new openingsand 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 encouragingother organisms.Cover crops bring more forms oflife 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. These natural pest controls—called beneficials in agriculturalsystems—include predator and parasitoid insectsand diseases. Predators kill and eat other insects;parasitoids spend their larval stage inside anotherinsect, which then dies as the invader’s larvalstage ends. However, in conventional systems,synthetic chemical treatments that kill insectpests also typically kill their natural enemies.Conserving and encouraging beneficial organismsis key to achieving sustainable pest management.

You should aim to combine strategies that makeeach farm field more hospitable to beneficials.Reduce pesticide use, and, when use is essential,select materials that are least harmful to beneficials.Avoid or minimize cultural practices such as tillingand burning that kill beneficials and destroy theirhabitat. Build up the sustenance and habitat thatbeneficials need. Properly managed cover crops


TIFTON, Ga.—Here in southwestern Georgia,I’m working with farmers who have haddramatic success creating biologically activesoil in fields that have been conventionallytilled for generations.We still grow thetraditional cash crops of cotton and peanuts,but with a difference.We’ve added covercrops, virtually eliminated tillage, and addednew cash crops that substitute for cotton and peanuts some years to break diseasecycles and 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 lime prior to the first planting of rye in theconversion year. This is usually the last tillagewe plan to do on these fields for many years.Together, these practices give us significantpest management benefits within three years.

Growers are experimenting with a basicwinter cover crop>summer cash croprotation. Our cover crops are ones we know grow well here. Rye provides control ofdisease, weed and nematode threats. Legumecrops are crimson clover, subterranean cloveror cahaba vetch.They are planted with the rye or along field borders, around ponds, nearirrigation lines and in other non-cropped areasas close as possible to fields to provide thefood needed to support beneficials at higherpopulations.

When I work with area cotton and peanutfarmers who want to diversify their farms, weset up a program that looks like this:• Year 1. Fall—Adjust fertility and pH

according to soil test. Deep till if necessaryto relieve subsurface soil compaction. Plant

Georgia Cotton, Peanut Farmers Use Cover Crops to Control Pestsa cover crop of rye, crimson clover, cahabavetch or subterranean clover.Spring—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 cahaba

vetch, allow crimson or subclover hard seedto germinate.Spring—Strip-till cotton.

• Year 3. Fall—Plant rye.Spring—Desiccate rye with herbicides.

No-till plant peanuts.• Year 4. Year 1 starts the cycle again.

Vegetable farmers frequently use fall-plantedcereal rye plowed down before vegetables,or crimson clover strip-tilled before plantingvegetables.The crimson clover matures,drops hard seed, then dies. Most of the seedgerminates in fall. Cereal/legume mixes havenot been more successful than single-cropcover crop plantings in our area.

Some vegetable farmers strip-till rows intorye in April. The strips are planted in early May to Southern peas, lima beans or snapbeans. Rye in row middles will be dead ornearly dead. Rye or crimson clover cancontinue the rotation.

Vegetable farmers also broadcast crimsonclover in early March. They desiccate thecover, strip-till rows, then plant squash in April.The clover in the row middles will set seedthen die back through summer. The crimsonstrips will begin to regrow in fall from thedropped seed, and fall vegetables may beplanted in the tilled areas after the July squashharvest.

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

supply moisture, physical niches and food in theform of insects,pollen,honeydew and nectar.

By including cover crops in your rotations andnot spraying insecticides, beneficials often are

already in place when you plant spring or sum-mer crops.However,if you fully incorporate covercrops, you destroy or disperse most of the benefi-cials that were present. Conservation tillage is a


better option because it leaves more of the covercrop residue on the surface. No-till planting onlydisturbs an area 2 to 4 inches wide,while strip-till-ing disturbs an area up to about 24 inches widebetween 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 that

The farmers get weed control by flail mowingherbicide-killed, fall-planted rye, leaving about6 inches of stubble. One or two post-emergeherbicide applications should suffice in thefirst few years. I don’t recommend cultivationfor weed control because it increases risks ofsoil erosion and damages the protective outerleaf layer that helps prevent plant diseases.

We see changes on farms where therotations stay in place for three or more years:

• Insects. Insecticide costs are $50 to $100/A less than conventional cropmanagement in the area for all kinds of crops.The farmers using the alternativesystem often substitute with insect controlmaterials such as Bacillus thuringiensis (Bt),pyrethroids and insect growth regulators that have less severe environmental impact.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 other non-crop areas, these farmers are increasing thenumbers of beneficials in the fieldenvironments.

Pests that are no longer a problem on thecover-cropped farms include thrips,bollworm,budworm,aphids, fall armyworm,beetarmyworm and white flies.On my no-tillresearch plots with cover crops and longrotations, I’ve not used insecticides for six yearson peanuts, for eight years on cotton and for 12years on vegetables. I’m working with growerswho use cover crops and crop rotations toeconomically produce cucumbers, squash,peppers,eggplant,cabbage peanuts, soybeansand cotton with only one or two applicationsof insecticide—sometimes with none.

• Weeds. Strip-tilling into over-winteredcover crops provides acceptable weedcontrol for relay-cropped cucumbers (264).Conventional management of rye in our areais usually to disk or kill it with broad-spectrum herbicides such as paraquat orglyphosate.

• 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 wherepest nematodes are not a major problem,this system keeps them from becoming aproblem.

Even though the conventional wisdom saysyou can’t build organic matter in our climateand soils, we have top-inch readings of 4percent organic matter in a field that tested0.5 percent four years ago.

We are still learning,but know that we canrotate crops,use cover crops and cut tillage to greatly improve our sustainability. In ourexperience,we’ve reduced total costs by asmuch as $200 per acre for purchased inputs and tillage.Parts of our system will work inmany places.Experiment on a small scale tolook more closely at what’s really going in yoursoil and 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


are planted into the cover-crop residue. Theultimate goal is to provide year-round food andhabitat for beneficials to ensure their presencewithin or 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, which feedon many species, may be an important biologicalcontrol. During periods when pests are scarce orabsent, several important generalist predatorscan subsist on nectar, pollen and alternative preyafforded by cover crops. This suggests you canenhance the biological control of pests by usingcover crops as habitat or food for the beneficialsin 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.

Recent research has looked carefully at howbeneficials and crops interact. In undisturbed,biodiverse settings, the interactions are complexand intricate. Crop plants, when attacked bypests, send signals to which other insectsrespond. Appropriate beneficials move in to find their prey (349).

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 beetle 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 cropscan enhance the soil and field environment tofavor beneficials. Success depends on properlymanaging the cover crop species matched with the cash crops and anticipated pest threats.While we don’t yet have prescription plantingsguaranteed to bring in all the needed benefi-cials—and only beneficials—for long lists of cashcrops, we know some associations :

• We identified 13 known beneficial insectsassociated with cover crops during one growingseason in south Georgia vegetable plantings (34,36, 39).

• 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 beneficial

BUCKWHEAT grows quickly in cool, moist weather.


insects. This approach has been used successfullyby California almond and walnut growers partici-pating in the Biologically Intensive OrchardSystems (BIOS) project of the University ofCalifornia (142).

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. Benefitsinclude weed, insect and dis-ease suppression, improvedfruit quality and overall lowerproduction cost.

• Leaving “remnantstrips” of a cover when most of the crop ismowed or incorporated provides a continuingrefuge and food source for beneficials, whichmight otherwise leave the area or die. Thismethod is used in orchards when continuedgrowth of cover crops would cause moisturecompetition with trees.

• Insect movement is orchestrated in a systemdeveloped by Oklahoma State University forpecan growers. As legume mixtures senesce,beneficials migrate into trees to help suppressharmful insects. Not mowing the covers fromAugust 1 until shuck split of the developingpecans lessens the unwanted movement of stinkbugs, a pest which can damage green pecans(209). In California, lygus bugs on berseem cloveror alfalfa are pests of cash crops. Be careful thatcover crop maturity or killing a cover doesn’tforce pests into a neighboring cash crop.

Disease ManagementGrowers traditionally have been advised to turnunder plant debris by moldboard plowing to

minimize disease losses (259, 260, 331, 333, 334).Now we realize that burying cover crop residuesand disrupting the entire soil profile eliminatesbeneficial insect habitat and weed control bene-fits. The increased use of conservation tillageincreases the need to manage crop disease with-out burying cover crops.

Plant infection by microorganisms is rare (254).A pathogen has to cross many barriers before itcan cause a disease to roots, stem or leaves.Youcan use cover crops to reinforce two of thesebarriers.

Plant cuticle layer. This often waxy surface layeris the first physical barrier to plant infection.Many pathogens and all bacteria enter the plantthrough breaks, such as wounds, or natural open-

ings, such as stomata, in thiscuticle layer. This protectivelayer can be physically dam-aged by cultivation, sprayingand sand-blasting from winderosion, as well as by theimpact and soil splashing

from raindrops and overhead irrigation. In well-developed minimum-till or no-till crop systemswith cover crops, you may not need cultivationfor weed control (see below) and you can mini-mize spraying.Organic mulches from living,dyingor killed covers that hold soil and stop soil splash-ing protect crops from injury to the cuticle.

Plant surface microflora. Many benign organ-isms are present on the leaf and stem surface.They compete with pathogens for a limited sup-ply of nutrients.Some of these organisms producenatural antibiotics. Pesticides, soaps, surfactants,spreaders and sticking agents can kill or disruptthe activities of these beneficial microorganisms,weakening the plant’s defenses. Cover crops canhelp this natural protection process work byreducing the need for synthetic crop protectionmaterials. Further, cover crop plant surfaces cansupport healthy populations of beneficialmicroorganisms, including types of yeasts, thatcan migrate onto a cash crop after planting ortransplanting.

Cover crops can enhance thesoil and field environmentto favor beneficial insects.


Many crops can be managed as cover crops,but only a few have been studied specificallyfor their pest-related benefits on cash cropsand field 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 versatilecover crop used in the continental UnitedStates. Properly managed under conservationtillage, rye has the ability to reduce soil-bornediseases, nematodes and weeds. Rye is a non-host plant for root-knot nematodes and soil-borne diseases. It produces significant biomassthat smothers weeds when it is left on thesurface and also controls weedsallelopathically through 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 mostvegetables. Rye will not control weedy grasses.Because it can increase numbers of cut wormsand wire worms in no-till planting conditions,rye is not the most suitable cover where thoseworms are a problem ahead of grass crops likecorn, sweet corn, 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 weedsbecause it produces less biomass and has lessallelopathic effect.

• Crimson Clover (Trifoliumincarnatum)—Used as a self-reseeding winterannual legume throughout the Southeast, fall-planted crimson clover supports and increasessoil-borne diseases, pythium-rhizoctoniacomplex and root-knot nematodes. Itsuppresses weeds effectively by forming athick mulch. Crimson supports high densitiesof beneficial insects by providing food andhabitat. Because some cultivars produce “hardseed” that resists immediate germination,crimson clover can be managed to reseed inlate spring so that it resumes its growth in latesummer and fall.

Soilborne pathogenic fungi limit production ofvegetables and cotton in the southern U.S. (332,333, 334, 335). Rhizoctonia solani, Pythiummyriotylum, Pythium phanidermatum andPythium irregulare are the most virulent patho-genic fungi that cause damping-off on cucumbersand snap beans. Sclerotium rolfsii causes rot in all vegetables and in peanuts and cotton. Infectedplants that do not die may be stunted because oflesions caused by fungi on primary or secondaryroots,hypocotyls and stems.But after two or threeyears in cover cropped, no-till systems, damping-off is not a serious problem, experience on southGeorgia farms and research plots shows. Highersoil organic matter may help.

In soils with high levels of disease inoculum,however, it takes time to reduce population lev-els of soil pathogens using only cover crops.After tests in Maine with oats, broccoli, whitelupine (Lupinus albus) and field peas (Pisumsativum) as covers, researchers cautioned it maytake three to five years to effectively reducestem lesion losses on potatoes caused by R.solani (190).Yet there are single-season improve-ments, too. For example, in an Idaho study,Verticillium wilt of potato was reduced by 24 to29 percent following Sudangrass green manure.Yield of U.S.No.1 potatoes increased by 24 to 38percent compared with potatoes followingbarley or fallow (322).

Select Covers that Balance Pests, Problems of Farm


• Subterranean Clover (Trifoliumsubterraneum)—A self-reseeding annuallegume, fall-planted subterranean clover carriesthe same risks as crimson clover with soil-borne diseases and nematodes. It suppressesweeds more effectively in the deep South,however, because of its thick and low growthhabit. Subclover supports a high level ofbeneficial insects.

• Cahaba White Vetch (V. sativa X V.cordata)—This cool-season annual legume is ahybrid vetch that increases soilborne diseasesyet suppresses root-knot nematodes. Itsupports beneficial insects, yet attracts veryhigh numbers of the tarnished plant bug, aserious pest.

• Buckwheat (Fagopyrum esculentum)—A summer annual non-legume, buckwheat isvery effective in suppressing weeds whenplanted thickly. It also supports high densitiesof beneficial insects. It is suitable for sequentialplanting around non-crop areas to providefood and habitat for beneficial insects. It isvery attractive to honeybees.

A well-planned crop rotation maximizesbenefits and compensates for the risks ofcover crops and cash crops. Planting rye in a

no-till system substantially reduces root-knotnematodes, soil-borne diseases and broadleafweeds. By using clovers and vetches in yourfields and adding beneficial habitat in non-cultivated areas, you can increase populationsof beneficial insects that help to keep insectspests under control. Mixed plantings of a smallgrains and legumes combine benefits of bothwhile reducing their shortcomings.

As pesticides of all types (fungicides,herbicides, nematicides and insecticides) arereduced, the field environment becomesincreasingly resilient in keeping pest outbreaksin check. Plantings to further increasebeneficial habitat in non-cultivated areas canhelp maintain pollinating insects and pestpredators, but should be monitored to avoidbuild-ups of potential pests. Researchers areonly beginning to understand how to managethese “insectary plantings.”

Editor’s Note: Each cover crop listed here,except for cahaba vetch, is included in thecharts (pp. 48 and following) and is fullydescribed in its respective section. Check theTable of Contents (p. 6) for location.—Sharad C. Phatak

Nematode ManagementNematodes are minute roundworms that interactdirectly and indirectly with plants. Some speciesfeed on roots and weaker plants, and also intro-duce disease through feeding wounds. Mostnematodes are not plant parasites,but feed on andinteract with many soil-borne microorganisms,including fungi, bacteria and protozoa. Damagefrom 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 asroot galls, swollen root tips or unnatural rootbranching.

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

This coexistence would be the case in the undis-turbed field or woodland described above.

In conventional crop systems, pest nematodeshave abundant food and little environmental resis-tance. This can lead to rapid expansion of plantparasitic species, plant disease and yield loss.Cropping systems that increase biological diversi-ty over time usually prevent the onset ofnematode problems. Reasons may include adynamic soil ecological balance and improved,healthier soil structure with higher organicmatter. In Michigan, some potato growers reportthat two years of alfalfa to limit nematodesbetween potato crops is sustainable for thembecause of improvements to potato productionand lower pest control costs (20).


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(296). One Iowa farmer reports that researchersanalyzing his fields have found no evidence thathairy vetch,a host for soybean cyst nematode,hascaused any problem with the pest in his soy-beans. This may be due to his use compost instrip-cropped fields with an oats/hairyvetch>corn>soybean rotation (346).

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

brassicasCover crops may also improve overall plant

vitality to lessen the nematode impact on yield.But if you suspect nematode trouble, send a soilsample for laboratory analysis to positively identi-fy the nematode species.Then be sure any covercrops you try aren’t alternate hosts for that pestspecies. 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 (Tagetespatula), hairy indigo (Indigofera hirsuta), showycrotalaria (Crotolaria spectabilis), sunn hemp(Crotalaria juncea) and velvetbean (Mucunadeeringiana).

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 adepth of several inches suppressed Columbialance nematodes in North Carolina cotton fields

better 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 (14).

Malt barley, corn, radishes and mustard some-times worked as well as the standard nematicideto control sugar beet nematode in Wyoming sugarbeets,a 1994 study showed.Increased productionmore than offset the cover crop cost, and lambgrazing of the brassicas increased profit withoutdiminishing nematode suppression. The success is conditional upon a limited nematode density.The cover crop treatment was effective only ifthere were fewer than 10 eggs or juveniles percubic centimeter of soil. A moderate sugar beetnematode level was reduced 54 to 75 percent inabout 11 weeks, increasing yield by nearly 4 tonsper acre (184).

Weed ManagementCover crops are widely used as smother crops toshade and out-compete weeds. Cereal grainsestablish quickly as they use up the moisture, fer-tility and light that weeds need to survive.Sorghum-sudangrass hybrids and buckwheat arewarm-season crops that suppress weeds throughthese physical means and by plant-producednatural 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 is more variable.Rye is a major com-ponent in the killed organic mulches used 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 in recent yearsspecifically to enhance weed suppression bycover crops. The undercutter uses a wide blade to slice just under the surface of raised beds, sev-ering cover crop plants from their root mass.Anattached rolling harrow increases effectiveness(69, 70, 71, 72). A Buffalo rolling stalk chopper


does no direct tillage, but aggressively bends andcuts crops at the surface (132). Both tools workwell on most legumes when they are in mid-bloom stage or beyond.

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 (71, 115).

Cover crops can also serve as a “living mulch”to manage 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.They may also provide organic matter,some nitro-gen (if legumes), beneficial insect habitat, erosionprevention, wind protection and a tough sod tosupport field traffic.

To avoid competition with the cash crop, livingmulches can be chemically or mechanicallysuppressed. In the Southeast, some cool-seasoncover crops such as crimson clover die out natu-rally during summer crop growth and do notcompete for water or nutrients. However, covercrops that regrow during spring and summer—such as subterranean clover, white clover and redclover—can compete strongly for water withspring-planted crops unless the covers are ade-quately suppressed.

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,woolypodvetch, oats, barley, red clover and an oats/hairyvetch mix were suppressed as needed with fluaz-ifop and metribuzin (280).

Cover crops often suppress weeds early, thenprevent erosion or supply fertility later in the sea-son. For example, shade-tolerant legumes such asred 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.

Cover crops can play a pest-suppressing roleon virtually any farm. As we find out more aboutthe pest management benefits of cover crop sys-tems, they will become even more attractivefrom both an economic and an environmentalperspective. Traditional research will identifysome new pieces of these biologically basedsystems. However, growers who understand howall the elements of their farm fit together will be the people who will really bring cover cropsinto the prominence they deserve in sustainablefarming.

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


Readers’ note: > indicates progression toanother crop; / indicates a mixture of cropsgrowing at the same time.

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

rotations that take full advantage of their benefits.This section will explore some of the systemsused successfully by farmers in different regionsof the U.S.One might be easily adapted to fit yourexisting crops, equipment and management.Other examples may point out ways that you canmodify your rotation to make the addition ofcover crops more profitable and practical.

Whether you add covers to your existing rota-tions or totally revamp your farming system, it iscrucial that you devote as much planning andattention to your cover crops as you do to yourcash crops. Failure to do so can lead to failure ofthe cover crop and cause problems in other partsof your system. Also remember that there is likelyno single cover crop that is right for your farm.Ultimately, rotating cover crops might be yourbest strategy. (See, for example, CaliforniaVegetable Crop Systems, p. 37). Like any othercrop, pest pressures may build up if a cover cropis grown too often in the same field.

Before you start:• Review Benefits Of Cover Crops (p. 9) and

Selecting the Best Cover Crops For Your Farm(p. 12)

• Decide which benefits are most important to you

• 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. 173)

• Start small on an easily accessible plot thatyou will see oftenBe an opportunist—and an optimist. If your

cropping plans for a field are disrupted by weath-er or other conditions outside of your control,this

may be the ideal window for establishing a covercrop. Consider using an early-maturing cash cropto allow for timely planting of the cover crop.Theideas in this book will help you see cover cropopportunities in what used to look like problems.

COVER CROPS FOR CORN BELT GRAIN 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 nitrogen feed-er; soybeans benefit little, if at all, from cover cropN; and that you have a shorter time for springlegume growth before corn than before soybeans.

Cover crop features: rye provides winter cover,scavenges N after corn,becomes a long-lasting (6-week) residue for your beans to suppress weedsand hold moisture; hairy vetch provides springground cover,abundant N and a moderate-term (3to 4 week) mulch for the next corn crop; fieldpeas are similar to vetch, but residue breaksdown faster; red clover is also similar, but pro-duces slightly less N and has less vigorous springregrowth; berseem clover grows quickly to pro-vide several cuttings for high-N green manure,then winterkills.

Here are some options to consider adapting toyour system:

Corn>Rye>Soybeans>Hairy Vetch. In Zone 7and warmer, you can grow a cover crop everyyear between your corn and full-season beans.Also, you can use wheat or another small grain to

CROP ROTATION WITH COVER CROPS

CROP ROTATION WITH COVER CROPS 35

replace the cover crop before beans, in a three-crop, two-year rotation (corn>wheat>doublecropbeans). 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 acultivator.

Kill the rye once it is aboutknee-high, or let it go a bitlonger, killing it a couple ofweeks before planting beans.Killing the rye with herbi-cides and no-tilling beans in narrow rows allowsmore time for cover crop growth, since you don’thave to work the ground. If soil moisture is low,consider killing the rye earlier. Follow the beanswith hairy vetch or a vetch/small grain mixture.Legumes must be seeded at least 6 weeks beforehard frost to ensure winter survival. Seed bydrilling after soybean harvest, or by overseedingbefore leaf drop. Allow the vetch (or mixture) togrow as long as possible in spring for maximum Nfixation.

Worried about planting your corn a bitlate because you’re waiting for your cover crop tomature? Research in Maryland, Illinois and else-where suggests that planting corn towards theend of the usual window when using a legumecover crop has its rewards. The delay can result in greater yields than earlier planting, due togreater moisture conservation and more N pro-duced by the cover crop, or due to the timing ofsummer drought (62, 64, 243, 338). Check yourstate variety trial data for a shorter season cornhybrid that yields nearly as well as slightly longerseason corn.The cover crop benefit should over-come many yield differences.

Worried about soil moisture? There’s noquestion 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, rye can quickly dry out a field.Later in the season, killed cover crop residues in minimum tillage systems can conservemoisture and increase yields.

In dryland areas of the Southern Great Plains,lack of water limits cover crop use. (See DrylandCereal Cropping Systems, p. 40).

In any system where youare using accumulated soilmoisture to grow your cashcrop, you need to be extracareful.However, as noted inthis section and elsewherein the book, farmers and

researchers 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>HairyVetch. This rotation is similar to thecorn>rye>soybeans rotation described above,except you add a year of small grains followingthe beans. This is the standard rotation in thegrain-growing regions of Paraguay and Brazil,where it is critical to maintain soil organic matter.In crop rotation research from different areas,many benefits accrue as the rotation becomeslonger. This is because weed, disease and insectpest problems generally decrease with anincrease in years between repeat plantings of thesame 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. If seed-ing with small grains, select cover crops that willstand shade and some traffic.

The length of the growing season will deter-mine how you fit in cover crops after full-season

Growers are looking to adda small grain to theircorn>soybean rotation.


soybeans 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 har-vest, use a small grain rather than no cover cropat all.

The small grain scavenges leftover N followingbeans. Legume cover crops reduce fertilizer Nneeded for following corn, a heavy N feeder. Ifyou cannot seed the legume at least six weeksbefore a hard frost, consider overseeding beforeleaf drop or at last cultivation.

An alternate rotation for the lower mid-South is corn>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 late sum-mer under the beans. Kill the cover crop beforecorn the next spring. If possible, choose a differ-ent cover crop following the corn this time toavoid potential pest and disease problems withthe crimson clover.

▲ Precaution. In selecting a cover crop tointerseed, 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 general rotation effects in weedsuppression and natural controls of disease andinsect pests. It was more profitable in recent years as the cost of synthetic N increased. Cornbenefits from legume-fixed N, and from theimproved cation exchange capacity in the soilthat comes with increasing organic matter levels.

With the changes in base acreage requirementsin the 1996 Farm Bill, growers in the upperMidwest are looking to add a small grain to theircorn>bean rotation.The small grain, seeded aftersoybeans,can be used as a cover crop,or it can begrown to maturity for grain.When growing wheat

or oats for grain, frost-seed red clover or sweet-clover in March, harvest the grain, then let theclover grow until it goes dormant in late fall.Follow with corn the next spring. Some sec-ondary tillage can be done in the fall, if conditionsallow.One option is to attach sweeps to your chis-el plow and run them about 2 inches deep, cut-ting the clover crowns (326).

Alternatively, grow the small grain to maturity,harvest, then immediately plant a legume covercrop such as hairy vetch or red clover in August orearly September. Soil moisture is critical for quickgermination and good growth before frost. Formuch of the northern U.S., there is not time toplant a legume after soybean harvest,unless it canbe seeded aerially or at the last cultivation. Ifgrowing spring grains, seed red clover or sweet-clover directly with the small grain.

Adding the small grain to the rotation helpscontrol white mold on soybeans, since two yearsout of beans are needed to reduce pathogen pop-ulations. Using a grain/legume mix will scavengeavailable N from the bean crop, hold soil overwinter and begin fixing N for the corn.Clovers orvetch can be harvested for seed,and red or yellowclover can be left for the second year as a greenmanure 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. The berseem can be clipped severaltimes for green manure.

▲ Precaution. Planting hairy vetch with smallgrains may make it difficult to harvest a cleangrain crop. Instead, seed vetch after small grainharvest.

COVER CROPS FOR VEGETABLE PRODUCTION

Vegetable systems often have many windows forincluding cover crops. Periods of one to twomonths between harvest of early planted springcrops and planting of fall crops can be filled using fast-growing warm-season cover crops such


as buckwheat, cowpeas, sorghum-sudangrasshybrid, or another crop adapted to your condi-tions. As with other cropping systems, plant awinter annual cover crop on fields that otherwisewould lie fallow.

Where moisture is sufficient, many vegetablecrops can be overseeded with a cover crop, whichwill then be established and growing after vegetableharvest. Select cover crops that tolerate shade andharvest traffic, especially where there will be multi-ple pickings,such as in tomatoes or peppers.

Cover crop features: Oats add lots of biomass,are a good nurse crop for spring-seeded legumes,and winterkill, doing away with the need forspring killing and tilling. Sorghum-sudangrasshybrid produces deep roots and tall, leafy stalksthat die with the first frost. Yellow sweetcloveris a deep rooting legume that provides cuttings ofgreen manure in its second year. White clover isa persistent perennial andgood N source.

In Zone 5 and cooler,plant rye, oats or a summerannual (in August) after snapbean or sweet corn harvestfor organic matter produc-tion and erosion control,especially on sandy soils. Incorporate the follow-ing spring, or leave untilled strips for continuedcontrol 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 asummer crop.

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 TackleTough Weeds (p. 38).

3 Year: Winter Wheat/Legume Interseed>Legume>Potatoes. This eastern Idaho rotationconditions soil, helps fight soil disease andprovides N. Sufficient N for standard potatoesdepends on rainfall being average or lower toprevent leaching that would put the soil N belowthe shallow-rooted cash crop.

1 Year: Lettuce>Buckwheat>Buckwheat>Broccoli>White Clover/Annual Ryegrass.TheNortheast’s early spring vegetable crops oftenleave little residue after their early summer har-vest. Sequential buckwheat plantings suppress

weeds, loosen topsoil andattract beneficial insects.Buckwheat is easy to kill bymowing in preparation for falltransplants. With light tillageto incorporate the relativelysmall amount of fast-degrad-ing buckwheat residue, you

can then sow a winter grass/legume cover mix tohold soil throughout the fall and over winter.Planted at least 40 days before frost, the whiteclover should overwinter and provide greenmanure or a living mulch the next year.

California Vegetable Crop SystemsInnovative 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>DryBeans>Common Vetch>Tomatoes>S-S Hybrid/Cowpea>Safflower. The N needs of the cashcrops of sweet corn,dry beans,safflower and can-ning tomatoes determine, in part,which covers togrow. Corn, with the highest N demand, is pre-

Residue from small grainsprovides organic matter forsoil building. . . to preventerosion over winter.


ceded by LANA vetch, which produces more N thanother covers.Before tomatoes,common vetch worksbest. A mixture of purple vetch and oats is grownbefore dry beans, and a mix of sorghum-sudangrassand cowpeas precedes safflower.

In order to get maximum biomass and Nproduction by April 1,LANA vetch is best planted earlyenough (6 to 8 weeks before frost) to have goodgrowth before “winter.”Disked in early April,LANA pro-vides all but about 40 lb.N/A to the sweet corn crop.Common vetch, seeded after the corn, can fix most

of the N required by the subsequent tomato crop,with about 30 to 40 lb.N/A added as starter.

A mixture of sorghum-sudangrass and cowpeas isplanted following tomato harvest. The mixtureresponds to residual N levels with N-scavenging bythe grass component to prevent winter leaching.The cowpeas fix enough N for early growth of thesubsequent safflower cash crop,which has relative-ly low initial N demands. The cover crop breaksdown fast enough to supply safflower’s later-seasonN demand.

Full-Year Covers Tackle Tough WeedsTROUT RUN, Pa.—Growing cover crops for afull year between cash crops helps Eric andAnne Nordell control virtually every type ofweed nature throws at their vegetable farm—even quackgrass.

The couple experimented with manydifferent cover crops on their north-centralPennsylvania farm before adapting a systemused to successfully battle quackgrass on a commercial herb farm in the PacificNorthwest. Between cash crops, the Nordellsgrow two winter cover crops to smotherweeds.A brief stint of aggressive summertillage between the two cover crops keepsannual weeds from setting seed.

Regular use of cover crops in their half-acre strips between rows of vegetables alsoimproves soil quality and moisture retentionwhile reducing erosion.“Vegetable cropsreturn very little to the soil as far as a rootsystem,” says Eric, a frequent speaker onconservation practices at conferences in theNortheast.“You cut a head of lettuce and havenothing left behind. Growing vegetables, we’realways trying to rebuild the soil.”

The Nordells’ short growing season—which typically ends with the first frost inSeptember—makes it challenging to squeezein cover crops on their six cultivated acres.

Yellow blossom sweetclover is overseededat 20 to 24 lb./A into early crops such asonions or spring lettuce. Lettuce is overseeded

a week or two after planting but before leavesopen up to trap sweetclover seeds, whileonions are overseeded near harvest.TheNordells walk up and down every other rowwith a manual Cyclone seeder (canvas bagwith a hand-crank spinner).They harvest thecash crop, then let the clover grow throughsummer.

Yellow blossom sweetclover—one of thebest cover crop choices for warm-seasonnitrogen production—puts down a deeptaproot before winter if seeded in June or July, observes Eric.“That root system loosensthe soil, fixes nitrogen, and may even bring up minerals from the subsoil with its long tap root.”He points out that the clover alonewould not suppress weeds.The sole-seedingworks on their farm because of theirsuccessful management efforts over a decade to suppress overall weed pressure by crop rotation and varied cover crops.

In spring, the sweetclover grows until it is about knee-high in mid-May. Then theNordells clip it just before it buds.They let the regrowth bloom to attract pollinators and beneficial insects to the field, beforeclipping it again in July.

In early- to mid-July, the Nordells moldboardplow the sweetclover to kill it.They leave theground in bare fallow, working it again with aspringtooth harrow to hit perennial weeds atthe weakest point of their lifecycle. After that,


▲ 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.

COVER CROPS FOR COTTON PRODUCTION

In what would otherwise be continuous cottonproduction, any winter annual cover crop addedto the system can add rotation benefits, help

maintain soil productivity, and provide 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 ofdefoliant. The dropping leaves mulch the covercrop seed, aiding germination. Rye works better

the couple harrows every two to three weeksto bring weed roots and rhizomes to the soilsurface, where they bake in the summer sun.The harrowing also kills flushes of annualweeds before they can set seed.

After five years in this weed-killing rotation, the Nordells were able to cut backon harrowing, which they now coordinatewith rainfall and weed pressure. In theunusually dry summer of 1997, for example,they did not harrow at all after plowing.

In mid-August, the Nordells plant a second,overwintering cover crop. In this rotation,they seed a mix of rye and hairy vetch.Theybroadcast and lightly incorporate about 80pounds rye and 30 pounds vetch per acre.The rye establishes quickly, putting on goodgrowth both above and below the surface,while the vetch fixes nitrogen.Anothercombination is yellow, red and white clover ina 2:2:1 ratio by volume.“We’re looking for agreen field by Labor Day,”Eric says.“We wanta good sod before we get our first freeze.”

Rye and vetch are a popular combinationto manage nitrogen.The rye takes up excessN from the soil, preventing leaching.Thevetch fixes additional nitrogen which itreleases after it’s killed the following springprior to planting the next cash crop.

With the August seeding, the Nordells’rye/vetch mixture produces most of itsbiomass in fall.

The Nordells plow the rye/vetch mix after it greens up in late March to early April,working shallowly so as not to turn up asmany weed seeds.They forego maximumbiomass and N for earlier planting of theircash crop—tomatoes, peppers, summerbroccoli or leeks—around the end of May.The bare fallow during mid-summer plus early spring incorporation of overwinteringcover crops are the best preventive to slugsand grubs, they have found.

Thanks to their weed-suppressing covercrops, the Nordells typically spend less than10 hours a season hand-weeding their threeacres of cash crops, and never need to hireoutside weeding help.“Don’t overlook thecover crops’ role in improving soil tilth andmaking cultivation easier,” adds Eric. Beforecover cropping, he noticed that their siltysoils deteriorated whenever they grew twocash crops in a row.“When the soil structuredeclines, it doesn’t hold moisture and we get a buildup of annual weeds,”he notes.

The Nordells can afford to forego a cashcrop to keep half their land in cover cropsbecause their tax bills and land value are notas high as market gardeners in a more urbansetting.“We take some land out of production,but in our situation, we have the land,”Ericsays.“If we had to hire people for weedcontrol, it would be more costly.”

See Recommended Resources (p. 162) toorder a video describing this system.


than wheat.Yields are usually equal to, or greaterthan yields in conventional tillage systems withwinter fallow.

Balansa clover, a promising cover crop for theSouth, reseeds well in no-till cotton systems (seeUp-and-Coming Cover Crops, p. 158).

1 Year: Rye/Legume>Cotton. Plant the rye/legume mix in early October, or early enough toallow the legume to establish well before coolerwinter temperatures. Kill by late April, and if soilmoisture permits, no-till plant cotton within threeto five days using tined-wheel row cleaner attach-ments to clear residue. Band-spray normal pre-emergent herbicides over the cleaned and plantedrow area.Cotton will need additional weed controltoward layby using flaming, cultivation or directedherbicides. Crimson clover, hairy vetch, Cahabavetch and Austrian winter peas are effectivelegumes in this system.

Multiyear: Reseeding Legume>No-Till Cotton>Legume>No-Till Cotton. Subterranean clover,Southern spotted burclover, PARADANA balansaclover and some crimson clover cultivars set seedquickly enough in some areas to become perpet-ually reseeding when cotton planting dates arelate enough in spring.Germination of hard seed inlate summer 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 herbicides are 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 as in-field insectary areas to increase overall insectpopulations, resulting in more beneficial insectsto control pest insects.

▲ 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.

DRYLAND CEREAL-LEGUME CROPPING SYSTEMS

Soil moisture availability and use by cover cropsare the dominant concerns in dryland productionsystems. Yet more and more innovators are find-

ANNUAL and PERENNIAL MEDIC cultivars can fix N on low moisture, and can reduce erosion in dryland areascompared with bare fallow between crop seasons.


ing that carefully managed and selected covercrops in their rotations result in increased soilmoisture availability to their cash crops.This deli-cate balance between water use by the covercrop and water conservation will dictate, in part,how cover crops work in your rotation.

Cover crop features: perennial medics per-sist due to hard seed,providing green manure anderosion control; field peas and lentils (grainlegumes) are shallow-rooted yet produce cropsand additional N in years of good rainfall.

An excellent resource describing these rota-tions in detail is Cereal-Legume Cropping

Systems: Nine Farm Case Studies in the DrylandNorthern Plains, Canadian Prairies andIntermountain Northwest. See Appendix C,Recommended Resources (p. 163).

In an area of Montana receiving 11 to 12 inch-es of rainfall per year,where summer fallow is thenorm, some farmers and ranchers are using covercrops and longer rotations to eliminate fallow.Greg Gould believes he can do without summerfallow because his rotation has improved his soil’swater-holding capacity. While most farmers in hisarea think water is the limiting factor, he thinks itis the condition of the soil.

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 can expand to:

Corn>Cover>Soybean>Cover. Most popularchoices are rye or rye/vetch mixture followingcorn; vetch or rye/vetch mixture followingbeans. Broadcast or drill covers immediatelyafter harvest. Hairy vetch needs at least 15days before frost in 60 F soil. Rye will germi-nate as long as soil is just above freezing. Drillfor quicker germination. Consider overseeding at leaf-yellowing if your post-harvest plantingwindow is too short.

If you want to make certain the legume iswell established for maximum spring N andbiomass production, consider adding a smallgrain to your rotation.

Corn>Soybean>Small Grain/Cover. Smallgrains 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 cultivarof 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 incorporating it early in its second season opens up newoptions for cash crops or a second cover crop.

Late-season tomatoes,peppers,vine crops or sweet corn all thrive in the warm,enrichedsoil following a green manure. Two heat-lovingcovers that could be planted after killing a cool-season legume green manure are buckwheat(used to smother weeds,attract beneficialinsects or for grain harvest) and sorghum-Sudangrass hybrid (for quick plow-downbiomass or to fracture compacted subsoil).

These crops would work most places in theCorn Belt. To get started in your area, checkTop Regional Cover Crop Species (p. 47) to fill various roles, or Cultural Traits andPlanting (p. 50) to find which cover crops fit best in your system.


7 to 13 Years: Flax>Winter Wheat>SpringBarley>Buckwheat>Spring Wheat>WinterWheat>Alfalfa (up to 6 years) >FallowSystem 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 the weeds that havebegun cropping up;

• 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 rotation wherea different cash crop or cover crop can be substitut-ed, particularly in response to market conditions.Furthermore, with Angus cattle on the ranch, manyof the crops can be grazed or cut for 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>SpringGrain/Legume Interseed>Legume GreenManure/Fallow>Winter Wheat>SpringWheat>Grain/Legume Interseed>Legume>Legume. In this rotation, one year of winterwheat and two years of spring-seeded crops fol-low a two or three-year legume break. Eachlegume sequence ends with an early summerincorporation of the legume to save moisture fol-lowed by minimal surface tillage to controlweeds. Deep-rooted winter wheat follows sweet-

clover, which can leave topsoil fairly dry. Spring-seeded grains prevent weeds that show up withsuccessive winter grain cycles and have shallowerroots that allow soil moisture to build up deeperin 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 andSIRIUS field peas are water-efficient substitutes forthe deep-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. Low-water use cover crops have been shown to use equal or less soil water thanbare fallow treatment, while adding organic mat-ter and N. Consequently, dryland rotations canhave a significant impact on soils and the fieldenvironment when used over a number of years.

When starting with dryland soil that has raisedthe same crop for many years with conventionalinputs, it will take three to five years of soil-build-ing rotations until soils become biologicallyactive. This is the length of time often cited byfarmers in many regions for soil-based changes totake place. These improved soils have higherorganic matter, a crumbly structure, and goodwater retention and infiltration. They also resistcompaction and effectively cycle nutrients fromresidue to following 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.

CHARTS 43

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 COVER CROPSPECIES

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 willnot be the most successful in all cases within abioregion, and others my 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 providemore seasonal details.The added effect of a nurse

crop 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.Nonlegumes have not been rated fortheir biomass nitrogen content, so this column isleft blank for nonlegumes. Mature nonlegumeresidues also tend to immobilize N.

Dry Matter. A quantitative estimate of therange of dry matter in lb./A/yr., based largely onpublished research.As some of this data is basedon research plots, irrigated systems or multicutsystems, your on-farm result probably would bein the low to midpoint of the dry matter rangecited.This estimate is based on fully dry materi-al. “Dry” alfalfa hay is often about 20 percentmoisture, so a ton 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 cropharvest—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


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 forage.

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 generalfor the species, based on measured results andobservations over a range of conditions.Choice ofcultivar, weather extremes and other factors mayaffect a cover crop’s performance in a given year.

Column headingsAliases. Provides a few common references forthe cover 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, winteror spring cover crop.

SA = Summer Annual. Germinates andmatures without a cold snap and usually toler-ates warm temperatures.

WA = Winter Annual. Would be more cold-tol-erant and would require freezing temperature ora 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

CHARTS 45

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 fall1997. 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. Your

cost 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. 166.

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 pests by suppressing or limiting damage from


nematodes, soil disease from fungal or bacterialinfection, or weeds by natural herbicidal (allelopathic) or competition/smothering action.Researchers report difficulty in conclusivelydocumenting allelopathic activity distinct fromother cover crop effects, and nematicidal impactsare variable, studies show.These are general, ten-tative ratings in these emerging aspects of covercrop influence.

Other. Indicates likelihood of attracting benefi-cial insects,of accommodating field traffic (foot orvehicle) and of fitting growing windows or shortduration.

CHART 4B: POTENTIAL DISADVANTAGES

Increase Pest Risks. Relative likelihood of acover crop becoming a weed,or contributing to a

likely pest risk. Overall, growing a cover croprarely causes pest problems. But certain covercrops occasionally may contribute to particularpest, disease or nematode problems in localizedareas, for example by serving as an alternate hostto the pest. See the 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.

CHARTS 47

Northeast red cl,hairy v, ryegrs, swt cl, rye, ryegrs, sorghyb, sorghyb, rye,berseem, sorghyb, wht cl, swt cl ryegrs, rye, sorghyb

swt cl rye oats buckwheat

Mid-Atlantic hairy v, red cl, ryegrs, rye, wht cl, sorghyb, rye, ryegrs, rye,berseem, swt cl, cowpeas, swt cl oats, sorghybcrim cl sorghyb rye, ryegrs buckwheat

Mid-South hairy v, sub cl, ryegrs, rye, wht 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, wht cl, sorghyb, buckwheat, rye,berseem, sorghyb, cowpeas, rye, swt cl ryegrs, sub cl, sorghybcrim cl swt cl ryegrs rye

Southeast Lowlands winter peas, ryegrs, wht cl, sorghyb, berseem, rye, rye,sub cl,hairy v, rye, cowpeas, swt cl wheat sorghyb

berseem, sorghyb, rye, cowpeascrim cl sub cl sorghyb oats

Great Lakes hairy v, red cl, ryegrs, rye, oats, sorghyb, berseem, rye,berseem, sorghyb, rye, swt cl ryegrs, rye, sorghybcrim cl swt cl ryegrs oats

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 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,hairy v medic barley swt cl barley sorghyb

Inland Northwest winter peas, medic, swt cl, rye, sorghyb, rye,wheat, rye,hairy v rye,barley barley swt cl barley sorghyb

Northwest Maritime berseem, ryegrs, rye, wht cl, rye, sorghyb, ryegrs, ryesub cl, lana v, sorghyb, ryegrs, swt cl lana v,oats,

crim cl lana v barley wht cl

Coastal 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 rye

Southwest 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. 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 vetch=LANA woollypod vetch.


Chart 2

PERFORMANCE AND ROLESLegume Total N Dry Matter N Soil Erosion Weed Good Quick

Species N Source (lb./A)1 (lb./A/yr.) Scavenger2 Builder3 Fighter4 Fighter Grazing5 Growth

Annual ryegrass p. 55 2,000–9,000

Barley p. 58 3,000–10,000

Oats p. 62 2,000–10,000

Rye p. 65 3,000–10,000

Wheat p. 72 3,000–7,000

Buckwheat p. 77 2,000–3,000

Sorghum–sudan. p. 80 8,000–10,000

Berseem clover p. 87 75–220 6,000–10,000

Cowpeas p. 95 100–150 2,500–4,500

Crimson clover p. 100 70–130 3,500–5,500

Field peas p. 105 90–150 4,000–5,000

Hairy vetch p. 112 90–200 2,300–5,000

Medics p. 119 50–120 1,500–4,000

Red clover p. 127 70–150 2,000–5,000

Subterranean clover p. 132 75–200 3,000–8,500

Sweetclovers p. 139 90–170 3,000–5,000

White clover p. 147 80–200 2,000–6,000

Woollypod vetch p. 151 100–250 4,000–8,000

1Total N—Total N from all plant. 2N Scavenger—Ability to take up/store excess nitrogen. 3Soil Builder—Organic matter yield andsoil structure improvement. 4Erosion Fighter—Soil-holding ability of roots and total plant. 5Good Grazing—Production, nutritionalquality and palatability.

=Poor; =Fair; =Good; =Very Good; =Excellent

NO

NL

EG

UM

ES

LE

GU

ME

S

CHARTS 49

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 crop will 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 boosts dry matter significantly.

Barley Tolerates moderately alkaline conditions but does 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 root penetration.

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 seasonal adaptability.

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 of seeddrop; overgrazing can be toxic.

F* S*

NO

NL

EG

UM

ES

LE

GU

ME

S


Chart 3A

CULTURAL TRAITSHardy Tolerances Min.

through pH Best Germin. Species Aliases Type1 Zone2 Habit3 (Pref.) Established4 Temp.

heat

drou

ght

shad

e

flood

low fe

rt

Annual ryegrass p. 55 Italian ryegrass WA 6 U 6.0–7.0 Esp, LSu,EF, F

Barley p. 58 WA 7 U 6.0–8.5 F,W, Sp

Oats p. 62 spring oats CSA 8 U 4.5–6.5 LSu, ESPW in 8+

Rye p. 65 winter, cereal, CSA 3 U 5.0–7.0 LSu-F 34For grain rye

Wheat p. 72 WA 4 U 6.0–7.5 LSu, F

Buckwheat p. 77 SA NFT U to 5.0–7.0 Sp to LSu 50FSU

Sorghum–sudan. p. 80 Sudax SA NFT U 6.0–7.0 LSp, ES 65F

Berseem clover p. 87 BIGBEE, SA,WA 7 U to 6.2–7.0 ESp, EF 42Fmulticut SU

Cowpeas p. 95 crowder peas, SAL NFT SU/C 5.5–6.5 ESu 58Fsouthern peas

Crimson clover p. 100 WA, SA 7 U/SU 5.5–7.0 LSu/ESu

Field peas p. 105 winter peas, WA 7 C 6.0–7.0 F, ESp 41Fblack peas

Hairy vetch p. 112 winter vetch WA/CSA 4 C 5.5–7.5 EF, ESp 60F

Medics p. 119 SP/SA 4/7 P/Su 6.0–7.0 EF, ESp, ES 45F

Red clover p. 127 SP, B 4 U 6.2–7.0 LSu; ESp 41F

Subterranean cl. p. 132 subclover CSA 7 P/SP 5.5–7.0 LSu, EF 38F

Sweetclovers p. 139 B/SA 4 U 6.5–7.5 Sp/S 42F

White clover p. 147 white dutch LP/WA 4 P/SU 6.0–7.0 LW, E to 40Fladino LSp, EF

Woollypod vetch p. 151 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

PLANTINGCost Cost/A Inoc.

Species Depth Seeding Rate ($/lb.)1 (median)2 Type Reseeds3

Annual ryegrass 0–1/2 5–10 .2–.4 15–30 .6–1.25 1 .50 3.75 11.25 R

Barley 3/4–2 50–100 1–2 80–125 1.6–2.5 3-5 .05–.20 9.38 12.81 S

Oats 1/2–2 80–110 2.5–3.5 110–140 3.5–4.5 4–6 .10–.20 14.25 18.75 R

Rye 3/4–2 60–120 1-2 90–160 1.5–3.0 4–6 .05–.20 6.75 9.38 R

Wheat 1/2–11/2 60–120 1–2 60–150 1–2.5 3–6 .05–.25 13.50 15.75 S

Buckwheat 1/2–1.5 48–70 1–1.4 60–96 1.2–1.5 3–4 .28–.70 29– 38– R

Sorghum-sudangrass 1/2-1.5 35 1 40–50 1–1.25 2 .21–.66 15.05 19.35 S

Berseem clover 1/4–1/2 8–12 15–20 2 1.50 15.00 27.00 crimson, Nberseem

Cowpeas 1–11/2 30–90 70–120 5 .50 30 47.50 cowpeas, Slespedeza

Crimson clover 1/4–1/2 15-20 22–30 2–3 1.50 26 39 crimson, Rberseem

Field peas 11/2–3 50–80 90–100 4 .25 16.25 26.25 pea, vetch S

Hairy vetch 1/2-11/2 15–20 25–40 2 1.25 22 41 pea, vetch S

Medics 1/4–1/2 8–22 12–26 2/3 1.50 22.50 28.50 annual Rmedics

Red clover 1/4–1/2 8–10 10–12 3 1.85 16.65 20.35 red cl, Swht cl

Subterranean clover 1/4–1/2 10–20 20–30 3 2.50 37.50 62.50 clovers, Rsub, rose

Sweetclovers 1/4–1.0 6–10 10–20 1.5 .70 5.60 10.50 alfalfa, Rswt cl

White clover 1/4–1/2 3–9 5–14 1.5 3.10 18.60 29.50 red cl, Rwht cl

Woollypod vetch 1/2–1 10–30 30–60 2-3 1.05 21 47.25 pea, vetch R,S

Drilledlb./A bu/A lb./A bu/A

Broadcastoz./100 ft2

drilled broadcast

1Per pound in 50-lb. bags as of summer/fall 1997; legumes especially subject to price changes due to supply variability.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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Chart 4A

POTENTIAL ADVANTAGESSoil Impact Soil Ecology Other

Frees Loosen choke attract bears shortSpecies subsoiler P&K Topsoil nematodes disease allelopathic weeds beneficials traffic windows

Annual ryegrass p. 55

Barley p. 58

Oats p. 62

Rye p. 65

Wheat p. 72

Buckwheat p. 77

Sorghum–sudangrass p. 80

Berseem clover p. 87

Cowpeas p. 95

Crimson clover p. 100

Field peas p. 105

Hairy vetch p. 112

Medics p. 119

Red clover p. 127

Subterranean clover p. 132

Sweetclovers p. 139

White clover p. 147

Woollypod vetch p. 151


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CHARTS 53

Chart 4B

POTENTIAL DISADVANTAGESIncrease Pest Risks Management Challenges

Species Comments Pro/Con

Annual ryegrass If mowing, leave 3-4" to ensure regrowth.

Barley Can be harder than rye to incorporate when mature.

Oats Cleaned, bin-run seed will suffice.

Rye Can become a weed if tilled at wrong stage.

Wheat Absorbs N and H20 heavily during stem growth, so kill before then.

Buckwheat Buckwheat sets seed quickly.

Sorghum–sudangrass Mature, frost-killed plants become quite woody.

Berseem clover Multiple cuttings needed to achieve maximum N.

Cowpeas Some cultivars, nematode resistant.

Crimson clover Good for underseeding, easy to kill by tillage or mowing.

Field peas Susceptible to sclerotinia in East.

Hairy vetch Tolerates low fertility, wide pH range,cold or fluctuating winters.

Medics Perennials easily become weedy.

Red clover Grows best where corn grows well.

Subterranean clover Cultivars vary greatly.

Sweetclovers Mature plants become woody.

White clover Can be invasive; survives tillage.

Woollypod vetch Hard seed can be problematic;resident vegetation eventually displaces.

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1Symbols, this page only: =Could be a major problem. =Could be a moderate problem. =Could be a minor problem.

=Occasionally a minor problem. =Rarely a problem

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Most of the commonly used nonlegume covercrops are grasses. These include:• Annual cereals (rye, wheat, barley, oats)• Annual or perennial forage grasses such as

ryegrass• Warm-season grasses like sorghum-sudangrass

Grass cover crops are most useful for:• Scavenging nutrients—especially N—left over

from a previous crop• Reducing or preventing erosion• Producing large amounts of residue, and

adding 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.

Perennial and warm-season forage grasses alsocan 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 theground 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.

Grass cover crops are higher in carbon thanlegume cover crops.The high carbon content ofgrasses means that they will break down moreslowly than legumes, resulting in longer-lastingresidue. As grasses mature, the carbon-to-nitrogenratio (C:N) increases. This has two tangible

OVERVIEW OF NONLEGUME COVER CROPS

results: The higher carbon residue is harder forsoil microbes 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 Nfrom the previous crop,as they mature the N is lesslikely to be released for use by a crop grown imme-diately after the grass cover crop. As an example ofthis, think of how long it takes for straw to decom-pose in the field.Over time,the residue does breakdown and nutrients are released. In general, thisslower decomposition and the higher carbon con-tent of grasses can lead to increased soil organicmatter, compared to legumes.

Grass cover crops can produce a lot of residue,which contributes to their ability to prevent ero-sion and suppress weeds while they are growingor when left on the soil surface as a mulch.

Although grasses contain some nitrogen intheir plant tissues, grass cover crops generally arenot significant sources of N for your cropping sys-tem.They do, however, keep excess soil N fromleaching, and prevent the loss of soil organic mat-ter through erosion.

Management of grasses in your cropping sys-tem may involve balancing the amount of residueproduced with the possibility of tying up N formore 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 indetail in its own section (p. 77). Buckwheat isusually classed as a non-grass coarse grain.Whileit is managed like a quick-growing grain, its has a succulent stem, large leaves and whiteblossoms.

ANNUAL RYEGRASS 55

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. 47 to 53, for rankingand management summary.

soil tilth.Rapid aboveground growth helps supplyorganic matter. Expect about 4,000 to 6,000 lb.dry matter/A on average with a multicut regimen,climbing as high as 9,000 lb.DM/A over a full fieldseason with high moisture and fertility.

Weed suppressor. Mixed with legumes orgrasses, annual ryegrass usually establishes firstand improves early-season weed control. Withadequate moisture, it serves well in HardinessZone 6 and warmer as a living mulch in high-value systems where you can mow it regularly. Itmay winterkill 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 leaching overwinter. Its extensive, fibrous root system can takeup as much as 43 lb.N/A,a University of Californiastudy showed (367). It took up about 60 lb. N/A by mid-May following corn in a Maryland study.Cereal rye scavenged the same amount of N bymid-April on this silt loam soil (307).

Nurse/companion crop. Ryegrass helps slow-growing, fall-seeded legumes establish and over-

ANNUAL RYEGRASS

If you want mellower 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 soilstructure 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 crop quality.You also can overseed ryegrass readily into corn,soybeans and many high-value crops.

BENEFITS

Erosion fighter. Ryegrass has an extensive,soil-holding root system. The cover crop estab-lishes quickly even in poor, rocky or wet soils andtolerates some flooding once established.It’s well-suited for field strips, grass waterways or exposedareas. “An added bonus: It keeps you out of themud at harvest,” says Pennsylvania grower BobHofstetter.

Soil builder. Ryegrass’s dense yet shallow rootsystem improves water infiltration and enhances


winter in the northern U.S., even if the ryegrasswinterkills. It tends to outcompete legumes in theSouth.Ryegrass also is a very palatable forage.Youcan extend the grazing period in late fall and earlyspring by letting livestock graze cover crops ofryegrass or a ryegrass-based mix.

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 (350).

Annual ryegrass has a biennial tendency in coolregions. If it overwinters, it will regrow quicklyand produce seed in late spring. Although fewplants survive more than a year, this reseedingcharacteristic can create a serious weed problemin some areas, such as the mid-Atlantic (82).

Establishment & FieldworkAnnual ryegrass germinates and establishes welleven in cool soil (350).Broadcast seed at 15 to 30lb./A.You needn’t incorporate seed when broad-casting onto freshly cultivated soil—the firstshower ensures seed coverage and good germina-tion. Cultipacking can reduce soil heaving,

however, especially with late-fall plantings. Drill 5to 10 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 andother ryegrass species, so don’t expect a purestand 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 (150).

If aerially seeding, increase rates at least 30 per-cent (12). You can overseed into corn at lastcultivation or later (consider adding 5 to 10pounds of red or white clover with it) or plantright after corn silage harvest.Overseed at leaf-yel-lowing or later for dense-canopy crops such assoybeans (147, 150). When overseeding intosolanaceous crops such as peppers, tomatoes andeggplant, wait until early to full bloom.

Spring seeding. Sow ryegrass right after anearly-spring vegetable crop, for a four- to eight-week summer period before a fall vegetable crop (302).

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.Seed the legume at about two-thirds its normalrate. Adequate P and K levels are important whengrowing annual ryegrass with a legume.

In vineyards,a fall-seeded,50:50 mix of ryegrassand crimson clover works well, some Californiagrowers have found (167).

Although not a frequent pairing, drilling rye-grass in early spring at 20 lb./A with an oats nursecrop or frost seeding 10 lb./A into overwinteredsmall grains can provide some fine fall grazing.Frost seeding with red clover or other large-seed-ed, cool-season legumes also can work well.

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 to

ANNUAL RYEGRASS (Lolium multiflorum)

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prolonged heat, cold or drought.That’s rarely thecase in Zone 5 and colder, however, whereclimate 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 arelatively late maturing plant, so in vineyards it may use excessive water and N if left too long (168).

Killing & ControllingYou can kill annual ryegrass mechanically by disk-ing or plowing, preferably during early bloom(usually in spring), before it sets seed (302, 351).Mowing may not kill ryegrass completely (77).You also can kill annual ryegrass readily with non-persistent contact herbicides such as glyphosateor paraquat.When soil moisture conservation is aprimary objective of the killed surface residue,paraquat would be better because it kills fast andconserves more moisture (82).

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 (302). It often volunteers invineyards or orchards if there is high fertility andmay require regular mowing to reduce competi-tion with vines (351).A local weed managementspecialist may be able to recommend a herbicidethat can reduce ryegrass germination if the coveris becoming a weed in perennial grass stands.Chlorsulfuron is sometimes used for this purposein California (351).

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 rust.Look for resistant, regionally adapted varieties.Annual ryegrass also can host high densities of pinnematodes (Paratylenchus projectus) andbromegrass mosaic virus, which plant-parasiticnematodes (Xiphinema spp.) transmit (351).

Other OptionsRyegrass provides a good grazing option that canextend the grazing season for almost any kind oflivestock. Although very small-seeded, ryegrassdoes not tiller heavily, so seed at high rates if youexpect a ryegrass cover crop also to serve as a pas-ture. Some varieties tolerate heat fairly well andcan persist for several years under sound grazingpractices that allow the grass to reseed.

As a hay option, annual ryegrass can provide2,000 to 6,000 pounds of dry forage per acre,depending on moisture and fertility levels (351).For highest quality hay, cut no later than the earlybloom stage and consider growing it with alegume.

When using ryegrass for grass waterways andconservation strips on highly erodible slopes,applying 3,000 to 4,000 pounds per acre of strawafter seeding at medium to high rates can helpkeep soil and seed in place until the stand estab-lishes (351).

Management CautionsRyegrass is a heavy user of moisture and N. Itperforms poorly during drought or long periodsof high or low temperature, and in low-fertilitysoils. It can compete heavily for soil moisturewhen used as living mulch. It also can become aweed problem (302).

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

Seed sources. Widely available.


Hordeum vulgare

Type: cool season annual cerealgrain

Roles: prevent erosion, suppressweeds, scavenge excess nutrients,add organic matter

Mix with: annual legumes orgrasses, perennial ryegrass


Nutrient recycler. Considered a light N feeder,barley captured 32 lb. N/A as a winter cover cropfollowing a stand of fava beans (Vicia faba) in aCalifornia study,compared with 20 lb./A for annu-al ryegrass. A barley cover crop reduced soil N an average of 64 percent at eight sites throughoutNorth America that had received an average of107 lb. N/A (213). Intercropping barley with fieldpeas (Pisum sativum) can increase the amountof N absorbed by barley and returned to the soilin barley residue, other studies show (172, 175).Barley improves P and K cycling if the residueisn’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, alongwith its thick root system, can improve soilstructure and water infiltration (219, 367). InCalifornia cropping systems, cultivars such asUC476 or COSINA can produce as much as 12,900lb. biomass/A.

Nurse crop. Barley has an upright posture andrelatively open canopy that makes it a fine nurse

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 atopsoil-protecting crop during droughty condi-tions in any region.

It’s a fine choice for reclaiming overworked,weedy or eroded fields, or as part of a cover cropmix for improving soil tilth and nutrient cycling inperennial cropping systems in Hardiness Zone 8or warmer.

Barley prefers cool,dry growing areas. A springcover crop,it can be grown farther north than anyother cereal grain, largely because of its shortgrowing period.It also can produce more biomassin a shorter time than any other cereal crop (219).

BENEFITS

Erosion control. Use barley as an overwinteringcover crop for erosion control in Zone 8 andwarmer, including much of California, westernOregon and western Washington. It’s well-suitedfor vineyards and orchards, or as part of a mixedseeding.

As a winter annual, barley develops a deep,fibrous root system.The roots can reach as deep as 6.5 feet. As a spring crop, barley has a compara-tively shallow root system but holds soil strongly tominimize erosion during droughty conditions (51).

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crop for establishing a forage or legume stand.Less competitive than winter grains, barley alsouses less water than other covers. In weedy fields,wait to broadcast the forage or legume until afteryou’ve mechanically weeded barley at the four- orfive-leaf stage to reduce weed competition.

As an inexpensive,easy-to-kill companion crop,barley can protect sugarbeet seedlings duringtheir first two months while also serving as a soilprotectant during droughty periods (detailsbelow).

Pest suppression. Barleycan reduce incidence ofleafhoppers, aphids, army-worms, root-knot nematodesand other pests, a number ofstudies suggest.

MANAGEMENT

Establishment & FieldworkBarley establishes readily in prepared seedbeds. Itprefers adequate but not excessive moisture anddoes poorly in waterlogged soils. It grows best inwell-drained, fertile loams or light, clay soils inareas having cool, dry, mild winters. It also doeswell on light, droughty soils and tolerates some-what alkaline 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 to2 bushels) from 3/4 to 2 inches deep into a pre-pared seedbed. Hoe or furrow-type drills withdisk- or double-disk openers work well in aridregions without irrigation.

If broadcasting, prepare the seedbed with atleast 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 50pounds) 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 (51).

Winter annual use. For an overwintering covercrop in Zone 8 or warmer, plant barley fromSeptember through February. Plantings beforeNovember 1 generally fare best, largely due towarmer soil conditions. Elsewhere, winter vari-eties might overwinter only in mild areas withadequate snow cover.

Expect mixed results if trying to use barley as aself-reseeding cover crop.Weather variations,mow-ing regimes and the return of native or resident

vegetation tend to reducebarley’s reseeding capabili-ty. Expect to resow periodi-cally,perhaps annually.

Mixed seedings. Barleyworks well in mixtures withother grasses or legumes. Inlow-fertility soils or whereyou’re trying to minimize

tie-up of soil nitrogen, growing barley with one ormore legumes can be helpful. Your seeding costper pound will increase, but the reduced seedingrate can offset some of this. A short-seasonCanadian field pea such as TRAPPER would be agood companion, or try an oat/barley/pea mix,suggests organic farmer Jack Lazor,Westfield,Vt.

In northern California, Phil LaRocca (LaRoccaVineyards, Forest Ranch, Calif.) lightly disks hisupper vineyard’s soil before broadcasting a mixof barley, fescue, brome, LANA vetch, and crim-son, red and subterranean clovers,usually duringOctober. He seeds at 30 to 35 lb./A, with 10 to 20 percent being barley. “I’ve always added more barley to the seeding rate than recom-mended. More is better, especially with barley,if you want biomass and weed suppression,”he says.

After broadcasting, LaRocca covers erosion-prone areas with 2 tons of rice straw per acre,which is “$1 cheaper per bale than oat straw hereand has fewer weed seeds,” he notes.“The strawdecomposes quickly and holds seed and soilwell.” Besides contributing to soil humus (as thecover crop also does), the straw helps keep theseedbed warm and moist. That can be veryhelpful in LaRocca’s upper vineyard, where itsometimes snows in winter.

A fast-growing barley can be grown farther north andproduce more biomass in ashorter time than any othercereal grain.


In his other, less-erodible vineyard, LaRoccadisks up the cover vegetation, then runs a harrowquickly on top of the disked alleyways to set aseedbed before broadcasting and cultipacking asimilar mix of cover crops.

Field ManagementAlthough barley absorbs a lot of water in its earlystages,it uses moisture more efficiently than othercereals and can be grown without irrigation.About half the commercial barley acreage in dry-land areas is irrigated, however. California crop-ping systems that include barley tend to beirrigated as well. Low seeding rates won’t neces-sarily conserve moisture, as vegetative growthoften increases.

LaRocca hasn’t had any moisture problems orgrape-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 is

deeper and much more competitive than a typicalcover crop’s root system,”he observes.

Mowing can postpone and prolong barleyflowering, as with other cereal grains. As a spring cover, barley puts on biomass quickly, soyou can kill it in plenty of time for seeding afollowing crop. If you want barley to reseed,don’tmow until most of the stand has headed and seedis about to fall off.

To encourage reseeding of his cover mix, PhilLaRocca 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 orcrop competition when intercropped, however,plant a lighter stand, suggests Alan Brutlag,Wendell, Minn. During droughty conditions, hebroadcasts 25 to 30 pounds of barley per acre asa soil-protective companion crop for sugarbeetseedlings. The low-density stand is easy to stunt or kill a month later with the combination ofherbicides and crop oil that he uses for weedcontrol in his sugarbeets.Another control optionis a single application of a herbicide labeled forgrass control (37).

KillingKill barley with a grass herbicide in late spring,orby disking or mowing at the mid- to late-bloomstage 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 beenshown to inhibit germination and growth ofwhite mustard (196).These exudates also protect

BARLEY (Hordeum vulgare)

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barley plants from fungus, armyworm larvae,bacteria and aphids (197, 374).

Barley seems to reduce the incidence of grapeleafhoppers in vineyards and increase levels of beneficial spiders, one California growerobserved (167). 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 (366).

Cutworms and other small grain pests can beoccasional 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 makesbarley more prone to fungus and disease. Assum-ing adequate soil moisture, shallow seeding canhasten emergence and lessen incidence of root rotdisease, if this has been a problem in your area(325). Varieties resistant to leaf diseases are avail-able. Two-rowed varieties are more resistant to leaf rust and mildew. Also avoid planting barleyafter wheat.

If nematodes are likely to be a problem, plantlate 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 (191.1).

Other OptionsBarley can be grazed lightly in winter or spring orcut for hay/haylage (147). It has greater foragenutritive value than oats, wheat or triticale. It alsocan be grown as a specialty grain for malting,soups, bread and other uses. As a feed grain (in ahog ration, for example), it can replace somecostlier 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 (325).

• Barley tolerates alkaline soils better than anyother cereal.

• Winter cultivars are less winterhardy than win-ter wheat, triticale or cereal rye.

SEED

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-rowed types have more symmetrical kernels andare more disease-resistant (e.g. leaf rust andmildew) than six-rowed types, in which two-thirds of the lateral rows of the spike are smallerand twisted.



If you need a low-cost, reliable fall cover thatwinterkills in Hardiness Zone 6 and colder andmuch of Zone 7, look no further. Oats provide

quick, weed-suppressing biomass, take up excesssoil nutrients and can improve the productivity oflegumes when planted in mixtures. The cover’sfibrous root system also holds soil during cool-weather gaps in rotations,and the ground cover pro-vides a mellow mulch 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. Seeding (whether broadcasting ordrilling), labor, equipment and management costsfor a fall oat stand averaged less than $40/A for agroup of northwestern Washington growers in arecent study. Budgets for seeding cereal cover

crops look even better in the southeastern U.S.,generally about $25 per acre (287).

Nutrient catch crop. Oats take up excess N andsmall amounts of P and K when planted earlyenough. 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 (252, 268).

Where the plant winterkills, some farmers useoats as a nitrogen catch crop after summerlegume plowdowns, to hold some legume N overwinter without needing to kill the cover in spring.Some of that N disappears by spring, eitherthrough denitrification into the atmosphere or byleaching from the soil profile. Consider mixingoats with an overwintering legume if spring nitro-gen is your main concern.

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(see below)—for a few weeks. Reduce crop sup-pression concerns by waiting three weeks afterkilling oats before planting a subsequent crop.

Fall legume nurse crop. Oats have few equalsas a legume nurse crop or companion crop.They

OATS

nonsummer use CSA

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 orother legumes


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can increase the fertilizer replacement value oflegumes, studies have shown. Adding about 35 to 75 lb. oats/A to the seeding mix helps slow-establishing legumes such as hairy vetch, cloversor winter peas, while increasing biomass. It alsohelps reduce fall weeds. The oats will winterkill in many areas while improving the legume’swinter 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 could pose a nitrate-poison-ing threat, especially if you delayharvesting until oats are nearingthe flowering stage.

The climbing growth habit ofsome viny legumes such as vetchcan contribute to lodging andmake oat grain harvest difficult.If you’re growing the legume for seed, the oatscan serve as a 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 planting intoheavy residue. 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) at least 40 to 60 days before your area’s first killing frost. Assuming adequate moisture forquick germination,the stand should provide somesoil-protecting, weed-suppressing mulch.

One low-cost seeding method is to set the com-bine so it blows the lightweight oats out the backat about 2 to 4 bushels per acre. Disk lightly toincorporate. In many regions, you’ll have theoption of letting it winterkill or sending in cattlefor 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 2 inches when growing grain you plan to harrow for weed control.Whenseeding into residue, a good no-till drill can savetime and also provide a firm seedbed thatlegumes like (102).

Shallow seeding in moist soil provides rapidemergence and reduces incidence of root rot dis-ease. Drilling spring oats in fall can provide

seedlings with slightly more frostresistance than broadcasting andcould extend the growing seasona bit if you can’t fit in a late-summer seeding.

Timing is critical when youwant plenty of biomass or athick ground cover. Overseeding

the large-seeded oats into a standing crop orheavy residue could be difficult. As a wintercover following soybeans in the Northeast orMidwest, however, overseeding spring oats atthe leaf-yellowing or early leaf-drop stage (andwith little residue present) can give a combinedground cover as high as 80 percent throughearly winter (156). If you wait until closer to orafter soybean harvest, however, you’ll obtainmuch less oat biomass to help retain beanresidue, Iowa and Pennsylvania studies haveshown.

Delaying planting by as little as two weeks in late summer also can reduce the cover’seffectiveness as a spring weed fighter, a study inupstate New York showed. By spring, oat plotsthat had been planted on August 25 had 39percent fewer weed plants and one-seventh the weed biomass of control plots with no oat cover, while oats planted two weeks laterhad just 10 percent fewer weed plants in springand 81 percent of the weed biomass of controlplots (268, 269).

Oats are a reliable,low-cost cover thatwinterkill in Zone 6and much of Zone 7.


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-tillagesystems.

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. When oats are grown as a greenmanure and weed suppressor before an annualcash crop, kill the oat stand by mowing or spray-ing soon after the vegetative stage, such as the

milk or soft dough stage.Killing too early reducesthe biomass potential and you could see someregrowth.But waiting too long could make tillageof the heavier growth more difficult in a conven-tional tillage system and could deplete soil mois-ture needed for the next crop.Timely killing alsois important because well-established or matureoat stands can tie up nitrogen.

If you want to incorporate the stand, allow atleast two to three weeks before planting the nextcrop. You can mow the oats for mulch if you’renot concerned that it might slow soil warming.

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 incorporation beforeseeding a susceptible crop, or by following withan alternate crop. Rotary hoeing or other pre-emerge mechanical weeding of solo-seeded oatscan improve annual broadleaf control.

Oats are less prone to insect problemsthan wheat or barley. If you’re growing oats forgrain or forage, armyworms, various grain aphidsand mites, wireworms, cutworms, thrips, leaf-hoppers, grubs and billbugs could presentoccasional problems.

Resistant oat varieties can minimize rusts,smuts and blights if they are a concern in your areaor for your cropping system. Cover crops such asoats help reduce root-knot nematodes andvegetable crop diseases caused by Rhizoctonia,preliminary results of a producer study in SouthCarolina show (369). To reduce harmful nema-todes that oats could encourage, avoid plantingoats two years in a row or after nematode-susceptible small grains such as wheat, rye ortriticale (51).

Other OptionsThere are many low-cost, regionally adapted andwidely available oat varieties, so you have hay,straw, forage or grain options. Select for

OATS (Avena sativa)

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cultural 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 (287). See Up-and-ComingCover Crops (p. 158).

Aside from their value as a cover crop, oats area great feed supplement, says grain and hogfarmer Carmen Fernholz, Madison, Minn. A nichemarket for organic oats also could exist in yourarea, he observes.

Oats are more palatable than rye and easilyovergrazed. If using controlled grazing in oatstands, watch for high protein levels, which canvary from 12 to 25 percent (356).The potassiumlevel of oat hay also is sometimes very high andcould cause metabolic problems in milking cows

if it’s the primary forage (176). Underseeding alegume enhances the forage option for oats byincreasing the biomass (compared with solo-cropped oats) and providing nitrogen for a subse-quent crop.

COMPARATIVE NOTES

• Fall brassicas grow faster, accumulate more Nand may suppress weeds 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 isbarley, but require more moisture.


Secale cereale

Also called: cereal rye, winter rye,grain rye

Type: cool season annual cerealgrain

Roles: take up excess N, preventerosion, add organic matter,suppress weeds, companion crop

Mix with: legumes, grasses or othercereal grains


pression. Inexpensive and easy to establish, ryeoutperforms all other cover crops on infertile,sandy or acidic soil or on poorly prepared land. Itis widely adapted,but grows best in cool, temper-ate zones or high altitudes.

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-


Taller and quicker-growing than wheat, rye canserve 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 mowing or herbicides. Pair rye with a winterannual legume such as hairy vetch to offset rye’stendency 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(351). Early seeding is better than late seeding forscavenging N (30).• A Maryland study credited rye with holding

60 percent of the residual N that could haveleached from a silt loam soil followingintentionally over-fertilizedcorn (307).

• A Georgia study estimated ryecaptured from 69 to 100 per-cent of the residual N after acorn crop (177).

• In an Iowa study, overseedingrye or a rye/oats mix into soybeans in Augustlimited leaching loss from September to Mayto less than 5 lb. N/A (252).Rye increases the concentration of exchange-

able potassium (K) near the soil surface, by bring-ing it up from lower in the soil profile (94).

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 conservation tillagepractices, rye provides soil protection on slopingfields and holds soil loss to a tolerable level (95).

Fits many rotations. In most regions, rye canserve as an overwintering cover crop after corn

or 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 andwindbreak within vegetables or fruit crops and as a quick cover for rotation gaps or if anothercrop fails.

You can overseed rye into tasseling or silkingcorn with consistently good results.You also canoverseed rye into brassicas (304, 351), into soy-beans just before leaf drop or between pecan treerows (43).

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 (302). Arye cover crop might yield too much residue,

depending on your tillage system,so be sure your planting regime forsubsequent crops can handle this.

Rye overseeded into cabbageAugust 26 covered nearly 80 per-cent of the between-row plots bymid-October and, despite some

summer heat,already had accumulated nearly halfa ton of biomass per acre in a New York study. Bythe May 19 plowdown, rye provided 2.5 tons ofdry matter per acre and had accumulated 80 lb.N/A. Cabbage yields weren’t affected, so competi-tion wasn’t a problem (268).

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 (300) and has been shown to inhibit germina-tion of some triazine-resistant weeds (275).

Rye reduced total weed density an average of78 percent when rye residue covered more than90 percent of soil in a Maryland no-till study

Rye can be plantedlater in fall thanother cover crops.

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(339), and by 99 percent in a California study(351). You can increase rye’s weed-suppressingeffect before no-till corn by planting rye with an annual legume such as hairy vetch (82).

Pest suppressor. While rye is susceptible to thesame insects that attack other cereals, seriousinfestations are rare.Rye reduces insect pest prob-lems in rotations (369) and attracts significantnumbers of beneficials such as lady beetles (38).

Fewer diseases affect rye than other cereals.Rye can help reduce root-knot nematodes andother harmful nematodes, research in the Southsuggests (14, 369).

Companion crop/legume mixtures. Sow rye with legumes or other grasses in fall or overseed a legume in spring. A legume helps off-set rye’s tendency to tie up N. A legume/rye mix-ture adjusts to residual soil N levels. If there’splenty of N, rye tends to do better; if there isinsufficient N, the legume component growsbetter, Maryland research shows (59). Hairyvetch and rye are a popular mix, allowing an N credit before corn of 50 to 100 lb. N/A.Rye also helps protect the less hardy vetchseedlings through winter.

Rye Smothers Weeds Before SoybeansAn easy-to-establish rye cover crop helpsNapoleon, Ohio, farmer Rich Bennett enrichhis sandy soil while trimming input costs inno-till soybeans. Bennett broadcasts rye at 2bushels per acre on corn stubble in lateOctober. He chops the cornstalks after ryeseeding to ensure easy bean planting andcultivation in spring.

Bennett doesn’t incorporate rye seed,having found that it germinates well on thesoil surface under the chopped cornstalks. Itusually breaks through the ground but showslittle growth before winter dormancy. Seededearlier in fall, rye would provide more residuethan Bennett prefers by bean planting—andmore effort to kill the cover. “Even if I don’tsee any rye in fall, I know it’ll be there inspring, even if it’s a cold or wet one,”he says.

By mid-May, the rye is usually at least 2.5feet tall and hasn’t started heading.“If it’sshorter than 15 to 18 inches, rye won’t do a good enough job of shading out broadleafweeds,”notes Bennett, who likes how ryesuppresses foxtail, pigweed and lambsquarters.

He sprays the rye with herbicide and no-tillsbeans at 70 pounds per acre on 30-inch rowsin a single pass to minimize rye knockdownfrom field equipment.“I kill the rye with 1.5pints of Roundup per acre—about half the

recommended rate—and sometimes add 1 quart of Lasso to control nightshade. Adding1.7 pounds of ammonium sulfate and 13ounces of surfactant per acre makes it easierfor Roundup to penetrate rye leaves,”heexplains.

The cover dies in about two weeks.Theslow kill helps rye suppress weeds whilesoybeans establish. In this system, Bennettdoesn’t have to worry about rye regrowing.

He usually cultivates beans twice, using a Buffalo no-till cultivator that handles ryeresidue easily. Bennett figures the rye saveshim $15 to $30 per acre in material costs and fieldwork, compared with conventionalno-till systems 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,”hesays.“Rye reduces our winter wind erosion,improves soil structure, conserves soilmoisture and reduces runoff.”Although hefigures the rye’s restrained growth (from the late fall seeding) provides only limitedscavenging of leftover N, any that it doesabsorb and hold overwinter is a bonus.


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. (44.1)

Rye can establish in very cool weather. It willgerminate at temperatures as low as 34 F.Vegetative growth requires 38 F or higher (302).

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 UpperMidwest and cool New England states, seed twoto eight weeks earlier than a wheat or rye graincrop to 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 canmake field management (especially killing thecover crop and tillage) more difficult in spring.See Rye Smothers Weeds Before Soybeans (p.67).

Rye is more sensitive to seeding depth thanother cereals, so plant no deeper than 2 inches(51). Drill 60 to 120 lb./A (1 to 2 bushels) into aprepared seedbed or broadcast 90 to 160 lb./A(1.5 to 3 bushels) and disk lightly or cultipack

(302, 351). If broadcasting late in fall and yourscale and budget allow,you can increase the seed-ing rate to as high as 300 or 350 lb./A (about 6bushels) to ensure an adequate stand.

“Rye is the only cover crop I’ve found that youcan successfully overseed by air, year in and yearout,”observes Mark Davis, an ag business manage-ment Extension specialist in Dover, Del.“Rye willgerminate and grow on concrete,”he jokes.

“I use a Buffalo Rolling Stalk Chopper to helpshake rye seeds down to the soil surface,” saysSteve Groff, a Holtwood, Pa., vegetable grower.“It’s a very consistent, fast and economical way toestablish rye in fall.” (Groff’s farming system isdescribed in detail on the World Wide Web athttp://www2.epix.net/~cmfarm).

Mixed seeding. Plant rye at the lowest locallyrecommended rate when seeding with a legume(302), 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 (61). 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. Thisprovides good weed control in asparagus, saysRich de Wilde,Viroqua,Wis. (86).

After drilling a large-seeded summer crop such as soybeans, try broadcasting rye. The covergrows well if it’s a cool spring, and the summercrop takes off as the temperature warms up.Secondary tillage or herbicides would be neces-sary to keep the rye in check and to limit thecover crop’s use of soil moisture.

CEREAL RYE (Secale cereale)

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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 the maturity 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 soilmoisture. But spring rains can be problematicwith rye, especially before an N-demanding crop, such as corn.Even if plentiful moisture has-tens the optimal kill period, youstill might get too much rain inthe following weeks and havesignificant nitrate leaching, aMaryland study showed (84).Soilcompaction also could be aproblem if you’re mowing ryewith heavy equipment.

Late killing of rye can deplete soil moisture andcould produce more residue than your tillage sys-tem can handle. For influencing corn yields inhumid climates, however, summer soil-water con-servation by cover crop residues often is moreimportant than spring moisture depletion by grow-ing cover crops,Maryland studies showed (62,64).

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 (84).

A legume/rye mix generally increases total drymatter, compared with a pure rye stand. Thehigher residue level can conserve soil moisture.For best results, wait about 10 days after killing

the covers before planting a crop. This ensuresadequate soil warming,dry enough conditions forplanter coulters to cut cleanly and minimizesallelopathic effects from rye residue (64, 84). Ifusing a herbicide, you might need a higher sprayvolume or added pressure for adequate coverage.

Kill before it matures. Tilling under rye usuallyeliminates regrowth, unless the rye is less than 12inches tall (302, 351). Rye often is plowed or disked in the Midwest when it’s about 20 inchestall (247). Incorporating the rye before it’s 18 in.

high could decrease tie-up ofsoil N (302,351).

For best results when mow-killing rye, wait until it hasbegun flowering. A long-dayplant, rye is encouraged toflower by 14 hours of daylightand a temperature of at least 40F. A sickle bar mower can givebetter results than a flail

mower, which causes matting that can hinderemergence of subsequent crops (89).

Mow-kill works well in the South after ryesheds pollen in late April (75). 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 bylate boot stage, before it heads or flowers.“If ryegets away from you,you’d be better off baling it orharvesting it for seed,” cautions southern Illinoisorganic grain farmer Jack Erisman (24). He oftenoverwinters cattle in rye fields that precede soy-beans. But he prefers that soil temperature be atleast 60 F before planting beans, which is too latefor him to no-till beans into standing rye.

“If rye is at least 24 inches tall, I control it witha 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 inchesdeep does a good job of tilling rye, says Rich deWilde,Viroqua,Wis. (86).

Rye is the best cool-season cover crop forscavenging N, typicallycarrying 25 to 50 lb.N/A over to spring.


Can’t delay a summer planting by a few weekswhile 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.

Glyphosate provides a slow, yet effective, kill.Paraquat kills more rapidly and would be betterwhen spring moisture is limited (82). For quickergrowth of a subsequent crop such as corn or soy-beans, leave the residue upright after killing(rather than flat). That hastens crop develop-ment—unless it’s a dry year—via warmer soiltemperatures and a warmer seed zone, accordingto a three-year Ontario study (80,111). This rarelyinfluences overall crop yield, however, unless youplant too early and rye residue or low soil tem-perature inhibits crop germination.

Pest ManagementThick stands ensure excellent weed sup-pression. To extend rye’s weed-managementbenefits, you can allow its allelopathic effects topersist longer by leaving killedresidue on the surface rather thanincorporating it. Allelopathiceffects usually taper off afterabout 30 days. After killing rye, it’sbest to wait three to four weeksbefore planting small-seededcrops such as carrots or onions. Ifstrip tilling vegetables into rye, be aware that ryeseedlings have more allelopathic compoundsthan more mature rye residue.Transplanted veg-etables, such as tomatoes, and larger-seededspecies,especially legumes,are less susceptible torye’s allelopathic effects (90).

In an Ohio study, use of a mechanical under-cutter 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 (70).

If weed suppression is an important objectivewhen 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 andbigflower vetch (a quick-establishing, self-seed-ing, winter-annual legume that flowers andmatures weeks ahead of hairy vetch) can sup-press weeds significantly more than rye alone,while also allowing higher N accumulations (85).

“Rye can provide the best and cleanest mulchyou could want if it’s cut or baled in spring beforeproducing viable seed,” says Rich de Wilde (86).Rye can become a volunteer weed if tilledbefore it’s 8 inches high, however, or if seedheadsstart maturing before you kill it. Minimizeregrowth by waiting until rye is at least 12 incheshigh before incorporating or by mow-killing afterflowering but before grain fill begins.

Insect pests rarely a problem. Rye can reduceinsect pest problems in crop rotations, southernresearch suggests (369). In a number of mid-

Atlantic locations, Colorado pota-to beetles have been virtuallyabsent in tomatoes no-till trans-planted into a mix of rye/vetch/crimson clover, perhaps becausethe beetles can’t navigatethrough the residue (132).

While insect infestations arerarely serious with rye, as with any cereal graincrop occasional problems occur. If armywormshave been a problem, for example, burning downrye before a corn crop could move the pests intothe corn. Purdue Extension entomologists notemany northeastern Indiana corn farmers reportedthis in 1997. Crop rotations and Integrated PestManagement can resolve most pest problems youmight encounter with rye.

Few diseases. Expect very few diseases whengrowing rye as a cover crop. A rye-based mulchcan reduce diseases in some cropping systems.No-till transplanting tomatoes into a mix of

Rye can effectivelysuppress weeds byshading, competitionand allelopathy.

RYE 71

rye/vetch/crimson clover, for example,consistent-ly has been shown to delay the onset of earlyblight in several locations in the Northeast (132).The mulch presumably reduces soil splashingonto the leaves of the tomato plants.

If you want the option of harvesting rye as agrain crop, use of resistant varieties, crop rotationand plowing under crop residues can minimizerust, stem smut and anthracnose.

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 planti-ngs, a California study showed (173).

Erol Maddox, a Hebron, Md. grower, takesadvantage 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 (199).

Mature rye isn’t very palatable and providespoor-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 falland early spring. It tolerates fall grazing or mow-ing with little effect on spring regrowth in manyareas (166). Growing a mixture of more palatablecover crops (clovers, vetch or ryegrass) canencourage regrowth even further by discouragingovergrazing (268).

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 soil drainageand warming even further,delaying crop planting.It’s also not a silver bullet for eliminating herbi-cides.Expect to deal with some late-season weedsin subsequent crops (339).

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(191, 302).

• Rye is a better soil renovator than oats (351),but brassicas and sudangrass provide deepersoil penetration (371).

• Brassicas generally contain more N than rye,scavenge N nearly as well and are less likely to tie up N because they decompose morerapidly.

SEED

Cultivars. MERCED is a popular variety. AROO-STOOK is very cold-tolerant. ALBION is nematicidal.ABRUZZI is the earliest Southern variety. ELBON isslightly later than ABRUZZI but both are earlierthan RYMOR.


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 is slower to mature than some cereals, so there isno rush to incorporate it early in spring and riskcompacting soil in wet conditions.

Whether grown as a cover crop or for grain,winter wheat opens a rotation niche for under-seeding a legume (such as red clover or sweet-clover) for forage or nitrogen.It works well as partof a no-till or reduced-tillage crop rotation,and forweed control in potatoes grown with irrigation insemiarid 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, wheat takes up N relatively slowly in autumn. It adds up,however. A September-seeded stand can absorb40 lb. N/A by December, a Maryland studyshowed (30). As an overwintering cover ratherthan a grain crop, wheat wouldn’t need fall orspring fertilizer.

A wheat stand can take up 0.5 to 0.7 lb.of P2O5

for each bushel of grain produced,but nearly two-thirds of it (20 to 25 pounds per acre for a 50-bushel wheat crop) is absorbed before boot stage.Wheat also can take up 1.5 to 2 lb. K2O for eachbushel produced. About 90 percent of that istaken up before wheat heads, and more than 80percent of the K is recycled if the stems andleaves aren’t removed from the field at harvest.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 providesa cash-grain option while also creating a niche ina corn>soybean or similar rotation for a secondcover crop, such as a winter annual legume. Forexample:

• In the Cotton Belt, wheat and crimson cloverwould be a good mix.

• In Hardiness Zone 6 and parts of Zone 7,plant hairy vetch after wheat harvest, giving thelegume plenty of time to establish in fall. Vetchgrowth in spring may provide most of the N nec-essary for heavy feeders such as corn,or all of theN for sorghum, in areas northward to southernIllinois, where early spring warm-up allows timefor development.

• In much of Zone 7,cowpeas would be a goodchoice after wheat harvest in early July or beforeplanting winter wheat in fall (88).


WINTER WHEATTriticum aestivum

Type: winter annual cereal grain

Roles: prevent erosion, suppressweeds, scavenge excess nutrients,add organic matter

Mix with: annual legumes orgrasses, ryegrass


• In the Corn Belt and northern U.S.,undersowred clover or frostseed sweetclover into a wheatnurse crop if you want the option of a year of haybefore going back to corn. Or, kill a wheat covergrown with a winter annual such as hairy vetchbefore vetch reaches peak N, and still make yourarea’s usual planting date for corn. Winterkilledcrimson or berseem clover are other options.

With or without underseeding a legume orlegume-grass mix, winter wheat provides greatgrazing and nutritional value and can extend thegrazing season. In Zone 8 and warmer, you alsohave a dependable double-crop option. See WheatBoosts Income and Soil Protection (p.74).

Weed suppressor. As a fall-sown cereal, wheatcompetes well with most weeds once it is estab-lished (51). 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.Although it generally produces less than rye orbarley, the residue can be easier to manage andincorporate. Wheat’s fine root system alsoimproves topsoil tilth.

When selecting a locally adapted variety for useas a cover crop, you might not need premiumseed. While a few cultivars, such as POCAHONTAS,provide slightly more biomass in early growthstages, first-year data from a Maryland study of 25wheat cultivars showed no major differences inoverall biomass production at maturity (66). Ifweed control is important in your system,look fora regional cultivar that can produce early springgrowth.To scavenge N, select a variety with goodfall 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 fairlyslow 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-fertility or light-textured soils, consider a mixed seedingwith a legume (60). Another alternative could beadding up to 50 pounds of starter N per acre,espe-cially on low-N soils if you’ll be killing the wheat inspring before a heavy-feeding crop such as pota-toes and are relying on a thick,overwintering standfor weed control. See Wheat Offers High ValueWeed Control, Too (p. 75). Too much N, however,can produce rank, succulent plants that aresusceptible to winterkill, disease or lodging.

A firm seedbed helps reduce winterkill ofwheat. Minimize tillage in semiarid regions toavoid pulverizing topsoil (297) and depleting soilmoisture (82).

WINTER WHEAT 73

WINTER WHEAT (Triticum aestivum)

Elay

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Sear

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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 early winter in Zone 8 and warmer. If yourcover crop planting is delayed, consider sowingrye instead.

Drill 60 to 120 lb./A (1 to 2 bushels) into a firmseedbed 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 (51).

After cotton harvest in Zone 8 and warmer,no-till drill 2 bushels of wheat per acre withoutany seedbed preparation. With irrigation or inhumid regions, you could harvest 45- to 60-bushel wheat, then double crop with soybeans,cotton or another summer crop. See WheatBoosts Income and Soil Protection (above).Youalso could overseed winter wheat prior to cot-ton defoliation and harvesting (287).

Another possibility for Zone 7 and cooler:Plantfull-season soybeans into wheat cover cropresidue, and plant a wheat cover crop after beanharvest (60).

Mixed seeding or nurse crop. At low to medi-um rates (300), winter wheat is an excellent nursecrop for frostseeding red clover (at 8 to 12 lb./A),or sweetclover (at 4 to 12 lb./A). In the Corn Belt,the legume usually would be sown in winter orbefore wheat’s vegetative growth resumes inspring. If you sow sweetclover in fall with winterwheat, it could outgrow the wheat. If you want agrain option, that could make harvest difficult.

Spring annual use. Spotty overwintering of win-ter wheat in your area? Or no time to fall-seed it?Although it’s not a common practice, you canspring-seed winter wheat as a weed-suppressingcompanion crop or early forage. It won’t have achance to vernalize (be exposed to extended coldafter germination), so it usually dies on its ownwithin a few months,without setting seed.By sow-ing when field conditions permit in early spring,

Wheat Boosts Income and Soil ProtectionWheat is an ideal fall cover crop that candouble as a cash crop, cotton farmer MaxCarter has found.“It’s easier to manage thanrye, still leaves plenty of residue to keeptopsoil from washing away—and is anexcellent double crop,” says Carter.

The southeastern Georgia farmer no-till drillswinter wheat at 2 bushels per acre right aftercotton harvest,without any seedbedpreparation.“It gives a good, thick stand,”he says.

“We usually get wheat in by Thanksgiving,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.

He pays about 7 to 14 cents per pound forseed, depending on whether he chooses to

use uncleaned or premium, cleaned seed.Disease or pests rarely have been a problem,he notes.

“It’s a very easy system, with wheat alwaysserving 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-acrecotton, 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.”

WINTER WHEAT 75

within a couple months you could have a 6- to 10-inch tall cover crop into which you can no-tillplant soybeans.You might not need a burndownherbicide, either.

Early planting of spring wheat, with orwithout a legume companion, is an option,especially if you have a longer rotation nicheavailable.

Pairing a winter wheat cover crop with areduced herbicide program could provideexcellent weed control in potatoes grown on light soils in irrigated, semiarid regions,research in the inland Pacific Northwestsuggests.A SARE-funded study in the early1990s showed that winter wheat providedeffective competition against annual weeds that infest irrigated potato fields inWashington, Oregon and Idaho. However,potato yield and quality reductionsoutweighed cost savings, that study’seconomic analysis showed.

Banding herbicide over the row whenplanting potatoes improves the system’seffectiveness, subsequent research shows, saysproject coordinator Dr.Charlotte Eberlein at theUniversity of Idaho’s Aberdeen Research andExtension Center. “In our initial study,we wereeffectively no-tilling potatoes into the Roundup-killed wheat,”says Eberlein.“Now we kill thecover crop and plant potatoes with a regularpotato planter,which rips the wheat out of thepotato row.”A grower then can band a herbicidemixture over the row and depend on the wheatmulch to 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 covercrop for suppressing weeds in a system likethis,” she notes.“Volunteer rye, however, is aserious problem in wheat grown in the West,and wheat is a common rotation crop forpotato growers in the Pacific Northwest.”

She recommends drilling winter wheat at90 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 showsgood 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 wheatand 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 wait for 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 in the hills for potatoes to sprout.”

An irrigation option ensures adequate soilmoisture—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 gives competitive yields, she observes, basedon research station trials.

Full-scale on-farm studies and economicanalyses are next on the project agenda andcould lead to greater use of winter wheat as a cover crop for weed control, nutrient cyclingand other benefits.

Wheat Offers High-Value Weed Control, Too


Field ManagementYou needn’t spring fertilize a winter wheat standbeing grown as a cover crop rather than a graincrop. As with any overwintering small grain crop,however,you will want to ensure the wheat standdoesn’t adversely affect soil moisture or nutrientavailability for the following crop.

KillingKill wheat with a grass herbicide in spring, or byplowing, disking or mowing before seedheadsmature.

There is no need to rush to killwheat in spring as is sometimesrequired for rye. That’s one reasonvegetable grower Will Stevens,Shoreham, Vt., prefers wheat torye as a winter cover on his heavy,clay-loam soils.The wheat goes toseed slower and can provide moreleaf matter than an earlier killingof rye would, he’s found.With rye, he has to disktwo to three weeks earlier in spring to incorpo-rate the biomass, which can be a problem in wetconditions.“I only chisel plow wheat if it’s reallyrank,”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 dis-ease. Managed as a cover crop, wheat rarelyposes an insect or disease risk. Diseases can be

more of a problem the earlier wheat is planted infall, especially if you farm in a humid area.

Growing winter wheat could influence thebuildup of pathogens and affect future small-grain cash crops, however. Use of resistant vari-eties and other Integrated Pest Managementpractices can avoid many pest problems inwheat grown for grain. If wheat diseases or pestsare a major concern in your area, rye or barleymight be a better choice as an overwinteringcover crop that provides a grain option, despitetheir lower yield.

Other OptionsChoosing wheat as a small-graincover crop offers the flexibilityin late spring or early summer toharvest a grain crop. Spring man-agement is essential for the graincrop option.A good resource forgrain production techniques,

used extensively in writing this chapter, is BestManagement Practices for Wheat, listed underRecommended Resources (p. 163).

Management CautionsAvoid grazing livestock in wheat stands sufferingfrom fungal diseases such as scab, which canproduce substances toxic to livestock, especiallynonruminants.


Wheat is less likelythan barley or rye tobecome a weed, andis easier to kill.

BUCKWHEAT 77

Buckwheat is the speedy short-season covercrop. It establishes, blooms and reachesmaturity in just 70 to 90 days. Then 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 cover crops.

Buckwheat thrives in cool, moist conditionsbut 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,soil-shading canopy, though not as dense as corn orsoybeans.Buckwheat typically produces only 2 to3 tons of dry matter per acre,but it does so quick-ly—in just six to eight weeks in the mild, temper-ate fields of central Pennsylvania in USDA

Hardiness Zone 5-6 (206).Buckwheat residue alsodecomposes quickly, releasing nutrients to thenext crop.

Weed suppressor. Buckwheat’s strong weed-suppressing ability makes it ideal for smotheringwarm-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 (206).While living buckwheat may have anallelopathic weed-suppressing effect (291), its pri-mary impact on weeds is through shading andcompetition.

Phosphorus scavenger. Buckwheat is believedto be effective in taking up phosphorus and someminor nutrients (possibly including calcium) thatare otherwise unavailable to crops, then releasingthese nutrients to later crops as the residuebreaks down. The roots of the plants producemild acids that free these nutrients from othercompounds. This effect aids in activating slow-releasing organic fertilizers, such as rock phos-phate. Buckwheat’s dense, fibrous roots cluster in

BUCKWHEAT

summer orcool-season annual

too dry, cool

Fagopyrum esculentum

Type: summer or cool-seasonannual broadleaf grain

Roles: quick soil cover, weedsuppressor, nectar for pollinatorsand beneficial insects, topsoilloosener, rejuvenator for low-fertility soils

Mix with: sorghum-Sudangrasshybrids, sunn hemp



the top 10 inches of soil, providing an extensiveroot surface area for nutrient uptake.

Thrives in poor soils. Buckwheat performs bet-ter 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 the mid-point of its long flowering period to reseed a sec-ond 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.

Late-season nurse crop. Due to its quick,aggressive start, buckwheat sees only limitedaction as a nurse crop. It’s sometimes used to pro-tect late-fall plantings of slow-starting, winter-hardy legumes wherever freezing temperaturesare sure to kill the 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-inch rows. Use heavier rates for a quickercanopy. For a fast smother crop, broadcast up to96 lb./A (2 bu./A) onto a firm seedbed and incor-porate with a harrow, tine weeder, disk or fieldcultivator. Overall vigor is usually better indrilled seedings. As a nurse-crop for slow-grow-ing, winter annual legumes planted in late sum-mer or fall, seed at one-quarter to one-third ofthe normal rate.

Buckwheat compensates for lower seedingrates by developing more branches per plantand more seeds per blossom. However, skimpingtoo much on seed makes stands more vulnerableto early weed competition until the canopy fillsin. Using cleaned, bin-run or even birdseed-gradeseed can lower establishment costs, but increas-es the risk of weeds. As denser stands mature,stalks become spindly and are more likely tolodge from wind or heavy rain.

BUCKWHEAT (Fagopyrum esculentum)

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BUCKWHEAT 79

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 vegetablecrops, then followed by a fall vegetable, wintergrain,or cool-season cover crop.In many areas, it can be plantedfollowing harvest of winterwheat or canola.

In parts of California, buck-wheat grows and flowersbetween the killing of winterannual legume cover crops inspring and their re-establish-ment in fall. Some Californiavineyard managers seed 3-foot strips of buck-wheat in row middles, alternating it and anothersummer cover crop, 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 (57). 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 beneficialinsects, allow buckwheat to flower for at least 20days—the time needed for minute pirate bugs toproduce another generation.

Buckwheat can be double cropped for grainafter 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 and

specially raised food-gradebuckwheat in domestic andoverseas markets.About 70,000acres are grown in the U.S.,with prices typically around 10 cents/lb. Exporters usuallyspecify variety, so investigatebefore planting buckwheat forgrain.

Management CautionsTo get optimal biomass while preventing buck-wheat from becoming a weed in following crops,kill within 7 to 10 days after flowering begins,before the first seeds begin to harden and turnbrown. Earliest maturing seed can shatter beforeplants finish blooming. Some seed may overwin-ter in milder regions.

Buckwheat can harbor insect pests includingLygus bugs, tarnished plant bugs and Pratylynchuspenetrans root lesion nematodes (204).

COMPARATIVE NOTES

• Buckwheat has only about half the root massas a percent of total biomass as small grains(294). Its succulent stems break downquickly, leaving soils loose and vulnerable to erosion, particularly after tillage. Plant asoil-holding crop as soon as possible.

• Buckwheat is nearly three times as effectiveas barley in extracting phosphorus, and more than 10 times more effective thanrye—the poorest P scavenger of the cerealgrains (294).

• As a cash crop, buckwheat uses only half asmuch soil moisture as soybeans (242).


Buckwheat germinates and grows quickly,producing 2 to 3 tons of dry matter in just 6 to 8 weeks.


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-typesorghums and sundangrass. Compared with corn,they have less leaf area,more secondary roots anda waxier leaf surface, traits that help them with-stand drought (302). Like corn, they require goodfertility—and usually added nitrogen—for bestgrowth.Compared with sudangrass, these hybridsare taller, coarser and more productive.

Forage-type sorghum plants are larger, leafierand mature later than grain sorghum plants.Compared with sorghum-sudangrass hybrids,theyare shorter, less drought tolerant, and don’tregrow as well (292). Still, forage sorghums as well as most forms of sudangrass can be used inthe same cover-cropping roles as sorghum-sudan-grass hybrids. All sorghum- and sudangrass-relatedspecies produce compounds that inhibit certain

plants and nematodes. They are not frost tolerant, and should be planted after the soilwarms in spring or in summer at least six weeksbefore first frost.

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, well-wateredsoil.

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 New York muck soils caused roots to burrow 10to 16 inches deep compared to 6 to 8 inches deepfor unmowed plants (224). The roots of mowed

SORGHUM-SUDANGRASS HYBRIDSSorghum bicolor X S. bicolorvar. sudanese

Also called: Sudex, Sudax (DeKalb reg. brand)

Type: summer annual grass

Roles: soil builder, weed andnematode suppressor, subsoilloosener

Mix with: buckwheat, sesbania,sunnhemp, forage soybeans orcowpeas

See charts, pp. 47 to 53, for rank-ing and management summary.

summer annual summer annual irrigated

year-round crop limited by cool temps.

SORGHUM-SUNDANGRASS HYBRIDS 81

plants fractured subsoil compaction with worm-hole-like openings that improved surfacedrainage. However, four mowings at shorterheights caused plants to behave more like a grassand significantly decreased the mass, depth anddiameter of roots (223).

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 (305). 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 (362).

Sorghum-sudangrass hybrids suppress suchannual weeds as velvetleaf, large crabgrass, barn-yardgrass (97,245),green foxtail,smooth pigweed(146), common ragweed, redroot pigweed andpurslane (257).They also suppressed pine (171)and redbud tree seedlings in nursery tests (117).The residual weed-killing effects of these allelo-chemicals increases when sorghum-sudangrasshybrids are treated with the herbicides sethoxy-dim, glyphosate or paraquat, in descending orderof magnitude (109).

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 (11).

Renews farmed-out soils. The combination ofabundant biomass production, subsoiling root

systems, and weed and nematode suppressioncan produce dramatic results.

On a low-producing muck field in New Yorkwhere 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 (174).

Widely adapted. Sorghum-sudangrass hybridscan be grown throughout the U.S. wherever rain-fall is adequate and soil temperature reaches 65 Fto 70 F at least two months before frost. Onceestablished, they can withstand drought by goingnearly dormant. Sorghum-sudangrass hybridstolerate pH as high as 9.0, and are often used inrotation with barley to reclaim alkaline soil (350).They tolerate pH as low as 5.0 (306).

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 is riskiest when plants are young (up to24 inches tall), drought stressed or killed by frost.Toxicity danger varies between cultivars.

SORGHUM-SUDANGRASS (Sorghum bicolor XS. bicolor var. sudanese

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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 (302). Standard biomass production usuallyrequires 75 to 100 lb. N/A .

With sufficient surface moisture, broadcast 40to 50 lb./A, or drill 35 to 40 lb./A as deep as 2inches to reach moist soil.These rates provide aquicker canopy to smother weeds than lowerrates used for forage produc-tion, but they require mowingor grazing to prevent lodging.Herbicide treatment or a passwith a mechanical weeder maybe necessary if germination isspotty or perennial weeds area problem. New York on-farm tests show that astale seedbed method—tilling,then retilling to killthe first flush of weeds just before planting—provides effective weed control (224).

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 with thesorghum-sudangrass, then incorporate about 1inch deep.Fast-germinating buckwheat helps sup-press early weeds. Sorghum-sudangrass supportsthe sprawling sesbania, forage soybeans and cow-peas. Sunnhemp has an upright habit, but couldcompete well for light if matched with asorghum-sudangrass cultivar of a similar height.

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 (223).

Mowing or grazing when stalks are 3 to 4 feettall 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 planting—within seven weeks of frost—makes mowingunnecessary and still allows for good growthbefore winterkilling (223, 224, 302).

Disking while plants are still vegetative willspeed decomposition. Make several passes with aheavy disk or combination tillage tool to handlethe dense root masses (223).Sicklebar mowing orflail chopping before tillage will reduce the num-ber of field operations required to incorporate thecrop and speed decomposition. Sicklebars cut

more cleanly but leave thestalks whole. Using a front-mounted flail chopper avoidsthe problem of skips wheretractor tires flatten the plants,putting them out of reach of arear-mounted chopper.

Any operations that decrease the residue sizeshortens the period during which the decompos-ing residue will tie up soil nitrogen and hinderearly planted crops. Even when mowed, residuewill become tough and slower to break down ifleft on the surface.

Flail chopping after frost or killing the covercrop 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. Allow the nutsedge to grow until it’s about 4 to 5 inchestall, about mid-June in New York. Kill the nutsedgewith herbicide, then plant the weed-smotheringhybrid.

Beneficial habitat. Some related sorghum culti-vars harbor beneficial insects such as seven-spot-ted lady beetles (Coccinella septempunctata) andlacewings (Chrysopa carnea) (350).

Nematodes. Sorghum-sudangrass hybrids andother sorghum-related crops and cultivars sup-

These heat-loving plantsare unrivaled for addingorganic matter to soils.


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, manystudies show.

Timing of cutting and tillage is very important tothe effectiveness of nematode suppression. Thecover crop needs to be tilled before frost while it isstill green. Otherwise, thenematicidal effect is lost. Formaximum suppression of soil-borne diseases, cut or choppedSudangrass must be well incor-porated immediately (248).

In an Oregon potato trial,TRUDAN 8 sudangrass controlledColumbia root-knot nematodes (MeloidogoyneChitwoodi), a serious pest of many vegetablecrops. Control extended throughout the zone ofresidue incorporation. The cover crop’s effectprevented upward migration of the nematodesinto the zone for six weeks,working as well as thenematicide ethoprop. Both treatments allowedinfection later in the season (227).

In the study, TRUDAN 8 sudangrass and thesorghum-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-sudangrasscultivars are useful if the cover crop is intendedfor anti-nematicidal effects only (227). In otherOregon and Washington trials, the cover crop sup-pression required supplemental chemical nemati-cide to produce profitable levels of U.S. No. 1potatoes (227). These same sudangrass andsorghum-sudangrass hybrid cultivars failed toshow any significant nematicidal effects in a laterexperiment in Wisconsin potato fields (198).

When faced with infestations of the nematodesMeloidogoyne incognita and M. arenaria,Oswego,N.Y.,onion grower Dan Dunsmoor foundthat a well-incorporated sorghum-sudangrass

cover crop with a seed cost of $32.50/A wasmore effective than fumigation costing $300 to$600/A. Further, the nematicidal effect continuedinto the next season, while the conditions a yearafter fumigation seemed worse than before theapplication. He reports that the sorghum-sudan-grass cover crop also controls onion maggot,thrips and Botrytis leaf blight (174).

Insect pests. Chinch bug (Blissus leucopterus),sorghum midge (Contarinia sorghicola), corn leaf

aphid (Rhopalosiphum maidis),corn earworm (Heliothis zea),greenbugs (Schizaphis gram-inum) and sorghum webworm(Celama sorghiella) sometimesattack sorghum-sudangrass hybrids.Early planting helps control thefirst two pests, and may reduce

damage from webworms. Some cultivars andhybrids are resistant to chinch bugs and somebiotypes of greenbugs (302). In Georgia, somehybrids hosted corn leaf aphid,greenbug,southerngreen stinkbugs (Nezara viridula) and leaffoottedbug (Leptoglossus phyllopus).

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 landfallow for a few months when soil is notfrozen to allow decomposition of the residue.If you kill the cover crop early enough in fall,

the residue will partially break down before coldtemperatures slow biological action (302). Wherepossible, use sorghum-sudangrass ahead of later-planted crops to allow more time in spring forresidue to decompose.

Planting sorghum-sudangrass every third yearon New York potato and onion farms will rejuve-nate soil, suppress weeds and may suppress soilpathogens and nematodes. Working a legume into

These plants producechemicals that inhibitcertain weeds andnematodes.


the 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 onceand then suppressed or killed, sorghum-sudan-grass can reduce weeds in fall-planted alfalfa.Sorghum-sudangrass suppressed alfalfa rootgrowth significantly in a Virginia greenhousestudy (109), but no effect was observed on alfalfa

germination when alfalfa was no-till planted intokilled or living sorghum-sudangrass (110).

In California, some table grape growers usesorghum-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.

Summer Covers Relieve CompactionA summer planting of sudangrass was thebest single-season cover crop for relievingsoil compaction in vegetable fields, a team of Cornell researchers found.Yellowmustard, HUBAM annual white sweetcloverand perennial ryegrass also were effective to some extent in the multi-year study.“Butsudangrass has proven the most promisingso far,” says project coordinator David Wolfe.“It has shown the fastest root growth.”

Sudangrass is particularly effective whenit is mowed once during the season,Wolfeadds. Mowing strengthens its deep,penetrating root system while the above-ground biomass adds to soil organic matter.

Farmers and researchers have longknown that alfalfa’s deep root system is agreat compaction-buster. But most vegetablegrowers can’t afford to remove land fromproduction for two to three years to grow it, notes Wolfe. Many also lack theequipment to subsoil their fields, which is often only a temporary solution, at best.That’s why Wolfe geared his study toidentify covers that can produce results in a single season. In the case of heat-loving sudangrass, it also may be possible to squeeze a spring or fall cash crop into the rotation while still growing the coverduring summer.

Heavy equipment, frequent tillage and lackof 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. For example, the Cornellresearchers found that slow-growing cabbagesdirect-seeded into compacted soils werevulnerable to flea beetle infestations.

Yellow mustard’s deep tap root may make it a solid challenger to sudangrass as a compaction reliever. But it was sometimesdifficult to establish in the test.“We still have a lot to learn about how best to grow thesecrops and how best to fit them into rotationswith vegetables,”Wolfe says.

Wolfe and his team assessed the cover crops’effectiveness by measuring yields of subsequentcrops and conducting a host of soil qualitymeasurements, including infiltration rates,water-holding capacity, aggregate stability and organic matter levels.They will follow up this research by examining the effects ofcompaction on pathogenic and beneficialmicroorganisms in the soil.

For more information, contact David Wolfe,(607) 255-5439, [email protected].


Incorporated sorghum-sudangrass residuereduces N availability to young crops more thanoat residue but less than wheat residue (319).

For suppressing root-knot nematodes in Idahopotato fields, rapeseed has proven slightly moreeffective and more dependable than sorghum-sudangrass hybrids (322).

SEED

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, selectsorghum-sudangrass hybrids and related cropswith lower levels of dhurrin, the compoundresponsible for prussic acid poisoning. Formaximum weed control, choose types high insorgoleone, the root exudate that suppressesweeds. Sterile cultivars are best where escapescould be a problem, especially where crossingwith johnsongrass (Sorghum halpense) ispossible.

To extend weed suppressive effects into thesecond season, select a cultivar known for weedsuppression and leave roots undisturbed whenthe stalks are mowed or grazed (361).


OVERVIEW OF LEGUME COVER CROPSCommonly used legume cover crops include:• Winter annuals, such as crimson clover, hairy

vetch, 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 often are used to:• Fix atmospheric nitrogen (N) for use by subse-

quent crops• Reduce or prevent erosion• Produce biomass and add organic matter to

the 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. Therefore, if youneed a cover crop to take up excess nutrientsafter manure or fertilizer applications, a grass or amixture is usually a better choice.

Winter-annual legumes, while established inthe fall,usually produce most of their biomass and

N 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.

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 betweencash 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 they are functioning more as a rotation crop thana cover 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 summer


annuals, 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 andhigher in nitrogen than grasses. This lower C:Nratio results in faster breakdown of legumeresidues. Therefore, the N and other nutrients

contained 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.

Mixtures of two or more cover crops areoften more effective than planting asingle 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

Possible disadvantages of cover crop mixturesmay include:• 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.

GRASS/LEGUME MIXTURES EXPAND POSSIBILITIESUsing 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 variedmaturity dates and growth habits maintains opti-mum benefits for a longer time. Orchardists inCalifornia mix subclovers to keep weeds at bay all season. One cultivar comes on early, then diesback as two later cultivars—one tall and oneshort—come on strong. Because they reseedthemselves,the cooperative trio persists year afteryear.

Sometimes you don’t know how much N maybe left after cash crop harvest. Do you need agrass to scavenge leftover N, or a legume to pro-vide fixed N? A grass/legume cover crop mixtureadjusts to the amount of available soil N: If thereis a lot of N, the grass dominates; if there is notmuch available soil N, the legume will tend todominate a mixture. In either case, you get thecombined benefit of N scavenging by the grasscover crop and N additions from the legumecover 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-

BERSEEM CLOVER 87

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 legumeimproves 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 for

each 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 be lim-ited when you plant a mixture of legumes andnonlegumes.

• Sometimes you can end up with more residuethan your equipment can handle.The benefits of a mixture will usually outweigh

these 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 work well.Try some of the proven cover crop mixtures, andcreate your own tailor-made mixtures. Rememberthat adding another crop increases the diversity onyour farm,and is likely to increase the many provenbenefits of rotations over monocropping.

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. 47 to 53, for rankingand management summary.

summer annual winter 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 in

Corn 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 favorablywith alfalfa in its regrowth following small grainharvest, its feed value and its tolerance to droughtand excess moisture (119). As a winter annual inCalifornia, irrigation usually is needed to allowberseem to achieve its full potential. Its peakgrowth 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. Alfalfa has its peak growth duringdry summer periods (127).

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 withsix cuttings per year (127), and grew faster thanBIGBEE in one Iowa report (118). Berseem is lessprone to possible N leaching if grown to maturi-ty without cutting, when it produces 100 to 125lb. N/A. Top N fixation occurs when soils haveless than 150 lb. N/A (127). A single cutting canyield 50 to 100 lb. topgrowth N/A. Berseem’sdry matter N concentration is about 2.5 percent(127).

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 TIBBEE

crimson clover WOOGENELLUP subterraneumclover and WOODFORD bigflowervetch. All but arrowleaf cloverwere able to set seed by May 13and regrow in the fall,despite theherbicides used to suppressthem in spring and to controlweeds during summer (23).

In recent Alberta legume trials,berseem clover averaged 3,750 lb. dry matter/Aover three years at a site where hairy vetch andfield peas produced 5,300 lb. and 4,160 lb.,

respectively. With irrigation, berseem clovertopped 19 other legumes at the same site with amean yield of 5,500 lb. DM/A.

Smother crop. Planted with oats or annualryegrass, berseem clover suppresses weeds wellduring establishment and regrowth after oatharvest.

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 (120).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 be ready to cut about 60 days after planting.

Legume nurse crop. Because of its quickgermination (seven days), quick growth andwinterkilling tendency, berseem clover can beused as a 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 (77).

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 clover

have been reported (121, 225).Forage quality remains accept-able until the onset of seed pro-duction. BIGBEE berseem cloverand TIBBEE crimson producemore fall and winter growth thando other winter annual clovers inthe South. BIGBEE continues pro-

ducing longer into the spring than otherlegumes, extending cuttings into late May orearly June in Mississippi (179).

MULTICUT berseemclover averaged 280lb. N/A in a six-yearCalifornia trial.

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MANAGEMENT

EstablishmentBerseem prefers slightly alkaline loam and siltysoils but grows in all soil types except sands. Soilphosphorus can limit berseem clover growth.Fertilize with 60 to 100 lb. P2O5/A if soil testsbelow 20 ppm (127). Boron also may limitgrowth, so test soil to maintain levels (225).Berseem tolerates saline conditions better thanalfalfa and red clover (91). Use R-type inoculantsuitable for berseem clover and crimson clovers.

Broadcast or drill berseem seed alone or withspring 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,cultipack or roll soil before and after broadcastseeding (127). Dry, loose soil will suppressgermination.

Recommended seeding rates are 8 to 12 lb./Adrilled 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 (364).

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 (308), but frostrisk is significant (124).

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 (122).

When seeding a mixture, harvest goals affectvariety 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 early

DEXTER, MI.—Mixing berseem clover 50:50with crimson clover for an interseeded legumecover in corn works well for Dexter, Mich.,farmer Paul Guenther. “They seem to thrive onopposite conditions, and both survive most ofthe time,”he says. He plants 8 to 10 lb. mixedseed/A in a 12- to 15-inch band between therows at final cultivation.

Guenther applies the seed throughinsecticide boxes from a corn planter.They’remounted on a toolbar that’s part of an oldanhydrous rig he uses to apply 28 percent N.Typically, the feed cups that handle granularinsecticide run too fast for small seeds andgrind them up. He overcame that problem bygearing down the rotation with a jack shaftthat allows the rig to travel 65 feet for everyrevolution of the metering device. Thatallows him to open the feed gates of the

boxes for a good seed flow with very littleseed damage.

“The berseem clover keeps growing as thecorn grows, and can get up to knee high,” saysGuenther. “The crimson doesn’t get muchtaller after the corn canopy closes, but theleaves seem to get bigger.”The berseem cloverwinterkills, and the crimson comes back inspring. He plans to seed the mixture in themiddles between his ridge-tilled corn rows,then kill the crimson with wide sweeps at firstcultivation the following spring.

He’s likes how the mix performs muchbetter than the interseeded annual medic hetried for several years.“They just don’t toleratethe shade”under corn or bean rows, but helauds how the annual medics work in the full-season sunshine of the family’s market gardenbetween tomatoes or beet rows (134).

Crimson-Berseem Clover Combo Works as Corn Underseeding


forage before green manuring is the goal, seed amixture of 4 bu.oats and 15 lb.berseem/A. If bio-mass quantity is foremost, use a short-stalked,long-season oat. If oat grain production isprimary, keep oat seeding rate the same, but select a short-season, tall variety to reduce thelikelihood of berseem clover interfering withgrain harvest (119).

Berseem clover also can be a late-summer crop.Planted in mid-August in the Corn Belt, it shouldgrow 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 standingsmall-grain crops, a method that has worked wellin a series of on-farm tests in Iowa (118).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(302) and Iowa (124).

Southeast. Fall planting in mild regions provideseffective weed control as well as N and organicmatter for a spring crop. Seed Aug. 25 to Oct. 15 in Mississippi 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 (179).

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 (127).

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 assoon as basal bud regrowth reaches 2 inches(127). At the latest, clip before early floweringstage or plants will not regrow. Berseem clover responds best when field traffic isminimized (119).

Mowed berseem clover left in the field as greenmanure 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 (124).

Remember that berseem clover has a tap rootand shallow 6- to 8-inch feeder root system (119).In thin plantings or well-drained soils, it can besusceptible to drought, a trait that could triggermowing, grazing or killing earlier than originallyplanned (143).

Abundant soil N will restrict N fixation byberseem 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 (368).

Berseem made its N contribution to soil in thefinal third of its cutting cycle—regardless of initialsoil N availability—in all six years of the study.Nitrogen fixation was closely correlated to a drop

BERSEEM CLOVER (Trifolium alexandrinum)

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BERSEEM CLOVER 91

in water-use efficiency in the trial. After producingfrom 400 to 640 lb. of dry matter per acre-inch ofwater in the first four cuttings,production droppedto 300 lb.DM/A-in. for the final two cuttings (368).

Small grain companion. Underseeded berseemclover provided about 1.2 T forage dry matter/Aafter oat harvest in Iowa, worth about $75/A ascommercial livestock feed. Removing the foragedecreases the soil-saving ground cover and N con-tribution (122), trading soil andN benefits for attractive near-term income.

In the Midwest, greenchopan oat/berseem clover mixturewhen oat is at the pre-bootstage to avoid berseem clovergoing to seed early and, there-fore, not producing maximumnitrogen. Oats have high forageN values at this stage. Monitorcarefully during warm periods to avoid nitrogen tox-icity (299).

A Montana study found that spring plantings ofberseem clover will produce the most legume drymatter and N if clear seeded.If,however,you wish tomaximize total dry matter and protein, seeding withoats is recommended. The oat nurse crop suppressedweeds well and increased total dry matter productionby 50 to 100 percent regardless of whether plotswere cut two,three or four times (356).

KillingBerseem dies when exposed to temperatures be-low 20 F for several days,making winterkill a virtu-al certainty in Zone 7 and colder. This eliminatesthe need for herbicides or mechanical killing aftera cold winter, and hastens delivery of nutrients tothe soil.

To kill berseem clover ahead of fall-plantedcrops,wait for it to die after blooming,use multiplediskings or apply herbicides.In mild areas,berseemclover grows vigorously through late spring.BIGBEE

berseem clover remained vegetative until early Mayor later in an experiment at a northern Mississippi(Zone 7) site. Until it reaches full bloom, it willrequire either tillage or a combination of herbi-cides and mechanical controls to kill it.

In a northern Mississippi mechanical controlstudy, 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 (79).

Rolling with 4-inch rollers killed less berseemclover than hairy vetch or crimson when the

legumes had more than 10inches of stem laying on theground. Kill rate was morethan 80 percent for the lattertwo crops, but only 53 per-cent for berseem clover.Without an application ofatrazine two weeks prior toeither flail mowing or rollingwith coulters, the mechanicalcontrols failed to kill more

than 64 percent of the berseem clover until earlyMay, when flailing achieved 93-percent control.Atrazine alone reduced the stand by 68 percent inearly April,72 percent in mid-April and 88 percentin early May (79).

Pest ManagementAvoid direct seeding small-seeded vegetables intofields where you have incorporated berseemclover within the past month. Berseem clover,crimson clover and hairy vetch residue incorporat-ed directly into the seed zone may suppress germi-nation and seedling development of onion, carrotand tomato, based on interaction of extracts fromthese legumes and the seeds in lab tests (26).

Lygus bugs have been a serious problem inCalifornia 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 resistantcultivar. BIGBEE is susceptible to crown rot andother root diseases common to forage legumespecies (127).

Berseem, like other clovers, shows little resis-tance to root-knot nematode (Meloidogynespp.). It seems to be particularly favored byrabbits (302).

The least winter hardy ofthe true annual clovers,berseem can be plantedwith oats in the Corn Beltand produce abundant Nbefore winterkilling.


Crop SystemsFlexible oats booster. In the Corn Belt,berseemclover seeded with can helps diversify corn>soy-bean rotations,breaking pest cycles and providingsome 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 (122). Plant 4 bu. oatswith 12 lb. berseem/A.

In a four-year Iowa study, planting berseemclover with oats increased net profit by $39/Acompared with oats alone.The clover was baled

With the help of nitrogen-fixing bacteria,legume cover crops can supply some or all of 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 togrow. 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 the airfor 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 acceptablebacterial 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 spacesbetween 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 the

soil. 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 ofactive 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 idealbacterial match, they work with the best strainsthey can find. They just don’t work asefficiently together and they produce less N.Inoculating seeds with the correct strain beforeplanting is inexpensive insurance to make surelegumes perform up to their genetic potential.Clover inoculum, for example, costs just 6 centsper pound of seed treated,plus about 12 centsper pound for an enhanced sticker that buffersand feeds the seedling (194).

While they are alive, legumes release little or no nitrogen to the soil. The N in their roots,stalks, leaves and seeds becomes availablewhen the plants die naturally or are killed by tillage, mowing or herbicide. This plantmaterial becomes food for microbes, worms,insects and other decomposers.

Nodulation: Match Inoculant to Maximize N

BERSEEM CLOVER 93

for forage and the underseeded oats were har-vested for grain. Not calculated in the benefitwere the 40 to 60 lb. N/A provided to the follow-ing corn or other soil-improvement benefits.Theoats/berseem mix produced 70 percent more bio-mass, increased subsequent corn yields by 10 per-

cent and reduced weed competition comparedwith a year of oats alone (122).

Pure berseem clover regrowth averaged 1.2 Tdry matter/A,which can be used as forage or greenmanure. These options could help oats become aneconomically viable crop for Midwest crop/live-

Microorganisms mineralize, or convert, thecomplex “organic” forms of nitrogen in theplant material into inorganic ammonium and nitrate forms, once again making the N available to plants. How quickly themineralization of N occurs is determined by a host of environmental and chemical factors.These will affect how much of that legume N is available to the next crop or has thepotential to leach from the soil.

For more information about mineralizationand how much you can reduce your Nfertilizer rate for crops following legumes,see How Much N? (p. 22).

To get the most from your legume/bacteriacombination:• Choose appropriate legume species for

your 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. 51) to determine the best inoculant touse.

• Coat seed with the inoculant just beforeplanting. Use milk, weak sugar water or acommercial sticking agent to help thematerial stick to the seeds. Use only freshinoculant (check the package’s expirationdate), and do not expose packages orinoculated seed to excessive heat or directsunlight.Mix the sticker with non-chlorinated water

and 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 within48 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.

On-farm use of commercial sticker/inoculantproducts has produced more consistent resultsthan pelleting methods applied by seedcompanies (357). Gum arabic stickers withsugars and liming agents boost the chances for optimum nodulation over water-appliedinoculant alone. Pre-inoculated (“rhizo-coated”)seed weighs about one-third more than rawseed, so increase seeding rates accordingly.Commercial sticker/inoculant products addabout 5 percent to seed weight.

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 to see the extent of nodulation. Slice open nodules.A pink or reddish interior indicates active N-fixation. Remember, an overabundance of soilnitrogen from fertilizer, manure or compost can reduce nodulation.

For more information about nodulation,see two books by Marianne Sarrantonio:Northeast Cover Crop Handbook (1994,Rodale Institute, Kutztown, Pa. 19530) pp. 35-49, and Methodologies for Screening Soil-Improving Legumes (1991, Rodale Institute Research Center) pp. 63-67.


stock farms in an era of decreasing governmentpayments for corn and soybeans (122,123).

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 normalmonoculture 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 (290).

Vegetable overseeding. Berseem can be over-seeded into spring vegetables in northernclimates where it thrives at moderate tempera-tures and moisture. Berseem iswell suited to a “mow andblow” system where strips ofgreen manure are chopped andtransferred to adjacent cropstrips as a green manure andmulch (302).

Boost the N plow-downpotential of old pastures orwinter-killed alfalfa by no-tillingor interseeding berseem clover. Or, broadcast seed then incorporate with light harrowing.

COMPARATIVE NOTES

Berseem clover is:• Similar to alfalfa in drought tolerance, but

some cultivars can tolerate more soil moisturethan alfalfa or sweet clover

• Similar in seed size to crimson clover

• Bee-friendy because its white or ivory blos-soms have no tripping mechanism.

• Because of its short roots, berseem clover doesnot utilize 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.

SEED

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 (127). MatureBIGBEE plants hold their seeds well and produceadequate hard seed for reseeding. Other berseemclover cultivars have less hard seed and will notdependably reseed (225).

California tests show MULTICUT berseem cloverproduces 20 to 25 percent more dry matter thanBIGBEE. It has greater N-fixing ability, blooms later,and has a longer growing period than other

varieties, but is not as coldtolerant as BIGBEE (127).

In California, BIGBEE begins to flower in mid-May, about two weeks ahead of MULTICUT.MULTICUT grows faster and pro-duces more dry matter in Cali-fornia conditions, averagingabout 1.6 T/A more in a six-yearstudy. When the five or six

cuttings per year were clipped and removed,MULTICUT was about 6 inches taller at each clippingthan other varieties (368). In Montana tests, BIGBEE

out-yielded MULTICUT in eight of 13 locations (314).

Seed sources. Albert Lea, Cal/West, Harmony,L.L. Olds, Peaceful Valley, Pennington, Rupp,Sexauer, Welter and Wolf River. (Cal/West andWelter have MULTICUT). See Seed Suppliers(p. 166).

Mow strips of berseembetween vegetable rowsand blow the clippingsaround the plants formulch.

COWPEAS 95

Cowpeas are the most productive heat-adapted legume used agronomically in theU.S. (221). They thrive in hot, moist zones

where corn flourishes, but require more heat foroptimum growth (211). 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 produce 100to 150 lb.N/A.Dense residue helps to improve soiltexture but breaks down fairly quickly. Excellentdrought resistance combined with good toleranceof heat, low fertility and a range of soils make cow-peas viable throughout the temperate U.S. wheresummers are warm or 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 broad-cast cowpea plantings quickly shade the soil to

block out weeds.Thick stands that grow well canout-compete bermudagrass where it does not pro-duce seed and has been plowed down beforecowpea planting (211). TROY cowpeas producedan average of about 5,100 lb. dry matter/A in atwo-year Nebraska screening of cover crops.Soybeans averaged about 7,800 lb. DM/A incomparison plots (271).Typical biomass produc-tion is 3,000 to 4,000 lb./A (302).

Quick green manure. Cowpeas nodulateprofusely, producing an average of about 130 lb.N/A in the East, and 200 lb. N/A in California.Properly inoculated in nitrogen deficient soils,cowpeas can produce more than 300 lb.N/A (91).Plowdown often comes 60 to 90 days after plant-ing in California (221). 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 (302).

IPM insectary crop. Cowpeas have “extrafloralnectaries”—nectar-release sites on petioles andleaflets—that attract beneficial insects, includingmany types of wasps,honeybees,lady beetles,ants

COWPEASVigna unguiculata

Also called: southern peas,blackeye 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 for mulch or plow-down beforevegetables; interseeded with cornor sorghum


summer annualminimal irrigation-establishment only


and soft-winged flower beetles (351). Plants havelong, slender round pods often borne on barepetioles above the leaf canopy.

Intercropping cotton with cowpeas in Indiaincreased levels of predatory ladybugs and para-sitism of bollworms by beneficial wasps. Inter-cropping with soybeans also increased parasitismof the bollworms compared with plots inter-cropped with onions or cotton without an inter-crop. No effects on overall aphid, leafhopper orbollworm populations were observed (351).

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 more temper-ate areas of California. Avoid use under a heavy tree canopy,however,as cowpeas are susceptible tomildew if heavily shaded (211).As in much of thetropical world where cowpeas are a popular foodcrop,they can be underseeded into corn for late-sea-son weed suppression and post-harvest soil cover-age (302).

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 240 days.Cowpeas make hay or forage of highest feed valuewhen pods are fully formed and the first haveripened (91). A regular sickle-bar mower worksfor the more upright-growing cultivars (91, 351).Crimping speeds drying of the rather fleshy stemsto avoid over-drying of leavesbefore baling.

Low moisture need. Oncethey have enough soil moistureto become established, cow-peas are a rugged survivor ofdrought. Cowpeas’ delayed leafsenescence allows them to survive and recoverfrom midseason dry spells (15). Plants can sendtaproots down nearly 8 feet in eight weeks toreach moisture deep in the soil profile (81).

Cultivars for diverse niches. Cover crop culti-vars include CHINESE RED, CALHOUN and RED RIPPER,

all viny cultivars noted for superior resistance torodent damage (258). IRON AND CLAY, a mixture oftwo formerly separate cultivars widely used in theSoutheast, combines semi-bushy and viny plantsand resistance to rootknot nematodes and 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-cessing,and “blackeye peas,”grown for dry seed inCalifornia.

Use leafy,prostrate cultivars for the best erosionprevention in a solid planting. Cultivars vary sig-nificantly in response to environmental condi-tions. Enormous genetic diversity in more than7,000 cultivars (91) throughout West Africa,SouthAmerica and Asia suggests that breeding for forageproduction would result in improved cultivars(15, 351) and cover crop performance.

Easy to establish. Cowpeas germinate quicklyand young plants are robust, but they have moredifficulty emerging from crusted soils thansoybeans.

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 (81).Cowpeas for green manure can be sown later in

summer (302),until about nineweeks before frost. Cowpeasgrow in a range of well-drainedsoils from highly acid to neu-tral,but are less well adapted toalkaline soils. They will notsurvive in waterlogged soils or flooded conditions (91).

In a moist seedbed, drill cowpeas 1 to 2 inchesdeep at about 30 to 90 lb./A,using the higher ratein drier or cooler areas or for larger-seeded culti-vars (302, 351). 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 weed

Cowpeas thrive underhot, moist conditions,but also tolerate droughtand low soil fertility.

COWPEAS 97

control if you go with rows, using pre-cultivationor 2,4-D and MCPA.

If you broadcast seed, increase the rate to about100 lb./A and till lightly to cover seed. A lower rate of 70 lb./A can work with good moisture andeffective incorporation (302). Broadcast seedingusually isn’t as effective as drilling, due to cow-peas’ large seed size. You can plant cowpeas after harvesting small grain, usually with a singledisking if weed pressure is low. No-till planting isalso an option. Use special “cowpea” inoculantwhich also is used for sunn hemp (Crotolariajuncea),another warm-season annual legume.SeeUp-and-Coming Cover Crops (p. 158).

Field Management Cowpea 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 (302) for quickestrelease of plant nutrients.Pods turn cream or brownupon maturity and become quite brittle. Stemsbecome more woody and leaves eventually drop.

Crop duration and yield are markedly affectedby night and day temperatures as well as daylength. Dry matter production peaks at tempera-tures of 81 F day and 72 F night (91).

KillingMowing at any point stops vegetative develop-ment, but may not kill plants without shallowtillage. Recent tests show mowing and rollingalone do not consistently kill cowpeas (69).Herb-icides that control cowpeas include glyphosate,paraquat, 2,4-D and dicamba (25).

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 (69, 256,63). Insect damage to cowpea cover crops is most likely to occur at the seedling stage.

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 of

screening in North Carolina. If stinkbugs are aconcern, remember these points:

• Flail mowing or incorporating cowpeas atpod set will prevent a stinkbug invasion. By thattime, cowpeas can provide good weed suppres-sion and about 90 percent of their nitrogen con-tribution (256). However, waiting too long beforemowing or incorporation will flush stinkbugsinto adjacent crops. Leaving remnant strips ofcowpeas to attract stinkbugs may reduce move-ment into other crops, as long as the cowpeaskeep producing enough new pods until the cashcrop is no longer threatened.

• Plan crop rotations so the preceding,adjacentand succeeding crops are not vulnerable or areresistant to stinkbugs.

• If you plan to use an insecticide to controlanother pest, the application may also help man-age stinkbugs (263).

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 reducedisease and nematode risks, rotate with four orfive years of crops that aren’t hosts. Also plantseed into warm soils and use certified seed oftolerant varieties (81). IRON and other nematode-tolerant cowpea cultivars reduced soybean cyst

COWPEAS (Vigna unguiculata)

Mar

ian

ne

Sarr

anto

nio


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 untilwe plant 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 lateApril, disks in May and field cultivates justbefore planting about the first week of June. He drills 30 to 40 lb./A of CHINESE RED

cowpeas 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 or by incorporating them for maximum soilbenefit.

French says cowpeas usually produce about 90 to 120 lb. N/A—relatively modest fora legume 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 field culti-vator 1 to 2 inches deep just before plantingwheat to set back fall weeds, targeting a 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 rainfallafter 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 incompliance with new USDA farm programprovisions.The Freedom to Farm Act 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 is working with Rhonda Janke ofKansas 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 levels will give farmers new ways to evaluatemicrobial activity and overall “soil health.”

Cowpeas Provide Elegant Solution to Awkward Niche

and rootknot nematode levels in greenhouseexperiments (351). Despite some research (351)showing an increased nematode risk aftercowpeas, California farmers report no suchproblem (256).

Crop SystemsCowpeas’ heat-loving nature makes them an idealmid-summer replenisher of soil organic matter

and mineralizable nitrogen. Cowpeas set podsover a period of several weeks. Viny varietiescontinue 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 thenormal cowpea seeding rate with a fast-growing,

COWPEAS 99

drought-tolerant sorghum-sudangrass hybridincreases dry matter production and helps sup-port the cowpea plants for mowing (256).Cowpeas also can be seeded with other tall annu-al crops such as pearl millet (see Up-and-ComingCover Crops, p. 158). Overseeding cowpeas intonearly mature spring broccoli in June in Zones 5and 6 of the Northeastsuppresses weeds whileimproving soil (302). Plantingcowpeas in late June or earlyJuly in the upper Midwestafter spring canning peas pro-vides green manure or anemergency forage crop (351).

Cowpeas can fill a mid-summer fallow niche in inland North Carolinabetween spring and summer vegetable crops. Amix of IRON AND CLAY cowpeas (50 lb./A) andGerman millet (15 lb./A) planted in late June canbe killed mechanically before no-till transplantedfall broccoli. In several years of screening trials atthe same sites, cowpea dry matter (3,780 lb./A)out yielded soybeans (3,540 lb. DM/A), but plotsof sesbania (Sesbania exaltata) had top yields atabout 5,000 lb. DM/A (69).

COMPARATIVE NOTES

Cowpeas are more drought tolerant than soy-beans, but less tolerant of waterlogging (302) and

frost (211). 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 (351). Cowpeas per-form better than clovers and alfalfa on poor or

acid soils. Cowpea residuebreaks down faster thanwhite sweetclover (302)but not as fast as Austrianwinter peas.

Warm-season alterna-tives to cowpeas includetwo crops that retain somecowpea benefits. Buck-

wheat provides good beneficial habitat andweed control without attracting stinkbugs.Velvetbeans (Mucuna deeringiana) provide nitro-gen, soil protection and late-season forage in hot,long-season areas. They do not attract stinkbugs and are resistant to nematodes (81,263).

SEED

Cultivars. See Cultivars for diverse niches(p. 96).

Seed sources. Adams-Briscoe, Frazier, Lohse Mill,Mangelsdorf, Peaceful Valley and Pennington. SeeSeed Suppliers (p. 166).

Unlike many grain legumes,cowpeas can leave a net Ngain even if seeds areharvested.


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 staple for-age 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.

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 especially

well before grain sorghum, which is planted laterthan corn. It is being tested extensively in no-tilland zone-till systems.One goal is to manage to letthe legume reseed yearly for no-cost, season-longerosion control, weed suppression and nitrogenbanking for the next year.

Along the northern edge of the “crimson cloverzone,” 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 (151).

Crimson clover is gaining popularity as awinter-killed annual, like oats, in Zones 5 and cold-er. Planted in late summer, it provides goodgroundcover and weed control as it fixes nitrogenfrom the atmosphere and scavenges nitrogenfrom the soil. Its winterkilled residue is easy tomanage in spring.

Biomass. As a winter annual, crimson clover canproduce 3,500 to 5,500 lb. dry matter/A and fix70 to 150 lb. N/A by mid-May in Zone 8 (theinland Deep South). In a Mississippi study, crim-son clover had produced mature seed by April 21,as well as 5,500 lb. DM and 135 lb. N/A. The study concluded that crimson clover is one of

CRIMSON CLOVERTrifolium incarnatum

Type: winter annual or summerannual legume

Roles: N source, soil builder, ero-sion prevention, reseeding inter-row ground cover, forage

Mix with: rye and other cereals,vetches, annual ryegrass, subclover,red clover, black medic

See charts, p. 47 to 53, for rankingand management summary. marginal (limited by heat, rainfall, short season)

not recomended summer annual winter annual

CRIMSON CLOVER 101

several winter annual legumes that can provideadequate but not excessive amounts of N forsouthern grain sorghum production (16, 23, 79).Crimson clover has produced more than 7,000 lb.DM/A several times in recent years at a USDA-ARSsite in Beltsville,Md.,where it produced 180 lb.Nand 7,800 lb. DM/A in 1996 (341).

As a summer annual in lower Michigan, a mid-summer planting of crimson clover seeded at 20lb./A produced 1,500 lb.dry matter and 50 lb.N/Aby late November (140).

Companion crop. Crimson clover grows well inmixtures with small grains, grasses and otherclovers. An oats crop is a frequent companion,either as a nurse crop to establish a clear stand ofcrimson clover,or as a high-biomass,nutrient-scav-enging partner. In California, crimson clover isplanted with rose clover and medics in orchardsand nut groves to minimize erosion and providesome N to tree crops (351).

In field trials of six annual legumes inMississippi, 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 (352).

Beneficial habitat and nectar source. Crimsonclover has showy, deep red blossoms 1/2 to 1 inchlong. They produce abundant nectar, and arevisited frequently by various types of bees. Theblooms may contain many minute pirate bugs, animportant beneficial insect that preys on manysmall pests, especially thrips (351). Georgiaresearch shows that crimson clover sustains pop-ulations of pea aphids and blue alfalfa aphids.These species are not pests of pecans,but providealternative food for beneficial predators such aslady 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 (139,213).Mixed with annual ryegrass in a simulated rainfallstudy, crimson clover reduced runoff from theherbicide lactofen by 94 percent and norflurazonand fluometuron by 100 percent (286). 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. Crimson clover establish-ment requires moderate temperature and mois-ture, but seedlings are rather robust thanks tocrimson clover’s relatively large seed size. Onceestablished, it thrives in cool, moist conditions.Dry soil often hinders fall plantings in the South.

Inoculate crimson clover with an R-type (crim-son clover-berseem) inoculant. Research inAlabama showed that deficiencies of phosphorusor potassium—or strongly acidic soil with a pH ofless than 5.0—can virtually shut down N fixation.Nodules were not even formed at pH 5.0 in thetest. Phosphorus deficiency causes many smallbut inactive nodules to form (144).

CRIMSON CLOVER (Trifolium incarnatum)

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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 goto seed in the fall and not regrow in spring untilthe soil warms up enough to germinate seeds.Early to mid-August seeding is common in thenorthern part of crimson clover’s winter-annualrange.While October plantings are possible in thelower Mississippi Delta,an August 15 planting in aMississippi test led to higher yields than laterdates (182). In the lower Coastal Plain of the GulfSouth, crimson clover can be planted until mid-November (277).

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, researchershave successfully establishedcrimson clover after short-seasoncrops such as snap beans (140).

In Northern corn fields,Michigan studies showed thatcrimson clover can be overseed-ed at final cultivation (layby)when corn is 16 to 24 inches tall.Crimson cloverwas overseeded at 15 lb./A in 20-inch bandsbetween 30-inch rows using insecticide boxesand an air seeder.The clover established well andcaused no corn yield loss (238). Crimson cloverhas proved to be more promising in this nichethan black medic, red clover or annual ryegrass,averaging 1,500 lb. DM/A and more than 50 lb.N/A (140).

In Maine, spring-seeded crimson clover canyield 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 winter-kill. It sometimessurvives the winter even in southern Michigan(205), however, so northern experimentersshould maintain a spring-kill option if icy windsand heaving don’t do the job.

In California, spring sowing often results instunting, poor flowering and reduced seed yield,and usually requires irrigation (351).

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 maximum N 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 uselonger season cultivars where regrowth fromhard seed would cause a weed problem.

Researchers have successfully strip-tilled intostanding crimson clover when 25 to 80 percent of

the row width is desiccated witha herbicide or mechanically tilledfor the planting area. Narrowerstrips of crimson clover increasedweed pressure but reduced mois-ture competition, while widerstrips favored reseeding of thecover (187, 353).

In a crimson clover-before-corn system, grow-ers can optimize grain yields by no-tilling intothe crimson clover and leaving the residue onthe surface, or optimize total forage yield by har-vesting the crimson clover immediately beforeplanting corn for grain or silage (160). InMississippi, sweet potatoes and peanuts sufferedno yield or quality penalty when they were no-tilled into killed crimson clover. The systemreduced soil erosion and decreased weed com-petition (21).

In Hardiness Zone 5and colder, crimsonclover can provide awinterkilled mulch.

CRIMSON CLOVER 103

In Ohio, crimson clover mixed with hairyvetch, 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-lasting 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 (72).

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. Crimsonclover development is similar totall fescue. It even can be estab-lished with light incorporationin existing stands of aggressivegrasses after they have beenclosely mowed or grazed.

Reseeding. Overwintered crimson clover needssufficient moisture at least throughout April toproduce seed. Cultivar selection is critical whenearly spring maturity is needed.

DIXIE and CHIEF are full-season standards. AUROBIN and FLAME beat them by about two weeks,while the popular TIBBEE is about a week ahead ofthe standards. A new cultivar—AU CRIMSON, thatreportedly would be three weeks earlier—is stillunder development. Price varies more by season-al supply than by cultivar.

Killing. Its simple taproot makes crimson clovereasy to kill mechanically. Mowing after early budstage will kill crimson clover. Maximum N isavailable at late bloom or early seed set, evenbefore the plant dies naturally. Killing earlieryields less N—up to 50 lb. N/A less at its late veg-etative stage, which is about 30 days before earlyseed set (283).

A rolling stalk chopper flattens a mix of crim-son clover, hairy vetch and rye ahead of no-tillvegetable 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.Small amounts of metribuzin applied two tothree weeks after transplanting handle anyregrowth and provide season-long weed control,as well (132). Glufosinate-ammonium, paraquat,cyanazine and glyphosate are other herbicidesused to kill crimson clover (205).

Pest ManagementCrimson clover is a secondary host to plant pestsof the Heliothus species, which include corn ear-worm and cotton bollworm. Despite its knownbenefits,crimson clover has been eradicated frommany miles of roadsides in Mississippi at the

request of some Delta farmerswho suspect it worsens prob-lems from those pests (77).

Crimson clover doesn’t sig-nificantly increase risk ofSouthern corn rootworm in no-till corn,while hairy vetch does(47). It is more resistant to dis-

eases (351) and to some nematodes than otherclovers (276). Crimson clover is said to tolerateviral diseases, but it succumbed to virus in Julyplantings in Mississippi (182) and to Sclerotiniain fall plantings in Maryland (83).

In lab tests, crimson clover,berseem clover andhairy vetch have been shown to inhibit germina-tion and seedling development of onion, carrotand tomato (26). However, this interference has-n’t been observed in North Carolina field cropswhere strips are mechanically tilled (353), or inother studies with crimson clover as part of akilled organic mulch. No-till vegetable transplant-ing has been done successfully on the same day as mechanically killing the cover crop mix onSteve Groff’s Lancaster County, Pa., farm with nonegative effects (132).

Wait two to three weeks after incorporatingcovers before planting seeds,to allow the biomassto begin to decompose and the soil biological life

In Mississippi, crimsonclover produced matureseed and 135 lb. N/A by April 21.


to stabilize. During this time, a flush of bacteriasuch as Pythium and Rhizoctonia attack rapidlydecaying plants. These bacteria also can attackseedling crops. To plant more quickly, mow theclover and use row cleaners to clear the tops fromthe seed zone. The mow/wait/plant cycle alsomay be influenced by the need to wait for rain toincrease seedbed moisture.

Mixed with hairy vetch,crimson clover attractsbeneficial 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 (320) and is verysusceptible to root knot nematode.

Crimson clover harbors flower thrips and is amore likely host for tarnished plant bug thanhairy vetch or subterranean clover (38). Intensivescreenings show less abundant arthropod herbi-vores and predators on crimson clover than onhairy vetch (162).

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 (212).

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 theearly bud stage. Mixing with grass reduces its rel-atively low bloat risk even further. Seedheads areeasily accessible by grazing livestock, leading to

reseeding via cattle manure.Timely mowing fourto six weeks before bloom improves growth,reduces lodging and will cause more uniformflowering and seed ripening on highly fertile soils(91, 351).

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 (60).

COMPARATIVE NOTES

Crimson clover is:• less tolerant of mowing than are subclovers or

medics (351)• similar to hairy vetch and Austrian winter pea

in the Southeast for total N production• quicker-growing than hairy vetch in fall and

spring• a better weed suppressor in fall than hairy

vetch• earlier to mature in spring than hairy vetch

Crimson clover produces more dry matter thansweetclover or hairy vetch on a given amount ofrainfall.

SEED

Cultivars. See Reseeding (p. 103) for cultivarcomparisons.

Seed Sources. Forage suppliers, includingAmpac, Kaufman, Missouri Southern, PeacefulValley, Pennington and Sexauer. See SeedSuppliers (p. 166).

FIELD PEAS 105

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


which can destroy whole fields during winter inthe mid-Atlantic area.Risk of infection increases ifpea crops are grown on the same land in closerotation (82).

Canadian field peas are a related strain ofvining pea. These annual “spring peas” can out-grow spring-planted winter peas. They often are seeded with triticale or another small grain.Spring peas have larger seeds, so there are fewerseeds per pound and seeding rates are higher,about 100 to 160 lb./A (237). However, spring pea seed is a bit less expensive than Austrianwinter pea seed (347). TRAPPER is the most com-mon Canadian field pea cultivar.

This section focuses on the widely grownAustrian winter pea. “Field peas” refers to both the winter 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 colderclimates. Idaho farmers regularly produce 6,000to 8,000 lb. DM/A from fall-planted Austrian

FIELD PEAS

summer annual winter annual

High N-fixers, field peas produce abundantvining forage and contribute to short-term soil conditioning. Succulent stems

break down easily and are a quick source of avail-able N (302). Field peas grow rapidly in the cool,moist weather they encounter as winter annualsin the South and in parts of Idaho, and as early-sown summer annuals in the Northeast, NorthCentral and Northern Plains areas. Harvestoptions as high-quality forage and seed increasetheir value.

Winter-hardy types of field peas, especiallyAustrian 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 (302), where averagesummers have fewer than 30 days exceeding 86 F.Temperatures greater than 90 F cause flowers toblast and reduce seed yield. On humus-rich blacksoils, field peas will produce abundant vinygrowth with few seed pods.

Use in the East and Southeast is limited by fieldpeas’ susceptibility to Sclerotinia crown rot,


winter peas (135). Because the residue breaksdown quickly, only peas in the high-productionareas build up much long-term organic matter.Peas do not make a good organic mulch for weedcontrol (302).

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-plantedlegume 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 pro-duced 96 lb.N/A the first year and 207 lb.N/A thesecond (317).

Austrian winter peas harvested as hay thenapplied as mulch mineralized N at more thandouble the rate of alfalfa hay.The N contributionwas measured the summer after a fall plowdown ofthe residue.The estimated N recovery of Austrianwinter pea material 10 months after incorporationwas 77 percent—58 percent through spring wheatand 19 percent in the soil (202).

Austrian winter pea green manure provided thehighest 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 (314). 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 (53).

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 seed left less soil N than did plots in fallow. Alsotested were fava bean, lentil,chickpea,spring pea,winter pea hay and dry bean (210).

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 (128).

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 (316).

Austrian winter peas grown in a controlledsetting at 50 F recorded more than 75 percent ofits N2 fixed per unit of water used by the 63rd day of growth. White clover, crimson clover andhairy vetch reached the same level of water effi-ciency, but it took 105 days (273).

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. In the Pacific Northwest, marketprices have ranged up to $11 per hundredweight. University of Montana economists esti-mate potential gross returns of $83 to $165/A onyields of only 1,500 lb./A. Demand is growing forfield peas as food and livestock feed (53).

Long-term bloomer.The purple and white blos-soms of field peas are an early and extendedsource of nectar for honeybees.

FIELD PEAS 107

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 coverusually kills Austrian winter pea (158). To maxi-mize winter survival:

• Select the most winter-hardy cultivars avail-able—GRANGER, MELROSE and COMMON WINTER.

• Seed early enough so that plants are 6 to 8inches tall before soil freezes,because peas are shal-low rooted and susceptible to heaving. Try to plantfrom mid-August to mid-September in Zone 5.

• Plant into grain stubble or a rough seedbed,or interseed 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 in North Carolina (282).Field peas usually are drilled1 to 3 inches deep to ensure contact with moistsoil and good anchoring for plants.

If you broadcast peas, incorporation will great-ly improve stands,as seed left exposed on the sur-face 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,Austrianwinter peas make a good nurse crop for alfalfa (274).

Field pea seed has a short shelf life comparedwith 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 arefall-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 after beingflail-mowed and disked in early April.

The general rule for other parts of the semi-aridWest 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 (316).

In the low-rainfall Northern Plains, broadcastclear 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 (316).Plant as soon as soil in the top inch reaches 40 Fto make the most of spring moisture (53).

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A mixture of Austrian winter peas and a smallgrain is suitable for dryland forage productionbecause it traps snow and uses spring moisture toproduce high yields earlier than spring-seededannual forages (53). With sufficient moisture,spring peas typically produce higher forage yieldsthan Austrian winter peas.

East. Planted as a companion crop in early springin the Northeast, Austrian winter peas may pro-vide appreciable plowdown N for summer cropsby Memorial Day (302). In the mid-Atlantic,Austrian winter peas and hairy vetch planted Oct.1 and killed May 1 produced about the same totalN and corn yields (83).

Southeast. Seed by October 1 in the inland Zone8 areas of the South so that root crowns canbecome established to resist heaving.Peas producemore biomass in the cooler areas of the South thanwhere temperatures rise quickly in spring (53,302). Peas planted in late October in SouthCarolina’s Zone 8 and terminated inmid- to late April produce 2,700 to4,000 lb.dry matter/A (17).

KillingPeas are easily killed by disking ormowing after full bloom, the stageof maturity that provides the optimum N contri-bution.Disk lightly to preserve the tender residuefor some short-term erosion control.

The downside to the quick breakdown of peavines is their slimy condition in spring if they win-terkill, especially in dense, pure stands. Plantingwith a winter grain provides some protectionfrom winterkill and reduces matting of dead peavegetation (230).

Pest ManagementWinter peas break crop disease cycles,Ben Burkettof Petal, Miss., has found. Septoria leaf spot prob-lems on his cash crops are reduced when he plantsAustrian winter pea in fall after snap beans andahead of collards and mustard greens the next sum-mer. Between October 15 and November 15,Burkett broadcasts just 50 lb./A then incorporates

the seed with a shallow pass of his field cultivator.They grow 3 to 6 inches tall before going dormantin late December in his Zone 8 location about 75miles north of the Gulf of Mexico.Quick regrowthstarts about the third week in January. He kills them in mid-April by disking, then shallow plowsto incorporate the heavy residue (158).

Farmers and researchers note several IPMcautions, because Austrian winter peas:• Host some races of nematodes• Are susceptible to winter Sclerotinia crown

rot, 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 (185).Austrian winter peas were heavily damaged by

Sclerotinia trifoliorum Eriks in several years of afour-year study in Maryland,but the crop still pro-

duced from 2,600 to 5,000 lb. drymatter/A per year in four out offive years. One year DM produc-tion was only 730 lb./A. Mean Ncontribution despite the diseasewas 134 lb. N/A. Overall, Austrianwinter peas were rated as being

more suited for Maryland Coastal Plain use than inthe Piedmont,due to harsher winters in the latterlocation (160).

To combat disease, rotate cover crops to avoidgrowing peas in the same field in successive years.To minimize disease risk, waiting several years isbest. To minimize risk of losing cover crop benefits to Sclerotinia disease in any given season,mix with another cover crop such as cereal rye.

Crop SystemsNorthern Plains. Austrian winter pea is a topcandidate for dryland grain legume>cereal rota-tions designed to save N and be adaptable tovarying amounts of soil moisture. The sequencestarts with a spring- or fall-planted grain legumewhose residue substitutes for fallow, followed bythe usual local small grain.

Winter pea residuebreaks down andreleases N quickly.

FIELD PEAS 109

In a “Flexible Green Manure” cropping system,the guiding management principles call for thegrain legume to be controlled based on the:• season’s rainfall• crop’s N fixation• anticipated moisture and N need of the

following crop When managing for moisture, farmers look at

three management paths for their Austrian winterpeas or other grain legume:• Deficient moisture—incorporate the grain

legume early to initiate summer fallow.• Adequate moisture—terminate the grain

legume when about 4 inches of groundwaterhave been used. Residue is maintained forgreen manure, moisture retention and erosionprevention.

• Above-average moisture—crop is left tobear seed for harvest.In conventional fallow systems using tillage or

herbicide, soil is left unplanted to allow organicmatter to mineralize during a non-crop year toincrease available plant nutrients. Fallow systems,however, still require N fertilizer to compensatefor the net loss of native soil fertility and have led to many environmental problems. Theseinclude saline seep and nitrate pol-lution of groundwater due toleaching of nutrients during thefallow period.

Grain legumes provide a soil-protecting alternative that more Nthan fallow.The legumes also dis-rupt disease, insect and weedcycles and contribute to long-term soil-buildingwhere limited moisture slows organic matterbreakdown. Austrian winter peas work in theserotations where there is at least 18 inches of rainper year. INDIANHEAD lentils (Lens culinarisMedik), a specialty lentil for cover crop use, iswidely used 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. When the legume generates income fromharvest of its hay or grain, fertilizer N savings from

the legume year’s contribution to the small grainmay top $15/A (316).

In Idaho, fall-seeded Austrian winter peas har-vested for seed provided income, residual N fromthe pea straw and soil disease suppression in a study of efficient uses of the legume cover. Acrop rotation of Austrian winter pea>winterwheat>spring barley produced similar wheatyields as did using the peas as green manure orallowing soil organic matter to break downduring summer 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 (201).

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 subsequent cashcrops, higher income and improvement of soilquality (8).

Southeast. Fall-seeded Austrianwinter peas out-produced hairyvetch by about 18 percent in bothdry matter and N production in athree-year test in the Coastal Plainof North Carolina.When legumeswere grown with rye, wheat or

spring oats,Austrian winter pea mixtures also hadthe highest dry matter yields. Over the threeyears, Austrian winter peas ranked the highest(dry-matter and N) in the legume-only trials and asthe legume component of the legume/grain mix-tures. In descending order after the peas werehairy vetch, common vetch and crimson clover.The peas were sown at 54 lb./A in the sole-seed-ings and 41 lb./A in mixtures (285).

In the year of greatest N fixation, soil N in theAustrian winter peas mixture treatments was 50percent greater than the average of all other treat-ments. Researchers noted that the bottom leaves

In the Northeast,spring-planted peascan be incorporatedby Memorial Day.


of 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 than30 percent in the top soil layer for all other treat-ments. In situations where the early-summer N

release from peas could be excessive, mixingAustrian winter peas with a grain can moderatethe N contribution and slow down its release intothe soil (285).

The carbon to nitrogen (C:N) ratio of plant mat-ter is an indication of how rapidly vegetation willbreak down. Mixtures of small grains withAustrian winter peas and the vetches had C:N

Peas Do Double Duty for Kansas FarmerPARTRIDGE, 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 sandyloam 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-Octoberhe inoculates about 30 lb./A of the peas anddrills them with an old John Deere double-rundisk drill in 8-inch rows. Establishment isusually good, with his only anxiety comingduring freeze-thaw cycles in spring.“Each timethe peas break dormancy, start to grow, thenget zapped with cold again they lose some oftheir root reserves and don’t have quite theresistance to freezing they did.They’ll sproutback even if there’s vegetative freeze damageas long as their food reserves hold out,”Frenchreports.

Ironically, this spring freezing is less of aproblem 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 120lb.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 hisgrain sorghum because it provides N whilereducing weed pressure from cheatgrass andpigweed and decreasing lodging from charcoal root rot.The option to use the peas as forage—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 integratecrops and livestock,” says French.“They giveyou so many benefits.”

FIELD PEAS 111

values from 13 to 34,but were generally under 25to 30, the accepted threshold for avoiding netimmobilization of N (285).

Austrian winter peas and crimson clover canprovide adequate N for conventionally plantedcotton in South Carolina. In a three-year trial, fer-tilizer rates of up to 150 lb.N/A made no improve-ment to cotton yield on the pea plots. Theevaluation showed that soil nitrate under Austrianwinter peas peaked about nine weeks after incor-poration (16).

Austrian winter peas achieved 50 to 60 percentgroundcover 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 (147). Overseeding peas into corn at lastcultivation is not recommended due to poorshade tolerance.

Austrian winter peas, like otherhollow-stemmed succulent cov-ers such as vetch and fava beans,do not respond well to mowingor cutting after they begin tobloom. In their earlier stages,Austrian winter peas will regroweven when grazed several times. See Peas DoDouble Duty for Kansas Farmer (p. 110).

After three years of moisture testing, Kansasfarmer Jim French can explain why he sees moresoil moisture after spring grazing than when thepeas are left to grow undisturbed. “There’sdecreasing overall transpiration because there’sless leaf area to move moisture out of the soil intothe air. Yet the root mass is about the same.”Ungrazed peas pump more water as they keepgrowing.

Other OptionsHarvest 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 (147). When selecting types,remember that long-vined varieties are better forweed control than short-vined types.

SEED

Cultivars. MELROSE, known for its winterhardi-ness, is a cultivar of the Austrian winter pea type.Planted the first week of September in Idaho,MELROSE peas yielded 300 lb.N/A and 6 tons of dry

matter the next June. Planted inmid-April, the cultivar yielded“just” 175 lb. N/A and 3.5 T drymatter/A (158).

GRANGER is an improvedwinter pea that has many fewerleaves and more tendrils, whichare stiffer than standard culti-

vars. It is more upright and its pods dry morequickly than other winter pea types. Seed isexpected to be commercially available in 1999(232). MAGNUS field peas have out-producedAustrian winter peas in California (168) andbloom up to 60 days earlier (256).

Seed sources. Forage crop suppliers, and Albright, Ampac, Ernst, Fedco, Lohse, Peaceful,Tennessee,Timeless and Wolf. See Seed Suppliers(p.166).

In dryland systems,winter peas produceabundant biomasswith limited moisture.


Few legumes match hairy vetch for springresidue production or nitrogen contribu-tion. Widely adapted and winter hardy

through the warmer parts of Hardiness Zone 4,hairy vetch is a top N provider in temperateregions.

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 exceeds 3 feet unless the vetch is supported byanother crop. Its abundant, viny biomass can be abenefit and a challenge. The stand smothersspring weeds, however, and can help you replaceall or most N fertilizer needs for late-plantedcrops.

BENEFITS

Nitrogen source. Hairy vetch delivers plenty ofresidue to condition soil and heavy contributionsof N in mineralizable form (readily available to thefollowing cash crop). It can provide sufficient Nfor many vegetable crops, partially replace N fer-tilizer for corn or cotton and increase the crop’sN efficiency for higher yield.

In some parts of California (168) and the East inZone 6, hairy vetch provides its maximum N bysafe corn 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 (287).

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 than under cereal rye orwith no cover crop. Killed vetch left on the sur-face conserved summer moisture for improvedcorn production (60, 62, 64, 82, 136, 192).

Even without crediting its soil-improving ben-efits, 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 test.The economic risk comparison included crim-son clover, wheat and winter fallow. Profit washigher, but less predictable, if 50 pounds of Nwere added to the vetch system (250).

Hairy vetch ahead of no-till corn was also thepreferred option for risk averse farmers in a three-

HAIRY VETCHVicia villosa

Type: summer annual or winterannual legume

Roles: N source, weed suppressor,topsoil conditioner

Mix with: strong-stemmed grains,field peas, bell beans, crimsonclover


vetch superior

vetch, crimsontransition zone

vetch viable crimsonclover superior

hairy vetch viablew/irrigation

Note: To estimate hairy vetch N contribution inpounds per acre, cut and weigh fresh vetch topgrowth from a 4-foot by 4-foot area. Multiply by 12pounds to gauge available N, by 24 to find total N(310).See also How Much N? (p.22).

HAIRY VETCH 113

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 (136). 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 (192)

In Wisconsin’s shorter growing season, hairyvetch planted after oat harvest provided a grossmargin of $153/A in an oat/legume>corn rota-tion. Profit was similar to using 160 lb. N/A incontinuous corn, but with savings on fertilizerand corn rootworm insecticide (328).

Hairy vetch provides yield improvementsbeyond those attributable to N alone. These may be 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 (108). Adding grasses that take up a lot 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 dissolve in water (108).

Hairy vetch improves topsoil tilth, creating aloose and flowable 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 of

25 or more tends to immobilize N.For more infor-mation, see How Much N? (p. 22), and the rest ofthat section,Building Soil Fertility and Tilth withCover Crops (p. 16).

Early weed suppression. The vigorous springgrowth of hairy vetch out-competes weeds, fillingin where germination may be a bit spotty.Residuefrom killed hairy vetch has a weak allelopathiceffect,but it smothers early weeds mostly by shad-ing the soil. Its effectiveness wanes as it decom-poses, falling off significantly after about three orfour weeks.For optimal weed control with a hairyvetch 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 30 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 andover winter better than legumes, yet avoids thepotential crop-suppressing effect of a pure ryemulch on some vegetables (338).

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)

Mar

ian

ne

Sarr

anto

nio


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 (285).

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 a Texas trial.Soil under hairy vetch alsohad the lowest level of P remaining after growersapplied high amounts of poultry litter prior tovegetable crops (92).

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-cost seedplant vetch after winter grain harvest in mid-sum-mer to produce whatever N it can until it win-terkills—or survives to regrow in spring.

Widely adapted. Its high N production,vigorousgrowth, tolerance of diverse soil conditions, lowfertility need and winter hardiness make hairyvetch the most widely used of winter annuallegumes.

MANAGEMENT

Establishment & FieldworkSeed into freshly prepared and firmed soil.Broadcast and incorporate lightly to no more than11/2 inches deep.Dry conditions often reduce ger-mination of hairy vetch. Drill seed at 15 to 20lb./A, broadcast 25 to 30 lb./A. Select a higher rate if you are seeding in spring or late in your window, or into a weedy or sloped field.

Irrigation will help germination, but cultivation islikely to bury seeds too deeply.

Plant hairy vetch 15 to 45 days before killingfrost for winter annual management; in earlyspring for summer growth; and in July for fallincorporation or a winter-killed mulch.

Hairy vetch has a relatively high P and Krequirement 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 5.6 to 7.5 (91).

An Illinois farmer successfully no-tills hairyvetch in late August at 22 lb./A into closelymowed stands of fescue on former ConservationReserve Program land (348). Using a herbicide tokill the fescue is cheaper—$8 to $10 to spray forgrowers owning their equipment vs. $10 to $12to mow—but it must be done about a month laterwhen the grass is actively growing for the chemi-cal to be effective (267). Vetch also can be no-tilled into soybean or corn stubble (32, 60).

Farmers in the Northeast’s warmer areas plantvetch by mid-September to net 100 lb. N/A bymid-May. Sown mid-August, an oats/hairy vetchmix can provide heavy residue (138).

Rye/hairy vetch mixtures mingle and moderatethe effects of each crop.The result is a “hybrid”cover crop that takes up and holds some excesssoil nitrate, fixes N,stops erosion,smothers weedsin spring 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.The rye acts as a trellis, making theclimbing vetch easier to mow and increasing itsexposure to the sun (61, 63, 64, 310).

In a vetch/rye mixture, an appropriate seedingrate for corn production in the mid-Atlanticregion is 19 lb. hairy vetch with 42 lb. rye/A (61).A mix of 20 to 25 lb. hairy vetch and 70 lb. rye/Aworks in a variety of conditions (302),while somefarmers report success with only 40 lb. rye/A.

Overseeding (40 lb./A) at leaf-yellowing intosoybeans 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 asconsistently. Late overseeding into vegetables is

HAIRY VETCH 115

possible, but remember that hairy vetch will notstand heavy traffic (302).

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.

In spring, hairy vetch continues to add Nthrough 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.

Climate influences the results of hairy vetchresidue management. In the hot and humid con-ditions of the Southeast, no-till hairy vetchresidue appears to contribute significant N with-out incorporation. Findings elsewhere (272) indi-cate that farmers in the cooler and drier areas ofthe western Corn Belt need to manage hairyvetch with mowing and tillage to achieve peak Nbenefits by preventing N volatilization (loss intothe atmosphere).

Mulch-retaining options include strip-tilling orstrip chemical desiccation (leaving vetch untreatedbetween the strips), mechanical killing (rotarymowing, flailing, cutting, sub-soil shearing with anundercutter, or chopping/flattening with a rollingstalk chopper) or broadcast herbicide application.

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 over 15years for one researcher/farmer. He used herbi-cide to kill the vetch about two weeks before thearea’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 thickfescue thatch.

He kills the vetch when it is in its pre-bloom orbloom stage, nearing its peak N-accumulationcapacity. Further delay would risk loss of soilmoisture in the dry period customary there inearly June (267). When the no-tilled vetch was leftto grow one season until seed set, it produced 6tons of dry matter and contributed a potentiallypolluting 385 lb. N/A (348).This high dose of Nmust be managed carefully during the next yearto prevent leaching or surface runoff of nitrates.

A series of trials in Maryland showed a differentmix of conditions. Corn planting in late-April iscommon there, but early killing of vetch to plantcorn then had the surprising effect of decreasingsoil moisture and corn yield, as well as predictablylowering N contribution. The earlier-planted cornhad less moisture-conserving residue. Late April orearly May kill dates, with corn no-tilled 10 dayslater, consistently resulted in higher corn yieldsthan earlier kill dates (62,63,64). With hairy vetchand a vetch/rye mixture, summer soil water con-servation by the cover crop residue had a greaterimpact than spring moisture depletion by thegrowing cover crop in determining corn yield (64).

Results in the same trials,which also included apure 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—thanvetch alone (63).

In an Ohio trial, corn no-tilled into hairy vetchat mid-bloom in May received better early seasonweed control from vetch mulch than corn seededinto vetch killed earlier. The late planting datedecreased yield,however (145,289),requiring cal-culation to determine if lower costs for tillage,weed control, and N outweigh the yield loss.

Once vetch starts to bloom, it is easily killed byany mechanical treatment (52). 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. Rye


also increases the density of residue covering thevetch stubble to prevent regrowth.

Much quicker and more energy-efficient thanmowing 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 orfoxtail millet at 8 to 10 mph (131).

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 25lb. hairy vetch, 30 lb. rye and 10 lb. crimsonclover/A (132).

No-till, delayed kill. Jeff Moyer of the RodaleInstitute in Kutztown, Pa., no-tills corn into stand-ing hairy vetch in late May or early June, waitsseveral more days, then flail-chops the vetchbefore corn emergence. This method allows thevetch to produce maximum N and is late enoughto allow soil warming even with the vetch inplace (230).

Also useful in killing hairy vetch on raised bedsfor vegetables and cotton is the improved proto-type of an undercutter thatleaves severed residue virtu-ally undisturbed on the sur-face (70). The undercuttertool includes a flat rollerattachment, which, by itself,usually provides only partialsuppression unless usedafter flowering.

Herbicides used to kill hairy vetch includeglyphosate (only somewhat effective), paraquat,2,4-D, dicamba and triazines including atrazine,cyanazine and metribuzin.Vetch will die in threeto 30 days (338), depending on the material usedand crop conditions.

Vetch incorporation. As a rule, to gauge theoptimum hairy vetch kill date, credit vetch withadding two to three pounds of N per acre per

sunny day after full spring growth begins.Usually,N contribution by early bloom (10-25 percent)stage warrants killing the legume, rather thanaccepting yield loss due to late planting to getmarginally more N at seed set or natural dry downafter seed set.

Cutting hairy vetch close to the ground at fullbloom 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 (351).

Heavy disk harrows, rotovators and powerspaders can incorporate heavy, unmowed vetchstands. A moldboard plow can turn under largeamounts of mowed vetch. Chisel plows andlighter disks can handle vetch killed earlier withherbicides.

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 (132). Vetch seed-pods will grow above the twining vetch vines anduse the grain as a trellis, allowing you to run the

cutter bar higher to reduceplugging of the combine.Direct combine at mid-bloom to minimize shatter-ing, or swath up to a weeklater. Seed is viable for atleast five years (302).

If you want to save dollarsby growing your own seed, be aware that themature pods shatter easily, increasing the risk ofvolunteer weeds. To keep vetch with its nursecrop,harvest vetch with a winter cereal and keepseed co-mingled for planting.Check the mix care-fully for weed seeds.

Management Cautions• About 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,

Winter hardy through thewarmer parts of Zone 4, fewlegumes can rival hairyvetch’s N contributions.

HAIRY VETCH 117

especially in winter grains. With wheat, you canuse 2,4-D for control. After a corn crop that canutilize the vetch-produced N, you could establisha hay or pasture crop for several years.

• Don’t plant hairy vetch with a winter grain ifyou want to harvest grain for feed or sale.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(302). Grain price can be markedly reduced byonly a few vetch seeds per bushel (82).

• A severe freeze with temperatures less than 5F may kill hairy vetch if there is no snow cover,reducing or eliminating the stand and most of itsN value. If winterkill is possiblein your area,planting vetch witha hardy grain such as rye ensuresspring soil protection.

Pest ManagementIn legume comparison trials,hairy vetch usually hosts numerous small insectsand soil organisms (162). Many are beneficial tocrop production, (see below) but others arepests. Soybean cyst nematode (Heteroderaglycines) and root-knot nematode (Meliodogynespp.) sometimes increase under hairy vetch. Ifyou suspect that a field has nematodes, carefullysample the soil after hairy vetch.If the pests reachan economic threshold, plant nematode-resistantcrops and consider using another cover crop.

Other pests include cutworms (302) andsouthern corn rootworm (47), which can beproblems in no-till corn; tarnished plant bug—noted in coastal Massachusetts (38)—which read-ily disperses to other crops; and two-spottedspider mites in Oregon pear orchards (107).Leaving unmowed remnant strips can lessenmovement of disruptive pests while still allowingyou to kill most of the cover crop (38).

Prominent among predator beneficials associat-ed with hairy vetch are lady beetles,seven-spottedladybeetles (38) and bigeyed bugs (Geocarisspp.). Vetch harbors pea aphids (Acyrthosiphonpisum) and blue alfalfa aphids (Acyrthosiphon

kondoi) that do not attack pecans but provide afood source for aphid-eating insects that can dis-perse into pecans. (40). 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 yieldin heavy infestations: the vetch weevil or vetchbruchid.Rotate crops to alleviate buildup of thesepests (302).

CROP SYSTEMS

Killed hairy vetch creates a short-term but effec-tive spring/summer mulch, especially for trans-plants. The mulch retains moisture, allowing

plants to use mineralized nutri-ents better than unmulchedfields. The management chal-lenge is that the mulch also low-ers soil temperature, which maydelay early season growth (302).One option is to capitalize on

high quality, low-cost tomatoes that capture thelate-season market premiums. See Vetch BeatsPlastic (p. 118).

How you kill hairy vetch influences its abilityto suppress weeds.Durability and effectiveness asa light-blocking mulch are highest where thestalks are left whole. Hairy vetch severed at theroots or sickle-bar mowed last longer and blocksmore light than flailed vetch, preventing moreweed seeds from germinating (70, 340).

While there is evidence that hairy vetchexudes weak natural herbicides that may inhibitdevelopment of small onion, carrot and tomatoseedlings (26), these compounds do not affecttransplants (132).

Southern farmers can use an overwinteringhairy vetch crop in continuous no-till cotton.Vetch mixed with rye has provided similar oreven increased yields compared with systems that

Note: An unmown 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 (39).

Mix hairy vetch withcereal grains to reducethe risk of N leaching.


include conventional tillage, winter fallow weedcover and up to 60 pounds of N fertilizer per acre.Typically, the cover crops are no-till drilled aftershredding cotton stalks in late October. Coversare spray killed in mid-April ahead of cotton plant-ing in May. With the relatively late fall planting,hairy vetch delivers only part of its potential N inthis system. It adds cost, but supplies erosioncontrol and long-term soil improvement (21).

Cotton yields following incorporated hairyvetch were perennial winners for 35 years at anorthwestern Louisiana USDA site. Soil organicmatter improvement and erosion control wereadditional benefits (222).

Other OptionsSpring sowing is possible, but less desirable thanfall establishment because it yields significantly

Vetch Beats PlasticBELTSVILLE, Md.—Killed cover crop mulchescan deliver multiple benefits for no-tillvegetable crops.The system can provide itsown N, quell erosion and leaching, anddisplace herbicides. It’s also more profitablethan conventional commercial productionusing black plastic mulch. A budget analysisshowed it also should be the first choice of“risk averse” farmers.These are individualswho prefer certain although more modestprofit over higher average profit that is lesscertain (178).

The key to the economic certainty of asuccessful hairy vetch planting is its lowcost—about $80/A for seeding and mowing—compared with the black plastic at about $750for plastic, installation and removal.

From refining his own research and on-farmtests in the mid-Atlantic region for severalyears, USDA’s Aref Abdul-Baki of the ARSBeltsville (Md.) Agricultural Research Center,outlines his approach:• Prepare beds—just as you would for planting

tomatoes—at your prime time to seed hairyvetch.

• Drill hairy vetch at 40 lb./A, and expectabout 4 inches of topgrowth 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

season weeds. 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 vigorousand may yield up to 20 percent more thanthose on 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 oftomatoes, peppers and cantaloupe through thesame plot between fall hairy vetch seedings.He shallow plows the third year aftercantaloupe harvest and seeds hairy vetch forflat-field crops of sweet corn or snap beansthe following summer.

He suggests seeding rye with the vetch (40 lb./A each) for greater biomass and longer-lasting mulch. Adding 10-12 lb./A of crimsonclover will aid in weed suppression and Nvalue. Rolling the covers before plantingprovides longer-lasting residue than doesmowing them. Some weeds, particularlyperennial or winter annual weeds, can stillescape this mixture, and may requireadditional management (2).

MEDICS 119

less biomass than overwintering stands. Hotweather causes plants to languish.

Hairy vetch makes only fair grazing—livestockdo not relish it.Heavy feeding for 20 days in hairyvetch pasture resulted in death for eight of 33 cat-tle in one trial in South America (351).

COMPARATIVE NOTES

Hairy vetch is better adapted to sandy soils thancrimson clover (285), but is less heat-tolerant thanLANA woolypod vetch.See Woolypod Vetch (p.151).

SEED

Cultivars. MADISON—developed in Nebraska—tolerates cold better than other varieties. Hairyvetches produced in Oregon and California tend

to be heat tolerant. This has resulted in twoapparent types,both usually sold as “common”or“variety not stated” (VNS). One has noticeablyhairy, bluish-green foliage with bluish flowersand is more cold-tolerant. The other type hassmoother, deep-green foliage and pink to violetflowers.

A closely related species—LANA woolypodvetch (Vicia dasycarpa)—was developed inOregon and is less cold tolerant than Vicia vil-losa. Trials in southeastern Pennsylvania withmany accessions of hairy vetch showed bigflowervetch (Vicia grandiflora, cv WOODFORD) was theonly vetch species hardier than hairy vetch. EARLY

COVER hairy vetch is said to be 10 days earlier thanregular common seed (337).


MEDICSMedicago spp.

Also called: black medic, bur medic,burclover

Type: Winter annual or summerannual legume

Roles: N source, soil quality builder,weed suppressor, erosion fighter

Mix with: Other medics; cloversand grasses; small grains


annual medics perennial medics(dryland)

annual medicsmarginal utility

Once established, few other legumes out-perform medics in soil-saving,soil-buildingand forage when summer rainfall is less

than 15 inches.They serve well in seasonally dryareas from mild California to the harsh NorthernPlains. With more rainfall, however, they can pro-

duce almost as much biomass and N as clovers.Medics are self-reseeding with abundant “hardseed”that can take several years to germinate. Thismakes medics ideal for long rotations of foragesand cash crops in the Northern Plains and in covercrop mixtures in 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/A wherethe plants grow over winter. They germinate and grow quickly when soil moisture is adequate,forming a thick ground cover that holds soil inplace. The more prostrate species of annual medic provide better ground cover.

Significant annual types include: bur medic (M.polymorpha), which grows up to 14 inches tall, issemi-erect or prostrate, hairless, and offers greatseed production and N-fixing ability;barrel medic(M. truncatula), about 16 inches tall, with manymid-season cultivars; andsnail medic (M. scutellata),which is a good biomass andN producer.

Southern spotted burmedic is a native M. polymor-pha cultivar with more win-terhardiness than most of the current bur medics,which are imported from Australia. See SouthernBur Medic Offers Reseeding Persistence (p. 122).Naturalized bur medic seed is traded locally inCalifornia (58).

Annual medics broadcast in spring over wheatstubble 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 (308).

GEORGE black medic (M. lupulina) is usuallycalled a perennial. It can improve soil, reduce dis-eases, save moisture and boost grain proteinwhen grown in rotations with grains in theNorthern Plains. GEORGE is the most widely usedcultivar in dryland areas of the Northern Plains.Black medic produces abundant seed. Up to 96percent of it is hard seed,much of it so hard seed-ed that it won’t germinate for two years. Second-year growth may be modest, but coverageimproves in years three and four after the initialseeding if competition is not excessive (351) andgrazing management is timely.

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 (313, 347). Fallow is the intention-al resting of soil for a season so it will build upmoisture and gain fertility by biological break-down of organic matter. Black medic increasedspring wheat yield by about 92 percent comparedwith spring wheat following fallow, and alsoappreciably raised the grain protein level (312).

April soil N value after black medic in oneMontana test was 117 lb./A, about 2.5 times thefallow N level and the best of six cultivars tested,

all of which used less waterthan the fallow treatment(311). GEORGE grows in aprostrate to ascending fash-ion and overwinters wellwith snow cover in theNorthern Plains.

Great N from more water. Under normal dry-land conditions,medics usually produce about 1 Tdry matter/A, depending on available soil mois-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 (157, 351).

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 medicstand. 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

Hard-seeded medics areideal for reseeding systemsin orchards and vineyards.

MEDICS 121

test reported a yield of more than 9,000 lb. drymatter/A from a spring-sown barrel medic (129).

Reduce soil erosion. Medics can survive in sum-mer drought-prone areas where few other culti-vated forage legumes would, thanks to theirhard-seeded tendency and drought tolerance.Low, dense vegetation breaks raindrop impactwhile roots may penetrate 5 feet deep to hold soilin place.

Tolerate regular mowing. Medics can begrazed or mowed at intervals with no ill effects.They should be mowed regularly to a height of 3to 5 inches during the growing season for bestseed set and weed suppression. To increase thesoil seed bank, rest medic from blooming to seed

maturation, then resume clipping or grazing (227, 351, 357).

Provide good grazing. Green plants, dry plantsand burs of bur medic provide good forage, butsolid stands can cause bloat in cattle (351). 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 (217).

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 (228).Scarified seed willachieve 95 percent germination, and 10-year old

STANFORD, Mon. — Jess Alger can count on13 inches of rainfall or less on his centralMontana farm, occasional hail damage, killingfrosts after June 10 now and then, too fewsolar units to raise safflower or millet, somebone-chilling winters without snow cover—and George.That’s GEORGE black medic.

Tests from 1997 showed he got 87 lb.N/Aand 4.3 percent organic matter in a clay loamfield.He initially seeded the medic on 10-inchrow spacings with barley in 1990 at 10 lb./A,his standard rate and seeding method.Hegrazed the medic early in the second year, thenlet it go to seed. In Year 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 matureto 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 in ‘97 with side-by-sidefields of spring wheat. One followed a ’96

spring wheat crop, the other he planted into asix-year-old stand of GEORGE medic.After a yearof canola and a green fallow year of just self-seeded medic, Alger added to the seed bankwith a no-till planting of GEORGE with a nursecrop of Austrian winter peas in ’96.

The ’97 medic/wheat interplant yielded 29 bushels per acre—six bushels less than theother field. But the interplanted grain tested at 15 percent protein, a full percentage pointhigher. Those are high yields for Alger’s area,partly due to timely summer rain.“The yielddrop with medic was mostly a weed problemwith Persian darnel,”Alger explains. He’ll grazethe field closely in ’98 to make sure thedarnel, an annual, doesn’t go to seed.

To plant winter wheat into the seven-year-old medic sward in fall ’97, he used threepasses with a chisel plow and sweeps to kill and partially incorporate the legume. Heplanted wheat with a conventional planter inearly October. He hopes someday to use a no-till planter so he can leave most of themedic in place, bury less seed and allowGEORGE to rest more securely in his field.

Jess Counts on GEORGE for N and Organic Matter


raw seed may still be 50 percent viable (351). Burmedic seed in the intact bur remains viable for alonger time than hulled seed (91).

Their status as a resilient,reseeding forage makesmedics the basis for the “ley system” developed indry areas of Australia. Medics or subterraneanclover pastured for several years on Australian dry-lands help to store moisture and build up soil pro-ductivity for a year of small grain production before

being returned to pasture. This use requires live-stock for maximum economic benefit. GEORGE

black medic is prostrate,allowing other grasses andforbs to become the overstory for grazing.It is well-suited to cold winter areas of Hardiness Zone 4,where it can stay green much of the winter (3).

Quick starting. Black medic can germinate with-in three days of planting (228). About 45 days

While annual medics, in general, are hardseeded, they usually cannot tolerate wintersnorth of the Gulf South. Southern spottedbur medic (Medicago arabica) showspromise as a winter legume that can reseedfor several years from a single seed crop inHardiness Zone 7 of the Southeast.

Once as widely grown as hairy vetch in themid-South region of the U.S., bur medicpersists in non-cropland areas because it iswell adapted to the region (265, 266). A localaccession collected in northern Mississippiexhibits better cold hardiness and insectresistance than commercially available(Australian) annual medics.

In a replicated cold-hardiness trial spanningseveral states, spotted bur medic flowered inmid-March, about two weeks after SERENA,CIRCLE VALLEY, or SANTIAGO burclover, but twoweeks before TIBBEE crimson clover.The burmedic flowered over a longer period thancrimson, matured seed slightly sooner thanTIBBEE but generally did not produce as muchbiomass.

The big advantage of spotted bur medicover 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. 158) reseeded as well as spotted burclover (79). The burmedic cultivar CIRCLE VALLEY successfully

Southern Spotted Bur Medic Offers Reseeding Persistencereseeded in a Louisiana no-till cotton field for more than 10 years without specialmanagement to maintain it (77).

Research in the Southeast showed that ifSouthern spotted bur 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 incooperation with the USDA-Natural ResourcesConservation Service’s Jamie Whitten PlantMaterials Center, Coffeeville, Miss., for possible accelerated release to seed growers as a “source-identified”cover crop. As of late1997, there were no commercial seed sourcesfor Southern spotted bur medic seed.

Insect pests such as clover leaf weevil(Hypera punctata Fabricius) and the alfalfa weevil (Hypera postica Gyllenhal)preferentially attack medics over other winter legume cover crops in the Southeast,and could 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 to ensure a reseeding crop for years to come.

MEDICS 123

after mid-April planting in southern Illinois, twoannual medics were 20 inches tall and blooming.In the upper Midwest, snail and bur medicsachieve peak biomass about 60 days after planti-ng. An early August seeding of the annuals insouthern Illinois germinated well, stopped grow-ing during a hot spell, then restarted.Growth wassimilar to the spring-planted plots by Sept. 29when frost hit.The plants stayed green until thetemperature dipped to the upper teens (157).

Widely acclimated. Species and cultivars varyby up to seven weeks in their estimated length oftime to flowering. Be sure to select a species to fit your 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 (316).

Medics are widely adapted to soils that are rea-sonably fertile, but not distinctly acid or alkaline.Excessive field moisture early in the season cansignificantly reduce medic stands (308). Acid-tol-erant rhizobial strains may help some cool-seasonmedics, especially barrel medic, to grow on sitesthat otherwise would be inhospitable (351).

To reduce economic risk in fields where you’venever 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 (351).

Establishment options vary depending onclimate and crop system:

• Early spring—clear seed. Drill 1/4 to 1/2 inchdeep (using a double-disk or hoe-type drill) into afirm seed bed as you would for alfalfa. Rolling isrecommended before or after seeding to improveseed-soil contact and moisture in the seed zone.Seeding rate is 8 to 10 lb./A for black medic,12 to20 lb./A for larger-seeded (snail, gamma and bur)annual medics. In the arid Northern Plains, fall

germination and winter survival are dependable,although spring planting also 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 bur medic wassuccessfully established in no-till corn three to sixweeks after corn planting, but biomass and weedsuppression were negligible during a two-yeartrial in Michigan. Medic seed was broadcast, thenlightly incorporated as dicamba herbicide wassprayed over the corn to control weeds. Becauseof variable and generally disappointing resultsthroughout the upper Midwest, current medicspecies and cultivars are not recommended forunderseeding in corn (308).

Where medic and corn work together, such asCalifornia, maximize medic survival during thecorn canopy period by seeding early (when corn

BLACK MEDIC (Medicago lupulina)

Elay

ne

Sear

s


is eight to 16 inches tall) and heavy (15 to 20lb./A) to build up medic root reserves (31, 351).

• After wheat harvest. MOGUL barrel medicseeded after wheat harvest produced 119 lb. N/Ain southern Michigan, more than double the Nproduction of red clover seeded at the same time(308). Planted even at mid-season in Montana,snail medic establishes well, smothers weeds,builds up N, then winterkills for a soil-holdingorganic mulch.

• Autumn seeding.Where winters are rainy inCalifornia, medics are planted in October as win-ter annuals (358). Plant about the same time ascrimson clover in the Southeast, Zones 7 and 8.

KillingMedics are easy to control by light tillage orherbicides. They reseed up to three times persummer,dying back naturally each time.Medics inthe vegetative 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. Inthis system, established,self-reseeding black medicplowed down as greenmanure in alternate yearsimproved spring wheatyield by about 50 percentcompared to fallow (313).

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 the medic,or the legume canbe incorporated.

A well-established black medic stand canreduce costs compared with annual crops bycoming back for many years. However, withoutthe livestock grazing benefit to supply additionalutilization, water-efficient legumes such as lentilsand Austrian winter peas will probably be more

effective N sources. Further, the long-lived seedbank that black medic establishes may be unde-sirable for some cash crop rotations in areas ofhigher rainfall (316).

Use of medics in the upper Midwest is still inthe exploratory stage. In a series of trials in Ohio,Michigan, Wisconsin and Minnesota, medic didnot provide enough weed control or N to justifyits use under current cash grain prices, evenwhen premiums for pesticide-free corn wereevaluated (308). One Michigan farmer’s situationis fairly typical. He established annual medic at10 lb./A when his ridge-tilled corn was aboutknee-high. The legume germinated, but didn’tgrow well or provide weed suppression untilafter corn dry-down in mid-September. Themedic put on about 10 inches of growth beforewinterkilling, enough for effective winter ero-sion protection (157).

Soybeans offer a better economic window formedics to work. The expected yield loss is rela-tively smaller (6 bu./A) and higher pesticide-freepremiums could make the system profitable,evenwith lower yield. In 1995, an economic analysisshowed that a premium of 72 cents per bushelover a base price of $6.50 would have mademedic a profitable weed-control option, without

counting its soil-buildingvalue (308).

Black medic and twoannual medics produced50 to 150 lb. N/A wheninterplanted with standardand semi-dwarf barley in a

Minnesota trial.Annual MOGUL produced the mostbiomass by fall, but also reduced barley yields.GEORGE was the least competitive and fixed 55 to 120 lb. N/A. The taller barley was more competitive, indicating that taller smallgrain cultivars should be used to favor grain pro-duction over medic stand development (231).

Midwestern farmers can overseed annualmedic 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 a

Medics earn a place in drylandrotations because they provideN while conserving moisture.

MEDICS 125

second cutting. Regrowth comes from lateralstems, so don’t clip or graze lower than 4 or 5inches if you want regrowth. To avoid bloat,manage as you would alfalfa (157).

Annual medics can achieve their full potentialwhen planted after a short-season spring cropsuch as processing peas or lettuce. Wisconsintests at six locations showed medic produced anaverage of 2. 2 T/A when sown in the late June orearly July (327). Early planting in this windowwith a late frost could give both forage and N-bearing residue,protecting soil and adding springfertility. Take steps to reduce weed pressure insolid 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 annual alfalfa. All the coverswere clear (sole-crop) seeded in early May afterpre-plant incorporated herbi-cide treatment, and wereplowed down 90 days later.Harvesting the medics at 60days as forage did not signifi-cantly lessen their greenmanure value (308).

In the mid-Atlantic at the USDA Beltsville, Md.,site, medics have been hard to establish by over-seeding at vegetable planting or at final cultiva-tion of sweet corn (338).

Pest ManagementUnder water logged conditions for which they areill-suited, annual medics are susceptible to dis-eases like Rhizoctonia, Phytophthora andFusarium (217).

Bur medic harbors abundant lygus bugs inspring. It also appears to be particularly prone tooutbreaks of the two-spotted spider mite, a pestfound in many West Coast orchards (351).

Most medics tolerate low doses of the herbi-cide 2-4,D-amine and glysophate.They are some-what resistant to 2-4,DB (351). Other herbicidescompatible with medics include EPTC, bro-moxynil before medic emergence and bentazonand imidazolinone on medic seeded with imida-zolinone-resistant corn (217). Glysophate, para-

quat, 2,4-D and dicamba kill medic effectively(25). One report says bur medic is very sensitiveto 2,4-D.

Pods and viable seeds develop without pollina-tors because most annual medics have no floralnectaries (91).

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 1 T dry mat-ter and 60 lb. N/A (308).

Medics can establish and survive better thansubterranean clover in times of low rainfall, andare more competitive with grasses. A short periodof moisture will allow medic to germinate and

send down its fast-growingtaproot, while subcloverneeds more consistent mois-ture for its shallower, slowergrowing roots (351). Medicsare more susceptible thansubclover to seed production

loss from closely mowing densely planted erectstalks. Bur and barrel medics are not as effectiveas subclover at absorbing phosphorus (351).

Medics may survive where true clovers(Trifolium spp.) fail due to droughty conditions(351) if there is at least 12 in.of rain per year (234).

Medics grow well in mixtures with grasses andclovers, but don’t perform well with red clover(351,211).Once established,black medic handlesfrost better than crimson or red clover.

GEORGE grows more slowly than yellow blos-som sweetclover in spring of the second year, butit starts flowering earlier. It uses less water in the2- to 4-foot depth than sweetclover, soybeans orhairy vetch seeded at the same time (295).

SEED

Annual Medic Cultivars. Species and cultivarsof annual medic vary significantly in their dry mat-ter production, crude protein concentration and

With abundant moisture,medics can produce morethan 200 lb. N/A.


total N. Check with local or regional foragespecialists for cultivar recommendations

Bur medic (also called burclover) cultivars arethe best known of the annual medics. Theybranch profusely at the base, and send out pros-trate stems that grow more erect in dense stands(351). They grow quickly in response to fallCalifornia rains and fix from 55 to 90 lb.N/A,near-ly as much as true clovers (236, 351). Most standsare volunteer and can be encouraged by propergrazing, cultivation or fertilization.

Selected cultivars include SERENA (an earlybloomer), and CIRCLE VALLEY, both of which havefair tolerance to Egyptian alfalfa weevil (357).SANTIAGO blooms later than SERENA. Early burmedics flower in about 62 days in California,rang-ing up to 96 days for mid-season cultivars (351).

Naturalized and imported bur medic provedthe best type of burclover for self-reseeding covercrops in several years of trials runfrom northern California intoMexico in the 1990s.While someof the naturalized strains havebeen self-reseeding for 30 years insome orchards, Extension special-ists say the commercial cultivarsmay be preferable because they are widely avail-able and better documented (58).

Established bur medic tolerates shade as a com-mon volunteer in the understories of Californiawalnut orchards, which are heavily shaded fromApril through November. However, in Michigantrials over several years, SANTIAGO (a bur medicwith no spines on its burs) failed to establish sat-isfactorily when it was overseeded into corn andsoybeans at layby. Researchers suspect the cropcanopy shaded the medic too soon after planting,and that earlier overseeding may have allowed themedic to establish (134).

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 forHANNAFORD to 260,000 for SEPHI (351). A leadingnew cultivar, SEPHI, flowers about a week earlier

than JEMALONG,commonly used in California (200,351).SELPHI,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(308).MOGUL barrel medic grew the most biomassin a barley intercrop,compared with SANTIAGO burmedic and GEORGE black medic in a four-siteMinnesota trial. It frequently reduced barleyyields, particularly those of a semi-dwarf barleyvariety, but increased weed suppression and Nand biomass production (231).

In a Michigan test of foragelegumes for emergency forageuse, MOGUL barrel medic pro-duced 1.5 T dry matter/A com-pared to about 1 T/A for SAVA snailmedic and SANTIAGO bur medic(M. polymorpha). Nitrogen pro-

duction was 66 lb./A for MOGUL,46 for SAVA and 22for SANTIAGO.The seeding rate for SAVA medic is 29lb./A,more than twice the 13 lb./A recommendedfor clear seedings of MOGUL and SANTIAGO (308).

In a California pasture comparison of threeannual 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 better under permanent pasture than under any rota-tional system involving tillage (68, 351).

Seed sources. Widely available in California;nationally through Kamprath, Peaceful Valley,Timeless and Wolf River. See Seed Suppliers(p. 166).

Medics are easy tokill with light tillageor most herbicides.

RED CLOVER 127

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 earlysummer. Full-season, over-wintered red clover can produce 2 to 3 T dry matter/A and fix nitro-gen at 70 to 150 lb. /A.

Two years of testing in Wisconsin showed thatconventionally planted corn following red cloveryielded the same as corn supplied with 160 lb.N/A, with less risk of post-harvest N leaching.Further, monitoring of the corn and the soil

showed that 50 percent of the cover crop N wasreleased in the first month after incorporation,corresponding well with corn’s fertility demand.Post-harvest soil N levels in the clover plots werethe same or less than the fertilized plots, andabout the same as unfertilized plots (329).

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 corngrows well. It does best in cool conditions.

In southern Canada and the northern U.S., andin the higher elevations of the Southeast andWest, red clover grows as a biennial or short-livedperennial. At lower elevations in the Southeast, itgrows as a winter annual, and at lower elevationsin the West and Canada, it grows under irrigationas a biennial (91).It grows in any loam or clay soil,responding best to well-drained, fertile soils.

Many economic uses. Red clover has been apopular,multi-use crop since European immigrantfarmers brought it to North America in the 1500s.It remains an important crop thanks to its greater

RED CLOVERTrifolium pratense

Also called: medium red clover(multi-cut, early blooming, Juneclover); mammoth clover (single-cut, 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, corn, soy-beans, vegetables, grass forages

See charts, p. 47 to 53, for rankingsand management summary.

spring seeded biennial winter annual


adaptability, lower seeding cost and easier estab-lishment than alfalfa. It can produce up to 8,000lb. biomass/A (277).

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 (328). Both had gross margins ofabout $166/A, with fertilizer nitrogen figured at$0.12/lb. as anhydrous ammonia.

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.The companion seedings yieldednearly twice as much estimated fer-tilizer replacement value as the seq-uential seedings.The work showedthat red clover holds great potentialto reduce fertilizer N use for corngrown in rotation (329).

Red clover sown as a companionwith spring oats outperformed the other leg-umes, which suffered from insect damage,mechanical damage during oat harvest and slowsubsequent regrowth. The short season provedinadequate for sequentially seeded legumes withthe exception of hairy vetch,which was nearly asprofitable as the red clover.

The role of red clover’s N contribution in therotation grew more significant in 1996 when Nprices had risen 83 percent, even though cloverseed price had also risen 40 percent from the orig-inal 1989 calculations. A corn>soybean>wheat/red clover sequence had a gross margin of $17/Amore than continuous corn and nearly $10/A morethan an oats>corn rotation in 1996 (326).

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 clover inpecan orchard recommendations from OklahomaState University in 1996. Red clover attracts more

beneficials than white clover,which features high-er N fixation and greater flood tolerance than redclover (209).

Two TypesTwo distinct types of red clover have evolvedfrom the same species. Be sure you plant a culti-var with the regrowth option if you plan to makemore than one green manure cutting, or to main-tain the stand to prepare for a late-summer veg-etable planting.

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 benefitand flexible cropping options fromthe planting (allowing it to over-winter as a soil-protecting mulch),you can use it for hay, grazing orseed throughout the second sea-son. Seed may be priced the sameas single-cut types (240), or it can

be up to 25 percent more than single-cut. SeeChart 3B: Planting (p. 51).

Mammoth red clover produces as much Npound for pound and will produce significant bio-mass in a single first cutting,but does not produceas much biomass overall as medium red’s multiplecuttings over time. Use this “single-cut” red cloverwhere a field will be all-clover just during theseeding year. Slow-growing mammoth doesn’tbloom the establishment year and regrows quiteslowly after cutting, but can provide good bio-mass by the end of even one growing season.

A single cutting of mammoth will give slightlymore biomass—at a slightly lower cost—than asingle cutting of medium red. Where multiplecuttings or groundcover are needed in the secondseason, medium red clover’s higher seed cost iseasily justified (153).

Some types of mammoth do better overseededinto wheat than into oats. ALTASWEDE (Canadian)mammoth is not as shade tolerant as MICHIGAN

mammoth, but works well when seeded withoats. MICHIGAN mammoth shows the best vigorwhen frostseeded into wheat, but is not asproductive as medium red (183).

Red clover canyield 2 to 3 tons of dry matter and70 to 150 lb. N/A

RED CLOVER 129

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 at 8 to 12 lb./A with spring-sown grains, usingauxiliary or “grass seed”drill boxes.Cut back smallgrain seeding rates up to 50 percent from purestand rates, if clover for forage is your main goal.Wisconsin researchers who have worked for sev-eral years to optimize returns from red clover/oats interseedings say planting oats at 3 to 4 bu./Agives good stands of clover without sacrificinggrain yield (326).

Red clover’s tolerance of shade and its ability togerminate down to 41 F give it a remarkable rangeof establishment niches.

It can be overseeded at 10 to 18 lb./A into:• Dormant winter grains before ground

thaws. This “frostseeding”method relies on move-ment of the freeze-thaw cycle to work seed intosufficient seed-soil contact for germination.Michigan farmers frostseed red clover at 6 to 8lb./A (240). If the soil is level and firm, you canbroadcast seed over snow cover on level terrain.You can seed the clover with urea if fertilizerapplication is uniform (183). Use just enough N fertilizer to support proven small-grain yields,because excess N application will hinder cloverestablishment. To reduce small grain competitionwith clover in early spring, graze or clip the smallgrain in early spring just before the stems begin togrow (91). Hoof impact from grazing also helpsensure seed-to-soil contact.

• Summer annuals such as oats, barley, speltor spring wheat before grain emergence.

• Corn at layby. Wait until corn is 10 to 12inches tall, at the V-4 to V-6 growth stage. Cloversown earlier in favorable cooler conditions withmore light may compete too much for water.Later, the clover will grow more slowly and notadd substantial biomass until after corn harvestlets light enter (153). Dairy producers oftenbroadcast red clover after corn silage harvest.

• After wheat harvest. Red clover logged afertilizer 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 (104).

• Soybeans at leaf-yellowing. Sowing theclover seed with annual or perennial ryegrass as anurse crop keeps the soil from drying out untilthe clover becomes established (153).

Whenever possible, lightly incorporate cloverseed with a harrow. Wait about six weeks toestablish a red clover stand in soil treated withpre-emergent herbicides such as atrazine. Checkherbicide labels for rotational crop plant-backintervals, and remember that cool temperaturewill slow herbicide breakdown (240).

KillingFor peak N contribution, kill red clover at aboutmid-bloom in spring of its second season. If youcan’t wait that long, you can kill it earlier to plantfield corn or early vegetables. If you want to har-vest the first cutting for hay, compost or mulch,kill the regrowth in late summer as green manurefor fall vegetables (153). If avoiding escapes orclover regrowth is most important, terminate assoon as soil conditions allow. Actively growing red clover can be difficult to kill mechanically(106), but light fall chisel plowing followed by asecond such treatment has worked well in sandyloam Michigan soils (240).

To kill clover mechanically in spring, you cantill,chop or mow it any time after blooming starts.You can shallow plow, or use a chisel plow about2 to 3 inches deep. Use overlapping shovels, suchas 16-inch sweeps on shanks spaced 12 inches oncenter. Chop (using a rolling stalk chopper), flailor sicklebar mow about seven to 10 days ahead ofno-till planting,or use herbicides such as atrazine,cyanazine, paraquat or glyphosate (25), whichworks best in fall (240).

A summer mowing can make it easier to kill redclover 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 four


weeks. If not mechanically killing, spray with 2quarts of glyphosate and a quart of 2,4-D ester peracre. The daytime high air temperature should beabove 60 F (so that the plants are actively grow-ing). When soil temperature drops below 50 F,biological decomposition slows to the point thatmineralization of N from the clover roots and top-growth nearly stops (183).

Field EvaluationIn Michigan, plant counts are used to estimateroughly how much N a clover stand will con-tribute to the immediately following crop. Theformula is 30 + 0.30 x % stand,where 100 percentstand is five to six plants per square foot in thesecond year of growth. So a field where yourcounts showed an average of six plants per squarefoot would contribute about 60 lb. N/A (30 +[0.30 x 100] 30 = 60). With four plants per squarefoot, percent stand is 4/6 or 66 percent, so the Ncontribution is 50 lb./A (30 + [.30 x 66] 20).

The Michigan field calculation reflects the con-ventional rule of thumb that about half of the totalN fixed by a legume will mineralize during the fol-lowing growing season and be available to thatseason’s crop (183). However,Wisconsin research

shows release may be faster. There, red clover and hairy vetch released 70 to 75 percent of theirN in the first season (329).

RotationsRotation niches for red clover are usually betweentwo non-leguminous crops. Spring seeding withoats or frostseeding into a wheat crop are com-mon options. The intersowing allows economicuse of the land while the clover is developing.This grain/red clover combination often followscorn, but also can follow rice, sugar beets, tobac-co or potatoes in two-year rotations. For three-year rotations including two full years of redclover, the clover can be incorporated or surface-applied (clipped and left on the field) for greenmanure, cut for mulch or harvested for hay (91).

Red clover in a corn>soybean>wheat/redclover rotation in a reduced-input system out-per-formed continuous corn by $53 per acre in a four-year Wisconsin study. The legume cover cropsystem used no commercial fertilizer, no insecti-cides and herbicides on only two occasions—once to-spot spray Canada thistles and once as arescue treatment for soybeans.Rotary hoeing andcultivating provided weed control.

Gross margins were $195 for the corn>soy-beans>wheat/red clover and $151 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$209, using standard inputs (218, 326).

Pest ManagementIf poor establishment or winterkill leads to weedgrowth that can’t be suppressed with clipping orgrazing, evaluate whether your anticipated covercrop benefits warrant weed control. MCPA islabeled for broadleaf weed control in winterannuals with clover seedings, but care must betaken to avoid seedling injury (183).

Never plant dry beans or soybeans after cloverunless the cover has been thoroughly incorporat-ed by plowing. Limited herbicide options may beunable to control clover escapes that survive inthe bean crop (183).

Root rots and foliar diseases typically kill com-mon medium red clover in its second year,making

RED CLOVER (Trifolium pratense)

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RED CLOVER 131

it 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 byvolunteer clover plants (295).

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 itsprime feeding value at five to 15days after first bloom. Underideal condition, medium redclover can be cut four times,mammoth only once. Maximumcutting of medium one year willcome at the expense of second-year yield and stand longevity(326).Red clover and red clover/grass mixtures make good silage if wilted slightlybefore ensiling or if other preservative techniquesare used (91).

If an emergency forage cut is needed,harvest redclover in early summer, then broadcast and lightlyincorporate millet seed with a tine harrow or disk.Millet is a heat-loving grass used as a cover and for-age in warm-soil areas of Zone 6 and warmer (seeUp-and-Coming Cover Crops, p.158).

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 (277).

Red clover and sweetclover both perform best onwell-drained soils, but will tolerate poorly drainedsoils. Alsike thrives in wet soils (306).

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 (220).

For early fall plowdown, alsike clover (with aseeding cost of about $9/A) may be a cheaper

N source than mammoth at$15.50/A, assuming similar Nyields (253).

Red clover and alfalfa showedmulti-year benefits to succeed-ing corn crops, justifying a cred-it of 90 lb. N/A the first year forred clover (153) and 50 lb. N/Athe second year (326). The thirdlegume in the trial, birdsfoot

trefoil (Lotus corniculatus), was the only one ofthe three that had enough third-year N contribu-tion to warrant a credit of 25 lb.N/A (113).

SEED

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(65). CHEROKEE is more suited to the Coastal Plainand lower South, and has superior resistance torootknot nematode (277).

Seed sources. Widely available. Companiesspecializing in forage crops have several cultivars.

Few legumes are aswidely adapted as redclover, which can beused as green manure,forage or seed crop.


Subterranean clovers offer a range of low-growing, self-reseeding legumes with high Ncontribution, excellent weed suppression

and strong persistence in orchards and pastures.Fall-planted subclovers thrive in Mediterraneanconditions of mild, moist winters and dry sum-mers on soils of low to moderate fertility, andfrom moderately acidic to slightly alkaline pH.

Subclover mixtures are used on thousands ofacres of California almond orchards,where farmerscontinue to evaluate some 50 cultivars for opti-mum combinations. Subclover holds promise inthe coastal mid-Atlantic and Southeast (HardinessZone 7 and warmer) on sandy loam to clay soils asa killed or living mulch for summer or fall crops.Most cultivars require at least 12 inches of rain per year. A summer dry period limits vegetativegrowth, but increases hard seed tendency thatleads to self-reseeding for fall reestablishment.

Subclovers generally grow close to the ground,piling up their biomass in a compact layer. AMississippi test showed that subclover stems wereabout 6, 10 and 17 inches long when the canopywas 5,7 and 9 inches tall, respectively (79).

Diversity of Types, CultivarsSelect among the many subclover options culti-vars that fit your climate and your cover cropgoals. Identify your need for biomass (for mulchor green manure), time of natural dying to fit yourspring-planting schedule and prominence of seedset for a persistent stand.

Subclovers comprise three Trifolium species:• T. subterraneum. The most common cultivars

that thrive in acid to neutral soils and aMediterranean climate

• T. yanninicum. Cultivars best adapted towater-logged soils

• T. brachycalcycinum. Cultivars adapted toalkaline soils and milder wintersPrimary differences between these species are

their moisture requirements, seed production anddays to maturity (15). 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

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 andsubclovers


cool season annualspring seeded

reseeding cool season annualfall seeded

SUBTERRANEAN CLOVERS 133

Subclover cultivars often are described by theirmoisture preference and days to maturity, whichare closely linked traits. The maturity estimates are set for continuous growing days, and will begreatly lengthened for fall-planted subclovers inthe East and Southeast, where winter weatherdelays flowering for two to three months.

• Short season subclovers tend to set seedquickly. Cultivars such as DALKEITH (an improvedversion of DALIAK) and NUNGARIN need only 8 to 10inches of rainfall and set seed about 85 days afterplanting. Early subclovers tend to be less winterhardy (77).

• Intermediate types such as TRIKKALA and thenew,more competitive GOSSE thrive with 14 to 20inches of rain and set matureseed in about 100 days.

• Long-season cultivars suchas KARRIDALE and NANGEELA per-form best with 18 to 26 inchesof rainfall, setting seed in about130 days. MT. BARKER was a long-time research standard that isnow surpassed by KARRIDALE for forage produc-tion, hardseed percentage, re-establishment po-tential and grazing. KARRIDALE is more prostrate,and is favored for cover crop use (345).

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-controllingmulch.

Subclover mixtures help West Coast orchardistsachieve season-long weed management. In CoastalCalifornia, fast-growing TRIKKALA, a mid-season cul-tivar with a moderate moisture requirement,jumpsout first to suppress weeds and produces abouttwice as much winter growth during January andFebruary as the other subclovers. It dies back natu-rally as KOALA, (tall) and KARRIDALE (short) come onstrong in March and April. The three cultivarscomplement each other spatially and temporallyfor high solar efficiency,similar to the interplantingof peas, purple vetch, bell beans and oats in

California vegetable fields where a high-residue,high-N cover is desired (345).

In legume test plots along the Maryland shore,subclover mulch controlled weeds better thanconventional herbicide treatments. The only weed to penetrate the subclover was a fall infes-tation of yellow nutsedge.The cover crop regrewin fall from hard seed in the second and thirdyears of the experiment (19).

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 into

disked and fertilized soil with-out a cover crop in three out offour years. The fertilized fieldshad received 54 lb. N/A (192).

Versatile mulch. Subcloverprovides two opportunities foruse as a mulch in vegetable sys-

tems. In spring,you can no-till early planted cropsafter subclover has been mechanically or chemi-cally killed, or plant later, after subclover has setseed and dried down naturally (19). In fall, youcan manage new growth from self reseeding toprovide a green living mulch for cold-weathercrops such as broccoli and cauliflower (165).

Conventionally tilled corn without a cover cropin a New Jersey test leached up to 150 lb. N/Aover winter while living subclover prevented Nloss (99). 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 (189).

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 (323).

Subclovers thrive inMediterranean climatesof mild, moist wintersand dry summers.


Great grazing. Subclovers are highly palatableand relished by all livestock (91). Seeded withperennial ryegrass,tall fescue or orchardgrass,sub-clovers add feed value as they improve produc-tivity 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 (249).

Insect pest protection. In the Netherlands, sub-clover and white clover in cabbage suppressedpest insect egg laying and larval populationsenough to improve cabbage quality and profitcompared with monocropped control plots.Eliminating pesticide costs offset the reducedweight of the cabbages in the undersown plots.Primary pests were Mamestra brassicae,Brevicoryne brassicae and Delia brassicae.Undersowing leeks with subclover in theNetherlands greatly reduced thrips that cannot becontrolled by labeled insecticides, and slightlyreduced leek rust,a disease that is difficult to con-trol. While leek quality improved, the quantity ofleeks produced was reduced considerably (344).

When tarnished plant bug (Lygus lineolaris) isa 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 low

levels, and nine other subclover cultivars hadlower levels than the crimson (38).

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 the covers made a significant difference in thepredator level, they did not make a significantdifference in control of the target pest, fall army-worm (Spodoptera frugiperda) (38).

Erosion fighter. Subclover’s soil-hugging, dense,matted canopy is excellent for holding soil (77).

Disease-free. No major diseases restrict sub-clover acreage in the U.S. (15).

MANAGEMENT

EstablishmentSubclovers grow best when they are planted inlate summer or early autumn and grow untilearly winter. They go dormant over winter andresume growth in early spring. In late spring,plants flower and seeds mature in a bur at orbelow the soil surface (hence the name subter-ranean clover) as the plant dries up and dies. Adense mulch of dead clover leaves and long peti-oles covers the seeds, which germinate in latesummer to establish the next winter’s stand(98). Their persistence over many seasonsjustifies the investment in seed and carefulestablishment.

In California, sow in September or earlyOctober to get plants well established before coolweather (249). Planting continues throughNovember in the most protected areas (281).

In marginally mild areas, establish with grassesfor 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 livestock

SUBTERRANEAN CLOVER(Trifolium subterraneum)

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trample 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 (91).

Broadcast at 20-30 lb./A in a well-prepared,weed-free seedbed that is firm below a depth of2 inches. Cover seed with a light, trailing harrowor with other light surface tillage to a depth ofless than one-half inch. Add lime if soil is highlyacid—below pH 5.5 (249). Soils low in pH mayrequire supplemental molybdenum for propergrowth, and phosphorus and sulfur may also belimiting nutrients. Only the T. yanninicum culti-vars will tolerate standing water or seepageareas (15, 249).

Subclover often is plantedwith rose clover and crimsonclover in California orchardmixes. Crimson and sub-clover usually dominate, buthard-seeded rose clover per-sists when dry weather knocks out the other two (368).

In the East, central Mississippi plantings arerecommended Sept. 1 to Oct. 15, although earlierplantings produce the earliest foliage in spring(91). In coastal Maryland where MT.BARKER plantswere tallest and most lush, winterkill (causedwhen the temperature dropped to 15 F orbelow) 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 (19) andSoutheast (77). This is about double the usualrecommended rate for pastures in the warmersoils of the Southeast.

Small plants of ground-hugging subclover ben-efit more from heat radiating from the soil thanlarger plants, but are more vulnerable duringtimes of freezing and thawing.Where frost heav-ing is expected, earlier planting and well-estab-lished plants usually survive better than smallerones (77).

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 (77).

In northern Mississippi, subclover was the leastcontrolled of four legumes in a mechanical killtest. The cover crops were subjected to beingrolled with coulters spaced 4 inches apart whenthe plants had at least 10 inches of prostrategrowth. While hairy vetch and crimson cloverwere 80 to 100 percent controlled, berseemcontrol was 53 percent and subclover wascontrolled only 26 to 61 percent (79).

Researchers in Ohio had no trouble killing post-bloom subclover with a custom-built under-cutter.The specialized tool is made to slice 1 to 2

inches below the surface ofraised beds.The undercutterconsisted of two blades that are mounted on uprightstandards on either side ofthe bed and slant backwardat 45 degrees toward the

center of the bed.A mounted rolling harrow wasattached to lay the cover crop flat on the surfaceafter being cut (70). The tool, which continues tobe modified, severs stalks from roots while above-ground residue is undamaged, greatly slowingresidue decomposition (69).

Glysophate and dicamba (25) materials workbetter for controlling subclover than do paraquat(77) and 2,4-D (186). Subclover tolerance to her-bicides varies with cultivar and growth stage.Generally, subclover is easier to kill after it has setsome seed (78, 130).

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 (249).Grazing or mowing in late springor early summer helps control weeds that growthrough the mulch (234).

Subclover mixes help keepweeds in check all seasonlong in West Coast orchards.


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 (15). Seed produc-tion in Oregon was best following grazing fromjust prior to the start of flowering until the timeof early bur fill (15). Subclover flowers are incon-spicuous and will go unnoticed without careful,eye-to-the-ground inspection (77).

After plants mature, livestock will eagerly eatseed heads (91). 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.

Some subclover seed (primarily MT. BARKER) isproduced in Oregon and sold locally for forageuse.Most commercial subclover seed is producedin Australia. Subclover cultivars were developedthere for use in “ley” cropping. In this system,sheep or other livestock graze the legume forseveral years. Then the land is cropped brieflybefore being pastured again as the hard seeds ofsubclover re-establish a stand.

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 (75). 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 (43).

The degree to which a cover crop mulchhinders vegetable seedlings is crop specific. Plant-toxic compounds from subclover mulch suppres-sed lettuce,broccoli and tomato seedlings for eightweeks, but not as severely or as long as did com-pounds from ryegrass (Lolium rigidum cv.

WIMMERA) mulch. An alfalfa mulch showed no suchallelopathic effect in an Australian study (323).

Guard against moisture competition fromsubclover at planting. Without irrigation toensure crop seeds will have enough soil mois-ture to germinate in a dry year, be sure that thesubclover is killed seven to 14 days prior toplanting to allow rainfall to replenish soilmoisture naturally (19).

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, butdisappeared seven to 13 days after legumeresidues were removed (75).

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 than redclover and berseem clover, which leached only 2to 4 lb. N/A in a Swedish test (181).

Pest ManagementSubclovers showed little resistance to root-knotnematodes in Florida tests on 134 subclover linesin three years of testing the most promisingvarieties (186).

Lygus species, important pests of field, rowand 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 (38).

Most cultivars imported to the U.S. are low in estrogen, which is present in sufficient levelsin some Australian cultivars to reduce fertility in ewes, but not in goats or cattle. Confirm estro-gen status of a cultivar if you plan to graze sheepon it (249).


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 and 24 lb. N/A, respectively (29).

Plant breeder Gerald Ray Smith of Texas A&MUniversity worked with several subclovers in east-ern Texas. While the subclovers grew well the first year,he concluded that those cultivars need aprolonged dry period at maturity to live up totheir reseeding performance in Australia andCalifornia. Surface moisture at seed set reducesseed hardening and increases seed decay. Mid-summer rains cause premature germination thatrobs the subclover seed bank, especially in pas-tures where grasses tend to create moist soil(318). Most summer-germinating plants die whendry 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 (100, 101).To facilitate reseeding or to seed into pastures,thegrasses must be mowed back or grazed quiteshort for the subclover to establish (77).

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 (345).

Rice N-source. In Louisiana trials, subcloverregrew well in fall when allowed to set seedbefore spring flooding of rice fields. Compared

with 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 (77). Formerly, some Louisianarice farmers seeded the crop into dry soil then letit develop for 30 days before flooding. Early vari-eties such as DALKEITH 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 (22).

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 contributed up to 370 lb. N/A (99), an N supply requiringcareful management after the subclover dies toprevent leaching.

Control of fall panicum was poor in the firstyear, 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 (99).

Central New Jersey had mild winters duringthese experiments. Early spring thaws triggeredsubclover regrowth followed by plunging tem-peratures that dropped below 15 F. This weak-ened the plants and thinned the stands. Thesurviving plants, which formed dense stands attimes, 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 (165).

Sustainable sweet corn. On Maryland’s EasternShore (one USDA hardiness zone warmer thanNew Jersey), University of Maryland Weed


Specialist Ed Beste reported good reseeding infour consecutive years and no problems withstand loss 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 (19).

Beste believes the sandy loam soil with a sandunderlayer 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 mulch intransplanted vegetable systems.Winterkill reducedthe subclover stand on top of bedded rows oneyear of the comparison, yet surviving plantsbetween the beds produced nearly as muchbiomass per square foot as did hairy vetch (1).

Beste has worked with subclover at hisSalisbury, 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 (19).

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(19).Such a no-chemical/dying mulch/perpetuallyreseeding legume system is the goal of cultivarand system trials in California (346).

Seed production in subclovers normally is trig-gered by increasing day length in spring after theplant experiences decreasing fall day length(346). This explains why spring-planted subcloverin Montana tests produced profuse vegetativegrowth,especially when fall rains began,but failedto set any seed (316). 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 (320).Top reseeding contenders are balansa clover (seeUp-and-Coming Cover Crops, p. 158.) and south-ern spotted bur medic (see Southern Spotted BurMedic Offers Reseeding Persistence, p. 122).

While mid-season subclovers generally pro-duced more dry matter and N than medics fordryland cereal-legume rotations in Montana(314), 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 (316).

CLARE is a cultivar of the subclover subspeciesbrachycalycinum.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 (43).

Subclover,rye and crimson clover provided grassweed 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 treatmentseliminated the need for pre-emergent herbicidesfor economic levels of weed control (373).

Subclover creates a tighter mat of topgrowththan vetch (19) or crimson clover (77).

SEED

Cultivars. See Comparative Notes, above, andDiversity of Types, Cultivars (p. 132).

Seed sources. Adams-Briscoe, Ampac, Budd,Kamprath, Kaufman, Peaceful Valley. See SeedSuppliers (p. 166).

SWEETCLOVERS 139

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 biennialtypes unless otherwise noted.

Sweetclover was the king of green manuresand grazing legumes in the South and later

throughout 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 (365).

A distinguishing sweetclover feature is bracts oftiny 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(370). Tall, stemmy cultivars are better for soilimprovement (91, 302, 351).

Both yellow and white sweetclover have culti-vars bred for low levels of coumarin. This com-

SWEETCLOVERSYellow sweetclover (Melilotusofficinalis) and whitesweetclover (M. alba)

Also called: HUBAM (actually a culti-var of annual white sweetclover)

Type: biennial, summer annual or winter annual legume

Roles: soil builder, fertility source,subsoil aerator, weed suppressor,erosion preventer

Mix with: small grains


biennialspring sown

marginal areabiennialfall sown


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 (M.alba var. annua) is notfrost tolerant,but can produce up to 9,000 lb.drymatter/A over a summer after being oversowninto a grain crop or direct seeded with a springgrain nurse crop. The best-known annual sweet-clover cultivar is HUBAM, a name often used for allannual white sweetclover. While its taproot isshorter and more slender than that of its biennialcousins, it still loosens subsoil compaction.

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 (302).

Research in Saskatchewan during a 34-yearperiod 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 springwheat, could tap the deep P buildup from the

legume 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 (49, 50).

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. Illinoisresearchers reported more 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 (306).

Soil structure builder. Kansas farmer BillGranzow says sweetclover gives his soils higherorganic matter, looser structure and better tilth (126). See Sweetclover: Good Grazing, GreatGreen Manure (p. 142). HUBAM annual sweet-clover also improved soil quality and increasedyield potential in 1996 New York trials (371).

Compaction fighter. Yellow sweetclover has adeterminate 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 (125).

Inexpensive. Establishment costs of about$11/A are one-half to one-fifth that of other majorlegume cover crops.

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

YELLOW SWEETCLOVER (Melilotus officinalis)

Mar

ian

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Sarr

anto

nio

SWEETCLOVERS 141

difficult to establish annual cover crops.The yel-low type is less sensitive to drought and easier toestablish in dry soils than the white type (125).

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(141). 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(91) 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 (116). Use an alfal-fa/sweetclover inoculant.

In temperate areas of theCorn Belt, drill yellow sweet-clover in pure stands at 8 to 15lb./A or broadcast 15 to 20lb./A, using the higher rate indry or loose soils or if notincorporating.

In drier areas such as easternNorth Dakota, trials of seeding rates from 2 to 20lb./A showed that just 4 lb./A,broadcast or drilled,created an adequate sole-crop stand for maximumyield.Recommended rates in North Dakota are 4 to6 lb./A drilled with small grains at small-grain plant-ing, 5 to 8 lb./A broadcast and harrowed (some-times in overseeding sunflowers),and 6 to 10 lb./A.broadcast without incorporating tillage (141).

An excessively dense stand will create spindlystalks 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 subsoilpenetration or snow trapping, go with a lighterseeding 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 scarification to produce an adequate stand may be over-rated,however. The process had no effect on germina-tion in six years of field testing in North Dakota—even when planting 70 percent hard seed still inseed pods (214).

Seed at a depth of 1/4 to 1/2 inch in medium toheavy 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 30pounds 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 planting

sweetclover into a firm seed-bed. If the seedbed is tooloose to allow the drill to reg-ulate seeding depth, run theseed spouts from the grassand legume boxes to dropseed behind the double-diskopener and in front of thepress wheels. Light, shallowharrowing can safely firm the

seedbed and incorporate seed (141).If your press-wheel drill has no legume box or

grass-seed attachment, you can mix the legumeand small grain seed. Reduce competitionbetween the crops by seeding a part of the com-panion crop first, then seed a mix of the cloverseed and the balance of the grain seed at rightangles (141).

Winter-hardy and droughttolerant, this biennial canproduce up to 200 lb. N/Awith good fertility andrainfall.


Bill Granzow taps biennial yellow and whitesweetclovers to enhance soil tilth, controlerosion and prevent subsoil from becomingcompacted. He works with a common varietythat his father originally bought from aneighbor.

Granzow, of Herington, Kan., produces grainand runs cattle in an area midway betweenWichita and Manhattan in the east-central part of the state.

Granzow overseeds sweetclover into winterwheat in December or January at 12 to 15lb./A using a rotary broadcaster mounted onhis pickup. Sometimes he asks the local graincooperative to mix the seed with his ureafertilizer for the wheat. There’s no extracharge for seed application. Granzow alsoplants sweetclover at the same rate withMarch-seeded oats.

Yellow sweetclover has overgrownGranzow’s wheat only when the wheat stand is thin and abnormally heavy rains delayharvest.The minimal problem is even morerare in oats, he says.

He uses yellow sweetclover with thecompanion 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.Second-year options include:• Grazing/green manure. Turn in livestock

when the clover reaches 4 inches tall, letthem graze for several weeks, then diskseveral times before planting grain sorghum.He feeds an anti-bloat medication to keepcattle healthy on the lush legume forage.

• Quick green manure. Disk at least twiceafter it has grown 3 to 4 inches, then plantsorghum.This method contributes about 60

pounds of N to the soil. He knocks backpersistent re-growing sweetclover crowns in the sorghum by adding 2, 4-D or Banvelto the postemerge herbicide mix.

• Green manure/fallow. Disk at-mid to fullbloom, summer fallow then plant wheatagain in fall.This method provides about120 lb. N/A, according to estimates fromKansas State University. Disking or otherlight tillage controls weeds that may emerge with sufficient rainfall.

• 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,he runs the seed through the combine asecond or third time.Despite the heavy growth in the second

year, yellow sweetclover matures and dies back naturally.Two or more passes with his496 International disk with smooth 21-inchblades on 9 inch spacings does an adequatejob to prepare for fall planting.

Granzow sows sorghum followingsweetclover with an 800 International Cyclo-planter with small furrow openers.Anotheroption would be to use a no-till planter afterherbicide desiccation, he says.

He rates fall sweetclover hay from theseeding year as “acceptable forage.”He’s aware that 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,”hesays, adding value to its cover crop benefitsand giving him farming flexiblity.

Sweetclover: Good Grazing, Great Green Manure

SWEETCLOVERS 143

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(116). Where weeds would be controlled bymowing, no-till spring seeding in small grainstubble works well.

Broadcast seeding for pure sweetclover standsworks 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 harvestof 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 exhibitedpoor regrowth after oat harvest in two years of aWisconsin study. To establish a sweetclover cover crop in this way, the researchers foundsweetclover did not fare well in years when thecombine head had to be run low to pick uplodged oats. When oats remained upright (sacri-ficing some straw for a higher cut), sweetclovergrew adequately (330).

You can plow down spring-planted yellowsweetclover 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 latesummer where winters are mild, north throughZone 6. Plant at least six weeks before frost soroots can develop enough to avoid winter heav-ing. See Sweetclover: Good Grazing, Great GreenManure (p. 142).

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 (302). Seeding year clip-ping before Aug. 15 in North Dakota can boostbiomass production by 50 percent, but virtually

no sweetclover is currently clipped in the firstyear (214).

Top growth peaks in late summer as the plant’smain 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 (125).

Sweetclover establishes well when sown withwinter 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 to August in Ohio, records show top-growth increasing tenfold while root productiondecreased by 75 percent (125, 365). All crownbuds initiate growth in spring. If you wantregrowth after cutting, leave plenty of stem budson 6 to 12 inches of stubble. You increase the riskof killing the sweetclover plant by mowing heav-ier stands, at shorter heights, and/or at latergrowth stages, especially after bloom (141).

Before it breaks dormancy, sweetclover canwithstand flooding for about 10 days withoutsignificant stand loss. Once it starts growing,however, flooding will kill the plants (141).

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 (141, 302).Killing sweetclover before bud stage has severalbenefits: 80 percent of the potential N is present;N release is quick because the plant is still quitevegetative with a high N percentage in youngstalks and roots; and moisture loss is halted with-out reducing N contribution. Sweetclover may


regrow from healthy crowns if incorporatedbefore the end of dormancy.For optimum full-sea-son organic matter contribution, mow prior toblossom stage whenever sweetclover reaches 12to 24 inches high before final incorporation ortermination (302). Mowing or grazing at bloomcan kill the plants (125).

In dryland areas, the optimum termination datefor a green manure varies with moisture condi-tions. In a spring wheat>fallow rotation in Saskat-chewan, sweetclover incorporated in mid-June ofa dry year provided 80 percent more N the fol-lowing spring than it did when incorporated inearly July or mid-July—even though it yielded upto a third less biomass at the June date.Mineralization from sweetclover usually peaksabout a year after it is killed.The potential rate ofN release decreases as plants mature and is affect-ed by soil moisture content (112).

In this study, the differences in N release wereconsistent in years of normal precipitation, butwere less pronounced. Little N mineralizationoccurred in the incorporation year. Nitrogenaddition peaked in the following year, and hasbeen shown to continue over seven years fol-lowing yellow sweetclover (112).

In northern spring wheat areas of NorthDakota, yellow sweetclover is usually terminatedin early June just at the onset of bloom, when itreaches 2 to 3 feet tall. This point is a compromisebetween cover crop gain (indry matter and N) and waterconsumption. A quick killfrom tillage or haying is moreexpensive and labor-intensivethan chemical desiccation,but it stops moisture-robbingtranspiration more quickly(116). Herbicides that kill sweetclover include2,4-D, dicamba, glyphosate and paraquat (25),with the latter material offering quicker desicca-tion than glyphosate (82).

Grazing is another way to manage second-yearsweetclover 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 (116).

Pest ManagementSweetclover is a rather poor competitor in itsestablishment year, making it difficult to establishpure sweetclover in a field with significant weedpressure.

Sweetclover residue is said to be allelopathicagainst 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 amajor 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 thecycle, but planting early with a non-competitivenurse crop (flax or small grains) gives sweet-clover plants the best chance to survive weevilforaging, Podoll says. Efforts continue on his farmand other locations to establish a parasitic wasp

from a similar climate inRussia that will help to stabi-lize the weevil population.

Eric and Anne Nordell ofnorth-central Pennsylvaniareport that early spring plow-down of their overwinteredsweetclover gives them fewer

slug and grub problems on spring-planted cropsthan later plowdown. They prefer to have thelegume start a cover>fallow>cover sequence ontheir certified organic farm.They overseed yellowsweetclover into early crops in June, let it over-winter, then plow it down. A slug-fighting barefallow period then precedes August-planted ryeand hairy vetch. The Nordells fit their cash crops around the cover crop rotation that best

During its second season,yellow sweetclover cangrow 8 feet tall while roots penetrate 5 feet deep.

SWEETCLOVERS 145

enhances soil fertility, texture and moisture andsuppresses weeds. See Full-Year Covers TackleTough Weeds (p. 38).

In a three-year Michigan trial of crop rotationsto decrease economic losses to nematodes, ayellow 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(56). Legume-supplied N coupled with an overallnutrient balance and enhanced cation exchangecapacity from the cover crop are thought to beinvolved in suppressing nematode damage (20).

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 retainedresidue of “brown” fallowlessens the erosion and evapo-ration of tillage-intensive “blackfallow,” but “green fallow” offerseven more benefits in terms ofsoil biological life, biodiversity,beneficial insect habitat, possi-ble harvestable crops and alternate forages.

Rapeseed (Brassica campestris) is a summerannual 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 (203).

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 greatly

reduce the erosion potential after oilseed crops,which leave little residue over winter (116).

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.

Sweetclover overseeded into sunflowers at lastcultivation 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 earlierplanting 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 (116).

Even though legume green manures in anotherNorth Dakota study used about 2.8 inches (rain-fall equivalent) more water than fallow,they led toa 1-inch equivalent increase over fallow in soilwater content in the top 3 inches of soil the fol-lowing spring (9).

One green fallow option isplanting yellow sweetcloverwith spring barley or springpeas. This is challenging, how-ever, because barley can beoverly competitive while herbi-cide compatibility is a concernwith the peas.

Fred Kirschenmann of Windsor, N.D., controlsspring 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 (ormillet, if there is less soil moisture). He harvestsbuckwheat, hoping for a 900 lb./A yield, then letsthe clover grow and overwinter. In early summer,when he begins to see yellow blossoms, he disksthe cover, lets it dry,then runs a wide-blade sweepplow just below the surface to cut apart thecrowns. The biomass contribution of the sweet-clover fallow builds up organic matter, he says, incontrast to the black-fallow route of burning uporganic matter to release N. Preventing humusdepletion holds back the dreaded kochia weed.

Sweetclover is the bestproducing warm-seasonforage legume, eventopping alfalfa.


In higher-rainfall temperate areas,overseed veg-etables with yellow sweetclover in early or mid-summer. A one-row cultipacker greatly improvesgermination of overseeded legumes on theNordell farm in their fresh vegetable operationnear Trout Run,Pa. If in-row weeds are under con-trol and a crop canopy is forming, the clover’sslow start should prevent competition with thecrop. Heavy late-season moisture could causeexcessive clover growth if you have no means tomow between the rows, the Nordells found.

They will sometimes mix yellow sweetcloverwith white and red clover for June overseedinginto early crops. Seeding rate is 15, 4 and 6 lb./A,respectively. The red and white clovers regrow in late summer of Year 2 after the yellow sweet-clover has been clippedtwice,once in late May thenagain at full-bloom in mid-July.

In temperate areas youcan overseed spring broc-coli with HUBAM annualsweetclover, let the cover grow during summer,then till it in before planting a fall crop.Alternatively, you can allow it to winterkill for athick, lasting mulch.

Other OptionsFirst-year forage has the same palatability andfeeding value as alfalfa, although harvest canreduce second-year vigor. Second-year forage is oflower quality and becomes less palatable as plantsmature, but may total 2 to 3 tons per acre (91).

Growers report seed yield of 200 to 400 lb./Ain North Dakota.Minimize shattering of seedpodsby swathing sweetclover when 30 to 60 percentof its pods are brown or black. Pollinating insectsare required for good seed yield (141).

Hard seed that escapes harvest will remain inthe soil seed bank, but organic farmer RichMazour 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,modern sweep cultivators and residue-man-agement tillage implements take care of sweet-

clovers with other tap-rooted “resident vegeta-tion,”Mazour says.

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 (128).

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 low mowing (161).

After 90 days’growth in aNorth Dakota drylandlegume comparison, a Juneplanting of yellow sweet-clover produced dry matterand N comparable to alfalfaand lespedeza (Lespedeza

stipulacea Maxim). Subclover, fava beans (Viciafaba) and field peas had the best overall N-fixingefficiency in the dryland setting because of quickearly season growth and good water useefficiency (270).

SEED

Cultivars. Yellow cultivars include MADRID,which is noted for its good vigor and production,and its relative resistance to fall freezes. GOLDTOP

has excellent seedling vigor, matures two weekslater, provides larger yields of higher quality for-age and has a larger seed than MADRID (302).Yellow common and YUKON joined GOLDTOP

and MADRID—all high-coumarin types—as thehighest yielding cultivars in a six-year NorthDakota test (215).

Leading white biennial cultivars are DENTA,POLARA and ARCTIC. POLARA and ARCTIC are adaptedto very cold winters. Best for grazing are thelower-producing, low-coumarin cultivars DENTA

and POLARA (white) and NORGOLD (yellow).


Sweetclover tolerates a widerange of harsh environments,poor soils and pests.

WHITE CLOVER 147

White clovers are a top choice for “livingmulch”systems planted between rowsof irrigated vegetables or trees. They

are persistent, widely adapted perennial nitrogenproducers with tough stems and a dense shallowroot mass that protects soil from erosion and sup-presses weeds. Depending on the type, plantsgrow just 6 to 12 inches tall, but thrive whenmowed or grazed.Once established,they stand upwell to heavy field traffic and thrive under 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 includemany cultivated varieties, most originally bred

for forage. The best of 36 varieties tested innorth-central Mississippi for cover crop usewere ARAN, GRASSLAND KOPU and KITAOOHA.Theseranked high for all traits tested, including plantvigor, leaf area, dry matter yield, number of seed-heads, lateness of flowering and upright stems toprevent soil contact. Ranking high were ANGEL

GALLARDO, CALIFORNIA LADINO and widely usedLOUISIANA S-1 (321).

White clover performs best when it has plentyof 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 theSouth, 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 after

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


summer annual perennial


establishment. In established stands, it also mayprovide some N to growing crops when it ismanaged as a living mulch between crop rows.Because it contains more of its total N in its rootsthan other legumes, partial tilling is an especiallyeffective way to trigger N release. The low C:Nratio of stems and leaves causes them to decom-pose rapidly to release N (82).

Tolerates traffic. Wherever there’s intensivefield traffic and adequate soil moisture, whiteclover makes a good soil coveringthat keeps alleyways green. Itreduces compaction and dustwhile protecting wet soil againsttrauma from vehicle wheels.White clover converts vulnerablebare soil into biologically activesoil with habitat for beneficialorganisms above and below thesoil surface.

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 takeroot 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, hairy vetch andfava beans (Vicia faba) were the only legumesshown to fix more than 50 percent of their totalN output at the 50 F temperature. Fava bean’s Nfixation rate declined during the period 42 to 105days after planting as ambient temperature

increased, while ladino’s fixa-tion rate increased at each offour sample dates (273).

Overseeded companion crop.Whether frostseeded in earlyspring into standing grain,broadcast over vegetables inlate spring or into sweet corn inearly summer, white clover ger-

minates and establishes well under the primarycrop. It grows slowly while shaded as it developsits root system, then grows rapidly when itreceives more light.

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 (91). Ladino preferssandy loam or medium loam soils.

Use higher seeding rates (5 to 9 lb./A drilled, 7to 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 asalsike 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 allow

Tough, low-growingand shade tolerant,this perennial is oftenused as a living mulchin vegetable systems.

WHITE CLOVER 149

for several freeze-thaw cycles. Make sure warm-soil seedings are established before summerdroughts hit (302).

Late-summer seeding must be early enough togive white clover time to become well estab-lished,because fall freezing and thawing can read-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 (91,302). Legumes suffer less root damage from frostheaving when they are planted with a grass (82).

In warmer regions of the U.S. (Zone 8 andwarmer), every seeding should be inoculated. N-fixing bacteria persist longer in cooler soils, witheven volunteer wild white clover leaving enoughbehind for up to three years (91).

Mowing no lower than 2 to 3 inches will keepwhite 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 (glyphosate, for example) willresult in good to excellent kill of white clover.Extremely close mowing and partial tillage thatleaves any roots undisturbed will suppress, butnot 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.

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 andstems creates a susceptibility to disease and insect

problems.Protect against pest problems by select-ing resistant cultivars, rotating crops, maintainingsoil fertility and employing proper cutting sched-ules (302).

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 vegetables, orchards and vineyards.Living mulch has not proved effective in agro-nomic crops to this point. To receive the multiplebenefits, manage the covers carefully throughoutearly crop growth—to keep them from compet-ing with the main crop for light, nutrients, andespecially moisture—while not killing them.Several methods can do that effectively.

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 (207, 208).

Matthews mulches the transplants with hay, 12inches on each side of the row.He hand-seeds the

WHITE CLOVER (Trifolium repens—intermediate type)

Mar

ian

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Sarr

anto

nio


cover 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 hayfield and replace the berseem, which is not win-terhardy (207, 208).

New Zealand white clover provided goodweed control for winter squash in the wetter oftwo years in a New Yorktrial. It was used in anexperimental non-chemicalsystem relying on over-the-row compost for in-rowweed control. Plants wereseeded into tilled strips 16inches wide spaced 4 feet apart. Poor seed estab-lishment and lagging clover growth in the drieryear created weed problems, especially withperennial competitors.The living mulch/compostsystem yielded less than a conventionally tilledand fertilized control both years, due in part todelayed crop development from the in-row com-post (226).

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 (226).

A California study showed that frequent mowingcan work with careful management. A white clovercover reduced levels of cabbage aphids in harvest-ed broccoli heads compared with clean-cultivatedbroccoli.The clover-mulched plants, in strip-tilledrows 4 inches wide,had yield and size comparableto clean cultivated rows. However, only intensiveirrigation and mowing prevented moisture compe-tition. To be profitable commercially, the systemwould require irrigation or a less thirsty legume,aswell as field-scale equipment able to mow betweenseveral rows in a single pass (67).

Chemical suppression is difficult. An appli-cation rate that sets back the clover sufficientlyone year may be too harsh (killing the clover) ornot suppressive the next year due to moisture,temperature or soil conditions.

Partial rotary tillage. In a New York evaluationof mechanical suppression, sweet corn plantingstrips 20 inches wide were rotary tilled June 2into white clover. While mowing (even five times)didn’t sufficiently suppress clover, partial rotarytilling at two weeks after emergence worked well.A strip of clover allowed to pass between thetines led to ample clover regrowth.A surge of Nwithin a month of tilling aided the growing corn.The loss of root and nodule tissue following stress

from tillage or herbicideshock seems to release Nfrom the clover. Leaf smutcaused less problem on theliving-mulch corn than onthe clean-cultivated checkplot (133).

Crop shading. Sweet corn shading can holdwhite clover in check when corn is planted in 15-inch rows and about 15 inches apart within therow. This spacing yielded higher corn growthrates, more marketable ears per plant and highercrop yields than conventional plots withoutclover in an Oregon study. Corn was planted intotilled strips 4 to 6 inches wide about the sametime the clover was chemically suppressed.Adapted row-harvesting equipment and hand-picking would be needed to make the spacingpractical (105).

Unsuppressed white Dutch clover established atasparagus planting controlled weeds and providedN over time to the asparagus in a Wisconsin study,but reduced yield significantly. Establishing theclover in the second year or third year of an aspara-gus planting would be more effective (251).

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 proteinand 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.

Healthy stands can produce 80 to 130 lb. N/A when killedthe year after establishment.

WHOOLLYPOD VETCH 151

COMPARATIVE NOTES

• White clover is less tolerant of basic soilsabove pH 7 than are other clovers.

• In a Wisconsin comparison, ladino clover bio-mass was similar to mammoth red cloverwhen spring-seeded (330).

• 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.


WOOLLYPOD VETCHVicia villosa ssp. dasycarpa

Also called: LANA 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 Californiarely 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 woollypodvetch each year with oats or as part of a legumemix—common vetch, subterranean clover, a

medic 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 and warmer. A study in California showed that


LANA provided the most N and suppressed themost weeds during two consecutive but distinctlydifferent growing seasons, compared with purplevetch and other legume mixtures (342, 343).

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 one weekafter emergence.

LANA can contribute as much as 300 pounds ofN its first year or two, given adequate moistureand warm spring growing conditions (219, 324).Fall-planted LANA incorporated before a corn cropcan provide a yield response equivalent to 200 lb.N/A, a California study showed (219). Similarresults have been seen in tomato research inCalifornia (324). In western Oregon, a yieldresponse equivalent to 70 lb. N/A for sweet cornhas been observed (87).

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 inZone 7 and warmer. LANA

shows explosive growth inearly spring in the PacificNorthwest (87) and in latewinter and early spring inCalifornia when moisture isadequate. It can provide up to 8,000 lb. DM/A,which breaks down quickly and improves soilstructure (44, 219, 324).

Frost protectant. Some orchard growers havefound that keeping a thick floor cover before theblossom stage can help prolong a perennialcrop’s dormant period by up to 10 days inspring.“This reduces the risk of early frost dam-age (to the blossoms, by delaying blossoming)and lengthens the blossoming period of myalmond trees,” notes almond grower GlennAnderson, Hilmar, Calif.

Smother crop. Woollypod’s dense springgrowth smothers weeds and also provides someallelopathic benefits. Of 32 cover crops in a repli-cated study at a California vineyard, only LANA

completely suppressed biomass production ofthe dominant winter annual weeds such as chick-weed, shepherd’s purse, rattail fescue and annualryegrass (351).

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 (142).

MANAGEMENT

Establishment & FieldworkWoollypod does well on many soil types—evenpoor, sandy soil—and tolerates moderately acidicto moderately alkaline conditions. It’s well-adapted to most orchard and vineyard soils inCalifornia (351).

It establishes best in recently tilled, nutrient-deficient fields (5). Tillage helps enhance thereseeding capability of vetches (44). LANA woolly-pod vetch hasn’t done as well in some no-till sys-

tems as it was expected to.Given adequate moisture,however, broadcasting LANA

even at low to moderaterates—and with light incor-poration—can give satisfac-tory results from fall

seedings,especially if the stand is allowed to growthrough mid-spring. If your goal is to shade outcompetition quickly, however, broadcast at medi-um to high rates and incorporate lightly.

You might not recognize the emerging plantwithout 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.

Woollypod vetch is oftenused in mixes in Californiaorchards and vineyards.

WOOLLYPOD VETCH 153

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 establishinga 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 (167).

Bartolucci prefers to drill rather than broadcastcover 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.

Don’t wait too long in fall to seed woollypodvetch in Zone 7 and warmer, however. If you wait until the soil starts getting cold, in mid-October in Oregon and early November in partsof central California,germination will be poor andthe stand disappointing. Seed too early, though,and you miss the early moisture benefit of theCentral Valley’s fog season (5) and will need toirrigate more before the rainy season (168).

Regardless of your planting method,seed wool-lypod vetch into moist soil or irrigate immediate-ly after seeding to help germination (219). 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 (300).

Mowing & ManagingWoollypod vetch can survive freezing conditionsfor days, but severe cold can markedly reduce itsdry matter and N production (170, 219).

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 (87).

Woollypod responds well to mowing,as long asyou 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 ortwice 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 toa 12-inch height can help keep them from trellis-ing over vine cordons. In vineyards withoutsprinklers for frost protection, some growersincorporate legume mixes in spring, before thesoil becomes too dry for disking. Where sprin-

WOOLLYPOD VETCH (Vicia villosa ssp.dasycarpa)

Elay

ne

Sear

s


klers are used, the covers might be allowed togrow for a longer period and provide additionalN. Timing is important when disking, however,as you don’t want to make equipment accessdifficult or compact soil during wet springconditions (167).

Given the high dry matter production fromwoollypod 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 (350).

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 rowsfor the first time. In Californiavineyards where irrigation isn’tused, a few growers report thatvines seem to lose vigor fasterwhen grown with cover crops.Others haven’t observed thiseffect.After a few years of grow-ing leguminous covers,many find that their soil isholding moisture better and they need less waterto 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.

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 Glenn Anderson.

It’s natural to expect a change in the residentvegetation over time, observes Anderson. After afew years of reseeding itself—and providingabundant dry matter and nitrogen—the LANA hehad clear seeded at low rates between orchardrows on half his acreage eventually diminished to

about 10 percent of the resident vegetation, henotes. Subclovers and other legumes he intro-duced have become more prominent. Thoselegumes may have better self-reseeding capabilitythan LANA, other growers note (168).

Pest ManagementWoollypod vetch outcompetes weeds and willquickly resolve most weed problems if seeded athigh rates. Woollypod also provides someallelopathic benefits. A root exudate can reducegrowth in some young grasses, lettuces and peas,however.

Hard seed carryover can cause LANA to becomea weed in subsequent cash crops and vineyards,however (55). Its strong climbing ability cancover grape vines or entwine sprinklers. In

orchards, it’s fairly easy to cut orpull Lana vines out of thecanopy of young trees. Mowingor “high chopping” may beneeded, especially in vineyards,even though this can reduceLANA’s reseeding rate.

Insects pests aren’t a majorproblem with woollypod vetch, in part because itattracts lady beetles, lacewings, minute piratebugs and other beneficials insects that help keeppests 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 seedproducer, but its pods are prone to shattering.You can increase seed harvest by raking the field (without mowing, if possible) to gather the crop into windrows for curing, before

LANA woollypod vetchshows explosive growthin early spring in thePacific Northwest.

WOOLLYPOD VETCH 155

combining with a belt-type rubber pickupattachment (350).

Forage. Like most vetches, LANA is a somewhatbitter yet palatable forage when green, and thepalatability increases with dryness (350). It is anutritious forage for rangeland use (350).

For hay, it is best cut in full bloom.The leavesdry rapidly and swaths can be gathered within aday or two (350).

COMPARATIVE NOTES

• Woollypod has slightly smaller flowers thanhairy vetch, and its seeds are more oval thanthe nearly round seeds of hairy vetch. LANA

also has a higher proportion of hard seed thanhairy vetch (351).

• LANA shows more early growth than commonvetch, although both increase their biomassdramatically by midspring (168).

• LANA and purple vetch are more cold-sensitivethan common vetch or hairy vetch.Once estab-lished,LANA can tolerate early frosts for a fewdays (especially if the temperature doesn’t fluc-tuate widely or with some snow cover) and ishardier than purple vetch,which is more sus-ceptible to early spring dieback (114).

• LANA flowers about three weeks earlier thanpurple vetch and has a better chance of set-ting seed in dryland conditions (219).

• LANA and LANA mixes suppress weeds betterthan purple vetch (114).

Seed sources. Widely available in the West,including Ampac, Harmony, Lohse Mill andPeaceful Valley. See Seed Suppliers (p. 166).


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 niche? Start with small plots sep-arated from cropped fields and plant over a rangeof dates, under optimal soil and weather condi-tions.

If you’re sure of the niche and have just two orthree covers to try, put the trial right in yourcropped fields, using a similar seedbed prepara-tion. This method provides rapid feedback onhow the cover crops fit into your cropping sys-tem. Keep in mind management-related variablescould cause subpar results for an otherwise ade-quate cover.

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 seedprice seems high. If it works well, it could trimother costs. You could consider growing yourown seed eventually, and perhaps even selling itlocally.

Be sure to obtain appropriate inoculants ifyou’ll be testing legumes, which require species-specific rhizobial bacteria so the cover can cap-ture and “fix”N efficiently. See Nodulation:MatchInoculant to Maximize N (p. 92).

C. Determine plot sizes. Keep them smallenough to manage, yet large enough to yield ade-quate and reliable data. Plots a few rows wide by50 to 100 feet could suffice if you grow vegetablesfor market. If you have 10 or more acres, quarter-

or half-acre plots may be feasible,especially if oth-ers in your area use similar species.

If you use field-scale machinery, establish field-length plots. For row crops, use plots at least fourrows wide, or your equipment width. Keep inmind the subsequent crop’s management.

D. Design an objective trial. Plots need to be asuniform as possible, randomly selected foreach option you’re testing, and replicated (atleast two or three plots for each option).

If parts of the field have major differences(such as poorer drainage or weedy spots), putblocks of plots together so each treatment hasequal representation in each field part, or avoidthose areas for your trial.

Label each plot and make a map of the trial area.

E. Be timely. Regard the trial as highly as any other crop. Do as much or as little fieldpreparation as you would for whole fields, and atan appropriate time.

If possible, plant on two or more dates at leasttwo weeks apart. In general, seed winter annualsat least six weeks before a killing frost.Wheat andrye can be planted later, although that will reducethe N-scavenging significantly.

F. Plant carefully. If seeding large plots withtractor-mounted equipment, calibrate your seed-ing equipment for each cover. This can preventfailures or performance differences due to incor-rect seeding rates. Keep a permanent record ofdrill settings for future reference.

A hand-crank or rotary spin seeder works wellfor small plots getting less than five pounds ofseed.Weigh seed for each plot into a separate con-tainer. 1 lb./A is about equivalent to 1 gram/100sq. ft., and 1 pound equals 454 grams.

Put half the seed in the seeder and seedsmoothly as you walk the length of the field andback, with a little overlap in the spread pattern.

APPENDIX A

TESTING COVER CROPS ON YOUR FARMby Marianne Sarrantonio

TESTING COVER CROPS 157

Then seed the remainder while walking in per-pendicular directions so you crisscross the plot ina gridlike pattern.

If broadcasting by hand, use a similar distribu-tion pattern.With small seed, mix in sand or freshcat litter to avoid seeding too much at a time.

G. Collect data. Start a trial notebook or binderfor data and observations.

Management information 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 after

establishment• 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 weather and record dates such asfirst frost. Note anything you think has a bearingon the outcome, such as weed infestations.

If time allows, try killing the cover crops andcontinuing your expected rotation, at least on asmall scale.You might need hand tools or a lawnmower. Use field markers to identify 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 thequestions 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 even

more affordableIn year two, expand the scale. Test your best-

performing cover as well as a runner-up. Withfield crops, try one-acre plots; stick with smallerplots for high-value crops. Also try any optionsthat might 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

cover work better in your farm system. Forexample, killing a cover earlier than you’d likewill reduce the amount of biomass or N itprovides, but could ensure you plant summercrops on time.

In most cases, fine-tuning your managementalso makes it more affordable.Lowering a seedingrate or shifting the seeding date also could reducethe tillage needed. Narrower rows might hinderestablishment of an overseeded legume butreduce weeds and bump up the cash crop yield.Finding a regionally adapted variety of a givenspecies could simplify management—but alsomight have you looking around for a better cashcrop variety.

Don’t expect all of a cover’s benefits to showup in yearly economic analyses.Some benefits arehard to assess in dollars.

When talking to other farmers, seed suppliersand agricultural experts, tell them about yourcover cropping experiences and ask for sugges-tions and ideas. Your best covers may seem


unbeatable. But there could be an up-and-com-ing species or management technique youhaven’t thought of testing. See Up-and-ComingCover Crops (p. 158) for a few examples.

Overwhelmed? You needn’t be. Initiative andcommon sense—traits you already rely on—arefundamental to any on-farm testing program. As a grower, you already test varieties, plantingdates and other management practices every

year.This section offers enough tips to start test-ing cover crops.

You also can collaborate with others in yourregion to pool resources and share findings.There’s a good chance others in your area couldbenefit from your cover cropping wisdom!

[Adapted from Northeast Cover CropHandbook by Marianne Sarrantonio, RodaleInstitute, 1994.]

APPENDIX B

UP-AND-COMING COVER CROPSWe chose the major cover crops in this book fortheir range of benefits, reliability, availability andwide adaptability. They’re not the only covercrops to choose from, of course. Here are a fewothers you might want to consider,either for theirregional appeal or because they show strongpotential once seed becomes readily available.

Balansa cloverIdentified as a promising new cover crop inMississippi research, balansa clover (Trifoliumbalansae) is a small-seeded annual legume withsuperior reseeding potential compared withother legumes, including crimson clover.

Well-adapted to a wide range of soil types, bal-ansa performs particularly well on silty clay soilwith a pH of about 6.5. It does not do well onhighly alkaline soils (18). It appears to be hardythroughout Zone 7A and is considered marginalin Zone 6B.

Balansa clover seed is quite small, so the seed-ing rate is only 10 lb./A. The seed is expensiveand not widely available, however. It is producedcommercially only in Australia at this time.Balansaclover requires a relatively rare inoculant, desig-nated “Trifolium Special #2” by Liphatech, Inc.,manufacturer of “Nitragin” brand inoculants. (SeeAppendix D, Seed Suppliers, p. 166, for contactinformation for Liphatech, Inc. and for KamprathSeed Co., which imports balansa seed).

PARADANA is the cultivar that has been tested inthe U.S. It was released in 1985 by the South

Australia Department of Agriculture. A newercultivar, BOLTA, was tested in California and Texasin 1997.

While PARADANA seed matures slightly earlierthan crimson clover, it often does not produce asmuch biomass.But PARADANA can reseed for sever-al years, due to its relatively high amount of hardseed. It has volunteered back for four years fol-lowing maturation of a seed crop in 1993 inSenatobia,Miss., and has reseeded successfully forat least two years in no-till systems at several otherlocations in Alabama, Georgia and Mississippi.Neither TIBBEE nor AU ROBIN crimson cloverreseeded for more than one year at any location inthose tests. It’s too soon to say how well balansaclover reseeds after tillage, but the small seededclover probably can’t stand being buried toodeeply.

Balansa is a bit less likely than crimson cloversto host root-knot nematodes (Meloidogyne incog-nita, race 3).In research by Gary Windham,USDA-ARS, Starkville, Miss., balansa had egg mass indexscores between 2.3 and 2.9 on a scale from 1 to5. For comparison, a very resistant white cloverbeing readied for release has a 1.5 score, mostcrimson clovers score between 3 and 3.5 andvery susceptible crops like REGAL white cloverscore a 5.

Balansa was screened at several locations in arange of soil types and climatic zones varyingfrom the Gulf Coast to northern Tennessee, andfrom Georgia to western Arkansas.Since the initial

UP-AND-COMING COVER CROPS 159

screening, a number of farmers have been evalu-ating balansa in trials covering an even wider geo-graphic area.

For further information, contact:Seth Dabney USDA-ARS National Sedimentation Lab.P.O. Box 1157 Oxford, MS 38655-2900 (662) 232-2975; [email protected]

Bell bean (Vicia faba)Other common names: fava bean, faba bean,small-seeded horse bean.Type: Winter annual or spring annual legume.Description: Stems coarse, upright; leaves com-pound, usually with six broad leaflets and no ten-drils; dark purple extrafloral nectary on lowersurface of stipule; flowers large, white, with darkpurple blotches;pods large,cylindrical,containingsix to eight seeds.

Bell bean is a true vetch,but differs greatly fromother vetches with its strong, upright growth. Italso has a relatively shallow, thick taproot, whichmay be useful for opening up heavy soils. Bellbean often is used in mixtures with vetches, peasand/or cereals. Because of its height and becauseit does not tolerate close mowing, it often is omit-ted from mixtures in frost-prone areas. It is bestadapted to Hardiness Zones 8 and 9.

Bell bean is frequently infested by the pea-beanaphid, which seldom affects its use as a covercrop. The aphid, which does not attack grapes,and the presence of extrafloral nectaries, mayattract beneficial insects into vineyards. However,their effects on insect and mite management havenot been tested.

Bell bean is more susceptible to frost damagethan other vetches. It is very similar in growth tobroad bean (also known as Windsor or horsebean), which has a much larger, flat seed. Thesmaller seed size of bell bean makes it more eco-nomical to sow.

Bell beans grow quickly throughout the winterin California, add N—although less than othervetches—and provide a tall structure to supporttwining vetches and peas. Bell beans do notspread like vetches and they have no hard seed.

They are easily incorporated into the soil.Estimated amount of N fixed may range from 50-200 lb/acre, but bell bean is regarded as a lownitrogen fixer in southern California. In six weeksof growth,bell bean may fix up to 100 lb/acre anda total of up to 150 lb/acre on fertile soils.

Seed 1 to 3 inches deep at 80-200 lb./A. Fababean can grow on a wide range of soils, fromloams to clays, and under a variety of drainageconditions. It does not tolerate saturated soils,andextended drought, especially at flowering,reduces seed production drastically.

Bell beans are not drought tolerant. They areeasier to control than other vetches.Bell beans donot tolerate close mowing.—Chuck Ingels University of California Extension4145 Branch Center Rd.Sacramento, CA 95827-3898(916) 875-6913; FAX: (916) [email protected]

Black oatsBlack oats (Avena strigosa) is the No. 1 covercrop on millions of acres of conservation-tilledsoybeans in southern Brazil. In the temperatefarming regions of southern South America, blackoats owes its popularity to a number of factors. Itis very resistant to rusts and produces largeamounts of biomass, similar to rye. It has excep-tional allelopathic activity for weed control. It iseasy to kill mechanically and cycles nitrogen bet-ter than rye.

Black oats breaks disease cycles for wheat andsoybeans and is resistant (some research claimseven suppressive) to root-knot nematodes. On top of this, it is also a good forage. It is not coldtolerant.

One cultivar, IAPAR-61, a public release devel-oped by the Paraná State Agricultural ResearchService, has been investigated by USDA-ARS andwas grown in 1997 in Alabama and Georgia forcommercial seed production. Its use likely will berestricted to the lower southern Coastal Plain(Zones 8b, 9 and 10). Seed should be availablecommercially in limited amounts in 1998.—D.W. Reeves (see p. 161)


Foxtail (German) milletFoxtail millet (Setaria italica) has a variety ofcommon names.Most literature refers to it as fox-tail millet due to its similarity to other members ofthe Setaria genus (several species of weedy fox-tails). Other common names include German mil-let, Hungarian millet and Italian millet. Comparedto the weedy species of foxtail, this millet has amuch larger seed head, larger golden-coloredseed, bigger plants and a higher seed yield. Thisplant was used for centuries in China as an impor-tant food grain. The crop has been grown as afood grain, forage and occasionally for birdseedproduction. The main use in the U.S. has been forforage production, primarily in the Great Plains.

Foxtail millet is a warm season crop, and willnot overwinter. Its best use as a cover crop wouldbe following spring-harvested vegetables in areasotherwise left fallow for a summer,or in southernregions as a cover crop planted in mid-summer.Although foxtail millet is a relatively short seasoncrop (90 to 100 days in the lower Midwest), itmust be planted in the first half of the summer tomaximize biomass production. If planted late,such as mid-July through August,the plants will bemuch shorter in stature and less vigorous.

The competitive advantage of foxtail millet liesin its drought tolerance, relatively quick growthand its status as a warm season annual that can bedrilled in narrow rows.The crop is relatively easyto establish, like oats or wheat, and establishesbest when drilled rather than broadcast.With ade-quate rainfall, the crop will reach 3 to 4 feet tallwithin about 50 to 60 days, but will be shorterunder limited moisture conditions or when plant-ed late. Foxtail millet fits a mid-summer niche notfilled by cool season grains such as wheat, oatsand rye. It provides more biomass in a short peri-od than many warm season grasses, though per-haps not as much as sorghum or pearl millet.Compared to those two crops however, foxtailmillet may provide better erosion control becauseit can be drilled in narrow rows.

Foxtail millet is somewhat easier to establishthan pearl millet, and although both are moredrought tolerant than corn, pearl millet would befavored on sandy soils.

Some vegetable growers in eastern states suchas Maryland have planted foxtail millet afterspring vegetable harvest as a cover crop. Controlmethods later in the summer have included spray-ing, mowing and rolling the crop flat (the rollingseems to provide a high percentage of controlwithout need for further action).

Disadvantages of foxtail millet are that it cannotbe used after fall-harvested crops (too little vigorwhen planted in the cool fall months) and that itcould be a host to some pests of other cereal graincrops—as is true of any grass cover crop. Foxtailmillet is not likely to be a weed, since it does nothave hard seed; any foxtail millet plants that vol-unteer the next season can be easily controlledsimilar to volunteer oats.

Some seed dealers sell foxtail millet under ageneric name, often as German millet (be sureyou are getting foxtail millet, and not some otherspecies such as proso millet or pearl millet).University cultivars include RED SIBERIAN, GOLDEN

GERMAN,WHITE WONDER, SNO-FOX and MANTA. Seeddealers most likely to carry foxtail millet are thoselocated in the Great Plains region, particularly inNebraska.—Robert L. Myers, Jefferson Institute601 West Nifong Boulevard, Suite 1D,Columbia, MO 65203(573) 449-3518; [email protected]

LupinWhite lupin (Lupinus albus) and blue or narrow-leaf lupin (Lupinus angustifolius) are cool-seasonannual legumes that provide plenty of N and canbe grown widely in the U.S.and southern Canada.As a fall and winter cover crop in the southeast-ern U.S., white lupin is the most cold-tolerant.Some cultivars overwinter as far north as theTennessee Valley (287). Spring cultivars can beseeded in early April in the northern U.S. andsouthern Canada and plowed down around mid-June when they’re in the early-bloom to early-podstage and at peak biomass.

For use as a cover crop, drill lupins no deeperthan 1 inch at rates varying from 70 lb./A (forsmall-seeded blue varieties) to 120 lb./A (for larg-er-seeded white varieties). At $30 to $40 per acre,

UP-AND-COMING COVER CROPS 161

the seed is relatively expensive. Be sure to inocu-late lupin seed with compatible rhizobia.

Lupins have aggressive taproots, especially thenarrow-leaf cultivars, and they can fix up to 350lb. N/A. Under normal growth conditions andwhen killed in early spring, they typically contain100 to 150 lb. N/A in their biomass.You can killlupins easily either mechanically or with herbi-cides.Their hollow stems crush or break readily,making it easy to plant cash crops using conser-vation tillage equipment.

Lupin species were named after their originalflower colors,but both species now have cultivarsthat may have white,blue or magenta/purple flow-ers.Blue lupin is adapted to the lower Coastal Plainand is more readily identified by its narrow leaflets(about 0.5-inch wide) rather than flower color.

Only two lupin cultivars are readily available ona commercial scale:TIFWHITE-78,a white lupin,andTIFBLUE-78, a narrow-leaf lupin, both released byUSDA’s Agricultural Research Service in the1980s. These two varieties, and other modernvarieties, are “sweet” types as opposed to “bitter”types that were widely grown in the South priorto 1950.Sweet varieties have a low concentrationof naturally occurring alkaloids.High alkaloid con-tent in the plants makes lupin seed and forageunpalatable for livestock.

Recent research suggests that alkaloids play amajor role in resistance to disease and pests(including insects and nematodes). High-alkaloidlupins are therefore being selected and bred foruse as cover crops rather than as animal feed.Anecdotal evidence suggests that sweet lupincover crops can act as a trap crop for thrips(Frankliniella spp.) in cotton plantings.

Lupins are susceptible to some fungal and viraldiseases and should not be grown in the samefield in successive years. It is best to rotate lupincover crops with a small grain cover crop.

For information about lupins and seed sources,contact:D.Wayne Reeves, Research Agronomist,USDA-ARS National Soil Dynamics Laboratory,411 S. Donahue St., P.O. Box 3439 Auburn, AL 36832-5806(334) 844-4666; FAX: (334) 887-8597 [email protected]

Sunn hempA tropical legume that grows rapidly, sunn hemp(Crotalaria juncea) can produce more than5,000 lb.dry matter/A and 120 lb.N/A in just nineto 12 weeks. It can fill a narrow niche betweenharvest of a summer crop and planting of a fallcash or cover crop. Sunn hemp sown bySeptember 1 following a corn crop in Alabama,forexample, can produce an average of 115 lb. N/Aby December 1.

Sunn hemp is not winter hardy and a hardfreeze easily kills it. Sow sunn hemp a minimumof nine weeks before the average date of the firstfall 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 management caution: Many Crotalariaspecies contain alkaloids that are poisonous tolivestock. However, the sunn hemp variety TROPIC

SUN,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 resistantand/or suppressive to root-knot (Meloidogynespp.) and reniform (Rotylenchulus reniformis)nematodes.—D.Wayne Reeves (see this page)

TeffTeff (Eragrostis tef), or tef, is a grain grown pri-marily in Ethiopia, where it survives under harshconditions in poor soils. Teff has been researchedvery little outside of east Africa, but has receivedoccasional attention by U.S. researchers. Mostsmall test plots have focused on teff as a cerealgrain crop,but it also has potential as a forage,andis reportedly used some for grazing in SouthAmerica and Australia.

Limited studies point to teff’s ability to grow onpoor soils. Although it is best to drill it, teff alsocan be established by broadcast seeding becausethe seed is less than 1 mm in size.This allows theseed to fall into cracks and crevices of a preparedsoil and not lay exposed on the surface.However,


the fact that the seed is so tiny and light also couldmake it difficult to broadcast uniformly on awindy day, and makes the seed hard to handle inmany conventional planters. If broadcast, theseedbed probably should be tilled first—no infor-mation is available about broadcasting it underno-till conditions.

Teff grows relatively quickly, and, althoughshort (18 to 24 in. tall), can establish a relativelygood ground cover. The leaf blades are narrow,but the crop tends to establish a high number ofplants per unit area.Teff is a warm season annualthat is probably best planted in June in moststates, which limits the conditions under which itwould be cover cropped. It might possible toplant it later, but this has not been tested.

The biggest limitation of teff as a cover crop isthe lack of a seed source.The USDA-ARS NationalPlant Germplasm System maintains several genet-

ic lines of teff available to researchers,but there isno commercial source of seed in the U.S. Onefarmer in the Pacific Northwest grows teff forEthiopian restaurants and other buyers, but doesnot routinely distribute seed. This would be agood crop for a plant breeder to breed and releasea variety for commercial distribution.Teff poten-tially could be used for temporary ground coverduring construction, when soil is left bare for aperiod of months,but where a winter cover is notneeded.Teff does not produce quite the biomassof some of the taller warm season grasses, butbecause it can be broadcast, it may confer someadvantages. Teff has not become a volunteer orweed problem following several years of testplots in Missouri. Its potential for serving as analternative pest host is unknown.—Robert L. Myers (see p. 160)

APPENDIX C

RECOMMENDED RESOURCESThis list is for information purposes only. Inclusion does notimply endorsement, nor is criticism implied of similarresources not mentioned.

Abdul-Baki,Aref and John R.Teasdale. 1997.Sustainable Production of Fresh-MarketTomatoes and Other Summer Vegetables withOrganic Mulches. Farmers’ Bulletin No. 2279,USDA-ARS, Beltsville, Md. 23 pp.http://www.ars.usda.gov/is/np/tomatoes.html

Appropriate Technology Transfer for Rural Areas(ATTRA). 1998. Cover Crops and GreenManures: Benefits, Uses and LiteratureResources.ATTRA. Fayetteville,Ark.

Bailey, R. G., P. E.Avers,T. King and W. H. McNab.1994. Ecoregions and subregions of the UnitedStates (map).Washington, DC: USDA ForestService. 1:7,500,000.With supplementary tableof map unit descriptions, compiled and editedby W. H. McNab and R. G. Bailey.http://www.fs.fed.us/land/ecosysmgmt/pages/ecoreg1_home.html

Barnes, Robert F., et al. 1995. Forages:The Scienceof Grassland Agriculture. 5th Edition. 2 vol. IowaState Univ. Press,Ames, Iowa.

Clark,Andrew J. et al. 1994. Seeding rate and killdate effects on hairy vetch-cereal rye cover cropmixtures for corn production.Agron. J. 86:1065-1070.

Cramer, Craig, George DeVault, Mike Brusko,Fred Zahradnik and Lesa Ayers (eds.). 1985. TheFarmer’s Fertilizer Handbook: How to makeyour own NPK recommendations…and makethem pay. Regenerative Agriculture Association,Emmaus, Pa. 176 pp.

Dabney, S. M. 1995. Cover crops in reducedtillage systems. pp. 126-127. Proc. BeltwideCotton Conferences. 5 Jan 1995. National CottonCouncil, Memphis,Tenn.

RECOMMENDED RESOURCES 163

Dyer, David A. 1998. Conservation LegumeVarieties in the United States. USDA Handbook.Plant Materials Center, P.O. Box 68, Lockeford,Calif. 95237, (209) 727-5319.

Duke, James A. 1981. Handbook of Legumes ofWorld Economic Importance. Plenum Press, N.Y.343 pp. Compendium of botanical, cultural andmanagement information. Excellent linedrawings.

Duval, Jean. 1997. Cover Cropping in PotatoProduction. Ecological Agriculture Projects.Publication No. 72.An eight-page bulletin withconcise descriptions of how to use legume,cereal and brassica cover crops; excellent chartfor planning rotations with benefit analysis ofvarious covers.

Hanson, James C. et al. 1993. Profitability of no-tillage corn following a hairy vetch covercrop. J. Prod.Ag. 6:432-437.

Hanson, James C. et al. 1997. Organic versusconventional grain production in the mid-Atlantic: an economic and farming systemoverview. Amer. J.Alt. Ag. 12:2-9.

Hargrove,W.L. (ed.). 1991. Cover Crops for CleanWater. Proc. Int’l Conf.April 9-11, 1991.WestTennessee Experiment Station, Jackson,Tenn. Soiland Water Conservation Society.Ankeny, Iowa.

Hofstetter, Bob. 1988. The New Farm’s covercrop guide: 53 legumes, grasses and legume-grassmixes you can use to save soil and money. TheNew Farm 10:17-22, 27-31.

Ingels,Chuck A.et al.1994.Selecting the right covercrop gives multiple benefits.Calif.Ag. 48:43-48.

Ingels, C.A., R.L. Bugg, G.T. McGourty, and L.P.Christensen. 1998. Cover Cropping in Vineyards:A Grower’s Handbook. University of California,Div. of Agriculture and Natural Resources. InPress. Chapters on cover crop species, soil/watermanagement, pest management, 12 growers.Charts of seeding rates, seed costs.

Macey,Anne. 1992. Organic Field CropHandbook. Canadian Organic Growers Inc.,Ottawa, Ont. 192 pp. Practical handbook cover-ing principles of organic farming, how to designcrop rotations and species-specific chapters on11 cash and cover crops.

Matheson, Nancy, Barbara Rushmore, James R.Sims, Michael Spengler and E.L. Michalson. 1991.Cereal-Legume Cropping Systems: Nine farmcase studies in the dryland northern plains,Canadian prairies and intermountainNorthwest.Alternative Energy ResourcesOrganization (AERO), Helena, Mont. 75 pp.Anexcellent description of these innovative systemswith clear diagrams and great management detailof how crops are selected.

MacRae, R.J. and G.R. Mehuys. 1985.The effect ofgreen manuring on the physical properties oftemperate-area soils. Adv. Soil Sci. 3:71-94.

McVay, K.A. et al. 1989.Winter legume effects onsoil properties and nitrogen fertilizer require-ments. Soil Sci. Soc. of Amer. J. 53:1856-1862.

Michigan State University. 1996. Cover CropsSymposium Proceedings. Michigan StateUniversity,W.K. Kellogg Biological Station, BattleCreek, Mich. 20 pp.

Miller, P.R. et al. 1989. Cover Crops for CaliforniaAgriculture. University of California, Div. Of Ag.and Natural Resources Publication 21471, 24 pp.Oakland, Calif.

National Assn. of Wheat Growers Foundation.1995. Best Management Practices for Wheat:A Guide to Profitable and EnvironmentallySound Production. National Assn. of WheatGrowers Foundation.Washington, DC.

Oregon State University. 1998. Using CoverCrops in Oregon. Publication #EM-8704.Available for $5.50 from Publication Orders,Extension and Station Communications,Oregon State University, 422 Kerr Administration,Corvallis, OR 97331.


Reeves, D.W. 1994. Cover crops and rotations. pp.125-172. In J.L. Hatfield and B.A. Stewart (eds.).Crops Residue Management. 1994. LewisPublishers,Ann Arbor, Mich.

Sainju, Upendra M. and Bharat P. Singh. 1997.Winter cover crops for sustainable agriculturalsystems: Influence on soil properties, waterquality and crop yields. Hort Sci. 32:21-28.Comprehensive overview of cover crop effectson N, soil organic C and N properties; chart on N contributions, water nitrate movement,research needs.

Sarrantonio, Marianne. 1994. Northeast CoverCrop Handbook. Soil Health Series. RodaleInstitute, Kutztown, Pa. 118 pp.

Sarrantonio, M. 1991. Methodologies forscreening soil-improving legumes. RodaleInstitute. Kutztown, Pa.

Shirley, Christopher and The New Farm staff.1993. What Really Happens When You CutChemicals? Rodale Institute, Kutztown, Pa. Lotsof farmer profiles and details on usage of covers.

Smith, Miranda et al. 1994. The Real Dirt:Farmers Tell About Organic and Low-InputPractices in the Northeast. Northeast OrganicFarming Association and Northeast Region SARE,Burlington,Vt. 264 pp.

Stute, Jim. 1996. Legume Cover Crops inWisconsin. Wisconsin Department of Agriculture,Sustainable Agriculture Program. Madison,Wis.27pp.

Stute, J.K. and J.L. Posner. 1995. Legume covercrops as a nitrogen source for corn in an oat-corn rotation. J. Prod.Ag. 8:385-390.

Sustainable Agriculture Network. 1997.Steel in the Field:A Farmer’s Guide to WeedManagement Tools. Greg Bowman, ed.

Sustainable Agriculture Network. Beltsville, Md.Shows how today’s implements and techniquescan control weeds while reducing—or eliminat-ing—herbicides. Farmer accounts include howcover crops and tillage tools are used in tandemto control weeds.

Teasdale, John R. 1996. Contribution of covercrops to weed management in sustainableagriculture systems. J. Prod.Ag. 9:475-479.

University of California Sustainable AgricultureResearch and Education Program. 1997. CoverCrops: Resources for Education and Extension.David Chaney and Ann D. Mayse, compilers.<[email protected]>.Three-ring binder ofeducational resources including Internet, printmaterials, cover crop profiles, videos and slidesets, and a list of experts.

University of Wisconsin et al. 1990. AlternativeField Crops Manual. Univ. of Wisconsin-Extension and Univ. of Minnesota, Madison,Wis.and St. Paul, Minn.Three-ring binder withdetailed descriptions of agronomic use for 35crops and short narratives on 13 more crops.Tabbed, referenced.

Wagger, Michael G. 1989.Winter annual covercrops. pp. 59-61. In M.C. Cook and W.M. Lewis(Eds.). Conservation Tillage for Crop Production.Publication No.AG-407.Agricultural ExtensionService, North Carolina State University. Crimson,hairy vetch, cahaba vetch, field peas mentionedin this brief overview of planting and managingcover crops.

Zalom, Frank G. 1995.A cover crop system forvineyard pest, weed and nutrition management.#LW91-26.Western Regions SARE. Utah StateUniv. Logan, Utah. Describes management of win-ter annuallegume/grass cover crops to controlleafhoppers, spider mites and weeds.

RECOMMENDED RESOURCES 165

USDA Sustainable Agriculture Networkhttp://www.sare.orgBrowse or search for cover crop information:The first edition of Managing Cover CropsProfitably, the database of SARE projects, andthe archives of the sustainable agriculture list-serv, sanet-mg.

Managing Cover Crops Profitably USDA Sustainable Agriculture Network http://www.sare.org/htdocs/pubs/mccp/ This on-line version of the predecessor of thispublication includes some covers not mentionedhere, plus guides to proven covers by region,summaries of more than 30 cover crops andmixes, and more.The information was compiledin 1991, but most of it is still useful.

Cover Crop Resource Page Sustainable Agriculture Research and EducationProgram (SAREP) University of California http://www.sarep.ucdavis.edu/ccrop An extensive site (not just for California farmers)that includes a searchable database of more than5,000 items, 400 online images and detailedinformation on 32 cover crop species. Manyvaluable gleanings from the scientific literaturecompiled in useful, readable form.

Cover Crops Menu Sustainable Farming Connectionhttp://sunsite.unc.edu/farming-connection/covercro/home.htm Includes farmer features and links to other covercrop sites.

ATTRA http://www.attra.org Appropriate Technology Transfer for Rural Areas(ATTRA), a nation-wide sustainable farming infor-

mation center located at the University ofArkansas, has a website that features many of the publications and resource lists developed byprogram specialists in response to inquiries fromfarmers since 1987. Call 1-800-346-9140

Ohio State University. 1995. The Value ofLegumes for Plowdown Nitrogen.http://ohioline.ag.ohio-state.edu/agf-fact/0111.html

HELPFUL VIDEOS No-Till Vegetables—A Sustainable Way toIncrease Profits, Save Soil and ReducePesticides This 38-minute video covers the basics of sus-tainable no-till vegetable production includingno-till transplanting into cover crops, pioneeredby Pennsylvania grower Steve Groff. Send $24.95($26.95 for overseas orders) check or moneyorder to: Cedar Meadow Farm, 679 Hilldale Road,Holtwood Pa. 17532. For more info, email:[email protected] or phone (717) 284-5152.

Using Cover Crops in ConservationProduction Systems An 11-minute video from the USDA-ARS NationalSedimentation Lab in Oxford, MS, this programcan be obtained for $10 (postpaid) from:Shepherd Productions, 5004 Sequoia Rd,Memphis,TN 38117-2016, (901) 272-0350

Controlled Rotational Cover Cropping inthe Bio-Extensive Market Garden This 52-minute video ($10) explains howintensive cover cropping serves as the base forcarefully planned rotations of many crops in theNordell’s whole-farm vegetable system. Booklet($10) also available (postpaid) from: Eric andAnne Nordell, Beech Grove Farm, 3410 Route184,Trout Run, Pa. 17771.

OTHER RESOURCES

Cover Crops On The WebTo keep up with the growing cover crop resources on the Internet’s World Wide Web, point yourbrowser to these sites:


This list is for information purposes only. Inclusion does notimply endorsement, nor is criticism implied of firms notmentioned.

Adams-Briscoe Seed Co. Inc. P.O. Box 19 325 E. Second St.Jackson, GA 30233-0019 770-775-7826 fax 770-775-7122 [email protected] http://www.abseed.comforage/grain legumes, grains, summer annuals,wildlife

Alabama Farmers Co-opP.O. Box 2227 Decatur,AL 35609 256-353-6843 fax 256-350-1770 small grains, forage/grain legumes, summerannuals (120 retail outlets)

Albert Lea Seedhouse Inc. P.O. Box 127 Albert Lea, MN 56007 800-352-5247 [email protected] http://www.alseed.com grains, forage/grain legumes, grasses

Albright Seed Company 487 Dawson Drive, Bay 5S Camarillo, CA 93012 805-484-0551 800-423-8112 fax 805-987-9021 [email protected] http://www.albrightseed.com legumes, grasses and grains adapted to California bioregions

Ampac Seed Co. P.O. Box 318 Tangent, OR 97389 800-547-3230 fax 541-928-2430 [email protected] http://ampacseed.com forage grasses, legumes

Barenbrug 33477 Highway 99 East Tangent, OR 97389 541-926-5801 800-547-4101 fax 541-926-9435 forage legumes, grasses

Birkett MillsP.O. Box 440 Penn Yan, NY 14527 315-536-3311fax 315-536-6740 buckwheat

Brett-Young Seeds Ltd. Box 99, St. Norbert Postal Station Winnipeg, MB, Canada R3V 1L5 204-261-7932 800-665-5015 (Canada) fax 204-275-7333 [email protected] forage legumes

Budd Seed191 Budd Blvd.Winston-Salem, NC 27114-5087800-543-7333336-760-9060 fax 336-765-3168 grasses, red clover, subclover

APPENDIX D

SEED SUPPLIERS

SEED SUPPLIERS 167

Cal/West Seeds Box 1428 Woodland, CA 95776-1428 800-327-3337 800-824-8585 fax 530-666-5317 whl: legumes, forages, clovers,Sudangrasses, vetches

Corland Seeds P.O. Box 336 Guelph, ON N1H 6K5 519-763-2059 800-265-4321 fax 519-763-5192 legumes, forages

DEKALB Genetics Corporation 3100 Sycamore Road DeKalb, IL 60115-9600 800-833-5252 [email protected] http://www.dekalb.com whl: sorghum-Sudangrass hybrids, forages

Discount Seed Inc. P.O. Box 842411 9th Ave SWWatertown, SD 57201 605-886-5888fax 605-886-3623 grains, forage/grain legumes, forage grasses

Ernst Conservation Seeds 9006 Mercer Pike RD 5 Box 806 Meadville, PA 16335 814-336-2404 fax 814-336-5191 [email protected] http://www.ernstseed.com forage legumes, native species, wildlife

Fedco Seeds P.O. Box 520 Waterville, ME 04903 207-873-7333 fax (same) grains, forage/grain legumes, brassicas

Fizzle Flat Farms—Marvin Manges 18773 E. 1600 Ave.Yale, IL 62481 618-793-2060 fax (same) buckwheat, hairy vetch, rye (some certifiedorganic)

Frazier Seed Co. 309 W. Main St.Anthony, KS 67003 316-842-5106 grains, cowpeas, winter peas

Harmony Farm Supply & Nursery P.O. Box 460 Graton, CA 95444 707-823-9125 fax 707-823-1734 forage/grain legumes

Hobbs and Hopkins Ltd. 1712 SE Ankeny Street Portland, OR 97214 503-239-7518 fax 503-230-0391 [email protected] grasses

Hytest Seeds454 Railroad Ave.P.O. Box 3147 Shiremanstown, PA 17011 717-737-4529 800-442-7391 fax 717-737-7168 grains, forage legumes, summer annuals


Johnny’s Selected Seeds Foss Hill Road Albion, ME 04910 207-437-9294 fax 207-437-2165 [email protected]://www.johnnyseeds.com grains, forage/grain legumes, rapeseed (some untreated)

Kamprath Seed Co. 205 Stockton St.Mateca, CA 95337 209-823-6242 800-325-4621 fax 209-823-2582 many medics, subclovers, clovers, grasses,other legumes

Kaufman Seeds P.O. Box 398Ashdown,AR 71822 870-898-3328 800-892-1082 wholesale (50-lb. min.): grains, forage/grainlegumes, grasses, summer annuals

Lohse Mill7752 County Road 29Glenn, CA 95943530-934-2157fax 530-934-9106grains, forage/dryland legumes

McDonald Ag Corp. P.O. Box 828 McMinville, OR 97128 503-472-5158 [email protected] crimson and red clover by cultivar

Minnesota Seed Solutions7800 State Highway 101 Shakopee, MN 55379 612-445-2606 wholesale (50-lb. min.): forgage/grain legumes,grains, grasses

Missouri Southern Seeds P.O. Box 699 Rolla, MO 65402 573-364-1336 800-844-1336 fax 573-364-5963 wholesale (w/retail outlets): grains, foragelegumes, grasses, summer annuals

North Country Organics P.O. Box 372 203 Depot St.Bradford,VT 05033 802-222-4277 fax 802-222-9661 forage legumes, summer annuals

Olds Seed Solutions2901 Packers Avenue Madison,WI 53704 608-249-9291 800-356-7333 fax 608-249-0695 forage legumes, brassicas, summer annuals,grasses

Peaceful Valley Farm Supply P.O. Box 2209 Grass Valley, CA 95945 916-272-4769 fax 530-272-4794 http://www.groworganic.com grains, grasses, forage/grain legumes, brassicas,sunn hemp

Pennington Seeds P.O. Box 290 Madison, GA 30650 [email protected] http://www.penningtonseed.com grains, grasses, forage legumes

SEED SUPPLIERS 169

Pick Seed CanadaP.O. Box 304 1 Greenfield RdLindsey, ON K9V 4S3905-623-2660fax 705-878-9249clovers, grasses

P.L. Rohrer & Bro. Co. P.O. Box 250 Smoketown, PA 17576 717-299-2571 fax 717-299-5347 grains, grasses, forage legumes, brassicas

Rupp Seeds, Inc. 17919 Co. Rd. B Wauseon, OH 43567 419-337-1841 fax 419-337-5491 grains, grasses, forage legumes

Seedway Inc. P.O. Box 250 Hall, NY 14463 800-836-3710 fax 716-526-6832Grains, forage/grain legumes, grasses, brassicas,summer annuals

Seimer/Mangelsdorf Seed Co. 96300 Collinsville Rd.East St. Louis, IL 62201 800-467-7333 fax 618-271-4199grains, cowpeas, summer annuals, wildlife

Southern States Cooperative 2600 Durham St.Richmond,VA 23220 800-868-6273 wholesale (retail outlets in 6 states): grains,forage legumes, cowpeas, summer annuals

Sweeney Seed Company 110 South Washington St.Mount Pleasant, MI 48858 517-773-5391 800-344-2482 fax 517-773-1216 forage legumes, peas, summer annuals, rape

Tennessee Farmers Co-op 200 Waldron Road P.O. Box 3003 LaVergne,TN 37086 615-793-8506 grains, forage legumes, peas

Timeless Seeds P.O. Box 881 Conrad, MT 59425 406-278-5770 fax 406-278-5720 [email protected] dryland forage/grain legumes

The Wax Co., Inc.204 Front St. N Amory, MS 38821 662-256-3511 annual ryegrass

Welter Seed and Honey Co. 17724 Hwy. 136 Onslow, IA 52321-7549 319-485-2762 800-728-8450 800-470-3325 grains, grasses, forage/grain legumes,summer annuals

Wolf River Valley Seeds N2976 County M White Lake,WI 54491 715-882-3100 800-359-2480 [email protected] grains, forage/grain legumes


INOCULANT SUPPLIERS LiphaTech Inc. (Nitragin inoculants) 3101 W. Custer Ave.Milwaukee,WI 53209 414-462-7600 800-558-1003 fax 414-462-7186 [email protected] http://www.liphatech.com inoculants for major/minor temperate,tropical climate legumes

Urbana Laboratories P.O. Box 1393 310 S.Third St.St. Joseph, MO 64502 816-233-3446 800-892-2013 fax 816-233-8295 [email protected] inoculants for major/minor temperate climate legumes

APPENDIX E

FARMING ORGANIZATIONS WITH COVER CROP EXPERTISE

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 cropping.

ORGANIZATIONS—NORTHEAST The Accokeek Foundation 3400 Bryan Point Road Accokeek, MD 20607 301-283-2113 fax 301-283-2049 [email protected] http://www.accokeek.org land stewardship and ecological agricultureusing CC

Center for Sustainable Agriculture590 Main St.Burlington,VT 05405802-656-5459fax [email protected]://www.uvm.edu/~susagctr

Chesapeake Wildlife Heritage P.O. Box 1745 Easton, MD 21601 410-822-5100 fax 410-822-4016 [email protected]://www.cheswildlife.org CC 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 419 114 W. Main St Millheim, PA 16854 814-349-9856 fax 814-349-9840 [email protected]://www.pasafarming.orgon farm CC demonstrations

ORGANIZATIONS 171

SARE Northeast Region Office University of Vermont 10 Hills Building Burlington,VT 05405-0082 802-656-0471 fax 802-656-4656 [email protected] http://www.uvm.edu/~nesare/index.html

ORGANIZATIONS—NORTH CENTRAL Center for Integrated Agricultural Systems(CIAS) University of Wisconsin-Madison 1450 Linden Drive Madison,WI 53706-1562 608-262-5200 fax 608-265-3020 [email protected] http://www.wisc.edu/cias/ CC resource locator in Wisconsin/ Upper Midwest

Conservation Technology InformationCenter (CTIC) 1220 Potter Drive, Rm 170 West Lafayette, IN 47906 765-494-9555 fax 765-494-5969 [email protected] http://www.ctic.purdue.educonservation tillage series fact sheets provider

Land Stewardship Project 2200 4th Street White Bear Lake, MN 55110 612-653-0618 fax 612-653-0589 [email protected] http://www.misa.umn.edu/~lsp/

Leopold Center for Sustainable Agriculture Iowa State University 209 Curtiss Hall Ames, IA 50011-1050 515-294-3711 fax 515-294-9696 [email protected] http://www.ag.iastate.edu/centers/leopoldsupport research, demos, education projects inIowa on CC systems

SARE North Central Region Office University of Nebraska-Lincoln 13-A Activities Bldg.P.O. Box 830840Lincoln, NE 68583 402-472-7081 fax 402-0280 [email protected] http://www.sare.org/ncrsare/

ORGANIZATIONS—SOUTH Appropriate Technology Transfer for RuralAreas (ATTRA) P.O. Box 3657 Fayetteville,AR 72702 1-800-346-9140 http://www.attra.org/ ATTRA is a leading information source forfarmers and extension agents thinking aboutsustainable farming practices

Educational Concerns for HungerOrganization ECHO 17430 Durrance Rd.North Ft. Myers, FL 33917 941-543-3246 fax 941-543-5317 [email protected]://www.echonet.org/ provides technical information and seeds oftropical cover crops


The Kerr Center for Sustainable Agriculture Inc. PO Box 588 Highway 271 South Poteau, OK 74953 918-647-9123 fax 918-647-8712 http://www.kerrcenter.com/ CC systems demonstrations & research

SARE Southern Region Office University of Georgia 1109 Experiment Street Georgia StationGriffin, GA 30223-1797 770-412-4787 fax 770-412-4789 [email protected] http://www.griffin.peachnet.edu/sare/

Texas Organic Growers Association P.O. Box 15211 Austin,TX 787611-877-326-5175 fax 512-842-1293 [email protected]://www.texasorganicgrowers.com/TOGA is helping to make organic agricultureviable in Texas and offers a quarterly periodical.

ORGANIZATIONS—WEST Center for Agroecology & Sustainable FoodSystems 1156 High StreetSanta Cruz, CA 95064 831-459-4367 fax 831-459-2799 http://zzyx.ucsc.edu/casfs/ facilitates the transfer of successful organicfarming and technical advice

Northern Plains Sustainable Agriculture Society 9824 79th St S.E.Fullerton, ND 58441-9725 701-883-4304 fax 701-883-4304 [email protected]://www.npsas.orgCC systems for small grains

SARE Western Region OfficeUtah State University 4865 Old Main Hill Room 322 Logan, UT 84322 435-797-2257 [email protected] http://wsare.usu.edu/

Small Farm Center University of California One Shields Avenue Davis, CA 95616 530-752-8136 fax 530-752-7716 [email protected] http://www.sfc.ucdavis.edu/ serves as a clearinghouse for questions fromfarmers, marketers, farm advisors, trade associa-tions, government officials and agencies, and theacademic community

University of California SAREP One Shields Avenue Davis, CA 95616-8716 530-752-7556 fax 530-754-8550 [email protected] http://www.sarep.ucdavis.edu/

REGIONAL EXPERTS 173

These 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: CC denotes cover crop(s) or cover cropping.

NORTHEASTAref A.Abdul-Baki USDA/ARS Vegetable Lab BARC-West Bldg. 010A Rm 213 10300 Baltimore Ave Beltsville, MD 20705 301-504-5057 fax 301-504-5555 [email protected] CC systems for vegetables, soil permeation & fer-tility

C.E. Beste 27664 Nanticoke Rd.Salisbury, MD 21801 410-742-8780 fax 410-742-1922 [email protected] CC systems & no-till equipment for vegetables

Andy Clark-SAN Coordinator Sustainable Agriculture Network National Agricultural Library 10301 Baltimore Ave Rm. 304 Beltsville, MD 20705 301-504-6425 fax 301-504-6409 [email protected] http://www.sare.org technical information specialist for sustainableagriculture; legume/grass CC mixtures

Jim Crawford New Morning Farm HCR 71, Box 168B Hustontown, PA 17229 814-448-3904 fax 814-448-2333 25 years of CC in vegetable production systems

Mark Davis USDA/ARS Soil Microbial SystemsBARC-West Bldg. 001, Rm 137 Beltsville, MD 20705-2350 301-504-9068 x342fax 301-504-8370 [email protected] CC for organic cropping systems

A. Morris Decker 5102 Paducah Rd.College Park, MD 20740 301-441-2367 Prof. Emeritus, University of Maryland. 40 yearsforage mgt., CC & agronomic cropping systemsresearch

Steve Groff Cedar Meadow Farm 679 Hilldale Rd.Holtwood, PA 17532 717-284-5152 fax 717-284-5967 [email protected] http://www.cedarmeadowfarm.com CC/no-till strategies for vegetable & agronomic crops

APPENDIX F

REGIONAL EXPERTS


H.G. Haskell4317 S. Creek Rd.Chadds Ford, PA 19317 tel/fax 610-388-0656 rye/vetch mix for green manure and erosioncontrol

Zane R. Helsel, Director of Extension Rutgers Cooperative Extension Rutgers,The State University of NJ88 Lipman Dr.New Brunswick, NJ 08901-8525 732-932-5000 x581 fax 732-932-6633 [email protected] http://www.rce.rutgers.edu CC for field crop systems

Stephen Herbert University of Massachusetts Dept. of Plant & Soil Sciences Bowditch Hall, Box 30910 Amherst, MA 01003 413-545-2250 fax 413-545-0260 [email protected] CC culture, soil fertility, crop nutrition & nitrateleaching

Bob Hofstetter Indian Rock Produce530 California RoadQuakertown, PA 18951215-538-1328CC for inter-seeding and over-seeding in field &vegetable crops

Dr. Amadou Makhtar Diop Information Coordinator The Rodale Institute 611 Siegfriedale Rd.Kutztown, PA 19530 610-683-1400 fax 610-683-8548 [email protected] http://www. rodaleinstitute.org333 acre farm & demonstration garden w/ CC;contact info and publications provider

Jack Meisinger USDA/ARS BARC-West Bldg. 007 Rm 205 10300 Baltimore Ave Beltsville, MD 20705 301-504-5276 [email protected] nitrogen management in CC systems

Anne and Eric Nordell 3410 Route 184 Trout Run, PA 17771 570-634-3197 rotational CC for weed control

Marianne Sarrantonio University of Maine 102 Deering Hall Orono, ME 04469 207-581-2913 fax 207-581-2999 [email protected] legumes, soil health & nitrogen cycling

Eric Sideman Maine Organic Farmers & Gardeners Assoc.P.O. Box 170 Common Ground County FairUnity, ME 04988 207-568-4142 fax 207-568-4141 [email protected]://www.mofga.org/MOFGA offers information & technical bulletinson CC selection & growth

John Teasdale USDA/ARS BARC-West Bldg. 001 Rm 323 10300 Baltimore Ave Beltsville, MD 20705 301-504-5504 fax 301-504-6491 [email protected] mgt./mixtures & weed suppression


David W. Wolfe Cornell University 168 Plant Science Bldg.Ithaca, NY 14853 607-255-7888 fax 607-255-9998 [email protected] CC for improved soil quality in vegetablecropping systems

NORTH-CENTRAL Dan Anderson University of Illinois Agroecology/SustainableAgriculture Program W-503 Turner Hall 1102 S. Goodwin Urbana, IL 61801 217-333-1588 fax 217-333-7370 [email protected] on-farm CC trials throughout Illinois

Rich Bennett RR 5 7 740 P3 Napoleon, OH 43545 419-748-8187 CC for soil quality & herbicide/pesticide reduc-tion

John Cardina Ohio State University-OARDC215 Williams Hall Wooster, OH 44691 330-263-3644 [email protected] CC for sustainable weed control

Stephan A. Ebelhar Dixon Springs Agricultural Center Route 1, Box 256 Simpson, IL 62985 618-695-2790 fax 618-695-2492 [email protected] CC systems for no-till corn & soybeans

Greg Endres Carrington Research Extension Center NDSU-CREC Box 219 Carrington, ND 58421 701-652-2951 x108fax 701-652-2055 [email protected] cropping systems & weed mgt. in the Dakotas

Rick Exner Practical Farmers of Iowa ISU Extension Service 2104 Agronomy Hall Ames, IA 50011 515-294-5486 fax 515-294-9985 [email protected] http://www.pfi.iastate.eduon farm CC research for the upper Midwest

Carmen M. Fernholz State Chair of the SFA of MN Rt. 2 Box 9A Madison, MN 56256 320-598-3010 fax 320-598-7347 [email protected]

Robert N. Fogg Fogg Organic Farms 2665 Bellevue Rd.Leslie, MI 49251 517-589-5590 fax 517-589-5596 CC for soil improvement in a closed organicsystem

Dr. Mohammadreza GhaffarzadehResearch ManagerAgronomy ServicesPioneer Hi-Bred International6900 NW 62nd Ave.Johnston, Iowa [email protected] sustainable cropping systems using berseemclover


Walter Goldstein or Jim Stute Michael Fields Agricultural Institute W2493 County ES East Troy,WI 53120 262-642-3303 fax 262-642-4028 [email protected] CC for nutrient cycling & soil health in biody-namic & conventional systems

Richard R. Harwood Michigan State University Crop & Soil Sciences Dept.260 Plant & Soil Sciences Bldg.East Lansing, MI 48824 517-432-1611 fax 517-353-3834 [email protected] CC systems & field crop agroecology

Frederick Kirschenman Rt 1 Box 73 Winsor, ND 58424 701-763-6287 fax 701-486-3580 CC systems for cereal grains, soil quality & pest mgt.

Matt Liebman Iowa State University Department of Agronomy 3218 Agronomy Hall Ames, IA 50011 [email protected] manures & CC for field and vegetablesystems

Dale Mutch W.K. Kellogg Biological Station District IPM Agent 3700 E. Gull Lake Dr.Hickory Corners, MI 49060-9505 616-671-2412 fax 616-671-4485 [email protected] http://www.msue.msu.edu/sycamore/cover.htm general CC information provider

Rob Myers Jefferson Institute 601 West Nifong Blvd, Suite 1D Columbia, MO 65203 573-449-3518 fax [email protected] CC systems and crop diversification

Michael Rahe Bureau of Land and Water ResourcesIllinois Dept. of Agriculture P.O. Box 19281 Springfield, IL 62794-9281 217-782-6297fax 217-524-4882 [email protected] CC information for referrals, research & projects

David R. Swaim Swaim & Associates Agronomic Consulting 1730 Camp Rotary Road Crawfordsville, IN 47933 765-362-4946 fax 765-361-9096 [email protected] CC with conservation tillage, soil fertility & cropnutrition

Richard Thompson Thompson On-Farm Research 2035 190th St.Boone, IA 50036-7423 515-432-1560 CC system in corn-soybean-corn-oats-hay rotation

SOUTH Philip J. Bauer USDA/ARS Cotton Production Research Center 2611 Lucas St.Florence, SC 29501-1241843-669-5203 x7250fax 843-662-3110 [email protected] CC systems for cotton production


Bob Burdette Southern Seed Certification Assoc.P.O. Box 2619 Auburn,AL 36831 334-821-7400 or 334-844-4995 specialty CC & seed development

Nancy Creamer North Carolina State University Horticultural Science Dept.Box 7609 Raleigh, NC 27695 919-515-9447 fax 919-515-2505 [email protected] CC systems for no-till vegetables & weed control

Seth Dabney USDA/ARS National Sedimentation Lab P.O. Box 1157 Oxford, MS 38655 662-232-2975 fax 662-232-2915 [email protected] legume reseeding & mechanical control of CC inthe mid-South

Phillip Davis Route 1 Box 208 Old Fort, NC 28762 tel/fax 828-668-9800 CC for corn, soybeans & tobacco

Mario DeLuca McDowell County Extension Service County Administration Bldg., Rm 226 Marion, NC 28752 828-652-7121 ext. 249 fax 828-659-3484 [email protected] http://mcdowell.ces.state.nc.us/staff/mdeluca/personalold.html CC information for corn and soybean production mgt.

Greg D. Hoyt MHCREC 2016 Fanning Bridge Rd.Fletcher, NC 28732 828-684-3562 [email protected] CC for vegetables, tobacco & corn

Noah N. Ranells North Carolina State University 1114A Williams HallBox 7620Raleigh, NC 27695-7620 919-515-7597 fax 919-515-5885 [email protected] grass/legume CC for improved water quality

D. Wayne Reeves USDA/ARS National Soil Dynamics Laboratory 411 S. Donahue St.Auburn,AL 36832-5806 [email protected] 334-844-4666 fax 334-887-8597

K.H. Quesenberry University of FloridaP.O. Box 110500 Gainesville, FL 32611 352-392-1811 fax [email protected] CC systems in Florida

Jac Varco Mississippi State University Plant & Soil Sciences Dept. Box 9555 Mississippi State, MS 39762 662-325-2737 fax 662-325-8742 [email protected] CC & fertilizer mgt. in no-till cotton productionsystems


Michael G. Wagger North Carolina State University Dept. of Soil Science P.O. Box 7619Raleigh, NC 27695-7619 919-515-4269 fax 919-515-2167 [email protected] nutrient cycling in CC based production systems

WESTMiguel A. Altieri University of California at Berkeley 215 Mulford Hall Berkeley, CA 94720-3112 510-642-9802 fax 510-642-7428 [email protected] http://nature.berkeley.edu/~agroeco3 CC to enhance biological pest control in peren-nial systems

Robert Bugg University of California at Davis 159 DANR BuildingDavis, CA 95616 530-754-8549 fax 530-754-8550 [email protected] CC selection, growth & IPM

David Chaney-SAREP EducationCoordinator University of California One Shields AvenueDavis, CA 95616-8716 [email protected] 530-754-8551 fax 530-754-8550

Ron Delaney University of Wyoming Dept. of Plant SciencesP.O. Box 3354 Laramie,WY 82071-3354 307-766-3103 fax 307-766-5549 [email protected] semi-arid annual legumes

Richard Dick Oregon State University Dept. of Crop & Soil Science Ag and Life Sciences, Bldg 3067Corvallis, OR 97331 541-737-5718 fax 541-737-5725 [email protected] nitrogen cycling & environmental applications ofCC systems

Charlotte Eberlein University of Idaho Twin Falls Research and Ext. Center 317 Falls AvenueTwin Falls, ID 83303-1827 208-736-3600 fax 208-397-4311 [email protected] CC for weed control in potatoes

Chuck Ingels UC Cooperative Extension 4145 Branch Center Rd.Sacramento, CA 95827-3898 916-875-6913 fax 916-875-6233 [email protected] farm advisor-pomology, viticulture,& environmental horticulture


Shiou Kuo Washington State University Research & Extension Center 7612 Pioneer Way East Puyallup,WA 98371 253-445-4573 fax 253-445-4621 [email protected] CC effects on soil, water quality and cropproductivity

John M. Luna Oregon State University Dept. of Horticulture 4143 Agricultural and Life Sciences Bldg.Corvallis, OR 97331 541-737-5430 fax 541-737-3479 [email protected] CC for integrated vegetable production systems& agroecology

Nancy Matheson 3845 Hart Lane Helena, MT 59602 406-227-9161 406-227-0389 [email protected]

Dwain Meyer North Dakota State University Loftsgard Hall, Room 470EExtension Service Fargo, ND 58105 701-231-8154 [email protected] yellow blossom sweet clover specialist

Clara I. Nicholls University of CaliforniaDepartment of Environmental Science Policy and ManagementDivision of Insect EcologyBerkeley, CA 94704510-642-9802fax 510-642-7428 [email protected] for biological control in vineyard systems

James R. Sims 21 Border Lane Bozeman, MT 59715 tel/fax 406-582-1576 dryland & alternate cropping systems

Fred Thomas CERUS Consulting 766 E.Avenue,#CChico, CA 95926530-891-6958fax 530-891-5248 [email protected] CC systems specialist for all agricultural crops


The publications cited in the text (in parentheses) are listedhere by reference number.

1 Abdul-Baki,Aref A. and John R.Teasdale. 1993.Ano-tillage tomato production system using hairyvetch and subterranean clover mulches.HortSci. 28:106-108.

2 Abdul-Baki,Aref and John R.Teasdale. 1997.Sustainable Production of Fresh-MarketTomatoes and Other Summer Vegetables withOrganic Mulches. Farmers’ Bulletin No. 2279,USDA/ARS, Beltsville, Md. 23 pp.

3 Alger, Jess. 1997. Personal communication.Stanford, Mont.

4 American Forage and Grassland CouncilNational Fact Sheet Series. Subterranean clover.http://forages.orst.edu/main.cfm?PageID=33

5 Anderson, Glenn. 1997. Personalcommunication. Hilmar, Calif.

6 Angers, D.A. 1992. Changes in soil aggregationand organic carbon under corn and alfalfa. SoilSci. Soc.Am. J. 56:1244-1249.

7 Appropriate Technology Transfer for RuralAreas (ATTRA). 1991 Cover Crops and GreenManures. ATTRA. Fayetteville,Ark.

8 Arshad, M.A. and K.S. Gill. 1996. Crop produc-tion, weed growth and soil properties underthree fallow and tillage systems. J. Sustain.Ag.8:65-81.

9 Badaruddin, M. and D.W. Meyer. 1989.Water useby legumes and its effects on soil water status.Crop Sci. 29:1212-1216.

10 Badaruddin, M. and D.W. Meyer. 1990. Green-manure legume effects on soil nitrogen, grainyield, and nitrogen nutrition of wheat.Crop Sci. 30:819-825.

11 Bagegni,Ali. M. et al. 1994. Herbicides withcrop competition replace endophytic tall fescue(Festuca arundinacae). Weed Tech. 8:689-695.

12 Ball, Donald M. and Robert A. Burdett. 1977.Alabama Planting Guide for Forage Grasses.Alabama Cooperative Extension Service, ChartANR 149.Auburn Univ.,Auburn,Ala.

13 Ball, Donald M. and Robert A. Burdett. 1977.Alabama Planting Guide for Forage Legumes.Alabama Cooperative Extension Service, ChartANR 150.Auburn Univ.,Auburn,Ala.

14 Barker, Kenneth R. 1996.Animal waste, wintercover crops and biological antagonists forsustained management of Columbia lance andother nematodes on cotton. pp. 19-20. SouthernRegion 1996 Annual Report. Griffin, Ga.

15 Barnes, Robert F. et al. 1995. Forages:TheScience of Grassland Agriculture. 5th Edition.Iowa State Univ. Press,Ames, Iowa.

16 Bauer, P.J. et al. 1993. Cotton yield and fiberquality response to green manures and nitrogen.Agron. J. 85:1019-1023.

17 Bauer, P.J. 1997. Personal communication.USDA-ARS. Florence, S.C.

18 Beale, P. et al. 1985. Balansa Clover—a NewClover-Scorch-Tolerant Species. South AustraliaDept. of Ag. Fact Sheet.

19 Beste, C. Edward. 1997. Personalcommunication. Univ. of Maryland-Eastern Shore,Salisbury, Md.

APPENDIX G

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20 Bird, George. 1997. Personal communication.Michigan State Univ. East Lansing, Mich.

21 Bloodworth, L.H. and J.R. Johnson. 1995.Cover crops and tillage effects on cotton. J. Prod.Ag. 8:107-112.

22 Bollich, P.K. 1997. Personal communication.Louisiana State Univ.. Crowley, La.

23 Boquet, D.J. and S.M. Dabney. 1991. Reseeding,biomass, and nitrogen content of selected winterlegumes in grain sorghum culture. Agron. J.83:144-148.

24 Bowman, Greg. 1997. Steel in the Field:AFarmer’s Guide to Weed Management Tools.USDA-Sustainable Agriculture Network (SAN).Burlington,Vt.

25 Bradley, John. 1997. Personal communication.Monsanto Crop Protection. Collierville,Tenn.

26 Bradow, Judith M. and William J. Connick Jr.1990.Volatile seed germination inhibitors fromplant residues. J. Chem. Ecol. 16:645-666.

27 Bradow, Judith M. 1993. Inhibitions of cottonseedling growth by volatile ketones emitted bycover crop residues. J. Chem. Ecol. 19:1085-1108.

28 Brady, Nyle C. 1990. The Nature andProperties of Soils. Macmillan Pub. Co., N.Y.

29 Brandt, J.E., F.M. Hons and V.A. Haby. 1989.Effects of subterraneum clover interseeding ongrain yield, yield components, and nitrogencontent of soft red winter wheat. J. Prod.Agric.2:347-351.

30 Brinsfield, R. and K. Staver. 1991. Role of covercrops in reduction of cropland nonpoint sourcepollution. Final Report to USDA-SCS, CooperativeAgreement #25087.

31 Brinton,Will. Medics, general. Univ. of Calif.SAREP Cover Crops Resource Page.http://www.sarep.ucdavis.edu/ccrop/

32 Bruce, R.R, P.F. Hendrix and G.W. Langdale.1991. Role of cover crops in recovery and main-tenance of soil productivity. pp.109-114. In W.L.Hargrove (ed.), Cover Crops for Clean Water.Soiland Water Conservation Society.Ankeny, Iowa.

33 Bruce, R.R. et al. 1992. Soil surfacemodification by biomass inputs affecting rainfallinfiltration. Soil Sci. Soc.Am. J. 56:1614-1620.

34 Brunson, K.E. 1991.Winter cover crops in the integrated pest management of sustainablecantaloupe production. M.S.Thesis. Univ. ofGeorgia,Athens, Ga.

35 Brunson, K.E. and S.C. Phatak. 1990.Wintercover crops in low-input vegetable production.HortSci. 25:1158.

36 Brunson, K.E., S.C. Phatak, L.D. Chandler andR.B. Chalfant. 1992.Winter cover crops influenceinsect populations in sustainable cantaloupeproduction. HortSci. 26:769.

37 Brutlag,Alan. 1997. Personal communication.Wendell, Minn.

38 Bugg, R.L. et al. 1990.Tarnished plant bug(hemiptera: Miridae) on selected cool-seasonleguminous cover crops. J. Entomol.Sci. 25:463-474.

39 Bugg, R.L. et al. 1991. Cool season cover cropsrelay intercropped with cantaloupe: Influence ofa generalist predator, Geocoris punctipes. J. Econ.Entomol. 84:408-416.

40 Bugg, R.L. 1991. Cover crops and control ofarthropod pests of agriculture. pp. 157-163. InCover Crops for Clean Water (W.L. Hargrove,ed.). Proc. Int’l Conf.April 9-11, 1991.WestTennessee Experiment Station, Jackson,Tenn. Soiland Water Conservation Society.Ankeny, Iowa.

41 Bugg, R.L. 1992. Using cover crops to managearthropods on truck farms. HortSci. 27:741- 745.


42 Bugg, Robert L. and Carol Waddington. 1994.Using cover crops to manage arthropod pests oforchards:A review. Ag., Ecosystems & Env. 50:11-28.

43 Bugg, Robert L. 1995. Cover biology: a mini-review. SAREP Sustainable Agriculture-TechnicalReviews. 7:4. Univ. of California, Davis, Calif.

44 Bugg, Robert L. et al. 1996. Comparison of 32cover crops in an organic vineyard on the northcoast of California. Biol.Ag. and Hort. 13:63-81.

44.1 Bugg, Robert L., Robert J. Zomer and Jill S.Auburn. 1996. Cover crop profiles: One-pagesummaries describing 33 cover crops. In CoverCrops: Resources for Education and Extension(Chaney, David and Ann D. Mayse, eds). Univ. ofCalifornia Sustainable Agriculture Research andEducation Program (SAREP). Univ. of Calif.,Division of Agriculture and Natural Resources,Davis, Calif.

45 Bugg, Robert L. and Mark Van Horn. 1997.Ecological soil management and soil fauna: Bestpractices in California vineyards.AustralianSociety for Viticulture and Oenology, Inc.Proc.Viticulture Seminar, Mildura,Victoria,Australia.

46 Burgos, Nilda R. and Ronald E.Talbert. 1996.Weed control by spring cover crops andimazethapyr in no-till southern pea (Vignaunguiculata). Weed Tech. 10:893-899.

47 Buntin, G.D., J.N.All, D.V. McCracken and W.L.Hargrove. 1994. Cover crop and nitrogen fertilityeffects on southern corn rootworm (Coleoptera:Chrysomelidae) damage in corn. J. Econ.Entomol. 87:1683-1688.

48 Butler, Lorna Michael. 1996. Fall-planted covercrops in western Washington:A model for sus-tainability assessment. Project Report #SW94-008.Western Region SARE. Logan, Utah.

49 Campbell, C.A. et al. 1993. Influence oflegumes and fertilization of deep distribution ofavailable phosphorus in a thin black cher-nozemic soil. Can. Jour. Soil. Sci. 73:555-565.

50 Campbell, C.A. et al. 1993. Spring wheat yieldtrends as influenced by fertilizer and legumes.J. Prod.Ag. 6:564-568.

51 Canadian Organic Growers Inc.1992.Organic Field Crop Handbook.Anne Macey (ed.).Canadian Organic Growers Inc.,Ottawa,Ont.

52 Cardina, John. 1997. Personal communication.Ohio State Univ.Wooster, Ohio.

53 Cash, Dennis, Jim Sims, Howard Bowman andBruce Smith. 1995. Growing Peas in Montana.Montguide MT 9520. Montana State Univ.Extension Service. Bozeman, Mont.

54 Cathey, H. M. 1990. USDA Plant HardinessZone Map. USDA-ARS Misc. Pub. No. 1475.

55 Chaney, David and D. Mays. March 1997.Cover Crops: Resources for Education andExtension. UC SAREP, Division of Agriculture andNatural Resources, Davis Calif.

56 Chen, J., G.W. Bird. and R.L. Mather. 1995.Impact of multi-year cropping regimes onSolanum tuberosum tuber yields in thepresence of Pratylenchus penetrans andVerticillium dahliae. J. Nematol. 27:654-660.

57 Choi, B.H. et al. 1991.Acid amide, dinitroani-line, triazine, urea herbicide treatment andsurvival rate of coarse grain crop seedlings.Research Reports of the Rural DevelopmentAdministration, Upland and Industrial Crops3:33-42.

58 Christensen, Peter. 1997. Personal communi-cation. Univ. of California. Davis, Calif.

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59 Clark,A.J. 1993. Managing hairy vetch/cerealrye cover crop mixtures for nitrogen and waterin no-till corn. Ph.D. dissertation, Univ. ofMaryland, College Park. Diss.Abstract 9407617.

60 Clark,Andy. 1997. Personal communication.Sustainable Agriculture Network. USDA- SARE.Beltsville, Md.

61 Clark,A. J. et al. 1994. Seeding rate and killdate effects on hairy vetch-cereal rye cover cropmixtures for corn production. Agron. J. 86:1065-1070.

62 Clark,A.J. et al. 1995. Hairy vetch kill dateeffects on soil water and corn production.Agron. J. 87:579-585.

63 Clark,A.J. et al. 1997a. Kill date of vetch, ryeand a vetch-rye mixture: I. Cover crop and cornnitrogen. Agron. J. 89:427-434.

64 Clark,A.J. et al. 1997b. Kill date of vetch, ryeand a vetch-rye mixture: II. Soil moisture andcorn yield. Agron. J. 89:434-441.

65 Cooke,L.1996.New Red Clover Puts Pasturesin the Pink.USDA/ARS.44:12 Washington,D.C.

66 Costa, Jose. 1997. Personal communication.Univ. of Md. College Park, Md.

67 Costello, Michael J. 1994. Broccoli growth,yield and level of aphid infestation inleguminous living mulches. Biol.Ag. and Hort.10:207-222.

68 Crawford and Nankivell. Medics, general. Univ.of Calif. SAREP Cover Crops Resource Page.http://www.sarep.ucdavis.edu/ccrop/

69 Creamer, Nancy G. 1997. Personal communi-cation. North Carolina State Univ.. Raleigh, N.C.

70 Creamer, Nancy G. et al. 1995.A method formechanically killing cover crops to optimizeweed suppression. Amer. J.Alt.Ag. 10:157-162.

71 Creamer, Nancy G., Mark A. Bennett, BenjaminR. Stinner and John Cardina. 1996.A comparisonof four processing tomato production systemsdiffering in cover crop and chemical inputs.J.Amer. Soc. Hort. Sci. 121:559-568.

72 Creamer, N.G., B. Plassman, M.A. Bennett, R.K.Wood, B.R. Stinner and J. Cardina. 1995.A methodfor mechanically killing cover crops to optimizeweed suppression. Amer. J.Alt.Ag. 10:157-161.

73 Cunfer, Barry M. 1996. Disease and insectmanagement using new crop rotations forsustainable production of row crops in theSouthern U.S. pp. 15-16. Southern Region 1996Annual Report. Griffin, Ga.

74 Cruse, R.M. 1995. Potential economic, envi-ronmental benefits of narrow strip intercrop-ping. Leopold Center Progress Reports 4:14-19.

75 Dabney, Seth. 1996. Cover crop integrationinto conservation production systems. pp. 13-14.Southern Region 1996 Annual Report.Griffin, Ga.

76 Dabney, S. M. 1995. Cover crops in reducedtillage systems. Proc. Beltwide CottonConferences. pp. 126-127. 5 Jan 1995. NationalCotton Council, Memphis,Tenn.

77 Dabney, Seth. 1997. Personal communication.USDA/ARS. Oxford, Miss.

78 Dabney, S.M. and J.L. Griffin. 1987. Efficacy ofburn down herbicides on winter legume covercrops. pp. 122-125. In Power, J.F. (ed.) The Role ofLegumes in Conservation Tillage Systems. Soiland Water Conservation Society.Ankeny, Iowa.

79 Dabney, Seth et al. 1991. Mechanical controlof legume cover crops. pp. 146-147. In CoverCrops for Clean Water (W.L. Hargrove, ed.).Proc. Int’l Conf.April 9-11, 1991.West TennesseeExperiment Station, Jackson,Tenn. Soil and WaterConservation Society.Ankeny, Iowa.


80 Davis, D.W. 1997. Personal communication.Univ. of Minnesota. St. Paul, Minn.

81 Davis, D.W., et al. 1990. Cowpea. InAlternative Field Crops Manual. Univ. of Wisc-Ext. and Univ. of Minnesota. Madison,Wis.and St. Paul, Minn.

82 Decker,A.M. 1997. Personal communication.Univ. of Maryland. College Park, Md.

83 Decker,A.M.,A.J. Clark, J.J. Meisinger, F.R.Mulford and M.S. McIntosh. 1994. Legume covercrop contributions to no-tillage corn production.Agron. J. 86:126-136.

84 Decker,A.M.,A.J. Clark, J.J. Meisinger, F.R.Mulford and V.A. Bandel. 1992. Winter AnnualCover Crops for Maryland Corn ProductionSystems.Agronomy Mimeo 34. Univ. of Md.Cooperative Ext. Service, Md. Inst. for Ag. andNatural Resources, College Park, Md.

85 DeGregorio, R. et al. 1995. Bigflower vetchand rye vs. rye alone as a cover crop for no-tillsweetcorn. J. Sustain.Ag. 5:7-18.

86 DeWilde, R. 1997. Personal communication.Viroqua,Wis.

87 Dick, Richard. 1997. Personal communication.Oregon State Univ.. Corvallis, Ore.

88 Diver, Steve. 1997. Personal communication.Appropriate Technology Transfer for Rural Areas(ATTRA). Fayetteville,Ark.

89 Doll, Jerry. 1991. Cited in Shirley, C.D. No-tillbeans: rye not?! The New Farm. 13:12-15.

90 Doll, J. and T. Bauer. 1991. Rye: more than amulch for weed control. pp. 146-149. IllinoisAgricultural Pesticides Conference presentationsummaries. Urbana, Ill.

91 Duke, James A. 1981. Handbook of Legumesof World Economic Importance. Plenum Press,N.Y.

92 Earhart, D.R. 1996. Managing soil phosphorusaccumulation from poultry litter applicationthrough vegetable/legume rotations. ProjectReport #LS95-69. pp. 33-34. Southern Region1996 Annual Report. Griffin, Ga.

93 Eberlein, Charlotte. 1995. Development ofwinter wheat cover crop systems for weedcontrol in potatoes. Project Report #LW91-27.Western Region SARE. Logan, Utah.

94 Eckert, D.J. 1991. Chemical attributes of soilssubjected to no-till cropping with rye covercrops. Soil Sci. Soc.Am. J. 55:405-409.

95 Edwards,W.M. et al. 1993.Tillage studies witha corn-soybean rotation: Hydrology and sedimentloss. Soil Sci. Soc.Am. J. 57:1051-1055.

96 Einhellig, F.A. and J.A. Rasmussen. 1989. Priorcropping with grain sorghum inhibits weeds.J. Chem. Ecol. 15:951-960.

97 Einhellig, F.A. and I.F. Souze. 1992.Allelopathicactivity of sorgoleone. J. Chem. Ecol. 18:1-11.

98 Enache,A.J., R.D. Ilnicki and R.R.Helberg.1992. Subterranean clover living mulch:A system approach. pp. 160-162. In Proc. FirstInt’l Weed Control Congress, Vol. 2. February 17- 21, 1992.Weed Science Society of Victoria,Melbourne,Australia.

99 Enache,A.J. 1990.Weed control by subter-ranean clover (Trifolium subterraneum L.) usedas a living mulch. Dissertation Abstracts Int., Sci.and Eng., 1990, 50(11):4825B.

100 Fairbrother,T.E. 1991. Effect of fluctuatingtemperatures and humidity on the softening rateof hard seed of subterranean clover (Trifoliumsubterraneum L.). Seed Sci.Tech. 19:93-105.

101 Fairbrother,T.E. 1997. Softening and loss ofsubterranean clover hard seed under sod andbare ground environments. Crop. Sci. 37:839-844.

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102 Fernholz, Carmen. 1997. Personal communi-cation. Madison, Minn.

103 Finch Univ. of Calif. Medics, general.SAREP Cover Crops Resource Page.http://www.sarep.ucdavis.edu/ccrop/

104 Fisk, J.W. and O.B. Hesterman. 1996. Ncontribution by annual legume cover crops forno-till corn. In 1996 Cover Crops SymposiumProceedings. Michigan State Univ.,W.K. KelloggBiological Station, Battle Creek, Mich.

105 Fischer,Albert and Larry Burrill. 1993.Managing interference in sweet corn-whiteclover living mulch system. Am. J.Alt.Ag. 8:51-56.

106 Fisk, J.W. 1997. Personal communication.Michigan State Univ.. East Lansing, Mich.

107 Flexner. 1990. Hairy vetch. Univ. of Calif.SAREP Cover Crops Resource Page.http://www.sarep.ucdavis.edu/ccrop/

108 Folorunso, Olatunji et al. 1992. Cover cropslower soil surface strength, may improve soilpermeability. Calif.Ag. 46:26-27.

109 Forney, D. Raymond and Chester L. Foy.1984. Phytotoxicity of products from rhizos-pheres of a sorghum-sudangrass hybrid. WeedSci. 33:597-604.

110 Forney, D. Raymond et al. 1985.Weedsuppression in no-till alfalfa (Medicago sativa)by prior cropping of summer-annual foragegrasses. Weed Sci. 33:490-497.

111 Fortin, M.C. and A.S. Hamill. 1994. Ryeresidue geometry for faster corn development.Agron. J. 86:238-243.

112 Foster, R.K. 1990. Effect of tillage implementand date of sweetclover incorporation onavailable soil N and succeeding spring wheatyields. Can. J. Plant Sci. 70:269-277.

113 Fox, R.H. and W.P. Piekielek. 1988. FertilizerN equivalence of alfalfa, birdsfoot trefoil, and redclover for succeeding corn crops. J. Prod.Agric.1:313-317.

114 Friedman, Diana et al.1996. Evaluation of fivecover crop species or mixes for nitrogen produc-tion and weed suppression in Sacramento Valleyfarming systems. Univ. of California Cover CropResearch and Education Summaries. 1994-1996. Davis, Calif.

115 Friesen, G.H. 1979.Weed interference in transplanted tomatoes (Lycopersiconesculentum).Weed Sci. 27:11-13.

116 Gardner, John ( ed.). 1992. Substitutinglegumes for fallow in U.S. Great Plains wheatproduction:The first five years of research anddemonstration 1988-1992. USDA/SARE andNorth Dakota State Univ., Michael FieldsAgricultural Institute, Kansas State Univ. andUniv. of Nebraska. NDSU Carrington ResearchExtension Center, Carrington, N.D.

117 Geneve, R.L. and L.A.Weston. 1988. Growthreduction of Eastern redbud (Cercis canadensisL.) seedlings caused by interaction with asorghum-Sudangrass hybrid (Sudax).J. Env. Hort. 6:24-26.

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119 Ghaffarzadeh, M. 1995. Considering annualclover? Don’t overlook berseem. Pub. #SA-7. 4pp. Sustainable Agriculutre Fact Sheet Series.TheLeopold Center,Ames, Iowa.

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121 Ghaffarzadeh, M. 1997.Annual legume makescomeback. pp. 24-25. Beef Today. January, 1997.

122 Ghaffarzadeh, M. 1997. Economic and biolog-ical benefits of intercropping berseem cloverwith oat in corn-soybean-oat rotations. J. Prod.Ag.10:314-319.

123 Ghaffarzadeh, M. 1995. Potential uses ofannual berseem clover in livestock production.Proc. Rotational Grazing, a conference spon-sored by The Leopold Center for SustainableAgriculture, Feb. 5-6, 1995. Published by IowaState Univ. Extension. See also Demonstration ofan annual forage crop integrated with crop andlivestock enterprises. In Progress Report. March1998.The Leopold Center for SustainableAgriculture 7:6-10.

124 Ghaffarzadeh, M. 1997. Personal communica-tion. Iowa State Univ.Ames, Iowa.

125 Goldstein,Walter. 1997. Personal communi-cation. Michael Fields Agricultural Institute.East Troy,Wis.

126 Granzow, Bill and Delores. 1997. Personalcommunication. Herington, Kan.

127 Graves,Walter L. et al. 1996. Berseem Clover:A Winter Annual Forage for CaliforniaAgriculture. Univ. of California, SAREP. Div. ofAgriculture and Natural Resources. Pub. 21536.Davis, Calif.

128 Green, B.J. and V.O. Biederbeck. 1995.Farm Facts: Soil Improvement with Legumes,Including Legumes in Crop Rotations.Canada-Saskatchewan Agreement on SoilConservation, Regina, SK.

129 Greene, D.K. et al.1992. Research report.New Crop News.Vol. 3. Purdue Univ.,WestLafayette, Ind.

130 Griffin, J.L. and S.M. Dabney. 1990. Preplant-postemergence herbicides for legume cover-cropcontrol in minimum tillage systems. Weed Tech.4:332-336.

131 Groff, Steve. 1997. Cedar Grove Farm.http://www.cedarmeadowfarm.com

132 Groff, Steve. 1997. Personal communication.Holtwood, Pa.

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134 Geunther, Paul. 1997. Personalcommunication. Dexter, Mich.

135 Guy, Stephen. 1997. Personalcommunication. Univ. of Idaho. Moscow, Idaho.

136 Hanson, J.C., E. Lichtenberg,A.M. Decker andA.J. Clark. 1993. Profitability of no-tillage cornfollowing a hairy vetch cover crop. J. Prod.Ag.6:432-436.

137 Hanson, James C. et al. 1997. Organic versus conventional grain production in the mid-Atlantic:An economic and farming systemoverview. Amer. J.Alt.Ag.12:2-9.

138 Harlow, Susan. 1994. Cover crops packplenty of value. Amer.Agriculturalist 191:14.

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143 Hermel, Rose. 1997. Forage Focus:Annuallegume makes comeback. pp. 24-25. Beef.January, 1997.

144 Hiltbold,A.E.1991.Nitrogen-fixing bacteriaessential for crimson clover.Alabama AgriculturalExperiment Station 38:13.Auburn,Ala.

145 Hoffman, Melinda L. et al. 1993.Weed andcorn responses to a hairy vetch cover crop.Weed Tech. 7:594-599.

146 Hoffman, Melinda L. et al. 1996. Interferencemechanisms between germinating seeds andbetween seedlings: Bioassays using cover cropand weed species. Seed Sci. 44:579-584.

147 Hofstetter, Bob. 1988. The New Farm’s covercrop guide: 53 legumes, grasses and legume-grass mixes you can use to save soil and money.The New Farm 10:17-22, 27-31.

148 Hofstetter, Bob. 1992. Bank on buckwheat.The New Farm 14:52-53.

149 Hofstetter, Bob. 1992. How sweet it is:Yellow-blossom sweetclover fights weeds, adds Nand feeds livestock. The New Farm 14:6-8.

150 Hofstetter, Bob. 1992. Reliable ryegrass. TheNew Farm 14:54-55, 62.

151 Hofstetter, Bob. 1993a. Meet the queen ofcover crops. The New Farm 15:37-41.

152 Hofstetter, Bob. 1993b. Fast and furious. TheNew Farm 15:21-23, 46.

153 Hofstetter, Bob. 1993c. Red clover revival.The New Farm 15:28-30.

154 Hofstetter, Bob. 1993d.A quick & easy covercrop. The New Farm 15:27-28.

155 Hofstetter, Bob. 1993e. Reconsider the lupin.The New Farm 15:48-51.

156 Hofstetter, Bob. 1994a.The carefree cover.The New Farm 16:22-23.

157 Hofstetter, Bob. 1994b. Bring on the medics!The New Farm 16:56, 62.

158 Hofstetter, Bob. 1994c.Warming up towinter peas. The New Farm 16:11-13.

159 Hofstetter, Bob. 1995. Keep your covers inthe pink. The New Farm 17:8-9.

160 Holderbaum, J.F. et al.1990. Fall-seededlegume cover crops for no-tillage corn in thehumid East. Agron. J. 82:117-125.

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162 House and Alzugaray. 1989. Hairy vetch.Univ. of Calif. SAREP Cover Crops Resource Page.http://www.sarep.ucdavis.edu/ccrop/

163 Howieson and Ewing. 1989. Medics, general.Univ. of Calif. SAREP Cover Crops Resource Page.http://www.sarep.ucdavis.edu/ccrop/

164 Hoyt, G.D. and W.L. Hargrove. 1986. Legumecover crops for improving crop and soilmanagement in the southern United States.HortSci. 21:397-402.

165 Illnicki, R.D. 1997. Personal communication.Rutgers Univ.. New Brunwick, N.J.


166 Ingels, Chuck A. et al. 1994. Selecting theright cover crop gives multiple benefits.Calif.Ag. 48:43-48.

167 Ingels, Chuck A. 1995. Cover cropping invineyards.Amer.Vineyard. 6/95, 8/95, 9/95, 10/95.In Chaney, David and Ann D. Mayse (eds.). 1997.Cover Crops: Resources for Education andExtension. Univ. of California, Div. of Agricultureand Natural Resources, Davis, Calif.

168 Ingels, Chuck A. 1997. Personalcommunication. Univ. of California. Davis, Calif.

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344 Theunissen, J, C.J.H. Booij and A.P. Lotz. 1995.Effects of intercropping white cabbage withclovers on pest infestation and yield. Ento-mologia Experimentalis et Applicata 74:7-16.

345 Thomas, Fred. 1997. Personal communica-tion. CERUS Consulting. Richvale, Calif.

346 Thompson, Dick. 1994. Personalcommunication. Boone, Iowa.

347 Timeless Seeds. 1997. Untitled price sheet.Conrad, Mont.

348 Townsend,Walt. 1994. No-tilling hairy vetchinto crop stubble and CRP acres. Project Report#FNC93-28. North Central Region SARE. Lincoln,Neb.

349 Tumlinson, J.H.,W.J. Lewis and L.E.M.Vet.1993. How parasitic wasps find their hosts.Sci.American 26:145-154.

350 Univ. of California Cover Crops WorkingGroup. March 1996. Cover Crop Research andEducation Summaries. Davis, Calif. 50 pp.

351 Univ. of California Sustainable AgricultureResearch and Education Program (UCSAREP)Cover Crops Resource Page online athttp://www.sarep.ucdavis.edu/ccrop/

BIBLIOGRAPHY 197

352 Varco, J.J., J.O. Sanford and J.E. Hairston. 1991.Yield and nitrogen content of legume covercrops grown in Mississippi. Research Report.Mississippi Agricultural and Forestry ExperimentStation 16:10.

353 Wagger, M.G. Personal communication. NorthCarolina State Univ. Raleigh, N.C.

354 Wander, M.M. et al. 1994. Organic andconventional management effects on biologicallyactive soil organic matter pools. Soil Sci. Soc.Am. J. 58:1120-1139.

355 Weaver, D.B. et al. 1995. Comparison of crop rotation and fallow for management ofHeterodera glycines and Meloidogyne spp. insoybean. J. Nematol. 27:585-591.

356 Welty, Leon et al. 1991. Effect of harvestmanagement and nurse crop on production of five small-seeded legumes. Montana AgResearch 8:11-14.

357 Weitkamp. 1988, 1989. Medics, general. Univ.of Calif. SAREP Cover Crops Resource Page.http://www.sarep.ucdavis.edu/ccrop/

358 Weitkamp and Graves. Medics, general. Univ.of Calif. SAREP Cover Crops Resource Page.http://www.sarep.ucdavis.edu/ccrop/

359 Westcott, M.P. et al.1991. Harvest manage-ment effects on yield and quality of small-seededlegumes in western Montana. MontanaAgResearch 8:18-21.

360 Westcott, M.P. 1995. Managing alfalfa andberseem clover for forage and plowdown nitro-gen in barley rotations. Agron. J. 87:1176-1181.

361 Weston, Leslie A. 1997. Personal communica-tion. Univ. of Kentucky. Lexington, Ky.

362 Weston, Leslie A., Chandrashekhar I. Nimbaland Philippe Jeandet. 1998.Allelopathic potentialof grain sorghum (Sorghum bicolor (L.)Moench) and related species. In Principles andPractices in Chemical Ecology. CRC Press, BocaRaton, Fla.

363 Weston, Leslie A. 1996. Utilization of allelopa-thy for weed management in agroecosystems.Agron. J. 88:860-866.

364 Wichman, David et al. 1991. Berseem cloverseeding rates and row spacings for Montana.Montana AgResearch 8:15-17.

365 Willard, C.J. 1927. An Experimental Study ofSweetclover. Ohio Agricultural Station BulletinNo. 405,Wooster, Ohio.

366 William, Ray. 1996. Influence of cover cropand non-crop vegetation on symphlan density invegetable production systems in the Pacific NW.Project Report #AW94-033.Western RegionSARE. Logan, Utah.

367 Williams et al. 1990. Ryegrass. Univ. of Calif.SAREP Cover Crops Resource Page.http://www.sarep.ucdavis.edu/ccrop/

368 Williams,William A. et al. 1991.Water-efficient clover fixes soil nitrogen, provideswinter forage crop. Calif.Ag. 45:30-32

369 Wingard, Charles. 1996. Cover Crops inIntegrated Vegetable Production Systems. ProjectReport #PG95-33. Southern Region 1996Annual Report. Griffin, Ga.

370 Wolfe, David. 1994. Management strategiesfor improved soil quality with emphasis on soilcompaction. Research project #LNE94-44.Northeast Region SARE. Burlington,Vt.

371 Wolfe, David. 1997. Soil Compaction: CropResponse and Remediation. Report No. 63.Cornell Univ., Department of Fruit and VegetableScience, Ithaca, N.Y.


APPENDIX H

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372 Wright, S.F. and A. Upadhaya. 1998.A surveyof soils for aggregate stability and glomalin, aglycoprotein produced by hyphae of arbuscularmycorrhizal fungi. Plant Soil 198:97-107.

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RESOURCES FROM SAN 199

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INDEX 201INDEX 201

AAlfalfa, 10, 42, 84, 88, 94Alkaloids, 60–61, 161Allelopathy

black oats, 159comparison of species,

45–46, 52–53hairy vetch, 113oats, 62, 64rye, 70sorghum-sudangrass hybrids,

81subterranean clovers, 136sweetclovers, 144woollypod vetch, 152, 154

Ammonia, 24Annuals. See also specific cover

cropsgrasses, 54legumes, 85–86uses, 54

Austrian winter peas. See Fieldpeas

Avena sativa. See OatsAvena strigosa. See Oats, black

BBacteria. See Disease manage-

ment and sources;Microorganisms

Barley, 58–61advantages and disadvan-

tages, 11, 52–53, 58–59crop systems, 41–42cultural traits, 50management, 59–61mixes of cover crops, 124,

145performance and roles,

48–49planting, 51, 59-61

Barrel medic. See MedicsBees, 149Bell beans, 148, 159

Beneficial insects. See Insectmanagement and sources

Biomass. See also Organicmatter; Residueberseem clover, 88, 90crimson clover, 100–101field peas, 105–106hairy vetch, 112legumes, 85medics, 126oats, 62sorghum-sudangrass hybrids,

81subterranean clovers, 132sweetclovers, 140

Birdsfoot trefoil, 131Blackeye peas. See CowpeasBlack medic. See MedicsBlack oats, 159Brassica campestris. See

RapeseedBrassica napus. See CanolaBrassicas

cash cropscover crop rotations for,

15, 37sweetclover overseeding,

146white clover, 150

cover cropserosion prevention, 11for nematode manage-

ment, 32for pest reduction, 10

Buckwheat, 54, 77–79advantages and disadvan-

tages, 52–53, 77–78comparative notes, 79cowpea mixtures, 98–99cropping systems, 37, 41, 42cultural traits, 50management, 78–79performance and roles,

48–49

for pest management, 31planting, 51, 78

Buffalo rolling stalk chopper,32–33

Burclover. See MedicsBur medic. See Medics

CCalcium, 19California. See WestCanadian field peas. See Field

peasCanola, 125Carbon to nitrogen ratio,

22–23, 54field peas, 110–111grasses, 54hairy vetch, 113, 114legumes, 86

Cereal grains. See Small grains;specific crops

Cereal rye. See RyeChoppers/chopping, 32–33, 91,

116, 129, 153–154. See alsoForage clover. See alsoSweetclovers; specific cloverspecies.vs. medics, 125mixtures, 135for orchards, 14reseeding, 13for weed management, 33

Clover, alsike clover, 131Clover, arrowleaf, 88Clover, balansa, 40, 158–159Clover, berseem, 87–94

advantages and disadvan-tages, 52–53, 87–88

comparative notes, 94crop systems, 34, 36, 89,

92–94cultural traits, 50inoculant, 92–93management, 89–91

INDEX


performance and roles,48–49

planting, 51, 88-90, 94Clover, crimson, 100–104


comparative notes, 104, 122,158

in crop rotations, 13, 35, 89,109–111

cultural traits, 50grazing, 88management, 101–104mixtures, 112, 113, 118, 135performance and roles,

48–49for pest management, 26–27,

30planting, 51, 101-104residue, 91

Clover, red, 127–131advantages and disadvan-

tages, 52–53, 127–128comparative notes, 131for corn>soybean systems,

34, 36, 73cultural traits, 50fertilizer cost reduction, 9–10management, 129–131performance and roles,

48–49planting, 51, 129, 131wheat nurse crop, 74

Clover, rose, 135Clover, subterranean, 132–138

advantages and disadvan-tages, 52–53, 132, 133–134

comparative notes, 138cultural traits, 50management, 134–138performance and roles,

48–49for pest management, 31planting, 51, 132-135, 138types and cultivars, 132–133

Clover, white, 147–151advantages and disadvan-

tages, 52–53, 147–148

comparative notes, 151cultural traits, 50management, 148–150for orchards, 14performance and roles, 13,

48–49planting, 51, 148-149types, 147for vegetable production, 37

Companion crops. See alsoNurse cropsannual ryegrass, 55–56berseem clover, 88, 91, 92–94cowpeas, 96crimson clover, 101oats, 63rye, 67sweetclover, 142white clover, 148

Conservation strips. See Stripcropping

Corn Belt. See MidwestCorn cropping systems

berseem clovers, 89, 92–93crimson clover, 89, 102fertilizer cost reduction, 9–10field peas, 111hairy vetch, 112–113,

115–116medic, 123–124planting time, 35red clover, 128, 129, 130, 131rotations, 34–36, 37–38, 41selecting cover crop, 14sorghum-sudangrass hybrids,

80subterranean clover, 133,

137–138sweetclovers, 145wheat, 72white clover, 148, 150woollypod vetch, 152

Costscomparison of species, 44,

49conventional vs. cover crop

systems, 27corn crop systems, 130

fertilizer cost reduction, 9–10field pea seeds, 106inoculant, 92lupins, 160medics, 124oat crops, 62pesticides, 10, 27, 114red clover, 127–128, 131seed, 45, 51, 156sunn hemp, 161sweetclovers, 140white clover, 149

Cotton crop systemscowpeas, 96crop rotations, 39–40field peas, 111hairy vetch, 117–118pest management, 26–27,

28, 29wheat, 74

Cover crops. See also specificcropsadvantages and disadvan-

tages for specific crops,45–46, 52–53

benefits, 9–11crop rotations, 34–42cultural traits, 44–45, 50performance and roles,

43–44, 48–49for pest management, 25–33planting recommendations,

45, 51promising species, 158–162regional species, 43, 47selection criteria, 12–15for soil fertility and tilth

development, 16–24testing on your farm,

156–158Cowpeas, 95–99


comparative notes, 99crop rotations, 72, 98–99cultural traits, 50management, 96–98mixtures, 82

INDEX 203

performance and roles,48–49

planting and seeds, 51, 96-97,99

for vegetable production, 38Crop residue. See ResidueCrop rotations. See also Crop

systemsberseem clover in, 92–94buckwheat in, 79corn-soybean systems, 34–36,

72–73for cotton production,

26–27, 39–40cowpeas in, 98–99crimson clover in, 102–103dryland cereal-legume sys-

tems, 40–42fertilizer application, 10field peas in, 106, 108–109foxtail millet in, 160hairy vetch in, 112–113legumes in, 85medics in, 121, 123–124pesticide and herbicide

reduction, 10planning, 12–15, 34red clover in, 128, 130rye in, 66sorghum-sudangrass hybrids

in, 83–84sunn hemp in, 161for vegetable production,

36–39winter wheat in, 72–73

Crop systems. See also Croprotationsberseem clover, 92–94cowpeas, 98–99field peas, 108–111hairy vetch, 117–118incorporating cover crops,

13sorghum-sudangrass hybrids,

83–84subterranean clovers,

137–138

sweetclovers, 145–146white clover, 149–150

Crotalaria juncea. See Sunnhemp

Crowder peas. See CowpeasCultivation

comparison of, 46, 52–53cowpeas, 98in disease management,

29–30field peas, 108hairy vetch, 116red clover, 129–130

DDairy farming, 14Damping off, 30Data collection for trials, 157Decomposition

carbon to nitrogen ratio,22–23

crimson clover, 103–104of grasses, 54microorganisms in, 17–18, 19

Denitrification, 24Disease management and

sourcesannual ryegrass, 57balansa clover, 158barley, 60, 61berseem clover, 91black oats, 159in corn-soybean system, 36cover crop benefits, 10, 27,

29–32cowpeas, 96, 97–98crimson clover, 103, 104field peas, 108hairy vetch, 117lupins, 161medics, 125oats, 64red clover, 130–131rye, 57–71sorghum-sudangrass hybrids,

81–83, 85species comparison, 45–46,

52–53

subterranean clovers, 136sunn hemp, 161sweetclover, 145vegetable production, 37wheat, 76white clover, 149, 150woollypod vetch, 154

Disking. See TillageDrought. See also Soil moisture

berseem clover, 90hairy vetch, 114sweetclovers, 140–14

Dryland productioncereal-legume crop rotations,

40–42cover crops, 11field peas, 106, 107, 108–109medics, 120, 125sweetclovers, 139–146, 144,

146Dry matter. See ResidueDutch white clover. See Clover,

white

EEconomics. See CostsEgyptian clover. See Clover,

berseemEragrostis tef. See TeffErosion prevention

annual ryegrass, 55barley, 58cover crops, 10–11, 16medics, 121mixtures, 86–87performance and roles of

species, 44, 48regional species comparison,

47rye, 66white clover, 149winter wheat, 72

Establishment. SeeSeeding/seeds, specific covercrops

Estrogen, 136


FFaba beans. See Bell beansFagopyrum esculentum.

See BuckwheatFallow

in dryland production, 40–42vs. grain legumes, 109vs. medics, 120selecting cover crops for,

12–13sweetclover rotations, 142,

144, 145Farmer accounts

Alger–perennial medic forsoil quality, fertility, 121

Anderson–woollypod vetchreseeding, 153; as frostprotectant and recognizingseedlings, 152

Bartolucci–establishingwoollypod vetch, 153

Bennett–rye for weed man-agement in soybeans, 67

Burkett–winter peas for dis-ease suppression, 108

Carter–wheat production, 74de Wilde–killing rye, 69; rye

for mulch, 70Erisman–timing rye kill, 69French–cowpeas in rotation,

98French–field peas, 110Granzow–sweetclovers for

grazing and green manure,142

Groff–incorporating rye seed68; killing rye, 69

Guenther–crimson-berseemclover with corn, 89

Kirschenmann–sweetcloverwith nurse crops, 145

LaRocca–barley in vineyardmix

Matthews–white clover incontour strips, 149

Mazour–managing sweet-clover escapes, 146

Moyer–no-till rye intostanding vetch

Nordell–early plowing toavoid slugs, 144; sweet-clover-clover mixes, 146;weed management in veg-etables, 38–39

Podoll–sweetclover weevilcycle, 144

Farming organizations, 170–172Fava beans. See Bell beansFeed supplements, 65Fertilizer

for fallow systems, 109red clover systems, 128, 130,

131reducing, 9–10, 93for subterranean clover, 136

Fescue, 81, 114, 115Field peas, 105–111


cropping systems, 34, 41cultural traits, 50for fertilizer reduction, 10for grazing and nitrogen, 110management, 107–111performance and roles,

48–49planting and seed, 51, 106-

108, 111Flail choppers for sorghum-

sudangrass hybrids, 82, 83Flail mowers. See

Mowers/mowingFlax, 42Forage

berseem clover, 88, 90, 91cowpeas, 96field peas, 106, 110hairy vetch, 119medics, 121, 126oats, 64–65red clover, 131rye, 71sorghum-sudangrass hybrids,

81subterranean clovers, 136

sweetclovers, 142, 146white clover, 148woollypod vetch, 155

Foxtail millet, 160Freedom to Farm Act, 98Frost damage, 152Frostseeding, 129, 143, 148–149Fruits. See also Orchards;

Vineyardsrye for, 66subterranean clovers, 134

GGerman millet. See Foxtail

milletGrain rye. See RyeGrains. See Small grains; specific

cropsGrasses

carbon to nitrogen ratio,23,54for fertilizer reduction, 10for moisture conservation, 11for nematode management,

32nitrate conservation, 18–19in soil health, 17, 18, 24subterranean clover

mixtures, 134Grass waterways, 57Grazing

annual ryegrass, 56, 57berseem clover, 88, 90in corn-soybean system, 41cowpeas, 96crimson clover, 104in dryland cereal-legume

systems, 42field peas, 106, 110, 111grass cover crops, 54hairy vetch, 119livestock poisoning, 81, 85,

139–140, 142lupins, 161medics, 121oats, 64–65performance and roles of

species, 44, 48rye, 71

INDEX 205

sorghum-sudangrass hybrids,85

subterranean clovers,134–135, 136

sweetclovers, 139–140, 141,142, 144, 146

wheat, 76Greenchopping berseem

clover, 91Green fallow systems, 145Green manures

berseem clover, 88, 89,90–91, 94

cowpeas, 95field peas, 106, 109oats, 63red clover, 127subterranean clovers, 133sweetclovers, 140, 142

Groundwater, 109

HHabitats. See Insect manage-

ment and sourcesHay

annual ryegrass, 57berseem clover/oats, 88in corn-soybean system, 41cowpeas, 96crimson clover, 104medic/grass mixtures,

124–125oats, 64–65sweetclovers, 141

Health and safety issues, 11Hemp, sunn, 161Herbicides

for annual ryegrass, 57for berseem clover, 91buckwheat sensitivity to, 79in corn production, 26–27in cotton production, 40cover crops for reducing, 10for cowpeas, 97crimson clover and, 101, 103for foxtail millet, 160for hairy vetch, 116

for medics, 121, 125for oilseed species, 145for red clover, 129–130for rye, 67, 70for sorghum-sudangrass

hybrids, 82for subterranean clovers,

135, 138for sweetclovers, 144for wheat and potatoes, 75for white clover, 150

High chopping woollypodvetch, 153–154

Hordeum vulgare. See BarleyHubam. See SweetcloversHumus. See Organic matter

IInoculants, 45, 51, 92–93, 149,

156, 158Insecticides, 26–27Insect management and

sourcesannual ryegrass, 57barley, 61bell beans, 159berseem clover, 91buckwheat, 78, 79cotton, 40cover crops for reducing, 10,

25–29, 30–31cowpeas, 95–96, 97, 104crimson clover, 101, 103field peas, 106hairy vetch, 117lupins, 161medics, 122oats, 64red clover, 128rye, 70sorghum-sudangrass hybrids,

82, 83species comparison, 45–46,

52–53subterranean clovers, 134sweetclovers, 141, 144–145wheat, 76white clover, 149, 150

woollypod vetch, 152Integrated Pest Management

(IPM), 28–29, 95–96Interseeding

barley, 60in corn-soybean system, 36,

41cowpeas, 96in dryland cereal-legume

crop rotations, 37legumes and cereal grains, 12medic, 89, 121performance and roles of

species, 44, 49subterranean clovers with

wheat, 137sweetclover and corn, 145in vegetable crop rotations,

37IPM. See Integrated Pest

ManagementIrrigation

barley, 60potatoes with wheat, 75subterranean clovers, 136for underseeding, 12woollypod vetch, 153, 154

Italian ryegrass. See Ryegrass,annual

KKilling and controlling, 57

annual ryegrass, 56–57barley, 60berseem clover, 91cowpeas, 97crimson clover, 103field peas, 108hairy vetch, 115–116medics, 124oats, 64red clover, 129–130rye, 69–70subterranean clovers, 135sweetclovers, 143–144white clover, 149winter wheat, 76


LLabor, 39Ladino clover. See Clover, whiteLana vetch. See Vetch,

woollypodLeaching, 11, 18–19. See also

Nitrogen management andsources

Legumes. See also specificcropsbenefits, 85–86carbon to nitrogen ratio, 23in crop rotations, 14, 37,

40–42, 108–111erosion prevention, 10–11humus production, 17mixtures, 62–63, 72–73mycorrhizae, 19nitrogen fixation and release,

9, 20–21, 92–93, 130, 148for pest management, 26–27,

33Lentils, 41Ley cropping subterranean

clovers, 136Ley system, medics for, 122, 124Livestock poisoning, 81, 85,

139–140, 142Living mulches

for soil improvement, 13for weed management, 33white clover, 148, 149–150

Lolium multiflorum. SeeRyegrass, annual

Lotus corniculatus. SeeBirdsfoot trefoil

Lupins, 160–161Lupinus albus. See LupinsLupinus angustifolius. See

Lupins

MMalting barley, 10Mammoth clover. See Clover,

redManagement.See specific

aspects of managementMedics, 119–126


comparative notes, 125, 138crop systems, 41, 89cultural traits, 50management, 123–125performance and roles,

48–49, 121planting and seeding, 51,

122-123, 125–126Medigo spp. See MedicsMedium red clover. See Clover,

redMelilotus alba. See

SweetcloversMelilotus officinalis. See

SweetcloversMicroorganisms

humus production, 17–18, 19nitrogen fixation, 20–21plant surface, 29–30rhizobium bacteria, 92–93

Mid-Atlanticcrimson clover, 103field pea crop systems, 108,

111hairy vetch, 112–113, 115,

116, 118rye, 66–71subterranean clovers, 133,

137–138sweetclovers, 146top species for, 47vegetable production, 37,

38–39weed management, 33winter wheat, 73

Midwestberseem clover, 89–90, 91,

92–94buckwheat, 79in corn-soybean system, 36cowpeas, 98crimson clover, 103field peas, 110hairy vetch crop systems,

113, 115medics, 120, 123–125

oats, 63red clover, 129–130, 130rye, 66, 69, 70sweetclovers, 141, 142top species for, 47winter wheat, 73

Millets, 131, 160Mixtures/mixed seeding. See

also Companion crops;Nurse cropsannual ryegrass, 56barley, 59–60benefits, 86–87berseem clover, 92–94carbon to nitrogen ratio, 23cowpeas, 98–99crimson clover, 103field peas, 105hairy vetch, 112, 113–114,

118medic, 124–125red clover, 128rye, 67, 68, 69sorghum-sudangrass hybrids,

82wheat, 74

Mow and blow system, 94Mowers/mowing

berseem clover, 90–91, 94buckwheat, 78cowpeas, 97fescue, 114flail

for berseem clover, 91for cowpeas, 97hairy vetch, 116

hairy vetch, 115–116insect management, 29medics, 121red clover, 129–130, 131rye, 69sicklebar

cowpeas, 96hairy vetch, 116sorghum-sudangrass

hybrids, 82, 83sorghum-sudangrass hybrids,

80–81, 82

INDEX 207

subterranean clovers, 133,137

sweetclovers, 143, 144, 146white clover, 149–150woollypod vetch, 153–154

Mucuna deeringiana. SeeVelvetbeans

Mulches. See also Livingmulcheshairy vetch, 117–118rye, 70–71sorghum-sudangrass hybrids,

82subterranean clovers, 133for weed management,

32–33woollypod vetch, 151–152

Mycorrhizae, 19, 140

NNematodes

annual ryegrass, 57balansa clover, 158barley, 60, 61berseem clover, 91black oats, 159cowpeas, 96, 97–98crimson clover, 104hairy vetch, 117management using cover

crops, 10, 27, 30–32oats, 64sorghum-sudangrass hybrids,

81, 85species comparison, 45–46,

52–53subterranean clovers, 136sunn hemp, 161sweetclover, 145

New Zealand white clover.See Clover, white

Nitrogen management andsourcesannual ryegrass, 55bell beans, 159berseem clover, 87–93calculating amount in cover

crop, 22–23

cover crop effect onconservation and leaching,

11, 18–19legume fixation and

release, 20–21organic matter, 17potential losses, 23–24regional species

comparison, 47species comparison, 43, 48in specific crops, 14–15tillage systems, 21–23

cowpeas, 95, 98crimson clover, 100, 101,

102, 103in crop rotations

corn-soybean system, 36dryland cereal-legume

systems, 42vegetable production, 38,

39field peas, 106, 109–111grasses, 54hairy vetch, 112–113, 115,

116legumes, 85–86lupins, 161medics, 120, 121, 124mixtures, 86oats, 62plant counts for estimation,

130red clover, 127, 129, 130, 131rye, 66, 67, 69sorghum-sudangrass hybrid

management, 83–84, 85subterranean clovers, 133,

136, 137, 138sweetclovers, 140, 143–144,

146wheat, 73white clover, 147–148, 148,

150winter wheat, 72woollypod vetch, 151–152,

152Nonlegumes. See also specific

crops

humus production, 17management, 54nitrogen, 18–19, 54uses, 54

Northeastbuckwheat, 79crimson clover, 102field pea crop systems, 108hairy vetch, 116oats, 63rye, 66sorghum-sudangrass hybrids,

80–81, 82, 83–84top species for, 47vegetable production, 37

Northern Plainsberseem clover, 91crimson clover, 102field pea crop systems, 106,

107, 108–109medics, 119–122subterranean clovers, 138sweetclovers, 143, 144, 145,

146Northwest. See Pacific

NorthwestNo-till systems. See also Tillage

cornwith hairy vetch, 9,

112–113selecting cover crop, 14with subterranean clover,

133cotton production, 40,

117–118cowpeas, 97crimson clover, 102, 103erosion prevention, 10–11hairy vetch, 114, 115–116,

117–118for insect management,

27–28nitrogen conservation, 18–24sorghum-sudangrass hybrids,

81, 82subterranean clovers, 136sweetclovers in grain

stubble, 143


vegetables, 15wheat, 74

Nurse cropsannual ryegrass, 55–56barley, 58–59berseem clover, 88buckwheat, 78medics, 123, 125mixtures, 87oats, 62–63rapeseed for sweetclover,

145wheat, 74

Nutrients. See Nitrogen;Phosphorus

OOats, 62–65


comparative notes, 61, 65crop systems, 36, 37, 113,

160cultural traits, 50fertilizer reduction, 9management, 63–65mixtures, 88, 89, 92–94, 143performance and roles,

48–49planting, 51, 63-64

Oats, black, 159Orchards

annual ryegrass, 55–57cowpeas, 96insect management, 28–29medics, 120mixtures for, 86selecting cover crop, 14subterranean clovers, 132,

133, 136, 137woollypod vetch, 154

Organic matterbarley, 58buckwheat, 77, 79components, 17medics, 120–121microorganisms and aggrega-

tion, 17–18, 19

rye, 66sorghum-sudangrass hybrids,

84wheat, 73woollypod vetch, 152

Overseeding. See Underseeding

PPacific Northwest

sorghum-sudangrass hybrids,83

species for, 47subterranean clovers, 136wheat with potatoes, 75

Pasture. See also Grazingin corn-soybean system, 41sorghum-sudangrass hybrids,

81Peanuts, 26–27, 29Pearl millet, 160Peas. See Cowpeas; Field peasPerennials. See also specific

cropsgrasses, 54legumes, 85nitrogen fixation, 92

Pest management. See Diseasemanagement and sources;Insect management and

sources;Weed management andsources

Phosphorusbuckwheat, 77–78, 79conservation by cover crops,

19crimson clover, 101hairy vetch, 114red clover leaching, 131sweetclovers, 140winter wheat, 72

Pisum sativum subsp. arvense.See Field peas

Plant counts for nitrogen esti-mation, 130

Planting. See Establishment;Seeding/seeds

Plastic mulches, 118Potassium, 19, 66, 72

Potatoes, 10, 30, 37, 75, 83–84Press-wheel drill, 141Profitability. See Costs

RRainfall. See Drought; Soil

moistureRapeseed, 85, 145Reseeding

balansa clover, 158barley, 60berseem clover, 88clovers, 13comparison of species, 45,

51in cotton crop rotations, 40crimson clover, 100, 103medics, 121–122, 126mixtures, 86subterranean clovers,

135–136, 137–138sweetclovers, 141woollypod vetch, 154

Residueberseem clover, 90, 91, 94buckwheat, 77in corn-soybean system, 35in cotton production, 40cowpeas, 98crimson clover, 103, 104field peas, 111grasses, 54performance and roles of

species, 44, 49sorghum-sudangrass hybrids,

82, 83, 85species comparison, 43, 48

Rhizobium bacteria, 92–93Rice, 137Rice straw, 59Rollers for berseem clover, 91Rolling stalk chopper, 32–33,

116, 129Rotations. See Crop rotationsRunoff reduction, 101Rye, 65–71


INDEX 209

comparative notes, 71crop systems, 34–36, 39, 40,

41, 160cultural traits, 50hairy vetch mixtures, 114,

115, 118management, 68–71nitrate conservation, 11,

18–19performance and roles,

48–49for pest management, 26–27,

30, 32, 70–71planting and seed, 51, 67-68,

71Ryegrass, annual, 55–57


cultural traits, 50management, 56–57vs. perennial, 57performance and roles,

48–49planting, 51, 56-57for vegetable production, 37

Ryegrass, perennial, 13, 57

SSafflower, 37–39Secale cereale. See RyeSeeding/seeds. See also

Interseeding; Reseeding;specific cover crops

Underseedingbalansa clover, 158bell beans, 159black oats, 159comparison of species, 51in corn>soybean system, 35foxtail millet, 160grasses, 54lupins, 160sunn hemp, 161teff, 161–162testing on your farm,

156–157Seed suppliers, 166–170Sesbania mixtures, 82

Setaria italica. See Foxtailmillet

Shading, 150Small grains. See also specific

cropsberseem clover as compan-

ion crop, 91for corn-soybean systems,

35–36, 41erosion prevention, 11fertilizer reduction, 10field pea mixtures, 105,

107–108humus production, 17interseeding, 12medics in rotation, 124overseeding with berseem

clover, 90red clover plantings, 129selecting cover crop for, 13,

14Small-seeded horse beans. See

Bell beansSnail medic. See MedicsSoil erosion. See Erosion

preventionSoil fertility and tilth. See also

Nitrogen management andsourcesannual ryegrass, 55barley, 58buckwheat, 78–79cover crops for improving,

10, 16–24crop rotations for, 13dryland cereal-legume

systems, 42hairy vetch, 113red clover, 128regional species comparison,

47rye, 71sorghum-sudangrass hybrids,

81, 84species comparison, 43, 48,

52–53subterranean clovers, 133sweetclovers, 140

vegetable production, 39wheat, 73, 74white clover, 148woollypod vetch, 152

Soil moisture. See also Drought;Dryland productionbarley, 60in corn-soybean systems, 35cover crops for conserving,

11cowpeas, 96, 98field peas, 106, 109, 111foxtail millet, 160hairy vetch, 114legumes, 145medics, 125mixtures, 86in nitrogen fixation, 21potatoes with wheat, 75rye killing and, 69subterranean clovers,

132–133, 136, 137sweetclovers, 146white clover, 148

Soil organisms, 24. See alsoMicroorganisms

Soil temperature, 21, 130Sorghum, 133, 136Sorghum-sudangrass hybrids,

80–85advantages and disadvan-

tages, 52–53, 80–81, 84comparative notes, 80, 84–85in corn-soybean system, 41cultural traits, 50management, 82–84performance and roles,

48–49planting and seed, 51, 82, 85for vegetable production, 37,

38Sorgoleone, 81South

berseem clover, 90, 91crimson clover, 101, 102, 103field pea crop systems, 108,

109–111, 111


hairy vetch crop systems,112, 115, 117–118, 122

rye, 66, 69subterranean clovers, 135,

136, 137top species for, 47weed management, 33

Southern peas. See CowpeasSouthern spotted bur medic.

See MedicsSoybeans

berseem clover for, 92–93cotton intercropping, 96crop rotations, 34–36, 41field pea overseeding, 111hairy vetch overseeding, 114medics in, 124nematode management, 32red clover for, 129, 130rye for, 66, 67wheat for, 72, 74, 75

Spring oats. See OatsSpring peas. See Field peasStraw, 59Strip cropping

annual ryegrass, 57berseem clover, 94in cotton production, 40cowpeas, 97rye, 66white clover, 150

Subclover. See Clover,subterranean

Subsoil looseners, 47, 52–53,80–81

Sudangrass, 83. See alsoSorghum–sudangrass hybrids

Sudax. See Sorghum-sudangrasshybrids

Sudex. See Sorghum-sudangrasshybrids

Sugarbeets, 10, 32, 59, 60Sunflowers, 145Sunn hemp, 161Sustainable Agriculture

Network, 198–199Sweetclovers, 139–146

advantages and disadvan-tages, 52–53, 139, 140–141

comparative notes, 146in crop rotation, 72cultural traits, 50management, 141–146performance and roles, 13,

48–49planting and seed, 51,

141-143, 145-146types, 139–140for vegetable production, 37,

38–39wheat nurse crop, 74

TTeff, 161–162Tillage. See also No-till systems

conservation tillagefor disease management,

30–31for insect management,

26–27conventional till

corn and subterraneanclover, 133

nitrogen conservation,18–24

organic matter accumula-tion, 18

cotton and peanuts, 26–27field peas, 108oats, 64reduced tillage for rye, 71ridge-till for medics in corn,

124rotary tillage for white

clover, 150sorghum-sudangrass hybrids,

82, 83strip-till

corn and peanuts, 26–27crimson clover, 102for insect management,

27–28rye, 70white clover, 150

sweetclovers, 142, 145–146

woollypod vetch, 153–154Trials on your farm, 156–158Trifolium alexandrinum. See

Clover, berseemTrifolium balansae. See Clover,

balansaTrifolium brachycalcycinum.

See Clover, subterraneanTrifolium incarnatum. See

Clover, crimsonTrifolium pratense. See Clover,

redTrifolium repens. See Clover,

whiteTrifolium subterraneum. See

Clover, subterraneanTrifolium yanninicum. See

Clover, subterraneanTriticum aestivum. See Wheat,

winter

UUndercutters, 32–33, 116, 135Underseeding

annual ryegrass, 56berseem clover, 89, 90, 94in corn-soybean system, 35crimson clover, 102in crop rotation, 12–13field peas, 111hairy vetch, 114medics, 123–124, 124–125,

126oats, 63red clover, 128, 129rye, 66sweetclovers, 142, 145, 146for weed management, 33wheat, 73white clover, 148

Universal Soil Loss Equation, 16

VVegetables

annual ryegrass for, 55–57berseem clover for, 91, 94in corn-soybean system, 41cowpeas for, 98

INDEX 211

crimson clover for, 102, 103crop rotations, 13, 36–39disease management, 30foxtail millet for, 160hairy vetch for, 116, 117, 118insect management, 27–29medics for, 125rye for, 66, 68, 70–71selecting cover crop, 15sorghum-sudangrass hybrids,

81, 83subterranean clovers for, 133,

134, 136, 137–138sweetclover overseeding, 146white clover for, 148,

149–150woollypod vetch for, 152

Velvetbeans, 99Vetch, 87, 159Vetch, bigflower, 70Vetch, cahaba white, 31Vetch, common, 37–39,

109–111, 155Vetch, hairy, 112–119


comparative notes, 155for corn-soybean systems,

34–36, 41, 72crop systems, 117–119cultural traits, 50fertilizer reduction, 9–10management, 114–117performance and roles,

48–49for pesticide reduction, 10planting and seed, 51,

114-119residue, 91rye mixtures, 68in small grain production, 14,

109–111strip cropping with wheat,

94for vegetable production, 39

Vetch, purple, 37–39, 155

Vetch, woollypod, 119, 151–155advantages and disadvan-

tages, 52–53, 151–152comparative notes, 155cultural traits, 50management, 152–155performance and roles,

48–49planting, 51, 151-155for vegetable production,

37–39Vicia dasycarpa. See Vetch,

woollypodVicia faba. See Bell beansVicia villosa. See Vetch, hairyVicia villosa ssp.dasycarpa.See

Vetch,woollypodVideo resources, 165Vigna unguiculata. See

CowpeasVineyards

annual ryegrass for, 55–57barley for, 59–60, 61buckwheat for, 79cowpeas for, 96medics for, 120sorghum-sudangrass hybrids,

84woollypod vetch for, 151,

153–154Virus. See Disease management

and sources

WWater quality, 11Weed management and sources

annual ryegrass, 55, 57barley, 58, 60–61berseem clover, 88black oats, 159buckwheat, 77cotton production, 40cover crops

management using, 27,32–33

performance and roles ofspecies, 44, 48

species comparison, 47,52–53

cowpeas, 95, 99foxtail millet, 160hairy vetch, 113medics, 120, 124oats, 62, 63, 64rye, 66–67, 70sorghum-sudangrass hybrids,

81, 82, 84, 85subterranean clovers, 133,

137–138sweetclovers, 146teff, 162vegetable production, 37,

38–39wheat, 73, 74–75white clover, 150woollypod vetch, 152, 154

Westbarley, 58berseem clover, 90buckwheat, 79cowpeas, 95–96field pea crop systems,

107–108hairy vetch, 112medics, 120, 123–124, 126subterranean clovers,

133–138top species for, 47vegetable crop systems,

37–39woollypod vetch, 151–155

Wheat, winter, 72–76advantages and disadvan-

tages, 52–53, 72–73berseem clover as

companion, 94crop rotations, 36, 41–42,

160cultural traits, 50management, 73–76medic plantings and, 120,

121, 124–125performance and roles,

48–49


for pest management, 30planting and seed, 51red clover plantings, 129, 130subterranean clover

interseeding, 137sweetclover rotations, 140,

142, 144for vegetable production, 37

White sweetclover. SeeSweetclovers

Winter rye. See Rye

YYellow mustard, 84Yellow sweetclover.

See SweetcloversYields

corn, 93cover crops in increasing, 10rye effect on, 67, 69

Farmers across the U.S. are using cover crops to smother weeds, deter pests andslow erosion.They find that cover crops help them cut costs and boost profitswhile 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 finddetailed information on how to select cover crops to fit your farm, and how to man-age them to reap multiple benefits.

Here is what the experts say. . .“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 thesatisfaction 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 dothe same for you.”Richard De Wilde, vegetable grower, Viroqua, Wis.

“Nowhere else can farmers and growers get the important detailed information theyneed to make their own decisions on integrating cover crops into crop rotations.Don’t forget to read the sidebars, which contain farmer experiences with covercrops.This really is a one-of-a-kind resource.”Noah Ranells, extension associate, North Carolina State University,Department of Crop Science

“This book will be a great resource for farmers, educators, researchers and anyonewho wants basic information and good ideas for how to use cover crops. I am partic-ularly impressed with the way information is supported by personal experiences offarmers and researchers.”John R.Teasdale, research scientist, USDA-ARS, Beltsville, Md.

Managing Cover Crops ProfitablySECOND EDITION

$19.00

A publication of the SustainableAgriculture Network with funding by theSustainable Agriculture Research andEducation program of the CSREES, U.S. Department of Agriculture


ISBN 1-888626-04-6

9 781888 626049

Managing Cover Crops Profitably SECOND

EDITION

HANDBOOKSERIES BOOK 3


Managing Cover Crops Profitably SECOND EDITION

Sustain

able

Agricu

lture N

etwo

rk



USDA Plant Hardiness Zone Map

Agricultural Research Service, USDA

Ecoregions of the United States

Source: Bailey, 1994

AVERAGE ANNUAL MINIMUM TEMPERATURE

Temperature (˚C) Zone Temperature (˚F)

-45.6 and Below 1 Below -50

-42.8 to -45.5 2a -45 to -50

-40.0 to -42.7 2b -40 to -45

-37.3 to -40.0 3a -35 to -40

-34.5 to -37.2 3b -30 to -35

-31.7 to -34.4 4a -25 to -30

-28.9 to -31.6 4b -20 to -25

-26.2 to -28.8 5a -15 to -20

-23.4 to -26.1 5b -10 to -15

-20.6 to -23.3 6a -5 to -10

-17.8 to -20.5 6b 0 to -5

-15.0 to -17.7 7a 5 to 0

-12.3 to -15.0 7b 10 to 5

-9.5 to -12.2 8a 15 to 10

-6.7 to -9.4 8b 20 to 15

-3.9 to -6.6 9a 25 to 20

-1.2 to -3.8 9b 30 to 25

1.6 to -1.1 10a 35 to 30

4.4 to 1.7 10b 40 to 35

4.5 and Above 11 40 and Above

DIVISIONSThe areas within each Division are Provinces.1. Tundra2. Subarctic3. Warm Continental4. Hot Continental5. Subtropical6. Marine7. Prairie8. Mediterranean9. Tropical/Subtropical Steppe10.Tropical/Subtropical Desert11.Temperate Steppe12.Temperate Desert13.Savanna14.Rainforest

Mountains with AltitudinalZonation

Source: R.G. Bailey (see p. 162).

managing cover crops profitably - usda · (san) published managing cover crops profitably in 1992,...

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