summer 2001 vol. 44, no. 3 · 2016. 1. 13. · kurt m. guidry, amos bechtel, steve hague, robert...

Louisiana Agriculture, Summer 2001 1

Summer 2001Vol. 44, No. 3

2 Louisiana Agriculture, Summer 2001

The mention of a pesticide or use of a trade name forany product is intended only as a report of researchand does not constitute an endorsement or recom-mendation by the Louisiana Agricultural ExperimentStation, nor does it imply that a mentioned productis superior to other products of a similar nature notmentioned. Uses of pesticides discussed here havenot necessarily been approved by governmental regu-latory agencies. Information on approved uses nor-mally appears on the manufacturer’s label.

Material herein may be used by the press, radio andother media provided the meaning is not changed.Please give credit to the author and to the publicationfor any material used.

ON THE COVER: Cows graze at the LSU AgCenter’s Southeast Research Station nearFranklinton. The facility includes about 190 cows with plans to increase to 220 with 200milking. See more on research at the station on page 18. Photo by John Wozniak.

Photo by John Wozniak

Florida Group Learns to CompostZoo ‘Doo’ at LSU AgCenter SchoolWhat to do with zoo doo-doo was the dilemma facing officials at the Panama City,

Fla., Zoo World until they found out about the LSU AgCenter’s Compost FacilityOperator Training School.

Now they have a plan to recycle the zoo waste into safe, useful and nearly odor-free compost. This plan involves working with two other groups in Panama City, a localhigh school and Tyndall Air Force Base. Both groups sent representatives to theweeklong school this past May.

“This is the first time we’ve had high school students at the compost school andthe first time we’ve worked with a zoo,” said Dr. Bill Carney, coordinator of the LSUAgCenter’s Callegari Environmental Center. He has been directing these workshops,which he puts on every spring and fall, since 1994.

Class size is limited to 25 because of the intensity of the activities. The participantslearn the chemistry of combining waste substances rich in nitrogen and carbon to buildand maintain compost piles, called windrows.

“I didn’t realize we’d be doing so much science,” said Andrea Colbert, 16, one ofthe high school students. All three of the students are juniors in an environmentalscience class. Their teacher Mike Sylvester could not attend because of his schedule.

Their high school, which includes about 1,200 students, has established severalbusinesses, called the “Phoenix Project,” as part of its curriculum. One business to berun by the environmental science classes is a composting facility.

Coincidentally, officials at Zoo World wanted to start composting the waste,which they now have to bury, and Tyndall had plans to set up a compost facility tohandle the waste generated by the 6,000 people who live there.

“The Air Force wants all the bases to set up composting facilities,” Carney said.“It’s just getting too expensive to haul off all that waste.”

The compost school is open to anyone wanting to learn composting on a largescale., Carney said. More information about the school can be obtained by contactingCarney at (225) 578-6998 or going to the LSU AgCenter’s website.

Linda Foster Benedict

Louisiana State University Agricultural CenterWilliam B. Richardson, Chancellor

Louisiana Agricultural Experiment StationWilliam H. Brown, Director

The Louisiana Agricultural Experiment Station providesequal opportunities in programs and employment.

The LSU AgCenter puts on a compost facility operator training school each spring and fall.The school is conducted at the Callegari Environmental Center, which just opened inDecember 2000. Students divide into groups and work with their own “windrows” ofwaste, learning how to turn it into safe, valuable and nearly odor-free compost.

EDITOR: Linda Foster Benedict

CONTRIBUTOR: Jane Honeycutt

PHOTO EDITOR: John Wozniak

DESIGNER: Barbara Groves Corns

Published quarterly by the LouisianaAgricultural Experiment Station,Louisiana State University AgriculturalCenter, Baton Rouge, Louisiana.Subscriptions are free. Send requestsand any comments or questions to:

Linda Foster Benedict, EditorLouisiana AgricultureP.O. Box 25100Baton Rouge, LA 70894-5100

phone (225) 578-2263fax (225) [email protected].

www.lsuagcenter.com

EDITORIAL BOARD:David J. Boethel (Chairman)Linda Foster BenedictPat BollichJames ChambersBarbara Groves CornsCaye DrapchoJane HoneycuttT. Eugene ReaganDavid Sanson


Volume 44, Number 3, Summer 2001

SCIENCE NOTES

CONTENTS

Research on bitter Panicum, at right,will be added as the coastal plantsproject develops. See page 4.

Photo by Michael D. Materne


4 Improving Native Plants to Protect and PreserveLouisiana’s Coastal MarshesStephen A. Harrison, Timothy P. Croughan, Michael D. Materne,Bradley C. Venuto, Gary A. Breitenbeck, Marc A. Cohn, Xiaobing Fang, Alicia Ryan, Raymond W. Schneider, R. Alan Shadow, Prasanta Subudhiand Herry Utomo

7 Enzyme Treatment of Catfish Feeds Can Reduce Environmental PhosphorusRobert C. Reigh and Weibing Yan

8 Preliminary Evaluation of Early-age Catfish Stocking to Enhance FingerlingProducers’ ProfitabilityC.R. “Chuck” Weirich and C. Greg Lutz

12 Benefits of Soil-applied Herbicides in Roundup Ready SoybeansJeffrey M. Ellis, James L. Griffin and Curtis A. Jones

14 Growing Leaf Lettuce in Louisiana’s Ornamentaland Vegetable GardensDrew Bates and Anthony Witcher

18 New Tool to Gauge Dairy HerdNutrition: Milk Urea NitrogenMichael E. McCormick, Angelica M. Chapa,J. Marcos Fernandez and James F. Beatty

21 Dairy Industry’s Contribution to Louisiana’sEconomy: More Than a Drop in the BucketRick Bogren

24 Llama Mamas Give Birth to AlpacasLinda Foster Benedict

25 Mapping and Interpreting Electrical Conductivity in Production FieldsSteven H. Moore and Maurice C. Wolcott

27 Scientists Taught Leadership SkillsLinda Foster Benedict

22 Profitability of Cotton Crop Rotation Systems in Northeast LouisianaKurt M. Guidry, Amos Bechtel, Steve Hague, Robert Hutchinson and Donald Boquet

16 Wheat Cover Crops: Benefits and ManagementBill J. Williams, Donald J. Boquet and Donnie K. Miller

10 Weed Control Using Roundup Ready, Liberty Link and Clearfield CornD. Alan Peters, Jason A. Bond, James L. Griffin and Jeffrey M. Ellis


Improving Native Plantsto Protect and PreserveLouisiana’s Coastal Marshes

Stephen A. Harrison,Timothy P. Croughan,Michael D. Materne,Bradley C. Venuto,Gary A. Breitenbeck,Marc A. Cohn,Xiaobing Fang,Alicia Ryan,Raymond W. Schneider,R. Alan Shadow,Prasanta Subudhiand Herry Utomo

Spartina research plots at Grand Terre.


Improving Native Plantsto Protect and PreserveLouisiana’s Coastal Marshes

Smooth cordgrassis widely used forerosion control.However, its use islimited by its highcost to plantmanually. The LSUAgCenter isworking with otheragencies to figureout a way to seedit efficiently viaairplane.

Smooth cordgrassis widely used forerosion control.However, its use islimited by its highcost to plantmanually. The LSUAgCenter isworking with otheragencies to figureout a way to seedit efficiently viaairplane.


T he improvement of native plantspecies for use in coastal protection andrestoration activities is the focus of amulti-disciplinary, cooperative effortinvolving scientists from the LSUAgCenter and the U.S. Department ofAgriculture’s Natural ResourcesConservation Service (NRCS).

Although biotechnology andclassical plant improvement methods arewell established in agricultural cropproduction, their use in environmentalremediation is still emerging. Scientistsfrom the NRCS Plant Materials Centerat Golden Meadow have collected,tested and released native plant materi-als with superior performance in coastalenvironments, including smoothcordgrass and black mangrove. Theobjective of the project is to develop aseed-based system of propagatingsmooth Spartina alterniflora, alsoknown as smooth cordgrass oroystergrass, over large areas and togenetically improve the performance ofnative plant species for use in coastalrestoration. This requires geneticimprovement of seed productioncapability while maintaining vigor anddisease resistance, and development of asystem to produce, store and plant theseeds.

Louisiana’s coastal marshes arehighly productive ecosystems. Smoothcordgrass is the predominant salt marshspecies along the Gulf Coast, and itprovides food and habitat for aquaticspecies. This plant and its decomposi-tion products provide the foundation ofthe food chain for such species as smallcrustaceans, shrimp, crabs, shellfish andminnows. These in turn support largerfish, aquatic birds and other wildlife.

Louisiana loses more than two acresof coastal wetlands every hour, about 30square miles each year, from naturalprocesses and human activities. Leveesystems protect low-lying regions fromflooding but deprive the coastal marshesof the sediment deposition necessary fortheir formation. The marsh naturallysubsides as organic matter decomposesand loose sediments compact. Channel-ing of the marshes to support petroleumand shipping activities has resulted inrapid and frequent mixing of salt andfresh water. Natural plant systems areunable to adapt to sudden changes fromfresh to saline water that result fromsubsidence, saltwater infiltrationthrough channels and other ecosystemdisturbances brought about by humanactivities. As a result, large areas ofproductive marsh have been lost.

The Coastal Wetlands Planning,Protection and Restoration Act of 1990(the Breaux Act) and other legislationhave provided impetus and substantialfunding for reclamation activities. Theseactivities include sediment diversionand rebuilding barrier islands anderoded areas using dredge material androcks. Revegetation of the eroded andnewly created marshland must be anintegral part of reclamation activities topreserve a natural ecosystem.

Spartina Ideal forReclamation

Spartina alterniflora is the pre-dominant marsh grass and tolerates awide range of salinity from slightlybrackish to seawater. It can readily beproduced in freshwater ponds. It is anideal species for coastal reclamationwork because of its stress tolerance andrapid growth. A single Spartinaalterniflora plant can grow to a clumpof several feet in diameter within a year.It thrives in coastal marshes andintertidal regions along the Gulf Coast.It spreads underground and its densecanopy provides a significant bufferagainst wave energy. It controls erosion,traps suspended sediments and producessignificant amounts of organic matter. Itgrows parallel to the shore in water upto 18 inches deep and in clumps on mudflats.

Smooth cordgrass is widely used forerosion control along shorelines andcanal banks and for stabilization ofloose soil on mud flats and dredge-fillsites. Its use is limited by the high cost

for plant material, up to $6 per plant,and the amount of labor required toplant it. Aerial seeding would permitplanting an acre in just a few seconds ata fraction of the cost of manual trans-planting.

One of the primary objectives ofthis research is to develop a seed-basedsystem of establishing vegetation inlarge reclaimed coastal areas. The needfor a seed-based system becameparticularly apparent with the largebrown marsh dieback that occurred in2000 and affected up to 390,000 acres ofsalt marsh. An estimated 17,000 acres ofdensely vegetated marsh were convertedto open mud flats in Louisiana.

Spartina Produces Few SeedsSpartina flowers in the late summer

and produces seed each year, but theseed quality and quantity are generallylow. Spartina seed must be stored under

Stephen A. Harrison, Professor, Department ofAgronomy; Timothy P. Croughan, Professor, RiceResearch Station, Crowley, La.; Michael D.Materne, Plant Materials Specialist, USDANational Resources Conservation Service; BradleyC. Venuto, Associate Professor, SoutheastResearch Station, Franklinton, La.; Gary A.Breitenbeck, Professor, Department of Agronomy;Marc A. Cohn, Professor, Department of PlantPathology and Crop Physiology; Xiaobing Fangand Alicia Ryan, Graduate Students, Departmentof Agronomy; Raymond W. Schneider, Professor,Department of Plant Pathology and CropPhysiology; R. Alan Shadow, Research Associate,and Prasanta K. Subudhi, Assistant Professor,Department of Agronomy; and Herry S. Utomo,Post-doctoral Research Associate, Rice ResearchStation, Crowley, La.

This is a healthy stand of Spartina.

Photos by Michael D. Materne


cool, wet conditions that mimicfalling into the marsh in the fall andremaining in a dormant state untilspring. Seed does not germinate at thetime of shattering, and seed that driesout rapidly loses viability. This majorobstacle to commercial seeding mustbe overcome.

An initial collection of nativesmooth cordgrass was made in 1998.Approximately 100 seed heads wereharvested from each of 126 sitesacross south Louisiana. Seed variedsignificantly in weight and germina-tion. Seedlings from 101 accessionswere planted at the NRCS PlantMaterials Center and under marshconditions in Lafourche and Cameronparishes to evaluate vegetative vigor,spread, pest resistance, adaptation andseed production. Forty selectedaccessions were planted in replicatedtrials at the LSU AgCenter Ben HurResearch Farm.

In the fall of 2000, 40 geneticallydistinct plants, representing eight ofthese accessions, were chosen basedon performance across two locations.These were transplanted to a pond atBen Hur and at Grand Terre, a barrierisland near Grand Isle, for additionalevaluation and use as parents in thebreeding program. The five bestaccessions from an earlier LSUAgCenter Rice Research Stationcollection, along with surviving plantscollected from brown marsh sites in2000, were added to this gene pool foruse in development of geneticallybroad-based synthetic populationswith superior performance.

The original Rice Research Stationaccessions have been evaluated exten-sively for vigor, adaptation and seedproduction. Five of these accessions arebeing vegetatively increased and one ofthese will probably be released in 2002to enhance genetic diversity of availableplant material. Vermilion, which wasreleased in 1989, is the only commer-cially available cultivar and is usedextensively in coastal wetland restora-tion projects.

Other Research ProjectsVermilion fingerprinting. Commer-

cial contracts for coastal revegetationprojects sometimes specify Vermilionsmooth cordgrass because of its vigor,wide adaptation and proven perfor-mance; however, there is no easy way todetermine if plants used to fulfill suchcontracts really are Vermilion. Twostudies have been undertaken to addressthis dilemma. The first study is todevelop genetic fingerprinting technol-ogy for rapid determination of thegenetic identity of plants supplied forreclamation efforts. The second studywill compare the performance ofvegetative clones of Vermilion to seed-propagated plants.

Smooth cordgrass diseases. Rapidand vigorous stand establishment isessential if large areas are to be reveg-etated. Numerous pathogens may affectplants at different growth stages,although most can be controlled withseed-applied fungicides. Other diseasesof mature plants may affect rate ofcolonization, biomass accumulation andseed production. These diseases will beassessed and varieties screened for

resistance to the most damagingdiseases.

Producing seed volume. A seed-based production system requires amethod of handling seed in largevolume and management practices foroptimum seed production. A study wasinitiated at Galliano in the spring of2001 to evaluate the effects of fertilizer,insecticide and fungicide application onseed production and quality in a fresh-water pond environment. In Spartina,the traditional seed treatment of chillingseeds stimulates the loss of dormancyand maintenance of seed viability. Thecritical moisture content and rate ofdrying necessary to maintain viabilityand break dormancy will be defined.Alternative dormancy-breaking treat-ments of short duration that are ame-nable to commercial application will beevaluated as replacements for moist-chilling and seed storage methods.

Other plants with promise. Al-though smooth cordgrass is the mainfocus of the coastal plant project,research is ongoing with several otherspecies to identify and improve the onesthat work well in the many differentniches within the coastal ecosystem.Black mangrove provides nesting sitesfor pelicans and is an important barrierisland species. Native Louisianaaccessions of black mangrove collectedby the NRCS are being evaluated.

Sea oats have extensive rootsystems and are excellent dune stabiliz-ers. In Florida, a thriving commercialsea oat industry produces plants fromseed for use in dune stabilization.However, the Florida accessions do notgrow well in Louisiana, and the nativeLouisiana sea oat is a poor seed pro-ducer. The native sea oat will behybridized with sea oats from theAtlantic Coast to increase seed produc-tion. Cultural practices for increasedseed production will be evaluatedbeginning in 2001. Research on bitterPanicum, marsh-hay cordgrass and otherspecies will be added as the coastalplants project develops.

Plants provide a self-sustaining,environmentally sound and aestheticallypleasing approach to controlling coastalerosion that can persist indefinitely.Commercial enterprises to supply marshplant material will expand as coastalreclamation activities increase over thenext decade. The coastal plants projectwill play an important role in develop-ing genetically superior varieties andimproved technology to protect ourvaluable coastal ecosystem. These are research plots at the NRCS Plant Materials Center at Golden Meadow.

Photo by Michael D. Materne


Phosphorus is a critical nutrient for plant growth in aquaticenvironments. Small increases in phosphorus entering a catfishpond can produce algal blooms that degrade water quality andincrease off-flavor in fish. The primary source of phosphorus incatfish ponds is feed. This could be reduced by lowering feedingrates, decreasing the amount of phosphorus in the feed orincreasing the absorption of dietary phosphorus by the fish.

However, each of these options has problems. Loweringfeeding rates is usually impractical because the high stockingdensities used by most catfish producers dictate high feedingrates for acceptable yields. Decreasing the amount of phospho-rus in feeds is difficult because of the high level of plant productsused in catfish diets. A typical catfish feed contains more than 90percent plant ingredients, primarily soybean meal and corn,which contain phosphorus in a chemical form (phytic acid)poorly digested by fish. Most of the chemically bound phospho-rus in feed ingredients passes through the gut unused and iseventually released into the pond by decomposition of fishwastes. Because so little of this phosphorus is used, inorganicphosphorus supplements are added to catfish feed to satisfydietary requirements.

Increasing the uptake of phosphorus from feed ingredientscan be accomplished by supplementing diets with phytase, anenzyme that breaks down phytic acid to release its boundphosphorus. Adding phytase to fish feeds has been shown toimprove phosphorus uptake in the few studies conducted todate and, in some cases, to increase use of dietary protein.Several studies have been conducted at the LSU AgCenter’sAquaculture Research Station to determine the effects ofsupplemental phytase on breakdown of phytic acid in catfish feedand to evaluate the effects of phytase supplementation on dietdigestibility and the use of dietary protein and minerals.

Laboratory feeding trials were conducted with an all-plantdiet containing graded levels of phytase (0, 500, 1,000, 2,000,4,000 and 8,000 units per kilogram). Results indicated thatweight gain, feed conversion, diet digestibility, protein availabilityand use of dietary protein were not improved by phytasetreatment, even at the highest level of phytase tested, but addingphytase to the diet at a level of 1,000 units or higher significantlyincreased the mineral content of bone—especially concentra-tions of calcium, phosphorus and manganese. Zinc, an essentialtrace mineral for catfish, was deposited at significantly higherconcentrations in bone of fish fed 8,000 units than in bone of fishfed 500 units or less.

Phytic acid was degraded by phytase, primarily in thestomach of catfish, within a few hours after ingestion. Two hoursafter feeding, stomach contents of fish fed phytase-supple-mented diets contained from 5 percent to 90 percent of theamount of phytic acid present in the diet, depending on theconcentration of phytase fed. By eight hours after feeding,concentrations of phytic acid in stomach contents of fish fed1,000 units per kilogram, or more, had fallen to 6 percent or lessof initial dietary levels. Phytic acid levels in digesta continued todecrease as the material moved through the intestine.

Results at this timesuggest that a phytase in-clusion level of 1,000 unitsper kilogram in the diet isadequate to significantlyincrease use of dietaryminerals and significantlyreduce the amount ofphytic acid in catfish waste.At this level, the require-ment for supplemental in-organic phosphorus is de-creased, and the quantityof phosphorus enteringthe pond environmentfrom feed ingredients isreduced significantly com-pared to fish fed anunsupplemented diet.

A problem with use of phytase in catfish feeds is theenzyme’s inability to withstand the high temperatures of extru-sion processing. Addition of phytase to floating feeds like thosecommonly used in commercial catfish production will requirethat methods be developed for applying the enzyme to finishedfeeds under practical milling conditions; for example, phytasemight be applied at the end of the manufacturing process as atop-spray on finished pellets.

Pond feeding trials also are needed to determine if theeffects of phytase that have been documented in laboratoryfeeding trials produce measurable benefits under practical pro-duction conditions.

Robert C. Reigh, Professor, and Weibing Yan, Research Associate,Aquaculture Research Station, LSU AgCenter, Baton Rouge, La.

An unobstructed pond, like this one at the Aquaculture ResearchStation, is desired by the catfish producer.

LSU AgCenter scientists are lookingat ways to reduce the amount ofphosphorus in catfish ponds andthus help eliminate problems withalgal blooms that can degradewater and increase off-flavor in fish.

Photo by Robert Reigh



Enzyme Treatment of Catfish FeedsCan Reduce Environmental Phosphorus

Enzyme Treatment of Catfish FeedsCan Reduce Environmental Phosphorus


Early-age Stocking of FryAlthough most fingerling producers hold and feed swim-up

fry in the hatchery for two to 10 days before stocking, severalLouisiana catfish fingerling producers stock their nursery pondswith sac fry, usually within two days after they are hatched. Thispractice was initiated in an attempt to reduce hatchery operating

expenses such as feed, labor and electric-ity. Although research has shown that frycan be stocked at the onset of yolk absorp-tion with no detrimental effects on subse-quent fingerling production, stocking sacfry has been reported to result in reducedsurvival rates and overall production. Tofurther investigate this topic, productiontrials were conducted at the LSUAgCenter’s Aquaculture Research Stationto determine the effect of stocking fry ofthree different ages on survival, weight,yield and feed conversion ratio.

Fingerling Production TrialsTwo fingerling production trials were

conducted over two growing seasons, 1998(Trial 1) and 1999 (Trial 2). Trials wereconducted under simulated nursery pondconditions using 12 earthen-bottom fiber-


Many Louisiana catfish farmers focus on producing market-ready fish and purchasefingerlings from other growers. Fingerlings are typically 4 to 6 inches long.

Catfish eggs as they appear under a microscope.


In Louisiana and other catfish-producing states, most grow-ers focus on the production of market-ready fish and purchasefingerling catfish to restock their production ponds from asmaller number of farmers who specialize in fingerling produc-tion. In Louisiana, fewer than 20 fingerling producers satisfy theannual seed stock requirements for the state’s catfish industry.Production of seed stock is one of the most critical phases of thecatfish production cycle.

Fingerling ProductionTo produce fingerling catfish, eggs are procured in the spring

from ponds containing adult broodstock and transported to ahatchery where they are incubated under controlled conditions.At hatching, baby catfish (fry) possess a yolk from which theyderive nourishment for the first four to five days of life and arecalled “sac fry.” After the yolk is absorbed, fry are called “swim-up fry” because they swim to the surface in search of food. Swim-up fry are typically held in the hatchery for up to 10 days and feda finely ground commercial diet before they are stocked intonursery ponds. After stocking, fry feed mainly on natural foodorganisms such as zooplankton and insect larvae. These foodsources normally become depleted within four to six weeksafter stocking, and fish are then fed formulated pelleted feedsuntil sufficient growth is obtained. At a common stocking rate of200,000 to 250,000 fry per surface acre, four to six months arerequired to produce fingerling catfish 4 to 6 inches long.

Preliminary Evaluation of Early-age Catfish Stockingto Enhance LouisianaFingerling Producers'Profitability


stocked at an age of 14 days after harvest. These findings suggestthat sac fry can be stocked with no detrimental effect onsubsequent fingerling production. Indeed, based on final weightat harvest, it may actually be beneficial to stock sac fry ratherthan to hold and feed fry in the hatchery before stocking. Sac frystocked in properly managed nursery ponds have unlimitedaccess to zooplankton and insect larvae, which comprise thebulk of the diet of recently stocked fry. Under hatchery condi-tions, feed is more restricted. Thus, fry stocked as sac fry maygain an initial size advantage over fry stocked at an older age,which may be retained over the course of production untilharvest. But because of the reduced mobility of sac fry relativeto older, larger fry, proper management procedures mustensure elimination of predators.

More Research RequiredAlthough results of this preliminary study suggest that the

practice of stocking sac fry may be an alternative to thetraditional procedure of holding and feeding fry under hatcheryconditions before stocking, experiments were conducted undersimulated conditions. In a typical production pond, there is lesscontrol of certain variables such as predator populations, waterquality parameters and disease organisms. Therefore, moreexperiments will be conducted in ponds at the AquacultureResearch Station and at two Louisiana catfish farms. Theseexperiments will include comprehensive cost and return infor-mation to determine the economic impact of early-age stockingof catfish fry before recommendations can be made to the state’scommercial catfish industry.

AcknowledgmentThis research was supported by the U.S. Department ofAgriculture and the Louisiana Catfish Promotion and ResearchBoard.

C.R. “Chuck” Weirich, Assistant Professor, and C. Greg Lutz, ExtensionSpecialist, Aquaculture Research Station, Baton Rouge, La.

Photo by German Poleo

glass pools (0.002 acre) for Trial 1 and 15 for Trial 2. Trial 1included four replicates per treatment (age of fry at stocking),and Trial 2 included five. Fry were stocked at two (sac fry), sevenor 14 days after hatching. Fry stocked at seven and 14 days afterhatching were fed in the hatchery for two and ninedays, respectively, before they were stocked. Frywere stocked at a rate of 250,000 (Trial 1) or 200,000(Trial 2) per acre.

After pools were stocked, catfish starter wasapplied daily to each pool until fish were observedfeeding at the surface. Fish were then fed progres-sively larger floating pelleted diets to satiation daily asthey grew. Pools were drained at 110 (Trial 1) and130 days (Trial 2) after stocking to allow harvest. Atharvest, samples of fish from each pool were weighed.Remaining fish were counted and weighed to deter-mine percentage of survival, yield and feed conver-sion ratio.

Stocking Sac FryResults indicate that the age at which fry were

stocked had no effect on subsequent survival, yield orfeed conversion ratio of fingerling catfish. Based onfinal weight, however, fingerlings reared from frystocked at two and seven days after harvest weresignificantly larger than fingerlings reared from fry


Photo by German Poleo

At hatching, baby catfish (fry) possess a yolk from which they derivenourishment for the first four to five days of life and are called “sac fry.” Thisis how they appear under a microscope.


he best time to plant corn inLouisiana is from mid to late March.During that time lower soil temperaturescan inhibit germination of weed seedsand delay growth of emerged seedlings,which helps with weed management.The critical time to remove weeds fromcorn for maximum yield ranges fromfour to six weeks after planting.

In some cases, depending on weedspectrum, use of soil-applied herbicidesalone can be sufficient for season-longcontrol, especially when corn growth israpid and canopy closure occurs early inthe season. Producers in the mid-Southhave traditionally relied on soil-applied residual herbicides in cornweed control programs; however, thedevelopment of herbicide-tolerantcorn may mean a change in strategy.Use of effective postemergenceherbicides could eliminate the needfor a soil-applied treatment.

The herbicide-tolerant technologiesdeveloped for postemergence control ofweeds in corn include Roundup Ready,Liberty Link and Clearfield. RoundupReady corn is tolerant of glyphosate, theactive ingredient in Roundup formula-tions and Touchdown. Liberty Link istolerant of glufosinate, the activeingredient in Liberty. Clearfield corn istolerant of a combination of imazapyrand imazethapyr, the active ingredients

in Lightning. Each offers alternativeweed management options for cornproducers in the South.

Roundup Ready, Liberty LinkExperiments were conducted over

two years (1998 and 1999) to evaluateweed control programs and cornresponse using the corn hybrids Dekalb580 RR (Roundup Ready) and Cargill7750 LL (Liberty Link) planted in lateMarch. Treatments included:

Bicep (Dual plus atrazine) as astand-alone preemergenceprogramBicep, Dual, Prowl or atrazinepreemergence followed byRoundup Ultra at 1.5 pints peracre or Liberty at 20 ounces peracre early postemergenceAtrazine plus Roundup Ultra at1.5 pints per acre or Liberty at 20ounces per acre earlypostemergenceRoundup Ultra or Liberty at thesame rates early postemergenceRoundup Ultra at 2 pints per acreor Liberty at 28 ounces per acrelate postemergenceRoundup Ultra at 1.5 pints peracre or Liberty at 20 ounces peracre both early and latepostemergence

Accent plus Buctril earlypostemergence, a standard program usedin conventional corn, was included forcomparison. Early postemergenceapplications were made in late April toearly May when weeds were 0.5 inch to5 inches tall and late applications to 1-to 14-inch weeds in late May.

In 1999, 0.6 inch of rainfall wasreceived within seven days of applica-tion. But in 1998, rainfall of only 0.16inch was received within 21 days ofapplication, and no rain fell from week 7through 10. Even though total rainfallwas greater during the growing seasonthe second year (18.2 inches as com-pared to 7.4 inches), rainfall was limitedduring grain fill.

For the two years, 28 days afterapplication of early postemergencetreatments, results were as follows:

Broadleaf signalgrass was con-trolled 74 percent to 93 percent withBicep alone preemergence and, whenfollowed by Roundup Ultra or Liberty,96 percent to 100 percent. For compari-son, Roundup Ultra or Liberty appliedearly controlled broadleaf signalgrass 73percent to 100 percent and, whenapplied late, 91 percent to 100 percent.Broadleaf signalgrass was controlled 70percent to 96 percent with Accent plusBuctril.

Pitted morningglory and pricklysida were controlled most consistentlywith Bicep or atrazine followed byRoundup Ultra or Liberty, or atrazineplus Roundup Ultra or Liberty (91percent to 100 percent). This compareswith 78 percent to 100 percent control ofpitted morningglory and 83 percent to100 percent control of prickly sida withRoundup Ultra or Liberty applied aloneearly. Accent plus Buctril controlledthese weeds 68 percent to 100 percent.

Because of inadequate rainfall, theyield potential of the hybrids was notrealized, and differences observed inweed control were not reflected in yield.

The Clearfield corn on the left was treated with Lightning, apostemergence herbicide. The row on the right was not treated,and itchgrass and broadleaf signalgrass are growing there.

D. Alan Peters and Jason A. Bond, formerGraduate Research Assistants; James L. Griffin,Professor; and Jeffrey M. Ellis, ResearchAssociate, Department of Plant Pathology andCrop Physiology, LSU AgCenter, Baton Rouge,La.

D. Alan Peters, Jason A. Bond, James L. Griffin and Jeffrey M. Ellis

Photo by James L. Griffin

T


Roundup Ultra, LibertyIn another study, Roundup Ultra at

2, 4 and 6 pints per acre and Liberty at28, 56 and 84 ounces per acre (1x, 2xand 3x rates) were applied to therespective hybrids at 4-, 6- and 8-leaf.Corn yield for each hybrid was equiva-lent to the nontreated weed-free controlin 1998, when only 7 inches of rainfallwas received during the growing seasonand in 1999, when corn was irrigated asneeded. Yield the second year was morethan 200 bushels per acre and averaged1.3 times higher than in 1998. Theconsistency in response of the hybrids tothe herbicides over the two diverse yearsindicated a high level of tolerance.

Clearfield StudyExperiments were conducted over

the same two years to evaluate cropresponse and weed control with Light-ning in Clearfield (Pioneer 3395 IR)corn. Weed control programs includedstandard preemergence and post-emergence herbicides applied alone andin combination with Lightningpostemergence. The hybrid was highly

tolerant to Lightningapplied from 5- to 9-leaf at twice thelabeled rate of 1.28ounces per acre.Bicep or Prowl plusatrazine preemergencecontrolled broadleafsignalgrass 50 percentto 86 percent anditchgrass no more than69 percent. Lightningpreemergence con-trolled these weeds nomore than 29 percent.Broadleaf signalgrasscontrol was increasedto 89 percent to 98percent when Light-ning followed Prowl,

atrazine or Bicep preemergence. Thesesame treatments controlled itchgrass 76percent to 83 percent. When onlyLightning was applied postemergence,broadleaf signalgrass was controlled 64percent and 88 percent and itchgrass 71percent.

In the first year, corn yield washighest when Lightning alone wasapplied postemergence, but in thesecond year, yield for this treatment wasno higher than when Bicep was applied.Conditions both years were not condu-cive to the maximum yield potential ofthe hybrid.

New SystemsCan Be Effective

Results indicate that depending onweed spectrum and timeliness ofapplication, Roundup Ultra, Liberty andLightning can provide effectivepostemergence control when used asstand-alone programs. Hybrids weretolerant to the respective herbicides.Consistency in season-long weedcontrol was enhanced in many caseswhen the herbicides followed a preemer-

gence treatment. Preemergence herbi-cides can be beneficial in delayingemergence and slowing growth rate ofweeds to allow flexibility in timing apostemergence application. When onlypostemergence herbicide programs areused, application timing is critical toreduce weed competition and to securemaximum yield potential of the hybrid.The decision to use a soil-appliedherbicide in corn also should be basedon negative environmental effectsassociated with movement of theherbicide from fields when significantrainfall occurs soon after applicationand the potential residual effect on othercrops should replanting be required. Innone of these studies was johnsongrass aproblem weed; however, past researchhas shown that Roundup Ultra, Libertyand Lightning all control johnsongrassand are, therefore, viable options.

Since Roundup Ultra, Liberty andLightning do not have significant soilresidual activity, multiple applicationsmay be required to obtain season-longcontrol. When conditions are conduciveto rapid early season corn growth,coverage of weeds underneath the cropcanopy with spray solution may behindered, requiring use of drop nozzles.

Selection of herbicide programs incorn should be based on grower prefer-ence, yield potential of the hybrid andeconomics. At present, the LSUAgCenter does not recommend herbi-cide-tolerant hybrids that allow for useof glyphosate herbicides (RoundupReady), Liberty (Liberty Link) orLightning (Clearfield). However, whenhigher yielding hybrids are developedfor the mid-South climate, this maychange.

The RoundupReady corn on theleft was nottreated. The cornon the right wastreated withRoundup Ultra at1 quart per acre.

Photos by James L. Griffin

Weed growth stops shortly after application of Lightning inClearfield corn. By 10 days broadleaf signalgrass takes on apurple coloration and itchgrass a pale yellow-greenappearance.


AcknowledgmentLouisiana Soybean and Grain Researchand Promotion Board


Glyphosate, sold under the trade names Roundup Ultra,Roundup Ultra Max, Roundup Original, Glyfos, Glyphomax Plus,Gly-Flo, Glyphosate Original, Touchdown and others, is apostemergence, nonselective herbicide that controls many an-nual and perennial weeds. Soybeans with the glyphosate-resis-tance gene (Roundup Ready soybeans) were introduced in 1996in the United States. In 2001, more than 75 percent of thesoybean acreage in Louisiana was planted to Roundup Readyvarieties, and acreage is expected to increase.

Weed control with Roundup depends on weed species andtheir growth stage and weather conditions at application. Thisherbicide is particularly effective on a number of troublesomeweeds in Louisiana soybeans including sicklepod, johnsongrassand annual grasses such as red rice, common cocklebur, pig-weeds and wild poinsettia. However, Roundup is not as effectiveon hemp sesbania, morningglories, prickly sida (teaweed), spread-ing dayflower and nutsedges.

The availability of Roundup Ready soybeans providespostemergence herbicide alternatives for weed control, butraises questions as to how this technology will fit into currentmanagement programs. According to Monsanto, the manufac-turer of Roundup formulations, soil-applied residual herbicidesare not needed in Roundup Ready soybeans since a single, timelyapplication or multiple applications of Roundup alone are suffi-cient for weed control. An effective soil-applied herbicide,

however, can eliminate or reduce early season competition ofweeds to secure crop yield and allow the grower flexibility intiming a postemergence herbicide application.

The objectives of this research were to determine if soil-applied herbicides used in Roundup Ready soybeans: 1) affectweed density and growth rate, 2) extend the number of daysbetween weed emergence and Roundup application, 3) affectweed control with Roundup and 4) eliminate the need for asecond (sequential) Roundup application.

Three Years of ExperimentsExperiments were conducted for three years, from 1998

through 2000, using Asgrow 5901 RR soybeans planted in 30-inch rows in mid-May to early June at the LSU AgCenter’s BenHur Research Farm near Baton Rouge. Soil-applied preemer-gence treatments included labeled and half rates of the followingherbicides:

Squadron (a premix containing the active ingredients inProwl and Scepter)ProwlDual

Detail (a premix containing the active ingredients inFrontier and Scepter)Canopy XL (a premix containing the active ingredients inClassic and Authority)Canopy (a premix containing the active ingredients inClassic and Sencor).

To activate the herbicide, plotswere overhead irrigated (0.75 inch)within three days after application.If plots had not been irrigated orrainfall received shortly after herbi-cide application, weeds would haveemerged along with soybeans sincesoil moisture was adequate for seedgermination. In this situation,preemergence herbicides wouldhave little influence on weed emer-gence, and their value could nothave been adequately determined.Irrigation was continued as neededthroughout the growing season.

Weeds were monitored attwo-day intervals beginning sevendays after initial emergence to de-termine number of days from soy-bean planting required to reach theselected treatment stage of 4 inches.

The plot in the foreground has been treated with soil-applied preemergence herbicide. Thearea in back and along the sides was not treated. Notice the difference in the number ofweeds present. The marked areas are where the weed counts were made.



Benefits of Soil-applied Herbicidesin Roundup Ready Soybeans


When the first weeds reached this stage, Roundup Ultra wasapplied at 1 quart per acre. Just before the initial Roundup Ultraapplication, weed density and height were determined from eachplot to evaluate the degree of control for each treatment and toassess the herbicide effect on weed growth rate. Weed controlwas visually evaluated 14 days after the Roundup Ultra applica-tion. Soybeans were harvested in late September to mid-October.

No Complete Weed ControlWeeds included barnyardgrass, ivyleaf morningglory, prickly

sida, hemp sesbania and redweed. In most instances, differencesin weed height and density did not change when preemergenceherbicide rates were reduced from the full to half rates, and noneof the herbicides provided complete weed control. The numberof days after planting for weeds to reach the treatment stage forRoundup when no preemergence herbicide was used was 17, 21and 25 for the three years. The rapid growth rate of weeds in thefirst year (17 days) was probably related to the late planting datein early June.

In most cases, the first weeds reaching the 4-inch treatmentsize were barnyardgrass or hemp sesbania, but this depended onthe preemergence herbicide used. The first year, all soil-appliedherbicide treatments reduced growth rate of weeds, providingan extra three to five days before the first Roundup applicationwas needed when compared with no preemergence herbicide.For the second year, the full rate of Canopy extended theapplication time for Roundup by six days. The full rates ofCanopy XL and Canopy were the only treatments to extend theapplication time the third year, providing an additional sevendays.

There were no differences in control of barnyardgrass,prickly sida or redweed among the herbicide treatments evalu-ated 14 days after Roundup was applied. These weeds werecontrolled 93 percent to 100 percent over the three years,showing that use of preemergenceherbicide was not beneficial. Whenonly Roundup was applied, ivyleafmoringglory was controlled 77 per-cent, but control was as high as 86percent to 93 percent whenRoundup followed the high rate ofDetail and both rates of Canopy XLand Canopy. When compared withRoundup alone, hemp sesbania con-trol was increased when Roundupfollowed the high rate of Detail (81percent) or Canopy XL (83 per-cent) and both rates of Canopy (85percent and 95 percent). Neitherhalf nor full rates of preemergenceherbicides followed by Roundupcould control hemp sesbania com-pletely, and an application of Blazerwas needed each year.

Soybean Yields EqualSoybean yield was equivalent for all herbicide treatments

and averaged 37.8 bushels per acre, further showing that a totalpostemergence program using Roundup was as effective aswhen preemergence herbicides at either half or full rates werefollowed by Roundup.

This research shows that the decision to use preemergenceherbicides in Roundup Ready soybeans should be based oneconomics and grower preference rather than differences inweed control and crop yield. Where a preemergence herbicidewas used, only a single Roundup application was needed. Incontrast, two Roundup applications were needed in two of threeyears when preemergence herbicide was not used. In yearswhere growing conditions favor the soybean crop (adequatemoisture and narrow row spacing), however, a single Roundupapplication may be sufficient whether or not a soil-appliedtreatment is used.

Results show that weeds emerging with soybeans do notaffect crop yield negatively when the initial application ofRoundup is made within three weeks after weed emergence.The extension in the time period to make an initial Roundupapplication when weed growth is delayed with some preemer-gence herbicides (three to seven days depending on year) maybe extremely important in diversified operations where timeconstraints exist.

AcknowledgmentThe Louisiana Soybean and Grain Research and Promotion Boardprovided funds to support this research.

Jeffrey M. Ellis, former Research Associate; James L. Griffin, Professor;and Curtis A. Jones, Research Associate, Department of Plant Pathologyand Crop Physiology, LSU AgCenter, Baton Rouge, La.

The area to the right of the pen has been treated with soil-applied herbicide. The area onthe left has not.




Cerize Deep wine red oakleaf. Highly rated for baby leaf. More solidlyred than Red Salad Bowl with fuller, more compact head. 28 days baby,51 days full size.

Red Sails Deep burgundy red over green. Taste stays mild for a longtime without bitterness. 1985 All-America Winner. Slowest flowering redleaf lettuce. 29 days baby, 55 days full size.

Vulcan Brilliant red. Combines earliness, color, size and flavor. Crispand mild. Ruffled, slightly frilled leaves are candy apple red over a lightgreen background. 28 days baby, 52 days full size.

Royal Oak Dark green. Highly rated for baby leaf harvesting. Largebroad plant with low density and slow flowering. 28 days baby, 50 daysfull size.

Galactic Dark red. Developed for baby leaf harvest. Like Redina but abit smaller, frillier, slightly darker red and 2-3 days slower to flower. 30days baby, 58 days full size.

As urban gardening has become more popular so has interest ingrowing leaf lettuce. Compared to head lettuce, leaf lettuce is quickerto mature, less prone to disease and more nutritious. Because of itsrelatively fast growth, leaf lettuce can provide a continuous harvestfrom late October to mid-February, if planted at two-week intervals.In addition to producing fresh produce throughout the winter, thevariety of color and texture among leaf lettuce cultivars can add to thebeauty of the ornamental garden. Tests were conducted at the LSUAgCenter’s Burden Center in Baton Rouge to evaluate the suitabilityof different leaf lettuce cultivars for use as an edible ornamental in smallurban gardens.

Eleven commercially available leaf lettuce cultivars were planted inOctober 1999. Although leaf lettuce seed can be sown directly into thegarden soil, plants were started from seed sown in small pots andtransplanted to raised beds after about four weeks. This methodensures a viable plant, eliminates the need for thinning seedlings andprovides an opportunity to apply a preemergence herbicide to inhibitthe germination of weed seeds. Plants spaced 10 to 12 inches apart willshade the soil within a short time, which will reduce weed growth.Lettuce needs a fertilizer with more nitrogen than flowering and fruitingplants, so the percentage of nitrogen should be at least twice that ofphosphorus and potassium. A fertilizer, including micronutrients, with

Growing Leaf Lettuce in Louisiana’s



Lollo Rossa Medium green leaves tipped with red heavily frilled edges.Mild flavor, Italian variety good for garnishes. Slow to flower. 30 days baby,53 days full size.

Carisma Heavily frilled, medium green leaves tipped with a strong,warm red. Good for garnishes and salad mix. Slow to flower. 30 daysbaby, 51 days full size.

Red Salad Bowl Wine red. Highly rated for baby leaf. Deeply lobed,delicate oak-like leaves form a full rosette. Slow to flower. 28 days baby,51 days full size.

Simpson Elite Light green. Extra-slow flowering. More ruffly, slowergrowing and much slower flowering than Black Seeded Simpson. 53 daysfull size.

a ratio of 12-6-6 was applied at planting and again after six weeks. Morefrequent applications of a liquid fertilizer would work as well. Nopesticides were applied during the evaluation period.

Among all the cultivars evaluated, Galactic and Redina rated thehighest for visual quality and insect and disease resistance. Royal Oak,Vulcan, Simpson Elite, Red Salad Bowl and Waldman’s Dark Green alsoperformed well. All cultivars had excellent visual quality and pestresistance ratings up to their recommended date of maturity (49 to 58days) and continued to perform well as an ornamental for up to 90 days.Vegetative growth began to decline from 90 to 120 days and plantsbegan to flower.

By February 15 (135 days) all cultivars were in the full stage offlowering. Except for Simpson Elite, which was slightly frost-burned, allwere undamaged by freezing weather on December 16 (29 degrees)and January 5 (28 degrees). The overall appearance of all cultivars wasvery poor by March 1 (150 days), and the trial was terminated.

In general, all of the cultivars are good candidates for the cool-season edible ornamental garden from October through February.

Drew Bates, Associate Professor, and Anthony Witcher, Research Associate,Burden Center, Baton Rouge, La.

Ornamental and Vegetable Gardens

Photos by Drew Bates

Waldman’s Dark Green (left) Dark green, frilled, ruffled leaves forma well-bunched head. Standard green leaf lettuce of the produce trade.28 days baby, 49 days full size. Redina (right) Color is an intensecandy red with green butt. Pliable, non-brittle ribs. Slow to tipburn. 29days baby, 55 days full size.



G rowing winter wheat has multiplebenefits that can lead to an increase infarm productivity. A wheat cover cropstabilizes the soil during high rainfallmonths and increases soil productivityby increasing organic matter andbiological activity. Wheat is especiallybeneficial when the residue is left on thesoil surface and the following summercrop is planted using no-till practices.

These are some of the research plots at the Northeast Research Station used to study rateand timing of burndown of wheat cover crops. Fifteen studies were conducted between 1998 and 2000.

Bill J. Williams, Assistant Professor, NortheastResearch Station; Donald J. Boquet, Professor,Macon Ridge Research Station, Winnsboro, La.,and Donnie K. Miller, Assistant Professor,Northeast Research Station, St. Joseph, La.

The residue covers the soil, which helpsto prevent packing effects of rainfall.This reduces runoff and increasesrainfall infiltration. The residue alsoprotects seedlings from rapid tempera-ture changes and wind damage. No-tillplanting into wheat cover crop residueconsistently increases the yield of cottonand may increase the yield of othercrops. With this practice, growth of thewheat is usually terminated before grainfill and not harvested for grain, so thecotton crop can be planted on time.

To obtain maximum benefits from awheat cover crop, the wheat must becompletely terminated three weeksbefore planting a summer crop. Wheatcover crops are typically terminated

with a nonselective herbicide, such asparaquat or glyphosate, applied betweenjointing (stem elongation) and maturity.After jointing and before heading, wheatis less susceptible to paraquat. Inconsis-tent results and the reluctance of manyaerial applicators to apply paraquatmake glyphosate the more popularherbicide for terminating wheat covercrops. Occasionally, producers observeless than optimum results with single orsequential glyphosate applications,raising the question of varietal differ-ences in tolerance to glyphosate.

However, differences in glyphosatetolerance among wheat varieties werenot expected to account for the largedifferences in treatment efficacy. Wheat

Bill J. Williams, Donald J. Boquet and Donnie K. Miller

Wheat Cover Crops:Wheat Cover Crops:Benefits and ManagementBenefits and Management


Table 1. Effect of glyphosate rate and wheat growth stage on wheattermination 3 weeks after treatment.

Wheat Wheat Range ingrowth stage termination termination

% %Glyphosate at 0.75 lb active ingredient per acre: prior to jointing through two visible nodes 90 (80 to 100) three visible nodes through last leaf just emerging 90 (85 to 100) early boot through early heading 75 (60 to 90) fully headed to flowering 85 (80 to 90)

Glyphosate at 1.0 lb active ingredient per acre: prior to jointing through two visible nodes 95 (85 to 95) three visible nodes through last leaf just emerging 95 (90 to 100) early boot through early heading 83 (80 to 90) fully headed to flowering 90 (80 to 95)

Data represent the average level of wheat control observed in 15 trials conducted from 1998 to 2000.Data were averaged across 11 wheat varieties.

growth stage at the time of glyphosateapplication and glyphosate rate aresuspected to be more likely reasons forunsatisfactory results. Therefore, theeffects of variety selection, wheatgrowth stage and glyphosate applicationrate on terminating wheat cover cropswere evaluated from 1998 through 2000at the Northeast Research Station.Different formulations of glyphosate(Roundup Ultra, Touchdown andEngame) were also compared.

Glyphosate was applied at differenttimes and rates to selected wheatvarieties to evaluate the effects of wheatgrowth stage and variety on glyphosateeffectiveness for growth termination.When glyphosate was applied (February15, March 1, March 15 and March 25),each variety was at a different growthstage. Because of this, it was difficult tocompletely separate growth stage fromvariety effects. However, out of the 15studies conducted between 1998 and2000, enough observations were madefor several varieties at similar growthstages to identify important trends.

Of the 11 varieties compared, onlysmall differences in varietal tolerance toglyphosate were observed. Wheatgrowth stage at time of glyphosateapplication was one of the most impor-tant factors in determining the successof terminating wheat cover crops.Glyphosate efficacy was best (at least 90percent) and most consistent whenwheat was treated before boot growthstages or after heading (Table 1).Effectiveness varied with glyphosateapplications made to wheat beforejointing up to two visible nodes. Whilenot demonstrated in Table 1, the

Wheat growth stage at time of glyphosate application was the most important factor indetermining the success of terminating wheat cover crops. In this plot, Roundup Ultra wasapplied prior to jointing.

increased variability in glyphosateefficacy was strongly associated withapplications made before jointing andwas a result of wheat re-growth.Glyphosate applications to wheat inearly-boot to early-heading growthstages were largely ineffective, rangingfrom 75 percent to 83 percent.Glyphosate applications on wheat fullyheaded or flowering were similar inefficacy (85 percent to 90 percent) toapplications made to wheat with threevisible nodes or smaller.

Application rate also influencedglyphosate effect on wheat growth

termination. Glyphosate used at a rate of0.5 pound active ingredient per acre didnot adequately control wheat regardlessof variety or growth stage (data notshown). When applications were madeat susceptible growth stages (less thanthree visible nodes or fully headed), the0.75 and 1.0 pound rates were equallyeffective. Glyphosate at 1.0 poundactive ingredient per acre was about 10percent more effective than at a 0.75pound rate when wheat was at a transi-tional or difficult to control (last leafemerging through early heading) growthstage. All formulations of glyphosatewere equally effective when applied atsusceptible growth stages and recom-mended rates.

While small differences in glypho-sate tolerance among wheat varietieswere noted, growth stage at the timeglyphosate was applied was the mostcritical factor in determining the degreeof growth termination. Variety selectionis still important, though, becausevariety and planting date will determinethe growth stage when glyphosate istypically applied (mid to late March).The best approach for terminating awheat cover crop is to apply glyphosateat a rate of 0.75 to 1.0 pound activeingredient per acre before wheat reachesthe boot growth stage or after it is fullyheaded and beginning to flower. Thelater date is preferred because the wheathas at this point produced maximumvegetative growth and will provide fullbenefits of a cover crop.

Photos by Bill J. Williams

18 Louisiana Agriculture, Summer 2001Photo by John Wozniak


The new feed mixing facility at the SoutheastResearch Station allows the purchase of feed inbulk, which saves on operating costs. The systemis computer operated. By pushing a button,various rations can be mixed for researchpurposes and for maintenance of the dairy farm.

New Tool to Gauge Dairy Herd Nutrition:

Milk Urea NitrogenMilk Urea Nitrogen


ietary protein is a key nutrient for high milk productionin dairy cows. But determining how much protein a cowconsumes and how well it is used is difficult, particularly at thefarm level. A new tool being explored is the measurement oftrace amounts of nitrogen in the milk. This analysis is known asmilk urea nitrogen (MUN).

Excess dietary protein is converted to ammonia by micro-organisms in the rumen of the cow and is quickly absorbed intothe bloodstream and converted to the less toxic urea by theliver. The level of urea in the blood is equal to the nitrogen levelin the milk, thus leading to the MUN mea-surement.

Normal levels of MUN range from 12to 18 milligrams per deciliter. Values below12 indicate insufficient dietary protein in-take for maximum milk yield, and concen-trations above 18 indicate excess crudeprotein intake and soluble protein in thediet. Feeding dairy cows excess dietaryprotein is costly, and recent research at theLSU AgCenter’s Southeast Research Sta-tion has shown a detrimental effect onreproduction. Yet, little is known abouturea concentrations in the milk from Loui-siana dairy herds and how they relate toseason, feeding systems used and animalperformance.

To answer some of these questions, astudy was conducted to compare MUNlevels with feeding practices, lactation per-formance and reproduction. Bulk-tank milksamples were taken monthly from 26 Loui-siana dairy farms from March through Au-gust of 1998. All herds in the study usedartificial insemination and the Louisiana DairyHerd Improvement Association recordkeeping system.

8

10

12

14

16

18

20

MU

N, m

g/dl

Mar Apr May Jun Jul Aug

9-2610-24

12-2312-24

9-21

10-20

Month

8

10

12

14

16

18

20

MU

N, m

g/dl

Past. P+H P+S P+WBG TMR

11-23

13-24

12-19

15-26

10-19

Feeding System

Figure 1. Effect of Season and Forage System on BulkTank MUN Concentrations in Louisiana Dairy Herds.

MUN (milk urea nitrogen) numbers above bars indicate the range (mini-mum and maximum values) for each category. Past. = pasture only, P+H =pasture and hay, P+S = pasture and silage, P+WBG = pasture and wetbrewers grains, and TMR = silage-based total mixed ration.



Michael E. McCormick, dairy nutrition researcher, is in the milk room in the newdouble-five (10 stalls) milking parlor at the Southeast Research Station. This bulk milktank stores 3,000 gallons.

D MUN Levels Higher in SpringAverage MUN levels peaked in April at 17.9 and declined to

14.2 in August (Figure 1). Although these averages seem fairlymoderate, some herds experienced monthly concentrations aslow as 9; others contained MUN levels as high as 26, well outsidethe recommended range of 12 to 18. In fact, 58 percent of theherds evaluated had one bulk-tank MUN sample above 18 duringthe spring months of March through May, and only 29 percentof the herds exhibited elevated MUN during the summer.

During the spring, 85 percent of the herds usedannual ryegrass pasture in their forage systems. Youngryegrass pasture often contains 30 percent or morecrude protein, of which as much as 45 percent may be inthe soluble form. These high concentrations of ryegrassprotein, coupled with a relatively high protein concen-tration in grain supplements (80 percent of grain supple-ments contained 18 percent or more protein), likelyprovided more dietary protein than required by thelactating dairy cow. Only 15 percent of milk samplestested had MUN concentrations below 12, indicatingthat dietary protein shortage was not common amongthe herds evaluated.

Variations in MUN with Feeding SystemThe dairies in the study used several different forage

feeding systems. In the spring, about 20 percent usedpasture (ryegrass) alone, 35 percent used pasture plussome form of ensiled forage, 20 percent used pastureand hay and 15 percent used pasture supplemented withwet brewer’s grains. Fewer than 10 percent used totalmixed rations (TMR), which is grain and forage mixed.


Ryegrass, bahiagrass and bermudagrass are grown at the Southeast Research Station. The cows graze on pastures November throughMay.



Research Station in which dairy cows within the recommendedrange of urea nitrogen in milk and plasma experienced 29percent higher pregnancy rates than those cows with high ureanitrogen (25 milligrams per deciliter).

Implications for Dairy ProducersThe results of this study show that bulk tank milk urea

nitrogen can be used as an indicator of dietary protein excess ordeficiency in dairy cattle. Since Louisiana dairy herds showed ahigher concentration of milk urea nitrogen in spring, when mostcows were grazing ryegrass, some herds may benefit fromlowering the protein content in grain supplements, particularlywhen ryegrass is immature and abundant. Producers may be ableto use bulk tank MUN to monitor dairy herds after a rationchange, when cows change pasture or when a new forage is used.Bulk tank samples are useful for monitoring protein nutrition ona herd level. To diagnose a particular problem, individual cowsor cow groups may need to be sampled. MUN analysis offersdairy producers another tool to help fine-tune nutritional needsof cows, which may improve profitability by reducing proteincosts, improving milk yield and lowering reproductive costs.Commercial laboratories are available that will measure MUNconcentrations for a nominal fee.

Michael E. McCormick, Associate Professor, Southeast Research Station,Franklinton, La.; Angelica M. Chapa, Graduate Assistant, and J. MarcosFernandez, Professor, Animal Science Department, LSU AgCenter, BatonRouge, La.; James F. Beatty, Professor and Resident Director, SoutheastResearch Station, Franklinton, La.

In summer, pasture (bahiagrass, bermudagrass or crabgrass)usage was similar to that recorded in spring, but the proportionof herds using TMR increased to nearly 20 percent of the total.

Milk samples from herds that relied on pasture and hay orTMR to meet forage needs generally had acceptable MUNconcentrations (Figure 1). In contrast, bulk tank MUN samplesfrom herds that received only pasture or pasture supplementedwith wet brewer’s grains were high, averaging between 18.3 and19.5. A few herds receiving ensiled forages had MUN concentra-tions below the recommended threshold of 12, suggesting aprotein shortage. Most of the silage used in the dairy herdfeeding systems was made from whole-plant corn, a low-proteinforage.

MUN Levels and Herd PerformanceIn this study, milk production (average test day milk yield)

was not closely correlated with bulk tank MUN concentration;however, average milk fat and protein percentages tended to belower when MUN was higher than 18. A poor correlationbetween MUN and milk yield may be because most herds withMUN concentrations outside the range indicative of optimumprotein nutrition were high, suggesting that more than enoughprotein was available for maximum milk production.

An examination of reproductive data revealed that estrusactivity was not affected by milk urea nitrogen concentration,but pregnancy rates tended to be higher in herds with normalMUN levels. This supports recent research at the Southeast


hauling more expensive. Southeast Louisiana still has enoughconcentration.

“The dairy industry in local areas must be careful of fallingbelow the critical mass needed to maintain the industry,” he says.“There must be enough production to make hauling, feedproduction and equipment dealers profitable enough to be inbusiness in close proximity to the producers.”

In cooler climates, cows produce well in summer monthswhile production falls off in colder winter months. For southernproducers, winter is prime time.

“Heat and high humidity depress production,” Beatty says.“Summer forage of bahiagrass and bermudagrass provides low-quality feed, and farmers can’t afford to haul in forage.”

Winter and spring, however, are different.“Ryegrass in winter has kept us in business,” Beatty says.

“November to May, we have excellent pastures and coolweather.

“Around here, it’s cheaper to let the cows get the grass forthemselves,” he says. “About 250 head appears to be the limitfor pasture-based production in Louisiana.”

Scientists at the Southeast Research Station have beenexperimenting with ryegrass “baleage,” wrapping plastic aroundbales of ryegrass hay to provide summer feed. It’s proving to beeffective in improving milk production and summer profitability.

Unlike those in other parts of the country, Louisianafarmers keep their cows on pasture rather than in confined lots.Along with year-round pastures, Louisiana dairy farmers don’thave to invest in warm, weather-tight barns or confinementfacilities.

Louisiana consumers would face higher milk prices withoutlocal producers, Beatty says.

“Our advantage is distance our competitors have to travel,”he says. “We’re going to have to keep our costs low enough tocompete with other parts of the country.”

The state’s dairy farmers have proved adept at low-costproduction, even though average per-cow productivity is thelowest in the United States. But many established dairy produc-ers have few alternatives for their labor and their past invest-ments in dairy-specific assets, Gauthier says.

Until urban pressures drive up the costs of land, the limitedalternative uses will continue to allow dairying in southeastLouisiana.

A looming concern is milk production’s movement awayfrom consumers. Comparing the first quarter of 1995 with thefirst quarter of 2000, national milk production increased 8percent. Regionally, however, production fell 9 percent in theSoutheast, rose 6 percent in the Northeast, rose only 2 percentin the North Central and rose a whopping 27 percent in theWest.

This means more milk is coming to market from fartheraway. If milk marketing programs do not change, Beatty andGauthier say, local milk production and the accompanyingeconomic benefits could disappear as technological advancesreduce production and transportation costs. Rick Bogren

Louisiana’s dairy industry continues to hold its own despitea threat from the West’s rapidly growing dairies and fast-changing technology that may eventually erode any advantagesover other regions.

The dairy industry generates nearly $100 million in farmincome and more than $150 million in value-added income forthe state, according to the 2000 Louisiana Summary of Agricul-ture and Natural Resources published by the LSU AgCenter.

The three parishes of St. Helena, Tangipahoa and Washing-ton comprise the vast majority of Louisiana’s current milkproduction with a few farms scattered in northwest Louisiana.

Generally speaking, says Jim Beatty, resident director of theLSU AgCenter’s Southeast Research Station in Franklinton, La.,both milk prices and production costs are higher as you movefrom north to south in the United States. And because Louisianais so far south, shipping milk north is not profitable. Northerndairy producers, on the other hand, can ship milk south, takingadvantage of those higher prices to offset transportation costs.

Approximately 700 dairy farms operate in an 80-mile radiusof Franklinton. This area represents about 80 percent of allLouisiana production and about 55 percent of all Mississippiproduction, accounting for about 1 billion pounds of milk peryear.

“This is the only concentration of milk production betweencentral Texas and Florida,” Beatty says.

During the mid 1990s, experts were fearful Louisiana’s milkindustry would vanish completely.

“Twenty years ago Louisiana had more than 1,000 dairyfarms. Today there are about 430,” says Wayne Gauthier, aneconomist in the LSU AgCenter’s Department of AgriculturalEconomics. “The dairy industry is moving to fewer, larger farmswith more geographic pockets of milk production.

“Generally, the initial investment in any dairy-specific tech-nology constitutes a high fixed cost,” he says, adding that iffarmers decide to invest in technology, they must also get largerto spread the high fixed costs over more units to reduce theiraverage costs and remain competitive.

After the mid 1990s, the producers left are efficient opera-tors who have been in business for a long time and have a lowdebt burden, Beatty says.

“They practice dairying because there are few alternativesto crop the land,” he says.

To gauge how well a dairy farm performs, Beatty says theLSU AgCenter research programs look at productivity per cow.

“A living wage requires a critical mass,” he says. “Dairyproducers with low margins but with enough production canrealize a reasonable income.”

Average herd size in Louisiana is about 140 cows, muchsmaller than large operations in California and the PacificNorthwest, where production is growing while other states aredeclining. The national average herd is 111 cows, Beatty says.

For northern Louisiana, the diminishing number of dairyfarms is lowering the critical mass and making such things as

Dairy industry’s contribution to Louisiana’s economy:


More than a drop in the bucket


he production and marketingenvironments of row crop agriculturehave changed dramatically sincepassage of the 1996 Farm Bill. Underprevious Farm Bills, price supportsystems let producers establish continu-ous or monocrop cropping systems withless concern for market signals. For themost part, as long as producers couldgrow the cropefficiently,the pricesupportsystemprovidedsufficientreturns toassureprofitability.The farmprogramprovisionsencouragedyear-after-year plantingof a singlecommodity,which prevailed as a primary croppingsystem used by farmers in Louisiana’sMississippi River Delta.

Current agricultural policy, how-ever, is more market-driven. Producershave to be more responsive to marketsignals because of increased income riskand uncertainty. The removal of acreagerestrictions along with governmentpayments no longer tied to productionhave given the producer the flexibility toselect crop mixes and cropping systemsbased on market signals rather thanpolicy provisions. This has broughtincreased interest in the use of croprotation systems as both a productionand marketing risk management tool. Touse crop rotation effectively, however,

T

Kurt M. Guidry, Assistant Extension Specialist,and Amos Bechtel, former Assistant Professor,Department of Agricultural Economics, LSUAgCenter, Baton Rouge, La.; Steve Hague,Assistant Professor, and Robert Hutchinson,Resident Director, Northeast Research Station, St.Joseph, La.; and Donald Boquet, Professor,Macon Ridge Research Station, Winnsboro, La.

Profitability of Cotton Crop Rotation

requires an understanding of theproduction costs and yield effects of theannual crop selection decision.

Why Crop Rotation?Recent trends in cotton, corn and

soybean acres in Louisiana indicate thatproducers may become more receptiveto crop rotation systems (Figure 1).

Cotton acreage in Louisiana before the1996 Farm Bill had increased from810,000 in 1990 to nearly 1.1 millionacres by 1995. By 1998, however, cottonacreage had decreased to 535,000, adecline of more than 50 percent from thepeak reached in 1995. During this sameperiod (from 1995 to 1998), cornacreage increased by more than 200percent, and soybean acreage increasedby more than 12 percent.

Crop rotation is not a new phenom-enon in production agriculture. Benefitsinclude improved soil productivity andpest management and enhanced riskmanagement with greater enterprisediversity. Rotation can provide moreplant residue to soil than monocropsystems, thus improving tilth and water-holding capacity. By alternatingbetween the different types of rootsystems of the various crops, more ofthe soil profile is used for crop produc-tion. In addition, rotating crops aidsintegrated pest management strategies.Rotation may disrupt life cycles of manyinsect pests and pathogens. Increasing

plant diversity also may encouragebeneficial insects, nematodes, fungi andbacteria to flourish. Moreover, rotationprovides growers with an opportunity toalternate herbicides. For instance, weedsdifficult to control in corn, such asjohnsongrass, may be easier to managewith herbicides labeled for cotton orsoybeans.

Tho

usan

d A

cres

Cotton0

200

400

600

800

1000

1200

1400

Soybean Corn

1992 1993 1994 1995 1996 1997 1998 1999

Figure 1. Louisiana Planted Acres, Selected Crops, 1992-1999

Analyzing Crop RotationData

This economic analysis includes 10years of crop rotation data from 1989 to1998 taken from research studies doneon Commerce silt loam soils at the LSUAgCenter’s Northeast Research Station.The research station is located in theMississippi River alluvial flood plain inTensas Parish near St. Joseph, La. Threecontinuous cropping systems and fiverotational systems were included in thestudy. Both two- and three-year rota-tions were considered with cotton as thebase crop rotated with either corn orsoybeans or both.

All continuous crops were plantedeach year of the study. But, because ofspace limitations, all rotation treatmentswere not grown in the same year. Forexample, the cotton-corn rotation didnot include both the corn and cottonportions of the rotation in the same year,so averages of each crop’s yields wereinadequate to determine the effect of therotations on crop yield within eachrotation. Therefore, the missing years’

Systems in Northeast LouisianaKurt M. Guidry, Amos Bechtel, Steve Hague,

Robert Hutchinson and Donald Boquet


crop yields were estimated using linearregression methods. The estimated cropyields are shown in Table 1. In all casesfor all crops, the crop rotations resultedin higher crop yields than continuouscropping.

To compare the profitability of thealternative rotations, the concept of arotation acre was used. The rotation acreassumes each crop in the rotationsequence is produced in equal propor-tion each year or, alternatively, eachacre could be thought of as beingcomposed of an equal proportion of eachcrop in the rotation. This allows thedirect comparison among single, two-and three-year systems.

Production cost estimates weredeveloped for each crop using the 1999Louisiana Agricultural ExperimentStation enterprise budgets for northeastLouisiana. Primary cost savings in eachrotation were the result of reducednitrogen requirements for cottonfollowing either corn or soybeans.Nitrogen fertilizer applications werereduced by 25 pounds nitrogen per acrefor cotton following soybeans and 20pounds per acre following corn.

PestManagement’sBenefitsAlthough crop rotationcan be a benefit to pestmanagement, the costsavings are moredifficult to quantify.Disruption of the lifecycles of insect pestsand pathogens, alongwith the ability toalternate herbicides tocontrol weeds, can helpincrease the efficiencyand success of pest

management strategies. Rotationalsystems, however, do not necessarilyguarantee fewer pesticide applicationsor the ability to use less expensivepesticides. In addition, current pestmanagement systems specified in the1999 enterprise budgets were assumedto be cost effective enough that substan-tial savings in pest management wouldnot be experienced. As a result, thebenefits of crop rotation on pest man-agement were viewed to affect theprofitability of rotational systems overmonocrop systems in terms of yieldresponse rather than cost savings.

Which cropping system to use isbased upon the expected costs andreturns for each alternative system.Expected returns for each alternative aredetermined, given the producer’sexpectation of yields and prices. Giventhe poor market conditions and pros-pects for cotton, corn and soybeans,expected prices were set at the averageloan rate in 1999 for each commodity.Expected yields were set at the esti-mated average yields shown in Table 1.

Gross revenues and net returns overdirect costs per rotation acre are shownin Table 2. Under the base price sce-

nario, the rotationhaving the highestreturn over direct costswas the cotton-cotton-soybean rotation at$294.58 per rotationacre. The returns tocontinuous cotton,cotton-cotton-corn andcotton-soybean rota-tions were similar at$244.89, $243.31 and$237.88 per rotationacre, respectively. Theranking of crop rotationstrategies is, however,sensitive to the price

relationships among the three commodi-ties, and an increase in the price of oneor two commodities could change therelative profitability of each rotation.

Figure 2 shows the change in thereturns over direct costs per rotationacre for the six cotton rotations as thecotton price increases relative to thecorn and soybean base price. Todetermine the impact of different pricescenarios, cotton prices were varied in10 percent increments from the baseprice of 52.4 cents per pound. Resultsindicated that, as cotton prices trendhigher, the rotations with a higherproportion of cotton increased inprofitability faster than did the otherrotations. Returns per rotational acre forthe continuous cotton strategy experi-enced the highest improvement inreturns with roughly a 25 percent

Table 1. Average Crop Yields 1989-1998 UnderAlternative Rotations, Northeast ResearchStation.

Cotton Soybean CornYield Yield Yield

Rotation (Pounds) (Bushels) (Bushels)Continuous Cotton 1,169 N/A N/AContinuous Corn N/A N/A 128Continuous Soybean N/A 44 N/ACotton-Corn 1,258 N/A 149Cotton-Soybean 1,202 52 N/ACotton-Corn-Soybean 1,311 54 154Cotton-Cotton-Soybean* 1,310 55 N/ACotton-Cotton-Corn* 1,287 N/A 147

*Cotton yield is the mean of both years of cotton production.

increase for each 10 percent increase inprice. Conversely, the cotton-corn-soybean rotation saw only around a 10percent increase in returns for each 10percent increase in cotton price.

Varying cotton prices had littleeffect on how each rotation strategyranked in terms of profitability. A 10percent increase in cotton prices fromthe base price of 52.4 cents per poundreplaces the cotton-corn rotation as theleast profitable strategy with the cotton-corn-soybean rotation. The only otherchange seen was when the cotton pricewas increased by 40 percent from thebase price. At a 40 percent increase inthe price of cotton, the continuouscotton system replaces the cotton-cotton-soybean as the most profitablestrategy.

Figure 2. Returns Per Acre AboveDirect Costs for Six CottonRotations at Varying Cotton Prices

150

250

350

450

550

Ret

urns

Per

Rot

atio

nal A

cre

(Dol

lars

/Acr

e)

$0.52 $0.58 $0.63 $0.68 $0.73Cotton Price (Cents/Pound)

Cotton-Cotton-SoybeanContinuous CottonCotton-Cotton-CornCotton-SoybeanCotton-Corn-SoybeanCotton-Corn

Table 2. Estimated Production Costs andReturns per Rotation Acre for AlternativeRotations, Northeast Research Station, 1999.

ReturnsAbove

Direct Gross DirectRotation Costs Revenue Costs

Dollars Per AcreContinuous Cotton 452.41 697.30 244.89Continuous Corn 198.93 255.10 56.17Continuous Soybean 73.39 235.57 162.18Cotton-Corn 323.47 523.95 200.48Cotton-Soybean 260.14 498.01 237.88Cotton-Corn-Soybean 239.73 459.74 220.01Cotton-Cotton-Soybean 324.23 618.81 294.58Cotton-Cotton-Corn 366.45 609.76 243.31


Yields Higherin Rotational Systems

Crop rotations have the potential toimprove crop yields and whole-farmprofitability. Profitability of the selectedrotational systems was affected by bothimproved yields and cost savings;however, results indicated that enhancedyields proved to be the most criticalfactor in the relative profitability of eachrotation. In this analysis, yields for eachof the rotational systems were higherthan the monocrop systems. Potentialcost savings from rotational systems aredifficult to pinpoint and were assumedto be limited to savings in fertilizerapplication.

Using the base crop price scenarioand mean rotation yields, the cotton-cotton-soybean rotation provided thehighest return over direct productioncosts. The cotton-cotton-soybeanrotation had returns above direct coststhat were $49.69 per acre and $132.40per acre higher than the continuouscotton and continuous soybean systems,respectively.

The ranking of each rotationalsystem in terms of profitability re-mained fairly stable even as cottonprices were allowed to change. Onlywith a 40 percent increase in cottonprices did the cotton-cotton-soybean


Last summer, far to the north from their historic home inthe Andes on a ranch near Bozeman, Mont., two llama mamasgave birth to alpacas.

These were the first cross species births between alpacaand llama brought about through embryo transfer technology.

“The first we know of anyway,” said Paul Taylor, owner ofTaylor Llamas, the ranch about 23 miles north of Bozeman onmountainous terrain where the historic event occurred. Taylorlives there with his wife, Sally, and about 150 llamas.

Taylor received support and ad-vice on this project from Robert Godke,researcher with the LSU AgCenter.Godke is director of the Embryo Bio-technology Laboratory. He has been apioneer in assisted reproductive re-search for more than 25 years, helpingto perfect techniques for test tubefertilization, embryo microsurgery andthe implantation of these embryos intosurrogate mothers.

Some of the latest projects at theLSU AgCenter’s lab include the cloningof goats and cattle and the first horseborn through the process of test tube,or in vitro, fertilization that involvedtaking eggs from a pregnant mare. Hisgraduate students have gone on tobecome leaders in both animal andhuman assisted reproduction.

The Taylors, who have operated allama ranch for 25 years supplying theexotic pet industry around the world,had read of Godke’s research work.Taylor, a former dentist and self-taughtin embryo transfer techniques, has pro-duced more than 100 embryo transfer

llama babies from llamas. Several years ago, the Taylors made acooperative agreement with Godke’s team for help in enhancingtheir expertise.

Although the successful births are good for Taylor’s busi-ness, they are also good for science, Godke said.

“We’re expanding our knowledge of how to be successfulin cross species embryo transfer,” Godke said. “This hasimplications for the domestic animal industry and certainly thesurvival of endangered species.”

Though not endangered, the al-paca is rarer than the llama and smallerin size. Alpacas stand about 3 feet highat the shoulder and weigh 120 to 250pounds. Llamas grow to about 45 inchesat the shoulder and can weigh up to500 pounds.

The Taylors’ next quest will betrying to produce the vicuna, which isa nondomesticated member of the samecamelid family as llamas and alpacas.The vicuna, which is even smaller thanthe alpaca, is endangered. Taylor isnegotiating with the Argentina govern-ment to obtain some vicuna skin cellsto use for vicuna propagation.

“With adult cells we can try toproduce clones,” Godke said. That isthe way Dolly, the sheep in Scotland,was cloned.

One of Godke’s graduate students,Aidita James from Houston, Texas,assisted the Taylors in their cross spe-cies embryo transfer project.

“This success will help pave theway for saving the vicuna,” she said. Linda Foster Benedict

Llama Mamas Give Birth to Alpacas

“Minnie,” the embryo transplant alpaca, withher surrogate llama mama.

Photo by Paul Taylor

Embryo Transfer Offers New Hope for Saving Endangered Species

rotation lose its status of most profit-able. With cotton prices at 40 percenthigher than the base scenario, thecontinuous cotton system becomes themost profitable.

This study was initiated before theadoption of transgenic crops and theboll weevil eradication program, andboth are likely to affect any croprotation decision. These factors likelydiscourage crop rotation by curtailingsome expenses of insect and weedcontrol in a monocrop system. Somebenefits of rotation over monocropsystems have diminished with theadvent of transgenic crops and the bollweevil eradication program.


Soil electrical conductivity was measured in a produc-tion field at the Dean Lee Research Station and found tocorrelate with soil texture, organic matter, soil nutrientsand crop yield. Research is under way to calibrate nitrogenneeds in corn and cotton based on soil electrical conduc-tivity, paving the way for site-specific fertilizer application.

Measuring electrical conductivity in soil has beeninvestigated as a way to determine its fertility and produc-tivity. This may help farmers make site-specific fertilizerapplications. The end result is increased efficiency andreduced waste. A research project at the LSU AgCenter’sDean Lee Research Station was initiated to determine howclosely electrical conductivity corresponded to changes insoil texture, soil nutrient concentration and crop yield.

Electrical conductivity was measured in a 166-acrefield of silt loam to silty clay loam soil at the station onOctober 27, 1998, using a Veris 3100 sensor cart (Figure1). Coulters on this cart are equipped with electrodesthrough which an electrical current is passed. The Verissensor cart can measure conductivity at two depthssimultaneously, and in this study it was measured at 12- and36-inch depths.

The measurements of electrical conductivity weretaken by driving the Veris sensor cart over the fields at about 8miles per hour, logging one data point per second. Costs formeasuring soil electrical conductivity generally run between $4and $9 per acre. Soil electrical conductivity is a relatively stableparameter, and a surface map may be useful for 10 years.

Conductivity measures soil textureSoil texture affects the amount of fertilizer required to

produce optimum crop yields. Usually clay soils require morefertilizer. One outstanding feature of electrical conductivity inthis study was how well it corresponded to changes in soiltexture.

Soil electrical conductivity is depicted in the surface map inFigure 2 using 400 square-foot grid cells. The darker the shade,the higher is the conductivity. Of note is the general increase inconductivity from west to east (left to right) across the field. Thiscorresponds to an increase in heaviness ofsoil texture. The highest conductivity mea-surements in the eastern-most portion ofthe figure fairly accurately depict the denserclay soil in this area. The surface map may beused as a prescription map for fertilizerinput based on soil texture.

In a separate study, soil samples weretaken from eight specific electrical conduc-tivity zones and analyzed for soil textureand organic matter (Tables 1 and 2). Therewas very high correlation between electri-cal conductivity and clay content (0.99) andbetween electrical conductivity and organicmatter (0.99).

Figure 1. A Veris model 3100 sensor cart used to measure soil electricalconductivity at the Dean Lee Research Station. The unit is manufacturedby Veris Technologies, a Division of Geoprobe Systems, in Salinas, Kans.The coulters on the outside of the wheels measured to 36-inch depths inthis study. The coulters inside the wheels measured to a 12-inch depth.

Mapping and Interpreting Electrical Conductivityin Production Fields

Figure 2. Soil electrical conductivity can be used to create surfacemaps for site-specific applications. These are six production fields,totalling 166 acres, at the Dean Lee Research Station.

Conductivity measures nutrientsSoil nutrient concentration also affects the amount of

fertilizer needed to produce optimum crop yields. Soils with highclay and organic matter usually have higher nutrient concentra-tions because there is more total surface area for nutrients toattach to, although the nutrients may not necessarily be moreavailable to the plant. Soil electrical conductivity correspondedhighly with soil nutrients in this study.

Nutrient concentrations were determined in soil samplestaken from eight electrical conductivity zones (Table 1). Corre-lation coefficients between electrical conductivity and meanconcentrations of nitrogen, phosphorus, potassium and zincwere very high, running from 0.95 to 0.99 (Table 2). Althoughelectrical conductivity does not measure the actual concentra-tion of soil nutrients per se, the two variables did rise and fall


NW E

S


closely together. This finding paves the way for potential site-specific application of fertilizer, once base rates are established.

Conductivity measures crop yieldSoybean and corn yields for the past four years were

correlated with electrical conductivity. To do the analysis, the

Table 1. Soil test values corresponding to soilelectrical conductivity zones.

OrganicSEC Zones P K N Zn Matter Clay23.2 - 32.7 195 164 0.070 0.464 0.98 15.032.7 - 35.9 204 170 0.076 0.487 1.01 15.835.9 - 38.4 216 179 0.080 0.508 1.05 16.838.4 - 40.8 221 182 0.083 0.510 1.07 17.440.8 - 43.5 223 186 0.086 0.523 1.08 17.643.5 - 46.8 231 193 0.089 0.536 1.11 18.646.8 - 51.5 237 94 0.089 0.573 1.13 19.151.5 - 65.4 250 205 0.092 0.617 1.18 20.2

Table 2. Correlation of soil electrical conductivitywith soil test values using sample data within SECzones.

OrganicP K N Zn Matter Clay

SEC 0.99 0.99 0.95 0.99 0.99 0.99

field was divided into 400 square-foot grid cells, or rasters.Values from more than 15,000 rasters were used to derive thecorrelation coefficients in Table 3. Yield correlated significantlywith electrical conductivity each season, although correlationswere weak.

A somewhat puzzling finding was the negative correlationbetween electrical conductivity and yield in 1997. In the threeother years, conductivity correlated positively with yield. Thedifference could be explained by rainfall patterns across the fourseasons. Heavy-textured low areas of a field tend to do better

These three images are of the upper middle field shown onpage 25. The photo at left, which is of the bare field,displays the unique pattern of soil variability. It was takenin 1994.

The image at bottom left is a grid cell map created withGeographical Information System (GIS) software from soilelectrical conductivity data. Each square represents an area20 feet by 20 feet. The lighter areas are of lower relativeSEC, graduating to the darker areas of higher SEC.

The image below is a grid cell map created from the yieldmonitor data from the harvest of the 1999 corn crop. Thelighter areas are of lower corn yield, 100 to 120 bushels peracre, graduating to the darker areas of higher corn yield,from 160 to 180 bushels per acre. Note the similarities in allthree images.

Aerial Panchromatic 1994

Soil Electrical Conductivity Corn Yield 1999

Conductivity corresponds to texture, nutrients, yield


in dry years and worse in wet years. The 1997 season was fairlynormal, whereas the 1998, 1999 and 2000 seasons all haduncharacteristically hot, dry periods. The implication is that therelationship between electrical conductivity and yield will differeach season. Fertilizer rate recommendations in site-specificagriculture will be based on average response, just as in conven-tional agriculture.

Correlation of means between electrical conductivity andcorn yield in 1999 from the zones in Table 1 was much higher(0.97). Correlating means often results in higher coefficients.

Measuring conductivity shows promiseSoil electrical conductivity was found to highly correspond

to changes in soil texture, organic matter, nutrient concentra-tions and crop yield. Using electrical conductivity as a prescrip-tion map for site-specific fertilizer application appears to be apromising technology. Field experiments are now under way atAlexandria to determine crop response to specific nitrogenrates within different electrical conductivity zones. If the experi-ments are successful, producers may be able to determine site-specific fertilizer applications using electrical conductivity mea-surements on their own farms as early as the 2002 or 2003season.

AcknowledgmentLouisiana Soybean and Grain Research and Promotion Board forits support.

Table 3. Correlation of soil electrical conductivity(SEC) with crop yields using GIS raster analyses offield-scale data.

Yield1997 1998 1999 2000

SEC -0.27 0.09 0.29 0.08

Two scientists have been named to the next Experiment Station Committee on Policy (ESCOP)and Academic Programs Committee on Policy (ACOP) leadership development course, and twohave just graduated from their year’s involvement. Michael Moody, head of the Food ScienceDepartment, and Roger Leonard, a researcher at the Northeast Research Station, have beenselected for the national group. Their year’s program begins in September. James Griffin, researcherin the Plant Pathology and Crop Physiology Department, and Regina Bracy, researcher at theHammond Research Station, have just graduated from their year in the program.

The course is sponsored by agricultural experiment stations and colleges at the land-grantuniversities and involves people identified as emerging leaders from every state. The year of studyincludes seminars on leadership topics, such as communication and conflict resolution, as well asmeetings with leaders in politics and academia.

In addition to representatives from the Louisiana Agricultural Experiment Station (LAES), theLSU College of Agriculture also sends participants. Marcos Fernandez from the Animal ScienceDepartment will join Moody and Leonard in the new class. Graduating with Griffin and Bracy wasLynn Kennedy from the Department of Agricultural Economics and Agribusiness.

William H. Brown, LSU AgCenter research vice chancellor, has been the mentor for thisprogram. David J. Boethel, associate vice chancellor, has taken over that responsibility and will beworking with next year’s class. Kenneth Koonce, dean of the College of Agriculture, also serves asa mentor.

Since the program began 10 years ago, the LAES has had 20 graduates and the College ofAgriculture eight. Linda Foster Benedict

Scientists taught leadership skills

Michael Moody

Roger Leonard

Marcos FernandezJames Griffin Regina BracyLynn Kennedy

Steven H. Moore, Professor, and Maurice C. Wolcott, Research Associate,Dean Lee Research Station, Alexandria, La.


Non-profit Org.U.S. Postage

PAIDPermit No. 733Baton Rouge, LA

Louisiana Agricultural Experiment StationLouisiana State University Agricultural CenterP.O. Box 25100Baton Rouge, LA 70894-5100

Inside:

Scientists work to improve nativeplant species to protect and preserveLouisiana’s coast land.

Page 4

Scientists examine weed control incorn with herbicide-tolerant varieties.

Page 10

As urban gardening has becomemore popular, so has interest ingrowing leaf lettuce. Page 14

Growing winter wheat has multiplebenefits that can lead to an increase infarm productivity.

Page 16

Phot

o by

John

Woz

niak

rainwater from where the cows walk, which will cut down oncontamination in runoff going into streams and waterbodies.

“We will be doing more waste management research,”Beatty said.

The station has 192 cows now but will grow to about 220,with about 200 milking.

Phase I of the construction was the completely automatedmilking parlor, where 70 to 75 cows can be milked per hour.

“That’s very good for a 10-stall parlor,” Beatty said. “We cancomplete the milking shift in about four hours.”

Phase II was the feed mixing facility. See photo and moreabout dairy research on page 18. Linda Foster Benedict

Construction of the free-stall barn at the LSU AgCenter’sSoutheast Research Station is expected to be completed bySept. 1, 2001. The barn is Phase III of changes at the station thatmake it a state-of-the-art dairy research facility as well as dairyfarm.

“Our cows will be housed and fed there when they’re noton pasture, which is mainly in the summer months,” said JamesF. Beatty, the station’s resident director.

The barn is designed to be as cool as possible for thesouthern climate. Features include a high-pitched roof, a 2-footvent across the peak and fans. The barn is also designed to divert

New free-stall barn will complete Phase IIIof changes at Southeast Research Station

New free-stall barn will complete Phase IIIof changes at Southeast Research Station

summer 2001 vol. 44, no. 3 · 2016. 1. 13. · kurt m. guidry, amos bechtel, steve hague, robert...

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