Birdsfoot trefoil (Lotuscorniculatus L.) is a perenniallegume that is well adapted

to the north-central states.Individual plants can be long-livedin northern states, but typicallylive only two years in central andsouthern states. Stands may lastmuch longer due to reseeding. It isprimarily used for pasture but canalso serve as a hay crop in areaswhere poorly drained, acidic soilsmake alfalfa production difficult.Trefoil tolerates poorly drainedsoils but will not survive in areaswhere standing water persists insummer or ice sheets form in win-ter. Its branched, relatively shallowtaproot makes it less drought tol-erant than alfalfa. Unlike mostlegumes, trefoil does not causebloat in grazing animals. That fac-tor, combined with high foragequality, excellent grazing toler-ance, natural reseeding capability,and the potential for a long standlife, make it an ideal pasturelegume.

Mature plant height variesfrom 12 to 30 inches depend-

ing on the variety and thedegree of support provided

by grasses or other more uprightspecies included in the stand.Birdsfoot trefoil plants are fine-stemmed and tend to lodge easily.Each leaf has five leaf-like stipules,three attached at the end of thepetiole and two attached at itsbase. Plants produce many brightyellow to orange-yellow flowers inclusters of two to eight. Eachflower can produce a slender seed-pod about 1-inch long which turnstan to dark-brown as the podmatures. The pods radiate awayfrom the flower stalk like the toeson a birdÕs foot; hence the name.Birdsfoot trefoil requires a daylength of about 16 hours to initiateflowering. Plants continue toflower over 3 to 8 weeks until fall.The ripened pods shatter, naturallydispersing the seed.

Variety selectionBirdsfoot trefoil varieties used inthe north-central states can be cate-gorized into three general groups:(1) the prostrate or grazing typerepresented by varieties such asAU-Dewey, Dawn, Empire,Fergus, and Leo; (2) the erect orhay type which includes the vari-eties Georgia-1, Maitland, andViking; and (3) the semi-erect typewith varieties such as Mackinawand Norcen. The prostrate type of

Birdsfoot trefoilfor grazing and harvested forageDan Undersander, Lou Greub, Richard Leep, Paul Beuselinck, John Wedberg, Dick Smith, Keith Kelling,Jerry Doll, Dennis Cosgrove, Craig Grau, Steve Peterson, Mark Wipfli, and Jim English

North Central RegionalExtension Publication 474

Table 1. Characteristics of selected birdsfoot trefoil varieties

Variety Origin Plant typea Winterhardinessb Performance

*AU-Dewey Auburn University semi-erect low to moderate adapted to southeastern states

*Carroll Iowa State University semi-erect to erect; high excellent seedling vigor; yields are matures earlier than as good as or better than EmpireEmpire

*Dawn Agricultural Research semi-erect; fine moderate to high good yields; excellent fall growth; Service/USDA, stemmed; late maturity good grazing tolerance; adapted to University of Missouri southern Corn Belt

Empire Cornell University prostrate; fine stemmed; high good tolerance to grazing; adapted late maturity to wetter soils; harder to establish

than Viking

*Fergus University of Kentucky semi-erect; matures moderate adapted to southeastern states; earlier than Empire good grazing tolerance

*Georgia-1 University of Georgia semi-erect; early maturity moderate adapted to southeastern states

Leo MacDonald College, semi-erect to erect; moderate to high very good seedling vigor; Canada matures slightly earlier yields are as good as Viking

than Empire

*Mackinaw Soil Conservation semi-erect; fine stemmed; high slightly better seedling vigor than Service, USDA late maturity Empire; yields are better than

Empire—similar to Norcen and Viking

Maitland University of Guelph, erect; hay type moderate to high above-average seedling vigor; yields Canada slightly less than Viking

Norcen North Central States semi-erect to erect; high good yields; best winterhardiness matures midway between Viking and Empire

Viking Cornell University erect; hay type; earliest moderate excellent seedling vigor; good yields; maturity good regrowth

*Proprietary varietyaThis table compares variety maturity against Viking and Empire, the maturity extremes. Viking matures about 10 days earlier than Empire; all others mature some-

where in between.bModerate to high winterhardiness is adequate for northern states.

Birdsfoot trefoil2

trefoil is particularly suited forprolonged grazing because of itslow profile. However, all the vari-eties listed here can be used forgrazing. The erect types better suithay, haylage, and green-chopproduction. They begin springgrowth and flowering earlier thanprostrate types, but are less winter-hardy in northern states.

Empire and Viking, the first com-mercial varieties released in theUnited States, were developed inNew York in the 1930s. While bothvarieties are still available, look fornewer varieties with improvedseedling vigor and resistance todiseases (see table 1 for varietycharacteristics). For example,Dawn was selected from Empire,but has improved resistance to

root and crown diseases; Maitlandand Mackinaw were selected forimproved seedling vigor; Leo wasdeveloped with a high degree ofwinterhardiness; Norcen wasdeveloped with a diverse geneticbackground to broaden its adap-tion to conditions found in thenorth-central states; Georgia-1 wasselected for tolerance to acid soils;and AU-Dewey and Fergus were

developed for persistence inhumid pastures of the southernCorn Belt. New varieties beingdeveloped by plant breedersshould improve establishment,disease resistance, and persistence.

Purchase certified seed to ensurethat you are buying improvedvarieties. Imported trefoil seed hasunpredictable performance. Inparticular, seed from SouthAmerica often lacks winterhardi-ness. Use varieties recommendedby your state Extension service fortop persistence and yield.

Establishment and seeding yearmanagementLIME AND FERTILIZER NEEDS

Fertility needs are best determinedby soil testing. Apply lime and fer-tilizer according to soil test recom-mendations. Trefoil tolerates acidsoils better than red clover oralfalfa, but benefits from limingthe soil to a pH of at least 6.0.When lime is needed, apply 6 to12 months before seeding andwork it into the soil. If no-till seed-ing trefoil into sod, apply lime twoyears before seeding. Since thislime wonÕt be incorporated, usethe smallest particle size avail-ableÑ80 to 90 grade or finer.Select liming material based on theaglime neutralizing index.

Where soil nutrient levels are low,especially for phosphorus, applyfertilizer before seeding and incor-porate the fertilizer with tillage.Research on trefoil fertility has notshown responses to broadcast orbanded fertilizers at plantingexcept for a small amount of nitro-gen (about 30 lb/a) on soils withless than 2% organic matter.

Trefoil requires a specific strain ofRhizobium bacteria to fix nitrogen.To ensure the presence of theneeded Rhizobium, purchasepreinoculated seed or treat theseed using commercial inoculumavailable from seed dealers.Inoculum is critical on land wheretrefoil has never been grown before.If treating seed, use a stickerÑanadhesive compound to attach theRhizobium to the seedÑand thor-oughly mix inoculum and seedbefore seeding. If trefoil plants areyellow and lack vigor, check rootsfor small growths called nodules.The absence of nodules may indi-

cate poor inoculation or excessive-ly acid soils.

PURE STANDS

Pure trefoil stands can be grownfor hay and used with pastures ofother species to provide uniformlyhigh-quality forage. Althoughpure stands offer high-quality for-age and hay, they tend to thin outmore rapidly than mixed stands,increasing weed problems.

The fall before planting a purestand, control perennial weeds,such as quackgrass, usingRoundup (glyphosate). In thespring, prepare a seedbed withappropriate tillage methods toprovide a firm seedbed, free ofweeds and clods. Then eitherapply a preplant-incorporated her-bicide or seed without a herbicideand control weeds after trefoilemergence.

Plant when soil temperaturesreach 50¡F at a 4-inch depth. Seedat 8 lb/a into a conventionallytilled seedbed using a special for-age-seeding drill, a broadcastseeder, or a grain drill equippedwith a legume seeding attachment.If the seeding implement is notequipped with presswheels, use acultipacker or roller after planting.When seed is sprayed or blownonto the surface of a preparedseedbed, cultipack to cover theseed and ensure good soil-seedcontact to enhance germinationand seedling growth.

Trefoil may be seeded with asmall-grain companion crop (usu-ally oats or barley) to prevent ero-sion and provide weed control.Use a relatively short small-grainvariety and seed at 1 to 1.5 bu/a.The short-stature small grain andlow seeding rate will reduce com-petition to the birdsfoot trefoil.Remove the companion crop by

Birdsfoot trefoil 3

Figure 2. Comparison of prostrate(left) and erect (right) varieties.

Figure 1. Trefoil from SouthAmerica often has very poorwinterhardiness.

grazing or machine harvestingwhen the small grain is in the bootstage. Control grazing carefully tominimize damage to the seedlingtrefoil plants. Monitor the standfor late-season weed growth (orregrowth of the oats) and clip ifnecessary.

On land where erosion is minimal,direct seeding with a preplant-incorporated herbicide is pre-ferred. Seeding without a herbi-cide or companion crop should belimited to pastures or fields thathave low weed pressure.

Several herbicide options aredescribed below.

■ Balan (benefin) is a preplant-incorporated herbicide thatcontrols annual grasses andsome annual broadleaf weeds.Balan must be incorporated toa depth of 2 to 3 inches.Incorporation may be delayedfor up to eight hours, butprompt incorporation is best.Incorporate with a disk orother suitable implement andwork in two different directions.Do not use Balan if plantingforage grasses as they will bekilled by Balan. Injury fromBalan at recommended rates isgenerally not a problem.

■ Butyrac (2,4-DB) is a post-emergence systemic herbicidethat controls many annualbroadleaf weeds but is weakon mustards and smartweedand will not control grasses. Itpartially suppresses perennialbroadleaf weeds. Apply whenseedling weeds are no morethan 3 inches high. Correct tim-ing is important as control isless effective on larger weeds.Check the label for specific

rates according to weed speciesand size. Treated forage cannotbe harvested or grazed for60 days after application.

■ Eptam (EPTC) is a preplant-incorporated herbicide thatcontrols annual grasses andmany broadleaf weeds. Eptammust be thoroughly incorpo-rated to a depth of 2 to 3 inches.Incomplete incorporation mayresult in streaking which cancause trefoil injury or poorweed control. Incorporate witha disk or other suitable imple-ment, working the field in twodifferent directions. Do not useEptam if planting forage grass-es as they will be killed byEptam.

■ Poast Plus (sethoxydim) is aselective post-emergence sys-temic herbicide that controlsmost annual grasses present intrefoil. Apply when annualgrasses are 3 to 8 inches tall.Grasses must be actively grow-ing for best results. Poast Plusgives some suppression ofquackgrass. It can also be usedto kill an oat or barley covercrop once the crop is no longerneeded for erosion control andweed displacement.

Trefoil can be harvested 7 daysafter Poast Plus treatment if theforage is green chopped orensiled and 20 days after treat-ment if harvested as dry hay.Use Poast Plus to control vol-unteer small-grain seedlingsthat emerge following wheat oroat harvest. Treat when cerealsare 2 to 4 inches tall and beforetillering has started.

Poast Plus and 2,4-DB can betank mixed and applied tonewly seeded trefoil to treat a

mixture of grass and broadleafweeds. However, it is safer andmore effective to apply 2,4-DBfirst and apply with Poast Plus7 or more days later. With atank mix, the possibility ofcrop injury increases becausethe oil concentrate increases2,4-DB uptake. Use the rate ofproduct as indicated for theweed species present. Do notuse any additives other thanthe crop oil concentrate for thistank mix. Treated forage can-not be harvested or grazed for60 days following the 2,4-DBapplication.

GRASS-TREFOIL ANDLEGUME-TREFOIL MIXTURES

Birdsfoot trefoil is best seededwith a perennial companion grasswhich will use the nitrogen fixedby the trefoil and fill vacant areasin the stand where weeds wouldotherwise grow. Trefoil seedlingsare small, slow to establish, andcannot tolerate much competition.Competition for light with thegrass canopy is a major factor lim-iting successful birdsfoot trefoilestablishment with grasses.Therefore, competition betweentrefoil and grasses or weeds mustbe controlled. Kentucky bluegrassand timothy are good companioncrops because they grow moreslowly than orchardgrass, smoothbromegrass, and tall fescue. Themore aggressive grasses can resultin uneven grazing and excessivecompetition but can be compatiblewith appropriate management. Asmall-grain companion crop(described in ÒPure StandsÓ) maybe seeded with the grass-trefoil orlegume-trefoil mixture to reducethe potential for erosion duringestablishment.

Birdsfoot trefoil4

Seeding trefoil with other legumesis generally less desirable thanmixing with grasses. Red cloverand alfalfa are very competitivebut could be used at low seedingrates. White and alsike clovermight be desirable in a wildlifemix.

Keep the seeding mixtures simple.Table 2 suggests recommendedseeding rates for various grass-trefoil mixtures. Plant seeds in afirm soil with good seed-soil con-tact as described above.

SEEDING METHOD FORPASTURE IMPROVEMENT

No-till seeding into sod. For pas-ture renovation or for new seed-ings on sloping land subject to ero-sion, no-till techniques are general-ly used. Test soil and apply lime, ifnecessary, one to two years beforeseeding (apply lime earlier onheavier soils). Check the field for

biennial and perennial broadleafweeds, such as thistles, and controlthem with herbicides for at leasttwo years before seeding.Productive stands can be no-tillestablished by any of four methods:

■ Roundup (glyphosate) is a non-selective herbicide that can beused to control existing vegeta-tion. Treat fields in the fallprior to no-till seeding.Roundup is recommendedwhere the sod is primarilyhighly competitive perennialssuch as quackgrass or smoothbromegrass. If applied in thespring, treat when grasses are6 to 8 inches tall and wait atleast three days after sprayingRoundup before planting. Donot graze pastures treated withRoundup for 8 weeks afterapplication.

■ Gramoxone Extra (paraquat) is acontact herbicide and can beused on early season growthfor temporary burn down.Treat only closely grazed ormowed pastures that are nomore than 2 to 3 inches tallwhen sprayed. Bluegrass andother perennial species willrecover in 3 to 5 weeks. Plantwithin 1 to 2 days after herbi-cide application using a no-tilldrill or grain drill heavyenough to place the seed 1Ú4 to1Ú2 inch deep. If grain drills areused, press wheels are recom-mended. Do not graze pasturestreated with Gramoxone Extrafor 6 weeks after herbicideapplication.

■ Overgraze or mow in the latesummer and fall prior to seed-ing to reduce competition fromsod growth. In the spring, seedearly and suppress sod growthby grazing after seeding butbefore trefoil emergence.Grazing must be intensive sothat grass is as short as possi-ble at seedling emergence.

■ Do a controlled burn of winter-killed residue in late winter orearly spring to effectivelyreduce early grass competitionin established grass-trefoil insouthern states of the north-central region. Prescribedburning temporarily injuresand slows spring growth of thegrass. Burning also reducesthatch and residue, encourag-ing the germination and estab-lishment of new trefoilseedlings.

Frost seeding. This seedingmethod relies on repeated freezingand thawing to incorporate theseed into the soil. This low-costmethod is less reliable than seed-ing with a drill. Research hasshown that grass sod suppressionis vital to successful frost seeding.This can be accomplished withseveral clippings or intensive rota-tional grazing the prior season.Seed in early spring when theground is still frozen. Fall or over-winter seeding is often less effec-tive than spring seeding due to theamount of seed eaten by wildlifeand lost with runoff during thaws.Broadcast seed by any methodincluding mixing seed with fertil-

Table 2. Recommended seedingrates for grass-trefoil mixtures

Rate (lb/a) of Seeding pure live seeda

mixtures Grass TrefoilBirdsfoot trefoil — 8(pure stand)

Kentucky bluegrass 2 6Orchardgrass 2 6Smooth bromegrass 5 6Tall fescue 4 6Timothy 3.5 6

aPure live seed = % germination x % purity

Birdsfoot trefoil 5

izer. For improved trefoil stands,suppress grass growth after seed-ing using the methods describedabove for no-till seeding.

MANAGING GRASS COMPETITION

Managing competition fromaggressive grasses by grazing orhaying practices is key to success-ful establishment and retention ofbirdsfoot trefoil in mixed stands.These practices include early hay-ing, early and close grazing, orintensive, rotational grazing. Grazebirdsfoot trefoil stands in the seed-ing year whenever companioncrops or regrowth of grasses in sodseedings reaches a height of 8 to10 inches to prevent excessivecompetition. As table 3 indicates,cutting during establishment yearor using a herbicide to controlgrass growth increased the trefoilyield in succeeding years. Not cut-ting, as many farmers do to Ògoeasy on the new seedingÓ actuallyreduced trefoil in the stand due tocompetition from the grasses.

Grazing during the establishmentyear should be done quickly andintensively, being carefully con-trolled to prevent damage to thesmall trefoil seedlings.

Alternatively, mow or greenchopthe companion crop or competitivegrasses for forage if field condi-tions permit. Do not graze or clipafter August 15 in the seedingyear. Grazing after this date great-ly reduces the standÕs ability tooverwinter.

Production managementFERTILIZER NEEDS

Research shows that soil test phos-phorus of about 15 ppm (parts permillion) and potassium of about90 ppm appear adequate for aver-age yield levels (2 to 3 t/a dry mat-ter). These levels are lower thanrecommended for alfalfa but aresimilar to those for red clover.Where soil tests are below theselevels annual broadcast applica-tion with phosphate and/orpotash is recommended.

Harvested trefoil forage usuallycontains about 0.20 to 0.40% phos-phorus and 1.50 to 3.20% potassi-um. Each ton of dry matter har-vested removes about 15 poundsof phosphate (P2O5) and 55 to60 pounds of potash (K2O). Theserates are similar to those for alfalfa.

Trefoil has a high requirement forsulfur, perhaps due to its ability toproduce high protein levels. It alsohas a high requirement for boron,often showing deficiency symp-toms when alfalfa does not.

Trefoil is apparently able toexclude some potentially toxicmicronutrients. In acid soils(pH<6.0), trefoil has tissue concen-trations of manganese, iron, andaluminum that are 50 to 60% lessthan the levels found in alfalfagrown under the same conditions.

Manure can be used to fertilizetrefoil and will reduce the need foradding commercial fertilizer. Itmay be advantageous to harrow apasture immediately following agrazing period to break up andspread the manure droppings.This also will reduce the unevengrazing that often occurs whenanimals avoid grazing lush plantsgrowing near the manure.Harrowing is more beneficial atlower animal stocking rates (e.g.,less than 30,000 lb animal weightper acre in paddock of rotation).Manure applied to supply phos-phorus and potassium also con-tains nitrogen which is used byboth the grasses and trefoil.Manure applications also willstimulate grasses in the stand andmay introduce weeds.

ANIMAL PERFORMANCE

Birdsfoot trefoil is an ideal pasturespecies. Inclusion of trefoilimproves both average daily gainand gain per acre (figure 3) com-pared to pure grass pastures. It hasexcellent feeding value, with-stands grazing better than anyother legume except white cloverand annual lespedeza, can be veryproductive, and has the potentialfor a long stand life. TrefoilÕs excel-lent quality and the absence of

Table 3. Yield of frost-seeded red clover and birdsfoot trefoilduring the second and third years of growth in Michigana

———————Hay yield (t/a)—————————Red clover—— —Birdsfoot trefoil—

Treatments 2nd year 3rd year 2nd year 3rd year

0 cuts 0.5 1.1 0.3 1.92 cuts 2.7 1.0 1.4 2.84 cuts 3.7 0.9 1.6 2.8Herbicide 3.8 1.4 1.9 3.3

aSeeded into three grass swards that were suppressed with a herbicide or by cutting. Dataaveraged over three grass sods (smooth bromegrass, reed canarygrass and orchardgrass).

Source: Tesar, 1983

Birdsfoot trefoil6

bloat potential, probably due tothe presence of tannin compounds,make it a valuable legume for allanimals, including grazing milkcows. Farmers occasionally reportthat livestock must first becomeaccustomed to the taste of the

plants before they will graze itreadily, but consumption prob-lems are not common.

Digestibility of trefoil is similar toalfalfa at comparable stages ofmaturity except that trefoil main-

tains high quality into later stagesof flowering (figure 4). The levelsof nitrogen, phosphorus, potassium,calcium, and other nutrient ele-ments in birdsfoot trefoil forageare very similar to those in redclover and alfalfa. Early or mid-

Birdsfoot trefoil 7

birdsfoot trefoilimproved grass plus NPKunimproved grass

2

1

Iowa Wisconsin (1967–1968)

Wisconsin (1972–1974)

aver

age

daily

gai

n (l

b/da

y)500

400

200

100

300

Iowa Wisconsin (1967–1968)

Wisconsin (1972–1974)

beef

gai

n (l

b/a)

Figure 3. Animal performance in Iowa and Wisconsin on birdsfoot trefoil pastures.

early season growth

70

65

60

55

50

75

birdsfoot trefoil

alfalfa

May 11 May 25 June 7

in v

itro

dig

esti

bilit

y (%

)

June 21

✖ ✖

✖✖

●

●

●●

vegetativevegetative

30% bud16% bud

6% flower2% flower

alfalfa —trefoil —

2% pods10% pods

late season growth

70

65

60

55

50

75

birdsfoot trefoil

alfalfa

July 26 August 17 September 6vegetativevegetative

57% flower61% pods

22% pods64% pods

alfalfa —trefoil —

in v

itro

dig

esti

bilit

y (%

)

●

●

●

✖

✖

✖

Figure 4. Comparison of in vitro digestibility of Viking birdsfoot trefoil and alfalfa duringearly and late season growth periods. Source: Buxton, Hornstein, Wedin, and Marten, 1985.

Birdsfoot trefoil8

3 4 6 8 10 12

1000

2000

3000

4000

5000

6000

7000 70

65

60

55

✖

●

✖

✖✖

✖

✖

●

● ●

●

●

dry

mat

ter

yiel

d (l

b/a)

harvest interval (weeks)

in v

itro

dig

esti

bilit

y (%

)dry matter yield (LSD=1280)

in vitro dry matter digestibility (LSD=5)

Figure 5. Dry matter yield and in vitro digestibility of trefoil harvestedat different intervals at Griffin, Ga. Source: Hoveland et al., 1990.

April May June July August Sept. Oct.

10

20

30

40

carb

ohy

drat

e st

ora

ge (

%)

cut

cut

cut

0

alfalfa birdsfoot trefoil

Figure 6. Comparison of carbohydrate storage in Empire birdsfoottrefoil and Vernal alfalfa in Iowa. Source: Greub and Wedin, 1971.

season trefoil stockpiled for late-summer grazing maintains a high-er quality than most other speciesused for such a purpose. However,forage stockpiled for over 6 to8 weeks may have greatly reducedyields and lower forage quality(figure 5).

GRAZING FOR STAND PERSISTENCE

Established trefoil, especially thesemi-erect type, begins growthlater in the spring than most alfalfaand clover varieties. Allow animalsto graze pure stands when firstflowers appear. Earlier grazing ofpure stands reduces trefoilÕsgrowth potential for the remainderof the season. Graze mixed standscontaining faster growing and ear-lier maturing grasses (such asKentucky bluegrass or orchard-grass) first to maximize foragequality and control competitionfrom the grasses. In fact, mixedstands may need to be grazed veryearly (through mid-May) to reducerhizoctonia in birdsfoot trefoil andthen allowed to flower and pro-duce seed for reseeding.

Birdsfoot trefoil does not undergoa cyclic utilization and storage ofroot and crown carbohydrates asdo alfalfa and clovers (figure 6) innorthern states (though cyclic vari-ation has been reported inGeorgia). Trefoil stands benefitfrom leaving some stubble andresidual leaf area after cutting,rotational grazing, or continuousgrazing. Stands regrow significant-ly better from 3-inch stubble thanfrom 1.5-inch stubble becauseregrowth comes only from axillarybuds on the stems (table 4). Trefoilharvested at 3 inches has leaf areaequal to approximately 40% of theground area. That leaf area pro-vides energy for faster regrowththan closer clipping or grazing.However, as shown in table 4,leaving a 4.5-inch stubble heightdid not increase the useable drymatter yield. Prostrate varietiesmay be grazed shorter, to 1.5- to2-inch stubble height, becausemore stem length remains uneatencompared with the upright types.

While trefoil can be defoliated morefrequently than alfalfa, studiesshow that trefoil yield decreasesthe more frequently it is harvested.Increasing the harvest interval

from three weeks to six weeksincreases forage yields, rootweights, and the next seasonÕsgrowth potential. A fall rest periodis critical to trefoilÕs ability to over-winter. Dry matter availability andforage quality must be balancedagainst the plantÕs need for foodreserves stored in the fall. Trefoilmay be even more sensitive thanalfalfa to fall grazing becausetrefoil stores fewer carbohydrates,making it more vulnerable tosevere winter injury. If you mustgraze after a killing frost or afterthe onset of plant dormancy, besure to leave several inches ofstubble for overwintering protec-tion, especially in areas of littlesnow cover.

Various grazing systems allowtrefoil to regrow and reseed. Theserange from frequent, incompletedefoliation under continuous graz-ing with low stocking rates, tointensive, carefully managed rota-tional grazing. Rotational grazingmakes the most efficient use of theforage. Productive managementsystems carefully match stockingrate and grazing duration to theavailability of forage which variesduring the season due to rainfall,temperature, and sunlight condi-tions. Overgrazed trefoil will beunproductive for the remainder ofthe season and may be more sus-ceptible to winter injury. Whentrefoil is severely defoliated duringthe warmer part of the summer itis more susceptible to root andcrown rot diseases which can takea heavy toll on the stand.

To maintain a long-lived and pro-ductive stand, allow birdsfoottrefoil to flower and set seed atsome point during the growingseason. Reseeding is particularlyimportant in years when the stand

Birdsfoot trefoil 9

Table 4. Regrowth yield of Empire birdsfoot trefoil defoliated tothree stubble heights

Stubble Net dry matter yield (t/a)height Residual after 7 weeks regrowth(inches) LAIa Early June Mid-July

4.5 1.1 2.11* 0.83*3.0 0.4 2.05* 0.78*1.5 0.1 1.76 0.53

*Values within a column followed by an asterisk are not significantly different at P=.05.aResidual LAI = leaf area index after cutting. LAI is expressed as units of leaf area per unit of land area.

Source: Greub and Wedin, 1971

needs to be thickened. The need ismore frequent in the south wherestands thin faster due to increaseddisease pressure.

In summary, graze pure birdsfoottrefoil stands two to three timesannually with the first cycle begin-ning at first flower (or later ifreseeding is desired) and with suc-ceeding grazing cycles followingin approximately 35 to 40 days.The last grazing should end inmid-August to rebuild rootreserves for overwintering.Recommendations are the samefor grass-legume mixtures exceptthat an early, additional grazing(when grass is 6 to 8 inches tall)may be desirable to reduce earlyseason competition and rhizocto-nia prevalence.

HARVESTING FOR HAY

Trefoil can be harvested for hay orhaylage. However, because trefoilyields less than alfalfa, it is grownfor hay primarily on soils wherealfalfa is poorly adapted. The man-agement principles discussed ear-lier for grazing trefoil also apply tousing it for hay. Harvest trefoil atearly flower for optimum yieldand quality. The main disadvan-tage for hay harvesting is the diffi-culty in getting it sufficiently dryto bale without excessive leaf shat-ter. Trefoil has small, thin leafletswhich dry more rapidly than thestems, making timing of the balingeven more critical than for otherlegumes to minimize shatteringlosses. Two cuttings should bepossible north of the line shown infigure 7 and three cuttings else-where. Leave a 2- to 4-inch stubbleheight to enhance regrowth fromthe lower stems.

Weed managementMaintain a weed-free standthrough proper grazing or harvest-ing management and through ade-quate fertilization and liming.However, even under good man-agement, thistles, mullein, or otherbiennial or perennial broadleafweeds may appear in pastures.Clip when the weeds are in thebud or early bloom stage. Morethan one clipping per season maybe required.

Herbicide use in established standsis generally limited to spot treat-ment to control serious perennialweeds such as Canada thistle orbrush. If quackgrass or annualgrasses are a problem, use PoastPlus (sethoxydim) to suppressthem. This treatment may be bene-ficial if the trefoil has been weak-ened by overgrazing, winterinjury, or other stresses that allowgrass weeds to encroach. ConsultExtension publications in yourstate for specific weed managementsuggestions and grazing restrictioninformation of herbicides.

Birdsfoot trefoil10

2 cuttings

3 cuttings

Figure 7. Number of birdsfoot trefoil hay cuttings for thenorth central states.

DiseasesFungal diseases appear to imposethe most important limitations tobirdsfoot trefoil adaptation andpersistence. It can behave as a long-lived perennial in the northernnorth-central states, but can actmore like a biennial when grownin the southern states. The lack ofpersistence appears to be mainlydue to a disease complex common-ly referred to as a root and crownrot.

Foliar and stem diseases. Manyfungal pathogens can affect thefoliage and stems of trefoil. Thesepathogens include species ofStemphylium, Rhizoctonia, Phomopsis,Uromyces, Curvularia, and Diaporthe.Of these, Stemphylium loti andRhizoctonia solani can cause exten-sive losses of foliage and entireshoots, particularly in warm andhumid regions. Symptoms ofinfection by S. loti consist of red-dish-brown lesions on leaflets andcankers on stems. Infected leafletscommonly drop from the plantprematurely. Plants infected by R.solani have blighted leaflets andstems. No chemical controls areavailable for these diseases, how-ever, losses can be minimized by

grazing or harvesting beforesevere defoliation occurs.Additionally, because lower leavesare affected most severely by thesepathogens, time grazing and har-vesting carefully to maximize theamount of healthy foliage remain-ing on stubble which will con-tribute to plant regrowth.

Root and crown rot. The firstsymptom of root rot infection isthe failure of plants to resumegrowth after harvest. Root decayusually begins within an inch ofthe soil line, with the color of theinfected tissue varying from tan toreddish brown or black. Tissuesare usually infected by combina-tions of plant pathogenic fungiincluding species of Fusarium,Mycoleptodiscus, Pyrenochaeta,Rhizoctonia, or others.Environmental factors affect theincidence and severity of root andcrown rot. These factors includesoil moisture, drainage, air andsoil temperature, nutrients, standdensity, crop rotation, frequencyand height of cutting, insect injury,and previous invasion by virusesand nematodes. The effects ofthese diseases can be reduced bymanagement practices that allowfor reseeding.

Root-lesion nematode(Pratylenchus penetrans). Thisparasitic nematode is a microscop-ic worm that feeds on root hairs,feeder roots, and nitrogen-fixingnodules on legumes. It is a severepest of trefoil, especially on lightersoils. Root-lesion nematodesreduce the plantÕs ability to takeup soil nutrients and fix nitrogen.Nematodes can cause stand estab-lishment failures. When root-lesion nematodes and Fusariumare both present, they reduce yieldand can cause stand loss.

Seedling diseases. Pythium speciescause seedling diseases that canresult in poor establishment ofstands. Metalaxyl, formulated asApron and applied as a seed treat-ment, is an effective fungicide forPythium control.

Birdsfoot trefoil 11

InsectsFORAGE-PRODUCTIONPESTS

Potato leafhopper is a potentialpest of trefoil. Potato leafhoppersare mid- to late season pests thatmigrate north from southern areas.The small (1Ú8 inch), green, wedge-shaped insects move rapidly andare nearly impossible to see with-out first catching them in a sweepnet. Leafhoppers suck sap fromplants. Severely damaged plantsmay be stunted. Informationregarding the effects of leafhopperfeeding on the yield and quality oftrefoil are limited. In a 1989University of Wisconsin study,birdsfoot trefoil leaves did notshow the classic ÒhopperburnÓsymptoms that were present onthe leaves of alfalfa in adjacentplots. Adult potato leafhopperpopulations peaked approximatelytwo weeks later in trefoil than inalfalfa, indicating slower develop-ment of leafhoppers feeding ontrefoil. Populations were also high-er in the alfalfa plots than in thetrefoil plots.

Plant bugs. Plant bugs are suckinginsects that feed on plant sap fromvarious plant parts, includingstems, buds, flowers, and develop-ing seeds. Plant bug populationsdecline naturally between genera-tions towards the end of July sothe crop can often recover.

Adult alfalfa plant bugs are 3Ú8-inchlong, light green, and have relative-ly long antennae which becomewider and reddish-brown at thetip as the adult matures (figure 8).Nymphs are green with red eyes.Alfalfa plant bugs overwinter aseggs in trefoil and other plantstems. Nymphs appear aroundmid-May and adults are common

by early July. There are two gener-ations per year in the upperMidwest. The second cycle beginsin mid-July, with adults layingeggs in September.

Tarnished plant bug (also calledlygus bug) adults are 1Ú4-inch long,brown to yellowish-brown, with aV-shaped marking in the middle ofthe back (figure 9). Nymphs aregreen with four to five black spotson the back. Tarnished plant bugsoverwinter as adults in andaround trefoil fields. There are twogenerations per year in the upperMidwest with the first generationof adults appearing in early May

and the second in July. These plantbugs are most abundant in lateJuly and early August.

Forage losses from plant bugs areseldom large enough to justify pes-ticide application.

Spittlebug nymphs are soft,orange or green bugs that can befound in white spittle masses inleaf axils and stems. Spittlebugssuck plant sap and excrete frothyand sticky masses. Spittlebug feed-ing can stunt plants, but seldomwarrants control.

Grasshoppers feed on trefoil butseldom cause economic damage.

Birdsfoot trefoil12

Figure 9. Tarnished plant bug.

Figure 8. Alfalfa plant bug.

second instarnymph

adultfifth instarnymph

second instarnymph

adultfifth instarnymph

3⁄8-inch

1⁄4-inch

SEED-PRODUCTION PESTS

Trefoil will normally producemore than adequate seed for nat-ural reseeding. However, twokinds of insect pests reduce yieldfor commercial birdsfoot trefoilseed producers: plant bugs thatfeed on buds and developingseeds and the seed chalcid, a seed-feeding wasp.

Plant bugs. In addition to thealfalfa plant bug and the tarnishedplant bug described above, thePlagiognathus plant bug can alsocause seed losses. These adults are1Ú8-inch long and light green.Plagiognathus (figure 10) is similarto the alfalfa plant bug, but smaller.The alfalfa plant bug andPlagiognathus overwinter in theegg stage in trefoil and other plantstems. Nymphs appear on trefoilaround mid-May and adults arecommon by early July. Unlike thealfalfa plant bug, which has twogenerations per year, thePlagiognathus has only one genera-tion per year. Adults usually layeggs and die by August. Alfalfaand Plagiognathus plant bugs over-winter in trefoil stems and becauseof this they are often abundantduring bud development.

Feeding by plant bugs causes budsand flowers to drop and seeds toshrivel. Bud blasting is the mostserious type of injury produced.High populations can delay blos-soming. However, because trefoilproduces buds throughout the sea-son, bud blasting early in the sea-son does not necessarily reduceseed yield.

Scouting. Scout fields for plantbugs when trefoil is in the earlybud stage. Use a standard 15-inch-diameter sweep net and take

5 groups of 20 sweeps for each40 acres. Place the swept materialin plastic bags and freeze them tokill insects. Too many bugs escapewhen counting takes place in thefield. Calculate the plant bugequivalent (PBE) using the chartabove and treat if the PBE exceeds100 per 20 sweeps.

Control. Early spring burning sub-stantially reduces levels of plantbugs. Burn stubble as soon as the

snow melts and soil begins to dry.Be sure to obtain a burning permitand follow all safety guidelines.Spray when fields have more than100 PBE per 20 sweeps. A singleapplication during the bud stagewill provide adequate plant bugcontrol. Multiple applications donot provide additional protectionand will harm natural enemies ofplant bugs. Do not apply insecti-cides to blossoming fields to avoidkilling honey bees.

Figure 10. Plagiognathus plant bug.

Birdsfoot trefoil 13

Table 5. Determining plant bug equivalents

Count per Plant bugPlant bugs 20 sweeps equivalents

1. Alfalfa plant bug nymphs _______ x .75 = ________

2. Tarnished plant bug nymphs _______ x .75 = ________

3. Plagiognathus nymphs _______ x .50 = ________

4. Alfalfa plant bug adults _______ x .50 = ________

5. Tarnished plant bug adults _______ x .50 = ________

6. Plagiognathus adults _______ x .50 = ________

Total plant bug equivalents (PBE) ________(add lines 1–6)

second instarnymph

adultfifth instarnymph

1⁄8-inch

Seed chalcid. The adult trefoilseed chalcid is a tiny black wasp,approximately 1Ú16 inch in lengthwith a hump-backed appearance.The female lays eggs in develop-ing seeds and one larva developsinside one seed. Larvae are white,legless grubs hidden inside trefoilseeds. Adults appear when trefoilpods become abundant, usually inmid-July. There are usually twogenerations of seed chalcids eachyear. The insect overwinters as amature larva inside a hollowed-out trefoil seed.

Tiny holes in seed pods indicatethat seed chalcids have emergedfrom seeds within the pod. Theseed chalcid destroys the seed ituses as a host. Damage from thisinsect ranges from 1% to 40%. Seedfields that have been in productionfor many years are more likely tohave higher seed chalcid levelsthan newer fields.

Control. Insecticides and springburning are largely ineffectiveagainst seed chalcids. The follow-ing practices will minimize dam-age from this insect:

■ Harvest as early as possible toavoid pod shattering andspread of infested seed.

■ Harvest seed fields regardlessof yield. Seed left in the fieldwill result in higher levels ofseed chalcid the next year.

■ Burn or bury chaff and lightseed.

■ Destroy or clip roadside trefoilnear seed fields.

■ Apply insecticides for plantbugs when trefoil is in theearly bud stage to avoid killingnatural enemies of the seedchalcid.

■ Make an early hay cutting todelay pod set. This practicewill lessen the amount ofinfested seed, but it also mayreduce seed yield.

■ If seed chalcid damage is likelyto be high because of severalyears of seed production, har-vest hay for the entire growingseason. Not allowing seed toset will break the cycle of theinsects.

Birdsfoot trefoil14

North Central Regional Extension Publications are subject to peer reviewand prepared as a part of the Cooperative Extension activities of thethirteen land-grant universities of the twelve North Central States, incooperation with the Extension ServiceÑUnited States Department ofAgriculture, Washington, D.C. The following states cooperated in makingthis publication available:

University of IllinoisAg. Publication Office69 Mumford HallUrbana, IL 61801(217) 333-2007

Iowa State UniversityPublications DistributionPrinting and Publishing Bldg.Ames, IA 50011-3171(515) 294-5247

Michigan State UniversityBulletin Office10B Ag HallEast Lansing, MI 48824-1039(517) 355-0240

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*University of WisconsinCooperative Extension PublicationsRm. 245, 30 N. Murray St.Madison, WI 53715-2609(608) 262-3346

For copies of this and other North Central Regional Extension publica-tions, write to: Publications Office, Cooperative Extension Service, in careof the university for your state listed above. If they do not have copies oryour state is not listed above, contact the publishing state (Wisconsin).

Birdsfoot trefoil 15

Authors: Dan Undersander is associate professor and Jerry Doll is profes-sor of agronomy, John Wedberg is professor of entomology, KeithKelling is professor of soil science, Craig Grau is professor of plantpathology, University of Wisconsin-Madison and University ofWisconsin-Extension, Cooperative Extension; Lou Greub is professor andDennis Cosgrove is assistant professor of agronomy, University ofWisconsin-River Falls and University of Wisconsin-Extension, CooperativeExtension; Richard Leep is professor of crop and soil sciences, MichiganState University; Paul Beuselinck is an agronomist with USDA-ARS,Missouri; Dick Smith is an agronomist with USDA-ARS, Wisconsin; StevePeterson and Mark Wipfli are former research assistants in entomology,University of Wisconsin-Madison; and Jim English is assistant professorof plant pathology, University of Missouri-Columbia. Plant bug illustra-tions courtesy Molly Vail. Produced by Cooperative Extension Publications,University of Wisconsin-Extension.

Programs and activities of the Cooperative Extension Service are avail-able to all without regard to race, color, national origin, age, gender, reli-gion, or disability.

In cooperation with the NCR Educational Materials Project.

Issued in furtherance of Cooperative Extension work, Acts of Congress ofMay 8 and June 30, 1914, in cooperation with the U.S. Department ofAgriculture and Cooperative Extension Services of Illinois, Indiana, Iowa,Kansas, Michigan, Minnesota, Missouri, Nebraska, North Dakota, Ohio,South Dakota, and Wisconsin. Cooperative Extension Service, Universityof Wisconsin, Madison, WI 53706.

NCR 474, Birdsfoot trefoil for grazing and harvested forage

November 1993 I-11-93-7M-100-S