NCR547 North Central Regional Extension.Publicationcourses.missouristate.edu/WestonWalker/AGA375_Forages/Forage … · NCR547 North Central Regional Extension.Publication:::e L ~

NCR547 North Central Regional Extension.Publication

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AUTHORS

Dan Undersander

Extension agronomist,forages

University ofWisconsin

Neal Martin


University of Minnesota

Dennis Cosgrave


UniversityofWisconsin

Keith Kelling

Extension soils scientist


Mike Schmitt

Extension soils scientist


John Wedberg

Extension entomologist


Extension agronomist, weed control


Craig Grau

Plant pathologist


Jerry Doll

Extension agronomist, weed control


Marlin E. Rice

Extension entomologist

Iowa State University

ACKNOWLEDGMENTS

T he authors wish to thank reviewers

from industry and various universi-

ties for their suggestions and everyone

who supplied photos, including those

not specifically mentioned:

Steve Bicen, University of Wisconsin

anthracnose; aphanomyces, roots;Fusarinm wilt, roots; Phytophthora, roots;

root assessment; verticillium wilt, root

Jim Ducy title page photo

Del Gates, Kansas State University

alfalfa weeviL,

Craig Grau, University of Wisconsin

aphanomyces, stunting; bacterial wilt,

stuntiug; black stem, lesions; Fusarium wilt,

field; Phytophthora, plant; sclerotinia;verticillium wilt, plants

Eric Holub, University of Wisconsin

aphanomyces, seedling

JeHrey S. Jacobsen, Montana State

University nutrient deficiencies-all except

boron leaf {from Diagnosis of Nutrient

Deficiencies in Alfalfa and Wheat)

Pioneer Hi-Bred International, Inc.

alfalfa closeups; cover photos; cow;

inside cover

lanie Rhodes, Ohio State University

black stem, leaves; common leaf spot;

lepto leaf spot

Marlin E. Rice, Iowa State University

alfalfa weevil, damage; blister beetles; clover

leaf weevils; grasshopper; pea aphids; plant

bug, adults; potato leajhoppel; adult;spittlebug; variegated cutworm

Judy A. Thies, USDA-ARS

root-lesion nematodes

John Wedberg, University of Wisconsin

clover root curculio, damage

This publication is a joint effort of:

University ofWisconsin- Extension,

Cooperative Extension

Minnesota Extension Service,


Iowa State University

Cooperative Extension Service

Produced by:

Cooperative Extension Publications,

University ofWisconsin-Extension.

Editor: Linda Deith

Designer: Susan Anderson

Published by:

American Society of Agronomy, Inc.

Crop Science Society of America, Inc.

Soil Science Society of America, Inc.

(i;;) 1994 by the American Society of Agronomy,

Inc., Crop Science Society of America, Inc.,

and Soil Science Society of America, Inc.

All rights reserved under the US. Copyright

Law of 1978 (RL. 94-553)

Any and all uses beyond the limitations of the

'Jair use" provision of the law require written

permission from the publishers; not applicable to

contributions prepared by officers or employees of

the U S. Government as part of their official

duties.

Library of CongressCataloging-in-Publication DataAlfalfa management guide/ authors,Dan Undersander ...[et al.].

p. cm.

ISBN 0-89118-111-3

1. Alfalfa. I. Undersander, D.J.

SB205.A4A56 1994

633.3'1-dc20 94-27421

CIP

CONT NT

24

24

25

26

2

3

3

3

3

4

5

..27

..28

..29

..30

..31

..32

..32

..33

..34

..34

..35

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.7

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Disease management. .

Anthracnose. Aphanomyces root rot. .

Bacterial wilt. Common leaf spot and

lepto leaf spot. Fusarium wilt. Phytophthora root rot. ..

Root-lesion nematodes. .

Sclerotinia. Spring black stem. Summer black stem. ...

Verticillium wilt. Insect management. ..

Alfalfa weevil. ..

Aphids. Blister beetles. Clover leaf weevil. Clover root curculio ...

Grasshoppers. Plant bugs. Potato leafhoppers. ...

Spittlebugs. Variegated cutworm. ...

When to rotate from

alfalfa.

Establishment. ..

Select a field carefully. Soil type, drainage, and slope. .

Control perennial weeds. ...

Autotoxicity Test soil before planting. ...

Apply lime before seeding. ..

Nutrient needs during

establishment. Select a good variety Yield potential. Persistence. Winterhardiness Disease resistance. Forage quality Intended use. Planting. Time of seeding. Field preparation. Seed inoculation. Seeding depth and rate

Seeding with and without a

compamon crop. Seeding equipment. Reduced tillage and

no-till planting.

13

14

15 40

.16

.17

.17

.19

.19

.19

.20

.20

.20

Harvest .42

Forage quality 43

What quality forage is needed? .43

Plant growth and forage quality .44

Harvest management. 44

Cutting schedule. 45

Fall management. 46

Hay and silagemanagement. 48

Feeding considerations ofhay and haylage 5020

Production. ..

Fertilize annually. Determine needs. Nitrogen. Phosphate and potash. ..

Secondary nutrients. ...

Micronutrients Manure management. .

Weed management. ..

Weed management before

planting. Weed management in the

seeding year. Weed management in

established alfalfa. ...

21

22

Profitable forage production

depends on high yields. Land,

machinery, and most other oper-

ating costs stay the same whether

harvesting 3 tons per acre or 6

tons per acre. Top yields in the

northern United States have

approached 10 tons per acre

while average yields are around

3 tons per acre. This booklet

describes what it takes to move

from a 3-ton yield to 6 or 9 tons

per acre.

A vigorously growing, dense

stand of alfalfa forms the basis

for profitable forage production.

Profitable stands are the result of

carefully selecting fields with

well-drained soil, adding lime

and nutrients if needed, selecting

a good variety, and using appro-

priate planting practices to ensure

germination and establishment.

ESTAB SHM NT3

SELECT A FIELD CAREFULLY

Soil type, drainage,and slopeA lfalfa requires a well-drained soil

for optimum production. Wet soilscreate conditions suitable for diseasesthat may kill seedlings, reduce forageyield, and kill established plants. Youcan reduce some disease problemsassociated with poor drainage by

selecting varieties with high levels ofresistance and by using fungicides for

establishment. Poor soil drainage alsoreduces soil oxygen movement toroots. Poor surface drainage can causesoil crusting and ponding which may

cause poor soil aeration, micronutrienttoxicity, or ice damage over winter.Even sloping fields may have low spotswhere water stands, making it difficultto maintain alfalfa stands.

Soils should be deep enough tohave adequate water-holding capacity.

Alfalfa has a long taproot that pene-trates more deeply into the soil thancrops such as corn or wheat whichhave more fibrous, shallow roots.Under favorable conditions, alfalfaroots may penetrate over 20 feet deep.This great rooting depth gives alfalfa

excellent drought tolerance.Sloping fields where erosion is a

problem may require use of erosioncontrol practices such as planting witha companion crop or using reducedtillage to keep soil and seed in placeuntil seedlings are well rooted.

Control perennial weeds The auto toxic compound,Fields should be free of perennial medicarpin, is water soluble and is

weeds such as quackgrass. If not concentrated mainly in the leaves. A

controlled before seeding, these weeds waiting period after destroying the oldmay re-establish faster than the new stand is necessary to allow this toxic

alfalfa seedlings and reduce stand compound to degrade or move out ofdensity. Weed management is discussed the root zone of the new seedlings.in more detail in the Production Weather conditions influence the

section. speed with which the toxins areFields should be free from herbi- removed. Breakdown is more rapid

cide carryover that may affect growth under warm, moist soil conditions.

of the new alfalfa and/ or companion Ideally, grow a different crop forcrop. This is especially important one season after plowing down or

dl1ring droughts or on fields where chemically killing a 2-year or olderhigh herbicide application rates or stand before seeding alfalfa again inlate-season applications oflong-acting the same field. This is the best andherbicides were used. safest way to manage new seedings of

A t t .. ty alfalfa.U O OXICI

Alfalfa plants produce a toxin thatcan reduce germination and growth ofnew alfalfa seedings. This phenome-non is known as auto toxicity. The

extent of the toxin's influenceincreases with the age and density ofthe previous stand and the amount ofresidue incorporated prior to seeding.

Alfalfa planted, left, in soil from a corn field (no autotoxicity)and, right, in soil from an alfalfa field (autotoxicity).

4 A A A MANAG M NT G u D

TEST SOIL BEFORE PLANTINGp roper fertility management, includ-

ing an adequate liming program, isthe key to optimum economic yields.

Proper fertilization of alfalfa allows forgood stand establishment and promotes

early growth, increases yield andquality, and improves winterhardinessand stand persistence. Adequate fertil-ity also improves alfalfa's ability to

compete with weeds and strengthensdisease and insect resistance.

Fields differ in their fertilizer needs.Soil testing is the most convenient andeconomical method of evaluating the

fertility levels of a soil and accuratelyassessing nutrient requirements.

Most soil testing programs make

recommendations for pH and lime,phosphorus, potassium, and several ofthe secondary nutrients and micronu-

trients. Optimal soil test levels foralfalfa differ among states due to

varying subsoil fertility, nutrient

buffering capacities, soil yield poten-tials, and different management

assumptions. For more detailed infor-mation on soil test recommendations,contact your local Extension office.

SHM NTSE s T A B

Apply before Because lime reacts very slowlyLiming is the single most impor- with soil acids, it should be applied

tant fertility concern for establishing 12 months-preferably longer-before

and maintaining high yielding, high seeding. For typical 4- to 6-year crop

quality alfalfa stands. Benefits of liming rotations, the best time to apply thealfalfa include: recommended amount oflime is when.increased stand establishment and coming out of alfalfa. This allows more

persistence, time for reaction with the soil. The

.more activity of nitrogen-fixing accompanying tillage for rotation cropsRhizobium bacteria may result in two or three remixings

, of the lime with the soil. This should

.added calcium and magnesium, . th H t h d .d 1 1b hraISe e p o t e esIre eve y t e

.improved soil structure and tilth, ti~e alfalfa is replanted.

.increased availability of phosphorusand molybdenum (figure 1), and

.decreased manganese, iron andaluminum toxicity (figure 1) .

For maximum returns, lime fieldsto at least pH 6.7 to 6.9. Field trialsperformed in southwestern Wisconsin Figure 2. first-cutting alfalfa yield relative to soil pH

show that yields drop sharply whensoil pH falls below 6.7 (figure 2). ..,... 5000 -

~uO

~

~"i0>-..Qj....oE

>...

~

4000

3000

2000Figure 1 .Available nutrients in relation to pH

1000

4.5 5.5 6.5 7.5

pH

Source: /MJllenhaupt and Undersandel;

UniversityoJWisconsin, 1991

4

acidic

5 6 7

pH

8 9 10basic

D6 MANAG M NT G u-A A A

Lime effectiveness is determinedby its chemical purity and the finenessto which it is ground. Figure 3 illus-trates the greater effectiveness of morefinely ground lime. To achieve thesame pH change, coarse aglime mustbe applied further in advance and at

higher rates than fine aglime but isusually less expensive per ton. It maynot be necessary to re-lime as oftenwhere some coarse lime is used.

When comparing prices, be sure Liming materials come in several

to evaluate materials on the basis of forms. Calcitic products containamounts oflime needed to achieve calcium-based neutralizers whilesimilar effectiveness. The relative effec- dolomitic sources contain bothtiveness of various liming materials is calcium and magnesium. Both are

given by its lime grade, effective equally effective for changing soil pH.calcium carbonate equivalency (ECCE), Some claims are made that when theeffective neutralizing power (ENP), or calcium to magnesium ratios in the

total neutralizing power (TNP) .soil are low, calcitic limestone shouldAglime should be broadcast on be used. Research evidence does not

the surface of the soil, disked in, and support these claims, as virtually all

then plowed under for maximum midwestern and northeastern soils

distribution and neutralization of acids have ratios within the optimal range.in the entire plow layer. Plowing Dolomitic limestone itself has a

without disking may deposit the lime calcium to magnesium ratio within

in a layer at the plow sole. For high the normal range for plant growth.rates oflime (>6 tons/acre), apply half The addition of calcitic limestone or

before working the field; work the gypsum for the purpose of addingremaining half into the soil after calcium or changing theplowing or other field preparation. calcium/magnesium ratio is neither

recommended nor cost effective.Several by-products, such as

papermilllime sludge and water treat-

ment plant sludge may be used asliming materials. Since the relativeeffectiveness of some of these materialsis highly variable, be sure you know its

Figure 3. Lime availability at different particle sizes. « . ali . ellectlve neutr zmg power.

III...100C

~

M 80

.5.....Qj

~ 60Qj

DlC

] 40

20

c....~QIc

~0

0

>8 8-20 20-60 <60

aglime particle size (mesh)

SHM NT7E s T A B

Nutrient needs duringestablishment

Tillage during establishmentprovides the last opportunity to incor-porate relatively immobile nutrientsduring the life of the stand. Typicalnutrient additions tend to include

phosphorus, potassium, and sulfur.Phosphorus. Adequate soil

phosphorus levels increase seedingsuccess by encouraging root growth.Phosphorus is very immobile in mostsoils. Wisconsin research confirms that

at low to medium soil test levels incor-porated phosphorus is more than twiceas efficient as topdressed phosphorus.

Potassium. Research has shownthat although potassium has relativelylittle influence on improving standestablishment, yield and stand survivalare highly dependent on an adequatepotassium supply. When soil tests are in

the medium range or below, sufficientpotassium should be added to meetthe needs of the seeding-year cropincluding the companion crop.

Sulfur. Elemental sulfur, whereneeded, can be used as the sulfursource and may be applied at seeding.Elemental sulfur must be converted to

sulfate-sulfur before it can be used byplants. This process is relatively slow,especially when sulfur is top dressed.

Therefore, incorporating moderatelyhigh rates (50 lb/acre sulfur) ofelemental sulfur at establishment will

usually satisfy alfalfa sulfur requirementsfor the life of the stand. The cost ofthis treatment should be compared tothe cost of annual top dressed applica-tions of sulfate-sulfur.

Nitrogen. Recent research hasshown that small additions of nitrogen

may enhance establishment and first-year yields. Apply 25 to 30 Ib/acrenitrogen when alfalfa is direct seededon coarse-textured soils with 10""

organic matter contents «2%). Appl)'20 to 35 Ib/acre nitrogen whenseeding alfalfa with a companion cropand apply 40 to 55 Ib/acre nitrogen ifyou will be harvesting the companion

crop as silage.

SELECT A GOOD VARIETYp lant breeders have developed alfalfa

varieties with greater yield poten-rial and disease resistance and

improved forage quality. But with over250 varieties available, how does oneselect an alfalfa variety? The majorfactors leading to profitability are:

.yield potential,

.persistence (percent stand remain-ing or estimated from winterhardi-ness and disease resistance ratings),

.winterhardiness,

.disease resistance, and

.forage quality.

As illustrated in table 1, yield hasthe largest effect on profitability,persistence next, and other factorshave a lesser effect.

Table' .Factors Influencing dollar return per

acre for alfalfa from milk production.

Source: Undersandet; University ofWisconsin, 19911 CP = crude protein; ADF = acid detergent fiber;

NDF = neutral detergent fibel:

"

J

,

.L ,j. Manure may besuccessfully applied prior to alfalfaestablishment if adequate weed controlpractices are followed. RecentMinnesota and Wisconsin research hasshown that preplant manure applica-tion can maintain or even increaseyields the first two years. Whenspreading manure avoid compactingsoil and be sure that the manure is

adequately incorporated so that seed isnot planted directly into high-manureapplication zones.

DN T G uMANAG M-A A A8 -

WinterhardinessWinterhardiness is dependent on

cold tolerance, fall dormancy, andresistance to root and crown diseases.Lack of winterhardiness may result in

winter injury and winterki1l. Winter

injury slows spring growth-meaningfewer shoots for first cutting and a

lower yield. The best indicator of

winterhardiness is stand survivalratings (count oflive plants) the spring

following a severe winter.Generally, varieties with less

winterhardiness have greater yieldpotential because of faster regrowth.Planting several fields of alfalfa, each

with different winterhardiness ratingsensures stand survival of some fields in

severe winters and increases yield

potential in others.

Yield potentialLook for varieties with high yields

in university trials. Compare new vari-

eties to Vernal, a winterhardy checkvariety. Comparing varieties to the

same check, planted within the trial,also allows comparison across several

trials. New varieties should performbetter than Vernal. In Wisconsin andMinnesota variety trials over the last

10 years, the top varieties have yieldedup to 0.89 tons more per acre thanVernal for each year of stand life(figure 4). For short-term stands, select

varieties by yield from 2- to 3-year-old stands. For long-term stands, selectby yield from 4- to 5-year-old stands.

Varieties will perform differentlyin various growing regions. Look fortop yields of a variety grown in a site

with as similar a soil type and climateto your farm as possible. Also, look for

top yield over several sites. This indi-cates stability for high yield and isimportant because soils may vary on

your farm and weather conditions

change from year to year.

range of average 10 minimum temperatures

for each zone

~zone 1- below -50°F

zone 2CJ-50° to -40°F

zone 3G-40° to -30°F

zone 4~-30° to -20°F

zone 50-20° to -]0°F

zone6~-]O°to o°F

CCcM~A

'1,

i.!!:

,~

~

:#m

~

Figure 4. Yield increase over Vernal of top five vari-

eties in Wisconsin and Minnesota from 1980 to 1990.

The two plants on right show severe winter injury. Damagedplants are slow to regrow and produce few stems.

PersistenceCompare stand survival ratings or

yields of 4- to 5-year-old stands todetermine relative persistence of vari-

eties. Persistence in northern locations

is most dependent on winterhardinessbecause of the severity of wintertemperatures (figure 5), while farther

south persistence is more dependenton disease resistance levels. In theabsence of stand survival ratings oryields of 4- to 5-year-old stands, use

winterhardiness and disease resistance

to estimate persistence.

Figure 5. Winterhardiness zones.

Source: USDA

SHM NT9s T A B

Disease resistance

Diseases may cause seedling death,reduce stand density, lower yields, andshorten stand life. The best diseasemanagement strategy is to select vari-eties with high levels of disease resis-tance. Determine potential for diseaseson your farm and select alfalfa vari-eties with resistance to as many ofthem as possible. Knowing whichdiseases have occurred in your fieldswill help you choose varieties with the

appropriate resistance. Look over thedescriptions and pictures in the diseasesection of this booklet, learn to recog-nize them and select resistant varietiesif the disease is occurring in yourfield. To estimate the potential for eachdisease to occur in your area, refer tothe maps in the disease managementsection.

Forage qualityMany new varieties coming on

the market have improved foragequality. Evaluate alfalfa varieties basedon estimated digestibility, intake andrelative feed value compared to Vernal,the standard variety.

Intended useMost alfalfa is planted for harvest

as hay or haylage with plans to keepstands as long as they are productive.Special situations may require differentvariety selection criteria. For example,when a short rotation is desired orwhen nitrogen for other crops is

needed, yield is more important thanpersistence so select varieties withhigh yields in the first two years; whenthe field will be used for grazing,

gelect grazing-tolerant varieties.

PLANTING

Time of seedingS pring seeding is preferred over late-

summer seeding in northern statesdue to a greater chance of successfulstand establishment. Better growingconditions, such as a longer growingseason, adequate soil moisture, andcool temperatures, enhance seedgermination and establishment. Late-summer seeding is preferred in south-

ern states because of the opportunityto establish alfalfa after growinganother crop. Herbicides are notgenerally required for late-summerseeding. Irrigation allows late-summerseedings in all areas.

Spring seeding of alfalfa can beginas soon as the potential for damagefrom spring frosts has passed. At emer-gence, alfalfa is extremely cold toler-ant. At second trifoliate leaf stage

(figure 6) seedlings become moresusceptible to cold injury and may bekilled by four or more hours at 26°For lower temperatures. Alfalfa seededwith a companion crop survives lowertemperatures and longer exposuretimes before showing frost damage.Frost damage is usually not a problemby the time farmers can get fieldstilled in the spring and ready to seed.

Early seedings have less weed compe-tition and less moisture stress during

germination because of cooler

temperatures.The spring seeding dates shown

on the map (figure 7) are averages forthe region. Seeding may be earlier on

light soils, when a companion crop isused, or when forages are established

using reduced-tillage or no-tillmethods. Irrigation may extend theseeding period later into the spring.Successful stand establishment can bemade outside the recommendeddates, but the likelihood of consistentsuccess is low.

10 A l F A l F A MANAG M NT G u D

Figure 7. Spring and late-summer seeding dates.

.spring seeding preferred

D late-summer seeding preferred

spring seeding dates

May 1-30

AprillS-May IS

April 1-30

March I S-April I S

Successfullate-summer seedingdepends on soil moisture during theestablishment period and sufficient

plant growth before a killing frost(figure 7) .Do not seed unless goodsoil moisture is present. A preplant

herbicide is usually not needed for

light infestations because annual weedswill be killed by frost. Postemergence

herbicides are available if severe weedpressure or volunteer grain problemsdevelop. Use of a companion crop isnot recommended, especially wherethe seeding date is August 15 or

earlier, because it competes with alfalfafor moisture. In many regions,Sclerotinia crown rot may be prevalentin late-summer seeding.

Alfalfa needs at least 6 weeksgrowth after germination to survivethe winter. The plant will generallysurvive winter if it develops a crownbefore a killing frost. This allows the

plant to store root reserves for wintersurvival and spring regrowth. Fieldswith less seedling development beforea killing frost may have a greater

problem with winter annual weeds,particularly in southern areas.

late-summer seeding dates

July 20-August 1

August 1-15

August 15-Sept. 1

September 1-15

Figure 8. Effect of weed pressure on late-summer seedings.

100

90

~

"'Cc

HIII

~D

-D

80

70

60

So

spring

seeded

summer seeded

15 T A B 5 H M N T

Minimizing competition fromvolunteer small grains or weeds is crit-ical in northern regions to ensure

adequate development of summer-seeded alfalfa prior to killing frost

(figure 8) .Failure to do so cuts seedlingestablishment and lowers yields.

Field preparallon

Field preparation should begin theyear before seeding. Scout fields forperennial weeds and use appropriatecontrol measures. For example, ifquackgrass is in a field where corn willbe planted, use a pretillage applicationof Roundup or a postemergenceapplication of Accent or Beacon.Cultivate when corn is 14 to 18 inchestall. For control of Canada thistle,dandelion, and other perennial weeds,use an effective management programbefore seeding alfalfa. These weeds can

be particularly competitive both duringthe seeding year and in subsequentyears. Controlling them prior toseeding will help ensure a long-lasting,productive stand.

Soil should be firm enough at planting for a footprint

to sink no deeper than 3jB inch.

Conventional tillage practices varyfrom farm to farm but should consistof a primary tillage (moldboard

plowing or chiseling) followed by

disking. Primary tillage loosens the soiland helps control perennial weedswhile disking provides weed control,helps level the land, and breaks uplarge soil clods. The final tillage shouldbe some type of smoothing operation.On level ground, primary tillage isbest done in the fall as winter freeze-

tbaw cycles help break down clodsand reduces field operations in spring.On erosive soils, fall tillage may not bean option.

The ideal soil condition for

conventional seeding should be asmooth, firm, clod-free soil (seepicture) for optimum seed placementwith drills or cultipacker seeders.

Avoid overworking the soil as rainfallfollowing seeding may crust the

surface, preventing seedling emergence.

Seed inoculation

Rllizobium bacteria nodulatealfalfa roots so the bacteria can fixnitrogen, making it available to theplant. While many soils contain someRhizobium bacteria from previousalfalfa crops, not all fields have

adequate numbers. To ensure the pres-ence of the needed bacteria, purchasepreinoculated seed or treat the seedusing commercial inoculum availablefrom seed dealers. Most varieties are

preinoculated. These inoculant treat-ments often contain Apron fungicideas well, which protects against diseasesthat reduce seedling emergence andkill young seedlings. If treating seedyourself, use a sticker-an adhesivecompound to attach the Rhizobia tothe seed-and thoroughly mix inocu-lum and seed before planting.


Alfalfa is a small-seeded crop andcorrect seeding depth is very impor-tant. Seed should be covered withenough soil to provide moist condi-tions for germination while allowingthe small shoot to reach the surface

(figure 9). Optimum seeding depthsvary depending on soil types. Plantseed Y4- to ~-inch deep on mediumand heavy textured soils and ~- tol-inch deep on sandy soils. Shallower

d:pths may be used when moisture isadequate while the deeper depthsshould be used in drier soils.

Table 2. Effect of seeding rate on

first-year alfalfa dry matter yields.

Source: Buhlet; Proost, and Muellet;

UniversityojWisconsin, 1988

Figure 9. Alfalfa emergence from various seeding depths.

80

70

~ 60GI~ 50GIfI 40GIEGI 30..c

..2 200.

10

02.0

Seeding rates should be between12 and 15 lb/acre with good soil

conditions and seeding equipment

(table 2). Higher seeding rates do not

produce higher yields except underpoor seeding conditions. Lower ratesare normally used in arid regions.While these rates may be higher thanneeded for good stands under ideal

conditions, the wide range of field andenvironmental conditions experiencedat seeding make this necessary to

obtain consistently good stands.Extended periods of cool, wet weathercan cause high seedling mortality (thiscan be reduced by planting Apron-treated seed) .Hot dry weather at

seeding time likewise may reducegermination and seedling establish-ment. Under normal conditions, onlyabout 60% of the seeds germinate and

nearly 60 to 80% of the seedlings diethe first year (figure 10).

An important and often over-

looked aspect of planting alfalfa isseeder calibration. Seed size can varybetween varieties and between seedlots of the same variety. Calibrate

seeding implements each time you usea new variety or a new seed lot, or ifyou use lime- or clay-coated seed.

Regular calibration can help to avoidover- or underseeding.

1.0 1.5

seeding depth (inches)

Source: Sund et al., University of Wisconsin, 1966

Figure' 0. Stand density during first 12 months

(seeded at 12 Ib/acre).

60

~

0-III

total

seeds

germinated ~Iants afterseeds first winter

50

40

30

20

10

0

s T A B L S H M N T 13

Seeding with and without Companion crops, such as oats,a crop spring barley and spring triticale, help

Direct seeding alfalfa (plant- control erosion, reduce seedlinging without a companion crop) allows damage from blowing sands, and mini-growers to harvest up to two extra mize weed competition during estab-cuttings of alfalfa and produce higher lishment. Companion crops also

quality forage in the seeding year as provide additional forage whencompared to seeding with a compan- harvested as oatlage or additionalion crop. However, total forage tonnage income if harvested as dry grain. Straw

may be reduced relative to compan- produced by the companion crop is

ion-crop seedings. Some important also valued as livestock bedding. Whenmanagement considerations are: companion crop growth is dense and.Select level fields with low erosion allowed to grow to grain, alfalfa

potential for direct seedings and uQderneath is often damaged either byuse companion seedings where the competition or by lodging of the small

erosion potential is greater. Erosive grain which smothers the alfalfasoils can be direct seeded using seedlings. Winter wheat, spring wheat,reduced or no-till methods that and rye usually compete too stronglyleave adequate residue on the with alfalfa seedlings and are less desir-surface. able as companion crops.

.Effective weed management iscritical in direct seeding (as no

companion crop is present). Seethe section on weed management

for details.

.Harvest the first cutting after60 days of growth, regardless of Figure 11. First-season yield of alfalfa using different establishment methods.

maturity stage. This eliminatesmany annual weeds and allows the 4. 0

second cutting to reach theYto bloom stage by September 1 in 3.5areas with short growing seasons.

(RFV=102)

(RFV= 137)

3.0

2.5

2.0

1.5

"'Qi'..uc

IIICO

.=..

"0"i">...GI=CE)....

"0 1.0.alfalfa

.grass weeds

.broadleafweeds

.oats

0.5

0

alfalfa/Bala"

alfalfa/ alfalfa/oatsoatlage with Poast Plus

G u DMANAG M NT14 A L F A A

Band seeders place the seed in

rows, usually with 7- to 9-inch spac-ings, and can place fertilizer below theseed where it's most effective. To

improve establishment, use presswheels mounted on the seeder orsome other packing device, such as a

cultipacker, pulled behind the seeder

or used in a separate pass (figure 12).The most common band seeders are

grain drills that can seed a companioncrop simultaneously with the alfalfa.

However, grain drills have poor depthcontrol of seed placement. Bandseeders adapted for forages have depth

bands to overcome this problem.Alfalfa and companion crop seed must

be put in separate seed boxes.Companion crops should be seeded1 to 2 inches deeper than alfalfa. This

can be done in a single pass by placingthe drop tubes for the companioncrop between coulters and for alfalfa

behind coulters (see picture).

Figure' 2. Comparison of seeders for stand establishment.

125

100

IIIIIIG>CG>>

'.;UG>

~G>

G>>

'.;C

f

75

So band seeder

band seeder withpress wheels

band seederwith cultipacker

cultipacker

25

0

spring seeding summer seeding

Source: Tesal; Michigan State University, 1984

For good alfalfa stands withcompanion seedings, manage the field

to the advantage of the alfalfa ratherthan for the companion crop. Some

important management considerations

are:.Select companion crop varieties

that are short, stiff strawed, and

early maturing to avoid lodgingand smothering the alfalfa.

.Seed the companion crop at 1 tolY2 bushels/acre on heavy soils and1 bushel/acre on sandy soils to

reduce competition for light and

moisture with the alfalfa seedlings.

.Limit nitrogen applications to no

more than 30 lb/acre to avoid

excessive competition and lodging

of the companion crop.

.Harvest the companion crop at theboot stage rather than leaving it for

grain. Harvesting at the boot stagereduces competition with alfalfaand minimizes the chance forlodging and smothering the alfalfa

crop. This harvest stage provides

.If you do harvest the companioncrop for grain, cut it as early as

possible to minimize lodgingdamage. Remove straw as quicklyas possible to avoid smothering the

alfalfa stand. Harvesting compan-ion crops for grain is not recom-mended for good alfalfa stand

establishment.

Seeding equipmentMany different types of drills and

seeders are used to seed alfalfa. All willproduce good stands when planting to

an accurate seeding depth in a firm,

moist soil.Cultipacker seeders, such as the

Brillion seeder, broadcast the seed onthe soil surface and then press it into

the soil with rollers. These seedershave been a mainstay of alfalfa estab-lishment because they give consis-tently even seed depth placement andgood seed-soil contact for most soils.

s T A B L S H M N T 15

no-lilllDue to the high potential for

erosion on slopes using conventionaltillage, a great deal of interest has beengenerated in reduced tillage alfalfa

establishment. These practices includethe use of a chisel plow rather than a

moldboard plow, a single pass with a

secondary tillage tool, or no tillage atall. Reduced tillage practices are

generally successful when careful,timely management is used.

Crop residue management is animportant factor in reduced-tillageseeding. Chisel plowing or diskingtypically chops the residue finelyenough for conventional seedingimplements to be used. In corn

residue, single disking may give thesame result. Cultipacker seeders willnot perform well with residue levelsabove 35% so a no-till seeder is

recommended. Chopping stalks helpseven the residue in the field and can

reduce the amount of residue in thefirst alfalfa harvest.

Special attention must be given toweed management in reduced tillage

systems. Oats can still be used as acompanion crop. When direct seeding,weed control is more difficult as thereis less tillage to decrease weed popula-tions. Perennial weeds are the most

difficult to control. Lack of deep

tillage may give some perennial weedsa head start on the alfalfa. The use of a

nonselective herbicide such asglyphosate to control perennial weeds(preferably in the previous fall) is criti-cal.prior to reduced or no-till seeding.Other weed control options are similarto conventional direct seeding and arediscussed later in this publication.

An additional consideration in no-till alfalfa establishment is soil fertilityand pH.As no tillage is done in the

seeding year, materials that work bestwhen incorporated, such as phosphorus

fertilizers and lime, should be appliedand worked into the soil prior to enter-

ing into no-till systems. If incorpora-tion is not feasible, apply the finest gradeoflime obtainable 1 to 2 years ahead of

seeding to raise soil pH in the top inchof soil. (Lime moves downward at about

To plant companion crops 1 to 2 inches deeper than alfalfa in a singlepass, place the drop tube for alfalfa behind coulters but before the packerwheel and place the drop tube for the cover crop between coulters.

~ inch per year on silt loam soils and

somewhat faster on coarser soils.) Fine-

grade alternative liming materials suchas papermilllime sludge or cement

plant kiln dust can also be used.

Many implement companiesproduce specialized no-till seeders foralfalfa and other crops. The design ofthese seeders differs among companiesbut should have the following featuresto ensure success:

.heavy down pressure,

.coulter ahead of disk openers tocut trash,

.double disc openers or an angledsingle disc opener,

.press wheels,

.small-seed box, and

.depth control mechanism.

Set seeding depths carefully asthese implements are very heavy and

may easily place seed deeper than

optimum.No-till seeders are often available

for rent through Land Conservation

offices, the Soil Conservation Serviceor local fertilizer dealers and elevators.

Once a good stand has been

established, continued production

and stand life depends on good

management practices. Good

management includes maintain-

ing soil nutrients, applying

manure judiciously, and control-

ling weeds and insects. Monitor

diseases to estimate stand life

and to determine resistance

needed in future plantings.

Finally, optimum production

involves deciding when to rotate

from stands that are no longer

profitable.

p R O D U C T ION 17

Soil tests are the most reliablemethod for preventing nutrient defi-ciencies. Visual symptoms (table 5 and

pictures) can be used to help assessnutrient needs for future yield.

However, by the time visual symptomsappear on a crop, nutrient deficiencymay be so severe that significant yieldlosses have already occurred. Visualsymptoms can also reflect environ-mental conditions, restricted root

growth, diseases or other problems notrelated to a soil nutrient shortage.

..Plant tissue analysis can determinethe nutritional status of your cropbefore any visual symptoms appear.While this method does not measurenutrient amounts for making a fertil-izer recommendation, combining thiswith a soil test makes for a compre-hensive nutrient management system.

FERTILIZE ANNUALLY

Determine needsA lfalfa has a relatively high demand

for some nutrients compared toother commonly grown crops. Eachton of alfalfa dry matter harvestedremoves about 14 pounds of phos-

phate {P 205) and 58 pounds of potash{KzO). This is the nutrient equivalentof 150 pounds of a 0-10-40 fertilizer.Each ton of alfalfa also removes thecalcium and magnesium found inabout 100 pounds of aglime. Seetable 3 for a complete list of nutrients

removed. Since many of these nutri-ents are supplied from the native soil

reserves, basing a fertility program onremovals is not recommended.

Table 3. Pounds of nutrient removed per

ton of alfalfa produced, dry matter basis.

Table 4. Sufficiency levels of nutrients, top 6 inches of alfalfa at

first flower.

18 - A A A MANAG M N T G u D

Phosphorus deficiency

Table 5. Nutrient deficiency symptoms

for alfalfa.

Deficient plants have blue-green leavesand stunted growth.

Leaflets often fold together, and theundersides may be red or purplish (left).

potassium deficiency

Leaves of severely deficient plants turn

completely yellow.

Lower leaves of deficient plants areedged with white spots (left).

Sulfur deficiency

Stems are spindly with weak growth. Leaves turn light green (left). Symptomsare similar to nitrogen deficiency.

Boron deficiency

Deficient plants have yellowed leaves on

shortened stems.

Yellow coloring turns reddish to purplishbetween veins.

nutrient deficiency symptoms

nitrogen Light green to yellow color,

spindly growth.

phosphorus Blue-green color, stiff, stunted

and erect growth. Leaflets

often fold together, and the

undersides and stems may be

red or purplish.

potassium White spots around edge of

leaf starting with lower

leaves. In advanced cases

leaves turn completely yellow

and die.

calcium Impaired root growth or

rotting. Petioles collapse on

youngest mature leaves.

magnesium Interveinal chlorosis of lower

leaves, margins initiallyremain green.

sulfur Light green, similar to nitro-

gen deficiency, spindly stems

and weak growth.

boron Yellowing of leaves, short-

ened main stem growth

between upper portion of

shoots, dense top. Often

confused with leafhopper

damage.

manganese Interveinal chlorosis of

younger leaves.

iron Interveinal chlorosis of

youngest leaves, bleached

appearance.

zinc Reduced leaf size and

upward curling of youngest

leaves.

copper Severe curvature of petioles,

grayish spots in midleaf.

molybdenum Pale green and stunted as

with nitrogen deficiency.

p R O D U C T 0 N 19

Nitrogen because phosphorus is immobile, 6. Foliar application should not beAlfalfa typically gets enough nitro- alfalfa responds better to incorporated used for applying moderate to

gen from its symbiotic relationship applications than to topdressed appli- high rates of macronutrients,with nitrogen-fixing Rhizobium bacteria cations. Guidelines for annual phos- although it is an excellent methodand from soil organic matter, which phate and potash application include for applying micronutrients.releases nitrogen as it decomposes. On the following: S II t . t. 1 d .. di econ ary nu rlen sestablished stands, topdressed rutrogen 1. App y top ress nutrIents Imme ..

1 ti h b 1: h CalcIUm and magnesIUm deficlen-does not improve YIelds, quality or ate y a ter arvest elore regrowt ...

A .d . h cles are very rare, especIally where soil

stand vIgor. Adding rutrogen may In resumes. VOI contact wIt wet. ...

1: 1 . Id dl ali b .1: li pH has been maIntaIned In the desIredlact ower YIe an or qu ty y stlm- 10 age.

range for alfalfa. Symptoms of magne-ulating growth of grasses and weeds. 2. Topdress following first cutting to . d fi .

h h ilsIUm e clency appear wen t e soPhosphate and potash stimulate second and third cutting test drops below 50 to lOO ppm

d 1 . 1 1 regrowth or in early September to. .dAlfalfa nee s re atlve y arge ...magnesIUm. MagnesIUm can rop

f h h d h Increase wInter hardIness. 1 .di d ilamounts 0 p osp ate an potas .below that leve on acI c, san y so sAdequate phosphorus is important for 3. Avoid application when soils are where repeated high amounts ofsuccessful establishment and good root soft (such as early spring) when potassium have been applied; on soils

development. Potash is essential for physical damage to the alfalfa where only calcitic liming materialsmaintaining yields, reducing suscepti- crown is likely. have been used; and on calcareousbility to certain diseases, and increasing 4. Split the application to avoid salt organic soils. The most economicalwinterhardiness and stand survival. In damage if more than 500 lbl acre way to avoid calcium or magnesiumthe eastern portion of the Midwest, of material (irrespective of grade) problems is to follow a good limingpotassium is likely the most limiting is to be used in any year. program with dolomitic limestone.nutrient to alfalfa production. 5 B 1: .li h Where soil pH is adequate and extra

.ase lertI zer purc ases on costPhosphate and potash are rela- . f 1 1: d . d d magnesium is needed, apply magnesium

per urut a p ant 100 provI etively immobile when added to the d d 1: all .sulfate (epsom salts) or potassium-

.an nee lor nutrIentssoil. Phosphate bonds tightly on acidic . d .1: till . F magnesium sulfate (Sul-Po-Mag or

contaIne In ler zer. orclayey soils (PH < 5.5) or on very 1 . h . d .J:r K-Mag) at 20 to 50 lblacre magne-...examp e, sInce t ere IS no Iller-high pH soils (PH > 7.5) making It. .. 1 b .l .. h sium per year.

ence In nutrIent avaI a Ilty wItunavailable to plants. Potash can leach d h . h . h Sulfur deficiencies are likely when

.re versus w Ite potas or wIt .on some extremely sandy sOIls and on

h 1 h h high sulfur-demanding crops such asort 0- versus po yp osp ate on

organic soils (peat or muck). Applica- il h b h .. h alfalfa are grown on sandy soils or on

most so s, t e est c OIce IS t e

tions of phosphate and potash should 1 . d P .other soils low in organic matter fareast expensIve pro uct. otassIUm-

be based on recommendations from a . 11: b from urbanized areas and which havemagnesIUm su late may e a supe-

recent, well-calibrated soil test. .. h lfi not received manure within the lastrlor potassIUm source were su ur

Alfalfa absorbs most nutrients, . d d d 1. d fr 2 years. Use of coal, fuel oil, and otherIS nee e an not supp le om

including phosphate and potash, from h 1: -1 .. 1 fossil fuels in industrial areas releases

anot er lertllzer materIa .

the top 6 to 8 inches of soil. However, sulfur into the atmosphere that is

deposited on the land in precipitation.Table 6. Estimate of available sulfur from manure as affected by animal and In general, precipitation containsmanure type. enough sulfur to take care of crop

needs in most regions (10 to 25 lblacre

each year) .The amount of sulfur inmanure depends on the kind of animalmanure (table 6). Some subsoils, espe-cially those that are acidic and clayey,may contain enough sulfur for high-yielding crops even though the plowlaver mav test low.

20 MANAG M NT G uA AA

Where the sulfur need has beenestablished, either elemental sulfur or

sulfate forms can be used on alfalfa.Sulfate-sulfur is immediately availableto the crop, whereas elemental sulfurmust be biochemically converted to

sulfate before it can be used. Whenapplied at 25 to 50 lb/acre, sulfate-sulfur will generally be adequate for

one or two years of alfalfa production.In contrast, elemental sulfur applied atthat rate should last for the term of thestand. Elemental sulfur converts to

sulfate more rapidly when incorporated.

Alfalfa has a relatively highrequirement for molybdenum.However, since molybdenum availabil-ity increases as pH increases, liming to

optimal pH levels usually eliminates

molybdenum problems. Manganese,zinc, iron, and copper are rarely defi-cient in alfalfa. In special situations

where deficiencies are suspected,contact your county Extension office

or consultant before treating.

MANURE MANAGEMENTM anure is a complete nutrient

source, containing all of the majornutrients, secondary nutrients, and

micronutrients. In addition, manurepromotes biological activity and

enhances the soil physical properties.While manure may be beneficial tosoil, applying manure on alfalfa fieldscan create problems. Manure can burnleaves, reducing yield and quality. The

mechanics of applying manure cancompact soil and damage crownswhich in turn lowers yields and short-ens stand life. Also, nitrogen in manure

can stimulate weed and grass growth.If possible, spread manure on

other crops that can benefit from thenitrogen. Alfalfa will use applied nitro-gen but does not need it due to itsability to fix nitrogen. When too much

manure and/ or too litcle croplandforce application of manure to alfalfa,

top management is required.When alfalfa fields are the only

land available for spreading manure,use the following guidelines to reduce

damage to the alfalfa stand:1. Choose fields that have the most

grass, usually the oldest stands,since these will benefit most from

nitrogen in manure.

Plants need only very smallamounts of micronutrients formaximum growth. While a deficiencyof any essential element will reduceplant growth, overapplication ofmicronutrients can produce a harmfullevel of these nutrients in the soil that

is difficult to correct, especially oncoarse-textured soils. Soil tests areavailable for some micronutrients, butplant analysis is generally more reliable

for identifying micronutrient problems.Boron is usually the only

micronutrient that is needed in afertilizer program for alfalfa. Boronmanagement depends on the textureof the soil. Sandy soils do not holdboron as tightly as clayey soils. A high

test in a sandy soil may be onlymedium in a silt loam. For alfalfawhere the soil test is very low or lowon medium-textured soils, apply 2 to

3 lb/acre boron once in the rotation.On sandy soils apply 0.5 to llb/acreboron each year. Due to the low rate

of material needed, boron is oftenmixed with other fertilizers such as

potash. Do not apply boron near

germinating seeds.

Most alfalfa stands are left in

production for several years. Theabsence of tillage during the life of the

stand naturally favors invasion byperennial weeds. It is very importantto eliminate weeds before establishing

2. Apply no more than 3,000 gallonsof liquid manure or 10 tons of

solid manure per acre. Applyingmore may cause salt burn, and

damage or suffocate plants. Usesupplemental fertilizer if additional

nutrients are required.

3. Spread manure immediately after

removing a cutting so manurecontacts the soil instead of thefoliage. This reduces the risk of salt

burn and minimizes palatability

problems.

4. Adjust the spreader to break uplarge chunks of manure that can

smother regrowth.

5. Spread manure only when soils are

firm to limit soil compaction andto avoid damaging crowns.

WEED MANAGEMENTW eeds reduce alfalfa production

during establishment by compet-ing with and choking out youngalfalfa seedlings. Weeds also invadeestablished alfalfa fields and reduceforage quality and yield. Effective

weed control begins before seedingand continues throughout the life ofthe stand. The most important factor

in weed control is to establish and

maintain a vigorous alfalfa crop.Proper soil fertility and pH, varietal

selection, and seedbed preparationcannot be over-emphasized to preventweed encroachment. If using a herbi-

cide, remember that application timingand rates vary-always read the productlabel for application instructions.

Weed managementbefore

p R O D U C T ION 21

Weed management in Direct-seeded plantings-the seeding year preplant-incorporated treatments

Tillage is an important part of a Balan (benefin) is a preplant-

weed management program when incorporated herbicide that controlsestablishing alfalfa. Thorough tillage annual grasses and some annual

helps uproot existing annual weeds broadleaf weeds. Balan must be incor-and sets back established perennial porated to a depth of2 to 3 inches.

weeds. Final tillage should be done as Incorporation may be delayed for upnear planting as possible to allow to 8 hours, but prompt incorporationalfalfa a head start on weed growth. is best. Incorporate with a disk or

Most alfalfa in the Midwest is other suitable implement and work inplanted with a companion crop to two different directions. Do not usecontrol weeds and soil erosion. Balan if planting a forage grass crop asHerbicides are seldom needed in these it will be killed by Balan. Injury fromsystems, especially if the small grain is Balan at recommended rates is gener-harvested as silage. For direct-seeded ally not a problem.

alfalfa planted in the spring, herbicides Eplam (EPIC) is a preplant-for weed control are usually necessary. incorporated herbicide that controlsSeveral herbicides are currently labeled annual grasses and several broadleaffor use in new alfalfa seedings. This weeds. Eptam must be thorougWysection describes the most commonly incorporated to a depth of 2 toused options. Performance ratings for 3 inches. Incomplete incorporation

each herbicide are listed in table 7. may cause streaking and alfalfa injuryor loss of herbicide. Incorporate with a

alfalfa. Herbicides for perennial weedcontrol may be applied in spring or

fall. Fall application is recommendedin most cases for more consistent

control. Applying nonselective herbi-cides to perennial weeds at the propergrowth stage in spring may delay

alfalfa planting past the optimum time.Herbicides for perennial weed

control the year before seeding alfalfainclude Banvel, Roundup, 2,4-D, andtank mixes of these herbicides. Banvelcarryover will damage alfalfa seedlingsunless used far enough in advance ofalfalfa planting. Consult labels for

specific recommendations.One of the most serious perennial

weed problems in alfalfa stands in

northern states is quackgrass. Fallapplication of Roundup is more effec-tive than spring application. Quack-grass should be actively growing whenRoundup is applied.

Table 7. Alfalfa tolerance and herbicide effectiveness on common weeds in direct seedings.

{Buctril is the only herbicide registered for use on alfalfa seeded with companion crops.)

Source: Adapted from Becket; University of Minnesota, 19941 G = good; F = fair; p = poor; N = no control.

2Control ratings for annual seedlings only.

MANAG M NT G u D22 A A A

Table 8. Impact of common weeds on forage quality.disk or other suitable implementworking the field in two different

directions. Eptam can temporarilystunt alfalfa and the first leaves maynot unfold properly. Injury may bemore pronounced when applied under

cool, wet weather, when high rates

have been applied, or when poorlyincorporated. Do not use Eptam if any

atrazine was used in the previous12 months as severe injury may result.Do not use Eptam if planting a forage

grass crop as it will be killed by

Eptam.

Direct-seeded plantings-postemergence treatments

Buctril (bromoxynil) is a post-emergence contact herbicide that

controls many common broadleafweeds. For best results, treat whenalfalfa has at least four trifoliate leavesand when weeds are 2 inches or less in

height and have no more than four

leaves. Buctril gives fair to goodpigweed control if plants are small and

actively growing when applied. Alfalfa

injury may occur if the temperatureexceeds 70°F within 3 days after appli-cation. Do not treat alfalfa stressed bymoisture shortage or excess, insectinjury, or other causes. Treated fieldscannot be harvested or fed for 30 days

after spring application.Butyrac (2,4-DB) is a post-

emergence systemic herbicide thatcontrols many annual broadleaf weeds

but is weak on larger mustards and

smartweed and will not controlgrasses. It suppresses some perennialbroadleaf weeds. Apply when seedling

weeds are small and actively growing.Correct timing is critical as control is

less effective on larger weeds. Checkthe label for specific rates according to

weed species and size. Treated foragecannot be harvested or grazed for

60 days after application.

Source: Doll, University ofWisconsin, 1993

Buctril can be tank mixed with

Butyrac to improve control whenweeds in the mustard or smartweedfamily (which are sensitive to Buctril),and pigweed (which is more sensitiveto Butyrac) are present. Forage treatedwith this combination cannot beharvested or fed for 60 days after

application.Poast Plus (sethox:ydim) is a

selective postemergence systemicherbicide that controls most annualgrasses present in alfalfa. Apply to

annual grasses according to labelinstructions. Grasses must be activelygrowing for best results. Poast Plus

gives some suppression of quackgrass.Alfalfa can be harvested 7 days

after Poast Plus treatment if the forageis green chopped or ensiled, and 14 days

after treatment if harvested as dry hay.Use Poast Plus to control volunteergrains that emerge following wheat oroat harvest. Treat when cereals are 2 to

4 inches tall and before tillering has

started.Poast Plus and Butyrac can be

tank mixed and applied to newlyseeded alfalfa to control a mixture ofgrass and broadleaf weeds. With a tank

mix, the possibility of crop injury

increases because the oil concentrateincreases Butyrac uptake. Use the rateof product as indicated for the weed

species present. Do not tank mixUAN or ammonia sulfate withButyrac. Treated forage cannot be

harvested or grazed for 60 daysfollowing application. It may be diffi-cult to apply this tank mix at the

proper time to adequately controlboth grasses and broadleaf weedsbecause each may not be at the beststage for control at the same time.

Companion-crop seeded plantingsBuctril (bromo:xynil) can be

used in companion seedings to control

several broadleaf weeds. It is veryeffective on wild mustard andcommon lambsquarters. Buctril maycause serious alfalfa injury if tempera-tures exceed 70°F within 3 days afterapplication and if the alfalfa has fewer

than four trifoliate leaves.

Weed management inestablished alfalfa

Weeds encroach on alfalfa as stand

growth slows due to poor fertility,disease and insect problems, andwinter injury. Removing weeds fromalfalfa seldom increases the tonnage of

harvested forage. Rather, the propor-

p R O D u c T ION 23

small and actively growing. Correcttiming is critical as control is lesseffective on larger weeds. Check thelabel for specific rates according toweed species and size. Treated foragecannot be harvested or grazed for

30 days after application.Lexone or Sencor (metribuzin)

control a broad range of annual and

perennial weeds, including fair togood control of dandelion and quack-grass. Alfalfa must be established for atleast 1 year before using these prod-ucts. Apply in spring while alfalfa isdormant to avoid injury or impregnatethe herbicide onto dry fertilizer and

apply when alfalfa is less than 3 inchestall and the foliage is dry. Rates varywith soil type and weed infestation.Consult label for appropriate rates aswell as for rotational restrictions.Treated alfalfa may be harvested

28 days after application.

tion of alfalfa in the harvested forageincreases. Whether this affects forage

quality depends upon the weed speciesand their stage of growth. Dandelions

and white cockle, for instance, havevery little effect on forage quality andanimal intake while other weeds suchas yellow rocket and hoary alyssumdecrease animal intake due to their

unpalatability. The higher fiber contentof grassy weeds also decreases intake.

Refer to table 8 for a comparison ofthe relative impact of weeds on forage

quality.The decision to use herbicides for

weed control in established alfalfastands should be based on the degreeof the weed infestation, the type ofweeds present and most importantlythe density of the existing alfalfa stand.

For treatment to be economical, weedinfestations must be severe enough andof species that reduce forage quality,and alfalfa stand density must be high

Table 9. Alfalfa tolerance and herbicide effectiveness on common weeds in established stands

Source:Adaptedjrom Becket; University of Minnesota, 19941 G = good; F = fair; p = poor; N = no control.

enough to respond to the decreased

competition upon weed removal.Herbicide application to thin alfalfastands severely infested with weedswill increase forage quality but candecrease forage yield. A1falfa does not

spread into open areas, so removingweeds in thin stands often means rein-festation. The cost of herbicide treat-ments such as Velpar, Sencor, andLexone can generally be spread over2 years because weeds will besuppressed for that length of time-

Table 9 compares the herbicidesa~ailable for established stands. The

paragraphs below describe the herbi-cides and when to apply them.

Bulyrac (2,4-DB) may beapplied to established stands to controlseveral broadleaf weeds but is weak onlarger mustards and smartweed andwill not control grasses. It gives somesuppression of perennial broadleafweeds. Apply when seedling weeds are

24 A L F A L F A MANAG M NT G u D

AnthracnoseAnthracnose occurs most often

under warm, moist conditions andcauses yield losses of up to 25%. Onsusceptible plants, stems have large,

sunken, oval- to diamond-shapedlesions. Large lesions are straw coloredwith brown borders. Lesions canenlarge andjoin together to girdle and

kill one to several stems on a plant.Girdled stems may wilt suddenly and

exhibit a "shepherd's hook."Thisshould not be confused with frostdamage. Dead stems are often scattered

in the field with straw-colored topearly white dead shoots. Anthracnoseis most important as a pathogen ofcrown tissue, turning it blue-black,resulting in fewer stems per plant andeventual plant death. Moderate orhigher resistance is available in many

varieties.

mild.severe II moderate

Poast Plus (sethox:ydim) may DISEASE MANAGEMENT

be applied to established stands toS everal diseases oc~ur in.al~alf~ stands

suppress quackgrass or control annual that can kill seedlings, lillllt yields,

grasses. Treat when quackgrass is 6 to and shorten stand life. The occurrence

8 inches tall and when annual grasses and severity of diseases depends onare small and actively growing. Do not environmental conditions, soil type,

apply to grass-legume mixtures as and crop management. Few economi-forage grasses will be stunted or killed. cal control options are available forAlfalfa may be harvested after 7 days as diseases once they're present in a field,green chop or haylage and after 14 days but knowing diseases are present can

for dry hay. help you select resistant varieties forYelpar (hexazinone) controls a future plantings.

broad spectrum of annual and peren-nial weeds, including fair to good Distribution ond severity

control of dandelion and quackgrass. AnthracnoseAlfalfa should be established for 1 year

or more prior to treatment. ApplyVelpar in spring to dormant alfalfa orbefore new growth exceeds 1 to2 inches. Treating taller alfalfa willseverely injure plants. Rates varyaccording to weed types present andsoil type. Consult the label for specific

recommendations and rotationalrestrictions. Do not graze or feed

treated hay for 30 days.Fall-applied Velpar controls certain

species (especially winter annuals) butis less effective on dandelion thanspring applications. The uncertainty ofwinter survival of alfalfa also makes falltreatment a risky venture in most areas.

The diseased crown (right) shows blue-black coloring ofanthracnose.

Straw-colored lesions on stems are indicative of anthracnose


Distribution and severity

Aphanomyces

4

.severe II moderate D mIld

Aphanomyces root rotAphanomyces root rot is an

important disease of wet soils. It stuntsand kills seedlings and causes a chronic

root disease in established plants.Infected seedlings develop yellow

cotyledons followed by cWorosis ofother leaflets. Roots and sterns initially

appear gray and water-soaked, thenturn light to dark brown. Seedlingsbecome stunted but remain upright.

Aphanomyces reduces root mass onestablished plants. Nodules are

frequently absent or in some stage ofdecay. Infected plants exhibit symptomssimilar to nitrogen deficiency and areslow to regrow following winter dor-

mancy or harvest. For best results,select varieties with high levels of

resistance to both aphanomyces and

Phytophthora root rot.

Infected seedlings develop yellow cotyledons

Infected plants lack lateral roots (from left, second and fourth pairs).

Comparison of susceptible (left) and resistant (right) varieties showsstunting and slight yellowing caused byaphanomyces.

26 A L F A A MANAG M NT G u D


Bacterial wilt

Bacterial wiltBacterial wilt symptoms begin to

appear in the second and third yearand may cause serious stand losses in

3- to 5-year-old stands. Affected plantsturn yellow-green, are stunted and, in

early stages, are scattered throughoutthe stand. Severely infected plants arestunted with many spindly stems andsmall, distorted leaves. Diseased plantsare most evident in regrowth afterclipping. Cross sections of the taprootshow a ring of yellowish browndiscoloration near the outer edge.Most varieties are now resistant to this

disease.

\~j'..;- ~

.moderate [J mIld

~

The entire plant is stunted and yellowed by bacterial wilt.

Varying degrees of infection shown by

yellowish-brown ring.

p R O D u c T 0 N 27


Common leaf spot

Distribution ond severity

Common lepto leaf spot

Lepto leaf spot attacks youngregrowth of alfalfa during spring andfall or midwinter in southern areas.Disease growth is particularly notice-able following cool, rainy periods. Thelesions start as small, black spots and

enlarge to 0.1 inch diameter with lightbrown or tan centers. The lesions are

usually surrounded by a yellow,chlorotic area. Lesions often enlargeand grow together. Yield and quality islost through loss of dead leaves bywind or during harvesting. Resistantcultivars are not available.

'1

mild mild.severe ij mode rote .severe !II moderate

Common leaf spotand lepto leaf spot

Common leaf spot occurs primar-ily in first and second cuttings and infall regrowth of most alfalfa stands.

Disease severity depends on alfalfaconditions and varietal resistance.Symptoms appear as small, brown toblack lesions-each less than 0.1 inchdiameter-that rarely grow together.The lesions may have a small raiseddisc in the center of the lesion on

upper leaf surface. Leaves turn yellowand fall off plant. The disease causesyield reductions and lowered forage

quality through leaf loss. Severelyinfected fields should be harvested

early. Some varieties are moderatelyresistant.

Lepto leaf spot lesions have tan centers and are surrounded by ayellow halo. Lesions often enlarge and grow together.

Common leaf spot lesions are small brown to black areas that

rarely grow together.

28A L F A L F A MANAG M N T G u D


Fusarium wilt

Fusarium causes a characteristic reddish-brown discoloration thatbecomes more evident as the disease progresses (left to right).

Fusarium wiltFusarium wilt is a vascular disease

that causes gradual stand thinning.Initially, plants wilt and appear torecover overnight. As the diseaseprogresses, leaves turn yellow thenbecome bleached, often with a reddishtint only on one side of a plant. Afterseveral months the entire plant dies.Symptoms are similar to bacterial wiltbut plants are not stunted. To diagnoseFusarium, cut a cross section of theroot. The outer ring (stele) of the root

is initially streaked a characteristicreddish brown or brick red color. As

the disease progresses the discolorationencircles the root and the plant dies.

Practice good fertility and control peaaphids and potato leafhoppers to

reduce the effects of this disease. Manyvarieties are resistant to Fusarium wilt.

Disease bleaches the leaves and stems on plants scattered throughoutthe field. Symptoms are similar to bacterial wilt but affected plants

are not stunted.

29-PRODUCT O N


Phytophthora root rot

.severe II moderate mild

Crop rotation is oflitde value forPhytophthora root rot control becausethe fungus can survive indefinitely inthe soil. However, good management

practices can prolong the productivityand life of infected plants that survivethe initial infection.

1. Maintain high soil fertility to

promote extensive lateral rootdevelopment above the diseasedregion of the root and to extendthe life of the plant.

2. Avoid untimely cuttings that

.might stress the plants. Heavy rainsimmediately after cutting oftenresult in severe infections. Do not

cut, for example, betweenSeptember 1 and October 15.

3. Controlleaf-feeding insects, whichcan stress plants and make themmore susceptible to Phytophthora.

4. Tilling and land-leveling, if practi-cal, can reduce Phytophthora rootrot by improving surface and

subsurface drainage. Stems and leaves are bleached by

Phytophthora .

Phytophthora root rotPhytophthora root rot can kill

seedlings and established plants in wetor slowly drained soils. The disease is

especially prevalent among newseedlings in cool, wet soils. Infectionoccurs as plants emerge; they appear

water-soaked and then collapse andwither. The disease appears on estab-lished plants in poorly drained soilsand where water stands for 3 days orless. Plants wilt, then leaves, especiallylower ones, turn yellow to reddish

brown. Lesions develop on the roots.In severe cases, taproots may rot off at

the depth of soil water saturation(frequendy 1 to 6 inches below

ground surface). Plants may die withinone week of infection or linger onwith reduced root mass and growth

rate. Often Phytophthora root rot isnot discovered until the soil dries and

apparendy healthy plants begin wiltingbecause their rotted tap roots areunable to supply adequate water.

Many highly resistant varieties areavailable for poorly drained soils.

As the disease progresses (left to right), lesions develop and the taproot

rots off.

30 - A A A MANAG M NT G u D


Root-lesion nematodesRoot.lesion nematodes

Root-lesion nematodes reduceyield and thin stands. The parasitic

nematodes are microscopic wormsthat feed on root hairs, feeder roots,and nitrogen-fixing nodules of alfalfa.

Root-lesion nematodes reduce thealfalfa plant's ability to take up soilnutrients and fix nitrogen. Plants

appear unhealthy and stunted, usuallyin spotty areas within an otherwise

healthy stand. Nematode populationscan be reduced by rotating to rowcrops or fallowing for 2 months

following incorporation of forage cropresidue. Moderate resistance will soonbe available in some varieties.

.severe IN!i! moderate mild

Seedling death due to root-lesion nematodes.

Stunted plants and stand thinning caused by root-lesion nematodes



Sclerotinia

7

cJ=1

4\"..

-",~,

.severe III moderate D

SclerotiniaSclerotinia crown and stem rot is

most damaging to seedling stands,especially those seeded in late summer.The first symptoms appear in the fallas small, brown spots on leaves andstems. During the cool, wet weather of Arrows point to white fluffy masses at the base of a stem.

early spring, the crown or lower partsof individual stems soften, discolor,

and disintegrate. As infected parts die,a white, fluffy mass grows over thearea and hard, black bodies, known assclerotia, form. These bodies remainon the surface of the stem or becomeimbedded in it. Infection will spread if

cool, wet weather prevails duringspring, rapidly thinning stands. Springplanting reduces incidence of thedisease. Plowing buries sclerotia andreduces its ability to infect new plant-

ings. No resistance is available yet.

Sclerotia on stem

Softened and discolored stems.

32A L F A L F A MANAG M NT G u D


Spring black stem

Distribution ond severity

Summer black stem

-

~

~

~

'V

.severe III moderate D mild .severe moderate D mIld

Spring black stemSpring black stem occurs in the

northern United States during earlyspring and reduces forage yield andquality. Many small, dark brown spotsdevelop on the lower leaves and stems.Leaves, especially lower ones, turnyellow, wither, and fall off. Lesions on

stems enlarge and may blacken largeareas near the base of the plant. Severeinfestations girdle and kill the stem.

The plant dies when infection spreadsto the crown and roots. Cutting thestand at early stages of maturity will

reduce leaf loss and disease prevalence.Currently available varieties have vari-able levels of resistance, but none are

characterized for this disease.

Lesions may enlarge to girdle stems andkill the plant.

Leaf lesions (left) first appear on lower leaves

Summer black stem

.Summer black stem occurs duringhot, humid weather, reducing forageyield and quality. The disease firstaffects the base of the plant andprogresses up the stem, causing leavesto fall off. Leaf spots are brown withirregular margins and oftensurrounded by a diffilse yellowmargin. Reddish to chocolate brownoval lesions form on the stems and

merge to discolor most of it. Earlyharvest may reduce losses. Currentlyavailable varieties have little resistance.

O N 33PRODUCT


Verticillium wilt

~

~~

xe'

mild.severe. moderate

Leaves show early symptoms of infectionNote v-shaped yellowing and scattered

bleaching.

At later stages of infection, dead leaves appear on green stems.

Verticillium wiltVerticillium wilt can reduce yields

up to 50% beginning the secondharvest year and severely shortensstand life. Early symptoms include

v-shaped yellowing on leaflet tips,sometimes with leaflets roiling alongtheir length. The disease progressesuntil all leaves are dead on a greenstem. Initially, not all stems of a plantare affected. The disease slowly invadesthe crown and the plant dies over aperiod of months. Root vasculartissues mayor may not show internal

browning. Many varieties are resistantto this disease.

The following measures minimizethe chances of introducing the fungusto an area and spreading the disease

between and within fields.1. Plant resistant varieties.

2. Practice crop rotation. Deep plow

Verticillium-infested fields and donot plant alfalfa for 2 to 3 years,

although a highly resistant varietycould be planted immediately.Corn and small grains are impor-

tant non-hosts. These crops shouldfit well into a rotation with alfalfa.

Red clover is a questionable host,so don't grow red clover on

Verticiilium-infested land.

3. Harvest non-infested fields first.Then harvest infested fields at the

hard-bud or early flower stage.

Early harvest can limit some yieldand quality losses caused by

Verticillium wilt and can slow thespread of the wilt fungus in a field.

Browning in roots.

34A L F A A MANAG M NT G u D

INSECT MANAGEMENT

Alfalfa weevilA Ifalfa weevil larvae chew and

skeletonize leaves. Large larvalpopulations may defoliate entire

plants, giving the field a grayish color.Damage normally only occurs to thefirst harvest but both larvae and adultsmay damage regrowth when popula-tions are high, resulting in both yield

and stand loss.Larvae are slate-colored when

small, but bright green when fullgrown (% inch). They have a whitestripe down the back and a black head.

Although larvae are present from Maywell into the summer, peak feedingactivity falls off by mid-June.

Severely damaged plants appeargrayish-brown.

When full grown, the larvae spinsilken cocoons on the plants, within

the curl of fallen dead leaves, or withinlitter on the ground. They change intoadults in lor 2 weeks.Adults are dark

gray to brown snout beetles measuringY16 inch in length. There is a distinctdark shield-like mark on the back.After feeding a short time, most leavethe field and enter a resting periodthat lasts until fall. In the fall, theyreturn to the alfalfa field and lay a feweggs before the onset of cold tempera-tlirl:-s. In northernmost states, fall egg

laying is insignificant; most eggs arelaid the following spring.

Begin checking alfalfa fields forsigns of weevil feeding around mid-May in northernmost states and earlier

farther south.

Leaves skeletonized by alfalfa weevillarvae.

Table' 0. Economic thresholds for alfalfa weevil larvae in

early bud stage alfalfa.

Adult weevils bear a distinctive shield-like mark on the back.Larvae are slate-colored when small but turn bright-greenwhen full grown.

Source: Peterson, Danielson, and Higley, University of Nebraska, 1993

Treat fields when 40% of the planttips of the first crop show obvioussigns of damage. This does notmean 40% defoliation. If damage

occurs within 7 to 10 days of thesuggested harvest date, harvest the hayas soon as possible; otherwise spray thefield as soon as possible. Many weevillarvae are killed during harvesting.

An alternative approach for decid-ing when to treat involves comparingthe control costs to the forage value.Use table 10 to find where these twovalues intersect for the number of

alfalfa weevil larvae needed to justifychemical control.

If you've harvested early because

of developing alfalfa weevil problems,or if substantial weevil damage has

occurred, check the stubble carefullyfor signs of damage to new growth.Some fields may fail to green-upbecause adults and larvae consumenew crown buds as fast as they areformed. Examine the stubble, the soilsurface around alfalfa plants, and underleaf litter for larvae and adults. If they

are present and if plants show no signof regrowth within 3 or 4 days afterharvest, spray the stubble as soon as

possible.Treat also if new growth has started

and feeding damage is apparent on 50%of the growth and/ or you find 6 to8 weevils or more per square foot.


AphidsAphids cause stunting and yellow-

ing of alfalfa resulting in yield loss.Heavily infested plants wilt during the

hottest parts of the days.Green pea aphids or the spotted

alfalfa aphids, which are yellow andfaindy dark spotted, congregate on

stems and leaves and suck plant juice.Spotted alfalfa aphids have beenuncommon in the upper Midwest for

many years. Parasites and disease keepthe pea aphid in check most years,

though population explosions periodi-cally occur. Pea aphids are a majorproblem in the hot and dry westernUnited States. Treat pea aphids when

numbers exceed 100 per sweep, partic-

ularly during dry periods.

Aphids congregate on leaves and stems

to suck plant juice.

Common adult blister beetles.

Blister beetlesBlister beetles in alfalfa hay can

cause sickness and death in livestock,

particularly horses. Blister beetlescontain cantharidin, a chemical irritant

that can blister internal and externalbody tissues. Although there are fewdocumented cases of fatalities in cattle

and sheep, cantharidin-contaminatedhay is deadly to horses.

Blister beetles are a seriousproblem in southern and westernstates, and an occasional problem in

tht: upper Midwest, particularly duringdrought years or the year followingdrought. The several species present inthe Midwest vary in size and color, but

are easily recognized by their elon-gated, narrow, cylindrical, soft bodies.The "neck" area is narrower than onmost beetles. Sprays are generally not

effective because cantharidin is a verystable compound and the dead beetlescan be picked up in the hay. Becausebeetle populations tend to buildthroughout the season, especially in

the south, horse owners shouldconsider buying first-crop and earlysecond-crop hay during high infesta-

tions of blister beetle.

36A L F A A MANAG M NT G u D

Adult clover leaf weevils are twoto three times larger than alfalfa

weevils. They are % inch long, darkbrown flecked with black, and have alighter colored stripe extending alongeach side of the wing covers. This

insect normally leaves the fieldsshortly after the first cutting andreturns in late summer to feed and lay

eggs before winter. There is onegeneration per year and they overwin-ter mostly as partially grown larvae.

Treatment is rarely warranted forclover leaf weevil larvae. Managementof alfalfa weevils will also control thisinsect. However, adult clover leafweevils can cause damage by feedingon the green stems and regrowth afterthe first cutting. Large populations cancause extensive feeding damage, scar-ring the stems and rapidly consumingnew foliage as it is produced. This typeof injury is more common during drysprings when regrowth is slow andweevils are abundant. Treatmentshould be considered if the hay doesnot begin to regrow in 3 to 4 daysafter cutting and weevils are present in

the field.

Clover leaf weevilClover leaf weevil larvae eat

alfalfa leaves, usually beginning withthe foliage around the base of the plant.Crop injury occurs mostly before thefirst cutting, but it is usually insignifi-cant compared with the injury causedby the alfalfa weevil. Clover leafweevils are active at night and on

cloudy days. During sunny days, theyhide around the base of the plant.

Larvae are slate-colored whensmall, but bright green when full

, '8fown. They are similar in appearance

to alfalfa weevil larvae except that the

head is light brown and the whitestripe down the center of the back isoften edged with pink. Full-grownlarvae are about Y2 inch long.

Adult clover leaf weevils are dark brownflecked with black.

Clover leaf weevil larvae are similar to alfalfa weevillarvae but have light brown heads rather than black.

Larvae hide around the base of the plant during sunnydays, preferring to feed at night and on cloudy days.

37PRODUCT ON

GrasshoppersGrasshoppers can overwinter as

eggs or adults, depending upon the

species. Populations tend to buildduring the season, followed by move-ment of the grasshoppers into culti-vated crops from grassy or weedy areaswhere they overwintered. It is impor-tant to detect infestations while the

grasshoppers are small and concen-trated in overwintering sites.

Several species can feed on alfalfa.Problems occur mainly in the westernUnited States and during droughtyyears in the Midwest. Grasshoppers

rarely cause economic damage in mostareas of the Midwest and should beconsidered a minor pest.

Begin spot-checking overwinter-ing sites during June. Estimate thenumber of grasshoppers per squareyard while walking through theseareas. Insecticide use is not suggesteduntil populations reach 20 per squareyard in field margins or 8 per squareyard within an alfalfa field. If econom-

ically damaging infestations aredetected while the grasshoppers arestill concentrated, spot treat the area to

protect alfalfa fields.

Clover root curculioThe clover root curculio is a

potentially serious pest of alfalfa.Although this pest can be found inmost alfalfa fields, high populationsand serious damage have been local-

ized and sporadic. However, even small

populations may contribute to standdecline. At this time there is no reliablemethod of damage prediction orcontrol.

Adults are black to dark brown,blunt-snouted weevils that are approx-imately ~ inch long and Y16 inchwide. The surface of the beetle's bodyis deeply "punctured." Females lay eggson the lower parts of stems, on lower

leaves, or on the soil surface. Larvaehatch from these eggs and enter thesoil through surface cracks.

There is only one generation per

year. Adults lay eggs in fall or spring,and hibernate over the winter. Eggshatch in the spring, and egg-laying is

usually complete by mid-June. Newadults emerge in June and July and liveabout a year.

Adult curculios injure plants by

chewing the margins ofleaves, creat-

ing crescent-shaped notches, or bychewing the stems and leaf buds of

young seedlings. Feeding damage canweaken seedlings, causing poor growthor death. Mature plants are not at riskunless populations are exceedingly

high.

Long brown furrows on the taprootcaused by curculio larvae feeding.

Larvae do the greatest damage,and such damage can be cumulativeover the years that a field exists. Newly

hatched larvae feed on nodules andsmall rootlets and chew out portionsof the main root. Feeding on the mainroot leaves long brown furrows and

may partially girdle the plant.

Grasshoppers are best controlled when they are in fieldborders and before they move into the alfalfa.

Damage from clover rootcurculios is believed to shorten stand

life, contribute to winter kill, andprovide an avenue for entry by disease

organisms. No commercially accept-able control techniques are available.

However, do not plant alfalfa backinto old, infested alfalfa stands because

curculio damage can destroy the newstand. Also, since adults migrate

primarily by crawling from field tofield, avoid seeding alfalfa next toolder stands.

38A L F A L F A MANAG M NT G u D

Crinkled leaves typical of plant bug

-damage.

Plant bugsPlant bugs extract plant sap with

their tube-like mouths. High popula-tions can stunt alfalfa growth or

crinkle and pucker leaves. However,these symptoms may be caused byother factors so be sure to positivelyidentify the problem before treating

plants.The two plant bugs that are

particularly important to alfalfaproduction are the tarnished plant bugand the alfalfa plant bug. The adulttarnished plant bug is Y4 inch long andbrown. Nymphs are green with blackspots on the back. Adult alfalfa plantbugs are % inch long and are lightgreen. Nymphs are green with red

eyes.Treatment is suggested if there are

three plant bug adults and/ or nymphsper sweep on alfalfa less than 3 inchestall; treat when there are five or moreadults and/ or nymphs per sweep ontaller alfalfa. If damage occurs within7 to 10 days of the suggested harvestdate, harvest the hay as soon as possi-ble; otherwise spray the field as soon as

possible.

Adult tarnished plant bugs are Y4 inch long

Alfalfa plant bugs are 3jB inch long.

-39PRODUCT ON

Table 11. Economic thresholds for

control of potato leafhopper. (Treat when

leafhopper densities reach these thresholds.}

Potato leafhoppersPotato leafhoppers are mid- to

late-season alfalfa pests that migrate tonorthern states from southern areas.

First-crop alfalfa harvested at theproper time in the Midwest usually

escapes damage. However, monitorsubsequent crops as well as newseedlings for leafhoppers.

These small (~ inch), green,wedge-shaped insects suck sap fromplants and inject a toxin into theleaves, creating a yellow wedge-shapedarea on the tip of leaflets. Severelydamaged plants will be stunted andchlorosis will appear on all leaves if

leafhoppers are not controlled. Damagefirst appears on field perimeters.

Alfalfa stands suffer yield andquality losses before any yellowing isvisible. To detect leafhoppers beforesymptoms appear, use an insect sweepnet. Refer to table 11 to determinewhen to treat alfalfa fields.

Severely damaged plants are stunted and chlorotic. Leafhopperburn appears first as yellow wedge-shaped areas on the tips ofleaflets.

Adult leafhopper {actual size 1;8 inch).

D40 MANAG M N T G uA A

Spittlebug nymphs appear in early

May. These soft, orange or green bugscan be found in white spittle masses in

leaf axils, and later in the clumps ofnew growth at tips of stems. They suck

plant juices and stunt but do notyellow the alfalfa. Alfalfa can support a

tremendous population of spittlebugs

without yield loss and they usuallyhave no economic impact. Treatmentis suggested if there is an average of

one spittlebug per alfalfa stem.

Treatment should be considered if

the hay does not begin to regrow in4 to 7 days after cutting and larvae are

present in the field.

WHEN TO ROTATEFROM ALFALFATo decide when to rotate from

alfalfa, you'll need to evaluate stand

density and yield relative to yourneeds.You'll also want to factor inrotation requirements, farm plan, total

acreage of forage needed, and abilityto reseed. Because most of thesefactors are farm specific, this sectionfocuses on the relationship between

stand density and yield.Alfalfa has a tremendous ability to

produce maximum yield over a widerange of stand densities. New seedings

should have at least 25 to 30 plants persquare foot the seeding year. Standsgradually thin and weeds may invaderapidly. Weedy stands force the choiceof using herbicides, which increasesproduction cost, or of harvesting much

lower quality forage.The decision to rotate from alfalfa

should be based on yield potential ofthe stand. Plant density is a poor esti-mator of yield potential because anindividual plant may have few shoots

and contribute little to yield. Stemdensity is the best estimator of yieldpotential. However, you may need tobase your decision on plant density if

assessing the stand in spring before

stem counts are available.Spittlebug froth

,

Variegated cutworm larvae can cause serious damage

on regrowth after alfalfa is cut.

Variegated cutworm larvae feed

on leaves and stems. Serious damagecan occur on regrowth after the alfalfais cut and larvae feed under the

protection of drying windrows. Theyalso can cut seedling plants in newstands. Larvae are variable in color,ranging from tan to greenish-yellow to

almost black with a row of small

yellow, dagger- or diamond-shapedspots down the center of the back.Tpere are three to four generations a

year.

p R O D U C T 0 N 41

To determine season yield poten-tial of a field, use the relationship infigure 13. Stem density can becounted any time after plants are 4 to6 inches tall. Try to count only stemsthat would be cut by a mower. With

experience, visual estimates are usuallysufficiently accurate. Note that thiscalculates yield potential; actual yieldwill probably be less due to moisture,soil fertility, and other managementpractices that limit yield.

The best time to make stand deci-sions is in the fall. During the last

growth period record stem density.Then dig a random sampling of plantsand assess root health (see related

advanced technique). Typically, standsthat fall below 40 stems per squarefoot or three to four healthy plants persquare foot are no longer profitable,although the critical yield range willvary with individual farming opera-tions. Marginal stands that are healthyplay be kept while fields with highlevels of crown rot will decline rapidlyand should be considered for rotationalong with low yield potential fields.

Figure 13. Alfalfa stem count and yield potential.

7

"0-0;

Source: Undersander and Cosgrove,University of Wisconsin, 1992

0 10 20 30 40 50 60 70

stems per square foot

yield = (0.10 .stems) + 0.38

Varying degrees of crown rot. From the left: the first two arehealthy, the next three show moderate injury, and the remainingfive show severe crown rot. plants with severe rot are unlikely tosurvive another year.

6

\.i~ 5.-Q)

>-I..I.. u 4Q)O= O III 3

ES...

>-- 2I..

~

0

The final step to profitable alfalfa

production is to set goals for

forage quality and use the appro-

priate harvest techniques to mini-

mize field losses and maximize

tonnage of high quality forage.

This recognizes that high quality

forage is profitable to animals

that can use the quality but that

tradeoffs exist between forage

quality, yield, and stand life.

H A R V E s T 43

Quality standards are presented intable 12. (Forage quality terms are

defined ar the end of the Harvestsection.) Use the RFV index to allo-cate the proper forage to the properlivestock class (figure 14). Performance

ofhigh-producing dairy cows is mostlimited by intake of digestible drymatter and prime hay or haylage isrecommended. Grade 1 is recom-mended for dairy cows after the firsttrimester, heifers, and stocker cattle.

Table 12. Quality standards for legume, grass,

and grass-Iegume mixture.

FORAGE QUALITYA lfalfa is superior to other forage

crops because it is high in crudeprotein and energy, reducing the need

for both types of supplements inrations. The superior intake potentialallows for greater use in rations ofhigh-producing dairy cows.

What quality forageis needed?

The nutrient need of an animal

depends primarily on its age, sex, andproduction status (figure 14).Maximum profit results from match-ing forage quality to animal needs.

Lower-than-optimum quality resultseither in reduced animal performanceor increased supplement costs.

Conversely, feeding animals higherquality forage than they need wastes

unused nutrients that were expensiveto produce and may result in animal

health problems.

IRFV = relativefeed value; ADF = acid detergentfiber;NDF = neutral detergentfibel:

Figure' 4. Forage quality needs of cattle and horses.

100 110 120 130 140 150 160

relative feed value

44A A A MANAG M NT G u D

Forage quality is also influencedby the time of day alfalfa is cut. Plantsconvert sugars and starches to energyin a process called respiration.

Respiration after cutting lowers foragequality and is stopped only by dryingthe forage. Therefore, the best time tocut alfalfa is in the morning to speed

drying and capture sugars and starchfor higher quality hay and haylage.

HARVEST MANAGEMENTForage yield, quality, and stand persis-

tence are all major considerations inthe development of a profitableharvest management program.Increased awareness of the nutritionalvalue of high quality alfalfa in terms of

potential savings of energy and proteinsupplements has caused many to re-evaluate current harvest strategies.

Plant growth and

forage qualityUnderstanding how alfalfa grows

and its relationship to forage yield,

forage quality, and carbohydrate rootreserves is critical to production of

high-quality hay. Alfalfa is a perennialplant that stores carbohydrates (sugarsand starches) in the crown and root.

Plants use these carbohydrate reservesfor regrowth both in the spring andafter each cutting. When alfalfa is 6 to8 inches tall, it begins replacing carbo-

hydrates in the root (figure 15). Thiscycle is repeated after each cutting.High levels of carbohydrate reserves

encourage rapid regrowth after cuttingand winter survival. Regrowth beginswith buds either on the crown or atthe base of old shoots (after first

cutting). Alfalfa regrowth for secondand later cuttings begins while growth

from the previous cycle is beginningto flower. Cutting at late maturity can

remove shoots for the next cutting and

delay regrowth.Figure 16. Forage yield relative to quality at different growth stages.

Figure 15. Carbohydrate content of alfalfa roots.

vegetative bud first flower full-flower post-flower

oe

growth 6-8 inchinitiation height

bud fullstage bloom

Forage growth is most rapid until

early flowering (figure 16). Foragegrowth continues until full flower, butoften leaf losses from lower stems slow

yield increase after first flower. Alfalfaforage quality is greatest in early vege-tative stages when the leaf weight is

greater than stem weight; however, byfirst flower, and sometimes earlier,stem proportion exceeds that of leaves.

Higher alfalfa yields after early flowercan be attributed mainly to more low-

quality stems. As cutting intervalincreases or as plants are harvested atlater stages of maturity, yield per

cutting increases but quality of theforage harvested decreases.

Temperatures during growthaffect forage quality. Alfalfa grownduring cool weather tends to produce

higher quality forage than alfalfagrown during warm periods, assumingall harvests are equally weed-free andat the same maturity stage.

H A R V S T 45

High quality. When harvestingfor high quality the first cutting should

be taken by an early calendar dateappropriate for the region. Theremainder of cuttings should be takenat midbud, generally 28- to 33-dayintervals early in the season and longernear the end of the season (figure 17).Cutting for high quality forage meansthat forage must be harvested within a3- to 4-day period. No late-fall cuttingshould be taken in northern states,although it should be taken in regionswhere needed to decrease insect over-wintering. Yield of the late fall cutting

is generally low and removal of thisforage will increase winterkill and first

cutting yield the next spring.

CuHing scheduleSelection of a harvest schedule

begins with the decision on quality offorage desired. Growers desiring allhigh quality alfalfa will shorten standpersistence and decrease yield. Harvestschedule decisions include number ofcuts per season, date of cut, stage ofmaturity, interval between cuts, andcutting height. The link between the

stage of maturity and yield, quality,and persistence makes it apparent whygrowth stage is frequently used todecide when to harvest alfalfa. Keyingharvests to specific stages of develop-ment also takes into account thevarying effects of changing environ-ments and variety maturity rates. Ashortened growing season in northernstates dictates combining calendardates and stage of development into

harvest strategies.Maximum persistence. If

harvesting for maximum persistence,cut alfalfa between first flower and25% flower. This is approximately35 to 40 days between cuttings(figure 17). The system has a slightlywider harvest window and longercutting interval than when cutting forhigh quality because the emphasis is

on high yield.

"~

""5>

]~".~Df

5!256!1 35394569283545 35 39 47 62 63

cutting intervals(days after previous cut)

Source: Adapted from Brink and Marten, University of Minnesota, 1989

Figure' 7. Cutting schedules for different management goals.

cutting interval (days after May 25)

10 20 30 40 50 60 70 80 90 100110120130 140150160-1-rt~ -1--1---l

persistence 35-40 days

I I

~0-35 days

recommendedtime to cut

qualityIi

28-33 days

I I28-33 days

30-35,doys

yield and quality

June 1 July 1 Aug.l Sept. 1 Oct. 1 Oct. 27

High yield and high quality.For harvest schedules to provide thehighest yield of high quality forage,the first two cuttings must be timely.During this time forage qualitychanges most rapidly and short delaysmean low quality forage (figure 18).Take the first cutting at bud stage orbetween May 15 and 25 in Minnesotaand Wisconsin, and earlier farthersouth. Take the second cutting 28 to33 days after the first cut or rnidbud,whichever is earlier, and take subse-quent cuttings at 38- to 55-day inter-vals or at 10 to 25% bloom. An early

first harvest followed by a shortcutting interval gives a high yield ofquality forage (figure 17) while letting


one cutting mature to early flower will

increase root reserves and stand persis-tence. The forage quality of alfalfa doesnot change as rapidly in later cuttings

as in earlier cuttings so later cuttingsmaintain quality to later maturitystages (figure 18). This slower qualitychange allows a harvest window of

7 to 10 days. Additional cuttings maybe taken if time permits before therequired 6- to 8-week rest period priorto the first killing frost. In northernregions, delaying the third cut oftenresults in alfalfa flowering during the6 weeks before the first killing frost(between September 1 and October 15

in northern states). To prevent loss ofpersistence, delay harvest until mid- tolate October, regardless of the stage ofmaturity. However, this late-fall cuttingwill shorten stand life and decreaseyield the next spring, so should be cuthigh (at 6 inches) or not harvested ifadequate forage is available. Minnesota

researchers found that highest yieldscame from three cuttings during the

growing season with a late-fall cutting.Using this cutting schedule, thepercentage of total yield cut at "primestandard" (>150 RFV index) ranged

from 32 to 75%.

FALL MANAGEMENTF all management of alfalfa involves

assessing the risk of winter injuryand the need for additional forage. The

risk of winter injury to alfalfa dependson uncontrollable environmentalfactors (snow cover, temperature, andsoil moisture) and controllable factors(variety, soil fertility, seasonal cuttingstrategy, stand age, and cutting height).

Uncontrollableenvironmental factors

~ Periods of cool temperatures arerequired in the fall for alfalfa todevelop resistance to cold temper-atures. Sudden changes from warm

to cold reduce hardening.

.A snow cover of 6 inches or moreprotects alfalfa plants from severecold. During winters withoutsnow cover, soil temperatures canfall below 15°F; injuring or killing

plants.

.Even hardy varieties can be injuredor killed by 2 weeks or more oftemperatures below 5° to 15°F.

.Warm fall weather (40°F orhigher) and midwinter thaws causealfalfa to break dormancy and haveless resistance to freezing.

.Excessively moist soil in the fall

reduces hardening and predisposesalfalfa to winter injury. Excesssurface and soil moisture can lead

to the formation of ice sheets. Icesheets smother plants by freezingthe soil before the plant has hard-ened. Ice sheets also allow highconcentrations of toxic substances-

such as carbon dioxide, ethanol,and methanol-to accumulate. Icesheeting frequently occurs in

conjunction with midwinterthawing and is more prevalent in

poorly drained soils.

Controllable factors.Select alfalfa varieties with good

winterhardiness and moderateresistance to several diseases. Thesevarieties will better tolerate late-fall cuttings-

.Soil fertility management is vitallyimportant for maintaining produc-tive alfalfa stands. Potassium(potash) is particularly importantfor developing plants that havegood winter survival.

.Greater harvest frequency andstand age at harvest increases thepotential for winter injury whenfall cuttings are taken. When the

interval between previous cuttingshas been 35 days or less, avoidharvesting during the critical fallperiod 6 weeks before the firstkilling frost (between September 1and October 15 in northern states,later in southern states). This allowsplants to enter winter with higher

root carbohydrates (figure 15).

.Young alfalfa stands survivewinters better than older standsdue to lower disease infestationand less physical damage.

.Stem and leaf stubble remaining in

the late fall catch snow and insu-late the soil. Alfalfa harvested inOctober should have a 6-inchstubble left and uncut strips to

reduce risk of winter damage.

Making the decision to cut in thefall requires using the above factors toestimate the risk of winter injury to

alfalfa and weighing it against the needfor forage. Use the questions andscoring system shown in table 13 toassess risk of winter injury. Then assessrisk potential with demand for hayfrom a fall harvest.

-47HARV ST

Table 1 3. Calculate your risk of alfalfa winter injury.

points score Harvesting the late fall cuttingwill increase tonnage for the seasonand may be more profitable where riskpotential is low (see table 13) and goodsnow cover or less severe winters occur.

Minnesota research shows that takinga fourth cutting after October 15 ismore profitable than three cuts bySeptember 1 (6 weeks before killingfrost) or four cuts by September 15with no fall cutting for a 4-year-oldalfalfa stand. In five-cut systems, thefirst cutting yield the next spring waslowered by approximately the sameamount as the yield from the fallcutting. Root rot was increased and,therefore, stand life was also shortened.

Fall culling risk

If you score: Your risk is:

3-7 low/belowaverage

8-16 moderate/average

17-27 high/above average

28 or more points very high/dangerous

Source: Adapted from C. S. Shaeffel; University of Minnesota) 19901 Dates listed are for northernmost states; states south of that area should use later dates.

48 A L F A L F A MANAG M NT G u D

Table 1 4. Summary of good hay-making practices.

Source: Pitt, CorneIl University, 1991

Figure' 9. Dry rl:'atter losses during harvest and storage relative to forage

storage loss

harvest loss~ 40

III41III

..2 30

40'I I field-

wilted

silage

direct-cut

silage

30

HAY AND SILAGEMANAGEMENTH ay-making and silage-making differ

in how the moisture content ofalfalfa is employed as a strategy in

preservation. Fresh alfalfa containsabout 80% moisture. Soluble sugarsand proteins are dissolved in the forageliquid. When concentrated throughwilting, this ')uice" provides an idealmedium for the growth of yeasts,molds, and bacteria and for rapidactivity of plant enzymes. Appropriatebacterial growth can result in fermen-tation that produces lactic acid andpreserves the material as silage. When

forage is dried to hay before harvest,water in the forage evaporates, result-ing in a higher concentration of nutri-ents in the remaining liquid where cell

growth and enzyme activity are

restricted.Losses. Each step in the preser-

vation process-mowing, raking,chopping, baling, storing, and unload-ing-causes a loss of forage dry matter(figure 19) .Some losses result frommechanical action; others are biologi-cal processes. Total losses from cuttingto feeding are 20% to 30% of thestanding crop dry matter in typical hay

and silage systems. In hay-making,most of the losses result from mechan-ical handling and weather damage inthe field. In silage-making, most losses

occur during storage and feed out.Quality changes. Most of the

dry matter lost from forage duringharvest and storage has high nutritionalvalue. More leaves than stems are lostduring hay-making, and most protein-and energy-rich nutrients are concen-

trated in the leaves. Biological processesin silage-making use the most readilyavailable nutrients, such as plant sugars.Thus, in both hay and silage systems, the

changes that occur are often detrimen-tal to the quality of the final product.

20 20

..QI=DE>-..

"010 - 10

..."'Q)>..o

..c

O~

0 0

10

moisture content at harvest.

50 --50

I I80 70 60 5040 30 20

moisture when harvested (%)

Source: Hoglund, Michigan State Universit~ 1964

H A R V E s T 49

Dry matterlosses and quality changes cannot beeliminated in hay preservation, butthey can be minimized by using good

management practices. The practicesfor good hay-making are summarizedin table 14.

Quality losses during hay-making.Respiration uses plant sugars, a

process which increases NDF andADF and decreases digestibility.

.Rain damage on hay before balingleaches soluble nutrients (protein

and carbohydrates). NDF andADFincrease; digestibility and crudeprotein decrease. Additional qualityis lost from leaf shattering.

.Rainy weather causes delays inharvest. NDF and ADF increase;digestibility and crude proteindecrease.

Good hay preservation dependsprimarily on handling and harvestmanagement. The drying rate, mechan-ical handling of the forage, and the

moisture content at baling all impactthe quality of the hay. With proper

management, little or no deteriorationtakes place in the hay during storage.

Quality losses during

silage-making.Dry matter loss increases ADF and

NDF; lowers digestibility and drymatter intake by animals.

.Loss of leaves decreases crude

protein.

.Soluble protein can increase in

silage during fermentation.Animals on high-performancediets (dairy or growing beef) needinsoluble protein, so performanceis adversely affected.

...

.6

forage moisture content at ensiling(% wet basis)

Source: Adapted from Muck, USDA, 1993

50 A L F A L F G u DA MANAG M NT

.Acid detergent fiber:crude proteinis protein made insoluble throughthe heating during fermentation.Up to 14% is beneficial; more than14% reduces protein availability to

the animal.

Unavoidable losses include those

due to field losses, plant respiration,and primary fermentation. Avoidablelosses occur from effiuent, anaerobicfermentation, and aerobic deteriora-tion in storage structure. Estimates of

unavoidable dry matter losses rangefrom 8% to 30%; avoidable losses from

2% to 40% or higher. The importanceof quickly achieving and maintainingoxygen-free conditions has led to

improved equipment and techniquesfor precision chopping, bettercompaction, rapid filling, and

complete sealing.

Alfalfa is more difficult than cornto ferment properly because alfalfa

contains fewer soluble carbohydratesrelative to protein. For an outline ofgood silage management practices see

table 15.

Feeding considerationsof hay and haylage

A widely used rule of thumb in

formulating rations for lactating dairycattle is that one-third of the diet beforage, one-third concentrate, and theremaining one-third either forage orgrain, depending upon the quality of

the forage fed. By feeding high qualityalfalfa in place of lower quality forages,dairy producers can decrease theamount of concentrates that must befed and can increase the utilization of

forage. The lactation study in table 16,

shows concentrates cannot supply the

energy required at high productionlevels when the quality of the forage is

too low.How alfalfa is harvested and

preserved has been the focus of many

research studies, but no clear advantagein animal performance has beendemonstrated for harvesting andstoring alfalfa either as hay or haylage.Harvesting alfalfa at higher moisturecontents will decrease field losses butwill increase storage losses unlessforage is kept in airtight silos or silage

tubes.

1 5. Summary of good alfalfa silage practices.

Source: Pitt, R.E. , Cornell University, 19901 TLC = theoretical length of cut. Chop alfalfa silage at ~-inch TLC.

H A R V E s T 51

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