Several Herbicides Tested for Wild RadishControl in Wheat

Wild radish, a member of themustard family, is a troublesomeweed in grain crops in Alabama. Ithas been reported that wild rad-ish is toxic, particularly the seeds, tofarm animals and reduces their per-formance. The seed are difficult toclean from grain due to similarity insize and shape.

Results of field experiments in1988-89 and 1989-90 at the PlantBreeding Unit, Tallassee, illustratethe competitiveness of wild radishwith wheat. With a single wildradish plant per 10 square feet(4,356 plants per acre), a lossequation indicated wheat yieldloss of 17.8 percent for 1988-89 anda 1.4 percent loss for 1989-90. Thedifference reflected the differ-ence in growth of the wild radish.

Research since 1987 indicates the

potential for herbicidal control.First-year findings with Har-mony Extra@ indicate that a sur-factant was needed for best wildradish control and that tank mix-ing Harmony Extra, X-77 non-ionic surfactant, and liquid ni-trogen increased wheat injurybut degree of injury was accept-able and yield was not affected.Wild radish control in this ex-periment was good to excellentwith the early March application.

Comparisons of fall versus springapplication of Harmony Extra as wellas fall/spring sequential applica-tions show excellent control withfall application and poor controlwith spring application. Excellentcontrol was also achieved with thefall/spring sequential applicationof Harmony Extra and the spring

RESEARCH UPDATE

±1991GRAYCROP

SS

application of Harmony Extra plus2,4-D.

In another test, Amber@ (0.026and 0.013 pound), Harmony Ex-tra (0.042 and 0.021 pound), Ex-press@ (0.012 and 0.008 pound),Buctril@ (0.75 and 0.50 pound),MCPA (0.75 and 0.50 pound), and2,4-D (0.75 and 0.50 pound) provided95 percent or greater control at anOpelika location when applied aloneto weeds no larger than 6-inch ro-settes. However, Buctril, HarmonyExtra, and Express applied alone atHeadland provided less controlbecause weeds were larger at ap-plication. Tank mixing Buctril, Ex-press, or Harmony Extra witheither MCPA or 2,4-D improvedcontrol of the larger wild radish.

Results indicate the need to applyherbicides in November or Decem-ber for effective wild radish control.Only Buctril, Harmony Extra, andMCPA were labelled for use in 1990.

R.H. Walker, D.R. Wyatt,and J.S. Richburg III[

Tillage and Cover Crops Affect Corn N Fertilizer Efficiency

An AAES study at the E. V. SmithResearch Center was designed todetermine if cover crops could,alone or in combination with falldeep tillage (paraplowing),ameliorate soil compaction and

increase crop growth and yield po-tential. The ultimate aim was toimprove N use efficiency of a sub-sequent corn crop.

Winter cover crops of crimsonclover, rye, and Tifwhite-78 white

lupin were planted following eitherdisking or disking plus paraplowing.A winter fallow treatment was alsoincluded.

Tifwhite-78 lupin, a winter hardycontinued on page 2

ALBtA er CLURLXEIEN T oN ABR UIESTLoELT.PoisDRETRAUUNUNVRITIALBM

Tillage and Cover Crops, continued

legume that has potential as a feedgrain, was included because re-search in Australia has shown thatanother species of lupin, bluelupin, has the capacity to act as a"biological plow" to improve soilstructure on compacted soils.

The paraplow is a conservationtillage implement with an offsetblade at the end of a straightshank. It effectively disrupts thesoil to a depth of 17 inches with aminimum of surface soil disrup-tion.

Prior to planting corn, the covercrops were killed with a burndownherbicide and disked into the soilto a depth of 4 to 5 inches. Thecorn was then fertilized with 0, 50,100, or 150 pounds N per acre.

None of the cover crops appearedto work as "biological plows" toimprove soil structure. The rye andclover slightly increased soil com-paction in the disked zone.

Paraplowing had a strong resid-ual effect in alleviating soil compac-tion for the subsequent corn crop,but tended to reduce yields, table 1.This effect was greatest during theextremely wet growing season of1989. Paraplowing reducedearlea f N, table 1, and increased soilwater content following rainfall.

Table 1. Effect of Cover Crop Tillage on CornEarleaf N and Grain Yield, 1988-90 Average

Tillage Earleaf N Grain/acre

Pct Bu.

Disk ........................ 2.56 89Paraplow ................. 2.50 83

Table 2. Effect of Cover Crop and fertilizer NRate on Corn Grain Yield, 1988-90 Average

Yield/acre, by N rateCover

0 50 100 150lb. lb. lb.

Bu. Bu. Bu. Bu.Clover .......... 87 95 111 110Fallow .......... 42 71 88 101Rye ........... 23 47 76 96Lupin ........... 83 108 109 114

These results suggest that para-plowing prior to planting the covercrop increased water infiltrationand N leaching.

Yields peaked with 50 to 100pounds N per acre following cloverand lupin and with 150 pounds Nfollowing rye and fallow, table 2.White lupin compared favorably toclover in N production and result-ant benefit to a corn crop. Lupinwinter killed in areas that werepoorly drained, but otherwiseshowed potential as an alternativewinter crop for grain.

D.W. Reeves and J.T. Touchton

Broiler Litter and Tillage Systems for Corn

A study at the Wiregrass Substa-tion, Headland, in 1990 investigatedutilization of N from broiler lit-ter by corn under strip and con-ventional tillage systems.

The strip tillage system employeda planter with a leading parabolicsubsoiler matched to the planterrow width (36 inches) so that tillageonly occurred in a narrow band cen-tered on the seed row. Conventionaltillage consisted of chisel plowingone day prior to planting and twodiskingson the day corn was planted.

Broiler litter rates included 2, 4,and 8 tons per acre, (67, 133, and 267

pounds N per acre). Forcomparison, matchingrates of N as ammoniumnitrate were applied. TheN sources were broadcastbefore planting and wereincorporated with thesecond disking in con-ventional tillage. For striptillage, only that portionof broiler litter or am-monium nitrate withinthe tilled zone was incor-porated.

Strip tillage resulted inhigher grain yields across

all N sources and N rates, see table.A 2- to 4-inch-thick hardpan exists atthe study location at a depth of ap-proximately 10 to 15 inches belowthe soil surface. Since 1990 was adrought year at Headland, dis-ruption of the hardpan via para-bolic subsoiling in strip tillageapparently increased corn rootingand water availability. It was ex-pected that N from broiler litterwould be less effective in increasinggrain yields under strip tillage thanunder conventional tillage manage-ment because of N volatilizationlosses from broiler litter remainingon the soil surface. This was notthe case in 1990, a drought year,when water availability appeared tobe much more important than Navailability.

The ammonium nitrate sourceproduced greater corn grain yieldsthan broiler litter, and the optimumN source/N rate combination wasammonium nitrate at 133 poundsnitrogen per acre. Eight tons ofbroiler litter per acre (267 poundsnitrogen) were required to ap-proach the yield obtained with133 pounds nitrogen from am-monium nitrate.

Leaching of broiler litter N belowthe root zone during the 1990 grow-ing season was not likely because:(1) water demand by corn exceededrainfall throughout the growingseason, and (2) N from ammonium

continued on page 3

Corn Grain Yields and Excess N as Affected by N Sourceand Tillage System, 1990

Grain yield/acre Excess N/acre'N sourceand rate2 ST3 CT Av. ST CT Av.

Bu. Bu. Bu. Lb. Lb. Lb.

No N ...................... 25 14 20 0 0 0

Broiler litter67 Ib. ......................... 66 48 57 39 47 43133 lb. ....................... 65 39 52 110 118 114267 b. ....................... 104 78 91 215 228 222

Ammonium nitrate67 lb ......................... 84 43 64 31 47 391331b. ....................... 125 83 104 76 88 822671b. .................... 113 78 96 206 222 214

Average.................. 106 62 84 104 119 112

Excess N = N not found in corn grain.2 Broiler litter contained 33.5 pounds N/ton.3 ST = strip till, CT = conventional till.

Broiler Litter, continued

nitrate was more subject to leachingthan that from broiler litter becausemost broiler litter N was in the or-ganic form.

Excess N (that not taken up by thecrop) can lead to groundwater con-tamination with nitrate. Because ofless available water and loweryields, use of conventional tillageresulted in more excess N than striptillage. The 133-pound N rate thatgave best corn grain productionhad relatively low amounts ofexcess N. The broiler litter rate re-quired to produce nearly compa-rable grain yields (8 tons) left siz-able quantities of N in the environ-mental system. Some of this N isnitrate or will be converted to nitrateand may be leached out of the root-ing zone with winter rains. Thus,the potential for groundwater con-tamination with N exists when highrates of broiler litter are land ap-plied. Winter cover crops such ascereal rye could be used to capturesome of this excess N.

Based on one year's data, it ap-pears that strip tillage is superiorto conventional tillage with re-spect to grain yield and N utili-zation in the Wiregrass regionregardless of N source or N rate.It also appears that broiler litteris a less efficient source of N forcorn than ammonium nitrate.

C.W. Wood, C.D. Cotton,and J.H. Edwards

Tropical Corn Disappointing In 1989-90 Tests

AAES research in 1989-90evaluated tropical corn (Pioneer304C) production systems andmeasured the crop's response torates of fertilizer nitrogen, re-sidual levels of soil phosphorusand potassium, and soil pH. The1989 tests were an intensive smallgrain-corn-soybean rotation atsix locations. In 1990 the studywas expanded to add a continu-ous small grain-tropical corndouble-cropping system at sevenlocations. Plantings were madein mid- to late June followingsmall grain harvest.

Tropical Corn Yields1 Following a Small Grain

Yield per acre

Location Tropical Smallcorn,grain grain'1989

Bu. Bu.Brewton ...................... 0 59Monroeville ............. . 0 64W iregrass .................... 36 32Prattville .................... 42 70Upper Coastal Plain..... 52 29Sand Mountain ......... 65 46

(172 tonssilage)

Tennessee Valley ........ 35 59

'Yields are an average of plots at seven locationsa standard application of N-P-K fertilizer and no

2 Triticale at Brewton and Monroeville; wheatlocations.

3All silage yields adjusted to 65 percent moistu

Corn grain yields were disap-pointing in both 1989 and 1990because of mid-summer insectdamage (armyworms and cornearworms) and late summer-early fall drought. Surprisingly,yields were higher in north Ala-bama than south Alabama wheretropical varieties are expected tobe better adapted. Worms de-stroyed the total crop both yearsat Brewton and Monroeville Ex-periment Fields despite repeatedattempts to control the pests.

Grain harvests in north Ala-bama were late (November/De-

cember) in 1989 and

Crop grain moisture was high(approximately 30 per-cent). In 1990, the crop

rropical was harvested only forcorn, silage because of a poorsilage3 grain crop.1990 Tropical corn ap-Tons pears to respond to ni-0 trogen rates and residual0 soil nutrients (P, K, and0 Mg) similar to temper-

11.1 ate varieties which were10.0planted on some of these

plots in 1968-81.9.5

receiving C.C. Mitchell and P.L. Maskirrigaton.at other

re.

Fungicides Increase Wheat Yields at Some Locations

Results from experiments con-ducted during 1989-90 again showedthat diseases can have a significantimpact on wheat yields in some ar-eas of Alabama. Various rates ofseveral labeled and experimentalfungicides were sprayed onto plotsof McNair 1003 wheat at three sub-stations. Fungicides included wereASC 66811 100E, Bayleton 50W,

Dithane M-45, DPX H6573, Folicur3.6F, RH-7592 2F, Spotless 25W, andTilt 3.6E. Initial applications of eachwere made around the time of flagleaf emergence; if needed, a secondapplication was made when the grainheads were beginning to emerge.

At the Gulf Coast Substation, allfungicides tested gave good to ex-cellent control of Septoria glume

blotch and leaf rust, and increasedyield. Yields from plots sprayedwith fungicides averaged 46 to 65bushels per acre, as compared to 34bushels from the unsprayed plots.Only leaf rust occurred in the testsat the Wiregrass Substation, and thenat relatively low levels. All fungi-cides reduced the disease, but yield

continued on page 4

I

Fungicides, continued

responses were not as marked as atthe Gulf Coast Substation. Yieldsfrom fungicide-trea ted plots rangedfrom 40 to 61 bushels per acre; thosefrom unsprayed plots averaged 45bushels. At the Sand Mountain Sub-

station, most of the fungicides testedreduced the levels of Septoria leafblotch, the only disease that devel-oped in this test, but there were nosignificant yield increases from anyfungicide treatment.

R.T. Gudauskas and D.J. Collins

Hand-held Meter Predicts Corn N Needs

Methods of predicting nitrogen(N) needs by corn have not beenreliable for Southeastern condi-tions. Soil tests have shown littlesuccess. Corn leaf tissue tests for Nhave shown promise, but time in-volved with sampling and labora-tory analyses may prevent timelyproducer response to corn N needs.

Measuring corn leaf tissue chlo-rophyll, which is directly related tocorn leaf tissue N, may be anequivalentmeansof determin- Ging the need for supplemental p,fertilization. In a field study in 11990attheE. V. SmithResearchCenter, use of a newly devel-oped chlorophyll meter to pre- 1dict supplemental N needs incorn showed promise. Themeter is lightweight (less than1/2 pound), is powered by bat-teries, provides instantaneousreadings (SPAD units), and canstore up to 30 readings.

Irrigated corn (Dekalb 689)was grown at the site and wasfertilized with broadcast-appliedammonium nitrate at rates of 0, 50,100, 150, 200,250, and 300 pounds Nper acre to establish a range of grainyield and chlorophyll tissue levels.Chlorophyll was measured at the10-leaf stage (V10)because this stageof growth would allow supplemen-tal N applications to the corn crop.

Corn grain yields increased withincreasing rates of N fertilizer, withpeak yields at approximately 150 to200 pounds nitrogen.

Chlorophyll measurementsatV10

did an excellent job of predictingcorn grain yields, as illustrated bythe graph. Chlorophyll measure-ments for the N rate range that pro-duced top yields (150 to 200 poundsN) were between 55.5 and 56.7SPADunits. This suggests that supple-mental N may be needed if chloro-phyll readings are below 55.5 SPADunits at the V10 stage of growth.

C.W. Wood and D.W. Reeves

O0 I I I I40 45 50 55 60

V10 chlorophyll, SPAD units

Boron Fertilizer NotNecessary for IrrigatedCorn

Coastal Plain soils of Alabama

are low in ex tractable boron and it isoften assumed that irrigated cornneeds boron applications for maxi-mum yields. However, this was not

continued on page 5

Disease ProblemsReduced in 1990Corn and SmallGrains

Incidence and severity of diseasesin grain crops were low in 1990 (insome cases lower than in 1989). De-tailed results have been reported inthe Corn Variety Report and SmallGrain Variety Report, which wereissued by the AAES in late 1990.

Corn. Levels of the virus diseasesmaize chlorotic dwarf (MCD) andmaize dwarf mosaic (MDM) wereunusually low in regular corn vari-ety tests and in the general cropstatewide. Low incidence of bothprecluded meaningful comparisonsof hybrid performances at the BlackBelt Substation, Marion Junction, andthe Prattville Experiment Field. Intests of 49 hybrids at the TennesseeValley Substation, Belle Mina, andthe Upper Coastal Plain Substation,Winfield, incidence of MCD rangedfrom 0 to 10.5 percent, and aver-aged 0.9 percent; MDM levelsranged from 0 to 11.6 percent, andaveraged 0.5 percent. Several hy-brids at both locations showed nosymptoms of either disease.

Small Grains. Most of the com-mon diseases occurred in the small

grain variety tests planted at 12 sub-stations and experiment fieldsthroughout the State. However, theincidence and severity were gener-ally lower than in 1989. Leaf rust waslight to severe and Septoria blotchwas moderate to severe on wheatentries at most locations. Outbreaksof powdery mildew occurred intests at the Sand Mountain Substa-tion, Crossville, and the WiregrassSubstation, Headland; otherwise, itsincidence was generally light. Withfew exceptions, only trace levels ofbarley yellow dwarf were noted in

continued on page 5

rain yielder acre, bu.50 r-

00

501

Boron Fertililzer, continued

true in an AAES field test at the E.V. Smith Research Center onGoldsboro soil.

Boron treatments of 0, 2, and 4pounds per acre were applied as foursplit applications each year. Nitro-gen and sulfur fertilizers were ap-plied at the same times. All phos-phorus, potassium, and zinc fertiliz-ers and lime were incorporated be-fore planting each year. Irrigationtreatments were: (1) no irrigation,(2) drip irrigation with controltensiometers at a depth of 6 inches,and (3) drip irrigation with controltensiometers at a depth of 13 inches.

Three-year average yields for thetreatments were:

No irrigationNo boron ................... 100 bu.2 lb. boron ..................... 107 bu.4 lb. boron ..................... 106 bu.Drip irrigation, 13-in. controlNo boron ................... 205 bu.2 lb. boron ..................... 206 bu.4 lb. boron .................... 187 bu.Drip irrigation, 6-in. controlNo boron ................... 214 bu.2 lb. boron .................. 207 bu.4 lb. boron ..................... 212 bu.Although boron applications did

not increase grain yields, they didincrease the earleaf boron concen-tration at silking from 14 to 26 partsper million. Thus, boron from thefertilizer was available to the crop.

J. W. Odom

Disease Problems, continued

wheat. Incidence of loose smut waslow everywhere, and stem rust wasnot seen in any test in 1990. On oats,crown rust was moderate to severeon most entries at the Gulf CoastSubstation, Fairhope, and theWiregrass Substation, as was leafspotat the Piedmont Substation, CampHill, and barley yellow dwarf at theTennessee Valley Substation.Septoria blotch was prevalent ontriticale entries at all locations.

R.T. Gudauskas

Annual Ryegrass Controlled in Wheat withPostemergence Hoelon Application

Annual ryegrass is a common andpernicious weed species that is aproblem in wheat production. Fortyannual ryegrass plants per squareyard have been shown to causewheat yield reductions of 19-26percent. Reduced grain quality isalso caused by ryegrass seeds.

Ryegrass control experimentswere conducted in 1988-89 atPrattville and Tallassee and atPrattville, Tallassee, and MarionJunction in 1989-90. Two rates andfour application timings ofHoelon@ herbicide were compared.Hoelon was applied at 0.5 and 1.0pound ai (active) per acre preemer-gence and postemergence to ryegrasswith 2, 4, and 8 leaves. A non-ionicsurfactant was included in allpostemergence applications. Allapplications were made in a volumeof 15 gallons per acre.

Prattville. Annual ryegrass seedswere sown broadcast at 20 poundsper acre and Saluda wheat seed werethen planted at 70 pounds per acre in7-inch rows on 9/22/88 and 10/22/89. Hoelon was applied preemer-gence on 9/23/88 and 10/22/89.Application dates for the post-emer-gence treatments were: 10/13/88,10/26/88, 11/11/88, 12/4/89, 1/3/90, and 2/6/90, which correspondedto ryegrass growth stages of 2, 4,and 8 leaves for the respective years.

Two-year average ryegrass con-trol at harvest was good to excellent(80 to 98 percent) with all Hoelonapplications. Slightly less controlwas evident when Hoelon was ap-plied at 0.5 pound ai per acre atthe 4-leaf stage (85 percent) andboth rates at the 8-leaf stage (80to 82 percent), but this did nottranslate into lower wheat yields.

Wheat yield with all Hoelontreatments ranged from 58 to 70

bushels per acre. Yield averaged 68and 58 bushels, respectively, for thehand-weeded and non-weededtreatment. Test weight for allHoelon treatments ranged from 56to 57 pounds per bushel, comparedto 56 pounds for the non-treated and57 pounds for the hand-weededtreatment.

Tallassee. Planting was identicalto that at Prattville except wheat andryegrass seeds were planted 10/28/88 and 10/25/89. Preemergencetreatments were applied 11/1/88and 10/25/89. Postemergencetreatments were applied 11/22/88,12/8/88, 1/12/89, 11/24/89,1/22/90, and 2/26/90, which corre-sponded to ryegrass growth stagesof 2, 4, and 8 leaves for the re-spective years.

Two-year average ryegrass con-trol at harvest was 86 to 98 percentfor all Hoelon treatments, except the0.5-pound rate applied to ryegrassat the 8-leaf stage averaged 76 per-cent control. Wheat yield for Hoelontreatments ranged from 50 to 62bushels per acre. Test weight was50-51 pounds per bushel for allHoelon treatments, and 49 and 50pounds, respectively, for the non-treated control and for the hand-weeded treatment.

Marion Junction. This locationwas not included in 1988. Plantingwas identical to the above exceptwheat and ryegrass seeds wereplanted 10/30/89. Preemergencetreatments were applied 10/30/89.Postemergence treatments wereapplied 12/5/89, 2/28/90, and3/13/90, which corresponded tothe three growth stages.

Ryegrass control at harvest wasgood to excellent (83 to 95 percent)for all Hoelon treatments, except forboth rates applied to ryegrasswith 8 leaves. The 0.5-pound rate

continued on page 6

Annual Ryegrass, continued

provided only 63 percent control,while the 1.0-pound rate aver-aged 75 percent. There was atrend for wheat yield to be higherfor Hoelon applied at either rateto ryegrass with 2 leaves and the0.5-pound rate applied at the 4-leafstage. Also, the 1.0-pound rate ap-plied preemergence produced goodryegrass control and high wheatyield.

Hoelon offers the grower a goodchemical tool for control of annualryegrass in wheat. Postemergenceapplication at 0.5 pound ai per acreto ryegrass with 2 to 4 leaves ap-pears to be the optimum rate andtime of application. On heavy claysoils, preemergence application ofHoelon at 1.0 pound ai per acre maybe advantageous if problems withpostemergence applications arelikely due to wet soils.

R.H. Walker, D.R. Wyatt,and J.S. Richburg III

CONTRIBUTORS To

GRAIN CROPs RESEARCH

PROGRAM, 1990

Wheat and Feed Grains ProducersE.I. DuPont de Nemours and Co.Fermenta ASC CorporationGustafson, Inc.Mobay CorporationRohm and Haas, Inc.

EDITOR'S NOTI:Mention of company or trade names does not

indicate endorsement by the Alabama Agricul-

tural Experiment Station or Auburn University

of one brand over another. Any mention of non-

label uses or applications in excess of labeled rates

of pesticides or other chemicals does not constitute

a recommendation. Such use in research is simply

part of the scientific investigation necessary to

fully evaluate materials and treatments.

Information contained herein is available to all

persons without regard to race, color, sex, or

national origin.

February 1991 9M

Composted Broiler Litter Good as Corn Fertilizer

Broiler litter has long been rec-ognized as a good source of ni-trogen (N) for corn production.However, it is known that too muchlitter can reduce yields of cornand lead to a loss of N that couldotherwise be used for plantgrowth. Much of the N presentin fresh litter is readily availablefor plant use or lost to the atmo-sphere as a gas. Composting litterconverts N to forms that are notas readily lost to the environment.

Tests at the Sand Mountain Sub-station, Crossville, compared corn

yield response to ammonium ni-trate, fresh broiler litter, andcomposted litter at several rates.Despite a dry, hot growing season,corn responded equally well to allthree sources of N. Grain yielddata indicate that ratesof fertilizerexceeding 80 pounds of N per acrehad no benefit. This correspondedto 2,080 dry pounds of fresh litter,3,600 dry pounds of compost, and235 pounds of ammonium nitrateper acre applied at planting.

R.P. Flynn and C.W. Wood

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