-N Surface Applications of Potassium Best for Cotton When growing cotton on a soil with "low" subsoil potassium (K), what rate of K fertilizer should be used and how should it be applied? These questions were addressed through an Alabama Agricultural Experiment Station field study at the Tennessee Valley Substation, Belle Mina. Often in Alabama, cotton with K deficiency has been found to have ad- equate surface soil K, but subsoil K levels are "low." A recent survey of cotton fields across Alabama found that 29 percent of the subsoils tested "low" or "very low" in K, while only 19 percent of the subsoils tested "high." The research site rated "medium" in surface K, but "low" in subsoil K, according to Soil Testing Laboratory results. Potassium fertilizer, at rates shown in the table, was either broad- cast in the spring or split-ap- A plied with fall and spring appli- cations. The fall application was F turned under with a moldboard plow. Cotton was grown in the test area in 1989 and 1991 and exhibited severe K deficiency symptoms during both years. 1 Surface application of K rates in the spring produced yields similar to cotton treated with K split-applied in the spring and fall. Using higher rates of K fertilizer than normally recom- mended (60 pounds K 2 0) for a soil rated "medium" in K did result in some yield response. However, cotton yield response to K fertilizer indicates little benefit from the deep turning under of K fertilizer rates in the fall. This research would indicate that, for cotton grown on soils testing "low" EFFECTS OF RATES AND TIMING OF POTASSIUM FERTILIZER ON OTTON YIELDS, TENNESSEE VALLEY SUBSTATION, BELLE MINA nnual K 2 0 rates, yield/acre Seed cotton, yield/acre all Spring 1989 1991 Avg. 0 0 1,777 1,538 1,658 0 60 2,649 1,807 2,228 0 120 2,814 1,794 2,304 0 180 2,942 1,924 2,433 60 60 2,860 1,872 2,366 90 90 2,840 1,800 2,320 20 0 2,740 1,598 2,169 in subsoil K, increasing K 2 0 applica- tions 30 to 60 pounds per acre above surface soil recommendations may be necessary. Applying this rate of K fertilizer to the soil surface before plant- ing seems the best method to correct a K deficiency in research plots. How- ever, these rates may have to be applied for several years before subsoil K levels are increased. C.H. Burmester and G.L. Mullins Microbial Insecticides Compare Favorably to Conventional Insect Control in Cotton Research in the United States and in other countries, such as Australia, has shown that various microbial prod- ucts, primarily based on the bacterium Bacillus thuringi'ensis (B.t.), can result in yields similar to that of conventional insecticides, such as Karate®, against cotton bollworm and tobacco bud- worm. Additionally, B.t. products should reduce the rate of increase of insecticide resistance to conventional insecticides because of their novel mode of action and their low toxicity towards beneficial insects. Alabama Agricultural Experiment Station field studies were initiated in 1991 to see if similar results could be obtained in Alabama and to determine which microbial products were the most similar to that of conventional insecticides. Cotton (Deltapine 90) was planted May 23, 1991, at the Wiregrass Substa- continued on page 2 A IC AUBURN UNIVERSIT LOWEL T.F~ossm, IRCO AuUR UNVRIY ALBM RESEARCH UPDATE 1992 COTTON
Transcript
-N
Surface Applications of PotassiumBest for Cotton
When growing cotton on a soilwith "low" subsoil potassium (K),what rate of K fertilizer should beused and how should it be applied?These questions were addressedthrough an Alabama AgriculturalExperiment Station field study at theTennessee Valley Substation, BelleMina.
Often in Alabama, cotton with Kdeficiency has been found to have ad-equate surface soil K, but subsoil Klevels are "low." A recent survey ofcotton fields across Alabama foundthat 29 percent of the subsoils tested"low" or "very low" in K, while only 19percent of the subsoils tested "high."
The research site rated "medium"in surface K, but "low" in subsoil K,according to Soil Testing Laboratoryresults. Potassium fertilizer, at ratesshown in the table, was either broad-
cast in the spring or split-ap- Aplied with fall and spring appli-cations. The fall application was Fturned under with a moldboardplow.
Cotton was grown in thetest area in 1989 and 1991 andexhibited severe K deficiencysymptoms during both years. 1Surface application of K rates inthe spring produced yields similar tocotton treated with K split-applied inthe spring and fall. Using higher ratesof K fertilizer than normally recom-mended (60 pounds K2 0) for a soilrated "medium" in K did result in someyield response. However, cotton yieldresponse to K fertilizer indicates littlebenefit from the deep turning under ofK fertilizer rates in the fall.
This research would indicate that,for cotton grown on soils testing "low"
EFFECTS OF RATES AND TIMING OF POTASSIUM FERTILIZER ON
OTTON YIELDS, TENNESSEE VALLEY SUBSTATION, BELLE MINA
in subsoil K, increasing K2 0 applica-tions 30 to 60 pounds per acre abovesurface soil recommendations may benecessary. Applying this rate of Kfertilizer to the soil surface before plant-ing seems the best method to correct aK deficiency in research plots. How-ever, these rates may have to be appliedfor several years before subsoil K levelsare increased.
C.H. Burmester and G.L. Mullins
Microbial Insecticides Compare Favorably to ConventionalInsect Control in Cotton
Research in the United States andin other countries, such as Australia,has shown that various microbial prod-ucts, primarily based on the bacteriumBacillus thuringi'ensis (B.t.), can result inyields similar to that of conventionalinsecticides, such as Karate®, againstcotton bollworm and tobacco bud-
worm. Additionally, B.t. productsshould reduce the rate of increase ofinsecticide resistance to conventionalinsecticides because of their novelmode of action and their low toxicitytowards beneficial insects.
Alabama Agricultural ExperimentStation field studies were initiated in
1991 to see if similar results could beobtained in Alabama and to determinewhich microbial products were themost similar to that of conventionalinsecticides.
Cotton (Deltapine 90) was plantedMay 23, 1991, at the Wiregrass Substa-continued on page 2
A IC AUBURN UNIVERSIT
LOWEL T.F~ossm, IRCO AuUR UNVRIY ALBM
RESEARCH UPDATE
1992
COTTON
Reducing Cotton Production InputsSignificant tillage and chemical in-
puts are currently used to producecotton in Alabama's Tennessee Valleyregion. Reducing these inputs withoutaffecting yield would provide substan-tial savings to growers.
An Alabama Agricultural Ex-periment Station study was initi-ated in 1991 at the Tennessee ValleySubstation, Belle Mina, to investigatethe potential for reducing cotton pro-duction costs. The test area wasdivided into no-till and conventionaltill strips. Prowl 4E@ at 1 pint peracre was incorporated on all con-ventional tillage plots, and Prowl at 2pints per acre plus Roundup@ at 2pints per acre was sprayed on no-till plots prior to planting. Soil fungi-cide treatments consisted of in-fur-row (TSX6) or hopperbox (Apron@).Soil insecticide treatments consistedof Temik 15G9 at 3 or 5 pounds peracre. Preemergence herbicide treat-ments consisted of Cotoran 4Lbroadcast at 2 or 4 pints per acre.
All possible combinations ofchemical inputs were used in each
tillage system. Conventional tillageplots were cultivated and directsprayed with Cotoran plus MSMA.Control treatments (no fungicide,Temik, or Cotoran applied) wereincluded for each tillage system.
REDUCED COTTON PRODUCTION INPUTS TRIALS, 1991,TENNESSEE VALLEY SUBSTATION, BELLE MINA
Tillagetype
Stand count Seed cottonno./6 ft. row yield
Lb./A
No-tillIn-furrow ...............Hopper box ..........Temik, 3 lb. ...........Temik, 5 lb ...........Cotoran, 2 pt. .......Cotoran, 4 pt. .......Average ..............
Cotton stand counts were equal forboth tillage systems and were not af-fected by soil fungicide treatments, seetable. Seed cotton yield was slightlyhigher for conventional than no-tillsystems when averaged over chemicalinputs. Temik at the higher labeledrate provided numerically higheryields in both tillage systems. Annualmorningglory control was equal forboth the low and high Cotoran rates inboth tillage systems, averaging 94percent overall. Prickly sida controlwas lower in conventional (81 percent)than in no-till (92 percent) for the lowCotoran rate.
Yields were not affected byCotoran rate in either tillage system.Seed cotton yield was higher for theno-till control than for the conventionaltillage control, primarily due to weedgermination suppression in the non-tilled soil. First-year results indicatesome production inputs might be re-duced without adversely affectingyield.
M.G. Patterson. B.E. Norris, and B.L. Freeman
Microbial Insecticides, continued
tion, Headland. Each treatment plotwas eight rows wide by 75 feet longand was replicated four times. In addi-tion to an untreated control, the follow-ing insecticides were tested: pyre-throid (Karate); ovicide(Larvin®andOvasyn); B.t. (Dipel®, Javelin@, EXP60516A, Bactec I, and Bactec IIl);Thuringiensin (Di-Beta); virus(Elcar@); gut poison (potassium car-bonate); and a feeding stimulant(strawberry gelatin). Foliar treatments,including Prime Oil as a spreader/sticker, were applied seven times (July3, 9, 22, and 30 and Aug. 6, 9, and 16)followed by one blanket coveragespray of Karate on Aug. 22 to preservedamage levels obtained from the mi-crobial treatments.
Treatments were initiated when atleast five bollworm/budworm eggswere found per 25 terminals. Yieldswere taken by mech-anically harvest-
ing the middle two rows perplot on November 6.
There were significant dif-ferences among cotton yields,with Karate-treated plotsyielding notably more than theuntreated control or the EXP60516A, Di-Beta, and Bactec IIIplus gelatin treatments. There-fore, all treatments with a cottonyield greater than 30 pounds perplot were not significantly dif-ferent from Karate, see table.Also, the addition of an ovicidealways resulted in at least aslight increase in control.
The summer of 1991 was arelatively light year for boll-worm/budworm infestations insouth Alabama. Continued re-search in upcoming summers willneeded to determine if microbprod ucts can be as effective as conv
MICROBIAL CONTROL OF BOLLWORM/BUDWORM ON COTTON INHEADLAND, ALABAMA, 1991
potassium carbonate, 150 g ....................Bactec I, .75 lb ............... .. ...............Untreated control .......................................Di-Beta, 10 g a.i ........................Bactec III, .75 lb., + strawberrygelatin ..............................................
Yield ,3
37.0535.5335.1534.3533.2032.3031.9031.6031.55
31.1030.9028.2527.55
25.00
1 Treatment rates per acre.2 Mean of four replicates (25 plants sampled/
replicate) season long (six sampling dates).3 Yield in pounds seed cotton/plot.
tional controls when bollworm/bud-be worm pressure is greater.ial W.J. Moar and R.H. Smith
Cotton Responds to Foliar Feeding of Potassium NitrateThe occurrence of late season po-
tassium (K) deficiency in cotton is be-coming more and more common in theSoutheast. Visual symptoms of K defi-ciency develop late in the season due tothe high demand for K during boll de-velopment. Preliminary work in Ar-kansas has indicated possible yieldand quality increases by foliar applica-tions of potassium nitrate (KNO 3 ) tocotton.
In 1991, an Alabama AgriculturalExperiment Station field test at theTennessee Valley Substation, BelleMina, and an on-farm test at SamSpruell's farm in Lawrence Countywere established to evaluate foliarfeeding of KNO 3 in Alabama. The soilat the Tennessee Valley Substation wasrated "high" in K, while the farm sitetested "low" in K. At both sites KNO 3(10 pounds KNO 3 per 10 gallons ofwater per acre) was applied at 10- to
14-day intervals beginning 2 REweeks after first white bloom.The Substation cotton received Potafour applications of KNO 3 ,while the on-farm cotton re-ceived three applications.
Severe late season K defi-ciency symptoms were noted inthe on-farm field, while onlyslight K deficiency symptomswere noted in the Substationfield. The on-farm cotton com-pletely defoliated when the cottonwas only 30 percent open due to the Kdeficiency.
Cotton at the Substation site wasirrigated and yields were excellent, seetable. A positive yield response to bothsoil and foliar applied K was observedat this site, even though the soil had a"high" soil test rating for K. The on-farm site also produced good yields,but no yield response to either the soil
SPONSE OF COTTON TO SOIL AND FOLIAR APPLIED POTASSIUM
ssium treatments/acre Seed-cotton yield/acre
Soil Foliar TVS On-farm
Lb. Lb. Lb. Lb.
0 None 2,648 3,0020 KNO 3 3,034 2,733
30 None 2,896 -30 KNO 3 3,01160 None 3,034 -
60 KNO 3 3,126 2,761
or foliar applied K was observed.Initial first-year results appear to
be conflicting. However, these resultssuggest that cotton yields can be in-creased by foliar applications ofKNO 3 under conditions of slight Kdeficiency and high yields. In contrast,when cotton K deficiency was severe,foliar K was not sufficient to correct thedeficiency.
G.L. Mullins and C.H. Burmester
Effects of Planting Date, Row Spacing, Variety, and PlantGrowth Regulator on Cotton
Results of Alabama AgriculturalExperiment Station research from 1988through 1990 at the Gulf Coast Substa-tion, Fairhope, indicated an April plant-ing date for Deltapine (DPL) 90 cottonon a solid-36-inch rowproduced greateryields than May or June dates in 2 of 3years. New research was initiated atFairhope in 1991 to study the interactionbetween row spacing, planting date,cotton variety, and PIX® plant growthregulator.
Cotton was planted April 15 andMay 15. DPL 20, a short sea-son variety, was compared to PLANTINDPL 90, a long season variety,on both planting dates. A Plantisolid 36-inch pattern wascompared to a skip patternwhere pairs of rows 36 inches April 15apart were separated by 60-inch skips. Lastly, PIX waseither applied or not applied.All possible combinations of May 15planting date, row spacing,variety, and PIX treatmentswere represented.
Seed cotton yields were
approximately 900 pounds per acregreater for the May planting date whenaveraged over row spacing and variety,see table. Within planting dates, thesolid 36-inch pattern produced slightlyhigher yields than the skip pattern.Except for DPL 20 planted on May 15,neither variety demonstrated a clearyield advantage over the other.
PIX did not significantly affectyield in any case; however, cottonheight was reduced 8 to 12 inches inPIX treated plots. More bolls per plant
NG DATE, Row SPACING, VARIETY, AND GROWTH REGULATOR
were counted for the April plantingdate (average 26) compared to the Mayplanting (average 21). Rotten bolls perplant were numerically higher for theApril planting (average 6) than the Mayplanting (average 4). No differences inthe number of rotten bolls were foundamong row patterns within each plant-ing date.
M.G. Patterson, M.D. Pegues, and K.L. Edmisten
Chlorophyll MeterHas Potential forDetermining CottonN Status
Cotton producers, consultants, andresearchers have long sought for aquick, reliable method to determinecotton nitrogen (N) needs. Improper Napplication can affect production andthe environment.
Petiole nitrate tests are used in sev-continued on page 4
Chlorophyll Meter, continued
eral southern states to monitor cotton N
status, but research has not confirmedthe reliability of these tests in Ala-
bama. Leaf-blade total N analysis has
been useful in predicting cotton N re-quirements, and is less affected by cli-
mate and seasonal changes than petiolenitrate.
Because leaf N status is directlyrelated to leaf chlorophyll content, a
newly developed hand-held chloro-phyll meter could offer a substitute forleaf-blade total N analysis. Chlorophyllmeter readings are measured in soil
plant analysis development (SPAD)units and are instantaneous. If chloro-
phyll meters could predict cotton Nneeds, farmers could realize substantialsavings of money, labor, and time asso-ciated with leaf-tissue collection and
analysis.Research was conducted in 1991
to determine the feasibility of using
chlorophyll meter readings for deter-
mining cotton N status. The experi-ment was conducted at the E.V. SmithResearch Center, Shorter. Several N
rates were used to establish a range ofcotton (Deltapine 50) yield, tissue Nconcentration, and chlorophyll con-centration. Chlorophyll meter read-ings were taken at first square, first
bloom, and mid-bloom on the upper-most fully developed leaves. For com-
parison, leaf-blade and petiole sampleswere collected and analyzed for total N
and nitrate, respectively.Abundant, well distributed rainfall
during the 1991 growing season pro-
moted high seed cotton yields and re-sponse to N fertilizer. Seed cottonyields ranged from about 1,000 poundsper acre with no N fertilizer to 3,500
EDITOR S NOTE
Menitioni of compaliiy or trade naitis. does not
indicate cteorscimcnit b y the Alabama Agricul
ftural Experiimcit Station or Auburii Lhliversity of
one branl over ianother Aiiny menition of inoimabeuses or applications in excess of labetled rates ofpesticide o crothcr chmical;l doiios ot constitute ar'coplptdalttioi1. Sucli iuse iil risetarchl is simply
part of the scientific ivlstigation nicessary to fiully
tvalliittt' llatrials la d tr atieits.
Info rmationi contained hereini is available' to aill
pcrsoils wtithlout regard to race, color , sx, or lilatiorlill
ortiii.
4,000
- 3,000 <36
A A
A A
A34 A 2,000 :A A
32 A A A
A 1,000
30 I I I I I I3 4 5 6 32 34 36 38 40
Leaf N, % SPAD Reading
Relationship between (A) chlorophyll meter readings (SPAD) and cotton leaf-blade N at firstsquare, and (B) between seed cotton yield and chlorophyll meter readings at first square.
pounds per acre with 160 pounds N peracre.
Chlorophyll meter readings onleaves at first square were highly re-lated to leaf-blade total N, see figure A.Relationships between leaf-blade totalN and chlorophyll meter readings atfirst square also were highly related tocotton yield, figure B. Similar relation-ships were found at first bloom andmid-bloom.
These relationships suggest thatcotton N requirements could be pre-dicted with the chlorophyll meter. In
addition, the chlorophyll meter pre-dicted seed cotton yields as well as orbetter than leaf-blade N and petiole ni-trate analyses at all three stages ofgrowth. Especially promising is theconnection between chlorophyll meterreadings at first square and seed cottonyield, because supplemental N fertilizercould easily be applied at that stage ofgrowth.
Further calibration of the meter isneeded before this technology can beuseful to producers.
C.W. Wood. D.W. Reeves, and K.L. Edmisten
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