Research Article Assessing the Economic Impact of Inversion...

Research ArticleAssessing the Economic Impact of Inversion TillageCover Crops and Herbicide Regimes in Palmer Amaranth(Amaranthus palmeri) Infested Cotton

Leah M Duzy1 Andrew J Price1 Kipling S Balkcom1 and Jatinder S Aulakh2

1National Soil Dynamics Laboratory Agricultural Research Service United States Department of Agriculture411 South Donahue Drive Auburn AL 36852 USA2The Connecticut Agricultural Experiment Station Valley Laboratory 153 Cook Hill Road PO Box 248 Windsor CT 06095 USA

Correspondence should be addressed to Leah M Duzy leahduzyarsusdagov

Received 26 July 2016 Revised 7 October 2016 Accepted 2 November 2016

Academic Editor Patrick J Tranel

Copyright copy 2016 Leah M Duzy et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Cotton (Gossypium hirsutum L) producers in Alabama are faced with a rapidly expanding problem that decreases yields andincreases production costs herbicide-resistant weeds Producers increasingly rely on integrated weed management strategiesthat raise production costs This analysis evaluated how tillage cover crops and herbicide regime affected net returns abovevariable treatment costs (net returns) for cotton production in Alabama from 2009 to 2011 under pressure from Palmer amaranth(Amaranthus palmeri S Wats) Annual net returns were compared for two tillage treatments (inversion and noninversion tillage)three cover crops (crimson clover [Trifolium incarnatum L] cereal rye [Secale cereal L] and winter fallow) and three herbicideregimes (PRE POST and PRE+POST) Results indicate that under heavy Palmer amaranth population densities one year ofinversion tillage followed by two years of noninversion tillage along with a POST or PRE+POST herbicide application hadthe highest net returns in the first year however the economic benefit of inversion tillage across all herbicide treatments wasnonexistent in 2010 and 2011 Cotton producers with Palmer amaranth infestations would likely benefit from cultural controls inconjunction with herbicide applications as part of their weed management system to increase net returns

1 Introduction

In the southern United States (US) producers spent over 37billionUS$on crop production expenses in 2015 Agriculturalchemicals and seed comprised over 4 billion US$ or 11 oftotal crop production expenses In Alabama total operatingexpenses for farms classified as cotton farms (North Amer-ican Industry Classification System [NAICS] 11192) equaled1276 million US$ as of the 2012 Census of Agriculture Ofthat producers spent 2229 million US$ (175) on pesticidesand other chemicals and 1975 million US$ (155) on seed[1] which included expenses such as costs of seed seedtreatments and seed cleaning costs [2] While many per unitproduction costs are beyond the control of the producer (iecost of fuel per liter) producers can control the amount andtypes of inputs used on their operations

Since the commercial introduction of glyphosate-resistant cotton in 1997 and subsequent introduction of otherherbicide-resistant cotton varieties (ie glufosinate-resistantcotton in 2004) adoption of herbicide-resistant cotton hasbeen widespread In 2014 98 of upland cotton hectaresin Alabama were seeded to biotechnology varieties ofcotton 9 to insect resistant only varieties 6 to herbicideresistant only varieties and 83 to stacked trait (more thanone genetically engineered trait) varieties [3] With theadoption of herbicide-resistant varieties cotton producershave reduced weed management costs by reducing thenumber of herbicide applications and many have moved toa conservation tillage system [4 5] Unfortunately cottonproducers in Alabama and across the Cotton Belt arefaced with a rapidly expanding problem that reduces yieldsand increases production costs herbicide-resistant weeds

Hindawi Publishing CorporationInternational Journal of AgronomyVolume 2016 Article ID 1524389 9 pageshttpdxdoiorg10115520161524389

2 International Journal of Agronomy

Currently three glyphosate-resistant weed species have beenreported in Alabama Palmer amaranth (Amaranthus palmeriS Wats) horseweed (Conyza canadensis (L) Cronq) andcommon ragweed (Ambrosia artemisiifolia L) [6]

While the hectarage impacted by all three herbicide-resistant weeds continues to increase cotton producers inSoutheast and Mid-South US are fighting a difficult battleagainst herbicide-resistant Palmer amaranth a highly aggres-sive drought-tolerantweed that grows rapidly and is a prolificseed producer [7ndash9] Herbicide-resistant Palmer amaranthis considered the most troublesome weed species for cottonproducers in the Southeast and Mid-South US [10ndash12] Toaddress this challenging weed producers are reverting tomanagement practices that increase their production costssuch as additional herbicide treatments inversion tillage andhand weeding [4] Sosnoskie and Culpepper [10] found thatproducers in Georgia have increased the use of herbicideshand weeding and mechanical weed control (ie inversiontillage after harvest) as part of their weed managementsystems to address Palmer amaranth infestations in theirfields Managing Palmer amaranth through conventionaltillage is a threat to the over 44 thousand hectares of no-tilland strip-till acres on operations classified as cotton farms(NAICS 11192) in Alabama [1 5] An additional option thatmay help maintain conservation tillage hectares is to moveto a glufosinate-based system which has shown success incontrolling glyphosate-resistant Palmer amaranth [13 14]

Recent literature suggests that the use of cultural prac-tices such as cover crops and tillage may be necessary foroptimal control of Palmer amaranth [5 15ndash17] While thereis literature on the agronomic impacts of Palmer amaranthsuch as yield loss and decreased harvest efficiency [11 18]there is limited information on the effect of different weedmanagement strategies on net returns DeVore et al [16]acknowledge the need to understand economic benefitsof combining inversion tillage and cover crops to addressPalmer amaranth infestations however the authors onlydiscuss production costs associated with control As part ofa six-part benchmark study on glyphosate-resistant croppingsystemsWeirich et al [19] conclude that producers can adoptmore intensive herbicide management to control glyphosateresistant weeds and recognize equivalent net returns in theshort-term however the authors did not consider culturalpractices aside from crop rotation as part of the inten-sive herbicide management strategies Shurley et al [20]investigated the use of a high biomass rye cover crop tocontrol glyphosate-resistant Palmer amaranth in GeorgiaTheir findings indicated the highest net returnswere achievedin treatments with no cover crop instead of a rye cover cropwhich they attributed to lower production costs for the nocover crop treatment In Alabama Price et al [21] foundthat a conservation agriculture system (which includes ahigh residue rye cover crop and conservation tillage usinga subsoiler and no-till planter) increased cotton net returnsover conventional tillage in two out of three years underheavy pressure from Palmer amaranth and redroot pigweed(Amaranthus retroflexus L)

Although previous research with different productionsystems for Palmer amaranth control has shown mixed

results there is limited information on the effect of differentweed management strategies on net returns The objectiveof this analysis was to evaluate the effect of tillage covercrops and herbicide regimes on net returns above variabletreatment costs in glufosinate-resistant cotton productionsystems in Alabama to manage severe Palmer amaranthinfestations

2 Materials and Methods

Field experiments were conducted from 2009 to 2011 at theE V Smith Research Center Field Crops Unit (EVS) nearShorter Alabama (32N 251015840 289510158401015840 85W531015840 273110158401015840)The soil atthis site was a Compass sandy loam (coarse-loamy siliceoussubactive thermic Plinthic Paleudults) The experiment wasconducted on a site that had been in continuous strip-tillfor six years prior to the establishment of the experimentin fall 2008 The schedule of operations is displayed inTable 1

The site was infested with naturally occurring resistantand susceptible Palmer amaranth and to guarantee a sizeableseedbank approximately 28 million native glyphosate sus-ceptible Palmer amaranth seeds were broadcast per hectareA randomized complete block design with a split-split plottreatment restriction was used in each year of the exper-iment The main plots were two soil-inversion treatmentsfall inversion tillage (IT) and noninversion tillage (NIT)administered in the spring The subplots were three covercrops crimson clover (clover) cereal rye (rye) andwinter fal-low (fallow) The sub-subplots were three herbicide regimespreemergence (PRE) alone postemergence (POST) aloneand PRE+POST (Table 2)

A no herbicide check was included in the original experi-ment but was excluded from this analysis due to lack of weedcontrol variability within treatments and lack of yield dataThemain sub and sub-subplotswere 439 by 9m 146 by 9mand 36 by 9m respectively Treatments were replicated threetimes however they were not rerandomized each year due tothe tillage treatment

21 Tillage andCoverCropTreatments TheIT treatment con-sisted of one pass with a moldboard plow (30 cm) immedi-ately followed by (fb) one pass with a disk and one pass with acultivator in fall 2008 In the following years the IT plots weremanaged the same as the NIT plots Each year in the springthe IT and NIT plots were subsoiled prior to planting with anin-row subsoiler equipped with pneumatic tires behind theshank Each preceding fall rye and clover cover crops wereplanted using 101 and 28 kg haminus1 of seed respectively For ryethe var ldquoElbonrdquo was planted in 2009 and 2010 and in 2011the var ldquoWrens Abruzzirdquo was planted due to seed availabilityFor clover the var ldquoDixierdquo was planted in all three years Therye treatment was not fertilized in 2009 and 2010 however itwas fertilized with 67 kgNhaminus1 as a 33-0-0 granular fertilizerin 2011 In 2011 the clover treatment was replanted in earlyMarch due to establishment failure of the original plantingWinter weeds were allowed to grow over the winter in thefallow treatment

International Journal of Agronomy 3

Table 1 Schedule of operationsa

Operations Experiment years20082009 20092010 20102011

Broadcasting Palmer amaranth seed 19 NovFall inversion tillage 19 NovCover crop planting 20 Nov 6 Jan 2 DecCover crop (rye) fertilization mdash mdash 14 FebCover crop (clover) replant mdash mdash 3 MarWinter burn down (fallow) mdash mdash 31 MarRolling and termination of cover crops 22 Apr 18 May 19 AprSubsoiling 23 Apr 24 May 26 AprCotton planting 1 Jun 27 May 5 MayCotton fertilization 1 Jun 27 May 5 MayPRE application 3 Jun 27 May 6 MayPOST application 16 Jun 16 Jun 24 MayAdditional POST application mdash mdash 13 JuneGraminicide application 13 July 8 July 6 JulyLAYBY application 14 Aug 16 Aug 19 JulyCotton defoliation 26 Oct 14 Oct 13 SepCotton harvesting 9 Nov 20 Oct 30 SepaSchedule of operations adapted from Aulakh et al [15]

Table 2 Description of herbicide treatments

Herbicide regime Chemical Ratekg ai haminus1

PREa Pendimethalin Prowl BASF Ag Products Research Triangle Park NC USA 084Fomesafen Reflex Syngenta Crop Protection Inc Greensboro NC USA 028

POSTb Glufosinate Ignite Bayer Crop Science Research Triangle Park NC USA 060S-Metolachlor Dual II Magnum Syngenta Crop Protection Inc Greensboro NC USA 054

PRE+POSTb

Pendimethalin Prowl BASF Ag Products Research Triangle Park NC USA 084Fomesafen Reflex Syngenta Crop Protection Inc Greensboro NC USA 028Glufosinate Ignite Bayer Crop Science Research Triangle Park NC USA 060

S-Metolachlor Dual II Magnum Syngenta Crop Protection Inc Greensboro NC USA 054

LAYBYPrometryn Caporal Syngenta Crop Protection Inc Greensboro NC USA 084MSMA Drexel Chemical Company Memphis TN USA 14

Sethoxydim Poast Plus BASF Ag Products Research Triangle Park NC USA 028aPRE herbicides were applied using 145 L haminus1 of water carrier delivered through a CO2-pressurized backpack sprayer with 8002 flat-fan nozzles POSTherbicides were applied 15 to 20 days after planting cotton to 3 to 4 leaves of Palmer amaranth using 145 L haminus1 delivered through an ATV-mounted sprayerwith 8002 flat-fan spray nozzlesbIn 2011 a second POST application glufosinate (060 kg ai haminus1) was made to the POST and PRE+POST treatments for added weed control

In the spring cover crops (including fallow) were termi-nated using mechanical and chemical termination methodsA three-section straight bar rollercrimper (BighamBrothersInc Lubbock TXUSA)was used to roll the cover crops in allthree years (and fallow treatments in 2009 and 2010) followedby a chemical application of a mixture of 084 kg ae haminus1 ofglyphosate (Roundup Weathermax Monsanto CompanySt Louis MO USA) plus 049 kg ae haminus1 of glufosinate(Ignite Bayer Crop Science Research Triangle Park NCUSA) Mechanical termination on fallow treatments was notnecessary in 2011 since the fallow treatments received awinterburndown application of glufosinate (049 kg ae haminus1) and

glyphosate (084 kg ae haminus1) on March 31 Due to delayedcover crop planting in fall 2009 cover crops were terminateda month later in 2010 than in 2009 and 2011 After covercrop termination and spring tillage operations the followingglufosinate-resistant cotton varieties were planted FM 1845LLB2 in 2009 and FM 1735 LL in 2010 and 2011 (Bayer CropScience Research Triangle Park NC US) Cotton received anapplication of 101 kgNhaminus1 (34 kgNhaminus1 as a starter fertilizerand 67 kgNhaminus1 at the 8 to 10 leaf stage) each year

22 Herbicide Treatments The three herbicide treatmentsincluded in the study were PRE only POST only and


Table 3 Production costs (US$ haminus1) for cotton production by year

Production itemProduction cost

US$ haminus1

2009 2010 2011Production costs differing by treatmentTillagea

NIT 1539 1539 1539IT 7857 1539 1539

Cover cropb

Clover 18763 18763 37527Rye 17775 17775 23782Fallow 6485 6485 10925

Herbicide regimec

PRE 4062 4062 4062POST 6449 6449 11205PRE+POST 10511 10511 15267

Production costs based on yieldGinning and warehousing (US$ kgminus1) 0045Classing and promotion fee (US$ kgminus1) 0003aInversion tillage (IT) was performed in 2009 only In 2010 and 2011 the costfor tillage for all treatments was the cost of noninversion tillage (NIT)bClover is crimson clover rye is cereal rye fallow is winter fallow In 2011clover was replanted and rye was only fertilized in 2011 Fallow received anadditional application of glyphosate and glufosinate as a winter burndowncPOST and PRE+POST received an additional POST application of glufosi-nate in 2011

PRE+POST Table 2 outlines the herbicide regimes for eachtreatment A last application (LAYBY) directed spray wasapplied each year to all plots In 2011 the POST andPRE+POST treatments received an additional application ofglufosinate (06 kg ai haminus1) on June 13 due to extensive Palmeramaranth growth These plots would not have been har-vestable if not for the second POST application Additionaldiscussion on the experiment as well as results related tocover crop biomass Palmer amaranth density and controland cotton yield are found in Aulakh et al [15]

23 Economic Analysis For the purposes of this analysisnet returns above variable treatment costs (net returns)were defined as the difference between revenues and cottonproduction costs (US$ haminus1) associated with each treatmentRevenues were calculated based on cotton lint and cottonseedyields and prices Since the seed cotton was not ginnedthe assumed ginning percentage was 40 and cotton fiberquality was not considered in this analysis Cotton lint(176US$ kgminus1) and cottonseed (24146US$ tonneminus1) pricesused in the analysis were the average cotton lint and cotton-seed prices received by Alabama producers in 2013 [1] Priceswere assumed constant across all three years of the analysis

Production costs associated with tillage cover crop estab-lishment and termination and herbicide regimes (Table 3)were adapted from machinery cost estimates [22] and cottonenterprise budgets [23 24] Input prices were assumed torepresent prices paid by producers in 2013 Two types ofproduction costs were considered costs that differed by

tillage cover crop and herbicide regime and yield varyingcosts Aside from production expenses related to treatmentsall other production expenses were assumed constant acrossthe experimental plots Costs associated with tillage covercrop management (fertilizer seed planting and termina-tion) herbicide regime and interest on operating capitalvaried by treatment and year Machinery costs included onlyvariable costs (fuel labor and repairs and maintenance)Yield varying costs included a ginning and warehousing feeand a classing and promotion fee Land rent crop insuranceand fixed expenses such as depreciation and managementcosts can differ substantially between producers Thereforethese expenses were not included in this analysis

24 Statistical Analysis Data were analysed using PROCGLIMMIX in SAS (SAS Institute Inc Cary NC USA)Dependent variables were net returns measured in US$ haminus1Year tillage cover crop herbicide regime and their inter-actions were considered fixed effects Replication the inter-action between replication and tillage and the interactionbetween replication and cover crop within tillage were con-sidered the random effects For net returns year year bytillage year by cover crop and year by herbicide effects werehighly significant (not shown)Therefore data were analysedby year in the final analysis As previously stated the noherbicide treatment was not included in the final analysisdue to lack of variability (multiple replications with zeroyields in the same treatment and year) in the existing dataFisherrsquos protected least significant difference (LSD) test at the119875 = 005 level of significance was used to separate treatmentmeans

3 Results and Discussion

The cotton lint yield within years and across years variedgreatly (Table 4) which directly influenced the variability ofnet returns within year and across years (Table 4) The yearwith the greatest yield and net return variability was 2009followed by 2011 Although treatments were approximatelythe same each year (with exceptions outlined in Section 21)weather and timing of operations differed between yearsCumulative precipitation and growing degree days (GDD)were calculated by summing the daily precipitation andGDD days from planting to harvest each year at EVSGrowing degree days (GDD) were calculated using a basetemperature of 1556∘C Cumulative precipitation during thecotton growing season was the highest in 2009 Total rainfallamounts were similar in 2010 and 2011 however the timing ofrainfall events was very different (Figure 1) Cumulative GDDwas the lowest for 2009 followed by 2011 and 2010 (Figure 2)In 2009 the cool wetweather at the endof the growing seasonheavily influenced cotton yields and subsequently net returnsThe below normal temperatures and above average rainfallcontinued into fall of 2009 andwinter of 2010 impacting covercrop planting and growth

The timing of operations differed each year specificallyrelated to cover crop planting and termination and cottonplanting and harvesting (Table 1) Producers are often faced


Table 4 Summary statistics for cotton lint yield (kg haminus1) and net returns (US$ haminus1)

YearCotton lint yield Net returns to cotton production

Mean Maximum Minimum CV Regional average Mean Maximum Minimum CVkg haminus1 US$ haminus1

2009 455 1193 49 69 638 584 1890 minus118 942010 512 824 130 27 609 722 1225 53 342011 1057 1447 640 17 836 1594 2420 856 23

750

625

500

375

250

125

0

Cum

ulat

ive p

reci

pita

tion

(mm

)

Days since planting1801651501351201059075604530150

2009

2010

2011

Figure 1 Cumulative precipitation (mm) for days since planting atE V Smith Research Center from 2009 to 2011

with similar constraints such as labor shortages or weatherdelays which can negatively influence the economic benefitsof cover crops through increased costs or less biomass pro-duction Cover crops were planted in mid-November 2008however cover crops were planted in early January 2010 forcrop year 2010 and December 2010 for crop year 2011 dueto late harvest of the previous cash crop While rye can beestablished in very cool weather temperatures of 333∘C arerequired for vegetative growth and the recommended plant-ing date is late September to early November [25] Previousresearch demonstrates that planting date of rye influencesthe amount of rye biomass produced and performance ofthe cover crop as part of the system [21] For clover therecommended planting date is even earlier from August toSeptember [25] As previously mentioned clover in 2011 wasreplanted inMarch due to lack of vegetative growth howeverthis was only 47 days prior to cover crop terminationReplanting clover in 2011 increased the establishment costsassociated with the clover treatments as compared to theother treatments

2009

2010

2011

3000

3750

2500

2250

2000

1750

1500

1250

1000

750

500

250

0

Cum

ulat

ive c

otto

n gr

owin

g de

gree

day

s (G

DD

)


Figure 2 Cumulative growing degree days (GDD) for cotton fordays since planting at E V Smith ResearchCenter from 2009 to 2011

Normal cotton progress in Alabama includes plantingbetween early April and mid-June and harvesting betweenearly September and mid-December Cotton was plantedwithin this range each year however in 2009 cotton wasplanted towards the end of the range (71 days after April 1)In 2009 due to a major rain event at the end of the growingseason cotton harvest was delayed until the second weekof November (161 days after planting) as compared to theend of October in 2010 (146 days after planting) and the endof September in 2011 (148 days after planting) Differencesin schedules of operations between years may explain thevariability of yields and net returns across years [21 26ndash28]Across all treatments 2011 was the only year with average cot-ton lint yields above the corresponding agricultural districtaverage [1] In 2009 and 2010 the average experimental yieldwas approximately 39 and 12 lower than the average agri-cultural district yield respectively (Table 4) EVS is locatedin the Black Belt Agricultural District (D40) as defined byUSDA [1] In Alabama average agricultural district yields are


Table 5 Analysis of variance and variance-component estimates for the net returns from cotton production by year

Fixed effects 2009 2010 2011DFa 119865 value Pr gt 119865 DF 119865 value Pr gt 119865 DF 119865 value Pr gt 119865

Tillage 1 10 3129 lt0001 1 2 002 0909 1 4 025 0646Cover 2 10 292 0100 2 8 135 0312 2 8 979 0007Tillage lowast cover 2 10 082 0468 2 8 092 0435 2 8 004 0960Herbicide 2 24 1314 00001 2 24 219 0134 2 24 022 0806Tillage lowast herbicide 2 24 409 0030 2 24 339 0051 2 24 201 0156Cover lowast herbicide 4 24 195 0134 4 24 201 0126 4 24 115 0356Tillage lowast cover lowast herbicide 4 24 202 0123 4 24 140 0263 4 24 167 0190Random effects Estimate Std err Estimate Std err Estimate Std errRep 24446 34715 3128 13900 0 0Rep lowast tillage 0 0 8129 16781 67626 55729Rep lowast cover (tillage) 33428 27832 13962 12594 19791 16627Residual 79268 22883 31465 9083 37953 10956aNumerator degrees of freedom denominator degrees of freedom

not separated by irrigated and nonirrigated acres Thereforethe average includes higher irrigated yields along with lowernonirrigated yields Furthermore the weed pressure in theexperiment may have been more severe than the weedpressure in the average field in the Black Belt AgriculturalDistrict For these reasons the average experimental yieldmay be less than the average agricultural district yield

Data were analysed across years and interactions be-tween year and treatment (tillage cover crop and herbicideregime) were all significant at 119875 le 005 (not shown) There-fore data were analysed by year The analysis of variance(Table 5) shows fixed and random effects by year

31 Herbicide Regime Herbicide regime had a significanteffect on net returns in one out of three years (Tables5 and 6) In 2009 applying PRE+POST instead of PREalone or POST alone increased net returns by 481 and228US$ haminus1 respectively Applying POST alone instead ofPRE alone increased net returns by 253US$ haminus1 Highernet returns for PRE+POST were due to increased Palmeramaranth control resulting in higher cotton lint yields [15]Adopting PRE+POST increased herbicide production costsby 64US$ haminus1 over PRE or a yield equivalent of 37 kg haminus1The yield increase due to PRE+POST as compared to PREalone all else held equal was over 290 kg haminus1 While therewas no statistical difference (119875 = 005) between any ofthe herbicide regimes in 2010 and 2011 PRE+POST had thehighest numerical net returns in both years

32 Tillage by Herbicide Interaction The tillage by herbicideinteraction was significant in one out of three years (Tables5 and 7) A closer examination of this interaction revealedin 2009 that ITPRE+POST had the highest net returnsand NITPOST had the lowest net returns however thefollowing years NITPRE was the most profitable treatment(Table 6) There was little significant difference outside of2009 partially due to lower yield variability In 2009 net

Table 6 Influence of tillage cover crop and herbicide treatmentson net returns (US$ haminus1) by year

Treatment 2009 2010 2011US$ haminus1

Tillage systema

Noninversion 261 716 1650Inversion 906 729 1537LSD (120572 = 005)b 257 NS NS

Cover cropClover 780 804 1432Rye 504 660 1492Fallow 468 703 1857LSD (120572 = 005) NS NS 240

Herbicide regimesPRE 339 755 1576POST 592 651 1587PRE+POST 820 761 1618LSD (120572 = 005) 194 NS NS

aThe inversion tillage (IT) treatment consisted of one pass with a moldboardplow immediately followed by one pass with a disk and one pass with acultivator in fall 2008 In 2010 and 2011 the IT plots were managed the sameas the noninversion (NIT) plots The IT and NIT plots were subsoiled eachspring prior to plantingbLSD (least significant difference) for comparing any twomeans within yearNS is not significant

returns from ITPRE+POST were eight times larger thanNITPRE Furthermore net returns from ITPRE+POSTwere two times larger than net returns fromNITPRE+POSTand ITPRE These results clearly show the variability in netreturns in 2009 across tillage by herbicide regime treatmentsdue to high concentrations of Palmer amaranth and moreeffective control using IT and PRE+POST [15] Additionallynet returns in 2009 were heavily influenced by lower yieldsdue to cooler wetter weather during the growing season andat harvest as compared to 2010 and 2011


Table 7 Influence of tillage system by herbicide interaction on netreturns (US$ haminus1) by year

Tillage systemtreatmenta

Herbicide regimePRE POST PRE+POST LSD (120572 = 005)b

US$ haminus1

2009Noninversion 132 123 529 274Inversion 546 1062 1111LSD (120572 = 005)c 325

2010Noninversion 836 612 699 173Inversion 674 690 824LSD (120572 = 005) NS

2011Noninversion 1708 1602 1641 NSInversion 1445 1571 1594LSD (120572 = 005) NSaThe inversion tillage (IT) treatment consisted of one pass with a moldboardplow immediately followed by one pass with a disk and one pass with acultivator in fall 2008 In 2010 and 2011 the IT plots were managed the sameas the noninversion (NIT) plots The IT and NIT plots were subsoiled eachspring prior to plantingbLSD (least significant difference) for comparing any two means withintillage treatment NS is not significantcLSD for comparing any two means within herbicide regime and acrosstillage and herbicide regime

In 2010 the tillage by herbicide interaction was notsignificant (119875 = 0051) and post hoc tests (LSD) indicateda significant difference within tillage treatment Noninver-sion tillage with a PRE herbicide regime (NITPRE) hadnet returns 22359US$ haminus1 greater than NITPOST Thelack of statistical difference between treatments in 2011may be partially due to the additional POST applicationwhich increased yields by further reducing competition fromPalmer amaranth and increased production costs associatedwith POST and PRE+POST treatments

While not statistically significant in all three years therewas a noticeable trend across all three years of the experimentUtilizing IT in the first year (when Palmer amaranth was themost severe) along with PRE+POST herbicide regime eachyear provided the highest total net returns when summedacross the system While the NIT system with PRE herbicideregime provided the highest net returns in 2010 and 2011there was no statistical difference across tillage and herbicideregimes and the increase in net returns was not enough tooffset the losses in 2009 Assuming the additional variablecosts associated with cotton production aside from land rentand crop insurance were 900US$ haminus1 only two treatmentoptions (ITPOST and ITPRE+POST) in 2009 covered thetotal variable costs On average in 2010 revenues were notlarge enough to cover the total variable costs while in 2011revenues were larger due to higher cotton lint yields and onaverage revenues would cover total variable costs associatedwith cotton production across all tillage and herbicide com-binations

33 Cover Crops As shown in Table 5 the cover croptreatment was only significant in 2011 (119875 = 00071) In 2011the fallow treatment had the highest net returns and exceededthe net returns to clover and rye treatments by 425 and365US$ haminus1 respectively (Table 6) There was no statisticaldifference between clover and rye treatments

Previous research has shown that the use of a highresidue rye cover crop as part of a conservation systemprovides mulching and allelopathic effects that limits weedgermination and growth especially under high biomass levels[21 29ndash35] The rye treatment did not perform as well asexpected based on the previous research In 2009 and 2010rye biomass amounts were lower than clover most likelydue to lack of fertilization [25] The average cost of biomassproduction (cover crop establishment and termination costdivided by biomass output) was higher for rye in 2009 and2010 (448US$ 100 kgminus1 and 908US$ 100 kgminus1 resp) thanfor clover (335US$ 100 kgminus1 and 715US$ 100 kgminus1) Delayedplanting of the cover crop also likely reduced the amountof biomass produced in both clover and rye in 2010 andclover in 2011 Due to replanting clover in 2011 the aver-age cost for clover was 1618US$ 100 kgminus1 as compared to366US$ 100 kgminus1 for rye

There were several production challenges within theexperiment that may have played an underlying role in theoutcome of the study in conjunction with the treatmentsDifferent results may have been realized if (1) rye treatmenthad received nitrogen fertilizer each year [25] (2) scheduleof operations was more consistent between years (ie dateof cover crop planting date of cotton planting) and (3)operations within year had occurred at the optimal time(ie cover crops were planted after December 1 in 2010 and2011) Inconsistency in the schedule of operations betweenyears and timing within year was largely driven by weatherbeyond the control of the researchers and a situation oftenfaced by cotton producers Based on these differences theseresults are applicable to operations with similar soil types andmanagement decisions and in years with similar weatherFuture research is needed to determine if it is necessary toincorporate these differences into the analysis and if so thebest way to accomplish this task Finally this was a short-termanalysis and did not consider the long-term benefits of theadoption of a cover crop and the negative impact of revertingto IT after the long-term use of NIT [5 36]

4 Conclusions

Cotton producers in Alabama and across the Southeastand Mid-South are struggling to control Palmer amaranthinfestations on their operations Many producers are turningto cultural management techniques such as IT and covercrops along with herbicide treatments as part of their weedmanagement system This study evaluated the influence oftillage cover crops and herbicide regimes on net returnsfrom cotton production The data used were from an experi-ment conducted at EVS near Shorter Alabama in 2009 2010and 2011


Results indicated that under heavy Palmer amaranth pop-ulations IT with a POST or PRE+POST herbicide applicationhad the highest net returns in the first year however the eco-nomic benefit of IT across all herbicide treatments was notstatistically significant in 2010 and 2011 For the NIT systemapplying a PRE+POST in 2009 and a PRE in 2010 providedthe highest net returnsWith the exception of 2011 cover cropuse did not negatively impact net returns as there was nostatistical difference between cover crops and fallow Whilethis research did not directly address erosion potential dueto IT planting a cover crop immediately following IT wouldminimize the potential for soil erosion in situations whereIT was necessary to control Palmer amaranth Additionalresearch is needed to further investigate economic impact ofusing cultural techniques to control Palmer amaranth andother herbicide-resistant weeds in a conservation system

Competing Interests

Mention of a trade name proprietary product or specificequipment does not constitute a guarantee or warranty by theUSDA and does not apply endorsement of a product to theexclusion of others that may be suitable

References

[1] United States Department of Agriculture ldquoNational Agricul-tural Statistics Service (USDA-NASS)rdquo 2014 httpquickstatsnassusdagov

[2] USDA-NASS ldquoAppendix B General Explanation and Censusof Agriculture Report Formrdquo 2012 httpwwwagcensususdagovPublications2012Full ReportVolume 1 Chapter 1 USusappxbpdf

[3] USDA-NASS ldquoAcreagemdashJune 2014rdquo 2014 httpusdamannlibcornelleduusdanassAcre2010s2014Acre-06-30-2014pdf

[4] J E Carpenter and L P Gianessi ldquoEconomic impacts ofglyphosate-resistant weedsrdquo in Glyphosate Resistance in Cropsand Weeds History Development and Management pp 297ndash312 John Wiley amp Sons Hoboken NJ USA 2010

[5] A J Price K S Balkcom S A Culpepper J A Kelton RL Nichols and H Schomberg ldquoGlyphosate-resistant Palmeramaranth a threat to conservation tillagerdquo Journal of Soil andWater Conservation vol 66 no 4 pp 265ndash275 2011

[6] I HeapThe International Survey of Herbicide ResistantWeeds2014 httpwwwweedsciencecom

[7] M J Horak and T M Loughin ldquoGrowth analysis of fourAmaranthus speciesrdquo Weed Science vol 48 no 3 pp 347ndash3552000

[8] P E Keeley CH Carter and RMThullen ldquoInfluence of plant-ing date on growth of Palmer amaranth (Amaranthus palmeri)rdquoWeed Science vol 35 pp 199ndash204 1987

[9] J K Norsworthy G Griffith T GriffinM Bagavathiannan andE E Gbur ldquoIn-field movement of glyphosate-resistant Palmeramaranth (Amaranthus palmeri) and its impact on cotton lintyield evidence supporting a zero-threshold strategyrdquo WeedScience vol 62 no 2 pp 237ndash249 2014

[10] L M Sosnoskie and A S Culpepper ldquoGlyphosate-resistantpalmer amaranth (Amaranthus palmeri) increases herbicideuse tillage and hand-weeding in georgia cottonrdquoWeed Sciencevol 62 no 2 pp 393ndash402 2014

[11] S M Ward T M Webster and L E Steckel ldquoPalmer amaranth(Amaranthus palmeri) a reviewrdquo Weed Technology vol 27 no1 pp 12ndash27 2013

[12] T M Webster and R L Nichols ldquoChanges in the prevalenceof weed species in the major agronomic crops of the SouthernUnited States 19941995 to 20082009rdquo Weed Science vol 60no 2 pp 145ndash157 2012

[13] A S Culpepper A C York P Roberts and J R WhitakerldquoWeed control and crop response to glufosinate applied to lsquoPHY485WRFrsquo cottonrdquoWeed Technology vol 23 no 3 pp 356ndash3622009

[14] A W MacRae A S Culpepper and J M Kichler ldquoManagingglyphosate-resistant Palmer amaranth in Liberty Link cottonrdquoin Proceedings of the Beltwide Cotton Conference p 1232National Cotton Council of America 2007

[15] J Aulakh A Price S Enloe E SantenGWehtje andM Patter-son ldquoIntegrated palmer amaranth management in glufosinate-resistant cotton I Soil-inversion high-residue cover crops andherbicide regimesrdquo Agronomy vol 2 no 4 pp 295ndash311 2012

[16] J D DeVore J K Norsworthy and K R Brye ldquoInfluences ofdeep tillage and a rye cover crop on glyphosate-resistant Palmeramaranth (Amaranthus palmeri) emergence in cottonrdquo WeedTechnology vol 26 no 4 pp 832ndash838 2012

[17] J A Kelton A J Price M G Patterson C D Monks and Evan Santen ldquoEvaluation of tillage and herbicide interaction forAmaranthus control in cottonrdquoWeed Technology vol 27 no 2pp 298ndash304 2013

[18] D T Smith R V Baker and G L Steele ldquoPalmer amaranth(Amaranthus palmeri) impacts on yield harvesting and gin-ning in dryland cotton (Gossypium hirsutum)rdquo Weed Technol-ogy vol 14 no 1 pp 122ndash126 2000

[19] J WWeirich D R Shaw M D Owen et al ldquoBenchmark studyon glyphosate-resistant cropping systems in the United StatesPart 5 effects of glyphosate-based weed management programson farm-level profitabilityrdquoPestManagement Science vol 67 no7 pp 781ndash784 2011

[20] W D Shurley A R Smith S Culpepper and R L NicholsldquoEconomic analysis of heavy rye cover crop to controlglyphosate resistant Palmer amaranth in cottonrdquo in Proceedingsof the Beltwide Cotton Conference p 400 National CottonCouncil of America New Orleans La USA January 2014

[21] A J Price K S Balkcom L M Duzy and J A Kelton ldquoHer-bicide and cover crop residue integration for amaranthuscontrol in conservation agriculture cotton and implications forresistance managementrdquo Weed Technology vol 26 no 3 pp490ndash498 2012

[22] W F Lazarus Machinery Cost Estimates University of Min-nesota Minneapolis Minn USA 2014

[23] Alabama Cooperative Extension System (ACES) ldquoAlabamaenterprise budget summariesrdquo 2014 httpwwwaceseduagriculturebusiness-managementbudgets

[24] Mississippi State University (MSU) ldquoCotton 2014 PlanningBudgetsrdquoMississippi StateUniversity 2014 httpwwwageconmsstateeduwhatwedobudgetsdocsMSUCOT14pdf

[25] A Clark Ed Managing Cover Crops Profitably SustainableAgriculture Network Beltsville Md USA 3rd edition 2007

[26] C W Bednarz W D Shurley and W S Anthony ldquoLosses inyield quality and profitability of cotton from improper harvesttimingrdquo Agronomy Journal vol 94 no 5 pp 1004ndash1011 2002

[27] W T Pettigrew ldquoImproved yield potential with an early plantingcotton production systemrdquoAgronomy Journal vol 94 no 5 pp997ndash1003 2002


[28] W T Pettigrew W T Molin and S R Stetina ldquoImpact ofvarying planting dates and tillage systems on cotton growth andlint yield productionrdquoAgronomy Journal vol 101 no 5 pp 1131ndash1138 2009

[29] J P Barnes and A R Putnam ldquoRye residues contribute weedsuppression in no-tillage cropping systemsrdquo Journal of ChemicalEcology vol 9 no 8 pp 1045ndash1057 1983

[30] J R Teasdale C E Beste and W E Potts ldquoResponse of weedsto tillage and cover crop residuerdquoWeed Science vol 39 pp 195ndash199 1991

[31] J R Teasdale and C L Mohler ldquoThe quantitative relation-ship between weed emergence and the physical properties ofmulchesrdquoWeed Science vol 48 no 3 pp 385ndash392 2000

[32] D W Reeves A J Price and M G Patterson ldquoEvaluation ofthree winter cereals for weed control in conservation-tillagenontransgenic cottonrdquoWeed Technology vol 19 no 3 pp 731ndash736 2005

[33] A J Price D W Reeves and M G Patterson ldquoEvaluation ofweed control provided by three winter cereals in conservation-tillage soybeanrdquo Renewable Agriculture and Food Systems vol21 no 3 pp 159ndash164 2006

[34] A J Price D W Reeves M G Patterson et al ldquoWeed controlin peanut grown in a high-residue conservation-tillage systemrdquoPeanut Science vol 34 no 1 pp 59ndash64 2007

[35] A J Price M E Stoll J S Bergtold et al ldquoEffect of cover cropextracts on cotton and radish radicle elongationrdquo Communica-tions in Biometry and Crop Science vol 3 no 1 pp 60ndash66 2008

[36] D J Boquet R L Hutchinson and G A Breitenbeck ldquoLong-term tillage cover crop and nitrogen rate effects on cottonplant growth and yield componentsrdquoAgronomy Journal vol 96no 5 pp 1443ndash1452 2004

Submit your manuscripts athttpwwwhindawicom

Nutrition and Metabolism

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014


Food ScienceInternational Journal of

Agronomy


International Journal of



Microbiology

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom

Applied ampEnvironmentalSoil Science

Volume 2014

AgricultureAdvances in


PsycheHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BiodiversityInternational Journal of


ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GenomicsInternational Journal of


Plant GenomicsInternational Journal of


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Forestry ResearchInternational Journal of


Journal of BotanyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

EcologyInternational Journal of


Veterinary Medicine International


Cell BiologyInternational Journal of


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Currently three glyphosate-resistant weed species have beenreported in Alabama Palmer amaranth (Amaranthus palmeriS Wats) horseweed (Conyza canadensis (L) Cronq) andcommon ragweed (Ambrosia artemisiifolia L) [6]

While the hectarage impacted by all three herbicide-resistant weeds continues to increase cotton producers inSoutheast and Mid-South US are fighting a difficult battleagainst herbicide-resistant Palmer amaranth a highly aggres-sive drought-tolerantweed that grows rapidly and is a prolificseed producer [7ndash9] Herbicide-resistant Palmer amaranthis considered the most troublesome weed species for cottonproducers in the Southeast and Mid-South US [10ndash12] Toaddress this challenging weed producers are reverting tomanagement practices that increase their production costssuch as additional herbicide treatments inversion tillage andhand weeding [4] Sosnoskie and Culpepper [10] found thatproducers in Georgia have increased the use of herbicideshand weeding and mechanical weed control (ie inversiontillage after harvest) as part of their weed managementsystems to address Palmer amaranth infestations in theirfields Managing Palmer amaranth through conventionaltillage is a threat to the over 44 thousand hectares of no-tilland strip-till acres on operations classified as cotton farms(NAICS 11192) in Alabama [1 5] An additional option thatmay help maintain conservation tillage hectares is to moveto a glufosinate-based system which has shown success incontrolling glyphosate-resistant Palmer amaranth [13 14]

Recent literature suggests that the use of cultural prac-tices such as cover crops and tillage may be necessary foroptimal control of Palmer amaranth [5 15ndash17] While thereis literature on the agronomic impacts of Palmer amaranthsuch as yield loss and decreased harvest efficiency [11 18]there is limited information on the effect of different weedmanagement strategies on net returns DeVore et al [16]acknowledge the need to understand economic benefitsof combining inversion tillage and cover crops to addressPalmer amaranth infestations however the authors onlydiscuss production costs associated with control As part ofa six-part benchmark study on glyphosate-resistant croppingsystemsWeirich et al [19] conclude that producers can adoptmore intensive herbicide management to control glyphosateresistant weeds and recognize equivalent net returns in theshort-term however the authors did not consider culturalpractices aside from crop rotation as part of the inten-sive herbicide management strategies Shurley et al [20]investigated the use of a high biomass rye cover crop tocontrol glyphosate-resistant Palmer amaranth in GeorgiaTheir findings indicated the highest net returnswere achievedin treatments with no cover crop instead of a rye cover cropwhich they attributed to lower production costs for the nocover crop treatment In Alabama Price et al [21] foundthat a conservation agriculture system (which includes ahigh residue rye cover crop and conservation tillage usinga subsoiler and no-till planter) increased cotton net returnsover conventional tillage in two out of three years underheavy pressure from Palmer amaranth and redroot pigweed(Amaranthus retroflexus L)

Although previous research with different productionsystems for Palmer amaranth control has shown mixed

results there is limited information on the effect of differentweed management strategies on net returns The objectiveof this analysis was to evaluate the effect of tillage covercrops and herbicide regimes on net returns above variabletreatment costs in glufosinate-resistant cotton productionsystems in Alabama to manage severe Palmer amaranthinfestations

2 Materials and Methods

Field experiments were conducted from 2009 to 2011 at theE V Smith Research Center Field Crops Unit (EVS) nearShorter Alabama (32N 251015840 289510158401015840 85W531015840 273110158401015840)The soil atthis site was a Compass sandy loam (coarse-loamy siliceoussubactive thermic Plinthic Paleudults) The experiment wasconducted on a site that had been in continuous strip-tillfor six years prior to the establishment of the experimentin fall 2008 The schedule of operations is displayed inTable 1

The site was infested with naturally occurring resistantand susceptible Palmer amaranth and to guarantee a sizeableseedbank approximately 28 million native glyphosate sus-ceptible Palmer amaranth seeds were broadcast per hectareA randomized complete block design with a split-split plottreatment restriction was used in each year of the exper-iment The main plots were two soil-inversion treatmentsfall inversion tillage (IT) and noninversion tillage (NIT)administered in the spring The subplots were three covercrops crimson clover (clover) cereal rye (rye) andwinter fal-low (fallow) The sub-subplots were three herbicide regimespreemergence (PRE) alone postemergence (POST) aloneand PRE+POST (Table 2)

A no herbicide check was included in the original experi-ment but was excluded from this analysis due to lack of weedcontrol variability within treatments and lack of yield dataThemain sub and sub-subplotswere 439 by 9m 146 by 9mand 36 by 9m respectively Treatments were replicated threetimes however they were not rerandomized each year due tothe tillage treatment

21 Tillage andCoverCropTreatments TheIT treatment con-sisted of one pass with a moldboard plow (30 cm) immedi-ately followed by (fb) one pass with a disk and one pass with acultivator in fall 2008 In the following years the IT plots weremanaged the same as the NIT plots Each year in the springthe IT and NIT plots were subsoiled prior to planting with anin-row subsoiler equipped with pneumatic tires behind theshank Each preceding fall rye and clover cover crops wereplanted using 101 and 28 kg haminus1 of seed respectively For ryethe var ldquoElbonrdquo was planted in 2009 and 2010 and in 2011the var ldquoWrens Abruzzirdquo was planted due to seed availabilityFor clover the var ldquoDixierdquo was planted in all three years Therye treatment was not fertilized in 2009 and 2010 however itwas fertilized with 67 kgNhaminus1 as a 33-0-0 granular fertilizerin 2011 In 2011 the clover treatment was replanted in earlyMarch due to establishment failure of the original plantingWinter weeds were allowed to grow over the winter in thefallow treatment









PRE+POSTb











US$ haminus1


NIT 1539 1539 1539IT 7857 1539 1539

Cover cropb


Herbicide regimec

PRE 4062 4062 4062POST 6449 6449 11205PRE+POST 10511 10511 15267














2009 455 1193 49 69 638 584 1890 minus118 942010 512 824 130 27 609 722 1225 53 342011 1057 1447 640 17 836 1594 2420 856 23

750

625

500

375

250

125

0

Cum

ulat

ive p

reci

pita

tion

(mm

)


2009

2010

2011



2009

2010

2011

3000

3750

2500

2250

2000

1750

1500

1250

1000

750

500

250

0

Cum

ulat

ive c

otto

n gr

owin

g de

gree

day

s (G

DD

)














Tillage systema










US$ haminus1









4 Conclusions




Competing Interests


References








































Journal of




Agronomy





Microbiology




Volume 2014
































PRE+POSTb











US$ haminus1


NIT 1539 1539 1539IT 7857 1539 1539

Cover cropb


Herbicide regimec

PRE 4062 4062 4062POST 6449 6449 11205PRE+POST 10511 10511 15267














2009 455 1193 49 69 638 584 1890 minus118 942010 512 824 130 27 609 722 1225 53 342011 1057 1447 640 17 836 1594 2420 856 23

750

625

500

375

250

125

0

Cum

ulat

ive p

reci

pita

tion

(mm

)


2009

2010

2011



2009

2010

2011

3000

3750

2500

2250

2000

1750

1500

1250

1000

750

500

250

0

Cum

ulat

ive c

otto

n gr

owin

g de

gree

day

s (G

DD

)














Tillage systema










US$ haminus1









4 Conclusions




Competing Interests


References








































Journal of




Agronomy





Microbiology




Volume 2014



























US$ haminus1


NIT 1539 1539 1539IT 7857 1539 1539

Cover cropb


Herbicide regimec

PRE 4062 4062 4062POST 6449 6449 11205PRE+POST 10511 10511 15267














2009 455 1193 49 69 638 584 1890 minus118 942010 512 824 130 27 609 722 1225 53 342011 1057 1447 640 17 836 1594 2420 856 23

750

625

500

375

250

125

0

Cum

ulat

ive p

reci

pita

tion

(mm

)


2009

2010

2011



2009

2010

2011

3000

3750

2500

2250

2000

1750

1500

1250

1000

750

500

250

0

Cum

ulat

ive c

otto

n gr

owin

g de

gree

day

s (G

DD

)














Tillage systema










US$ haminus1









4 Conclusions




Competing Interests


References








































Journal of




Agronomy





Microbiology




Volume 2014




























2009 455 1193 49 69 638 584 1890 minus118 942010 512 824 130 27 609 722 1225 53 342011 1057 1447 640 17 836 1594 2420 856 23

750

625

500

375

250

125

0

Cum

ulat

ive p

reci

pita

tion

(mm

)


2009

2010

2011



2009

2010

2011

3000

3750

2500

2250

2000

1750

1500

1250

1000

750

500

250

0

Cum

ulat

ive c

otto

n gr

owin

g de

gree

day

s (G

DD

)














Tillage systema










US$ haminus1









4 Conclusions




Competing Interests


References








































Journal of




Agronomy





Microbiology




Volume 2014


































Tillage systema










US$ haminus1









4 Conclusions




Competing Interests


References








































Journal of




Agronomy





Microbiology




Volume 2014




























US$ haminus1









4 Conclusions




Competing Interests


References








































Journal of




Agronomy





Microbiology




Volume 2014


























Competing Interests


References








































Journal of




Agronomy





Microbiology




Volume 2014




































Journal of




Agronomy





Microbiology




Volume 2014
























Research Article Assessing the Economic Impact of Inversion...

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