Comparison of Conventional, Roundup Ready, and Liberty-Link Cotton Weed Management Programs

in Two Tillage Systems

Michael Patterson, Bob Goodman and Dale MonksAuburn University

Wilson Faircloth USDA-ARS, Dawson Ga.

Alabama CottonAlabama Cotton

In Alabama and most of the southeast, Roundup Ready Cotton comprises 90% to 95% of the acreage.

The remainder of cotton acreage is planted in conventional (non-transgenic) or Liberty-Link varieties.

Over 75% of Alabama cotton is grown in some form of reduced tillage.

Research ObjectivesResearch Objectives

1. Evaluate cotton production in tilled and reduced till systems using Roundup Ready, Liberty Link, and conventional weed management programs.

2. Evaluate the economic viability of each tillage/weed management system.

3. Philosophize on the implications of the data.

Materials and MethodsMaterials and MethodsLocationsLocations

Tennessee Valley Research and Extension Center

Belle Mina(Decatur clay loam)

Wiregrass Research and Extension Center

Headland(Dothan sandy loam)

Materials and MethodsMaterials and MethodsExperimentalExperimental Particulars Particulars

Time frame: 2005, 2006Varieties: FM 966, FM 960 RR, FM 966 LLConventional and reduced tillage.Six Treatments Replicated four timesPlot Dimensions: both north and south AL =

four rows by 40’ long, each plot separated by four border rows

Materials and MethodsMaterials and MethodsExperimentalExperimental Particulars Particulars

Tractor mounted sprayer used: 15 GPA.Conventional tillage: north AL = disk 2X,

roterra. south AL = subsoil, disk, roterra.Reduced tillage: north AL = notill into wheat,

south AL = strip till into wheat.Soil types: north AL = clay loam. south AL

= sandy loam

Tillage/Herbicide Treatments Tillage/Herbicide Treatments

Trt.No. Tillage/Variety Soil-applied herbs POT herb-timing PDS herbs

1 Reduced/ RR Prowl-pre Rdup 3, Envoke 8 Layby Pro

2 Convent/RR Prowl-ppi Rdup 3, Envoke 8 Layby Pro

3 Reduced/LL Prowl-pre Ignite 3, Envoke 8 Layby Pro

4 Convent/LL Prowl-ppi Ignite 3, Envoke 8 Layby Pro

5 Reduced/CV Prowl+Cotoran-pre Staple 2, Envoke 8 Layby Pro

6 Convent/CV Prowl-ppi, Cot-pre Staple 2, Envoke 8 Layby Pro

Application and Timing to Cotton

Costs of Tillage/Weed Systems($ per acre)Costs of Tillage/Weed Systems($ per acre)

Trt.No. Tillage/Variety Tech fee Tillage/Herb* Total*1 Reduced/ RR 33 53/63 86/962 Convent/RR 33 55/63 88/963 Reduced/LL 15 57/67 72/824 Convent/LL 15 59/67 74/825 Reduced/CV 0 75/85 75/856 Convent/CV 0 77/85 77/85

*north AL / south AL

Effect of Herbicide System Fiber Strength Effect of Herbicide System Fiber Strength and Percent Lint (north Alabama)and Percent Lint (north Alabama)

HerbicideSystem

Strength of Fiber g/tex

Percent Lint2006

RR variety 29.7 44.4

LL variety 31.7 43.1

CV variety 31.7 44.6

LSD (.05) 0.7 0.8

Effect of Tillage on Broadleaf Weed Effect of Tillage on Broadleaf Weed Control (north Alabama) Control (north Alabama)

TillageSystem

%Control2005

%Control2006

Reduced till 98 93

Conv till 98 84

LSD (.05) NS 5

Effect of Tillage on Cotton Yield and Effect of Tillage on Cotton Yield and Economic Return (south Alabama)Economic Return (south Alabama)

TillageSystem

Lint Lb/A $/System

Reduced till 1576 700

Conv till 1425 625

LSD (.05) 105 ----

Effect of Herbicide System on Weed Control Effect of Herbicide System on Weed Control and Cotton Yield (south Alabama)and Cotton Yield (south Alabama)

Variable RR LL CV LSD .05

% Grass 95 94 89 3

% Brdlf 94 89 85 6

Lint #/A 1564 1461 1326 125

% Lint 41.6 39.4 40.8 0.9

$/System 686 649 578 ----

SUMMARY (north Alabama)SUMMARY (north Alabama)

No yield differences due to herbicide/tillage system in.

Decrease in late season broadleaf weed control for Conventional till in 2006.

Slight and inconsequential differences in strength and turnout between varieties.

Summary (south Alabama)Summary (south Alabama)

Greater yield in strip till than in conventional till in both years.

Greater yield in RR and LL systems than in conventional herbicide systems in both years.

Strip till returned $75.00 per acre more than conventional on average.

RR and LL returned $108.00 and $71.00 more per acre respectively than conventional herbicide system.

Implications of dataImplications of data

Probable reduction in economic return if south AL cotton growers return to conventional tillage and conventional herbicide technology.

New post-emergent herbicide technology with activity on pigweed is needed in light of the recent discovery of glyphosate and ALS resistant pigweed biotypes.

SupportSupport

Researchers gratefully acknowledge the financial assistance of Cotton Incorporated and Alabama cotton growers in conduction of this research.

Reseachers also gratefully acknowledge the support of Alabama Agricultural Experiment Station personnel at the Tennessee Valley and Wiregrass Research and Extension Centers.

Q

Questions?