1. Comparison of Conventional, Roundup Ready, and Liberty-Link Cotton Weed Management Programs in Two Tillage Systems Michael Patterson, Bob Goodman and Dale Monks Auburn University Wilson Faircloth USDA-ARS, Dawson Ga.

2. Alabama 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.

3. Research 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.

4. Materials and Methods Locations Tennessee Valley Research and Extension Center Belle Mina (Decatur clay loam) Wiregrass Research and Extension Center Headland (Dothan sandy loam )

5. Materials and Methods Experimental Particulars Time frame: 2005, 2006 Varieties: FM 966, FM 960 RR, FM 966 LL Conventional and reduced tillage. Six Treatments Replicated four times Plot Dimensions: both north and south AL = four rows by 40’ long, each plot separated by four border rows

6. Materials and Methods Experimental 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

7. Tillage/Herbicide Treatments

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

9. Effect of Herbicide System Fiber Strength and Percent Lint (north Alabama) Herbicide System Strength of Fiber g/tex Percent Lint 2006 RR variety29.744.4 LL variety31.743.1 CV variety31.744.6 LSD (.05)0.70.8

10. Effect of Tillage on Broadleaf Weed Control (north Alabama) Tillage System %Control 2005 %Control 2006 Reduced till 98 93 Conv till 98 84 LSD (.05) NS 5

11. Effect of Tillage on Cotton Yield and Economic Return (south Alabama) Tillage System Lint Lb/A$/System Reduced till1576700 Conv till1425625 LSD (.05)105----

12. Effect of Herbicide System on Weed Control and Cotton Yield (south Alabama) Variable RR LL CVLSD.05 % Grass 95 94 893 % Brdlf 94 89 856 Lint #/A156414611326125 % Lint 41.6 39.4 40.80.9 $/System 686 649 578----

13. 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.

14. 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.

15. Implications 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.

16. Support 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.

17. Q Questions?