|Hutmacher, Robert - U OF CA SHAFTER RESEARCH|
|Godfrey, Larry - U OF CA SHAFTER RESEARCH|
Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: January 7, 2005
Publication Date: January 7, 2005
Citation: Funk, P.A., Armijo, C., Brashears, A. D., Showler, A.T., Fletcher, R.S., Hutmacher, R.B., Godfrey, L.D., McGuire, M.R., Bancroft, J.S. 2005. Thermal defoliation in 2004. In: Proceedings of the National Cotton Council, Beltwide Cotton Conferences, January 4-7, 2005, New Orleans, Louisiana. p. 648-656. 2005 CDROM. Interpretive Summary: Thermal defoliation has been shown to be effective both for preparing organic cotton for harvest and for eliminating late season insects in conventional cotton. Field trials in 2004 additionally demonstrated the effectiveness of thermal defoliation for giving more control over harvest timing to conventional cotton producers. Only one treatment is required (chemical defoliants sometimes require two) and cotton can be harvested within two days (chemical treatments usually require ten days). There were no adverse affects on the final value of the cotton fiber. These results were consistent in seven varieties in six locations in three states. Finally, yields can be improved using chemical boll openers, either in combination with chemical or thermal defoliation.
Technical Abstract: Organic cotton production requires alternative methods to harvest aid chemicals for crop termination and harvest preparation. Conventional cotton production occasionally requires greater control over the timing of crop termination and harvest preparation. Trials were conducted to determine the impact thermal defoliation has on plant physiology, yield and fiber value under various conditions. A self-propelled two-row prototype thermal defoliator was tested in eight fields at six locations in three states, with differing intervals between treatment and harvest. Desiccation, defoliation and open boll percentages were quantified at some locations, and seed cotton trash content and classing office data were recorded at others. Thermal defoliation resulted in crop termination in all four climate zones, successfully preparing all seven varieties for harvest. Thermal defoliation resulted in greater leaf kill and less leaf drop compared to standard harvest aid chemical treatments. Thermally defoliating cotton six days after treating the crop with ethephon resulted in a greater percentage of open bolls compared to standard harvest aid chemical treatments, thermal treatment alone, and no treatment. At the two locations where ginning and classing have been completed, fiber values were not statistically different (p < 0.05) between thermal and control treatments. Thermal defoliation appears to give growers greater control over harvest timing without adversely affecting fiber value.