Submitted to: Journal of Cotton Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/29/2004
Publication Date: 1/1/2005
Citation: Funk, P.A., Armijo, C.B., McAlister,III, D.D., Lewis, B.E. 2004. Experimental thermal defoliator trials. The Journal of Cotton Science. 8(4):230-242. Available: http://www.cotton.org/journal/current/cfm
Interpretive Summary: This paper reports results from exhaustive analysis of field and fiber properties responses to thermal treatment of cotton plants by an experimental defoliation process. Comparisons are made to chemically defoliated and untreated controls. Rapid leaf kill following thermal treatment reduced insect populations and prepared the plants for earlier harvest. High Volume Instrument classification color grades were better with thermal treatments, resulting in more value per pound and per acre. Fiber and yarn properties were not affected. The demonstrated economic potential of this process means a prototype-scale treatment device will be built and additional experiments will be conducted.
Technical Abstract: Organic labeling rules restrict harvest aid chemical use. This study was conducted to determine whether thermal defoliation could prepare cotton for harvest without damaging fiber and seed quality. Untreated and standard chemical defoliant control treatments were compared with thermal treatments that consumed less than 10, between 10 and 15, and more than 15 gal/acre propane in an experimental defoliator that forced hot air through Acala 1517-99 and Delta Pine 565 cotton grown on a Brazito fine sandy loam (mixed, thermic, Typic Torripsamment) and a Harkey clay loam (coarse-silty, mixed, superactive, calcareous, thermic Typic Torrifluvent). In 2002, medium and high levels of thermal defoliation resulted in over 90% leaf kill within seven days. For the Delta Pine cultivar, high thermal treatment resulted in a $0.013/lb gain in fiber value over the untreated control. For the Acala, thermal treatment added $0.046/lb. For both cultivars, there were no significant differences in the majority of yarn quality measures. Assuming all else to be equal, thermal treatment could be economic if application costs were less than $15.79/ac for Delta Pine, or $42.83/ac for Acala. In 2001, aphid populations were significantly lower in thermally defoliated plots.