The objectives of this research are to quantify the relationship between defoliation and harvest timeliness and cotton yield and grade and to determine the optimum stage of defoliation and harvest that would maximize net returns. Cotton (Suregrow 501) was planted April 27, 1998 and DPL 33B was planted May 10, 1999 at the University of Georgia Coastal Plain Experiment Station Ponder Farm in Tift County. Each plot was replicated 4 times. Maturity was determined using the "percent open boll" method. Each year, harvest aid applications began when the crop was approximately 10 percent open bolls (OB)and continued for 13 weeks. In 1998, highest income was achieved when the crop was defoliated at 50 to 60 percent open boll. In 1999, income was maximizedby defoliating at approximately 75 percent to 80 percent OB. Over the first 2 years of the study (1998 and 1999), income was maximized at approximately 70 percent OB. If defoliating too early, there are fewer harvestable bolls which may result in lower yield. Further, Micronaire and Staple may be reduced. If defoliating and harvesting too late, income may be reduced due loss of yield and quality. In Georgia, it is estimated that approximately 30 percent of the cotton is likely harvested after 100 percent OB. In 1999, harvest conditions were favorable and delaying defoliation and harvest was not costly. In 1998. harvest was hampered by rainfall. Bach week delay in defoliation and harvest after 100 percent OB resulted in 13.62 dollar per acre per week decline in income.
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