Influence of Dose and Application Timing on the Efficacy of Harvest Aid in Cotton-Winter Wheat Double Cropping System of China

Cotton-based double cropping, such as cotton-winter wheat, plays an important role in combining food security and farmer's income in the Yellow River Valley of China. Harvesting the cotton in time to plant winter-wheat by mid-October is critical for this double cropping system. Normally, cotton is picked by hand in this region. However, changes in China's social economic condition have led to a shortage of workers to pick the cotton and, therefore, most producers have to introduce mechanized harvesting. Harvest aid chemicals can be used to enhance defoliation and boll opening and provide the potential for once-over mechanical harvest. This study was carried out for determining the effects of different application times at 20, 15 and 10 days pre-harvest and three doses of thidiazuron + ethephon on defoliation, boll opening, cotton yield and seed quality in cotton-winter wheat double cropping system in the Yellow River Valley. Defoliation and boll opening were all increased with earlier application of harvest aid, and defoliation also was increased with higher doses. Late application of harvest aid reduced first harvest yield, whereas total seedcotton yield was unaffected. Both application time and dose did not affect boll weight, ginning percentage, and seed quality. However, effective dose was increased with delaying application of harvest aid.