Optimum defoliation and harvest timings in different maturing cotton (G. hirsutum L.) cultivars in Çukurova region

The objective of this research was to determine influence of defoliation (50 (early), 70 (mid), and 90 (late) % OB) and harvest (early harvest (14 days after defoliation and a late harvest (28 days after defoliation) timings on yield and fiber quality, for cultivar maturity groups of cotton under Çukurova region conditions in 2011. A standard mixture of thidiazuron at the 120 g L rate and diuron at the rate of 60 g L was used across all application timings. Treatments were arranged in a split plot design, with three replications.Maximum yields were achieved when defoliation timings were 70 and 90 % OB. Yields when cotton was defoliated at the early defoliation timing were significantly found to be lower than yields of the optimum and delayed defoliation timings. Yields decreased significantly as harvest was delayed (14 and 28 days after application), when cotton was defoliated at the early defoliation timing. Micronaire values of early-maturing cultivar decreased significantly as harvest was delayed, however the micronaire values of late-maturing cultivar was not affected by harvesting timings. A significant decrease in fiber strength was found by the late harvest defoliated at late defoliation timing, although a significant increase was achieved by early defoliation timing.