Determination of heat requirements as degree-day unit at different development periods of cotton (Gossypium hirsutum l.) varieties under siirt ecological conditions

The objective of this study was to determine the number of total calendar days and day-degree units required for each growth stages and entire growing period of cotton (Gossypium hirsutum L) cultivars grown commonly in Southeast Anatolia Region. By this means, anticipating the plants' different growth periods in response to recorded temperature data, to explain the differences that occur in different climate condition and effect of growing degree day and growing degree day values on cotton yield, yield components and fiber technological characteristics. The study was conducted in Siirt University, Faculty of Agriculture's experimental area as a randomized complete block design with four replications in 2015 cotton growing season. According to the results of study significant differences were obtained from used varieties in terms of days of squaring, days of flowering, days of firs open boll and their growing degree days units. In addition, there were significant differences for seed cotton yield, fiber yield, ginning percentage, first picking percentage, seeds number of per boll, single boll weight, seed cotton yield of per boll, fiber fineness, fiber maturity and fiber elongation.