Effect of Boll Age and Harvesting Period on Fiber Properties of Egyptian and Upland Cotton Cultivars

The physical properties of cotton fibers for the successive age of development were studied in three different periods. Three cultivars of Egyptian and Upland cottons; Giza 75, McNair 220 and Tamcot H. 37 , were planted at Fayoum Experiment Farm, Faculty of Agriculture in 1984 season. Fiber properties were studied on samples obtained from five successive stages of boll development in three different periods. Data obtained revealed that fibers from both Egyptian and Upland cultivars showed substantial increment in micronaire reading up to 42 days after flowering. Micronaire reading showed a trend similar to fiber maturity percentage in studied cultivars.
Within each period, fibers tended to be stronger, more extensible, tougher and have higher stiffness with the increase in boll age. The rate of increment in the successive boll ages for fiber strength and elongation characters were markedly higher in the Egyptian cultivar than the American upland cultivars, especially in the younger boll ages. Fiber length was slightly affected by the environment growth conditions. However, the increase in fiber length was progressive from the age of 21 days up to the age of 35 days.