Effect of Nitrogen Rates and Flowering Dates on Fiber Quality of Cotton (Gossypium hirsutum L.)

Nitrogen (N) supply during boll setting and maturation period of cotton can be critical in determining fiber quality. The study aims to investigate the relationship between N rates and formation of fiber length, strength, maturity and micronaire in bolls with different flowering dates. Field experiments were conducted using two cotton cultivars (Kemian 1 and NuCOTN 33B) and three N fertilization rates (0, 240, and 480 kg N ha -1 ) in Nanjing and Xuzhou in 2005 and in Anyang in 2007, China. The fiber length, strength, maturity, micronaire, and N concentration per unit area (N A) of the subtending leaf of cotton boll were analyzed. N fertilization rates, flowering dates, and N fertilization rates × flowering dates significantly (P ≤ 0.05) affected N A and the formation of fiber length, strength, maturity and micronaire. N fertilization rates affected fiber quality by influencing NA which was significantly related to rate and duration of the fiber quality formation process. The optimal N A for fiber quality formation was varied. For bolls flowering before August 25, when mean daily temperature during boll maturation period (MDT BMP ) was higher than 21°C, NA in the 240 kg N ha -1