Effects of Nitrogen Rates on Biomass and Nitrogen Accumulation of Cotton with Different Varieties in Growth Duration

To investigate the effects of nitrogen application rate on cotton biomass accumulation,nitrogen uptake,and nitrogen fertilization recovery rate in the cotton extremely early-maturation region,field experiment was carried out in Liaoyang,Liaoning,using two cotton cultivars Liaomian 19 and NuCOTN33B,with three nitrogen levels(0,240,480 kg·hm-2,respectively).The accumulated dynamic of biomass and nitrogen of cotton were described by Logistic curve equation.Nitrogen application rate changed biomass and nitrogen accumulation characteristics of cotton,and then affected the yield and quality of cotton.The results showed the beginning of speed nitrogen accumulation were 10～12 days earlier than that of biomass.With nitrogen at 240 kg·hm-2,biomass and nitrogen accumulation amount was the highest,eigenvalues of the dynamic accumulation model of cotton was the most harmonious,nitrogen recovery rate was the highest,thus lint yield was highest and the cotton fiber quality was the best.At 480 kg·hm-2 of nitrogen,accumulation amount and rate of biomass and nitrogen decreased,and the distributive indices of biomass in reproductive organ and lint yield reduced.