Effect of nitrogen application rate on accumulation of dry matter and N,P,K in different periods of cotton growth as well as yield and quality of hybrid cotton under high-yield cultivated condition

Effects of nitrogen application rates 0,75,150,225,300 and 375 kg·hm-2 on accumulation of dry matter and N,P,K in different periods of hybrid cotton growth as well as yield and quality were studied under high yield conditions.The results showed that the increased accumulation amount of dry matter and N,P,K in hybrid cotton plants was connected with the increased nitrogen fertilizer,and the increased accumulation proportion was connected with the increased nitrogen fertilizer especially at later stage.In this experiment,The highest yield reached 300 kg·hm-2 treatment increasing by 1.66% compared with 225 kg·hm-2 treatment,but the difference was not significant.when nitrogen rate 375 kg·hm-2 was applied,the seed cotton yield decreased by 2.23% and 3.92% compared with 300 and 225 kg·hm-2,respectively.The nitrogen utilization decreased distinctly while the phosphorus and potassium utilization increased with more nitrogen fertilizer added.The fiber quality was compared and the result indicated that the fiber length was short and fiber strength was weak on the null nitrogen treatment.The fiber length and fiber strength were no significant difference between the different N nutrient treatments.The fiber strength was highest at 225 kg·hm-2 treatment while other index of fiber quality was no difference.