Effects of Nitrogen Application Rates on Nutrition Uptake and Utilization, Yield and Fiber Quality of Cotton

【Objective】 The research aims to investigate the effects of nitrogen application rates on cotton yield, nutrient uptake and distribution, nitrogen utilization rate and fiber quality with the view of proving theoretical basis for rational nitrogen application in cotton production. 【Method】 Four nitrogen application levels (0, 112.5, 168.75 and 225 kg/hm², expressed by CK, N₁, N₂ and N₃ respectively) were established using cotton variety CCRI 60 in the field during 2018 and 2019. During the boll-opening period, plant samples were collected and separated into stem, leaf and reproductive organs, the dry matter quality, nitrogen, phosphorus and potassium accumulation were investigated, and nitrogen fertilizer utilization rate and cotton yield were calculated. 【Result】 The results showed that when the amounts of applied N were ranged from 0-225 kg/hm², the cotton yield increased with the increasing amounts of nitrogen fertilizer. Applying nitrogen fertilizer could increase the uptake of nitrogen, phosphorus and potassium in the boll-opening stage of cotton. When the amounts of applied N ranged from 0-168.75 kg/hm², the nitrogen, phosphorus, potassium uptake of cotton plant increased with the increasing nitrogen application rates. The excessive application of nitrogen fertilizer decreased the uptake of nitrogen, phosphorus, potassium. The utilization rate of nitrogen fertilizer was the highest with the amounts of applied N of 112.5 kg/hm². The nitrogen application rates had no significant effect on cotton fiber quality index. 【Conclusion】 Considering the yield, nitrogen utilization, nutrient uptake, distribution and utilization and fiber quality, the recommended amount of nitrogen fertilizer in cotton area of Yellow River Basin was 112.5-168.75 kg/hm².