Objective  The effects of different combined applications of nitrogen (N), phosphorus (P) and potassium (K) fertilizers on cotton growth, nutrient accumulation, yield and fertilizer utilization efficiency were compared to solve the serious problems of unbalanced fertilization and excessive chemical fertilizer usage in cotton fields in Shaya County, Aksu Prefecture, Xinjiang, and to reduce cotton fertilizer usage, to increase yield and improve fertilizer utilization efficiency in Shaya County.

  Method  The cotton of Shaya County was regarded as experiment material. In the case of fertilization treatment of N, P and K fertilizer dosage was a certain amount, and five treatments were set up: control (CK), N and P (NP), N and K (NK), P and K (PK) and N, P and K combined application (NPK). The response characteristics of biomass and nutrient accumulation of cotton in each growth period were systematically analyzed under the different conditions of combined applications of N, P and K, and the influence mechanism of combined applications of N, P and K fertilizers on cotton nutrient absorption, yield and fertilizer utilization efficiency was explored.

  Result  With the progression of cotton growth period, the biomass of the whole plant treated with different combined applications of N, P and K fertilizers appeared a gradually increasing trend, and the maximum value was distributed in "bolling period - boll opening period". In the cotton bud stage, N and P fertilizers were significantly correlated with the dry matter quality of plants. The accumulation of N nutrients in roots, reproductive organs and whole plants under NPK treatment showed an increasing trend, while that of the stem and leaf showed a trend of "increasing - decreasing", and the accumulation of N, P and K nutrients reached the maximum during the boll opening period. The yield of seed cotton under the NPK treatment was highly up to 4583 kg hm^-2, which is 5.92%, 9.93% and 11.10% higher than that of NP, NK and PK treatments, respectively. The fertilizer utilization efficiencies of N, P and K in the cotton field were 41.59%, 14.52% and 69.29%, respectively.

  Conclusion  When the N fertilizer usage is 300 kg hm^-2, the P fertilizer usage is 150 kg hm^-2, and the K fertilizer usage is 90 kg hm^-2, compared with the treatment of N, P and K, the NPK treatment can effectively promote the growth, development and nutrient absorption of cotton, and significantly improve cotton yield and fertilizer utilization efficiency, which has the best effect on cotton growth.