Abstract: In order to optimize the application amount of phosphorus fertilizer in cotton and ensure the balance of phosphorus, the Logistic model was selected to analyze the phosphorus accumulation in different growth stages of cotton, and then the exponential model and linear model were used to analyze the relationship between phosphorus application amount and soil available phosphorus content. Based on the fertilizer effect function method, a linear plus platform mathematical model was constructed to simulate the relationship between phosphorus fertilizer application amount and cotton yield. On this basis, the optimum fertilization amount was determined by the nutrient balance method. The results showed that as the application of phosphorus fertilizer gradually increased, the yield of cotton also increased accordingly. When the application amount of phosphorus fertilizer was 83.99 kg/hm², the yield of seed cotton reached the highest level, which was 6 410.784 kg/hm². By optimizing the fertilization strategy, the phosphorus input of cotton was determined to be 21.98 mg/kg, and the corresponding phosphorus fertilizer application amount （P₂O₅） was 82.64 kg/hm², which could not only ensure the cotton yield, but also ensure the balance between the acquisition and expenditure of phosphorus.

Key words: cotton, phosphate fertilizer, application amount, phosphorus nutrient balance, mathematical model, fertilizer effect function method