Detailed Explanation of Key Points of High-Yield Fertilization Technology for Cotton

Fertilization is the most important and active link in cotton production. In order to obtain high cotton yields, scientific fertilization must be achieved. In villages such as Diandong and Sunwan in Tongshan County, Jiangsu Province, the lint cotton yield per unit area has stably exceeded 1500 kg/ha for more than ten consecutive years. According to surveys, the author summarizes their main experience in fertilization into 3 words, namely "sufficient, early, complete."

1 "Sufficient"

Sufficient fertilizer is the foundation of high yield. That is, determine the target yield according to production conditions and management level, and determine sufficient fertilization amount according to the target yield. According to the experience of the above-mentioned high-yield units, to obtain a lint cotton yield index of 1500 kg/ha, the nitrogen fertilizer application rate per hectare should be no less than 375 kg (referring to pure nitrogen). According to the survey results of fertilization amounts in Sunwan Village, the average lint cotton yield was 1410 kg/ha with an average of 301.8 kg of pure nitrogen applied per hectare; the lint cotton yield was 1672.5 kg/ha with an average of 381 kg of pure nitrogen applied per hectare. The reason for applying sufficient fertilizer is that there is a large difference between the amount of fertilizer applied and crop absorption. According to surveys, the utilization rate of ammonium bicarbonate in the current year was 44.5% in two-mixed soil, 52.1% in silt soil, and only 25.2% in sandy soil. Therefore, if the relationship between utilization rate and fertilization amount is not considered, insufficient fertilization will restrict the increase in yield. However, if too much fertilizer is added, the economic cost of fertilizer must also be considered, so blind input cannot be used. According to surveys at several high-yield points, within a certain range of fertilization amount, each additional 0.5 kg of urea applied can increase lint cotton yield by 0.75-1 kg, increasing output value by about 15 yuan, which is 10 times the cost of the fertilizer applied. Therefore, increasing the amount of fertilizer applied should determine the appropriate amount of fertilizer input according to soil texture, production conditions, target yield, and the economic benefits of input and output. Generally, when the lint cotton yield per unit area reaches more than 375 kg/ha, sandy soil should increase the pure nitrogen application rate by 45-60 kg, and clayey soil can reduce the pure nitrogen application rate by 30-45 kg; when the lint cotton yield per unit area is above 1200 kg/ha, loamy soil should apply about 300 kg of nitrogen, sandy soil should increase the pure nitrogen application rate by 30-45 kg, and clayey soil should reduce the pure nitrogen application rate by 30-45 kg.

2 "Early"

With the increase in fertilization amount, fertilization methods should also be improved accordingly. The experience of high-yield units is: appropriately advance the fertilization time, that is, apply 40%-50% of the fertilizer in the early stage of cotton growth, to ensure sufficient fertilizer promotes seedlings and early and stable growth at the bud stage. For example, in the fertilization of wheat-intercropped cotton in Sunwan Village, the method is: on the basis of applying 22,500 kg of farmyard manure and 750 kg of superphosphate per hectare as base fertilizer, the topdressing is advanced to before wheat harvest (bud stage), applying 300 kg of urea per hectare, accounting for 36.4% of the total annual urea topdressing amount; for the flowering and boll fertilizer, 375 kg of urea per hectare is applied, divided into 2 applications at early flowering and full flowering, accounting for 45.5% of the total annual urea topdressing amount; for the topping fertilizer, 300 kg of urea per hectare is applied, accounting for 18.1% of the total annual urea topdressing amount. This method of fertilizer management is mainly based on promoting early development with fertilizer, taking into account both the weak seedlings in the early stage of wheat-intercropped cotton and providing sufficient fertilizer supply during the large boll-setting period in the middle and late stages, preventing premature aging due to fertilizer deficiency, and ensuring early and stable growth of cotton.

3 "Complete"

That is, in the structure of fertilization elements, nitrogen, phosphorus, and potassium must be applied in combination. According to soil nutrient content status, promote formula fertilization, and change the unreasonable fertilization method of "emphasizing nitrogen and neglecting phosphorus and potassium" in previous years. For example, in many places in the past, due to a single fertilizer variety, potassium deficiency symptoms were obvious, causing large areas of leaf disease and red leaf stem blight. Even after applying a large amount of single nitrogen fertilizer, the effect was still not obvious. These are directly related to soil potassium deficiency. According to the 2004 Mengzhuang experiment, cotton applied with 225 kg of potassium sulfate per hectare had 29.1 bolls per plant, 4.7 more bolls than cotton without potassium sulfate, and could increase lint cotton by 163.5 kg per hectare, increasing yield by 14.6%, increasing economic benefits by 2940 yuan, and after deducting costs, net increase in benefits by 1800 yuan; according to statistics from multi-point experiments in Zhangji Town in 2005, for every additional 0.5 kg of potassium fertilizer invested in cotton fields, an average increase of 0.73 kg of lint cotton could be achieved. Therefore, while applying sufficient nitrogen fertilizer, increasing potassium fertilizer is an important measure that cannot be ignored for high cotton yields.

4 Conclusion

Based on the many years of high-yield fertilization experience in Zhangji Town, Tongshan County, when the lint cotton yield per unit area is about 1500 kg/ha, the fertilization standard is: apply 375-450 kg of pure nitrogen, 150-180 kg of phosphorus pentoxide, and 120-150 kg of potassium oxide per hectare, plus 15,000-22,500 kg of farmyard manure. Such a fertilization amount can basically meet the nutrient requirements for the above yield index.