Detailed Explanation of Key Points for Balanced Fertilization Technology in Cotton

I. Principles of Cotton Fertilization

1. Combined Application of Organic and Inorganic Fertilizers

Cotton production should be sustainable. Organic fertilizers have the characteristics of complete nutrients and stable, long-lasting fertilizer efficiency, and cannot be replaced by inorganic fertilizers. Even under conditions where the supply of inorganic fertilizers is relatively sufficient, the role of organic fertilizers should not be neglected. Only through the combined application of both can high and stable yields be achieved. Especially under the current situation of high chemical fertilizer prices, more attention should be paid to increasing the application of organic fertilizers.

2. Balanced Application of Major Elements and Trace Elements

Major elements refer to nitrogen, phosphorus and potassium; trace elements refer to boron, zinc, etc. The combined application of these two types of elements is beneficial for improving fertilizer use efficiency.

II. Balanced Fertilization Technology for Cotton

Balanced fertilization of cotton is based on the fertilizer requirements of cotton, the fertilizer supply performance of the soil and fertilizer effects. On the basis of applying organic fertilizers, it proposes the appropriate amounts, ratios and corresponding fertilization techniques for nitrogen, phosphorus, potassium and trace elements, in order to implement the optimal balanced nutrient plan and technology to obtain the best economic benefits of cotton production, while adhering to the combination of land use and land nurturing, and the combination of organic and inorganic, so that the available soil nutrients are in the best dynamic balance.

III. Suitable Fertilizer Amounts and Ratios for Cotton in Our County

Based on the general fertilization level in the cotton region along the river combined with the results of many years of experiments and demonstrations by our office, the suitable ratio of nitrogen, phosphorus and potassium for cotton in our county is 1:0.35~0.4:1. For a target yield of 100~120 kg of lint cotton per mu, the entire growth period requires 18~21 kg of nitrogen (N) per mu, equivalent to 40~15 kg of urea; 6~8 kg of phosphorus (P2O5), equivalent to 50 kg of superphosphate or 20 kg of ammonium phosphate; 15~20 kg of potassium (K20), equivalent to 25~35 kg of potassium chloride; plus 50 kg of cake fertilizer.

IV. Cotton Fertilization Methods

1. Base fertilizer. Where conditions permit, generally apply 20 dan of farmyard manure per mu plus 10~20 kg of decomposed cake fertilizer, 10 kg of urea, 50 kg of superphosphate or 20 kg of diammonium phosphate, 10 kg of potassium chloride, or an equivalent amount of NPK compound fertilizer (for soil with a high sand content, the amount of chemical fertilizer in the base fertilizer should be appropriately reduced to prevent loss), and 1~1.5 kg each of borax and zinc sulfate. Alternatively, a one-time application of 80~100 kg of cotton-specific formula slow/controlled-release fertilizer can be used. Fertilization timing: for reserved cotton rows or vacant stubble fields, apply 15~20 days before transplanting or 7~8 days before transplanting combined with land preparation and bed formation; for cotton transplanted after rapeseed harvest, apply within 5~7 days after transplanting is completed; fertilizer should be more than 15 cm away from cotton plants, with a fertilization depth of more than 15 cm; at transplanting, a small amount of compound fertilizer can be applied in the planting hole.

2. Bud stage. Generally, no additional chemical fertilizer is needed at the bud stage. If growth is poor, a small amount of quick-acting fertilizer can be supplementally applied. For cotton fields deficient in boron, spray 50 g of borax dissolved in 25~30 kg of water on the leaves at the bud stage.

3. Flower and boll fertilizer. Apply the first flower and boll fertilizer early. Generally apply 30~40 kg of cake fertilizer, about 10 kg of urea, and 10~15 kg of potassium chloride per mu. For film-mulched transplanted cotton, the plastic film must be removed at the end of June or beginning of July. At the early flowering stage, apply the first flower and boll fertilizer in a furrow opened in the middle of the small rows combined with intertillage; for open-field transplanted cotton, apply the first flower and boll fertilizer from the early flowering stage to the flowering period in early July. Spray boron fertilizer: for cotton fields deficient in boron, spray 100 g of borax dissolved in 50 kg of water on the leaves per mu at the flowering stage. Heavily apply the second flower and boll fertilizer. For film-mulched transplanted cotton, apply about 15 kg of urea by hole or furrow application in mid-to-late July; for open-field transplanted cotton, apply about 12 kg of urea by hole or furrow application per mu in late July. For cotton fields deficient in boron, spray 100 g of borax dissolved in 50 kg of water on the leaves in late July.

4. Top-covering fertilizer. Depending on growth conditions, apply 5~10 kg of urea per mu (especially for fields where cotton-specific formula slow/controlled-release fertilizer was applied as a one-time application), generally finishing before August 10.

5. Foliar topdressing. After mid-August, spray 0.5%~1.0% urea on the leaves (for cotton fields with excessive growth, add 0.3%~0.5% potassium dihydrogen phosphate), spraying once every 7-10 days for 3~4 consecutive times.