Technical Points for Spraying Foliar Fertilizer on Cotton to Increase the Boll Setting Rate

This year, the summer-ripening crops in Haimen City were delayed in maturity due to climate effects, and after the summer harvest there was a continuous drought until mid-July, when it rained heavily for several consecutive days. This weather pattern of drought followed by rain was very unfavorable for the survival and growth of the already delayed transplanted cotton, and the growth process was delayed by about 10 days compared with normal years. To increase the formation speed of flower buds in the late stage of cotton and improve the boll setting rate, it is recommended to strengthen fertilizer management in the late stage by means of foliar spraying.

1. Combine pest control with proper timing of fertilizer application. Not every pest control treatment requires added fertilizer. Different types of nutrients such as nitrogen, phosphorus, potassium and trace elements should be applied alternately. The same nutrient should be sprayed once every 7-10 days, and different nutrients should be spaced 3-5 days apart. For example, apply nitrogen fertilizer the first time, phosphorus and potassium fertilizer the second time, and trace element foliar fertilizer the third time.

2. Select good varieties to ensure coordinated nutrients. Urea is an ideal nitrogen fertilizer for foliar spraying. In the late growth stage of cotton, spray a 0.5% urea aqueous solution until the leaves drip; for phosphorus and potassium fertilizer, potassium dihydrogen phosphate is suitable, with a concentration of 0.2%; trace element foliar fertilizer can effectively reduce nutrient deficiency symptoms in upper leaves and increase the boll setting rate. In addition, humic acid liquid fertilizer has the effect of promoting well-developed roots and robust plants, can enhance photosynthesis, regulate plant physiological functions, and promote plant growth and dry matter accumulation, thereby increasing yield and improving quality.

3. Adjust flexibly to improve photosynthetic efficiency. Foliar fertilization should be flexibly controlled according to the growth vigor and appearance of cotton. For cotton with weak growth, nitrogen fertilizer is generally the main choice, combined with phosphorus and potassium fertilizer; for average growth, nitrogen, phosphorus and potassium should be used together; for overly vigorous growth, phosphorus and potassium fertilizer should be the main choice, combined with chemical regulation, using 3-3.5 grams of pure mepiquat chloride per mu plus water for spraying. Trace element foliar fertilizer is suitable for all types of cotton fields, especially for plots with weak growth.