Foliar feeding of cotton at the late stage is highly effective, and growers should pay attention to it

In the late growth stage of cotton, the root system's ability to absorb nutrients declines markedly. At this time, spraying foliar fertilizer to supplement nutrition has the effects of preventing premature senescence, preventing diseases, promoting large bolls, promoting early maturity and pursuing high quality, with remarkable effects in increasing yield and income.

1. Spray nitrogen fertilizer to prevent premature senescence: In the late stage of cotton, foliar spraying of nitrogen nutrition can keep cotton leaves green, enhance photosynthesis, and prevent nitrogen-loss premature senescence. Mixing nitrogen fertilizer with "regulator 802" makes the effect of enhancing cotton's late growth vigor more obvious and the yield-increasing effect better. From late August to early September, spray a mixed solution of 100-fold urea solution and 4000-fold "regulator 802" solution, spraying once every 5 days to 7 days, for 2 to 3 consecutive sprayings, with 75 kg of fertilizer solution per mu each time.

2. Spray potassium fertilizer to prevent diseases: When cotton lacks potassium, red leaf stem blight (wilt disease) is likely to occur during the flowering and boll-setting stage. Cotton leaves turn red or yellow, become thick, shrunken and brittle, and finally fall off, causing premature senescence of the cotton plant and serious yield reduction. While preventing drought, foliar spraying of potassium can reduce or inhibit the disease. Spray on the leaves a 0.3% potassium dihydrogen phosphate solution, a 2% potassium nitrate solution, a 1% potassium chloride solution, or a filtrate of 5% plant ash soaked (for 24 hours), spraying once every 7 days to 10 days, for 2 to 3 consecutive sprayings. For cotton fields where red leaf stem blight caused by potassium deficiency has already occurred, promptly spray on the leaves a 3% potassium nitrate solution, or a mixed solution of 0.3% potassium dihydrogen phosphate and 100-fold urea, spraying once about every 5 days, for 3 consecutive sprayings, which can quickly turn the cotton leaves green again. Spray 75 kg of fertilizer solution per mu each time, and be careful to wet the whole plant.

3. Spray phosphorus fertilizer to promote early maturity: Spraying phosphorus fertilizer in the late stage of cotton can make the seeds plump, increase boll weight and advance boll opening. Generally starting from late August, use 75 kg per mu each time of a filtrate of 2% superphosphate soaked (for 24 hours, stirring frequently); a 0.3% potassium dihydrogen phosphate solution can also be sprayed in combination with potassium supplementation.

4. Spray boron fertilizer to promote large bolls: When cotton lacks boron, side branches increase, fruit branch node positions are high, leaves become thick, and buds and flowers are prone to shedding, resulting in "buds but no flowers" or "flowers but no bolls", with few flowers, sparse bolls and low yield. Timely spraying of boron fertilizer can reduce flower and boll shedding and help set more bolls and larger bolls. Generally starting from boll setting, spray once every 15 days, for 2 to 3 consecutive sprayings, with 75 kg per mu each time of a 0.2% borax solution. Adding 0.5% urea when spraying boron gives a better effect. First dissolve the borax with a small amount of warm water, then dilute with cool water before spraying.

5. Spray zinc fertilizer to pursue high quality: Cotton is a zinc-sensitive crop. In recent years, as the application rates of nitrogen and phosphorus fertilizers in cotton fields have increased, the ratio of major elements to the trace element zinc has become imbalanced. Available zinc in the soil cannot be replenished in time, affecting cotton growth and development and limiting improvements in cotton yield and quality. Increasing zinc fertilizer application is beneficial to chlorophyll synthesis and growth, can promote cotton's absorption of nutrients, coordinate nutrient transport and enhance photosynthesis. Spraying zinc fertilizer on the leaves during the flowering and boll-setting stage of cotton can increase outer bolls, extend the life of functional leaves, increase lint percentage, raise yield and improve quality. Spray a 0.2% zinc sulfate solution on the leaves, generally for 2 to 3 sprayings, with 75 kg of fertilizer solution per mu each time. Foliar fertilizer should preferably be sprayed before 9 a.m. or after 5 p.m. on sunny days, to prolong the moist time of the fertilizer solution on the leaves and facilitate leaf absorption. Spray finely and evenly, with special attention to spraying the underside of cotton leaves, to promote absorption and enhance fertilizer efficiency. To save steps and give play to the combined effects of various nutrient elements, the above fertilizers can be mixed according to specific conditions, and can also be mixed with pesticides in combination with pest and disease control, so as to achieve "one spraying, multiple effects". Foliar fertilizer should not be mixed with alkaline pesticides, plant ash should not be mixed with other foliar fertilizers that are incompatible with alkalinity, and phosphorus fertilizer should not be mixed with zinc fertilizer.