symptom. During the flowering and ringing period of cotton, the leaf color of the upper part of the main stem of cotton turns from pale yellow to dark green. Yellow spots appear in the green veins, then brown, and then the leaves shrink, brittle, reddish brown and fall off, cotton bolls are thin, easy to premature aging, analysis of cotton stem vascular end of the tube is not infected, and verticillium The end of the vascular stem of the cotton plant was yellowish brown.
Control method. Improve cotton farmers' awareness of increasing potassium fertilizer. Because the application of potassium fertilizer can not only accelerate the flower bud differentiation of cotton, reduce the detachment of buds, but also promote the respiration of cotton plants to nitrogen fertilizer, and increase the function and production stamina of cotton leaves.
Rational and scientific application of potash fertilizer. The absorption of potassium fertilizer in cotton during the whole growth period is generally less in the early stage, more in the middle and late stages, and the absorption of potassium fertilizer after flowering accounts for about 80% of the whole growth period. Therefore, each mu of cotton field should be applied about 12.5 kg of potash. The bud period is about 7.5 kg. In the middle and late stages, potassium fertilizer such as potassium dihydrogen phosphate can be sprayed in an appropriate amount, sprayed once every 7 to 10 days, and sprayed for about 3 times.
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