Q&A on Key Technical Points for Cotton Late-Stage Management

1. When does cotton late-stage management begin?

Answer: Cotton field management after the end of the flowering and boll-setting stage is called cotton late-stage management. In China's Yellow River basin it generally begins in early September, and in the Yangtze River basin it generally begins in late August.

2. What is the main task of cotton late-stage management?

Answer: The boll-opening stage is the key period determining cotton fiber quality, so first of all the focus should be on preserving bolls, increasing boll weight and increasing lint percentage; secondly, the focus should be on protecting roots, preserving leaves, promoting early maturity and preventing premature senescence; thirdly, the contradiction must be resolved between a bumper harvest and rotten bolls from rainy weather, excessive vegetative growth and late maturity, and a high proportion of stiff-boll cotton.

3. What is the basic appearance of cotton in the late stage that combines high yield, early maturity and no premature senescence?

Answer: Red stalks and green leaves with good ventilation, green leaves with yellow veins and no excessive vegetative growth; clean and bright without shading, large bolls with thin shells and smooth leaf and lint development; double flowers visible after End of Heat, leaves gradually turning yellow after White Dew;

One harvest of cotton causes a batch of leaves to drop, and boll opening is complete around Frost's Descent. In a normal cotton field, half the bolls are required to open by National Day, and half the cotton leaves drop after mid-October. If after mid-October the cotton leaves grow more and more attractive, then green-skinned bolls and green stalks easily form, with excessive vegetative growth, late maturity and no high yield.

4. How should water and fertilizer management be handled in the cotton late stage?

In the cotton late stage the temperature drops and water demand gradually decreases; at this stage water demand accounts for 10%-20% of total water demand, and field capacity should be maintained at 60%, which is appropriate. When drought occurs at the early boll-opening stage, watering should be maintained, but the amount of water should not be too large, so as to avoid excessive vegetative growth and late maturity in the plants; generally only half a furrow of water needs to be applied. For cotton fields where improper management in the early and middle stages, or excessive water and fertilizer causing vigorous growth, has led to severe boll shedding in the middle and lower parts, or where autumn bolls are sparse, plants are tall, large and empty, and flower buds cluster again in the late stage with excessive vegetative growth, no additional fertilizer should be applied in the late stage. For generally well-managed insect-resistant cotton fields, the demand for potassium fertilizer is relatively sensitive, so sufficient potassium fertilizer should be applied when topdressing. Based on many years of experience, it has been found that when potassium deficiency symptoms appear in cotton fields, foliar topdressing once every 5 days has a relatively obvious effect. Application method: per mu, 2 liang of monopotassium phosphate + half a jin of potassium sulfate + 2 liang of urea, diluted in 60 jin of water for spraying. Spraying is best done after 4 p.m. For cotton fields with many bolls set in the middle and lower parts, or with fertilizer deficiency and premature senescence, liquid fertilizer should be sprayed as early as possible; the above application method may be used, or other liquid fertilizers may be sprayed, to promptly supplement the nutrients cotton needs, prevent premature senescence, increase boll setting in the upper part, increase boll weight and raise cotton yield.