Detailed Explanation of Current Field Management Measures for Cotton
Recently, our region has experienced consecutive moderate to heavy rain, with local torrential rain, causing waterlogging in some cotton fields. Currently, cotton is about to enter the flowering and boll-setting stage. Because waterlogging accelerates the aging of cotton roots, it will affect normal flowering and boll-setting, resulting in reduced cotton yield and quality. Therefore, the following management measures should be taken to ensure a bumper cotton harvest.
1. Drain water promptly. Use every possible method to drain the waterlogged cotton fields as soon as possible, ensure the cotton fields dry out and are aerated, and strive as much as possible to restore normal root growth and promote flowering and boll-setting.
2. Topdress to promote growth. Once it is possible to enter the fields, farmers should topdress promptly according to cotton growth, the amount of basal fertilizer applied, soil fertility, and other conditions. Generally, per mu, 7.5-10 kg of urea plus 5 kg of potassium chloride, or 15 kg of cotton-specific fertilizer (a topdressing-type compound fertilizer with a total nitrogen and potassium content greater than 40%), may be applied. Carry out the second topdressing before August 10, applying 5 kg of urea per mu.
3. Break the plastic film. When conditions permit, break the plastic film, that is, cut it open from the middle and remove it as much as possible, to speed up drying out and avoid high temperatures after rain accelerating cotton root rot.
4. Rational pruning and chemical regulation. Use mepiquat chloride promptly to control excessive vegetative growth of cotton and prevent physiological flower and boll shedding caused by a closed canopy under high temperature and high humidity conditions. Apply about once every 10 days, and by August 10, it may be used 3-4 times. The first application rate is 1.5 g per mu, and each subsequent application increases by 0.5-1 g. Generally, ensure 12-15 fruiting branches are retained per plant, and top the plants around July 20; depending on plant growth, this may be completed by July 25. Pruning the group tips should be completed before August 10, and superfluous buds should be removed as appropriate.
5. Timely control of pests and diseases. Spray pesticide about once every 10 days to control cotton bollworm, cotton mirids, and aphids. Commonly used pesticides are: malathion, beta-cypermethrin, acetamiprid, BT emulsion, etc. To improve control effectiveness, alternating use of the above pesticides or mixing two pesticides is recommended. During control, focus on cotton tips and fruiting branch tips, spraying from the outer area toward the center. Spraying should be done before 9 a.m. and after 5 p.m. Where conditions permit, carry out unified prevention and unified control.
6. Foliar topdressing to prevent premature senescence. After mid-August, the ability of cotton roots to absorb fertilizer has gradually declined. Foliar fertilizer application can supplement the nutrients needed for cotton boll development and is an effective measure to increase boll weight and improve yield and quality. When used properly, it can increase yield by about 7%. Specifically: use 500 g of urea and 200 g of monopotassium phosphate per mu, mix with 25 kg of water, and spray evenly on the leaves. At the same time, mix with fungicides such as carbendazim to prevent rotten bolls and boll diseases. Spray once every 7 days, for 2-3 consecutive sprays.