How to manage cotton during the bud and boll stage? Strengthening management is key
Bud stage management: After cotton enters the bud stage, all regions should manage according to the seedlings, with classified management. For first-class cotton fields, where cotton plants have vigorous vegetative growth, reasonable regulation should be carried out to shape an ideal plant type and promote early boll setting, more bolls, and large bolls; for second-class cotton fields, promotion and control should be combined to encourage cotton plants to build a high-yield framework early; for third-class cotton fields, which develop late and grow weakly, the method of promoting both water and fertilizer should be adopted to encourage cotton seedlings to grow early.
Focus on the following aspects:
1. Grasp "four rush" management. For cotton fields interplanted in wheat fields, after harvesting wheat, promptly rush to water, rush to clear stubble, rush to topdress, and rush to control insects, providing a good environment for cotton seedling growth and development. The topdressing rate is generally about 5 kg of urea per mu; where base fertilizer is insufficient, 50 kg of cake fertilizer or 500-1000 kg of organic fertilizer can be topdressed; potassium-deficient plots can be topdressed with 10-20 kg of potassium sulfate. Focus on the control of cotton aphids, red spiders, and mirids.
2. Scientific fertilization. After cotton squaring, it enters a period of simultaneous vegetative growth and reproductive growth, while still mainly vegetative growth. Fertilization at the cotton bud stage must both meet the needs of cotton for growing and building a high-yield framework and prevent improper fertilization from causing excessive vegetative growth of cotton plants. Therefore, fertilization should be steady and skillful. According to the reality that cotton development is generally late this year, especially for second- and third-class cotton fields, it is necessary to start early, give priority to promotion, and combine promotion with control. Generally, 10-15 kg of standard nitrogen fertilizer is topdressed per mu. For cotton fields with poor soil fertility, insufficient base fertilizer, and weak cotton seedling growth, it should be applied appropriately earlier and more; for cotton with early development or sufficient seedling fertilizer and strong growth, it should be applied appropriately later, less, or not at all. Potassium-deficient cotton fields can be topdressed with 10-20 kg of potassium sulfate per mu.
3. Timely watering. Our province is often dry in late spring and early summer. Although the soil moisture in cotton fields is currently good, drought symptoms have appeared in some areas, so attention should be paid to watering to prevent drought. When the soil moisture content at 10-30 cm in cotton fields is less than 55%, water promptly, but each watering should not be too much; 20-30 cubic meters per mu is appropriate. After watering, promptly cultivate and loosen the soil to promote root penetration downward, thereby enhancing cotton's drought resistance in the later period.
4. Earthing up in cotton fields. After watering or thorough rain at the end of June and the beginning of July, plastic-film-mulched cotton fields can have the film removed and be earthed up to prevent lodging and also facilitate drainage and irrigation. Direct-seeded open-field and seedling-transplanted cotton fields can be earthed up directly. However, plastic-film-mulched cotton without irrigation conditions should not have the film removed and be earthed up before thorough rain.
5. Insect control. Focus on controlling the second generation of cotton bollworm, red spiders, and mirids. When the number of second-instar and older cotton bollworm larvae reaches more than 20 per 100 cotton plants, chemical control should be carried out promptly. For red spiders, when the rate of cotton seedlings with yellow spots damaged by mites is 20%-25%, control should be carried out promptly. The key to mirid control lies in "early." Generally, when there is 1 insect per 100 plants in the field, or when small black spots are found on young leaves or bracts of cotton plants, spraying for control should begin.
6. Chemical regulation. Mainly aimed at cotton fields with excessive growth and relatively high density, use 0.5-1 g of mepiquat chloride per mu, or 2-4 ml of chlormequat, diluted with 10-15 kg of water for spraying. After applying growth regulators to cotton fields, management must be strengthened, with attention to watering and fertilizing, so as to promote below and control above. Prevent the situation where, after using regulators, because cotton leaves are dark green, no topdressing or watering is done and management is relaxed, causing premature senescence and reduced yield. Flower and boll stage management The flower and boll stage is the key period determining cotton yield and quality. This period is when cotton needs the most nutrients in its entire life and is also a period when various natural disasters occur frequently. Strengthening management is very important for achieving a cotton harvest.
1. Apply heavy flower and boll fertilizer. According to the growth characteristics of insect-resistant cotton with many bolls set in the early stage, fertilization at the initial flowering stage is advocated, generally applying 15-20 kg of urea per mu. When fertilizing, it should be flexibly controlled according to cotton appearance and weather changes. For cotton fields with relatively little base fertilizer and bud fertilizer, relatively thin soil fertility, and weak cotton plant growth, flower and boll fertilizer should be applied early and heavily, so as to "fertilize at flowering for use at boll setting." At the same time, in early August, apply a supplementary top-covering fertilizer, 5 kg of urea per mu; for cotton fields with medium to high fertility, in order to strive for more bolls per plant, increase boll weight, and obtain higher yield, on the basis of topdressing at the initial flowering stage, 2.5-3 kg of urea per mu can be topdressed at the end of July and beginning of August; for cotton fields with a tendency toward premature senescence, topdress 5 kg of urea per mu; fertile cotton fields should only apply initial flowering fertilizer and apply little or no top-covering fertilizer. General cotton fields can combine insect control with foliar fertilization starting in mid-August. Spray 0.5%-1% urea solution, 2%-3% superphosphate solution, or 800-1000 times potassium dihydrogen phosphate solution, once a week, for three consecutive sprays.
2. Topping and pruning. Topping should be flexibly controlled according to cotton field density and variety characteristics. Generally, conventional insect-resistant cotton sown in spring has a density of 3000-4000 plants per mu, and each plant can retain 14-16 fruit branches; insect-resistant hybrid cotton has a density of 2000-2600 plants per mu, and each plant can retain 16-18 fruit branches; summer cotton has a density of 6000-8000 plants per mu, and each plant can retain 6-8 fruit branches. According to the principle of not waiting for branches when the time comes and not waiting for the time when branches come, the topping time for cotton fields with medium fertility is generally July 15-20, and late-developing cotton fields can be postponed to around July 25. The time for removing side shoots of cotton is generally before August 10. At the same time, promptly remove buds appearing after the Beginning of Autumn and flowers opening after White Dew, and remove ineffective buds to promote early maturity, high quality, and high yield of cotton.
3. Chemical regulation. Chemical regulation is an effective method for shaping a reasonable plant form. According to cotton growth and weather conditions, at the initial flowering stage, generally use 2-2.5 g of mepiquat chloride per mu, add 15-25 kg of water, and spray; 7-8 days after topping, according to cotton growth, generally use 3-5 g of mepiquat chloride per mu, dilute with 15-25 kg of water, and spray the top and side shoots of cotton plants. Chemical regulation must be flexibly controlled according to cotton growth and weather conditions. When the soil is short of water and cotton growth is inhibited, use less or not at all.
4. Integrated control of diseases and insect pests. In recent years, the occurrence of cotton Fusarium wilt, Verticillium wilt, red leaf stem blight, cotton leaf mites, tobacco whitefly, and mirids has worsened, causing losses to cotton. All regions should attach great importance, strengthen forecasting, and grasp the appropriate control period. In cotton bollworm control, focus on controlling the third generation. When there are 15 young larvae per 100 plants, chemical control measures should be taken. For cotton leaf mite control, acaricides such as Shamanwang and Chongmanke can be selected. For mirid control, polyester and organophosphorus pesticides can be applied alternately, and attention should be paid to protecting natural enemies. For cotton Fusarium wilt and Verticillium wilt, control should be based on prevention, and agents such as Guangkuling and Shiteling can be selected.