How to manage cotton during the flowering and boll-setting stage? Apply flowering and boll fertilizer heavily, use chemical regulation and pruning to prevent premature senescence

During the flowering and boll-setting stage of cotton, vegetative growth and reproductive growth proceed together, and this is the peak period of fertilizer and water demand throughout the whole growth period and the critical period for yield formation. This year, cotton fields had sufficient subsoil moisture and good seedling conditions. In the early stage there was a period of high temperature and drought, but after moderate rain fell generally on June 30, the drought was alleviated, which is favorable for flowering and boll setting. In management, it is necessary to adapt to local conditions and combine promotion with control, prevent high temperature and drought, autumn waterlogging, and pests and diseases, and strive for stable growth in July, tender growth in August, and no premature senescence in early September, so as to achieve "no excessive vegetative growth, no premature senescence, more bolls set, and fewer rotten bolls."

1. Apply flowering and boll fertilizer heavily, supplement foliar fertilizer to prevent premature senescence

The demand for fertilizer is greatest during the flowering and boll-setting stage, so flowering and boll fertilizer should be applied adequately and a top-covering fertilizer should be supplemented. For fields with sufficient soil fertility, good moisture, and robust cotton plants, a small amount can be topdressed at the full flowering stage or postponed, with 8-10 kg of urea applied per mu; for fields with insufficient base fertilizer, poor moisture, and weak growth, it should be applied early and heavily, preferably at the early flowering stage, with 10-15 kg of urea applied per mu; both types of fields should also be applied with 5-10 kg of potassium sulfate or potassium chloride. For vigorously growing fields with a daily growth amount exceeding 3 cm, topdressing should be postponed until 1-2 bolls are set and nitrogen fertilizer should be reduced; after topping, 5-7 kg of urea per mu should be supplemented as a top-covering fertilizer. Topdressing should mainly be done by hole application or band application, below 10 cm into the soil and 25-30 cm away from the cotton plants. Combined with pest control, spray a mixed solution of 0.2% potassium dihydrogen phosphate + 1% urea + 0.2% borax 2-3 times to reduce flower and boll shedding; from early July to early August, supplement foliar fertilizer well. Spray 1% urea for weak growth, and spray 0.2% potassium dihydrogen phosphate for robust fields, to prolong the functional period of green leaves, prevent premature senescence, and increase boll weight.

2. Combine irrigation and drainage, cultivate and earth up, and remove film in time

Rainfall during the flowering and boll-setting stage varies greatly from year to year, so both waterlogging and drought must be prevented. If there has been no rainfall for 10-15 days, the relative water content of the plow layer is below 60%, and at noon the leaves wilt, are small, thick, and dark green, and the fruiting branches extend slowly, timely small-water furrow irrigation should be carried out; flooding irrigation should be avoided. When there is much rain, drain water promptly to prevent water accumulation and oxygen deficiency that can cause root diseases and flower and boll shedding. Intertillage should be shallow rather than deep, 7-10 cm between rows and 5 cm between plants; for overly vigorous fields, deep intertillage can cut some lateral roots to control excessive growth. After watering or rainfall, carry out intertillage and loosening of the soil at suitable moisture to reduce humidity, suppress weeds, and prevent rotten bolls. For sandy soil and fields that have not yet closed canopy, deep intertillage and high earthing up can be carried out; for fields that have already closed canopy, deep intertillage should be avoided to prevent root damage; earth up to a height of 13-16 cm, ultimately lower than the first fruiting branch, and do not bury branches, damage branches, or touch flower buds. At the end of June or early July, combined with watering or after thorough rain, remove the film at suitable moisture, then immediately carry out intertillage and earthing up to promote roots to grow downward, resist drought, and prevent lodging. When drought and moisture deficiency occur, film should not be removed; after film removal, apply 300-500 kg of straw per mu as mulch to lower temperature, preserve moisture, and improve soil fertility.

3. Rational chemical regulation and fine pruning, keep a close watch on pest and disease control

For chemical regulation, observe the weather and the plants. Start when the daily growth amount of the main stem is 2.5 cm at the early flowering stage and 3 cm at the full flowering stage. For vigorously growing fields, at the early flowering stage use 1-1.5 g of mepiquat chloride per mu (or 5-10 mL of chlormequat) mixed with 30 kg of water; at the full flowering stage use 2-3 g of mepiquat chloride per mu or 8-15 mL of chlormequat mixed with 40-50 kg of water and spray evenly; for poor-growing fields, postpone application or reduce the dosage, generally using about 2 g of mepiquat chloride per mu or about 8 mL of chlormequat; for vigorously growing fields, 5 days after topping, use 4-5 g of mepiquat chloride per mu for one heavy regulation. Chemical regulation must not be carried out within 5 days before or after topping; regulate more in rainy conditions and less in drought. Pruning should adhere to "determine branches by density, determine timing by branches; when branches are sufficient, do not wait for time; when time is sufficient, do not wait for branches": at the early flowering stage, remove the growing points of the lower 3-4 fruiting branches; around July 15, remove those of the middle 4-5; in early August, remove the tips of the upper fruiting branches; for well-growing fields, when each plant has grown 13 fruiting branches, the group branches and the main stem tip can be topped all at once; for poor-growing fields, topping can be postponed but no later than the Beginning of Autumn, with July 25-30 being suitable. For fields with high water and fertilizer and low density, remove redundant buds along with topping; for densely shaded fields, remove old leaves in stages from bottom to top. At present, insect-resistant cotton is mainly grown, and generally no control is needed for the 2nd and 3rd generations of cotton bollworm, while the 4th generation should be controlled according to conditions, with emphasis on controlling aphids, mirids, and red spiders; adhere to prevention first, choose two pesticides with different active ingredients for mixed spraying and alternate use, do not increase the dosage at will, spray finely and evenly, ensure the leaf backs receive the pesticide, and do not miss any spraying.