What are the management techniques for cotton during the boll-opening stage?
After cotton enters the boll-opening stage, both vegetative growth and reproductive growth gradually slow down, the root system's absorption capacity weakens, and dry matter accumulation decreases. In the early boll-opening stage, summer bolls gradually mature, and autumn bolls are growing. From the perspective of individual plant development, in high-yield cotton fields, the upper fruiting branches of the plant extend horizontally, with a length of 20-30 cm, 3-4 squares present, large squares and a high boll-setting rate, and leaf color beginning to fade. In the early boll-opening stage, the cotton plant meets the requirement of "green leaves holding white lint, with both flowers visible above and below."
The main tasks of management during the boll-opening stage: first, create good environmental conditions for normal boll opening and promote early maturity; second, protect the roots and leaves and prevent premature senescence.
1. Strengthen water and fertilizer management. Drought in cotton fields will affect boll weight, so irrigation should be done in a timely manner. For cotton fields with insufficient nitrogen fertilizer and weak growth, a 500-fold urea solution can be sprayed on the leaves; for normal cotton fields, 300-500-fold monopotassium phosphate can be sprayed. Generally, spray once every 7-10 days, for 3-4 consecutive sprays. If there is a lot of standing water in the cotton field, drain it promptly.
2. Pruning and pushing rows together. In high-yield cotton fields, during this period, superfluous buds should still be removed promptly and old leaves removed. For cotton fields with excessive vegetative growth in the later stage, rows can be pushed together, that is, bringing two adjacent rows of cotton plants together into a splayed shape. After 5-7 days, push them apart again to both sides. In this way, both sides of each row of cotton and the ground between rows can receive sufficient sunlight successively, which promotes cotton boll maturity and boll opening and reduces rotten bolls.
3. Give equal importance to pest control and disease prevention. Pests during the boll-opening stage are mainly sudden pests such as the fourth-generation cotton bollworm, cotton semilooper, and beet armyworm. Timely inspection should be carried out, and control should focus on the peak hatching period, eliminating them before the third instar; in addition, there are whiteflies, red spider mites, thrips, autumn aphids, and others, which should be controlled promptly. Diseases are mainly rotten bolls caused by boll blight and others, which can be controlled with mancozeb. In the later stage, pay attention to preventing the spread of yellow wilt and Fusarium wilt.
4. Do a good job at the cotton harvesting stage. (1) Harvest in a timely manner. Generally, 7 days after cotton bolls crack, fiber quality is best, so harvesting once every 7-10 days is best. Too early affects the grade, and too late makes the cotton fiber prone to oxidation, becoming brittle and coarse, reducing strength. (2) Strictly implement "five separations, four cleans, two no-harvests, one prevention." "Five separations" means different varieties, or seed cotton, good cotton, inferior cotton, rigid and rotten cotton, pre-frost cotton, and post-frost cotton of the same variety, are separately harvested, separately sun-dried, separately stored, separately delivered (sold), and separately ginned. "Four cleans" means the cotton on the plant is fully harvested, the lint in the cotton bolls is fully picked, the cotton on the ground is fully gathered, and the leaf tips on the lint are fully removed. "Two no-harvests" means immature cotton is not harvested, and cotton with dew is not harvested. "One prevention" means adopting multiple measures to strictly prevent three types of foreign fibers from mixing into raw cotton.
Wang Yanna, Agriculture and Animal Husbandry Bureau of Handan County