Do a good job of cotton management in July and August for a more secure bumper harvest

I. The importance of battling through July and August. The flowering and boll-setting stage is the longest stage in cotton's growth period and the time when natural resources such as light, heat and water are most abundant, which is very favorable for cotton growth and development. However, this period also has its unfavorable side: not only are natural disasters such as wind, hail, drought and waterlogging frequent, but pests and diseases also occur and cause serious damage. As the farming proverb says, "Cotton is a weed in the dog days; good can turn bad, and bad can turn good." Therefore, this period is the key period for securing a bumper cotton harvest, especially this year, when the cotton growth process is delayed by 7-10 days compared with previous years and the seedling condition is generally worse than in previous years. In this situation, according to the growth characteristics of cotton, making full use of natural advantages, overcoming unfavorable factors and strengthening cotton management is even more important for battling through July and August and securing a bumper harvest despite disasters.

II. Key points of cotton management during the flowering and boll-setting stage

1. Apply bud fertilizer steadily, apply flowering and boll fertilizer heavily and early, and apply topping fertilizer as a supplement. According to our association's rural service surveys, due to the effects of low temperature and cloudy and rainy weather, some cotton fields have still not flowered so far. For such cotton fields, bud fertilizer should be applied promptly. Bud fertilizer is generally applied per mu at 5-7.5 kg of urea, 50 kg of phosphate fertilizer or 15-20 kg of diammonium phosphate, plus 0.5-1 kg each of boron fertilizer and zinc fertilizer, applied in furrows in combination with intertillage and earthing up. For cotton fields that have entered the flowering stage, flowering and boll fertilizer should be applied early and heavily. Generally, flowering and boll fertilizer is applied per mu as a topdressing of 20 kg of urea (up to 30 kg for high-yield fields) and 15-20 kg of potassium fertilizer. When the amount applied at one time is relatively large, it can be divided into two applications: one at the early flowering stage and one at the peak flowering and boll-setting stage. Topping fertilizer is generally applied in late July to early August. Topping fertilizer should not be excessive or too late, so as to prevent excessive vegetative growth and delayed maturity. Before boll opening and after topping, for cotton fields lacking fertilizer, root-zone topdressing should be carried out with a 2% urea solution or a leaching solution of diammonium phosphate or compound fertilizer, once every 7 days for 3 consecutive sprays.

2. Carry out chemical regulation according to local conditions. Using mepiquat chloride for chemical regulation can not only shape an ideal cotton plant form and control plant height, but also adjust nutrient distribution in the cotton plant, prevent excessive aboveground growth, promote root development, and improve disease and pest resistance. Mepiquat chloride regulation should avoid excess and should follow the principle of small amounts applied multiple times according to local conditions. The general dosage per mu is: 0.3-0.5 g at the bud stage, 1-2 g at the early flowering stage, 3-4 g at the peak flowering and boll-setting stage, and 5-6 g 7 days after topping. Through chemical regulation, the plant height at the peak flowering stage should be controlled at 80-90 cm in the south, and after topping the plant height should be controlled at about 130 cm; in northern cotton areas, it should be controlled at about one meter.

3. Careful pruning and timely topping. Careful pruning is a traditional technique for increasing and stabilizing cotton yields and should continue to be used and improved. The topping time is generally around July 15, following the principle of not waiting for branches when the time comes and not waiting for the time when branches are ready. For cotton fields transplanted relatively late, topping can be done appropriately earlier to prevent late maturity. In the north, for simplified pruning cotton fields that retain leaf branches and for no-pruning cotton fields, the tips of leaf branches should be removed when 3 secondary leaf branches have grown from the leaf branches. The topping time for the main stem can be appropriately earlier than for careful pruning.

4. Do a good job of controlling major pests and diseases. After July, cotton mirids enter a period of overlapping generations and alternating occurrence, which is also the most difficult period to control. According to the habits of cotton mirids, control should be carried out during the nymph stage and early damage stage, using early morning or evening, and the policy should be to control thoroughly without leaving surviving insects. To achieve this requirement, good forecasting must be done, and control should be carried out when the rate of newly damaged plants at the growing tips reaches 3%-5%. For cotton fields with relatively severe occurrence, timely inspection should be carried out after control; if control is not thorough, continuous control should be carried out until it is complete. The specific pesticide for controlling cotton mirids is Jinkelingchun, followed by fipronil, chlorpyrifos, malathion, etc. The above pesticides also have relatively high control effects on cotton bollworm and other pests, so one pesticide can serve multiple purposes. Red spider mites occur severely after drought, so timely inspection and timely control are needed; the specific pesticide is abamectin. The peak occurrence of summer aphids is in mid-July, and the specific pesticides for control are acetamiprid, imidacloprid, pymetrozine, etc.

5. Strictly prevent explosive pests. The main explosive pests are whiteflies, beet armyworm, cotton looper, etc. The main occurrence and damage period of whiteflies is in August and September, and unified control should be carried out in the early occurrence stage. Effective pesticides are acetamiprid wettable powder, bifenthrin, abamectin, etc. The outbreak period of beet armyworm and cotton looper is in mid-to-late August. The main specific pesticides for control are emamectin benzoate, chlorfenapyr, abamectin, etc. Through forecasting, the key period before the 3rd instar should be seized for control.

6. Irrigate in drought and drain in waterlogging. When managing cotton in July and August, earthing up should be carried out in combination with intertillage, so that water can be drained in waterlogging and irrigation can be provided in drought, ensuring normal cotton growth.