Technical Guidance on Late-Stage Management of Cotton Production (2016)
To ensure stable production and increased income for China's cotton this year, the Cotton Expert Steering Group of the Ministry of Agriculture has put forward technical guidance for late-stage management in the three major cotton regions, based on production conditions and climate characteristics in different cotton areas.
Northwest Inland Cotton Region
Late August to October is the key period for boll formation and growth. In view of the current overall late development of cotton in northern Xinjiang, the relatively severe boll disease in southern Xinjiang, and problems such as premature senescence and delayed maturity with excessive vegetative growth that are prone to occur later in the season, the following guidance is proposed.
Cotton field management: Strengthen fertilizer and water management in the middle and late stages, ensure 2-3 drip irrigations, with a drip irrigation volume of 20-30 cubic meters per mu, and apply urea at 3 kg/mu as a top dressing during drip irrigation. According to leaf conditions, the last watering may appropriately include drip-applied urea or clear water. For cotton fields with premature senescence, irrigation must be ensured, delaying the stopping of watering until the end of August or early September, and spraying a foliar fertilizer solution of urea or potassium dihydrogen phosphate once every 7-10 days for 1-2 consecutive applications. For cotton fields with delayed maturity and excessive vegetative growth, measures such as manual pruning and pushing plants together into ridges can be adopted, with timely application of ethephon for ripening.
Pest and disease control: In the middle and late stages of cotton field growth, cotton bollworm, aphids, red spider mites, and others occur frequently. For cotton fields with relatively severe damage, pesticides should be applied promptly, with unified spray control. For cotton bollworm, pesticides with little killing effect on natural enemies (such as Cypermethrin, etc.) should be selected; for red spider mites, specialized acaricides, etc. may be selected. For cotton fields with relatively severe boll disease, sprays such as carbendazim, chlorothalonil, and thiophanate-methyl should be used for control.
Scientific harvesting: For machine-picked cotton fields, defoliants should be scientifically selected and applied at an appropriate amount according to cotton field growth, cotton variety, and population density. Spraying should be carried out when the top bolls of the cotton are basically mature, more than 80% of bolls have reached 45 days or more, and the temperature is stable at 18-20°C. Defoliation and ripening agents must be completely sprayed 18-25 days before harvest. When the defoliation rate in the cotton field is above 90% and the boll opening rate is above 95%, mechanical harvesting can proceed. Hand-picked cotton must be harvested by grade according to standards, and the mixing of "three types of foreign fibers" into seed cotton must be strictly controlled.
Yellow River Basin Cotton Region
Since late July, the Yellow River Basin cotton region has repeatedly suffered heavy rainfall and extreme high temperatures. Some cotton fields show signs of excessive vegetative growth, square and boll shedding, and premature senescence. In view of the current cotton growth, the focus should be on increasing the setting of early autumn bolls and preventing premature senescence, and late-stage cotton field management should be effectively carried out.
Scientific management: Top dressing. For cotton fields showing premature senescence due to fertilizer deficiency, a solution of 3% urea plus 0.5% potassium dihydrogen phosphate should be sprayed on the leaves 2-4 times, with an interval of about 7 days each time. Water control. For drought-affected cotton fields, timely irrigation should be carried out. If autumn waterlogging occurs, field ditches should be further cleared and dredged to ensure smooth drainage. Pruning. Tip the side branches early to promote the setting of more early autumn bolls. For vigorously growing cotton fields, late-season cotton fields, and cotton fields affected by cloudy and rainy weather in autumn, old leaves should be removed promptly and empty branches pruned off.
Pest and weed control: Increase efforts to control pests in cotton fields such as planthoppers, cotton mirids, cotton leafworms, and beet armyworms, carry out unified control, and reduce the probability of large-scale pest and disease outbreaks in cotton fields caused by factors such as excessive vegetative growth or delayed maturity with excessive vegetative growth. Tall weeds and malignant weeds such as dodder should be removed promptly, and plants should be pushed together into ridges to increase field ventilation and light penetration.
Chemical regulation and harvesting: Chemical regulation. For late-maturing cotton fields and cotton fields requiring earlier rotation, ethephon should be sprayed for ripening according to weather and growth conditions. The spraying requirements are a boll stage of more than 45 days and a temperature above 20°C, with spraying time 20 days before the first frost. For machine-picked cotton demonstration fields, chemical regulation should be the focus according to weather and growth conditions, with timely use of mepiquat chloride for regulation, and defoliation and ripening should be properly carried out. Harvesting. Normal cotton bolls are best harvested 5-7 days after boll opening. Concentrated harvesting may be carried out 2-4 times according to boll-opening conditions. During harvesting, drying, packaging, and storage, attention should be paid to the color of seed cotton, and the mixing of "three types of foreign fibers" must be strictly controlled to ensure the quality of raw cotton.
Yangtze River Basin Cotton Region
In the Yangtze River Basin cotton region, severe weather such as heavy rain and high temperatures occurred repeatedly during the middle stage of cotton growth, and some cotton fields show a trend of premature senescence. All localities should make full use of the favorable climatic conditions of abundant sunlight and suitable temperatures in the late production stage, strengthen production guidance, and set more autumn bolls to reduce the impact of adverse weather on cotton yield and quality.
Top dressing and pruning: Top dressing. From late August to late September, use 0.3% potassium dihydrogen phosphate for foliar top dressing, spraying once every week. For potassium-deficient and boron-deficient cotton fields, apply potassium fertilizer and boron fertilizer promptly to supplement late-stage nutrients and prevent square shedding and premature senescence. Pruning. Promptly remove ineffective fruit branches, old leaves in the middle and lower parts, and superfluous buds to enhance ventilation and light penetration, increase the boll-setting rate and boll weight in the upper part of the cotton plant, and prevent boll rot.
Disaster prevention and harm reduction: All localities should prepare disaster response and relief plans, dredge the three ditches inside and outside cotton fields in advance, and promptly drain accumulated water from cotton fields when waterlogging occurs. If lodging is caused by typhoons, the cotton plants should be promptly righted, and soil should be loosened and hilled up in a timely manner to improve air permeability in the cotton field. Closely monitor the occurrence of pests such as the fourth-generation cotton bollworm, red spider mites, cotton mirids, and tobacco whiteflies, and apply pesticides promptly for control according to pest conditions.
Ripening and harvesting: From late September to mid-October, when more than 80% of cotton bolls have reached 45 days, choose a sunny day with a temperature above 20°C and spray ethephon for ripening. It is recommended to carry out two applications: the first on the middle and lower parts of the cotton plant, and the second on the upper part of the cotton plant one week later. For cotton fields with late sowing and late development, many autumn bolls, and delayed maturity with excessive vegetative growth, or cotton fields that encounter low temperature, cloudy and rainy weather, and insufficient sunlight in the later stage and cannot open and fluff normally, ethephon may be sprayed to promote faster boll maturation. In processes such as seed cotton harvesting, drying, and packaging, grading by harvest, drying, storage, and sale should be maintained to prevent the mixing of "three types of foreign fibers" and other foreign fibers.
Cotton Expert Steering Group of the Ministry of Agriculture (August 2016)