Key Field Management Techniques for Cotton During the Squaring and Flowering-Boll Stages

Management of cotton during the squaring and flowering-boll stages centers on regulating water and fertilizer, combined with measures such as intertillage, chemical regulation, and pruning. The promotion and control techniques should be applied reasonably, combining promotion with control, to achieve strong plants with steady growth, build a high-yield framework, increase boll setting, reduce shedding, and achieve a full set of three bolls.

I. Fertilizer and Water Management

During the squaring stage, cotton plants are required to grow steadily, so fertilizer application should be steady and skillful, with controlled use of nitrogen fertilizer. Cotton fields with medium to high fertility should not be fertilized further. If soil fertility is poor or the base fertilizer is insufficient, generally apply urea at 5-7 kg per 667 sq m. When cotton enters the flowering-boll stage, the growth of stems, branches, and leaves reaches its maximum, and at the same time a large number of squares appear, flowers open and bolls set, nutrient uptake reaches its peak, making this the critical period for fertilization. During this period, the amounts of nitrogen, phosphorus, and potassium absorbed by cotton plants all account for more than 60% of the entire growth period. On the basis of sufficient nitrogen and potassium fertilizer applied earlier, apply heavy nitrogen fertilizer, generally topdressing urea at 15-20 kg per 667 sq m. The topdressing time should be before the early flowering stage; for fields with poor soil fertility, weak plant growth, and early-maturing cotton, it can be appropriately advanced, with topdressing about 15 days before the flowering stage. For fertile fields with excessively vigorous plant growth, topdressing can be done when the plants have set the pre-summer bolls.

Topping-off fertilizer is key to preventing premature senescence in the late stage of cotton and achieving autumn bolls covering the top. For cotton fields showing signs of premature senescence, apply early and heavily; for vigorous growth, apply lightly or late. For insect-resistant cotton in the late stage, due to strong boll-setting per plant and reduced root function, foliar topdressing can be strengthened. For the premature senescence type, spray 0.2% urea aqueous solution; for the overly vegetative type, spray 0.4% potassium dihydrogen phosphate or 3% superphosphate extract; spray once every 7-10 days, with 3-4 consecutive sprays being appropriate.

The squaring stage of cotton coincides with relatively low rainfall in the Northern Xinjiang cotton region, while field water consumption is increasing daily. To build a good high-yield framework, irrigate when drought occurs. The flowering-boll stage is the period of greatest water demand for cotton plants. If water supply is insufficient, cotton plant growth and development will be seriously affected, increasing square and boll shedding. At the same time, without adequate water, fertilizer in the soil cannot exert its effect. Therefore, irrigate promptly to regulate fertilizer with water, promoting fertilizer decomposition and root absorption of nutrients. If rainfall is excessive, drain promptly to prevent waterlogging, reduce square and boll shedding, and lower the incidence of fusarium wilt and verticillium wilt.

II. Chemical Control Dosage

In chemical control, the principles of "early, light, frequent" and "light in the front, heavy in the rear" should be mastered. At the early squaring stage, use mepiquat chloride at 0.5-1.0 g per 667 sq m; at the full squaring stage, use 1-1.5 g. Chemical control should also be flexibly adjusted according to growth, soil type, and weather. At the early flowering stage, apply mepiquat chloride at 1.5-3 g per 667 sq m; at the full flowering stage, 3.0 g; about 7 days after topping, the dosage is 4-5 g.

III. Pruning and Topping

During the squaring stage, pruning is generally not done; the main task is to control excessive growth and achieve steady plant development. If excessive growth appears in patches, remove the "pant legs" early, removing all vegetative branches. During the flowering-boll stage, top promptly. In the Northern Xinjiang cotton region, the topping time is from June 25 to July 5, and the side shoots should be topped by July 10. Vegetative branches can be topped when 2-3 fruiting branches have grown before July 10. Topping too early causes a proliferation of superfluous buds, overly long fruiting branches, affecting ventilation and light penetration, and also limits the number of fruiting branches and fruiting sites, reducing effective squares and bolls, failing to fully utilize the effective growing season, and easily leading to premature senescence; topping too late fails to regulate nutrient distribution. The correct topping time should be determined based on cotton growth and the frost period.

IV. Pest and Disease Control

The squaring stage is when fusarium wilt begins to occur and gradually worsens, so prevention and treatment work should be done well. Fusarium wilt has 5 different symptom types: yellow vein type, yellowing type, sudden wilting type, purplish-red type, and stunting type. For mildly diseased cotton plants, use 50% carbendazim 500-fold solution, or thiophanate-methyl 800-fold solution; for severely diseased plants, use Mianbing Kexing, supplemented with potassium permanganate for root irrigation treatment.

For aphid control, use Shiyajing, imidacloprid, pymetrozine, etc.; for cotton leaf mite control, use abamectin, Saomanjing, etc.; for cotton thrips control, use Tianhui Chongqing, monocrotophos, etc.; for cotton bollworm control, use BT and NPV biological pesticides. The main disease during the flowering-boll stage is verticillium wilt, and the insect pests are the second and third generations of cotton bollworm, summer aphids, cotton leaf mites, etc. The main control methods refer to pest and disease control during the squaring stage.