From August 16 to August 20, the city experienced normal heavy rainfall, with accumulations ranging from 50 to 110 mm. Lucheng recorded the highest rainfall at 103 mm, which led to waterlogging in some cotton fields, affecting cotton growth to a certain extent. In response, cotton farmers should focus on post-rain field management to prevent early decline, reduce boll rot, and control diseases and pests, ensuring healthy boll development. The following measures are recommended:
I. Drainage and Anti-Lodging
During August and September, cotton plants are in their critical growth phase. After heavy rain, it's essential to promptly drain standing water from the fields to avoid root damage, yellowing leaves, and root rot. Even if there is no visible water accumulation, in clay soils where waterlogging occurs, farmers should dig drainage ditches along the main rows to reduce surface moisture and improve the growing environment. Timely soil cultivation after heavy rain is also crucial to prevent lodging.
II. Pruning and Managing Bolls
Excessive foliage can lead to poor air circulation and cause lower bolls to rot. After the "Liu Qiu" period, it’s important to remove excess branches, flowers, axillary buds, and yellow or old leaves to enhance light penetration and airflow, reducing the occurrence of bad bolls. For bolls that have been on the plant for over 40 days and show signs of discoloration, yellowing, or dark spots, they should be picked promptly. Soaking the seeds in a 1% ethephon solution and drying them can help achieve better boll opening.
III. Foliar Fertilization to Prevent Premature Aging
As cotton enters its late growth stage, root activity declines, reducing nutrient absorption. To prevent premature aging, foliar applications are more effective. Farmers can spray 0.2% potassium dihydrogen phosphate or a mixture of 2% potassium chloride, 2% superphosphate leachate, and 1% urea solution at a rate of 50–60 kg per acre. Apply every 7 days, up to three times. This helps delay aging, increase boll weight, and promote the formation of autumn peaches, especially in fields with limited water and nutrients. Spraying should be done in the late afternoon or on cloudy days for best results.
IV. Pest and Disease Control
Continuous rain and low temperatures create favorable conditions for diseases like red stem blight, brown wilt, and boll rot, as well as pests such as bollworms, red bollworms, cutworms, and whiteflies. For red stem blight, apply potassium dihydrogen phosphate solution early. For brown wilt and boll rot, use solutions like 30% hymexazol (1000x), 80% bicinchonate (1000x), or 70% thiophanate-methyl (1000x). For pests, apply 20% methomyl EC (1500x) or 2.5% kungfu emulsion (1000x). For whiteflies, use yellow sticky traps or spray 10% imidacloprid (1000x) or 1.8% avermectin (1500x).
V. Ethephon Application to Promote Bolling
For late-maturing or autumn peach-dominated fields, timely application of ethephon can help accelerate boll maturation and improve yield and quality. It should be applied before the first frost. Use 40% ethephon at 150–200 ml per mu mixed with 50 kg of water. Focus on upper late-season bolls to encourage early maturity and reduce boll damage. Avoid mixing with alkaline pesticides to ensure effectiveness. Apply on sunny days when daily temperatures exceed 20°C.
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