First, let's explore the factors that can lead to boll shedding in cotton plants:
1. Physiological Disorders: Environmental and internal plant conditions play a major role. Insufficient light, especially in densely packed cotton fields, leads to reduced photosynthesis, which limits the supply of essential nutrients and causes premature boll drop. Temperature also plays a key role—when daily average temperatures fall below 20°C or rise above 32°C, it can increase boll shedding. Excessive soil moisture can similarly trigger this issue. Additionally, improper nutrient management, such as insufficient fertilizer application, poor timing, or imbalanced nutrient ratios, can further contribute to boll loss.
2. Pest and Disease Infestations: Several pests and diseases can directly damage flowers, buds, and bolls, leading to significant yield losses. For example, cotton bollworms and aphids can weaken the plant's structure and reduce its ability to retain bolls. Fungal and bacterial diseases can also interfere with normal physiological processes, making the plant more vulnerable to boll shedding.
3. Mechanical Damage: Physical damage caused by human activities, animals, or farm equipment can harm the plant and cause bolls to fall prematurely. Natural disasters like strong winds or hail can also have similar effects, especially in unprotected fields.
Now, let's look at ways to reduce boll shedding:
1. Pruning and Field Management: Timely and proper pruning helps improve light penetration and air circulation in the field. Cotton topping should follow the principle of “cutting when needed and removing branches as required.†In dense areas, it’s important to remove empty branches and thin out old leaves to promote better growth and reduce boll drop.
2. Growth Regulation: For overgrown or vigorously growing cotton, careful control is necessary. Light drought or excessive growth may require minimal intervention, while heavy rainfall or overgrowth may call for increased chemical controls to manage plant development effectively.
3. Fertilization and Irrigation: Proper fertilization is crucial. In early growth stages, apply 2–3 kg of urea per acre after the boll setting period. For weak or thin cotton fields, applying 3–5 kg of urea during the bud stage can help strengthen the plants. If organic fertilizer or potassium is lacking, consider using 25 kg of cake fertilizer and 5 kg of potassium sulfate or chloride per mu. Watering should be done when soil moisture drops to around 17%, or when plants show signs of stress like dark leaves and more than two-thirds of the stems turning red. During flowering and boll formation, cotton requires the most water and nutrients. Fields with high fertility can receive top-dressing at full bloom, while weaker fields should be fertilized earlier and more frequently.
4. Pest and Disease Control: Effective pest management is essential. For cotton bollworms, use 20% methomyl diluted at 1000 times during egg-laying periods, and 28% emamectin benzoate or 25% chlorfenapyr at 1000 times during larval stages. For aphids, treat when infestation reaches 5%. Early detection and treatment of fungal or bacterial diseases with appropriate fungicides can significantly reduce boll loss caused by these issues.
By addressing these factors and implementing proper agricultural practices, farmers can minimize boll shedding and improve overall yield and quality.
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