In recent weeks, we have visited cotton fields in Hebei, Shandong, Jiangsu, Hubei, and Henan. Since the emergence of this year’s cotton crop, prolonged rainy weather, lower temperatures, reduced sunlight, and wind-related damage have significantly slowed down the growth of seedlings. According to field surveys conducted as of June 5, the average height of cotton seedlings is 4.4 cm shorter than the same period last year, with 1.8 fewer leaves per plant. The budding stage has also been delayed by 5–7 days compared to previous years. Given these conditions, it's more critical than ever to implement effective field management strategies to ensure a successful harvest this season.
To address the current situation, we will discuss several key measures tailored to local conditions:
1. **Current Growth Stage and Characteristics**
Most cotton fields are now entering the bud stage, which marks the transition from vegetative to reproductive growth. Although vegetative growth is still dominant, the development of roots is accelerating rapidly, reaching its peak before flowering. In fact, the main root grows two to three times faster than the above-ground parts. This makes the bud stage a crucial time for root development. Nutrient requirements shift from nitrogen to a more balanced mix of phosphorus and potassium during this period. The duration of the bud stage typically lasts 24–30 days, with Hebei’s usual start around early June, but this year it has been delayed until June 5–10.
2. **Key Management Goals**
Due to the unfavorable weather this season, many cotton plants are growing slowly and weakly. The primary goal is to promote healthy growth in underperforming fields while maintaining strong growth in high-yielding ones. The focus should be on encouraging robust vegetative growth, increasing leaf area, and supporting early budding and flowering. All actions should align with the principle of "steady growth" to maximize yield potential.
3. **Current Field Management Practices**
- **Timely Cultivation**
With ample rainfall in many areas, irrigation is generally not needed. However, regular cultivation is essential. Weak fields should be cultivated more frequently—every 7–8 days—while high-yield fields benefit from deeper cultivation (at least 8 cm). On dry land, shallow cultivation is recommended to avoid damaging roots. For waterlogged fields, deep plowing helps control root growth and prevent premature aging.
- **Fertilizer Application Based on Need**
Top-dressing should be done carefully. In well-fertilized or vigorous fields, reduce or avoid nitrogen fertilizer. A small amount of diammonium phosphate (5 kg per mu) can be applied instead. For weak or poorly nourished fields, apply 12.5 kg of urea and 5 kg of potassium per mu, along with foliar sprays of 2% urea and 0.3% potassium dihydrogen phosphate. Be cautious with nitrogen use to avoid excessive growth and poor light penetration.
- **Film Removal and Soil Loosening**
In northern regions, it's best to remove plastic mulch later, ideally in late June, to encourage stronger root development. After removal, cultivate the soil to improve drought resistance. In southern areas, drainage ditches should be dug to prevent waterlogging.
- **Scientific Pruning**
Pruning should be delayed slightly, with full pruning starting when 3–4 fruit branches are visible. This helps increase vegetative mass and strengthen weak plants. In high-yield fields, remove lower leaves and limit fruit branch pruning to 2–3 leaves.
- **Growth Regulation**
Apply growth regulators at a concentration of 30–50 ppm (about 0.4–0.75 g per 30 liters of water), with 0.3–0.8 g per mu. The best time to spray is during the Sheng Lei period (when four fruit sticks are visible). Fields with good growth can be sprayed more frequently, while dry or weak fields may need less or no treatment. If plant height exceeds 40 cm, a second application of up to 2 g per mu is recommended.
- **Pest Control**
Common pests include bollworms, aphids, spider mites, and weevils. For bollworms, a combination of malathion and phoxim is effective and cost-efficient. For aphids, acetamiprid works well, especially when resistance is a concern. Spider mites respond well to avermectin-based products, and for bollworms, options like chlorpyrifos and acephate are available.
- **Disease Prevention**
Wilt disease remains a concern, even though its early-season incidence was low. The peak period usually occurs in mid-to-late June, so proactive field management and improved disease resistance are essential.
By implementing these targeted practices, farmers can help their cotton crops overcome the challenges of this season and lay the foundation for a successful harvest.
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