In the South China Rice Region, effective pre-production management techniques are essential for early rice cultivation. The timing of planting is crucial—early rice should be sown before and after the Qingming Festival in the southern region, before and after the Grain Rain in the central area, and before May 1st in the northern part. Key technical measures include:
1. **Optimized Fertilization and Planting Density**: Base fertilization should include 30 kg of calcium ammonium nitrate, 7.5 kg of potassium chloride, and 25 kg of ammonium bicarbonate per mu. If available, 1,000–1,500 kg of high-quality farmyard manure can be added. Plant 21,000–25,000 holes per acre, with two seedlings per hole for hybrid rice and 4–6 for conventional varieties. Apply 5–6 kg of urea 5–7 days after transplanting, and 7.5 kg of urea plus 7.5–10 kg of potassium chloride or 12.5–15 kg of compound fertilizer 12–15 days later to promote strong growth.
2. **Water Management During Transplanting**: Maintain a thin water layer (1.5–2 cm) during transplanting and increase it to 3–4 cm afterward. Avoid standing water during the transplanting process and refill with 1.5–2 cm of shallow water. Keep the water level below 2 cm during the tillering phase. Drain the field when the tiller population reaches 200,000 per mu, around 15–20 days after transplanting.
3. **Disease and Pest Control**: Implement integrated pest management strategies to control diseases like rice blast, leaf sheath blight, and pests such as stem borers and leaf rollers.
In the middle reaches of the Yangtze River, the early rice planting season has been delayed due to rainy weather in March. However, high temperatures after sowing have accelerated seedling growth. If the weather remains favorable, transplanting will proceed normally in mid to late April. Key practices include:
1. **Irrigation Management**: After temperature drops, ensure timely watering, especially for dry seedlings, to prevent young plant death.
2. **Ventilation and Seedling Hardening**: As temperatures rise, remove the plastic cover gradually and ventilate both sides of the seedbed. In hot weather, open the film earlier and irrigate to protect the plants.
3. **Nutrient Application**: After removing the film, apply 3–4 kg of urea per acre 3–5 days before transplanting to ensure uniform seedling growth.
In the Southwest Rice Region, current conditions are favorable for rice seedling management, though some challenges exist, including delayed planting and lower seed quality. To address these issues:
1. **Timely Planting and Scheduling**: Ensure winter fallow and green manure fields are planted on time. Use intensified rice cultivation techniques where possible. Adjust planting schedules based on seedling age, typically not exceeding 25 days for mechanical transplanting and 40 days for tray seedlings.
2. **Seed Treatment**: Perform thorough seed drying, selection, soaking, and germination to improve germination rates and reduce disease risk at the seedling stage.
3. **Monitor Germination Rates**: Adjust seeding rates based on actual germination performance. If less than 80%, replant promptly to maintain adequate seedling density.
4. **Protect Against Environmental Stress**: Cover seedlings with straw to prevent sunburn during high temperatures and water them in the evening if needed.
5. **Pest and Disease Control**: Monitor and manage thrips, aphids, and rice blast according to local forecasts.
In the Northeastern Rice Area, one-season rice seedlings face challenges from low temperatures and high humidity. This year’s early spring weather has been cooler than usual, with higher rainfall. Current best practices include:
1. **Controlled Nursery Conditions**: Prefer vegetable or garden fields for seedling production. If using field nurseries, choose high-elevation, well-drained soils with high organic content. Build raised beds at least 30 cm high.
2. **Proper Seed Processing**: Follow strict procedures for drying, salting, disinfecting, and germinating seeds to ensure quick root development and even emergence.
3. **High-Quality Nutrient Soil Preparation**: Mix 60–70% soil with over 3% organic matter with 30–40% decomposed compost. Adjust pH to 4.5–5.0 and add 150–200 g of ammonium sulfate, 300 g of superphosphate, and 100 g of potassium sulfate per 100 kg of soil.
4. **Seeding Rate Control**: Adjust seeding rates based on seedling type, typically 150–300 grams per square meter.
5. **Temperature Regulation**: Ventilate seedlings between 1.5–2.0 leaves, keeping bed temperatures at 25–30°C. For 2.5–3.0 leaves, maintain temperatures between 20–25°C.
6. **Disease Prevention**: Monitor for bacterial wilt and blight, and implement preventive treatments as needed.
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