The growth of seedlings follows its own specific rules, so it's essential for farmers to operate and manage them scientifically before and after transplanting into the field. Proper cultivation must be based on the characteristics of seedling development. As our province is a major grain-producing region that primarily grows double-crop rice, the mechanized planting techniques can be categorized into early rice and late rice field management practices. This section mainly focuses on the key techniques for early rice cultivation.
First, field preparation is crucial. Soil preparation and fertilization are the first steps. Before transplanting, the field should be leveled, and base fertilizer should be applied with an increased amount of organic fertilizer. During plowing, about 70-80% of the total nitrogen fertilizer, all phosphate fertilizer, and approximately two-thirds of the potassium fertilizer should be used as base fertilizer. The soil should be fine and level, but not too high, with a moderately soft top layer. To improve fertilizer efficiency, dry tillage and dry application of fertilizer with controlled water levels are recommended. For green manure fields, 500 kg of animal manure per mu is applied, while for non-green manure (winter fallow) fields, 1000 kg of animal manure per acre is needed, along with 40 kg of ammonium bicarbonate or 10-12 kg of urea, 30 kg of superphosphate, and 5 kg of potassium chloride as a top-dressing. If using water tillage, the depth should not be too deep, as excessive water may cause the field to become too soft, leading to the transplanter sinking deeper and increasing resistance. Additionally, excessive mud can make it difficult to handle seedlings during planting. Therefore, sandy soils should be dried for one day, and clay soils for 2-3 days before thin water planting.
Second, the machine transplanting process should occur when the seedlings are around 20 days old, with three and a half leaves. The field surface should be kept shallow during transplanting. If the water is too deep, it affects the depth of the machine’s insertion, increases drifting, and causes waves that may damage the already planted seedlings, leading to more side seedlings and drift. The quality of machine transplanting plays a vital role in determining the yield and is a key factor in achieving higher productivity. Good transplanting should ensure proper density, even distribution, low injury rate, minimal missing plants, less drift, and no seedling loss due to water or mud. Typically, 1.4 to 1.8 million holes per mu are required, with 1-3 grains per hole for hybrid rice. The spacing is usually 30×11.6–14.7 cm, adjustable based on seedling uniformity. The planting depth is generally about 1.5 cm.
Third, water management is critical. The principle is to use thin water for planting, maintain light flooding during the growing phase, apply shallow water during stem elongation, keep the field slightly dry before heading, and alternate between wet and dry conditions during maturity. Watering methods include using thin dew irrigation, allowing the field to dry naturally for 3–4 days before rewatering. The water depth should cover the mud. When the total number of tillers reaches 80% of the expected panicle count, controlled dehydration helps improve ventilation and light penetration, enhancing plant health and promoting large ears at lower positions.
Fourth, fertilizer application is essential. Base fertilizer should be applied, followed by limited topdressing. Organic fertilizer, combined with NPK, should be used, with 70–80% of nitrogen fertilizer as base fertilizer and 20–30% as topdressing. All organic and phosphate fertilizers should be applied as base fertilizer, while two-thirds of the potassium fertilizer should be used as base fertilizer and one-third as topdressing. If the base fertilizer is insufficient, 5 kg of urea and potassium chloride can be combined with weeding 7 days after planting. Applying panicle fertilizer during the stage when the second leaf turns back and the flag leaf expands is most effective, typically when the young panicle begins to differentiate. About 3–5 kg of urea and potassium chloride per mu are recommended. Before applying, the soil should be slightly dry, and after application, water should be slowly added to allow the nutrients to penetrate the soil. After heading, a grain fertilizer can be applied once, using 0.5 kg of urea and potassium chloride, plus 150 g of potassium dihydrogen phosphate dissolved in 50 kg of water.
Finally, pest control is important. Before transplanting, spraying 20% tricyclazole at 750 times dilution or using 40% emulsifiable oil at 100% concentration per acre can help prevent pests. After planting, timely and accurate control of pests such as rice blast, sheath blight, and stem borers is necessary to reduce production costs and increase yield.
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