Mechanically direct-seeded rice has a wide root system in the shallow soil, exhibits significant low-level tillering dominance, and produces robust plants with full panicles and uniform panicle shape. However, compared to other rice cultivation methods, it faces challenges such as tight planting seasons, difficulty in achieving uniform and full seedling emergence, and increased weed infestation. Therefore, supporting technologies must include large-scale planting, early sowing, improved sowing quality, integrated weed control, and fertilizer and water regulation, effectively addressing five key aspects: seedling establishment, weed control, pest and disease control, fertilizer application, and lodging prevention.
I. Seedling Establishment: Select high-yielding, lodging-resistant, and adaptable varieties suitable for local cultivation. After seed selection, soak seeds in a pesticide such as chlorhexidine for 50-60 hours before sowing. Sow seeds after they show signs of sprouting. Carefully prepare the land, ensuring the paddy field is level and loose. Generally, rotary tillage is used to remove stubble, followed by harrowing and leveling. Then, water is released to allow the soil to dry and settle, and sowing is done the following day with a light layer of water. For late-season japonica rice, sow early to ensure sufficient nutrient growth period. The seed quantity should not exceed 7 kg per mu (approximately 0.067 hectares), with 65-80 grains per row per meter. Sowing is best done in early June, and should be completed before June 15th. After sowing, promptly dig the central and perimeter ditches to ensure unobstructed drainage; drain any standing water to prevent seed rot and ensure full seedling emergence.
Secondly, regarding lodging: Maintain a basic seedling density of 80,000-100,000 per mu. Keep the soil moist during the seedling stage. Around the 2-leaf stage, irrigate with a thin layer of water (1.5-2 cm), followed by shallow watering to encourage tillering. At the 4-leaf stage, transplant seedlings to fill in sparse areas, ensuring full and even seedling emergence. Begin intermittent irrigation at the 6-7 leaf stage, lightly draining the water in stages. After draining and re-irrigating, maintain clear, firm, moist, and flowing water to promote panicle growth and grain filling. Irrigate for the last time 5-7 days before harvest, then stop irrigation to prevent premature dehydration and reduced grain weight.
III. Fertilizer: Apply fertilizer before rotary tillage and stubble removal, using 25 kg of ammonium bicarbonate and 50 kg of compound fertilizer per mu (approximately 0.067 hectares). Adopt a balanced fertilization method, saving nitrogen fertilizer and increasing phosphorus. The nitrogen, phosphorus, and potassium ratio is 1:0.15:0.4. Control the pure nitrogen fertilizer at 20 kg per mu, phosphorus pentoxide at 5 kg per mu, and potassium oxide at 10 kg per mu. Apply tillering fertilizer at the 2-4 leaf stage of seedlings, in two applications. The first application should be early, using 15 kg of ammonium bicarbonate per mu. Apply growth-promoting fertilizer in late May, using 30 kg of ammonium bicarbonate and 10 kg of potassium chloride per mu. Apply heading fertilizer in mid-August, using 10 kg of urea per mu. The amount of fertilizer should be strictly controlled to prevent lingering and delayed maturity.
IV. Weeds Weed control requires early intervention and addressing small weeds, combining manual and chemical methods, early and mid-stage chemical weeding, and wet and water-based application. Within 4 days of sowing, spray 75-100 ml of 30% flufenoxuron emulsion per acre diluted in 50 kg of water. Keep the field moist but not waterlogged after application. At the 2-4 leaf stage, spray 15-20 g of chlorpyrifos or 600-700 g of 10% benzyl chloride per acre diluted in water, maintaining a water layer for 5-7 days after application. For fields with a high incidence of broadleaf weeds at the late tillering stage, spray 100-150 g of 20% 2,4-D aqueous solution plus 100 g of bentazon aqueous solution per acre. Drain the field before application, apply the herbicide when there is no dew on the rice leaves, and re-irrigate the field the following day.
V. Pests and Diseases: During the seedling stage, the main control is for rice thrips. Use 100-150 grams of dimethoate per mu (approximately 0.067 hectares) diluted in water. Spray with a water layer in the field. To control rice weevils, use 2-3 grams of cypermethrin or 20 ml of 2.5% deltamethrin per mu diluted in 50 kg of water, then drain the field and spray. During the mid-stage, focus on controlling rice leaf rollers and sheath blight. In the late stage, pay attention to controlling stem borers, rice planthoppers, rice blast, and rice false smut.
