How should rice seedling beds be managed to cultivate strong seedlings?

I. Water management in seedling beds: For dry-raised seedlings, generally no supplemental water is needed during the seedling stage. Adhere to dry raising and dry management to improve the drought tolerance of the seedlings. At the same time, pay attention to watering well three times: water thoroughly with "bottom moisture water" before sowing, water well with "film-removal water" when removing the film, and water well with "leaf-rolling water" during drought. At the 1-2 leaf stage, control water appropriately to promote downward growth of seminal roots; at the 2-3 leaf stage, pay attention to supplemental water to prevent seedling death; after the 3-4 leaf stage, strictly control water and use dry raising to cultivate physiologically strong seedlings. To prevent excessive rainwater from making dry raising and dry management impossible, small arched sheds or greenhouses can be used to strictly control water for dry raising. For seedling raising of rice for seedling throwing, adopt the moist irrigation method of full ditch water on sunny days, half ditch water on cloudy days, and draining dry water on rainy days. The water layer should not exceed the tray surface to prevent the root soil from rising and forming connected roots. For moist seedling raising, from sowing to the 1 leaf 1 heart stage, keep water in the ditch and maintain the seedling board moist; at the 3 leaf stage, establish a water layer and implement shallow water frequent irrigation to promote tiller growth.

II. Fertilization in seedling beds: After strict fertilization, dry-raised rice seedling beds generally have sufficient fertilizer, complete nutrients, and high available nutrient content, so weaning fertilizer is generally not needed. Only after the 3 leaf stage should topdressing be applied timely and appropriately according to seedling condition. Generally, apply 4-5 kg urea per mu or irrigate with 750 kg manure water. Apply starting fertilizer 1-2 days before pulling seedlings, with 7-8 kg urea per mu. Topdressing should be done in the evening, using the method of first broadcasting and then spraying water to wash it in. For seedling raising of rice for seedling throwing, topdress appropriately: apply weaning fertilizer at the 1 leaf 1 heart stage, with 3-4 kg urea per mu, and apply starting fertilizer 2-3 days before throwing transplanting, with 5-6 kg urea per mu. For conventional moist seedling-raising fields, adhere to the fertilization principles of applying weaning fertilizer early, skillfully applying relay fertilizer according to seedling condition, and heavily applying starting fertilizer. Weaning fertilizer at the 1 leaf 1 heart stage, with 5-6 kg urea per mu; relay fertilizer at the 3-4 leaf stage, with 3-5 kg urea per mu; starting fertilizer 2-3 days before pulling seedlings, with 8-10 kg urea per mu, and transplant with fertilizer.

III. Pest and disease control: During the seedling stage, win the overall battle for control of pests and diseases, focusing on small brown planthopper and also controlling stem borers and other pests and diseases. Focus on carrying out full-course chemical control from the migration of small brown planthopper into seedling fields to the peak migration of first-generation small brown planthopper adults. Insecticides with good residual effect such as pymetrozine and fipronil can be selected for control, and mixed with fast-acting pesticides such as imidacloprid, chlorpyrifos, isoprocarb, and dichlorvos to prolong the control period and improve the control effect. During the seedling field stage, determine the pesticide application interval and number of treatments according to the number of virus-carrying insects and the resistance or susceptibility of varieties. For seedling fields with high numbers of virus-carrying small brown planthopper, a long peak adult period, and susceptible varieties, shorten the pesticide application interval and implement full-course chemical control to improve the control effect on small brown planthopper; for seedling fields with low numbers of virus-carrying insects or relatively resistant (tolerant) varieties, the pesticide application interval can be extended and the number of treatments reduced. In combination with early control of small brown planthopper in seedling fields, for susceptible varieties in severely affected areas, add virus inactivators such as Jun Ke Du Ke to improve control of rice stripe leaf blight. In severely affected stem borer areas along the Yangtze River, southern Jiangsu, and northern Huai regions, while controlling small brown planthopper to control rice stripe leaf blight, pay attention to also controlling first-generation stem borers, rice thrips, and other pests and diseases.