Detailed Explanation of the Latest Technical Methods for Rice Seedbed Management
Rice has entered the critical period of seedbed management. Effectively strengthening seedbed management plays a vital role in cultivating strong seedlings and ensuring a bumper rice harvest. To properly carry out field management during the dry-raised seedling stage, attention should focus on the following 7 aspects:
1. Regulate film temperature. From sowing until the needles emerge, the main task of seedbed management is to promote emergence and full stands. When sowing in early spring, outdoor temperatures are low, so in terms of temperature management, sealing the film to retain heat is the main approach. After sowing, check frequently for exposed seed or air leaks. If exposed seed or air leaks are found, cover the seed with soil and seal the film promptly. Before emergence, keep the temperature inside the film at 30-32 degrees C. From emergence until the 1.5-leaf stage, keep the daytime temperature inside the film below 25 degrees C. After the film is removed, if the daily average temperature exceeds 20 degrees C, the seedbed should also take shade and cooling measures.
2. Remove the film when needles stand. Covering with film after sowing in early spring aims to increase temperature and preserve moisture, promoting early and uniform emergence. However, if the film is removed early, in places with low temperatures the seedlings grow slowly and may even become stunted; if the film is removed late, as temperatures rise, the temperature inside the film becomes high, causing seedlings to grow leggy and have poor resistance, and the first leaf node struggles to tiller. Under normal circumstances, the best time to remove the film is 5-7 days after sowing, before the first complete leaf unfolds (needle-shaped, about 2 cm or so). On the day of film removal, if the air humidity is high and the temperature is on the low side with overcast and rainy weather, the film should be removed in the morning; if it is sunny, the film should preferably be removed in the evening.
3. Water thoroughly when removing the film. When removing the film, you must remove the film and water at the same time, and water thoroughly. This is because after the film is removed, the air temperature around the seedlings rises sharply, while root water uptake often cannot keep up, making bacterial wilt and seedling death likely. Therefore, water thoroughly at film removal in time to supplement the soil moisture deficit after film removal, so the seedlings can adapt to environmental changes as quickly as possible.
4. Supplement with “weaning” water. At the 2-3 leaf stage, seedlings have the poorest tolerance, the shortest time from leaf rolling to death, and are most sensitive to water deficit. This period is also the most critical time for preventing seedling death and increasing the seedling survival rate. If the water at film removal was insufficient, evaporation is excessive, and soil moisture is poor, “weaning” water must be supplemented in time.
5. Moderate chemical control. For seedbeds where soil was not treated with strong-seedling agent, especially when cultivating long-age large seedlings, spray a 250-300 ppm paclobutrazol solution mixed with Saisheng seaweed acid iodine at the 1-leaf-1-heart and 3-leaf-1-heart stages respectively, to promote tillering and dwarf the seedlings.
6. After the 3-leaf stage, control water for dry raising. After the 3-leaf stage, the seedlings are larger and the root system gradually develops. Generally, they should not be watered at will; water control for dry raising should be the main approach to prevent excessive growth from too much water. If high temperature and drought occur, and the leaves wilt at noon and form “rolls” and do not unfold at night, water must be applied promptly in the evening. However, the amount of water should not be large, and the frequency should not be high.
7. Water thoroughly with “send-off” water. On the evening before transplanting, apply send-off water together with send-off fertilizer using a 1% urea aqueous solution. This watering is very particular: it must be moderate, neither too much nor too little; and it must be timely, neither too early nor too late, so that pulling the seedlings is effortless and the root system is disturbed as little as possible. After transplanting, spray Saimiao seaweed acid iodine as soon as possible to promote root healing and growth.