What are the key management points during the grain-filling stage of rice?
The grain-filling stage of rice is the critical period that determines yield. Field management should aim to nourish the roots and protect the leaves, prevent premature senescence, improve photosynthetic efficiency, promote grain filling, and increase the seed-setting rate and grain weight.
1. Supplemental application of grain fertilizer: apply grain fertilizer according to the seedlings, the field, and the weather. Apply it when the leaf color is on the yellowish side and the flag leaf is short and small; do not apply it when the leaf color is deep green and the flag leaf is large and plump. Apply it to lean fields, not to fertile fields; apply it when there are many sunny days, not when there are many cloudy and rainy days. Generally, it is appropriate to apply 2-3 kg of urea per mu at the booting stage.
2. Rational irrigation: rational irrigation during the grain-filling and seed-setting stage can nourish the roots and protect the leaves, reducing empty grains and blighted grains. A certain water layer should be maintained in the field during the heading and flowering stage. During the grain-filling stage, keep the soil mainly moist, with alternating wet and dry irrigation, that is, after watering, let it dry naturally for 1-2 days before irrigating again, so as to maintain root activity. Sandy loam with good permeability often suffers premature senescence due to lack of water, so this method should not be used; instead, a shallow water layer should be maintained. If high temperatures occur during the flowering stage or low temperatures occur during the seed-setting stage, deep water should be irrigated as early as possible to regulate the temperature and reduce empty grains and blighted grains. Water should not be cut off too early before harvest. For early rice, cut off water 4-5 days before harvest; for middle and late rice, cut off water 6-7 days before harvest.
3. Do a good job of the “four preventions”
1. Prevent and control pests and diseases. The main pests and diseases in this period include rice blast, bacterial leaf blight, rice false smut, sheath blight, rice leaf roller, and rice planthopper. Fields with too many total tillers and vigorous growth should be taken as the key targets for control, and control should be carried out at the key stage of rice booting.
2. Prevent lodging. Rice lodging mainly occurs during the seed-setting stage. In addition to strengthening fertilizer and water management and preventing and controlling pests and diseases, 3% superphosphate extract can also be sprayed multiple times on vigorously growing fields. When the panicles are about to fully emerge, spray 40 ml of 40% maize growth regulator mixed with 40 kg of water to inhibit elongation of the internodes below the panicle and enhance lodging resistance.
3. Prevent excessive vegetative growth. For fields with overly tender growth, plump leaves, and drooping flag leaves, spray 500 mg/kg ethephon at the milk-ripening stage to promote ripening.
4. Prevent premature senescence. In addition to increasing grain fertilizer and strengthening water and slurry management, foliar spraying of 2% urea and 0.3% potassium dihydrogen phosphate solution can also be used. Spraying a mixed solution of triadimefon and Luyexianfeng in the later stage can significantly protect leaves and prevent senescence.