Wet irrigation for rice is a water-saving irrigation mode that requires shallow water irrigation, with the next watering conducted only after the previous watering has dried up. This irrigation method can alter soil aeration conditions, enhance soil permeability, activate beneficial soil microbes, decompose toxic substances, improve soil physicochemical properties, stimulate root development, strengthen nutrient absorption capacity, and significantly increase crop yields.
The key points of wet irrigation techniques for rice in the early, middle, and late stages are as follows:
Early Stage – From Transplanting to Tillering: Due to root damage during transplanting, seedling water absorption is weak. Therefore, shallow water and shallow planting are required, maintaining a thin water layer (below 20 millimeters) to reduce leaf evaporation, mitigate the adverse effects of low and high temperatures and wind, and promote early root and leaf growth. About three days after transplanting, the field should be allowed to dry naturally. This drying should be light, and when there is no water on the field and “bee mud” appears, it is time for the first topdressing and chemical weeding with thin water. Maintain the water layer for about five days to ensure weed control. After each watering, the field should be allowed to dry naturally until the soil surface is about to crack before watering again.
Studies have shown that rice tillering speed increases in the order of dry, deep irrigation, shallow irrigation, and wet irrigation. Wet irrigation can meet the physiological water needs of rice seedlings and their aeration requirements. At the end of tillering, field drying is an effective means to control ineffective tillering, but the degree must be mastered well. Early tillering and sufficient tillers in vigorous fields should be dried early and heavily, while late tillering and few tillers should be dried late and lightly. The standard for heavy drying is when the field surface cracks, the soil surface is white, the white roots are exposed, the leaves are erect, and the color fades, generally about seven days; the standard for light drying is when the soil is tight, the field edge cracks, the field does not sink, and it takes about four days. It is generally required to end field drying before heading begins.
Middle Stage – From Booting to Heading: The booting tillering stage is a period of simultaneous vegetative and reproductive growth, with vigorous plant growth, high water consumption, and peak photosynthesis. During this period, thin water should still be used for irrigation, but the field drying degree is lighter than in the early stage. Thin water should be applied when the field is about to run out of water, maintaining soil moisture saturation at 100%. However, prolonged water coverage can enhance reducing conditions, inhibit root growth, and increase susceptibility to diseases, pests, and lodging. Measures should be taken to maintain temperature stability when encountering high temperatures or low temperatures (mid-season rice above 40°C, late-season rice below 15°C). For fields with high groundwater levels, strong water retention, and excessive growth, about 3-5 days before heading when the development of each part of the panicle is completed, the field can be lightly dried and exposed to sunlight for 1-2 days to improve soil permeability and prevent premature root aging.
Late Stage – Milk and Dough Ripening Period: The milk ripening period requires adequate soil moisture and air to ensure that the roots remain vigorous. Therefore, the drying degree can be increased, and thin water can be applied when the soil surface cracks 1-2 millimeters. During the dough ripening period, rice plants are aging, and to prevent root lignification, soil oxygen should be increased. Therefore, the drying degree should be increased further, and thin water can be applied when the soil surface cracks 4-5 millimeters. Water should be cut off in advance before harvest, generally 5 days in advance for early rice and about 10 days for late rice. Premature water cutoff will affect yield and grain quality.
