Detailed Explanation of the Three-Drainage and Three-Irrigation Water Management Measures for Rice

1. Three Drainages

First drainage: From the critical tillering stage to the stage when the penultimate leaf tip emerges (20 days before heading), the field should be drained and sun-dried to control the growth of ineffective tillers. For fields with vigorous seedling growth and dark green leaf color, as well as fertile fields and cold-waterlogged fields, heavy sun-drying should be carried out to promote fading of leaf color; for fields with poor seedling growth, as well as lean fields and fields with a low groundwater table, multiple light sun-dryings should be carried out, combining sun-drying with exposure, with the degree judged by the field not sinking underfoot.

Second drainage: From 5-7 days before heading to the heading stage, a second drainage should be carried out to improve rice root vigor and enhance the roots' ability to absorb nutrients.

Third drainage: After rice enters the yellow-ripening stage, immediate drainage and sun-drying of the field helps reduce the moisture content of the grains, promotes early ripening of the rice grains, improves rice quality and yield, and facilitates harvesting and threshing.

2. Three Irrigations

First irrigation: From transplanting to the critical stage of effective tillering, shallow water should be applied frequently, maintaining a 2-3.3 cm water layer in the field. For fields with excessive application of organic fertilizer (green manure, straw manure, etc.) or lake fields and cold-waterlogged fields, to prevent stiff seedlings, the field can be allowed to dry naturally after transplanting, exposed for 3-4 days, and then irrigated with shallow water, so as to reduce the harm of toxic substances to rice roots and prevent rice from staying green and ripening late.

Second irrigation: From the stage when the second leaf tip emerges to the stage when the rice spikelet number is determined (5-7 days before heading), water shortage will reduce the number of grains per panicle. Therefore, from the stage when the second leaf tip emerges to the rice flowering stage, water should be restored immediately, and a shallow water layer should be maintained until the spikelet number determination stage.

Third irrigation: From heading to the yellow-ripening stage, a shallow water layer should be maintained in the rice field to lower the temperature, reduce the harm of high temperature to rice, and reduce the harm of cold dew wind. After rice enters the grain-filling stage, to prevent premature senescence, the intermittent irrigation method can be adopted, that is, irrigate with shallow water and let it dry naturally, then expose for 1-2 days before irrigating with shallow water again, so that the field alternates between dry and wet, in order to achieve the purpose of nourishing the roots and preserving the leaves.