How to manage water for rice? A detailed explanation of the three-drainage, three-irrigation water management method

    I. Three drainages 

    First drainage: From the critical tillering stage of rice 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 where the seedlings grow vigorously with dark green leaves, as well as fertile fields and cold-waterlogged fields, heavy sun-drying is needed to help the leaf color fade; for fields where the seedlings grow poorly, 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, to the extent that the field does not sink underfoot. 

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

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

    II. Three irrigations 

    First irrigation: From rice 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 where organic fertilizer (green manure, straw manure, etc.) has been applied excessively, or lake fields and cold-waterlogged fields, to prevent stiff seedlings, the water can be allowed to dry naturally after transplanting, and after exposing the field for 3-4 days, shallow water should be irrigated again, so as to reduce the harm of toxic substances to the rice root system and prevent the rice from excessive vegetative growth and late ripening. 

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

    Third irrigation: From heading to the yellow-ripe stage of rice, a shallow water layer should be maintained in the field to lower the temperature, reduce the harm of high temperatures 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 used, that is, irrigate shallow water and let it dry naturally, then expose for 1-2 days before irrigating shallow water again, so that it alternates between wet and dry, in order to achieve the purpose of nourishing the roots and preserving the leaves.