Seedling Establishment and Grain Yield of Tropical Rice Sown in Puddled Soil

Inconsistent seedling establishment constrains wider adoption of direct sowing of rice (Oryza sativa L.) in the tropics. Farmers broadcast pregerminated seeds onto the puddled soil surface. We hypothesize that if seeds were sown into the puddled soil rather than on the soil surface, then the establishment could be more consistent. For such below‐surface sowing to be successful, however, the seedling must be able to withstand anoxic conditions. This study was conducted to clarify whether seedlings can be established by sowing below the surface in puddled soil and to analyze the difference in establishment among cultivars. Anoxia‐tolerant cultivars, which had been selected from screening trials, were evaluated in flooded soil in a container in a temperature‐controlled (29/21°C day/night) glass room under natural light and in the fields during the dry season at Los Baños and Muñoz, Philippines. In the container, pregerminated seeds of 12 cultivars were sown at the 25‐mm depth in the soil with a water level of 30 mm. In the field, pregerminated seeds of 10 cultivars and calcium peroxide–coated seeds of two cultivars were drill‐sown at Los Baños; pregerminated seeds of 12 cultivars were drill‐sown and broadcast at Muñoz. Drill sowing was conducted 1 d after puddling, while broadcast sowing was done on the same day. The anoxia‐tolerant cultivar outperformed the check cultivar in plant stand and seedling height and weight, hence producing more biomass. Plant stands at Los Baños were 80.5% for tolerant and 64.0% for check cultivars; those at Muñoz were 57.5 and 24.6% for drill sowing and 59.1 and 26.7% for broadcast sowing, respectively. Mean grain yield of short anoxia‐tolerant cultivars was 6.9 t ha−1, which was the same as that of check cultivars. It is concluded that the use of anoxia‐tolerant cultivar can stabilize seedling establishment of rice plants sown in the puddled soil.