Seedling establishment and grain yield of tropical rice sown in puddled soil

Inconsistent seedling establishment constrains wider adoption of direct sow ing of rice (Oryza sativa L.) in the tropics. Farmers broadcast pregerminat ed seeds onto the puddled soil surface. We hypothesize that if seeds were s own into the puddled soil rather than on the soil surface, then the establi shment could be more consistent. For such below-surface sowing to be succes sful, however, the seedling must be able to withstand anoxic conditions. Th is study was conducted to clarify whether seedlings can be established by s owing below the surface in puddled soil and to analyze the difference in es tablishment among cultivars. Anoxia-tolerant cultivars, which had been sele cted from screening trials, were evaluated in flooded soil in a container i n a temperature-controlled (29/21 degrees C day/night) glass room under nat ural light and in the fields during the dry season at Los Banos and Munoz, Philippines. In the container, pregerminated seeds of 12 cultivars were sow n 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 t wo cultivars were drill-sown at Los Banos; pregerminated seeds of 12 cultiv ars were drill-sown and broadcast at Munoz. Drill sowing was conducted Id a fter puddling, while broadcast sowing was done on the same day. The anoxia- tolerant cultivar outperformed the check cultivar in plant stand and seedli ng height and weight, hence producing more biomass. Plant stands at Los Ban os were 80.5% for tolerant and 64.0% for check cultivars; those at Munoz we re 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 th at the use of anoxia-tolerant cultivar can stabilize seedling establishment of rice plants sown in the puddled soil.