Reduction of Rice Chalky Grain by Deep and Permanent Irrigation Method; Effect on Growth and Grain Quality of Rice

Formation of chalky grains which is the main cause of the degradation of rice grain quality occurs frequently when the temperature during the 20 days after heading exceeds 27 degrees C. In this study, we examined the grain quality, chalky grain formation, growth and yield of plants grown by the deep and permanent irrigation (DPI) method, which is a combination of the V-furrow direct seeding method and the deep-flooding irrigation method. Field experiments were conducted in 2008, 2009 and 2010. The DPI method in which the water level was maintained at about 20 cm above the soil surface, improved grain quality by decreasing the chalky grain ratio by about 5% and increasing the perfect grain ratio by about 10% as compared with the V-furrow direct seeding method in which the water level was maintained at about 10 cm above the soil surface. The DPI method decreased the number of tillers and panicles but increased the number of spikelets per panicle so that the two methods gave similar yields. DPI is a promising labor-saving method expected to reduce the formation of chalky grain due to a high temperature during ripening.