Improvement of lodging resistance in submerged direct seeding rice (Oryza sativa L.) cultivation using a newly developed 'shooting hill-seeder' - Effects of seedling density on the lodging resistance of hill-seeded rice as compared with that of broadcast-seeded rice

The characteristics of lodging resistance in hill-seeded rice were compared with those in broadcast-seeded rice at three different plant densities (40 , 80 and 160 plants m(-2)) to establish the submerged direct seeding rice c ultivation using a newly developed 'Shooting hill-seeder'. In the hill-seed ed rice, the culm was longer than in broadcast-seeded rice, applying a stro ng force to the basal part of the hill. However, they did not lodge easily because the percentage of productive tillers was high resulting in superior characteristics of the culm related to the lodging resistance, and they ha d extremely high pushing resistance. Such differences in the lodging resist ance between hill- and broadcast-seeded rice plants were remarkable at a hi gh plant density. In the broadcast-seeded rice, the number of panicles per hill is fewer than 10 when they are cultivated at a density higher than 40 plants m-2, and the lodging resistance decreased with decreasing number of panicles per hill. On the other hand, in the hill-seeded rice (40-160 plant s m(-2), 30cm inter-row and 20cm intra-row spacing), the number of panicles per hill is 20-25 even when the seedling density fluctuates within the ran ge of 40-160 seedlings m(-2) (2-10 seedlings per hill), and lodging resista nce is stable. Because the fluctuation of seedling density is inevitable, t he hill-seeding cultivation with the above characteristics is favorable for the stabilization of submerged direct seeding cultivation.