Improvement of lodging resistance in submerged direct seeding rice (Oryza sativa L.) cultivation using a newly developed 'shooting hill-seeder' - Method of hill-seeding for the improvement and stabilization of lodging resistance

By using a newly developed 'Shooting hill-seeder', it is easy to adjust the hill space within a row or the seeding depth, and change the hill-seeding form in the submerged direct seeding rice cultivation. In this study, the e ffects of these seeding conditions on the lodging resistance of hill-seeded rice were examined. It was suggested that the increased hill space within a row resulted in lower lodging resistance because of the elongation of cul m and decrease in pushing resistance of the hill. These results show the im portance to adopt a variety with high lodging resistance, or to control the nitrogen uptake by improvement of fertilizer application or water manageme nt, when a large hill space is necessary. On the other hand, the hill-seedi ng form did not seem to affect the lodging resistance. Furthermore, in hill -seeded rice, the chance of shallow seeding is rare, and the degree of lodg ing due to shallow seeding is extremely small as compared with broadcast-se eded rice. These characteristics are very important for the stabilization o f the submerged direct seeding cultivation, in which unification of the see ding depth is difficult, and the stabilization of seedling emergence is imp ortant.