Improved Lodging Resistance in Rice (Oryza sativa L.) Cultivated by Submerged Direct Seeding Using a Newly Developed Hill Seeder

Abstract

Submerged direct-seeded rice is more susceptible to lodging during the ripening period than is transplanted rice. Comparing different seeding methods of direct seeding cultivation, lodging resistance is considered to be highest in hill-seeded rice. However, practical hill-seeders did not exist, and previously direct-seeding had been conducted by broadcast- or row-seeding. This paper discusses the development of a hill seeder and improvements in the lodging resistance of hill-seeded rice, both of which have contributed to the recent widespread cultivation of submerged, direct-seeded rice in Japan. The newly developed hill-seeder effectively drives seeds intermittently into the puddled soil and enabled establishment of a hill which is composed of several plants as is a transplanted hill. Hill-seeded rice showed remarkable higher pushing resistance than broadcast-seeded rice across a range of seedling density and seeding depth after heading, while the plant length was longer in hill-seeded rice. It is suggested that the high lodging resistance of the hill-seeded rice is derived from the larger number of panicles per hill, because the lodging resistance varied depending on the number of panicles in a hill. The area cultivated by hill-seeding has been increasing since 1998, in 2004, it occupied 25% of the total submerged direct-seeded area.