Growth characteristics of submerged hill-seeded rice (Oryza sativa L.) in warmer regions of Japan - Difference of growth as compared with broadcast-seeded rice [Japanese]

摘要

The growth characteristics of hill-seeded rice were compared with those of broadcast-seeded rice to establish the submerged direct seeding cultivation using a newly developed 'Shooting hill-seeder'. The hill-seeded rice suffered from severe growth competition among individuals at an earlier growth stage, and showed a decrease in tillering and dry matter production until the maximum-tillering stage. The nitrogen uptake at the panicle-initiation stage was higher in hill-seeded rice, because the growth reduction at the early growth stage resulted in higher nitrogen content during the period between maximum-tillering and full-heading stage. However, a higher nitrogen uptake did not increase the number of spikelets in hill-seeded rice because of a greater decrease in the nitrogen content during the period between maximum-tillering stage and panicle-initiation stage as compared with that in broadcast-seeded rice. Furthermore, in the hill-seeded rice, a higher LAI at the maturing stage and higher photosynthetic rate due to higher nitrogen content of leaf blade at the full-heading stage seemed to result in an increase of dry matter production during the ripening period. These results suggest that the number of spikelets is increased by the improvement of nitrogen application resulting in an increase in yield of hill-seeded rice.