2020 Volume 89 Issue 4 Pages 346-352
In recent years, the area of direct-seeded rice cultivation has been increasing, but the occurrence of volunteer rice has disturbed the spread of direct-seeded cultivation. Influence of multiple factors of combined cultural (existence of false seedbed, seeding methods, etc.) and chemical control on the transition of emerged and number of surviving plants was investigated to establish a system to control volunteer rice. Almost all “Tachisuzuka” and “Hinohikari” tested as volunteer rice emerged during the dry season. “Tachisuzuka” germinated slightly slowly, but the cumulative emergence rate of both species reached approximately 100% in early June. In 2017, the number of surviving volunteer rice in all treatments was significantly lower compared with the conventional dry direct-seeded cultivation practice. However, there was no significant difference among the seeding methods (full, partial, no plowing). Similarly, the effect of the mortality rate with high-concentration bispyribac-sodium application, which was expected to inhibit growth of rice seedlings, was low. In 2018, we examined the effects of soil compaction after seeding and preparation of false seedbeds; however, there was no significant difference in the number of surviving volunteer rice between treatments. The results of the two year study revealed that delayed seeding contributed to the reduction in the number of surviving volunteer rice more than false seedbed and bispyribac-sodium application.
