Effects of the amount of seed coating with oxygen-generating products on the seedling establishment of submerged direct-seeded rice (Oryza sativa L.) in Tohoku Region

Abstract

In submerged direct-seeding of rice cultivation, the drainage after seeding contributes to stabilization of seedling establishment and the amount of oxygen generating products (Calper Fine Granule, simply called "Calper" hereafter) for seed coating is decreasing in recent years. In this study, we analyzed the data collected in Tohoku region and examined the relationship between the amount of Calper for seed coating and the rate of seedling establishment under a drained condition after seeding. The rate of seedling establishment was lower without Calper coating than with coating even when the field was drained after seeding. On the other hand, when the amount of Calper coating was decreased to half of the standard (equivalent to dry-seed weight), the percentage of seedling establishment was reduced only slightly (4%), but it was significantly reduced under low temperature conditions compared with the standard Calper coating (double the dry-seed weight). Thus, it is necessary to consider the amount of Calper coating and seeding time, when the low temperature condition at the seedling emergence period is anticipated. Furthermore, the application of the technique to promote seedling emergence is also important for stabilization of seedling establishment at low temperature conditions.