Growth Enhancement by Drainage during Seedling Establishment in Rice Direct-Sown into Puddled and Leveled Soil: —Comparison with seed coating with calcium peroxide—

Growth enhancement by drainage during seedling establishment was compared with seed coating with calcium peroxide in rice direct-sown into puddled and leveled soil. Coated and noncoated seeds were sown about 10 mm deep, three times from April to June at two locations (Niigata and Ibaraki, Japan). Seed coating with calcium peroxide accelerated seedling emergence at an early stage, whereas drainage during 10 to 13 days after sowing promoted it at a late stage. Although drainage was less effective in increasing the number of finally emerged seedlings than seed coating with calcium peroxide, the drainage clearly improved seedling establishment. Seed coating with calcium peroxide enhanced shoot elongation during seedling emergence. In contrast, drainage somewhat inhibited shoot elongation at this time, but promoted it after drained soil was flooded. Drainage also increased the dry weight of shoots more than flooding after seedling emergence. These results indicate that seed coating with calcium peroxide enhances plant growth during seedling emergence, whereas drainage after sowing promotes plant growth mainly after seedling emergence. This suggests that seed coating with calcium peroxide accelerates seedling emergence, but drainage after sowing enhances seedling establishment