Abstract
In cold climates, when seeds are sown directly in flooded paddy fields during the low temperature, the final rates of seedling emergence and establishment are decreased compared with warmer climates. Seeding at low temperatures also decreases the yield because of reduced plant growth. The early sowing limits for emergence and establishment of seeds in cold climates have been estimated using daily mean temperature. However, it is also necessary to estimate the early sowing limits under site-specific weather conditions. In this study, we calculated the early sowing limits for direct seeding of paddy rice at different points in the Hokuriku region using Automated Meteorological Data Acquisition System (AMeDAS) weather data and the Arrhenius equation. The goal was to help establish the direct seeding technique in Hokuriku by clarifying the conditions under which stable seedling emergence can be ensured. The results indicated that the early sowing limits of seeding calculated by the daily mean temperature differed from that calculated by the daily temperature range. Moreover, the early sowing limits tended to be earlier in inland areas, except at high altitudes, than in coastal areas.
