2025 Volume 94 Issue 1 Pages 55-65
The effect of sowing time (mid-October, early November, and mid-November), seed production year and seed chemical treatment on emergence rate of the following spring were evaluated to clarify the early sowing limit for early-winter direct-sowing cultivation of rice in the Hokuriku region. Seeds of cultivar “Tsukiakari” and “Nijinokirameki” were sown in Joetsu City, Niigata Prefecture in early winter of 2021 and 2022. The emergence rates of the seeds produced the previous year and sowed in mid-October were less than 3% regardless of whether the seeds were smeared with thiuram hydrating agent. On the other hand, the emergence rate of the seeds produced the current year and sowed in the same period was 31-65%, and the rate was increased by treatment with thiuram hydrating powder. The emergence rate increased with the delay of sowing time. Seeds producedthe previous year, had the emergence rate of 36-62% when sown in mid-November, assuming low temperature storage at around 10°C and treatment of the seeds with thiuram hydrating agent. Differences in emergence rates depending on sowing time and seed production year were thought to be due to seed dormancy at the time of sowing. For the cultivars “Tsukiakari” and “Nijinokirameki” in each seed production year, the seeding amount for each sowing time and the early sowing limits based on the effective accumulated soil temperature and air temperature within the year werediscussed.
