Emergence Rate, Growth and Yield of Rice Cultivated by Early-winter Direct-sowing Using Rotary-tilling Fertilizer Application and Sowing Machine in the Aomori Tsugaru Area

Early-winter direct-sowing cultivation (EDC) is a cultivation method of sowing rice before the ground is covered with snow. We examined a management method to increase the emergence rate in EDC using rotary-tilling fertilizer application and a sowing machine in the Aomori Tsugaru area. In addition, the growth and yield were compared with conventional spring direct-sowing cultivation (CDC) in the 2018 and 2019 seasons. The snow-covered period was 120 days in 2018 and 69 days in 2019. The germination rate of the seeds collected from the field after the snow melted ranged from 55% to 88%, and tended to be lower in 2018 than in 2019. There was no significant difference between one-tilling without pre-tilling and two-tilling with pre-tilling. The emergence rate ranged from 29% to 60%. Setting the sowing machine to a seeding depth of 1 cm rather than 3 cm reduced the number of deeply sown seeds and increased the germination rate. Tamping soil in spring also improved the germination rate by 12%. The heading stage was 2 to 6 days earlier in EDC than in CDC. Under the conditions of surface fertilization during the budding season, there was no significant difference in yield between EDC and CDC. In simultaneous fertilization of sowing, EDC had fewer number of ears and lower yield than CDC. When supplied with additional fertilization, the number of paddies and yield were similar in EDC and CDC.