Yield Potential of High-Yield Rice Varieties in the Tohoku Region of Japan

概要

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To achieve a super high brown rice yield exceeding 10 t ha-1 in the Tohoku region (relatively cold), a two-year field experiment was conducted. The yield components, morphological traits and dry matter production among the Japonica type high-yield variety “Fukuhibiki,” indica type high-yield variety “Takanari,” large grain type high-yield variety “Bekoaoba” and two conventional Japonica type varieties were compared. Although the traits relating to high yield varied greatly, the three high-yield varieties all showed a large sink size, heavy rice yield at 30 days after heading (30 DAH) and a high harvest index. The effects of nitrogen application and planting density on the morphological traits, dry matter production and yield in the large grain type variety Bekoaoba were investigated. Although high nitrogen application (HN) increased the brown rice yield from 8 to 9.5 t ha-1, regulation of the timing of topdressing and/or planting density under HN could not increase the brown rice yield beyond 10 t ha-1. Strategies to achieve a super high-yield rice in the Tohoku region were discussed.