Dry Matter Production and Nitrogen Absorption of Japonica-Indica Hybrid Rice Cultivars Grown under Upland Conditions : A Comparison with Japonica Cultivers(Agronomy)

Japonica-Indica hybrid rice cultivars, Suweon 287 and Suweon 290, showed a high yield under the upland cultivation conditions as well as the lowland cultivation conditions. This study was conducted to elucidate the high yielding ability of the Japonica-Indica hybrid rice cultivars under the upland cultivation conditions through examination of dry matter production and nitrogen absorption in comparison with Japonica upland and lowland cultivars, Toyahatamochi and Koshihikari. Suweon 287 and Suweon 290 had a large leaf area index and large sink capacity, determined by the grain number and grain weight, which might be caused by the increased nitrogen absorption before anthesis. These cultivars showed a higher crop growth rate after anthesis mainly due to the high mean leaf area index during the ripening period. In addition, these cultivars showed relatively high net assimilation rates even though their high mean leaf area index during the ripening period. Therefore, it may be concluded that the Japonica-Indica hybrid rice cultivars have a high yielding capacity even under upland cultivation conditions. In 1994 which had a dry growing season in August, Suweon 287 and Suweon 290 showed higher photosynthetic rates under both insufficient and sufficient soil water conditions compared to the two Japonica cultivars, suggesting the high drought-resistance ability of these cultivars.