| Co-Investigator(Kenkyū-buntansha) |
MATSUI Tsutomu Kyoto University, Graduate School of Agriculture, Instructor, 農学研究科, 助手 (70238939)
INOUE Hiromo Kyoto University, Graduate School of Agriculture, Instructor, 農学研究科, 助手 (40260616)
INAMURA Tatsuya Kyoto University, Graduate School of Agriculture, Associate Professor, 農学研究科, 助教授 (00263129)
YAMAMOTO Takuji The Nara Prefectural Agricultural Experiment Station, Researcher, 主任研究員
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| Research Abstract |
(1) In 3 experimental sites (Sichuan Province China, Kyoto and Nara) of which the mineralization soil nitrogen level differed, the effect of the soil nitrogen fertility on the spikelet productivity was investigated. Mineralized soil nitrogen level in China was higher than Kyoto and Nara. The nitrogen uptake from soil and its' effect on the spikelet productivity was high in China than Kyoto and Nara.
(2)The growth characteristics of paddy rice were evaluated in rotational paddy field (RPF) and continuous paddy field (CPF) at Sakurai, Nara, in 1998-2000. Without N fertilizer application, biomass production, yield and N uptake of rice were generally higher in RPF than in CPF. It seemed that greater nitrogen release from soil in RPF caused this increase. However, soil drying effect for N mineralization, often expected in RPF, was not observed in this study, and the total amount of mineralized N from soil (SMN) was greater in CPF. We concluded that higher N uptake observed in RPF could be explained by 1) greater N contribution from subsoil, 2) higher recovery rate of N, compared with CPF.
(3)The varietal differences in the response to atmospheric humidity were examined using japonica and indica variety. Under low humidity, as compared to the indica varieties, the japonica varieties had a higher stomatal density, longer stomatal and longer stomatal aperture, resulting in a lower water potential in leaf blades and lower water-use efficiency. Under high humidity, the japonica and indica varieties showed a similar transpiration rate, stomatal aperture and water-use efficiency. These differences between the japonica and indica varieties in morphophysiological characters under low humidity might cause the varietal differences in the plant growth and dry matter production in rice.
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