0023-6152

AA00697606

9228

査読無

0023-6152

AA00697606

Field studies were on a commerce silt loam soil in a paddy field using three soybean (Glycine max L.) cultivars Pungsan-namulkong, Sobaeg-namulkong and Saebyeolkong of determinate growth type, which have different productivity. The flood duration was done for 3, 5, 7 and 9 days, respectively when plants were at the vegetative (V5 to V6) stages filled with tap water to 2 cm above the level of the soil surface by irrigation. After removal of flooding, photosynthetic rate reduced in all flooding treatments except for 3 days’ flooding. Reduction of photosynthetic rate was relatively lower in Saebyeolkong than any others. The number of pod and seed decreased as much as the flood period was prolonged. There was a significantly positive relationship (R^2＝0.50, p＜0.01) between the ratio of seed yield on branch stem against that on main stem and the seed yield of three soybean cultivars treated with flooding. Also, the relationship between the seed yield and the relative yield of the flooded soybean to non-flooded one had a high positive significance, and there was more significant difference in relative yield of branch stem (R^2＝0.91, p＜0.01) than that of main stem (R^2＝0.88, p＜0.01). From these results, it was ascertained that the high yield soybean cultivar (Saebyeolkong) under the upland field condition (Cho et al., 2005) has the highest ability of productivity under the paddy field condition in the rainy season. From above results, the accumulation of biomass was considerably reduced by longer exposure of soybeans against flooding. Flooding stress was also decreased in the photosynthesis and the seed yield of soybeans. The seed yield was remarkably reduced from flood duration of 3 days. That is, a critical day for drainage after flooding might be 3 days.