水田・畑両条件下に於ける水稲及び陸稲の生育収量の比較

抄録

The study was begun in an effort to make clear the difference of growth and yield, especially dry matter and carbohydrate production, of paddy and upland rice crop grown under paddy-and upland-field conditions. A supplementary study of the effect of fertilizer and soil moisture contents was introduced into the experiment on the upland field plots. Experiments were carried out with paddy rice variety Fujisaka No. 5 and upland rice varieties Norin No. 12 and No. 21. The results obtained were as follows: 1. Among the factors which constitute rice yields, such factors which are determined by the time of heading as the number of ears, number of grains per ear were larger under the upland field condition than under the paddy field condition. And such factors which are influenced after heading as percentage of ripened grain, 1, 000-kernel weight were larger under the latter condition than under the former condition. 2. The ratio of the amount of carbohydrates stored by the time of heading to those of carbo-hydrates in the grain yields was higher under the upland field condition than under the paddy field condition. On the other hand, the ratio of the amount of carbohydrates produced after heading to those of carbohydrates in the grain yield was higher under the paddy field condition than under the upland field condition. 3. Therefore, the yield of upland rice grown under upland field condition was as high as that grown under paddy field condition because of their greater vegetative growth and larger amounts of carbohydrates stored by the time of heading, in spite of the low photosynthetic ability after heading. 4. Paddy ribe variety Fujisaka No. 5 showed higher photosynthetic ability than either of two upland rice varieties under both conditions after heading, thus resulted in approximately 11 per cent increase in its yield as compared with the yield of upland rice under the paddy field condition. But under the upland field condition the hulled rice yield of paddy rice was about 1, 000 kg. per hectare lower, representing an decrease of 22 per cent on the basis of the yield under paddy field condition, because of their poor growth by the time of heading. 5. At the high level of nitrogen supply, the photosynthetic ability of the both of paddy- and upland-rice after heading, was reduced, especially the reduction of the latter was remarkable. 6. In the unirrigated plot, the amount of the both carbohydrates stored by the time of heading and accumulated after heading in the grain were less. By the irrigation both of these increased, and the amount of non-reducing sugar was reduced remarkably. 7. The amount of growth of paddy rice variety Fujisaka No. 5 was smaller than that of the upland rice varieties under both condition, paddy-and upland-field. Especially under the latter condition, the ratio of the amount of carbohydrates accumulated by the time of heading and translocated to the grain to the total amount of carbohydrates in the grain was low even under irrigated condition. The content of non-reducing sugar was also low, showing that paddy rice suffered from the drought even under the soil moisture condition sufficient for upland rice growth.