抄録
Writers intended to find a method which determines the most adequate amount of nitrogen to be given to rice plants in a paddy field condition. If we made a graph (for example, as shown in Fig. 4) which shows tne relation between the amount of the grain produced at a given amount of nitrogen and the percentage content of nitrogen in the grain, from which it will be recognized , that there exist two stages. In the first stage the yield of rice grain increases with the increase of the nitrogen supply (from 0 to 50 kg N per Acre), but the nitrogen content of the grain remains comparatively constant (about 1.0%). In the second stage, that is, in the case of heavy dressing (more than 56 kg N per Acre), the yield of grain remarkably decreases, but on the contray, the nitrogen content remarkably increase. So we concluded that the point of inflexion from the first stage to the second denotes the most adequate amount of nitrogen to be given to rice plants in a paddy field condition. Thus, in this research we have obtained, by the recognition of these two stages described above, the following result : a) The highest yield is obtained at the dressing of 50 kg. N per Acre. In this case, the amount of nitrogen in grain is 1.05%. b) But the degree of economic utilization of nitrogen is highest in the case of l7 kg. N per Acre. c) The amount of protein in polished rice is increased according to an increase of the amount of nitrogen given as fertilizer. This increase will be attributed to an increase of NaOH soluble ptotein (Oryzenin).
