Studies on Protein Content in Rice Grain : IV. Varietal differences of the effect of nitrogen top-dressting at full heading time on the protein content of rice

Abstract

lt is known that the protein content of rice is increased by the nitrogen top-dressing at full heading time. The present experiments were carried out to clarify the varietal differences of the effect of nitrogen top-dressing at full heading time on the protein content of rice. Twenty varieties used in the experiments are those being cultivated or having been cultivated in Tohoku and Hokkaido districts. The summary of the results is shown below. 1. The protein content of brown rice of the varieties used in the experiments increased 8∼24 percent compared with that of the control (non top-dressed) plot by nitrogen top-dressing at full heading time. 2. The protein percentage of brown rice showed the positive correlation with the nitrogen percentage of the leaf blade at full heading time on the control plot and with the nitrogen percentage of the leaf blade at 10th day after top-dressing on the treatment plot. The protein percentage of brown rice showed the negative correlation with the nitrogen percentage of the leaf blade at the time of harvesting regardless of top-dressing. These facts seem to suggest that the better the translocation of nitrogen from the leaf blade to the ear, the higher the protein percentage of brown rice. 3. It is assumed that the difference among varieties of the increasing of protein percentage of brown rice by the nitrogen top-dressing at full heading time is rather due to the difference of distribution ratio of nitrogen to the ear than the difference of the amount of nitrogen absorbed.