Analysis of Yield-Determining Process and Its Application to Yield-Prediction and Culture Improvement of Lowland Rice : XCII. Possibility of increasing yield and nutritional value of rice protein by nitrogen dressing

Abstract

In the previous paper, it was found that top dressing with nitrogenous fertilizer at full heading stage increases their percentage of ripened grains and results in an increase in yield. On the other hand, it is known that the protein content of rice is increased by the application of nitrogenous fertilizer after heading stage. Based on those results, the present experiments were carried out to prove the possibility of increasing the protein yield and the nutritional value of rice by nitrogen dressing. Basal dressing and top dressing at panicle formation stage did not always affect the total nitrogen content ( : protein content) but top dressing at full heading stage increased the total nitrogen content by 15∼30 per cent. In the case of increasing not only the total nitrogen but the grain yield by top dressing at full heading stage, the total nitrogen yield was greatly increased by the interaction. With respect to a given quantity of top dressing after full heading stage (2∼8 Ng/m2), it was shown that the more the fertilizer applied, the more the total nitrogen content was increased. When an identical amount of the dressing was applied in the period from full heading stage to 30 days after it, it was the more effective at the nearer stage to full heading. The total nitrogen was less in milled rice than in brown rice and the decreasing rate of total nitrogen by milling was lower in the brown rice of high total nitrogen content increased by top dressing at full heading stage. This finding indicates that the increased protein is stored in the endosperm. The total nitrogen content in both the brown and the milled rices showed negative correlations with lysine and methionine contents to 16g total nitrogen but positive correlations with lysine, threonine and methionine contents on dry matter. As the results, it is presumed that top dressing at full heading stage serves to increase the protein content and the nutritional value of rice, and also the protein yield in case of the percentage of ripened grains being increased.