Studies of Protein Content in Rice Grain : V. Effects of topdressing of ammonium sulfate and foliar application at full heading time on the translocation of nitrogen to ears and the protein content of brown rice

[摘要] Using the 5 varieties grown on the field with sufficient nitrogen fertilizer as the basal dressing, we investigated the effect of nitrogen topdressing and foliar application of urea at full heading time on the translocation of nitrogen from the leaves and culms to the ears and the protein content of brown rice. 1. The amount of dry matter production increased 40% by topdressing and 36% by foliar application compared with non-topdressing on the average of 5 varieties. Most of the dry matter produced after full heading time was used for the increase of ear weight and a part of it was used for the increase of culm weight. The weight of leaves and leaf sheaths at harvest time was less than that of full heading time due to the translocation of dry matter, but the weight decrease of leaves and leaf sheaths, especially the former, was suppressed by topdressing of nitrogen and foliar application of urea. 2. The recovery rates of nitrogen applied at full heading time were 53∼73% on the topdressing plots and 74∼84% on the foliar application plots. The recovery rates of nitrogen on the foliar application plots were higher than those of the topdressing plots. 3. The distribution ratio of nitrogen to ears was about 50% of the nitrogen recovered on the topdressing plots and about 60% of the nitrogen recovered on the foliar application plots. 4. On the non-topdressing plots, 31∼38% of the nitrogen contained in the ears at harvest time was translocated from the leaf blades and 6∼10% from the leaf sheaths, and the nitrogen amount absorbed from the soil was 34∼49%. The translocation of nitrogen from the culms to the ears was little. On the topdressing plots, 9∼17% of the nitrogen of the ears at harvest time was translocated from the leaf blades and little or nothing from the leaf sheaths or the culms, and the nitrogen absorbed from the soil was 68∼76%. On the foliar application plots, the translocation of nitrogen from the other organs and the soil to the ears showed almost the same tendency as the topdressing plots. 5. The protein content of brown rice increased 23% by nitrogen topdressing and 48% by foliar application of urea at full heading tinle on the average of 5 varieties compared with the non-topdressing plots. The foliar application of urea was more effective than the nitrogen topdressing on the increase of protein of brown rice when the same amount of nitrogen was applied.

[学科分类] 农业科学（综合）