The effect of topdressing at ear formation stage on brown rice on the quality and crude protein content of brown rice [Oryza sativa]

To establish a growth control technology that enhances both the quality and the crude protein content of brown rice, we analyzed the effect of timing and the amount of the topdressing at ear formation stage on the quality and the crude protein content of brown rice, and determined the methods of topdressing at ear formation stage that would be most effective in 'Koshihikari' and 'Fusaotome'. 1. The percentage of white immature grains increased as the number of grams per square meter increased in 'Koshihikari' and 'Fusaotome'. In 'Koshihikari', the number of grains per panicle depended on the timing and the amount of the topdressing at the ear formation stage, and it influenced the percentage of white immature grains. In 'Fusaotome', however, the effect on the number of grains per panicle by topdressing at the ear formation stage was small. 2. The crude protein content of brown rice increased by topdressing at the ear formation stage at the later timing. The extent of the increase was larger in 'Fusaotome' than in 'Koshihikari'. In 'Koshihikari', the crude protein content of brown rice increased greatly by topdressing at heading time. However, in 'Fusaotome', the crude protein content of brown rice increased greatly 18 days before the heading time. 3. In 'Koshihikari', an increase in the number of grains on secondary rachis or branches by topdressing at ear formation stage at the earlier timing was shown to be a factor that increases the percentage of white immature grains. For 'Koshihikari', we should use topdressing at the ear formation stage, between 18 and 10 days before the heading time, and if the value of (number of stalks x leaf color value) is 20000 or more, we should decrease the amount of nitrogen used. 4. For 'Fusaotome', we should use topdressing at 25 days before the heading time, and if the value of (number of stalks x leaf color value) is 24000 or more, we should decrease the amount of nitrogen used.