Effects of application timing of top-dressed nitrogen and shading treatments on nitrogen-use efficiency on the grain number and protein content of milled rice
1998
Fujii, H. (Yamagata-ken. Agricultural Experiment Station (Japan)) | Ando, H. | Matsuda, H. | Shibata, Y. | Mori, S. | Kominami, C. | Hasegawa, S.
To clarify the effect of nitrogen (N) cultural practices on N-use efficiency for the total number of grains produced per amount of N in a plant heading (NUE for G/N), a field experiment was carried out. Furthermore, the effects of translocation of top-dressed N applied at different dates and the amount of total available carbohydrate (TAC) in the plant at heading on the protein content in milled rice was evaluated. The results obtained were as follows: 1) No significant differences were observed in the number of differentiated grains among the application times of top-dressed N and shading treatments. However, the number of degenerated grains was affected by both top-dressed N timing and shading. A delay in the application date of top-dressed N and increase of shading percentage resulted in an increase in the number of degenerated grains. 2) Nitrogen-use efficiency as affected by the date of N application (day before heading, DBH) was higher in the order of 26 DBH 19 DBH 16 DBH 9 DBH 5 DBH. Furthermore, increasing the shading percentage decreased N-use efficiency. 3) Delaying the date of top-dressed N induced the reduction of N-use efficiency and an increase in the amount of N per grain, resulting in an increase of protein content in the milled rice. The protein content of milled rice was also affected by the amount of N derived from top-dressed N, which was governed by application timing. 4) The low NUE for G/N controlled by shading treatment resulted in an increase in the amount of N in grain and in the protein content of the milled rice. The amount of TAC in a plant at heading, as regulated by shading treatment, affected the protein content through grain weight
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