2006 Volume 75 Issue 4 Pages 443-450
In order to understand the effect of the time of nitrogen topdressing (panicle formation stage — 40 days after heading time) on the recovery rate of applied nitrogen and its distribution in rice plant, we examined the absorption rate of nitrogen fertilizer (ammonium sulphate) labeled with nitrogen (15N) in Hokkaido Kamikawa Agric.Exp.Stn. (Brown lowland soil). Nitrogen topdressed from panicle formation stage to 7 days after panicle formation stage was allocated to polished rice at a low rate, and did not affect the protein content of polished rice, although it increased the yield. Nitrogen application at the flag leaf stage increased the recovery rate and protein content of polished rice. A similar tendency was observed irrespective of the amount of basal dressing of nitrogen. Both the recovery rate of nitrogen and protein content of polished rice were highest when the time of topdressing from heading time to 10 days after heading time.Therefore, it is important to apply nitrogen topdressing within 7 days after the panicle formation stage to produce low protein content rice, and later nitrogen topdressing should be avoided.
