Use of optical spectrograpiuc 15N-analyses to trace nitrogen applied at tile heading stage of rice

In the recent decades experimental work has led to the accumulation of vast quantities of valuable data on mineral nutrition of plants through the use of isotopic tracers. However, only limited research has been done with nitrogen presumably because of the high costs of instrumentation and isotopes. A few Investlgatlons on the distribution and accumulation of nitrogen have been reported using mass spectrographic method. For example, Ozaki et al. (1) observed a larger distribution of ammonical nitrogen administered before heading, Into ears, culms, and boot leaves in contrast with other plant parts. They further noted that 35% of the nitrogen applied after heading was found in the ears (2).