Abstract
The effect of temporally high N application was investigated to develop the fertilization method that increases N content per leaf area (NCLA) without the increasing of specific leaf area. The change of N content in seedlings treated with high N concentration (230, 1150, 2300, 4600, 11500 and 23000 ppmN) for 12-24 hours, the effect of this treatment prior to transplanting on the growth after transplanting and the yield were analyzed. The result showed that 2300 ppmN 12 hours treatment did not affect leaf thickness, but increased NCLA by 40%. Seedlings treated with this treatment and transplanted at lower level of basal dressing showed remarkable acceleration of net assimilation rate, relative growth rate (RGR) and relative leaf growth rate. From the result of field trial under lower level of soil fertility condition, varietal differences were found in effect of this treatment, dry matter increased by 5-90%, tiller number increased by 10-90% at the early stage of the growth. However, the effect of this treatment was not found in plant length of all varieties used. It was considered that this treatment affected the growth directly for 3 weeks, based on the change of RGR. Moreover, increased tillers were lower order ones which were to be productive culm, clearly, the increasing of tiller number induced yield increase through the increasing of spikelet number per hill.
