Abstract
Appropriate and effective nitrogen (N) use is an important factor to realize the sustainable rice production and to avoid environmental pollution. In this study, the low N conditions were induced by two different treatments; the restricted supply of N fertilizer by soil culture and the sudden depression of N by water culture. The growth responses of eight varieties of indica rice to low N supply were analyzed using fundamental growth parameters and specific nitrogen utilization rate (NUR) . The relative growth rate (RGR) was generally higher in the local varieties than improved varieties in both experiments. The net assimilation rate (NAR) showed a close correlation with RGR, whereas the specific leaf area and leaf weight ratio did not. A highly positive correlation was found between RGR and NUR. Among the local varieties, Pokkali showed the highest RGR, NAR and NUR in both experiments. These results indicated that under low N supply, the growth rates of the local varieties were higher than those of the improved varieties due to their higher NAR and NUR.
