Nitrogen use efficiency in MR219-4 and MR219-9 rice mutant lines under different water potentials and nitrogen levels using 15N isotopic tracer technique.

This study was conducted to evaluate the nitrogen use efficiency of rice mutant lines of MR219, viz. MR219-4 and MR219-9, developed under rice radiation mutagenesis programme for adaptability to aerobic conditions, grown under conditions of varying water potentials and nitrogen levels in a shade house. Direct 15 N isotopic tracer method was used in this study, whereby the 15 N labeled urea fertilizer was utilized as a tracer for nitrogen nutrient uptake by the test crops. 15 N isotope presence in the samples was determined by using emission spectrometer analysis and percentage of total nitrogen was determined by using Kjeldahl method. 15 N atom access values of the samples were to determine the efficiency of N use by the mutant varieties. In this work, the data of yield components, viz. grain yield, plant biomass, plant height and 1000 grain weight, and nitrogen components viz, total N, % nitrogen derived from labeled fertilizer (% Ndff), % nitrogen derived from soil (% Ndfs), nitrogen uptake, fertilizer nitrogen use and nitrogen use efficiency were obtained. Results from this study showed a significant difference to the nitrogen component and yield when there is a change in the rate of fertilizer and water potential. However, varietal factor does not show any significant differences.