Genotypic Differences in Nitrogen Uptake and Utilization for Grain Yield of Rice

A field experiment was conducted to investigate the variation of nitrogen(N) use efficiency, nitrogen uptake efficiency, and their relationships with grain yield in 34 rice genotypes. Significant differences among genotypes were observed in grain yield, N uptake, total dry matter (TDM), and harvest index (HI). The N-efficient genotypes that produced high grain yield at both low and standard levels of N were, Ilpumbyeo(MNU)77-GH1-3, Ilpumbyeo, and SR19616-2B-34-3. Inefficient genotypes that produced low yields at low N level but responded well to N application were Yangjobyeo and Milyang182. Palawan was N-inferior genotypes giving low yields at both and standard levels. Increase in grain yield was highly correlated with N uptake (r² = 0.65***) and TDM was also similarly correlated with N uptake. The grain yield-N uptake relationship for individual genotypes indicated significant difference in slope and in the yield obtained with soil N (GY0). Differences in GY0 were due to genotypic variation in N uptake and efficiency of use. HI was related to both grain yield and TDM.