Variation of Nitrogen Use Efficiency in Rice Genotypes

This experiment was conducted to investigate the variation of nitrogen(N) uptake efficiency and their relationships with grain yield in the 34 rice genotypes. Significant differences among genotypes were observed in grain yield and N-uptake, efficiency and partitioning parameters as physiological N use efficiency [PNUE], agronomic N use efficiency [ANUE], apparent recovery [AR], partial factor productivity of applied N [PFPn], N harvast index [NHI]. The N-efficient genotypes that produced high grain yield at both low and standard level of N were BG90-2, Ilpumbyeo(MNU)77-3-GH1-3-3-3-2-1-3-3, Ilpumbyeo, and SR19616-B-B-35-3-3-1. 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 NHI and ANUE. The negative relationship implied a declining PNUE with increasing straw N content. The grain yield-N efficiency parameters for individual genotypes indicated significant differences in slope and in the yield obtained with soil N(GYo). Differences in GYo were due to genotypic variation in nitrogen efficiency parameters of use. NHI and ANUE were related to nitrogen use efficiency. The work also indicates that genotypes with NHI and ANUE are likely to perform well in different fertility conditions.