Differences in Nitrogen Absorption and Use Efficiency in Rice Genotypes with Different Yield Performance

【Objective】 The objective of this study was to identify the differences in N absorption and use efficiency in rice genotypes with different yield performances. 【Method】 A field experiment was conducted with 20 rice genotypes(10 high-yielding and 10 low-yielding performance) selected from 108 rice genotypes including early (125-135 d,growth duration),medium (136-145 d) and late-maturing (146-155 d) medium japonica and early (156-165 d) and medium-maturing (166-175 d) late japonica rice under 225 kg·hm-2 N fertilizer application in 2006 and 2007 on the farm of Yangzhou University,Jiangsu province,China. Yield,N accumulation,N uptake rate,N use efficiency and their relationship were analyzed. 【Result】 The results showed that the mean yields of high-yielding rice genotypes were 31.6%,31.94%,39.47%,26.21%,and 21.82% higher than those of low-yielding rice genotypes,respectively,with the extension of the growth duration. N accumulation and use efficiency increased with the extension of the growth duration,and which of high-yielding genotypes was significantly higher than those of low-yielding genotypes. N accumulation and uptake rate of high-yielding genotypes were higher than those of low-yielding during the growth phases from transplanting to elongation and from elongation to heading,while it showed a reversed trend during the growth phase from heading to maturing for some genotypes. Correlation analysis indicated that there existed significant or highly significant positive correlations between yield and N accumulation,N use efficiency,N uptake rate during the growth phase from transplanting to elongation. 【Conclusion】 Compared with the low-yielding rice genotypes,N accumulation in various growing stages,N uptake rate before heading and N use efficiency of high-yielding rice genotypes were higher. It was obvious that high yield and increasing N accumulation and use efficiency could be coordinated development on improving genotype.