Abstract:

【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.

Key words: rice, N accumulation, N uptake rate, N use efficiency, genotype, yield performance