Variations of nitrogen nutrition efficiency in different rice germplasm types

Field experiment was conducted to investigate the variations of nitrogen absorption efficiency(NAE),nitrogen utilization efficiency(NUE) and nitrogen harvest index(NHI) in 607 rice germplasms(including conventional indica,japonica and hybrid indica combination rice).The results showed that genotypic differences of NAE,NUE and NHI obviously existed among these rice germplasms, with maximum coefficient of variation in NHI and minimum in NAE.There were not significant differences among conventional indica rice,conventional japonica rice and hybrid indica rice combinations,but the variations of NAE,NUE and NHI in hybrid indica rice combinations were lower than those in conventional indica and japonica rice.Correlation analyses indicated that the correlations of NAE to NUE and NHI in rice were very significantly negative,and the correlations of NUE and NHI to yield per plant were very significantly positive,but the correlations of NUE to NHI and NAE to yield per plant were not significant.The distributions of rice germplasms based on single NAE,NUE or NHI in conventional indica rice and NUE in hybrid indica rice combinations resembled typical normal curve, namely that low and high efficient germplasms were fewer and medium efficient germplasms were more.The distributions of rice germplasms based on single NAE,NUE or NHI in conventional japonica rice and NHI in hybrid indica rice combinations resembled normal curve approximately.The distributions of rice germplasms based on NAE in hybrid indica rice combinations were very sporadic and high efficient germplasms were more.Furthermore,the distribution of hybrid indica combinations was concentrative with small variation on NAE,NUE and NHI,but that of conventional japonica rice was much scattered.The ranges of NUE and NHI in three rice types were so large that they could be classified into some clusters.The differences among clusters were significant.