Characteristics of N utilization efficiency in different rice genotypes in Jiaxing area

To further understand characteristics of nitrogen( N) utilization efficiency in different rice genotypes with varied grain yields,which would be helpful for the breeding of rice cultivars with higher N use efficiency,field experiments were conducted in Jiaxing City,Zhejiang Province. Grain yield,N accumulation,N translocation efficiency and amount,N physiological use efficiency of 10 rice cultivars in 3 study sites were analyzed. The results showed that rice grain yield and other indexes related to N utilization properties among rice cultivars were significantly different in each study site. The same results were also found among 3 study sites for each rice genotype. Furthermore,rice cultivars had significant interaction with study sites. There were significantly( P 0. 01) positive relationship between grain yield and total N accumulation during periods of whole growth stage and heading stage,and N redistribution amount,as well as N physiological use efficiency. N physiological use efficiency showed significantly( P 0. 01)negative correlation with N accumulation at tillering,heading and mature stages obviously. However,N redistribution efficiency and redistribution amount had significantly( P 0. 01) positive relationship with N physiological use efficiency. Therefore,rice with larger amount of N accumulation might appear lower N physiological use efficiency,al-though it might increase N uptake efficiency. Increasing N redistribution efficiency and amount after rice heading stage would be favorable for higher N physiological use efficiency.