Abstract:A pot experiment was conducted to study the differences in rice plant biomass, N accumulation, N use efficiency, glutamine synthetase activity (GSA) and nitrate reductase activity (NRA) of paddy soil derived from red soil under different fertility levels at 40, 50 and 60 days after sowing. The results showed that the fresh and dry weights of rice plant under high fertility condition were significantly higher than those under low fertility condition, especially for the root biomass. High soil fertility increased rice root numbers significantly, but showed no significant effect on the root/shoot ratio. The rice N accumulation, NRA and GSA were significantly improved under high fertility soil conditions, which showed that high soil fertility increased rice N accumulation and assimilation significantly. High soil fertility increased the rice N use efficiencies but resulted in no statistically significant difference. In summary, appropriate amelioration for the paddy soil fertility was of important strategic significance for rice growth and nitrogen nutrition in tropical and subtropical China.