Abstract: We conducted a field experiment to obtain high yield and high recovery of N fertilizer simultaneously through regulating carbon and nitrogen metabolism under suitable planting density in 2006. The main results showed that plants grew well under low or medium densities [9.75×104 (D_1-1) and 11.25×104 (D_1-2) plants ha-1 for CF008; 8.25×10⁴ (D_2-1) and 9.75×10⁴ (D_2-2) plants ha^-1 for Zhengdan 958; and 6.75×10⁴ (D_3-1) and 8.25×10⁴ (D_3-2) plants ha^-1 for Jinhai 5]. Although C and N accumulation in stem/sheath and leaf at silking stage and C and N translocation rate were higher under medium or high density than under low density, grain yield, N uptake efficiency, N use efficiency, and recovery of N fertilizer were significantly higher under low or medium densities. N accumulation in shoots before silking was higher under medium or high density than under low density, N in shoot accumulation at maturity and N in grain were higher under low or medium density. Hence N accumulation in shoot after silking stage was important for grain N accumulation. We also obtained some quantitative criteria based on the research in Wuqiao area: for the three varieties of maize, grain yield was 10 262–11 461 kg ha^-1, recovery of N fertilizer was 23.00%–34.11% under low or medium densities.

Key words: Summer maize (Zea mays L.), Density, Metabolism of carbon and nitrogen, C/N ratio, Recovery of N fertilizer