[Effect of free-air CO2 enrichment (FACE) on nitrogen accumulation and utilization efficiency in rice (Oryza sativa)]

Effect of FACE, 200 mumol.mol-1 CO2 elevation under field condition in this study, on nitrogen accumulation and nitrogen use efficiency in rice was investigated. Results showed that nitrogen content (%) in rice plant sampled at different growth stages decreased significantly under FACE treatment, but FACE had no obvious effect on nitrogen accumulation in rice plant due to the significant enhancement in dry matter production. FACE treatment resulted in the significant increase in nitrogen use efficiency for biomass production (NUEp) which was measured at 28th day after transplanting, at heading and at maturity, respectively. Significant increase in nitrogen use efficiency for grain output (NUEg) and nitrogen harvest index (NHI) under FACE treatment was also observed in this study. Nitrogen content (%) and nitrogen accumulation in rice plant were increased under high N, but nitrogen use efficiency in rice plant were decreased.