[Effects of free-air CO2 enrichment on phosphine emission from rice field]

Phosphine, a trace gas, has been proved to commonly exist in environment. Under free air carbon dioxide enrichment (FACE) condition, the phosphine fluxes were investigated on the function of different nitrogen fertilizer application, NN (normal N, 250 kg/hm2) and LN (low N, 125 kg/hm2). Results showed that phosphine fluxes and concentrations in flourishing stages, both tillering stage and elongation stage, were higher than in slowly growing stages. The highest phosphine flux of (155.2 +/- 22.71) ng/(m2 x h) was observed in tillering stage in NN zone of the FACE area. The highest average phosphine flux of (41.72 +/- 7.006) ng/(m2 x h) was observed in NN zone of FACE area, while the lowest average phosphine flux of (- 1.485 +/- 6.229) ng/(m2 x h) could be detected in LN zone of the ambient area. CO2 enrichment can obviously improve the phospine emission. The nitrogen fertilizing level doesn't play an important role in phosphine emission. Both net fluxes and concentrations of phosphine had obviously positive correlation with temperature. A one-day phosphine flux and concentration experiment was carried out in ripening stage. The result showed that light was the prominent factor influencing phosphine concentration in daytime.