Paddy ecosystem is an important source of N 2 O emission, this paper is aimed to clarify

the effects of different nitrogen forms under different light intensities on N 2 O emission from rice phyllosphere and rhizosphere and the mechanism of these effects. 【Methods】Hydroponic methods with rice were adopted in small incubators in which the light was controlled. The incubators were separated into inner and outer chambers,and the above-ground part of rice was completely sealed in the inner chamber and the roots in the outer chamber.The N 2 O emissions from rice phyllosphere and rhizosphere were measured by gas chromatography method. It was firstly studied about the effects of three N forms (NO 3 – -N, NH 4 NO 3 -N, NH 4 + -N) on N 2 O emission of rice phyllosphere and rhizosphere under weak light (8:00–18:00, 4000 Lux) and same N applications (90 mg/L). Then the experiments were conducted to further study the effects of different N forms on N 2 O emission from rice phyllosphere and rhizosphere under different light intensities (weak light, 8:00–18:00, 4000 Lux;18:00–22:00, 0 Lux; strong light, 8:00–18:00, 8000 Lux, 18:00–22:00, 0 Lux and natural sunlight,

respectively).
【Results】 1) Under NO 3 – -N, NH 4 NO 3 and NH 4 + -N with weak light, the mean rates of N 2 O emission from phyllosphere and rhizosphere were 6.37, 5.03 and 0.46 μg/(pot·h), respectively, and 16.30, 15.71 and 1.31 μg/(pot·h), respectively, during rice tillering stage, and similar results were obtained during rice flowering, seeding and mature aging stages under the same conditions. 2) Under weak light, the N 2 O emissions from rice phyllosphere treated with NO 3 – -N, NH 4 NO 3 and NH 4 + -N were 10.47, 3.70 and 0.26 μg/(pot·h), respectively, and 20.83, 10.82 and 2.08 μg/(pot·h) with strong light, respectively, during flowering and seeding stages. There were significant differences in N 2 O emissions among the three N forms under these two light

intensities, but no significant difference in N 2 O emissions between NO 3 – -N and NH 4 NO 3 under the sunlight. 3) Under NO 3 – -N, NH 4 NO 3 and NH 4 + -N with the weak light during flowering and seeding stages, the N 2 O emissions of rice rhizosphere were 27.76, 5.19 and 0.30 μg/(pot·h), respectively. Under the strong light, the N 2 O emission

rates were 20.83, 10.82 and 2.08 μg/(pot·h), respectively, and 16.49, 20.21 and 1.74 μg/(pot·h), respectively, under the sunlight. The N 2 O emission from rhizosphere was high with high light intensity under NH 4 NO 3 . No significant difference was observed in the N 2 O emission between NO 3 – -N and NH 4 NO 3 under sunlight, but did

under weak light. 4) There was a significantly positive linear regression relationship between N 2 O emission from rice phyllosphere(Y) and rhizosphere(X) (Y = 1.963 + 0.444X, R 2 = 0.661, P < 0.01).
【Conclusions】The N 2 O emissions from rice phyllosphere and rhizosphere can be increased significantly by NO 3 – -N, followed by NH 4 NO 3 . The N 2 O emissions is also increased with the increase of light intensity. The N 2 O emissions of phyllosphere can reflect the N 2 O emissions of rhizosphere. Therefore, while applying N fertilizers, ammonium fertilizers should be preferentially used and nitrate nitrogen and fertilizers containing nitrate nitrogen should be avoided.