[Impact of different levels of nitrogen fertilizer on N2O emission from different soils]

To investigate the effect of different urea incorporation amount in different soils on N2O emission, a pot experiment was carried in 2002-2003. Four treatments were designed as the control (without urea incorporation); low N fertilizer level (334 kg/hm2); middle N fertilizer level (670 kg/hm); high N fertilizer level (1004 kg/hm2). In rice growing season, compared to control, the increment of N2O emission accumulation flux of each soil has no obviously differences among three N fertilizer levels. Contrarily, in wheat-planted soils, there are remarkably differences among three N fertilizer levels. Without urea incorporation, there are no differences among N2O accumulation emission flux of three soils. During the rice growing season, N2O accumulation emission flux of F soil (jiangsu province, lishui), G soil (jiangsu province, lianshui) and H soil (jiangsu province, agriculture academy) are 168, 127 and 146 mg/m2, respectively. N2O accumulation emission flux of F soil, G soil and H soil is 134, 124 and 168 mg/m2, respectively, during wheat growing season. Incorporation of urea into different soils yielded different influence on N2O emission. For example, at middle-N fertilizer, N2O accumulation emission flux from F soil, G soil and H soil is 976, 744 and 626 mg/m2, respectively. During rice-wheat rotation period, significance differences exists among N2O emission factors of three soils, with the value of (1.1 +/- 0.23)%, (0.75 +/- 0.17%) and (1.01 +/- 0.11)%. Furthermore, under the high N fertilizer level, N2O emission factors of three soils had no significantly difference (p = 0.3); while, the N2O emission factors existed difference among three soils under the low and middle N fertilizer level (F = 6.25, p = 0.01).