关键词: 旱地农田, N₂O背景排放, N₂O排放系数, 氮肥用量, 硝化抑制剂, 缓控释肥

Abstract: 【Objective】Published literatures regarding to N₂O emissions from upland fields in China were collected to establish a dataset. The established database was used to analyze the N₂O background emissions (emission from soil without fertilization), emission factors (EFs) and associated factors influencing the N₂O emissions from major upland fields (for example wheat fields, maize fields and vegetable fields) in China. The results will provide supports for estimating regional N₂O emission inventory and provide appropriate mitigation strategies.【Method】Subgrouping analysis and regression analysis were used to analyze the factors which influence N₂O background emissions (for example the soil nitrogen content and C﹕N ratio of the soil) and EFs (for example the nitrogen application level and fertilizer types such as nitrification inhibitors and slow release or controlled release fertilizers).【Result】(1) The N₂O background emissions from upland fields ranged between 0.70 and 3.14 kg N₂O-N·hm^-2. Either N₂O background emissions from wheat and summer maize fields or daily N₂O background emissions from vegetable fields increased with increasing soil total N (TN) while decreased with the increasing of soil C﹕N ratio. Irrigation could promote the N₂O background emissions from wheat fields. (2) EFs increased with increasing N application rate and its value was ranked in the following order: vegetable fields (0.56%-0.61%)＞summer maize fields (0.50%-0.68%)＞spring maize fields (0.35%-0.40%)＞wheat fields (0.22%-0.36%). EFs from summer maize fields were two times higher than those from wheat fields. (3) Nitrification inhibitors could decrease N₂O EF by 34%-60% ranking in the order: DCD+HQ (58.9%)＞NBPT+DCD (52.9%)＞DMPP (51.1%)＞NBPT (44.1%)＞Pyridine (39.5%)＞DCD (38.9%). The effects of different nitrification inhibitors on EF decline were varied in different fields ranking in the order: wheat fields (60.0%)＞vegetable fields (50.6%)＞spring fields (39.6%)＞summer maize fields (34.7%). (4) Compared with normal urea, slow release or controlled release fertilizers decreased EF to an extent between 15.9% and 79% ranking in the order: long-effect ammonium bicarbonate (78.9%)＞Polymer-coated urea (59.8%)＞Urea formaldehyde (53.4%)＞Resin-coated urea (44.9%)＞Sulfur-coated urea (30.6%)＞Calcium-magnesium-phosphate-coated urea (15.9%). The decline effects of different slow release or controlled release fertilizers on decreasing EFs varied in different fields ranking in the order: vegetable fields (78.4%) ＞spring maize fields (58.2%)＞winter wheat fields (49.2%)＞summer maize fields. The effect of slow release or controlled release fertilizers on decreasing EFs were lower in summer maize fields than in other croplands.【Conclusion】N₂O emissions are influenced by many factors including soil properties (i.e. soil TN content and C: N ratio), management practices (i.e. irrigation and fertilization) and other factors. In order to reduce N₂O emissions, it is critical to take appropriate practices specific to oriented climate, soil and cropping regimes and combined with appropriate rational nitrogen fertilizer application rate and type.

Key words: upland fields, N₂O background emission, N₂O emission factor, amount of nitrogen fertilizer, nitrification inhibitor, slow/controlled release fertilizer