[N2O and N2 emission characteristics from maize and greenhouse vegetable soils in Northern China].

To explore N2O and N2 emissions from upland soils after nitrogen fertilizer application, a 60-day aerobic incubation experiment (25 ℃,80% water-filled pore space) using the 15N tracing method was conducted to quantify the N transformation, N2O and N2 emissions from maize soils from four sites (Harbin, Shenyang, Luancheng and Shouguang) and vegetable soils from two sites (Shen-yang and Shouguang), with urea being applied at 167 mg N·kg-1 to simulate the field application rate of 200 kg N·hm-2. The results showed that for the four sites with maize soils, the cumulative emission of N2O was in the order of Shouguang (20 mg N·kg-1) > Luancheng (14 mg N·kg-1) > Shenyang (5 mg N·kg-1) > Harbin (0.5 mg N·kg-1) and the cumulative N2 emission was in the order of Luancheng (176 mg N·kg-1) > Shenyang (106 mg N·kg-1) > Shouguang (75 mg N·kg-1) > Harbin (12 mg N·kg-1). For vegetable soils, the cumulative N2O emission of Shouguang (21 mg N·kg-1) was 10 times of that of Shenyang (2 mg N·kg-1), but without differences in cumulative N2 emissions (28 and 24 mg N·kg-1, respectively). The N2O/(N2O+N2) of the six soils ranged from 5% to 40%. The N2O/(N2O+N2) of the two soils from Shouguang (30%-40%) was significantly higher than other four soils (1%-10%). Soil bulk N pool contributes to 56% of total N2O emission and 61% of total N2 emission, which was higher than the contribution of fertilizer. The cumulative N2O emission was positively correlated with soil background pH, which indicated that soil background pH might be an important factor regulating N2O and N2 emission from upland soils. In the alkaline soil regions of North China Plain (such as Luancheng and Shouguang), mea-sures to reduce soil pH might have great impact on reducing N gaseous emission.为了探究旱地土壤施入氮肥后的气态氮(N2O和N2)损失规律,本研究通过室内好氧培养试验(60 d,25 ℃,80%孔隙含水量),运用15N同位素示踪技术,研究了4个玉米地土壤(哈尔滨、沈阳、栾城、寿光)和2个设施菜地土壤(沈阳、寿光)在施入尿素后的氮转化、N2O和N2排放动态。试验中尿素添加量为167 mg N·kg-1,以模拟田间氮肥施用量200 kg N·hm-2。结果表明: 在4个玉米地土壤中,尿素施用60 d内N2O累积排放量为寿光(20 mg N·kg-1)>栾城(14 mg N·kg-1)>沈阳(5 mg N·kg-1)>哈尔滨(0.5 mg N·kg-1),N2累积排放量为栾城(176 mg N·kg-1)>沈阳(106 mg N·kg-1)>寿光(75 mg N·kg-1)>哈尔滨(12 mg N·kg-1);在2个设施菜地土壤中,寿光土壤N2O累积排放量(21 mg N·kg-1)是沈阳(2 mg N·kg-1)的10倍,而两个站点N2累积排放量分别为28和24 mg N·kg-1。不同土壤N2O排放占两种气体排放总量的5%～40%,其中寿光土壤(30%～40%)显著高于其他样地土壤(1%～10%)。在土壤排放的N2O和N2中,土壤氮库分别贡献了56%和61%,高于添加当季氮肥的贡献率。相关分析表明,N2O累积排放量与本底土壤pH呈正相关,说明土壤本底pH可能是调控不同旱地土壤N2O和N2排放的重要环境因子。在华北碱性土壤区,采用能降低土壤pH值的措施可能具有较好的气态氮减排效果。.