我国北方几种玉米和设施菜地土壤的N2O和N2排放特征

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。

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.