我国北方几种玉米和设施菜地土壤的N_(2)O和N_(2)排放特征

N_(2)O and N_(2) emission characteristics from maize and greenhouse vegetable soils in Northern China

为了探究旱地土壤施入氮肥后的气态氮(N_(2)O和N_(2))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^(15)N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、N_(2)O和N_(2)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N_(2)O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)),N_(2)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N_(2)O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N_(2)累积排放量分别为28和24 mg N·kg^(-1)。不同土壤N_(2)O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N_(2)O和N_(2)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,N_(2)O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N_(2)O和N_(2)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。

To explore N_(2)O and N_(2)emissions from upland soils after nitrogen fertilizer application,a 60-day aerobic incubation experiment(25℃,80%water-filled pore space)using the^(15)N tracing method was conducted to quantify the N transformation,N_(2)O and N_(2)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 N_(2)O 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 N_(2)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 N_(2)O 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 N_(2)emissions(28 and 24 mg N·kg^(-1),respectively).The N_(2)O/(N_(2)O+N_(2))of the six soils ranged from 5%to 40%.The N_(2)O/(N_(2)O+N_(2))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 N_(2)O emission and 61%of total N_(2)emission,which was higher than the contribution of fertilizer.The cumulative N_(2)O emission was positively correlated with soil background pH,which indicated that soil background pH might be an important factor regulating N_(2)O and N_(2)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.