不同配比有机无机肥料对菜地N_2O排放的影响

Effects of combined organic and inorganic fertilizers on N_2O emissions in intensified vegetable field

【目的】采用静态暗箱–气相色谱法,研究有机无机肥料配施对菜地N_2O排放的影响。【方法】试验期间连续种植了4季蔬菜,分别为香菜、空心菜、菜秧、菠菜,其中香菜和菠菜种植期间有塑料大棚覆盖。每季蔬菜收获后至下季蔬菜种植前有时间不等的休耕期。每季蔬菜种植前肥料作为基肥一次性施入,施肥量均为N250 kg/hm^2,其中空心菜在第二茬收获后追施N 250 kg/hm^2一次,整个观测期共施肥5次,总施氮量为N 1250kg/hm^2,同时施入等量P_2O_5、K_2O。试验共设4个处理:不施氮对照(CK)、单施化肥(NPK)、有机无机肥料1∶1配施(M1N1)和有机无机肥料2∶1配施(M2N1)。N_2O排放通量测定频率为每周一次,每次施肥后则每2天测定一次。【结果】观测期内各处理菜地N_2O排放主要集中在4~10月份,并与10 cm土层土壤温度呈显著正相关;NPK处理菜地N_2O排放通量与土壤无机氮含量显著相关,其他处理N_2O排放通量与土壤铵态氮、硝态氮以及无机氮含量间无显著相关。整个观测期内土壤充水孔隙度(WFPS)介于39%~59%之间,土壤水分含量的变化对N_2O排放通量无显著影响。与NPK处理相比,M1N1和M2N1处理均能保证蔬菜产量稳定,并显著提高空心菜的产量。与NPK处理相比,M1N1处理显著降低菜地N_2O周年累积排放量36%,显著降低N_2O周年排放系数64%。与M2N1处理相比,M1N1处理的N_2O周年累积排放量和周年排放系数分别显著降低29%和56%;而M2N1处理较NPK处理的减排效果不显著。【结论】在集约化菜地适宜的无机有机肥料配比既能保证蔬菜产量,又能减少N_2O排放,不施或施用有机肥比例过高均不利于减少N_2O周年排放。本试验条件下,有机无机肥料以1∶1配施是合适的稳产减排措施。

【Objectives】Effects of combined application of organic manure（M） and inorganic nitrogen fertilizers（N） on annual N_2O emissions from vegetable fields were studied using the static chamber-gas chromatograph method. 【Methods】Field experiments were established in triplicates with four treatments： CK（without N application）, NPK, M1N1（M and N in the ratio of 1∶1） and M2N1（M and N in the ratio of 2∶1）,and N amount was equally applied in the N-fertilized treatments. Coriander herb, water spinach, baby bok choy and spinach were cultivated in turn with short time of fallow in between. The N_2O emissions were normally monitored in week frequency, but in every two days after fertilization and irrigation. Once N basal application was N 250 kg/hm^2 for crop except for water spinach with twice application. The total N input during the experiment was 1250 kg/hm^2. 【Results】N_2O emissions mainly emitted from April to October, which were significantly correlated with soil temperature in the 10 cm depth in all treatments. The N_2O flux in NPK treatment had significant correlation with soil inorganic nitrogen content, but in CK, M1N1 and M2N1 treatments, the N_2O fluxes had no significant correlations with soil nitrate, ammonium and inorganic nitrogen contents. In addition,WFPS（water filled pore space） ranged from 39% to 59% and no significant correlations between soil moisture and N_2O fluxes were detected during the experimental period. Compared with NPK treatment, the vegetable yields of water spinach had been significantly improved in M1N1 and M2N1 treatments, but there were no significant differences in cumulative vegetable yields between M1N1, M2N1 and NPK treatments. Compared with the NPK treatment, the cumulative N_2O emission and N_2O emission factor（EF） in the M1N1 treatment was significantly decreased by 36% and 64%, respectively. Meanwhile, compared with M2N1 treatment, the cumulative N_2O emission and N_2O emission factor（EF） in the M1N1 treatment was significantly decreased by 29% and 56%,respectively. But the effect in reducing N_2O emission was insignificantly in M2N1 treatment, compared with NPK treatment.【Conclusions】Appropriate ratio of chemical and organic fertilizer is necessary for mitigating N_2O emissions in intensified vegetable fields. In the experimental conditions, the ratio of chemical N to organic N in 1∶1 is satisfactory for ensuring vegetable yield and keeping low annual emission of N_2O.