氮肥施用水平及种类对生菜产量及菜地N2O排放的影响

采用静态箱-气相色谱法研究了氮肥施用水平及种类对生菜产量和土壤N_2O排放的影响。试验设7个处理:不施氮肥(N0),施氮112.5 kg N·hm~(-2)(N1),施氮225 kg N·hm~(-2)(N2),施氮337.5 kg N·hm~(-2)(N3),控释氮肥(CRU-N2),稳定性氮肥(SN-N2),有机无机氮肥配施(MN-N2)。对比研究了不同施氮水平和等氮量不同氮种类处理对N_2O排放特征和生菜产量的影响。结果表明,随着氮肥用量的增加N_2O排放通量增加。在试验条件下,生菜获得最高产量时的施氮量为125 kg N·hm~(-2),适量降低生菜施氮水平能有效降低N_2O气体累积排放量。相同氮水平下,SN-N2与MN-N2处理较N2处理分别增产达13.3%和17.2%,但差异未达显著水平。SN-N2处理N_2O排放总量和N_2O排放系数仅为0.80 kg N·hm~(-2)和0.36%,较常规施肥处理分别降低了84.8%和1.97个百分点。综上,在不降低生菜产量的前提下,优化氮肥施用水平并采用稳定性氮肥技术是菜地N_2O减排和减少蔬菜种植氮素损失的重要途径。

Effects of nitrogen application rate and sources on yield of lettuce and nitrous oxide emission in vegetable soil

Closed-chamber technology with gas chromatography method was used to study the effects of different nitrogen(N) application rates and sources on the yield of lettuce and nitrous oxide(N₂O) emissions from vegetable soil. Seven treatments were including zero N fertilization(N0), 112.5 kg N·hm^-2(N1), 225 kg N·hm^-2(N2, conventional fertilization), 337.5 kg N·hm^-2(N3), controlled release urea(CRU-N2), stability N fertilizer(SN-N2), integrate chemical and manure N fertilizer(MN-N2). The effects of different N levels and N sources with the same amount of N on characteristics of N₂O emission, yield of lettuce were comparatively studied. Results showed that the N₂O emission fluxes increased with the increasing of nitrogen fertilizer application. The optimum N rate to obtain the maximum yield of lettuce was 125 kg N·hm^-2. Reasonable reduction of N application rate could effectively reduced N₂O accumulative emission. Under the same N level condition, yield of lettuce increased by 13.3% and 17.2% with SN-N2 and MN-N2 compared with N2, however, there were not significant differences(P>0.05) for yield of lettuce between SN-N2, MN-N2 and N2. The total seasonal emission of N₂O and N₂O emission factor(EF)of SN-N2 only was 0.80 kg N·hm^-2 and 0.36%,which was 84.8% and 1.97 percent point reduction compared to N2. In conclusion, optimized N fertilization rate along with stability N fertilization technology without sacrificing vegetable output is an important approach for N₂O reduction emission and reducing on N loss in vegetable field.