不同施氮水平对农田黑土净氮转化速率和温室气体排放的影响

探讨不同施氮水平对农田黑土氮素转化和温室气体排放的影响,以期为农田合理施肥提供科学指导。以黑龙江省农田黑土为对象,采用室内培养试验,研究土壤净氮矿化速率、净硝化速率、N₂O和CO₂排放速率及累积排放量对不同施氮水平0 mg N/kg (N0)、40 mg N/kg (N40)、60 mg N/kg (N60)、80 mg N/kg (N80)]的响应。结果表明,不施氮的N0处理土壤净氮矿化速率为0.03 mg N/(kg·d),而N40、N60和N80处理土壤净氮矿化速率分别为-0.71、-1.01、-1.27 mg N/(kg·d),均表现为对氮的净固定。施氮显著促进了土壤硝化作用,N0处理土壤净硝化速率为0.32 mg N/(kg·d),而N40、N60和N80处理土壤净硝化速率分别为N0处理的15.2、19.7、24.0倍。在0~60 mg N/kg施氮水平内,土壤N₂O排放速率随施氮水平的增加而显著增加,施氮水平增加至80 mg N/kg时,N₂O排放速率反而显著低于N60处理。N0处理的N₂O排放比例为8.11‰,施氮后N₂O排放比例显著降低,N40、N60和N80处理的N₂O排放比例分别为1.48‰、1.72‰和1.15‰,3个施氮水平间没有显著差异。与N0处理相比,施氮显著抑制了土壤CO₂的排放,但CO₂累积排放量不受施氮水平的影响。研究表明,施氮水平显著影响土壤净氮转化速率和温室气体排放,研究结果对加深农田黑土氮转化规律的理解及氮肥的合理施用具有实际意义。

Effects of Different Nitrogen Application Levels on Net Nitrogen Transformation Rate and Greenhouse Gas Emission in Cropland Black Soil

The study aims to understand the effects of different nitrogen (N) application levels on N transformation and greenhouse gas emissions in cropland black soil, and provide scientific guidance for rational fertilization in cropland. Cropland black soil in Heilongjiang Province was selected to study the responses of net N mineralization rate, net nitrification rate, N₂O and CO₂ emission rates and cumulative emissions to different N application levels 0 (N0), 40 (N40), 60 (N60) and 80 (N80) mg N/kg] through a laboratory incubation experiment. The results showed that the net N mineralization rate of N0 treatment was 0.03 mg N/(kg·d), while that of N40, N60 and N80 treatments was -0.71, -1.01 and -1.27 mg N/(kg·d), respectively, which indicated the occurrence of net N immobilization in the three treatments. Nitrogen application significantly promoted nitrification in soil, soil net nitrification rate of N0 treatment was 0.32 mg N/(kg·d), while that of N40, N60 and N80 treatments was 15.2, 19.7 and 24.0 times that of N0 treatment, respectively. The N₂O emission rate increased significantly with the increase of N application level within 0-60 mg N/kg, however, when the N application level increased to 80 mg N/kg, N₂O emission rate was significantly lower than that of N60 treatment. The N₂O emission ratio of N0 treatment was 8.11‰, N application significantly decreased the ratio to 1.48‰, 1.72‰ and 1.15‰ under N40, N60, and N80 treatments, respectively, and no significant difference among the three N application rates was observed. Compared with N0 treatment, N application significantly inhibited CO₂ emission, whereas, CO₂ cumulative emission was not affected by N application level. This study show that N application level significantly affect soil net N transformation rate and greenhouse gas emissions, and the results are of practical significance for deeply understanding the N transformation regularity in cropland black soil and the rational application of N fertilizer.