菜地不同施氮量下N2O逸出量的研究

用田间原位密闭气室法和乙炔抑制原状土柱培养法 ,研究了蔬菜地不同施氮量下 N2 O的逸出量。结果表明 ,在一定施氮量范围内 ,N2 O通量随施肥量的增加而上升 ;除最高施肥量 (N4 50 )外 ,N2 O占 (N2 +N2 O)的比率随施肥量的增加而增加。在施肥水平低时 ,氮素的损失以 N2 为主 ,当施肥量高于 30 0 kg/ hm2后 ,则以 N2 O为主。 2 m土体中 NO3- N分析结果表明 ,试验结束时对照和 N4 50 处理土壤剖面中有 NO3- N累积 ,其余各个处理氮素都存在一定程度的损失 ,其中损失量最大的是 N1 50 处理 ,与 N2 O逸出量的趋势相一致。 N2 O逸出量占肥料 N总用量的 0 .15 %～ 0 .6 6 % ,肥料逸出量占土壤 N2 O总逸出量的 39.0 %～ 70 .3% ,且在施氮水平低于 N30 0 以下时 ,N2 O逸出量有随施肥量增加而上升的趋势

N2O losses from vegetable field of applying different amounts of NO3-N

By using inclosed chamber method and C₂H₂ inhibition intact soil cores method,the field experiment and lab incubation test were carried out on the fallow vegetable field after applying different amount NO₃-N to study N₂O losses.The results show that N₂O flux increases with the increase of applying NO₃-N amount except for the treatment N₄₅₀,the ratio N₂O/(N₂O+N₂) also has the same trendency.At the lower NO₃-N rates,gaseous nitrogen losses will be N₂.Whereas for the higher NO₃-N amount,the losses will be N₂O.The highest N losses will take place at N₁₅₀ lever.Both the field results and caculation of NO₃-N losses from 2 m soil profile have the similar conclution.N₂O emission amount is only about 0.152%-0.655% of total applied N,and the emission from fertilizer is about 39.0%-70.3% of total soil emission.The natural N₂O emission of test soil is 1.876 kg/(hm²·a).