不同园龄果园土壤硝化与反硝化活性及N2O排放（英文）

目的]评价硝化反硝化作用在果园土壤氮素损失中的贡献率以及N2O的排放量和排放特性。方法]在室内培养条件下比较研究了3种不同园龄果园土壤及未开垦土壤之间硝化反硝化活性的差异。结果]培养26天的未开垦土壤、5年、12年和20年园龄果园土壤的氮肥硝化率分别为6.85%、10.26%、13.29%和12.90%。4种土壤硝化活性均相对较低,但随种植年限的延长呈提高趋势,而且与土壤有机质和铵态氮含量呈显著正相关关系(P<0.05),与全氮含量呈极显著正相关关系(P<0.01),与土壤碳氮比呈显著负相关关系(P<0.05),与pH值呈极显著负相关关系(P<0.01)。3种果园土壤N2O排放量显著高于未开垦土壤(P<0.05),其中硝化作用产生的N2O排放量占施氮量的0.03%～0.08%。硝化过程产生的N2O排放量与土壤有机质、全氮、铵态氮含量呈显著正相关关系(P<0.05),而与土壤碳氮比呈显著负相关系(P<0.05),与pH值呈极显著负相关关系(P<0.01)。不同园龄果园土壤之间氮肥的反硝化活性差异显著,表现为20年>12年>5年>未开垦土壤,反硝化损失氮量占施氮量的0.01%～3.11%,与土壤有机质含量呈显著正相关关系(P<0.05)。结论]我国南方果园土壤硝化水平相对较低,但随种植年限的延长呈提高的趋势;而土壤反硝化水平相对较高,而且随种植年限的延长显著提高。

Nitrification and Denitrification Activities and N2O Emission of Orchard Soils Cultivated for Different Periods of Time

Objective] The aim was to investigate the differences in nitrification and denitrification activities and the N2O emission of orchard soils cultivated for different periods of time.Method] Incubation experiment was conducted to determine the nitrification and denitrification activities and N2O emission of three types of orchard soil samples that had been cultivated for 5,12 and 20 years,respectively,by using the virgin soil sample as control.Result] After 26 d of incubation,the nitrification rates of nitrogen fertilizer in the virgin soil sample and the orchard soil samples cultivated for 5,12 and 20 years were 6.85%,10.26%,13.29% and 12.90%,respectively,which were positively correlated with content of soil organic matter,ammonium nitrogen and total nitrogen(P<0.05),and negatively correlated with soil carbon-nitrogen ratio and pH value(P<0.05).The denitrification activities of these soil samples increased with the increase of cultivation years.The amount of nitrogen loss by denitrification accounted for 0.01%-3.11% of the amount of fertilizer nitrogen,and had a positive correlation with the content of soil organic matter(P<0.05).The N2O emissions of orchard soil samples were higher than that of the virgin soil samples(P<0.05).Conclusion] In South China,the nitrification activity of orchard soil is relatively low,but it has a tendency to increase as the cultivation years increases;the denitrification activity is relatively high,and increases significantly with the increase of cultivation years.