长期施肥及撂荒土壤对不同外源氮素固持及转化的影响

Effects of Long-Term Fertilization and Fallow on the Retention of Different Forms of Nitrogen in Different Soils

【目的】硝态氮及铵态氮是常用的氮肥种类,其施入土壤后的去向与作物氮素供应及土壤培肥有关,不同肥力土壤对施入的这些外源氮的固持与转化的影响有何不同值得关注。【方法】以黄土高原南部进行的17年长期定位试验不同处理土壤为研究对象,利用培养试验方法研究了灭菌与不灭菌条件下长期施用不同肥料及撂荒土壤对施入不同形态氮素固持及转化的影响。【结果】虽然供试的土壤由于长期施肥或撂荒土壤有机质及可溶性有机碳含量存在明显的差别,但培养期间不同处理土壤对施入的外源硝态氮在土壤中的生物及非生物固持及转化过程无明显影响。而施入铵态氮后,不同处理土壤在培养第3天起微生物对外源铵态氮的固持已相当明显,培养结束后平均约有41%的铵态氮被土壤微生物固持,23%的铵态氮被非生物因素固持或发生挥发损失。【结论】长期不同施肥处理或撂荒土壤对外源铵态氮的非生物固持能力的影响无显著差异,但有机质含量较高的撂荒和化肥与有机肥配合施用处理土壤对施入的铵态氮生物固持能力高于不施肥对照和单施化肥处理。

【Objective】Nitrate and ammonium are two common forms of nitrogen fertilizers and their transformations in soils is related to the nitrogen supply and loss from soil.It is interested to understand the effects of soils with a long-term fertilization and fallow on the retention of these different forms of nitrogen.【Method】The soils used were sampled from a 17-year long-term fertilization experiments located in the south edge of the Loess Plateau.【Result】Although the contents of organic matter and soluble organic carbon in the soils were different,there were no significant differences in biotic and abiotic nitrogen retention in the soil when nitrate form of nitrogen was added.On the contrary,when ammonium was added into the soils,N immobilization by biotic factors occurred from the 3rd day after incubation.At the end of incubation,about 41% of the NH4＋-N added was immobilized by soil microbes,and about 23% of NH4＋-N added was fixed or lost by abiotic factors.【Conclusion】The long-term fertilization and fallow had no significant effects on N retention by abiotic factors,however,the long-term addition of chemical and organic fertilizers and fallow significantly increased the N retention by biotic factor in comparison with the treatments without fertilizer or only addition of chemical fertilizers.