长期不同培肥处理对土壤有机氮组分及氮素矿化特性的影响

【目的】揭示长期不同培肥处理对黄土高原南部土垫旱耕人为土(土)土壤有机氮组分、氮素矿化的影响以及有机氮组分对氮素矿化潜力的贡献。【方法】采用Stanford和Smith间歇淋洗好气培养法测定了土19年长期不同施肥处理土壤矿化氮的数量,并采用Bremner法测定了培养前、后土壤有机氮各组分含量的变化。【结果】各处理土壤有机氮各组分含量高低顺序为:氨基酸氮非酸解氮酸解未知氮氨态氮氨基糖态氮。与不施肥对照相比,长期单施化肥处理土壤有机氮各组分含量有不同程度的增加,但幅度有限;化肥配施秸秆或有机肥处理显著提高了各有机氮组分含量,其中以氨基酸氮含量增加幅度最大;化肥配施秸秆或有机肥处理降低了酸解有机氮占全氮的比例。化肥长期配施有机肥或秸秆,显著提高了土壤氮素矿化势(N0)以及矿化率,其中化肥配施有机肥土壤N0大于化肥配施秸秆处理。相关分析表明,土壤氮素矿化势N0与培养前后土壤氨基酸氮变化量间呈显著负相关关系(P0.05),与土壤酸解未知态氮和非酸解氮的变化量间的负相关关系未达显著水平(P0.05)。【结论】化肥配施有机肥或秸秆,是提高土壤供氮潜力的有效手段;氨基酸氮是土壤可矿化态氮的主要贡献者。

Effects of Different Long-Term Fertilization on the Fractions of Organic Nitrogen and Nitrogen Mineralization in Soils

Objective]A long-term field experiment located at the south edge of the Loess Plateau in Shaanxi was conducted to study the effects of different fertilizer treatments on the forms of organic nitrogen and the potential nitrogen mineralization (N0) in soils. Method]Soil organic N was fractionated by acid hydrolysis-distillation method (Brenmer method),and N mineralization was estimated by using 30-week aerobic incubation method of Stanford and Smith. Result]The results showed that the range of organic nitrogen forms in soil was in the following order,amino acid N＞non-hydrolysable N＞hydrolysable unidentified N＞ammonium N＞amino sugar N.Compared to the un-fertilization (CK) treatment,the addition of chemical fertilizers (NPK treatment) increased the different forms of organic N in soil,but the increasing rate was low.Compared with the CK treatment,the SNPK (NPK plus straw) and MNPK (NPK plus manure) treatments significantly increased the contents of different fractions of organic nitrogen in soil,especially the content of amino acid N,whereas they decreased the proportion of total hydrolysable N accounted for total nitrogen.Application of MNPK significantly increased the potentially mineralizable nitrogen (No) and the rate of N mineralization.The significantly negative correlation was found between amino acid N and No (P＜0.05);and the negative correlationships between hydrolysable unidentified N and non-hydrolysable N and soil No were not statistically significant (P＞0.05). Conclusion]Long-term application of NPK with manures or crop straw is an efficient way to enhance the nitrogen supplying capacity of soil,and amino acid N is the major contributor to the soil mineralized nitrogen.