复水干土的无机氮组分及对鲜土检测的可替代性

Inorganic Nitrogen Components of Rehydrating Dried Soil and itsSubstitutability to Detection of Fresh Soil

【目的】风干过程会干扰土壤微生物活性进而对土壤无机氮含量产生影响。探究复水干土过程能否消除风干效应,进而确定鲜土无机氮的可替代性时间节点等问题,为改进土壤氮素检测手段提供参考。【方法】以毕节市七星关区林下鲜土及复水风干土为研究对象,通过检测分析土壤全氮、铵态氮、亚硝态氮与硝态氮等指标,研究复水干土过程对林下土壤无机氮组分的影响及鲜土的可替代性。【结果】复水过程激活了土壤固氮菌活性,干土过程第15天出现显著峰值,约为复水结束时土壤全氮含量的1.50倍。随着水分丧失全氮含量在干土中期结束时又趋于稳定,并保持到整个干土过程结束。无机三氮含量明显受制于复水干土的环境条件,干土过程含量最大的为铵态氮,含量为18.79 mg/kg,占无机总氮的85.44%。厌气复水导致铵态氮含量在干土早期达最大,为52.93 mg/kg。干土中期(10~40 d)大气环境少变导致3种无机氮较为稳定;干土后期(40 d以后)亚硝态氮和硝态氮含量受大气条件影响显著,尤以亚硝态氮波动最为剧烈,与氨氧化菌在应对环境胁迫方面比亚硝酸氧化菌有更强的适应性有关。干土效应导致土壤硝化率明显提升,增长1.07~3.52倍,与硝化菌的好氧性有关。40 d可大致作为替代鲜土进行相关氮素检测的时间节点。与鲜土相比全氮仅有约5%的差异,但无机氮相对误差较大,最大差值出现在绝对含量最低的亚硝态氮指标上。【结论】鲜土仍是进行氮素检测的首选用土。

【Objective】Air-drying process interferes with soil microbial activity,thereby affecting inorganic nitrogen content in soil.In order to provide a reference for improving detection methods of soil nitrogen,whether the rehydrating dried soil process to eliminate the air-drying effect is explored to determine the substitutability time node of inorganic nitrogen in fresh soil.【Method】The fresh soil and rehydrating dried soil under forest in Qixingguan District of Bijie City are used as research objects.The effects of rehydrating dried soil on inorganic nitrogen component in soil under forest and its subsitutititability to fresh soil are studied through detecting and analyzing the indexes of soil total nitrogen,ammonium nitrogen,nitrite nitrogen and nitrate nitrogen.【Result】Rehydration process activates soil azotobacter activity,and the significant peak of total nitrogen appears on the 15th day of soil drying,about 1.50 times higher than that at the end of rehydration.With the loss of water,total nitrogen content tends to be stable until the end of middle stage for soil drying,and keeps until the end of whole drying process.Inorganic nitrogen content is obviously restricted to the environment condition of rehydrating dried soil.Ammonium nitrogen content is 18.79 mg/kg during the soil drying process,accounting for 85.44%of total inorganic nitrogen.Anaerobic rehydration causes the maximum ammonium nitrogen content(52.93 mg/kg)at the early stage of soil drying.Less variation in atmospheric environment at middle stage of soil drying(10-40 d)contributes the stability of three inorganic nitrogen.Nitrite nitrogen and nitrate nitrogen content are affected by atmospheric condition significantly at the end stage of soil drying(after 40 d),especially nitrite nitrogen with most violent fluctuation.This is related to the better adaptability of ammonium-oxidizing bacteria toward the environmental stress compared with nitrite-oxidizing bacteria.Soil drying effect increases soil nitration rate significantly,with an increase of 1.07-3.52 times,which is related with the aerobic property of nitrate-bacteria.40 d can be used as the time node for detecting related nitrogen of substituting fresh soil.Compared with fresh soil,there is only 5%difference in total nitrogen,but there is a great relative error in inorganic nitrogen,and the greatest difference appears in nitrite nitrogen index with the lowest absolute content.【Conclusion】Fresh soil is still the preferred soil for nitrogen detection.