施加碳酸钙对酸性土壤微生物氮循环的影响

Effects of CaCO_3 Application on Soil Microbial Nitrogen Cycle in an Acid Soil

土壤硝化作用和反硝化作用是闭合氮循环的重要步骤,阐明在酸性土壤施用碳酸钙(CaCO_3)对土壤理化性质及土壤氮循环的影响,可为农田质量稳定和可持续利用提供理论依据和技术支持.以湖南省湘潭市酸性土壤为研究对象,设计了4个CaCO_3施加量,分别为0、2.25、4.5和7.5 t·hm^(-2),在种植一季水稻后,分析了不同CaCO_3施加量对土壤理化性质、硝化作用和反硝化作用的影响.结果表明CaCO_3的施加,显著提高了土壤溶解有机碳(dissolved organic carbon,DOC)762.10~868.58mg·kg^(-1),促进土壤硝化作用[0.59~0.82μg·(g·h)^(-1),以NO_2^--N/土计],但当CaCO_3施加量达7.5 t·hm^(-2)时对硝化作用产生抑制,土壤反硝化作用对CaCO_3的响应较为复杂.Pearson相关分析结果表明,土壤硝化作用与土壤DOC显著正相关,和NH_4^+-N含量显著负相关,反硝化作用与NO_3^--N含量、土壤DOC显著正相关,和含水量显著负相关.

Soil nitrification and denitrification are important steps in closing the nitrogen cycle. Understanding the effects of CaCO_3 application on the physicochemical properties and nitrogen cycle in acid soil would provide some theoretical and technical information for stable and sustainable utilization of this agricultural soil. In this study,a field trial was conducted in Xiangtan city,Hunan province. In this field,the soil pH was 5. 54,and CaCO_3 was applied at four levels： 0,2. 25,4. 5,and 7. 5 t·hm^（-2）. After one season of rice cultivation,the soil was sampled to determine dissolved organic carbon（ DOC）,NH_4~＋-N,and NO_3^--N levels,and the potential nitrification rate（ PNR） and denitrifying enzyme activity（ DEA） were measured. The results showed that CaCO_3 application improved the content of soil DOC（ 762. 10-868. 58 mg·kg^（-1）） and PNR [0. 59-0. 82 μg·（ g·h）^（-1）]. However,excessive application of CaCO_3（ 7. 5 t·hm^（-2）） revealed an obvious inhibition on the activity of soil nitrification. Furthermore,the result of Pearson correlation analysis indicated that soil nitrification was positively correlated with soil DOC and negatively correlated with NH_4~＋-N content,whereas denitrification had a significant positive correlation with NO_3^--N content and soil DOC,but a negative correlation with water content.