RESUMO
Soil nitrification and denitrification are important steps in closing the nitrogen cycle. Understanding the effects of CaCO3 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 CaCO3 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), NH4+-N, and NO3--N levels, and the potential nitrification rate (PNR) and denitrifying enzyme activity (DEA) were measured. The results showed that CaCO3 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 CaCO3 (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 NH4+-N content, whereas denitrification had a significant positive correlation with NO3--N content and soil DOC, but a negative correlation with water content.
