Nitrapyrin Addition Mitigated CO2 Emission from a Calcareous Soil Was Closely Associated with Its Effect on Decreasing Cellulolytic Fungal Community Diversity.

Abstract

Application of nitrification inhibitors (NIs) has been widely used to inhibit nitrification and reduce N2O emissions. However, the impacts of NI addition on soil carbon transformation and carbon-degrading microbial communities have not been well explored. Here, a microcosm experiment was carried out, and four treatments were designed: (i) unfertilized control, (ii) urea alone, (iii) urea plus cattle manure, and (iv) urea plus cattle manure with nitrapyrin. The influence of nitrapyrin on soil CO2 emissions, carbon-degrading extracellular enzyme activities, and the abundance and diversity of the cbhI community was investigated. Compared to the treatment of urea plus cattle manure, nitrapyrin significantly decreased cumulative CO2 emissions by 51.8%. Moreover, cbhI community gene copies and their α-diversities (P < 0.05) were also significantly reduced by nitrapyrin application. A partial least squares path model showed that CO2 emission was positively associated with cbhI community α-diversity but negatively associated with nitrapyrin addition. We conclude that the mitigation of soil CO2 emissions by nitrapyrin can be ascribed to its effects on decreasing of cellulose-degrading gene community diversity. Our findings provide new insights into the side-effects of nitrapyrin on abating CO2 emission.