Liming decreases the emission and temperature sensitivity of N2O following labile carbon addition

Abstract

Lime has been widely applied for ameliorating soil acidification, potentially improving soil fertility and crop production. However, the long-term effects of liming and its interaction with carbon (C) availability on the emission and temperature sensitivity (Q10) of greenhouse gas nitrous oxide (N2O) from acidic arable soil are not well understood. Here, the limed and unlimed acidic soils collected from a long-term field trial, amended with and without glucose as labile C, were incubated at 15℃ and 25℃ to investigate the responses of the emission and Q10 of N2O and the underlying mechanisms. Results showed that liming had no effect on N2O emission without labile C addition. While after labile C addition, N2O emissions were 13–28% lower in the limed relative to unlimed soils, indicating that the mitigation effect of liming on N2O emission can mainly be seen when labile C (e.g., from rhizodeposition) is highly available in soils. High temperature did not affect N2O emissions from soil without labile C addition, but greatly increased N2O emissions after labile C addition with significantly lower Q10 of N2O in the limed (1.23) relative to unlimed soils (1.48). These results suggested that liming could decrease the Q10 of N2O emission in the presence of labile C. Elevated soil pH by liming caused increases in the abundances of N2O reductase genes (nosZI and nosZII) over nitrite reductase genes (nirK and nirS), thus significantly lowering (nirK + nirS)/(nosZI + nosZII) ratio compared to the unlimed soil, particularly after labile C addition. Soil N2O emissions were strongly positively related to the nirK abundance, (nirK + nirS)/(nosZI + nosZII) ratio, and NO3− consumption after labile C addition, indicating that denitrification was mostly responsible for N2O emission. Concluding, long-term liming could potentially reduce N2O emission and its Q10 via decreased (nirK + nirS)/(nosZI + nosZII) ratio in acidic soils in the presence of labile C.