N 2 O contributes to increasing the greenhouse effect and is also involved in stratospheric ozone depletion. In soil and water, N 2 O reductase catalyses the reduction of N 2 O into the inert form N 2 . N 2 O reductase activity is known to be affected by acidic conditions and the application of liming materials to acidic soils is now proposed as a solution for mitigating soil N 2 O emissions. During a one-year laboratory experiment, we studied the functioning of N 2 O reductase after the application of calcium carbonates to an acidic soil with a very low capacity to reduce N 2 O. The functioning of N 2 O reductase was characterised through anaerobic incubations using the acetylene inhibition technique combined with a logistic model to determine the main enzyme functioning characteristics (latency, maximal rate). Both changes in soil pH and soil capacity to reduce N 2 O were rapidly observed after the application of lime materials. The activity of N 2 O reductase was observed to be efficient throughout the experiment even when the soil had returned to initial acidic conditions, revealing a hysteretic response of N 2 O reductase to pH variations. Nevertheless, some signs of lower N 2 O reductase activity over time were observed mainly after 200 days of applying lime materials. Altogether, these results suggest that, in this soil condition, the beneficial impact of the application of liming materials on N 2 O emissions could last longer than this on soil pH.
The functioning of the nitrous oxide (N2O) reductase enzyme involved in the last step of denitrification is pH sensitive, with an optimum of 6.8. A solution to mitigate N2O emissions would be to bring soil pH close to neutrality by adding agricultural liming products (aglime). Nevertheless, the influence of aglime on the soil greenhouse gas (GHG) balance (CO2–N2O) is a subject of debate, particularly when considering the fate of the carbon (C) derived from carbonates. Our objective was to investigate the results of the effect of calcium carbonate (CaCO3) aglime on the CO2–N2O balance. Sixteen cylinders of undisturbed acidic soil were taken from a sandy loam profile and incubated at 20°C for 107 days in anaerobic conditions (water‐filled pore space >60%). Eight limed treatment cylinders received 1.45 g of aglime on the soil surface (2 t NV ha−1) and 0.08 g of N (100 kg of N ha−1). Eight control treatment cylinders received only 0.08 g of N. N2O and CO2 fluxes were measured and converted into CO2 equivalents to perform a GHG balance calculation. Furthermore, soil and leachate properties were measured. Aglime application triggered a reduction of N2O emissions, probably due to an increase in soil pH at the beginning of the experiment, which would have led to the N2O reductase activation. High NO3−$$ {{\mathrm{NO}}_3}^{-} $$‐N content in the soil may inhibit the high N2O reduction potential in the limed treatment. CO2 emissions were unexpectedly lower in the limed treatment. Aglime addition did not enhance C mineralisation, which may be explained by the possible stabilisation of soil organic carbon. A significant 11.3% reduction of GHG emissions was observed in the limed treatment. Overall, our results show that a strategy of liming acidic agricultural soil could be implemented for its potential in GHG mitigation. Nevertheless, future in‐depth research is necessary to better understand the fate of the C brought about by aglime.
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