Hysteretic response of N2O reductase activity to soil pH variations after application of lime to an acidic agricultural soil

Nitrous oxide (N₂O) contributes to increasing the greenhouse effect and is also involved in stratospheric ozone depletion. In soil and water, N₂O reductase catalyses the reduction of N₂O into the inert form N₂ and is then considered as a key environmental enzyme. N₂O reductase activity is known to be affected by acidic conditions (Samad et al. 2016) and the application of liming materials to acidic soils is now proposed as a solution for mitigating soil N₂O emissions (Barton et al. 2013).

During a one-year laboratory experiment, we studied the functioning of N₂O reductase after the application of calcium carbonates to an acidic soil with initially a very low capacity to reduce N₂O. The functioning of N₂O 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 N₂O were rapidly observed after the application of lime materials. The activity of N₂O reductase was observed to be efficient throughout the experiment even when the soil had returned to initial acidic conditions, revealing a hysteretic response of N₂O reductase to pH variations. Nevertheless, some signs of lower N₂O 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 N₂O emissions could last longer than this on soil pH.

Keywords: Climate change mitigation · N₂O reductase · Soil · pH · Lime application · Logistic modelling

 

References:

Barton, L. et al. (2013) Is liming soil a strategy for mitigating nitrous oxide emissions from semi-arid soils? Soil Biology and Biochemistry 62, doi: 10.1016/j.soilbio.2013.02.014

Samad, M. S. et al. (2016) High-resolution denitrification kinetics in pasture soils link N₂O emissions to pH, and denitrification to C mineralization. Plos One 11, doi: 10.1371/journal.pone.0151713  

 

Acknowledgements: The authors gratefully acknowledge funding for the NatAdGES project from the “Investissement d’Avenir” program, ISITE-BFC project (contract ANR-15-IDEX-0003), the European Regional Development Fund (FEDER), the public investment bank (BPI France) and the CMI-Roullier.