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RESEARCH PRODUCT

Defining the conditions of liming products application to promote nitrous oxide reduction in an acidic agricultural soil

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With a lifetime of more than 100 years in the atmosphere, N2O is an important greenhouse gas with a global warming potential (GWP) of ~ 300 for a 100-year timescale that also takes part in the destruction of the ozone layer (Ravishankara et al., 2009). While N2O emissions are projected to increase in the coming years (Aneja et al., 2019), the promotion of the N2O reduction to N2 in soils could appear as a possible solution for mitigating soil N2O emission (Hénault et al., 2019). The N2O reduction path appears to be mainly driven by the soils’ pH with a progressive inhibition when pH is lower than 6.8. The aim of the proposed study was to test during laboratory experiments the time and the dose required for different liming products (CaCO3 > 99 % reagent, and tow R&D products coded as RD1 and RD2), to concomitantly increase soil pH and soil capacity to reduce N2O.During a first experiment, an acidic soil (pH=5.6) developed on the granitic substrate from the Morvan Region in France and cultivated with maize was sampled in July 2019, sieved and organized in 4 sets, three of them receiving the equivalent of 1.4 t ha-1 of neutralizing value (NV) respectively as CaCO3, RD1 and RD2 while the last set of soil did not receive any liming product (control). All were placed at a soil moisture of 20 % w/w and at 15°C. Soil pH (ISO 10390: 2005) and soil capacity to reduce N2O (ISO / TS20131-2: 2018) were then monthly determined on each of these 4 sets of soil. During a second experiment, the same acidic soil received different doses of RD1 from 0 to equiv. 1.4 t of NV. Soil samples were incubated at 15°C and both soil pH and soil capacity to reduce N2O were monthly determined.Both changes in soil pH and soil capacity to reduce N2O were observed after one month of incubation and continue to be observed over all the experiment. Changes in soil pH and in soil capacity to reduce N2O were especially rapid and important for CaCO3 and RD1 and consistent with the relation between soil pH and soil capacity to reduce N2O reported by Hénault et al., 2019. Significant changes could be obtained at dose lower than the theorical 1.4 t VN ha-1. We will now continue to define conditions of application of liming products for mitigating soil GHG emission (N2O and CO2) during experiments conducted from the laboratory to the field scales.