How could simulated dewatering of slurry mitigate nitrous oxide emissions from fall and spring injections? - A modelling study in a Chernozem soil in Western Canada

Abstract

Process-based ecosystem models, such as ecosys, can be useful tools to gain insights and accurately project nitrous oxide (N₂O) inventories in national, regional and global scales, and to explore potential emission reduction strategies. Our objectives are to investigate how the ecosys model simulate the effects of fall and spring slurry injections on N₂O production and if de-watering slurry could become a potential N₂O mitigation strategy for both fall and spring injections. The ecosys model was used to simulate hourly N₂O fluxes from 2014 to 2017 in a cropping system with and without slurry (fall and spring additions) in comparison with field measurements in Alberta, Canada. Furthermore, we performed simulations of de-watered fall and spring slurry applications in the same scenarios. Our results showed ecosys adequately simulated soil temperatures and moisture contents at 10 and 20 cm depths [correlation coefficients (r) ≥ 0.929 for temperatures; r ≥ 0.529 for moistures]. The divergences of modelled and measured soil water contents during spring thaws could be attributed to uncertainties in model inputs for soil hydrological parameters as well as uncertainties in field measurements. The model captured reasonably well the dynamics of N₂O fluxes from soils receiving fall and spring slurry (r = 0.356). However, the concurrent discrepancies of N₂O fluxes between modelled and measured values during the wetter spring thaw of 2017 might be a result of an unsatisfactory simulation of snowmelt infiltration and runoff. Compared to whole slurry, simulated de-watered slurry resulted in considerable reductions in cumulative N₂O emissions by 16-36 and 23-29% for fall and spring slurry injections, respectively. The model results indicate that de-watering slurry would potentially be an efficient emission mitigation strategy; however, there is still a paucity of studies addressing the feasibility of dewatering as a practice and further research can focus on this knowledge gap.

Keywords: De-water; Ecosys; Model; Nitrous oxide; Slurry; Soil; Timing.