Modelling nitrification inhibitor effects on N 2 O emissions after fall- and spring-applied slurry by reducing nitrifier NH 4 + oxidation rate

[摘要] Reductions in N 2 O emissions from nitrification inhibitors (NI) are substantial but remain uncertain because measurements of N 2 O emissions are highly variable and discontinuous. Mathematical modelling may offer an opportunity to estimate these reductions if the processes causing variability in N 2 O emissions can be accurately simulated. In this study, the effect of NI was simulated with a simple, time-dependent algorithm to slow NH 4 + oxidation in the ecosystem model ecosys . Slower nitrification modelled with NI caused increases in soil NH 4 + concentrations and reductions in soil NO 3 - concentrations and in N 2 O fluxes that were consistent with those measured following fall and spring applications of slurry over 2 years from 2014 to 2016. The model was then used to estimate direct and indirect effects of NI on seasonal and annual emissions. After spring slurry applications, NI reduced N 2 O emissions modelled and measured during the drier spring of 2015 (35 % and 45 %) less than during the wetter spring of 2016 (53 % and 72 %). After fall slurry applications, NI reduced modelled N 2 O emissions by 58 % and 56 % during late fall in 2014 and 2015 and by 8 % and 33 % during subsequent spring thaw in 2015 and 2016. Modelled reductions were consistent with those from meta-analyses of other NI studies. Simulated NI activity declined over time so that reductions in N 2 O emissions modelled with NI at an annual timescale were relatively smaller than those during emission events. These reductions were accompanied by increases in NH 3 emissions and reductions in NO 3 - losses with NI that caused changes in indirect N 2 O emissions. With further parameter evaluation, the addition of this algorithm for NI to ecosys may allow emission factors for different NI products to be derived from annual N 2 O emissions modelled under diverse site, soil, land use and weather.

[学科分类] 大气科学