Implementation of the effect of urease inhibitor on ammonia emissions following urea-based fertilizer application at a Zea mays field in central Illinois: A study with SURFATM-NH3 model

Abstract Agriculture is the main source of ammonia (NH 3 ) emissions in the atmosphere. NH 3 is precursor to secondary fine particulate matter, which is of concern for its impacts on health and visibility. There are a limited number of field measurements of NH 3 emissions from fertilizer application in the US, and this limits our understanding of the importance of individual NH 3 source and sink processes in controlling timing and magnitude of NH 3 emissions. In this study, a new parameterization of the effect of urease inhibitor on NH 3 emissions from urea-based fertilizer was developed on the basis of experimental results found in the literature. This parameterization was combined with an existing operational parameterization of soil and stomatal emission potentials (Γ g , Γ s ) and was implemented in a surface-atmosphere transfer model for NH 3 (SURFATM-NH 3 ) in order to evaluate the bi-directional fluxes of NH 3 at the field scale. The model was evaluated with field measurements obtained by the flux-gradient (FG) and relaxed eddy accumulation (REA) methods in a fertilized corn field in central Illinois. By integrating the effect of urease inhibitor, the timing of the highest NH 3 emission peak was successfully predicted and its magnitude was close to that measured (predicted 2106 ng m −2 s −1 , measured by FG 2312 ± 582 ng m −2 s −1 ). Based on the model results, urease inhibitor has a considerable effect on the dynamics and order of magnitude of NH 3 fluxes. Furthermore, the model simulated the inhibiting action of N- ( n -butyl) thiophosphoric (nBTPT) and suggests that it can reduce NH 3 volatilization by 32%. The model also successfully predicted environmental parameters, such as soil temperature. Finally, this new version of SURFATM-NH 3 is a valuable tool to estimate the NH 3 bi-directional fluxes at the field scale, which describes dynamic modeling of Γ s and Γ g by taking into account the effect of urease inhibitor which is commonly used in the US to improve the efficiency of urea fertilizers.