Ammonia emission is calculated using the methodology described in the following reference:
Søgaard, H.T., Sommer, S.G., Hutchings, N.J., Huijsmans, J.F.M., Bussink, D.W. and Nicholson, F., 2002. Ammonia volatilization from field-applied animal slurry—the ALFAM model. Atmospheric Environment, 36(20), pp.3309-3319.