Possibilities to reduce nitrous oxide (N20) emission from soils can be explored with simulation models. In this study, principal assumptions and hypotheses underlying such a simulation model under development are presented. It uses soil water content profiles as main input data and describes production, consumption and transport of N20.Observations on sandy grassland plots in the Wageningen Rhizolab will be used in the model development. The model is to explain the shape of the nitrous oxide profiles and the relation between subsurface nitrous oxide gradients and the observed fluxes.