The spatial extension of perennial biomass crop, like miscanthus, seems to be unavoidable to face the decrease of fossil fuel. However, the risk of a food / non food competition due to land use change has to be anticipated. Several models of biomass crops allocation have been already performed. Most of these models simulate large-scale allocation processes, taking into account numerous biophysical variables but only few true-to-life human variables. In this paper, we present modelling framework of miscanthus allocation in farmland. We use a case based reasoning model in order to compute both biophysical and human variables. An Ad hoc similarity measures framework and the comparison of tow modelling techniques are presented. First results of one application based on a french case study are discussed. They show the necessity to take into account stakeholders' knowledge of miscanthus allocation process in the modelling.