This paper presents a regional agricultural model using a plant growth simulation model (EPIC) as generator of activites. Its objective is to develop a simple tool which determines the possible effects of economic changes on regional supply and revenue as well as at the level of farm structure and farm relationships. Erosion trends can also be observed. The use of a physiological model allows us to utilize real activites of the region as well as some potential ones (such as irrigation or different fertilizer doses). Thus, if economic changes are produced,, these activities may become more profitable and, so, will appear in the solution. The predictive capability of the model then, becomes more accurate. In this work the autors develop a model prototype of this kind for a region in Argentina, which considers three types of farms, including land market (sale and rent) and the market for rented machinery. The results obtained on cropping parttern are close to the actual ones with the present economic environment. When price and interest rate simulations are done, differences inter and intra farms are observed as well as in the total regional output. The sensitivity analysis shows that changes in wheat and soybean prices would induce the most important changes at the regional level, which is not the case for corn or cattle prices. On the other hand, erosion trends will generally be aggravated (except when wheat price increases), if no specific measures are taken to counterbalance the tendency.