This paper presents a model to represent situated action in farming systems. The basic idea is to invert the classical vision of action that stipulates that action is a consequence of a decision process and a plan. We consider action as mainly dictated by a situation created by the interaction of the actor and his/her environment. Hence, action is a process that emerges from this situation. Thus, in this paper we treat the question of how to model action as an emergence process from the situations created by actors and their environment? For this, our model is based on multiagent system as well as on the affordance, emergence and stigmergy concepts (this paper emphasizes mainly the first two).