This paper presents a model to represent situated action in farming systems. The idea is to consider a multi-agents system in which the environment is an intelligent entity that has the ability to decide at a given time and space the actions to perform. Surrogates of real actors, called actuators, just execute the action dictated by the agents embedded in the environment. For this, the model is based on the affordance and stigmergy concepts as well as a multi-agents approach.