Representing the stored grain ecosystem for quality maintenance implies the representation of all its characteristics that take part in the grain quality degradation process. A mixed qualitative and quantitative modelling is used to represent the stored grain ecosystem. The temperature, moisture content and presence of insects are used as control variables. The quality maintenance operations are represented as actions to be executed in time requiring available equipment and consumable. Our planning approach involves three consecutive stages: treatment to obtain a safe grain storage condition, storage to maintain the storage condition and dispatch to respond to the market requirements.