MAGMA: a simulation model to help manage animal wastes at the farm level

MAGMA is a hybrid dynamical system (HDS; i.e. with both continuous and discretevalued variables) allowing the simulation of management of various kinds of animal manure or slurry production and utilization modes (waste spreading on cultivated crops and fallow land and compost making). It can support decision-making to help better manage such potentially hazardous organic matter (OM) at the farm level with the aims of environmental risk minimization, agricultural efficiency and farming sustainability. One can define several scenarios based on farm structural parameters in MAGMA, for example, animal and crop production characteristics, capacity of manure or slurry spreading equipment, and distances. Each scenario can be tailored according to several management strategies by using switch constants. This paper describes the core of the model, enabling the simulation and scheduling of actions (crop harvest, manure or slurry spreading, etc.) that consume those wastes according to various uses. The use of the model in simulation is explained and a detailed example is given on how it can contribute in choosing alternative management strategies.