Many explanations of agricultural technology adoption have either been based loosely on diffusion concepts and have ignored economic factors or have been static economic models that ignore dynamic and spatial aspects of adoption. In this paper we propose a model of adoption which incorporates economic factors in a spatial and dynamic framework. the approach used is based on extending replicator dynamics models in evolutionary game theory to a spatial setting. The replicator dynamics of adopters versus non-adopters are characterised by a spatial diffusion model the solution of which illustrates how local institutions drive spatial technology adoption processes via the rules of the game. The model is applied to forage technology adoption in the Philippines and a method of empirically testing the model is presented.