We introduce a new model for examining the dynamics of uptake of technological innovations in agricultural systems, using the adoption of zero-till wheat in the rice-wheat system in Haryana state, India, as a case study. A new equation is derived which describes the dynamics of adoption over time and takes into account the effect of aggregation (e.g. on a spatial and/or cultural basis) in the adopting population on the rate of adoption. The model extends previous phenomenological models by removing the assumption of homogeneity in the non-adopting fraction of the population. We show how factors affecting the per capita rate of adoption can be captured using cognitive mapping and simulate the dynamics of the adoption process.