During the past decade, there has been a growing interest in expanding the list of factors affecting the adoption and diffusion of agricultural technology. It has been suggested that most previous research efforts have been insensitive to contextual variables and institutional constraints. The physical environment has been suggested as one contextual variable that has been largely ignored in past adoption-diffusion research. The present study tested for the relative effects of a site-specific indicator of the physical environment (saturated thickness), as well as personal attributes and farm structural characteristics for the adoption of irrigation innovations in the Texas High Plains. The results revealed that saturated thickness is an important variable in understanding the adoption of the irrigation innovations considered. While a multivariate analysis revealed that farm size overall was the most important variable, the environmental factor was more important than traditional research variables selected for use in this study. It is concluded that the use of environmental variables does contribute to our knowledge of adoption of technology and should be included in studies of the diffusion of innovations