This paper estimates respective roles of private investments in irrigation and local government programs (land reforms, extension services, and infrastructure investments) in the growth of farm productivity in West Bengal, India between 1981-95. Using a farm panel from a stratified random sample of farms from major agricultural districts of West Bengal, we find evidence that private investment in irrigation which reduced irrigation costs for farms played an important role in the growth process. However, the growth in private investment was itself stimulated by tenancy registration and minikit distribution programs implemented by local governments. This channel helps account for the substantial spillover effects of the tenancy reform on non-tenant farms noted in an earlier study. Hence the observed productivity growth was a result of complementarity between private investment incentives and state-led institutional reforms.