This chapter explores the ways in which different forms of farming knowledges are produced, disseminated and influence farmers' willingness or ability to make changes to their farming systems. It proposes two concepts from Morgan and Murdoch: a simple classification of forms of knowledge, and the idea of networks to help understand relations among possessors of knowledge and the process of disseminating knowledge. Many farmers have exhibited a strong buy-in to the productivist discourse since the 1960s. It concurs with farmers' understandings of their role as producers of food commodities using conventional methods. The main external, expert sources of information used by farmers are Teagasc (a semi-state agency), and the Department of Agriculture, Fisheries and Food (DAFF). Teagasc provides advisory, training and research services to farmers, the agriculture and food industry and the wider rural community.