Drawing on the UK research project, "Farmers' understandings of GM crops within local communities", this paper considers the application of the concepts of communities of practice and networks of practice in the agricultural context. A brief review of theories about communities of practice and networks of practice is given and some of our findings are discussed in the context of those theories. Farmers were found to be a particular type of network of practice, characterised by a weak organisational framework but with a relatively stable network of other communities of practice (or networks of practice) they interact with, which we have called a "web of influencers on practice". Together, farmers' network of practice and their web of influencers on practice represent the whole environment in which learning may occur, and so provide insights into their social learning system. Most farmers have to work at the boundary of their network of practice and their web of influencers, which creates a significant load on their knowledge management. This is in contrast to other networks of practice where only some members take on this boundary brokering role. The paper concludes that these theories (on networks and communities of practice) provide a useful lens through which to view farmers and their practice, highlighting important points for policy. However, in such contexts these theories need to be extended to include the role of a broader "web of influencers on practice". (Contains 2 tables and 2 figures.)