Research-based on-farm trials and demonstrations are becoming a norm in agri- cultural research and extension involving collaboration between scientists, advi- sors, and farmers. There is, however, a rather large variation in the engagement mo- dels underlying this farmer participatory research and extension depending on the form and intensity of farmer involvement. While the very idea of farmer engagement is laudable and is increasingly promoted by various policy instruments, it is impor- tant also to critically look at these multi-actor processes of knowledge co-produc- tion and the existing areas of contention not to over-romanticize these collaborative arrangements by identifying, acknowledging and addressing the various challen- ges that come with it. Collaborative arrangements involved in on-farm trials and de- monstrations can be demanding in terms of aligning and integrating the different needs, expectations, skills, experiences and knowledge resources possessed by the involved parties, not least in terms of specifying the research problem and in ensu- ring a common and shared framework for the practical implementation of the trial, data gathering and communication. Yet, there are still many benefits that compen- sate for these hardships when considering the social and technological potential of on-farm experiments and demonstrations to promote innovative farming practices.