Purpose: The paper investigates the multi-actor processes of knowledge co-production in the implementation of researchbased on-farm demonstration with a focus on collaboration arrangements and areas of contention. Design/Methodology/Approach: Building on science studies and literature on farmer participatory research and extension, the paper uses a case study of a demonstration project in Latvia to analyse the processes of agenda-setting, knowledge co-production and communication in an arrangement that brings together farmers, advisors, and scientists. Findings: Multiple tensions exist between the perspectives and practices of stakeholders along the different stages of the on-farm trial and the demonstration process, leading to a series of trade-offs between initial conceptions and practical implementation. The challenges relate to balancing expert-and user-driven processes, negotiating claims for scientific knowledge, and integrating knowledge transfer and peer-to-peer learning. Practical implications: The analysis allows using evidence-based knowledge for designing on-farm trials and demonstrations that take account of the possible pitfalls in multi-stakeholder collaborative arrangements. Theoretical implications: The paper demonstrates the applicability of the concepts of co-production of knowledge, scientific knowledge claims, and expertise for the investigation of agricultural knowledge production and its governance. Originality/Value: The study contributes to the body of literature on evaluations of farmer participatory research and extension and the broader debate on the strengths and shortcomings of participatory arrangements by adding qualitative insights into their process dimension.