We use the course-of-action research program to highlight and understand the knowledge mobilized by farmers through practice change experimentation on their farms that are not controlled by a research protocol. We propose methodological tools such as self-confrontation interviews based on video recordings in order to analyze the action in progress and no longer a posteriori. This allows access to a fine grain of analysis of the knowledge and indicators used by farmers during the experimental action. In turns, the material produced and the insights gained can inform the design of collaborative on-farm experiments, as well as contribute to the building of digital resource banks that are valuable tools for training, particularly when related services are lacking.