In the context of a current need for cropping systems adapted to new economic, social and environmental requirements, some agronomists have focused their research and advice activities on the re-design of cropping systems. Such adaptation requires firstly new knowledge on biological and ecological mechanisms supporting cropping systems less dependent on synthetic inputs, and secondly, tools (models, methods, participatory processes in which farmers have an active participation) for their design and evaluation. However, the new knowledge and tools proposed until now mainly address a de novo design of completely described cropping systems. Thus, questions remain concerning how farmers may benefit from these resources in order to undertake progressive technical changes in their own cropping systems, without necessarily having a clear description of one specifically targeted cropping system. This led us to study the way farmers engaged in such technical changes are managing the available knowledge in the design of their action. To this end, different characteristics of knowledge were analyzed, and used to describe the forms of knowledge mobilized or not by farmers. We proceeded with different types of interaction between farmers and agronomists to bring out the relevant characteristics: we surveyed farmers re-designing their cropping system and advisors helping them in this action, we organized meetings with farmers, supported with a set of information materials previously characterized. Axes of description of knowledge characteristics include forms of quantification, ways in which different time scales are addressed, ways in which it refers to uncertainty and risks, ways it refers to agronomic situations, and to onfield action. Knowledge characteristics were studied with the aim to understand how they influence legitimation and validation for action, and how they allow them to act in their particular situation, which will need further research. With a better understanding of what can be actionable knowledge, we finally aim at making proposals for adapting the knowledge produced to support technical changes.