This article addresses the difficulties faced by farmers who implement new production methods on their land. We discuss the nature of the new competences that farmers must develop, highlighting the complexities of the means they use, the difficulties they confront in this process, and the strategies farmers develop in consonance with the practical knowledge of their profession. The method used includes elements of Ergonomic Work Analysis combined with a case study. Le Boterf's model of the process of constructing competences is used to support the data analysis. The discussion is organized based on an analysis of the evolution of consolidated competences that are re-elaborated for a new agricultural production. The analysis of the strategies and operational modes is introduced, and their contribution to the development of new competences is noted, thus enriching the model proposed by Le Boterf. It is essential to understand the cognitive processes, strategies, and operating modes involved in the development of competences. This procedure provides mechanisms that preserve the opportunity for observation of significant variables in managing variability to be included in the transformation or evolution of work situations and to define the activities that workers will perform.