Introducing service crops into rotations promotes ecosystem services, but these services are highly dependent on the production of biomass by the service crop (Vrignon-Brenas et al., 2016b). Relay intercropping into winter cereal makes it possible to limit economic risk thanks to minimal competition with cash crops (Gardarin et al., 2022), but sowing the service crop into an established crop is not straightforward. It may hinder its establishment and the provision of services (Vrignon-Brenas et al., 2016a). Complex interactions between cash crops, companion crops, weeds, and various soil and climatic conditions inevitably lead to uneven success (Vrignon-Brenas et al., 2016a). Therefore, the work presented has two objectives, based on two analysis approaches: 1) identify critical success factors based on 15 years of on-farm experimentation, 2) experiment and evaluate the relevance of the specific establishment practices of a legume service crop mentioned and used by innovative farmers.