Microbial applications contribute to more sustainable agriculture by stimulating plant growth, increasing resistance to pests and diseases and relieving stresses from climate change. To stimulate the adoption of microbial applications, it is important to understand the underlying reasons for farmers' adoption decision. In this article, we investigate the behavioural drivers and barriers associated with the likelihood to adopt microbial applications. We employ the Behaviour Change Wheel and its capability, opportunity, motivation-behaviour (COM-B) model. Data were collected via an online survey among 196 Dutch and German arable farmers. We find that trust in microbial applications is an important driver and that lack of knowledge and professional support are barriers for the adoption of microbial applications. On this basis, we recommend three interventions: i) norm creation and enablement, ii) education and learning, and iii) trust building by providing incentives. The acceptance and success of a behavioural intervention depends on the choice of the interventionist. For instance, the role of governmental institutions in enforcing the adoption of microbial applications is perceived as problematic by farmers. Instead, farmers expect advisers and farmer organisations to become active in knowledge transmission and field studies.