9 November 2015This article shows that the introduction of a conditional collective bonus in an agri-environmental scheme (AES) can improve farmers’ participation and increase land enrolment for lower overall budgetary costs. This monetary bonus is paid in addition to the usual AES payment if a given threshold is reached in terms of aggregate farmer participation. Using a choice experiment, we estimate the preferences of winegrowers in the South of France for such a bonus. We show that it contributes to increased expectations of farmers on others’ participation, therefore shifting a pro-environmen-tal social norm and favouring the adoption of less pesticide-intensive farming practices.