Knowledge investment supporting the adoption of environmentally friendly farm practices is a key driver behind innovation processes in agriculture, yet impact evaluations and financial assessments of existing initiatives remain scarce despite dramatic changes in orientation, organisation and intervention. This report examines the role, performance and impact of farm advisory services, training and extension initiatives in the OECD area to foster green growth in agriculture. Based on a series of case studies, the report discusses a range of methodological issues and the merits of the different types of providers, and identifies best practices in sustainable agricultural management.