Agri-environmental schemes are the main policy instrument currently available in the EU to promote environmentally friendly farming practices. Nevertheless, the adoption rate of these measures is still limited. This paper develops a theoretical framework to explain farmer sign-up decision and tests whether factors affecting this decision differ depending on the level of requirement of each measure. The model is tested with two different AES in Spain implying a low and a high farm management change. Technical factors are found to be most relevant when significant farm practice changes are at stake while the role of farmer characteristics is significant when minor changes are required. In both cases, social capital and farmer attitudes still explain part of the sign-up decision. In order to increase adoption rates, different promotion activities should be undertaken according to different measures, increasing technical suitability when major changes are at stake and enhancing social capital and better targeting to relevant farmers for measures with lower requirements.