A key challenge for sustainable intensification of agriculture is to produce increasing amounts of food for a growing world population, with minimal loss of biodiversity and ecosystem services. Intensive conventional farming results in high yields, but reduces soil biodiversity and ecosystem functioning. Organic farming can be more sustainable, but generally produces lower yields. In order to facilitate ecological intensification of agriculture, the underlying principles need to be understood and validated in farmers’ fields. Therefore, this project aims at 1) assessing changes in biological, chemical and physical soil properties in organic vs. conventional arable fields and how these properties develop over time since conversion from conventional to organic farming, and 2) unravelling the biological, chemical and physical mechanisms that control these properties. The central focus will be on the role of soil organisms and soil organic matter dynamics. In lab and field, it will be tested how transition towards ecological intensive management can be facilitated, e.g. by soil transplantation. Results will be synthesized in order to develop predictors and indicators of successful soil conversion, and disseminated to farmers through farmers’ organizations.