The preservation of soil fertility is a central focus in organic agriculture. Management of soil has an impact on soil organic matter and nutrient regime and therefore on soil fertility. Five departments of the Faculty of Organic Agricultural Science at the University of Kassel, one department of the Faculty of Agicultural Science of the University of Göttingen and the Thünen-Institut of Climate-Smart Agriculture in Braunschweig participate at the interdisciplinary Research Training Group 1397. They study the underlying processes of soil organic matter and nutrition turnover according to management and fertilization and thus help to account for long term preservation of soil fertility in agricultural systems.