The coordinated DFG research unit „Denitrification in Agricultural Soils: Integrated Control and Modelling at Various Scales (DASIM)” investigates the denitrification process chain in agricultural soils using advanced analytical and molecular biologic methods as well as field studies and various modelling approaches. The aim is to investigate activity and regulation of denitrification in unpreceded spatial and temporal resolution and to use results to develop mathematical models from the micro-scale to the field scale and to improve existing simulation approaches. The anaerobic soil volume fraction, a major control of denitrification, is known to depend on the spatial distributions of gas diffusivity and respiration. However, estimating the anaerobic soil volume fraction has been hampered in the past by the difficulty to quantify its controls. Today, new and improved methods are available to fill those gaps.