Messung und Modellierung von Änderungen der organischen Bodensubstanz in einem Kurzzeit-Feldversuch

Aim of the study was to determine to what extend data collected in a short term field experiment can be used in the validation of a humus balance model. The „hudycrop“ short term field experiment comprised different cropping systems with a uniform previous crop (spring barley), followed by winter wheat, potatoes, red clover (3 cuts/harvested or mulched), all without additional fertilizer application. The sampling design of the experiment was small scaled, assessing biomass as well as soil organic carbon (SOC) and soil total nitrogen (STN) changes (0 - 30 cm soil depth) in miniplots (each 1 m²). Soil organic matter (SOM) changes were calculated with consideration to bulk density. Parallel to this, SOM change, based on SOC and STN inputs and outputs, was modelled with the humus balance model HU-MOD-2. All confirmed STN changes are in the line with expectations. Further, an overall positive correlation between predicted SOM changes and measured data does occur. Still, estimated STN changes are stronger than those observed. It is concluded that the experimental design provides the possibility to assess STN changes under single arable crops. In addition the model approach is confirmed in principle, but further calibration is necessary. Subsoil samplings will be considered in future experiments to cover most of the functional zone of the soil profile.