Present state of soil structure: A comparison of cropland and grassland soils in North Germany

The objectives of this study are to analyse soil structure of representative crop (45 sites) and grassland (58 sites) soils and furthermore to identify differences in soil structure features between these sites in Northern Germany. Using the Compaction Verification Tool (CVT), published by Zink et al. (2011), the present state of soil structure was investigated. Additionally, the orientation of the pore system was analysed by combining the vertical and horizontal hydraulic conductivity. Finally, the influence of soil structure features on crop yield of different arable plants was determined according to the concept of the Muencheberg Soil Quality Rating (Müller et al., 2013). While (sub-) soil compaction within the transition layer, connecting top- and subsoil, was identified on 15 % of the on arable sites, on grassland sites in contrast only a negligible small proportion showed these features. Regarding the correlation of soil quality and crop yield, the results also show differences between arable and grassland sites: on arable soils a correlation was found with a coefficient of determination of nearly 50 % (R²=0.46), on grassland sites in contrast this correlation could not be identified. The conclusions of this study are the overriding importance of soil structure on arable soils regarding plant yield and management efficiency. In contrast, plant growth and yield on grassland soils are more likely determined by management practices (e.g. fertilisation, number of cuts) and the influencing groundwater than by soil structure features. Furthermore, the results show investigation methods should be adapted to grassland soils in order to analyse the complex interactions of soil, sward (including the dense rooting system) and environmental conditions.