Mean soil cover comprises a spatial and temporal component. Spatial soil cover changes, for example, through the growth of crops, reaching almost 100% before harvest. Temporally distinctive changes in the degree of soil cover are found when the seedlings become visible at the surface, but also after ploughing. A high degree of soil cover has several positive effects: for starters, it reduces nutrient leaching and soil erosion, and favours biodiversity.
A soil-cover figure of less than 30% is viewed as critical for nutrient loss and erosion. Soil cover over a specific time period can be given in so-called ‘soil cover days’ (SCDs). The number of SCDs is calculated by adding up the daily soil-cover values (between 0% and 100%) over the time period considered. Thus, 1 SCD can mean that a plot is 100% covered for one day, or 50% covered for two days.
In the context of the SAEDN, soil cover is calculated as a spatially and temporally weighted average for each farm, with both crop-residue cover and living-vegetation cover being taken into account (Büchi et al. 2016).