Targeted erosion control measures: The backbone of soil-conserving cultivation

The intensification of agriculture over the last 50 years together with a constant change in climatic conditions has resulted not least in a deterioration of the aquatic habitat due to sediment input and siltation in the upper reaches of Bavarian streams. Concerned about this development, the  Fisheries Association Bavaria has launched a project to investigate the main causes of erosion on agricultural land.

By comparing aerial photographs from the 1960s with current orthophotos, by means of a detailed GIS-analysis, the size of agricultural plots in five representative catchment areas was first investigated. In a further step, erosion modelling based on the Universal Soil Loss Equation (USLE) was implemented in two catchment areas.

The intersection of the digitalized land uses from the two time steps showed that despite an almost constant proportion of arable land in the catchment area, the length of the fields had been increased by a third on average and their extent had at least doubled, due to wide-ranging changes in the landscape structure.

By considering the soil loss in the 1960s, that under today's conditions, and by modelling scenarios with conserving farming technics and further-reaching retention measures, conclusions can be drawn as to which measures will be necessary in the future to enable effective soil and water protection.

The erosion modelling showed that the average long-term soil loss - as a result of the USLE - currently exceeds a value of 40 t/ha*a under conventional farming in vast areas of the arable land. Likewise, even with conservation tillage (no-till), isolated erosion spots of more than 20 t/ha*a occur. Since a simple change to soil-conserving cultivation (reduction of the cultivation factor C) will not be sufficient to prevent future erosion events (increased precipitation erosivity R) and constant soil loss, targeted measures (improvement of the erosion protection factor P) against soil erosion must be implemented. This includes nature-based retention measures as wetlands, buffer strips or green waterways. All of which will also help to tackle the upcoming impacts of the Climate crisis. The chosen model supports the localization of the source of erosion as well as the selection and implementation of targeted measures.