Long-term Monitoring Shows Effective Measures for Reducing Soil Erosion

A long-term field study conducted by Agroscope, the Soil Protection Agency of the Canton of Bern and the University of Bern shows that soil erosion on arable land can be significantly reduced with the right measures – in particular, conservation tillage practices.

Both in Switzerland and worldwide, erosion ranks as one of the most important threats to the resource soil. Structural change – increased average plot size and the use of larger and heavier tillage machinery – is leading to an increased risk of erosion. More frequent and more intense torrential rains are predicted owing to climate change. This can result in erosion damage on unprotected plots. The increase in winter precipitation, especially in the form of rain rather than snow, can lead to increased erosion in winter.

24 years of erosion monitoring in Frienisberg

A field study on soil erosion on arable land was conducted over a 24-year period on 210 arable plots in the Frienisberg region (canton of Bern). The transdisciplinary and participatory research approach is characterised by a close, longstanding collaboration between Agroscope, the Cantonal Soil Protection Agency of Bern and the University of Bern. To date, a total of 130 erosion-damage mappings have been made and around 2500 erosion systems have been recorded and documented throughout Switzerland. Numerous field courses, excursions and workshops with Swiss and international experts from practice and research have also taken place. In addition to amassing scientific knowledge, the main focus of the studies has been on developing tools for practice and enforcement.

Soil erosion varies over space and time

Because average annual soil erosion figures vary widely over time and space, long-term measurements are crucial. On average, 55% of the erosion occurred in the winter half-year, 45% in the summer half-year. Consequently, mitigation measures must be taken in both spring- and autumn-sown crops. Often, only part of a plot is affected by erosion. Slope depressions, headlands and linear features concentrating runoff (tramlines, furrows) often trigger local erosion damage on a plot.

Conservation practices offer the most efficient protection

Conservation tillage practices like no-till, strip-till, rotary strip seeding and mulch-seeding are the most efficient erosion protection measures, reducing soil erosion by an average factor of ten.  This tillage method was used in an average 7% of cases in the first twelve years of the study, Thanks to cantonal and national support programmes as well as our research project, it was possible to increase this share over the further twelve years of the study to an average 72%. Over the same period, average soil erosion per plot and year fell by 78%.

Water pollution from soil erosion

Hydraulic shortcuts such as inlet shafts and maintenance shafts, which are currently being discussed in connection with plant-protection product inputs into watercourses, were mapped throughout Switzerland for the first time back in 1997 and identified as major sources of sediment, phosphorus and plant-protection product input into watercourses. In the Frienisberg region, around 20% of soil erosion on average reached a watercourse.

Tools for enforcement and practice

The Erosion Risk Map and the Watercourse Connection Map of Switzerland (https://map.geo.admin.ch/) were developed and validated in the area under investigation. Various factsheets and other tools were provided for the national enforcement of statutory regulations concerning soil erosion and for international projects.