Consideration of risk management practices in regulatory risk assessments: evaluation of field trials with micro-dams to reduce pesticide transport via surface runoff and soil erosion

Abstract

Background On sloped agricultural fields, water and sediment can be transported downhill as runoff and erosion. This process can cause losses of valuable top soil material, water resources for plant availability, and nutrients as well as transport of plant protection products (PPP) into adjacent surface water bodies. In the European and the US risk assessment for the registration of PPP, runoff and erosion are numerically calculated with the simulation model PRZM which uses the USDA runoff curve number (CN) concept for the water movement. Results from runoff field trials were used to estimate the effect of dedicated management practices in terms of mitigating runoff and erosion, i.e. creating micro-dams between the ridges of potato fields or in maize cultivation on model input parameters. Results Application of different cultivation and tillage techniques (micro-dams/bunds) showed a consistent decrease of the measured quantities of runoff, erosion, and PPP transport as well as of the calculated CN and predicted environmental concentrations in surface water. The results presented here support the approach to quantitatively consider in-field risk mitigation measures (if applied) in the context of regulatory surface water exposure calculations, as proposed by the SETAC MAgPIE workshop. Conclusion Based on these data, a robust case can be made to consider innovative runoff mitigation for risk assessment purposes by, e.g. lowering the CN in the exposure scenarios. In the assessment presented herein, an average decrease in the mean of the derived CN of 86 of 21 points (± 11, 10th percentile: 12) for potatoes could be derived. For maize, the mean calculated CN of 73 was lowered on average by 3 points.

Runoff mitigation via micro‐dams and conservation tillage—Numerical modeling of runoff and erosion from maize field trials

“…The overall mean reduction resulting from the application of micro‐dams with conventional tillage of three points is well in line with the results from Sittig et al (2020; note that the event‐wise evaluation of the 2013 trial was already part of this previous study).…”

“…Comparing the procedure conducted in Sittig et al (2020) using the example of TCM R1 with micro‐dams reveals an f r of 0.69 and an f v 0.68. Consequently, assuming the fraction of runoff water ( f v ) only (Equation ) leads to virtually the same PECsw.…”

Potato Production in Northwestern Europe (Germany, France, the Netherlands, United Kingdom, Belgium): Characteristics, Issues, Challenges and Opportunities

“…Increasing occurrence of water run-off and soil erosion in fields historically not dedicated to potato crop because they have been too hilly or stony is becoming another important issue particularly due to increasing occurrence of extreme precipitation events. Adoption of contour farming, and the use of micro-dams in potato furrows to reduce erosion and runoff and minimize surface water contamination through pesticides (Olivier et al 2014;Sittig et al 2020) also appear as relevant short to mid-term solutions in sensitive fields and are disseminating.…”

The Potato of the Future: Opportunities and Challenges in Sustainable Agri-food Systems

“…Potato furrows in slope fields are a serious concern because of water runoff, soil erosion, and thereby surface water contamination with pesticides and excessive plant nutrients. The use of micro-dams in potato furrows has been demonstrated to minimize these risks and to be a cheap and easy technique to implement (Olivier et al 2014 ; Sittig et al 2020 ).…”