Plastic products are omnipresent in our everyday lives and are so versatile and efficient that it is difficult to imagine modern agriculture without them. However, in combination with littering and as foreign materials in digestate and compost fertilisers, they are also the main source of plastic inputs on agricultural land. Using material flow analysis, this study estimates the annual amount of plastic spread on agricultural land in Switzerland at 16,000 tonnes. Around 160 tonnes of this annual figure remains in the soil, which can lead to concentrations of up to 0.02 ± 0.01 % (200 ± 100 mg kg–1) over the years. The few ecotoxicological studies available to date describe effects on soil organisms starting from a plastic content of 0.1 %. On the basis of current knowledge, therefore, there is no risk to soil organisms in Switzerland. However, a more reliable risk assessment would require more in-depth studies on exposure and the effects of plastic in the agricultural environment. As plastic is generally undesirable in soil and degrades only very slowly, we recommend further refining the use of agricultural plastics and continuing to reduce the foreign material content of digestate and compost fertilisers in order to minimise plastic inputs.
Plastic waste flows in Swiss agriculture and their risk potential for soils