Mineral fertilization pollutes soil with cadmium and uranium

A study by the University of Bern investigated whether levels of arsenic, cadmium, lead and uranium are elevated in soils of arable farming areas with high phosphorus-containing mineral fertilizer applications compared to soils without mineral fertilization, how high the pollutant loads from mineral fertilizers are and whether there is a risk of accumulation. For the study, 400 soil samples from 228 sites from the NABO monitoring network, the biodiversity monitoring, the cantonal soil monitoring (AG, BL, FR, SO) and the long-term fertilizer experiment DOK were analyzed.

The study provides no evidence that arsenic and lead are significantly introduced into arable soils by mineral fertilization. For cadmium, the arable sites studied show enrichment in the topsoil compared to the subsoil. Arable soils show on average higher uranium contents than meadows and pastures, and the arable topsoils show higher contents than subsoils. The results of the status study were confirmed by the results of the trend studies at six selected NABO sites. The authors conclude with recommendations to avoid uranium and cadmium accumulation and to improve monitoring. They likewise outline the need for research.

No acute danger
Even if no acute environmental or health hazards are to be assumed, it is nevertheless important to avoid the input of harmful elements through fertilizers as far as possible in the interests of precaution. Adjustments to agricultural policy have led to a situation in which only a quarter of the amount of mineral phosphorus fertilizer is applied today compared to 1990.

Mitigate risks

In order to reduce the risks associated with fertilization, the FOAG is in constant contact with other federal offices, research, practice, and the cantons. It is important that the existing cadmium limit value is complied with. In the medium term, efforts will focus on the recovery of nutrients and the use of recycled mineral fertilizers. The aim is to close the material cycles as far as possible and thus to reduce the use of P-containing mineral fertilizers to a minimum as well as to make their use more efficient.