This study summaries the ongoing sludge trials on arable land in Skåne, which is now in its 45th year. Normal sludge application in combination with mineral fertiliser has resulted in a 4% increase in yield, 10% higher humus content, increased levels of plant-available phosphorus in the soil (50-250%) and no or little increase (0-6%) in the soil content of the heavy metals lead, cadmium, chromium and nickel, but increased zinc (6-14%), mercury (20-28%) and copper (41-51%) levels in the soil compared to the application of mineral fertiliser alone. Plant uptake of lead, cadmium, chromium, mercury, nickel and zinc did not differ between sludge-fertilised and non-sludge-fertilised test plots. For copper, plant uptake was marginally higher in sludge-fertilised plots.

A special study on PFAS showed an accumulation of PFAS in soil related to the amount of sludge applied and that earthworms have higher levels of PFAS in themselves when sludge is spread. In autumn wheat harvested from sludge-fertilised plots, only PFOS and a PFCA precursor were detected, but only in roots and harvest residues. No PFAS could be detected in the wheat kernel. Further studies of uptake in different crops are needed to estimate the risk of PFAS when spreading sludge.