Effect of different types of sewage sludge on Cu concentration in soil and pasture in a silvopastoral system established under Pseudotsuga menziesii L

The concentration of heavy metals in the sewage sludge and its effect on the soil and plants is different depending on the process used to stabilise the sewage sludge. The objective of this study was to evaluate the effect of the fertilisation with municipal sewage sludge that has been stabilized using anaerobic digestion, composting, and pelletisation on the total and available Cu concentration in soil and the Cu levels of pasture compared to control treatments (mineral and no fertilisation) in a silvopastoral system under Pseudotsuga menziesii L. The results obtained showed that the composted sludge is the type of residue that increased more the total and Mehlich Cu in the soil due to higher inputs of Cu made with it. However, the annual applications of pelletised sludge implied a higher concentration of Cu in the pasture than the other treatments but without cause harmful effects on plants and animals.