The effects of fertilization with anaerobic, composted and pelletized sewage sludge on soil cations and pasture production in a silvopastoral system under Quercus rubra L.

In Europe, sewage sludge has to be stabilized before being used as fertilizer in agriculture. Depending on the stabilization process that is used, sewage sludge has different characteristics, nutrient contents and soil nutrient incorporation rates. This study aimed at evaluating the effect of municipal sewage sludge stabilized using anaerobic digestion, composting and pelletization on saturation percentage of cations in the soil exchange complex and pasture production compared with control treatments (mineral and no fertilization) in a silvopastoral system established under Quercus rubra L. in Galicia (Spain). The application of the dose of pelletized sewage sludge in several times implied an increase of pasture production in the understory which reduced the Ca saturated percentage in the soil exchange complex and therefore increased the Al saturated percentage compared with the other types of sewage sludge evaluated.