Sewage sludge use in agriculture is promoted by the European union since the normative of cleaning waters related to the compulsory use of depuration plants in all cities over 2000 inhabitants was finally implemented in 2005. The USC has been conducted long-term experiment research of application of different sewage sludge doses in silvopastoral systems. Main results shown that sewage sludge can be successfully used as fertilizer for both tree and pasture development, with reduced toxicity for animals when plant production is considered in both very acidic and acidic soils. However, the recycling of nutrients has to be considered as heavy metals uptaken by the trees appears in the soils when the leaves fall down. This paper provides an overview of the main findings in acidic soils of the long-term results after application of sewage sludge in soils.