Adding organic residues to the soil is a management practice with the potential to affect the adsorption and transport of pesticides in it (Ahangar et al., 2008; Herrero-Hernández et al., 2011). This practice has now been extended to improve the quality of agricultural soils such as Mediterranean soils, due to their low OM content (García Izquierdo and Lobo Bedmar, 2008). Sewage sludge (SS) from urban wastewater treatment plants is one of the organic residues recording the highest growth in use in recent years. The proportion of SS applied to agricultural soils as an amendment in Spain was 81% of the total generated in 2012 (www.magrama.gob.es). Other biodegradable organic residues of a different nature generated from agricultural and forestry activities are crop residues, animal wastes, or green wastes from pruning (Moreno Casco and Moral Herrero, 2008).