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Restoration of degraded soils with organic wastes could be a feasible practice to minimise erosion in the Mediterranean area. In this work we have applied three different organic wastes to three different soils of degraded areas. Two composted and one uncomposted sewage sludges were used for the restoration of soils. The soils were: one soil of overexploited agricultural area, one burned forest soil, and one shrub-land soil degraded by environmental conditions (annual rainfall similar to 300 mm) and erosion. The experiment was carried out in field conditions. After the addition of organic amendments, some soil samplings were made. Different soil properties were determined: physical (aggregate stability %), chemical (pH, salinity, available nutrients) and biological, (microbial biomass carbon, soil respiration rate). Beneficial and detrimental results have been obtained in the earliest stages (around three months after organic application) of this long-term restoration experiment. In the first 90 days after wastes application one of the positive effects in the shrub-land soil has been the increase of around 1.7-fold in soil microbial biomass carbon with respect to untreated soils. But, in some treated soils negative effects have been observed too, such as an increase in electrical conductivity. This negative effect is reversible and temporary, and may disappear after rainfalls. Therefore, the application of the different organic wastes to degraded soils could be a good restoration management.