Evaluation of the soil biological activity in a remediation soil assay using organic amendments and vegetal cover

The recovery of a degraded soil was assayed in greenhouse conditions by applying organic amendments and revegetation with grasses. Two types of organic residues were used: sewage sludge composted with pruning waste (CPW), at 8.5 and 85 Mg ha−1 and sewage sludge treated by thermal drying (TD), at 22 and 46 Mg ha−1. The vegetal cover was established by sowing different herbaceous species commonly used in the revegetation of degraded alkaline soils (100 and 200 Kg of seeds ha−1). The chemical soil parameters and enzymatic activities (alkaline phosphatase, urease, and β-glucosidase) and the vegetal biomass were evaluated. The type of amendment and the doses applied had different effects on the soil characteristics. However sowing dose did not have a significant effect on the parameters analysed. Organic matter was the only soil parameter affected by the interaction between the sowing rate and the amendment dose. The phosphatase and glucosidase activities showed significant correlation with the percentage of N in the leaves and stems, furthermore the phosphate activity was significantly related to the dry weight of leaves and stems.