Use of biosolids to restore the natural vegetation cover on degraded soilsin the badlands of Zaragoza (NE Spain)

In the semiarid central Ebro valley, the soils of the badlands surrounding Zaragoza city exhibit severe degradation features. Nevertheless, poor land management practices and limiting climatic and edaphic factors make the nat ural regeneration of the soil difficult. The use of sewage sludge as amendm ent for land rehabilitation is increasingly being considered as a technical solution to reverse this environmental degradation and to restore the orig inal vegetation cover. This paper describes the changes produced on the nat ural vegetation cover after application of digested sewage sludge (biosolid s) to three soil types. Experiments were conducted on plots with two differ ent slope levels by applying different rates of biosolids. When increasing rates of biosolids were applied, the biomass yield increase d proportionally, although differences among the different soil types and t he level of the slope were observed. To avoid undesirable side-effects, mai nly referred to soil pollution (salinity and toxic levels of metals), each case has to bf: individually studied. Therefore, prior to application both characterisation of biosolids and determination of the most suitable applic ation rates to be used are required. (C) 1999 Elsevier Science Ltd. All rig hts reserved.