Long-term effects of mine soil reclamation using different amendments on microbial and biochemical properties in southeast Spain

Microbial biomass carbon, soil respiration and enzyme activities were measured five years after reclamation of a polluted soil affected by former mining activities in SE Spain. This abandoned mine site contains materials of high Fe-oxyhydroxides, sulphates, and elevated contents of potentially leachable heavy metals due to extreme acidic conditions. Thus, soils have scarce or null vegetation due to very poor properties including low soil organic matter. A field trial was established in 2004in which different experimental plots were designed, using marble wastes, pig manure and sewage sludge as amendments to recover soil properties. Results show that all biochemical properties were higher in treated soils than in control, despite soil organic matter being similar amongst the treatments. As general pattern, biochemical properties showed higher values after application of pig manure than after application of sewage sludge. The different doses used did not have a great effect, being only significant for b-glucosidase, phosphodiesterase and arylsulfatase. This study confirms the high sensitivity of biochemical properties in the evaluation of soil quality and reactivation of nutrients cycles.