Soil quality improvement by the establishment of a vegetative cover in a mine soil added with composted municipal sewage sludge

• A strategy to improve mine soil characteristics to establish plant cover is proposed.
• Soil organic C and conductivity increased with addition of both composted municipal sewage sludges.
• A decrease in enzyme activities was measured as the composted sewage sludge dose increased.
• The higher dose of both composts (10%) led to tomato and ryegrass mortality and reduced their growth.
• Composted sewage sludge (≤ 5%) is the best solution as soil conditioner for plant establishment.

The effect of two different composts of urban sewage sludge was investigated for the establishment of three different plant species (ryegrass, tomato and ahipa) on a mine soil (Alquife, SE Spain). The treatments consisted in a non-amended mine soil, and mine soils amended with composted sewage sludge (CSL) or composted sewage sludge with olive prune wastes (CLV) at 2, 5 and 10% (w/w). Different soil and plant parameters were measured. Soil pH was slightly modified but soil conductivity and soil organic C increased with compost addition and remained constant along incubation. Soil respiration and dehydrogenase activity increased more when amended with CSL than with CLV. At the end of the incubation period a decrease in enzyme activities was measured with increasing CSL doses suggesting a possible toxic effect of CSL above 5%. The plant species responded differently to both composts. In ahipa, the treatments did neither affect the leaf photosynthetic pigments nor the plant growth. In tomato and ryegrass, the 2% dose improved biomass but at 10% increased plant mortality and inhibited plant growth. Composted sewage sludge (≤ 5%) appeared to be the best solution when used as soil conditioner for improving plant establishment in this mine soil.