Granular soil structure indicates reclamation of degraded to productive soils: A case study in southeast Spain

Abstract

Arocena, J. M., van Mourik, J. M. and Faz Cano, A. 2012. Granular soil structure indicates reclamation of degraded to productive soils: A case study in southeast Spain. Can. J. Soil Sci. 92: 243–251. Accelerated conversion of degraded landscapes in mining areas to productive ecosystems requires stimulation of soil formation. The evolution in microstructure and changes to chemical properties in metal mine wastes 5 yr after amendments with pig manure, sewage sludge and marble waste is reported. Mine wastes had <1% organic carbon, <0.05% total nitrogen, pH∼2.0, electrical conductivity up to 20 dS m−1and high concentrations of metals such as 22000 mg zinc kg−1and 7000 mg lead kg−1. After 5 yr, one time amendment increased total carbon (g kg−1) from 1.4 (control) to 5.6 (marble waste +sewage sludge) to 8.3 (marble waste+pig manure). Soil pH in amended plots was 6.0 compared with 2.8 in controls. Micromorphological characteristics clearly showed that primary and secondary calcite serve as active sorption sites for organic matter. These calcitic zones were areas conducive to root growth. Soil microstructure in amended mine wastes was dominantly granular, resulting from activities of soil organisms such as fungi and enchytraeds. Results suggest organic matter can be effectively enriched in mine waste deposits through simultaneous additions of pig manure, sewage sludge and calcite. Soil amendments promoting formation of granular structure can accelerate establishment of productive landscapes in degraded mine sites.