Soil resource assessment of reclaimed bauxite mine lands in Jamaica.

摘要

Bauxite companies in Jamaica are required to restore land disturbed by mining to a condition conducive to productive agriculture. The purpose of this study was to evaluate and compare properties of pre- and post-mined bauxite soils in Jamaica that are relevant in assessing the suitability of these lands for small-scale agriculture. The focus was on soil properties that influence water and nutrient movement and retention, as well as the variation in these properties across the landscape. In addition to standard characterization of pre- and post-mined pedons, mineralogy was assessed by x-ray diffraction and micromorphology was examined in thin sections. Infiltration and sediment loss were measured in the field with a rainfall simulator. A Brilliant Blue FCF dye tracer was applied after rainfall simulation to examine pathways of water movement. Soil maps were produced for pre- and post-mined sites to delineate and compare distribution of soil types with differing depth to limestone bedrock, subsoil material, and slope class.; Bauxite soils in Jamaica were clayey Oxisols formed over undulating limestone bedrock. Pre-mined soils were dominated by variable charge minerals, primarily gibbsite and goethite. CEC was low and almost entirely dependent on organic matter. Pre-mined soils had high infiltration rates and low sediment loss due to stable microaggregate structure. Post-mined soils consisted of replaced topsoil over fill material and/or residual bauxite over limestone bedrock. Post-mined soils had similar texture and mineralogy (with the addition of calcite) to pre-mined soils, but they were generally shallower, higher in rock fragments, steeper, more susceptible to erosion, and considerably more variable than pre-mined soils. Post-mined soils also had higher pH and bulk density in Ap horizons than pre-mined soils. Rock fragments found in post-mined soils could be beneficial because they increase pH in topsoils and increase macroporosity and plant available water in dense subsoils. A comparison of post-mined Ap horizons from different sites indicated that in situ formation of structure, organic matter content, and infiltration rates increased with time after reclamation and revegetation with grass. If managed carefully to limit erosion and loss of organic matter, some post-mined soils have the potential to be used productively for small-scale agriculture.