Thursday, August 9, 2007

PS 67-132: Influence of organic amendment dose on gypsum quarry soil rehabilitation

Ricardo Castelló, Sara Abad, and José M Castillejo. Centro de Ciencias Medioambientales

Open cast gypsum mining rehabilitation is made difficult because the original soil resource is not retained and local substitute materials, that is, soil-forming materials (SFMs), have to be used as growing media. One severe limitation of SFMs is their poor inherent structure and nutrient content, mainly derived from their low organic matter (OM) content. Soil development may be accelerated through the use of soil organic amendments. In this sense, composted residue addition to soil has been considered an effective method for carrying out successful rehabilitation programs under semiarid conditions. However, plant community composition greatly depends on the organic amendment dose applied to the soil so that rehabilitation success is determined by the treatment. The restoration strategy was mainly based on subsuperficial organic amendment (MSW compost) and topsoil replacement. A 6-year field experiment was conducted in 2 landfill materials (gypsum fines and sterile material) to evaluate the effect of the addition of a composted urban residue (at the rate of 0, 10, 30 and 50 Mg ha-1) on the evolution of soil chemical properties of the superficial and subsuperficial layers. The changes produced in the content of total organic carbon (TOC), N (Kjeldahl) and available P, K, Ca and Mg were evaluated using a multivariate statistic tool (discriminant analysis). This evolution was compared with autochthonous gypsum soil profiles. The results showed that moderate MSW compost doses are a useful management practice for the rehabilitation of landfills in gypsum quarries. As it has been established, primarily N and P limited soil development in the initial stages of surface mine landfill rehabilitation.

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