Organic Compost to Improve Contaminated Soil Quality and Plant Fertility

The use of stabilization techniques for the recovery of trace element-contaminated soils has steadily increased in the last decades. A short-term pot experiment was carried out under semifield conditions using two organic amendments (biosolid compost and "alperujo" compost) and two plant species (Medicago polymorpha and Poa annua). The effect of amendments and plant species on chemical properties (pH, total organic carbon, water soluble carbon, N-Kjeldhal, available K, and available P) and on enzyme activities (dehydrogenase, urease, beta-glucosidase, and acid phosphatase) of two trace element-contaminated soils with different pH values (6.32 and 3.23) was studied. No significant effects of amendment addition and plant rhizosphere were found in the neutral contaminated soil. However, in the acid soil, noticeable effects due to organic amendment addition, especially biosolid compost, were found. Indeed, the most remarkable effects were the increase in soil pH and improvement of soil conditions for the establishment of the vegetation. Moreover, a marked decrease in trace element availability and an increase in the nutritional status of plants due to the improvement of soil fertility were observed in the acid soil. Both plants tested could be acceptable candidates for phytostabilization techniques. The application of amendments is crucial in acidic contaminated soils, whereas in neutral contaminated soils, this application should be evaluated in economic terms.