STRUCTURAL REMEDIATION OF AN ALFISOL BY MEANS OF SEWAGE SLUDGE AMENDMENTS IN ASSOCIATION WITH YELLOW SERRADELA (Ornithopus compressus L.)
Wastewater treatment generates large amounts of sewage sludge, which when are disposed in highly degraded soils (with a complete loss of the A horizon and a great part of the B horizon), represent an interesting alternative to recover the aggregate level into soil. Within the hierarchy of soil systems, the aggregate level is the one that integrates soil properties that are directly related to soil sustainability. The aim of this study was to determine the effect of different dose of sewage sludge and an annual legume on the structural recovery of a degraded Alfisol. Sludge was added to soil at 0, 15, 30 and 60 t ha-1 in treatments with and without yellow serradela (Ornithopus compressus L.). After 6 months, the following structural indicators were identified: aggregate distribution, water aggregate stability and bulk density (Da). Results showed that the higher the sludge dose the higher the proportion of macroaggregates and their stability, whereas Da decreased. In spite of the short-term study, data showed that there was a positive effect when amendments were combined with O. compressus L. It demonstrated that degradation is likely to be reversed, thus giving to soil more physical support.