A Two-phase Process for Revegetation of Acidic Bauxite Tailings in the Amazon Region, Brazil

This paper presents the methodology developed by the association of Mineração Rio do Norte S.A. with Embrapa/Agrobiologia and the Soil Department of Federal University of Viçosa to promote revegetation of tailings ponds from bauxite mining in Porto Trombetas, Para State, Brazil. The tailings have a fine texture (77% clay), are low in nutrients, have low pH (4.5) and high Pfixation capacity. This technology is based upon a two-phase process. In the first phase, seeds of leguminous trees and shrubs, inoculated with N-fixing bacteria and mycorrhizae (VAM fungi), are hydroseeded over the tailings with fertilizer. This initial phase accelerates the tailings drying and incorporates carbon and nutrients into the tailings surface. In the second phase, after substrate consolidation, native secondary and pioneer species are planted with the objective of ensuring more biological diversity and sustainability in the system. Among the evaluated species, Sesbania virgata, S. exasperata, Cecrópia sp., Parkia discolor, Styphnodendron guinensi, Leucaena leucocephala, Hidrocoria corumbosa and Chamaecrista flexuosa have been used with success in the first phase, and Sclerolobium paniculatum, Clitoria farchildian, Eugenia sp., Tapirira guyanensis, Dalbergia spruceana and Enterolobium maximum have been successful in the second phase. Four years after revegetation of the first tailings pond, monitoring results indicate a significant increase of biological activity in the substrate and the presence of different species from natural invasion and regeneration, indicating that primary successional processes are active. These results indicate that the two-phase revegetation process may be more appropriate for the tailings ponds in Porto Trombetas than conventional reclamation practices. Additional