English

Abstract

Paracatu is located in northwest Minas Gerais State, 230 kilometers from Brasilia, the capital of Brazil, and for the last two centuries has been an important gold mining site. With more of 600 ha of acid-sulfate soils across the open cut mine to be revegetated, the company is working to develop a method to reliably establish sustainable vegetation and minimize acid drainage. With this goal, we established a field experiment to evaluate five soil placement combinations to isolate (saddle) and/or cover the acid substrate. We also evaluated five plant species and three combinations to revegetate the materials. The five cover treatments were composed of three layers to: 1) isolate/saddle the substrate; 2) break capillarity and, 3) form a suitable surface material for plant growth. Ore (from mining zone B1) or clay was used as the saddle layer and sand, lime gravel, and sand plus oxalic acid were tested as capillary barriers. Then KCl and NaCl were also added to induce jarosite formation (geochemical barrier) to reduce availability of Fe and As in the drainage. As a cover layer, we tested B1 and local B horizon clay. Each (3) experimental block was comprised of five plots (to test the layers materials) with eight split sub-plots to evaluate the species and combinations. Ten months after establishment, we took samples of the layers to evaluate density and porosity, and the revegetation species were sown. Preliminary results showed that the saddle layer with clay resulted in higher density/less porosity. Non-compacted clay, when used to form the third layer, had higher water retention than B1 ore. This characteristic is very important to reduce water movement into underlying acid-sulfate materials. Among the evaluated species, Crotalaria juncea performed best followed by Melinis minutiflora. For most tested plant species and mixtures, the use of clay as the first and third layer coupled with sand plus KCl and NaCl as the capillary barrier resulted in optimal biomass production.