Do bioinoculants improve the recovery of mining waste with the application of Technosols for pastures?

Abstract

Soil inoculation with mycorrhizal fungi and/or other microorganisms is used to improve plant development in the environmental recovery. This study aimed to evaluate the effectiveness of mycorrhizal fungus+Trichoderma (bioinoculant) in the recovery of tailings for pasture growth, together with the use of a eutrophic-alkaline Technosol. A mesocosm experiment was carried out in a greenhouse conditions with three treatments (Tailing+Bioinoculant; Tailing+Technosol+Bioinoculant; Tailing+Technosol) where a pasture was sown. The Technosol was elaborated from industrial wastes and applied at 400 g/kg. Biomass production and composition of nutrients and potentially toxic elements were quantified at two periods (T1: five of growth; T2: three months after T1), and the substrata were physicochemically characterized. The tailing, even with the bioinoculant, presented pH≈2.7, low fertility, high available multielemental concentration, and without any germination. The Technosol improved the tailings characteristics (pH~8.3, increase of organic C and available nutrients, between, and decrease >95% of the availability for most of potentially toxic elements) allowing considerable pasture development. Independently of the bionoculant application, plant productivity (257-370 kg/ha) and soil characteristics were similar between Technosols treatments (except available Fe in soils). The elemental concentrations (except Mn) in the shoots from pasture were sufficient/normal, not presenting a risk for consumption by domestic animals. Therefore, the rehabilitation and valorisation of tailing with Technosols for pastures is feasible but, the use of the bioinoculant was not advantageous.