Fitorremediação do cobre em vinhedos: efeito do fungo micorrízico arbuscular, minhocas e vermicomposto

Abstract

The high copper level in sandy soils of the Campanha Gaúcha, resulting from the successive copper-based fungicides application, lead to environmental contamination and toxicity in cover crops and young vines. The phytoremediation is an alternative to reduce contamination of these soils, but little is known about the interaction of arbuscular mycorrhizal fungi, organic fertilizers and earthworms on the bioavailability and absorption of copper by phytoremediation plants in sandy textured soils. In this context, the objective of the thesis was to evaluate the interaction between arbuscular mycorrhizal fungi and vermicompost or earthworms in the phytoremediation of sandy soil contaminated with high copper level. Two studies were conducted under greenhouse conditions. For that, samples of an uncontaminated sandy soil were collected in an area adjacent to a vineyard. In the experiment I, the soil was contaminated with 100 mg kg-1 of copper, fertilized with five doses of bovine manure vermicompost to grow jack bean (Canavalia ensiformis L.) and inoculated or not with the arbuscular mycorrhizal fungus (Rhizoglomus clarum). In experiment II, jack bean’s were grown in the sandy soil with addition of 100 mg kg -1 of copper with and without inoculation of earthworms (Eisenia andrei) and mycorrhizal fungi. The availability of copper and other nutrients in the soil and in solution, the accumulation of copper and other nutrients in shoots and roots, plant growth and phytotoxicity of copper were evaluated through photochemical efficiency, the concentration of photosynthetic pigments and of the activity of oxidative stress enzymes. The reproduction of earthworms and the concentration of copper in their body compartments were also evaluated. The results show that the vermicompost reduces the availability of copper in the soil and lower doses increase the phytostabilization of the plants while higher doses increase the phytoextractor. The mycorrhizal fungi increase plant biomass and reduce the translocation of copper to shoot by concentrating it in the roots. The interaction between mycorrhizal fungi and vermicompost occurs mainly in lower doses of vermicompost and is reflected in higher phytostabilization of copper. The earthworms reduce the copper content in the soil solution, but increase copper translocation to the shoot. The arbuscular mycorrhizal fungi increase plant biomass and reduce the phytotoxic damage of copper. The interaction between mycorrhizal fungi and earthworms promotes the phytoextraction of copper in the sandy soil. In this way, the inoculation of arbuscular mycorrhizal fungi and the addition of vermicompost, or the adoption of management systems that increase the earthworm population in sandy soils of vineyards is a strategy to increase the phytoremediation of copper by cover crops such as Canavalia ensiformis and reduce the levels of metal in the soils.