Disponibilidade de nutrientes e metais pesados tóxicos em plantas medicinais cultivadas em solos de diferentes texturas e sob diferentes condições de adubação

Abstract

The cultivation and use of medicinal plants has followed man s evolution through centuries. Since the earliest civilizations, plants were already used for different purposes, especially for eating and in the treatment of diseases. Many recent surveys are pointing to the knowledge of sustainable agronomic practices that can provide higher quality and utilization of the active principles of interest of medicinal plants aiming to provide, for example, better environmental and nutritional conditions to plants. The aim of this study was to determine nutrient availability and content of heavy metals in two species of medicinal plants, Ocimun basillicum (Basil) and Calendula officinalis (Marigold), when subjected to different treatments with organic fertilization and conventional fertilization in different soil textures (sandy and clayey). For this, two similar experiments were conducted with each of the two species chosen in which the treatments were arranged in factorial scheme (2x2x3) arranged in a completely randomized design (CRD), being two soil textures (clayey and sandy), two forms of fertilizer (chemical and organic) and three levels of fertilization (unfertilized, the recommended dose and twice recommended dose) totalizing 12 treatments with four replications. The experiment conducted with basil plants, It was concluded that the clay soil favored the availability of P, K, Ca, Cu, Zn, Fe, Cd e Pb; the sandy soil favored the availability of N, Mn e Cr. The organic fertilization provided higher levels of N, P, Mg e Zn, while chemical fertilizer showed the presence of toxic heavy metals (Cd e Pb) in the sources of NPK used. The experiment conducted with marigold plants,the results showed that clayey soil favored the availability of N P, K, Mg, Cu, Zn and Fe; the sandy soil favored the availability of Ca, Mn, Pb and Cr. The organic fertilization provided higher levels of P and Fe, while the leaf tissue of marigold plants fertilized with chemical fertilizer showed higher concentrations of K and Mn. Marigold plants grown in clay soil were higher and had the highest average of dry volume and fresh volume.The results obtained with both experiments showed that the use of fertilizer improved the availability of heavy metals in the tissue of medicinal plants. The clay soil and organic fertilization favored the increase of CTC in the soil and the availability of nutrients that are essential to plants in general