Metais pesados em solo e plantas em área com longo histórico de aplicações de fontes orgânicas e mineral de nutrientes

Abstract

The application of organic and mineral fertilizers in agricultural areas, especially, in no-till system and over the years, can promote increased levels of heavy metals and as arsenic (As), cadmium (Cd), lead (Pb), chromium (Cr), copper (Cu), zinc (Zn) and nickel (Ni) in the soil, which may be contaminants and ground water but may also be absorbed and accumulated in plants, and even exported by the grain entering the food chain. The aim of this study was to evaluate how changes of heavy metals in the soil, caused by use of several years of organic and mineral sources, can be reflected in its content in shoots of oat, corn and wheat, and corn and wheat grains. The study was carried in the experimental area of the Department of Soil Science of the Federal University of Santa Maria (UFSM), Santa Maria, Rio Grande do Sul (RS). The experiment was installed in 2004 and the treatments were control (without nutrient application) and application of pig slurry (PS), pig deep-litter (PL), cattle slurry (CS), and mineral fertilizers (NPK). August 2014 soil samples were collected and aerial part of black oats (Avena strigosa) (Winter 2013), maize (Zea mays) (2013/14 crop) and wheat (Triticum aestivum) (Winter 2014) and grains of wheat and maize. The elements analyzed were Cd, Cr, Cu, Ni, Pb and Zn and found out that there was an increase of their content in the soil with frequent applications of organic and mineral fertilizers, however, without exceed the maximum set by CONAMA 420. The crops of oat, corn and wheat showed addition of Cr, Cu, Ni and Zn in plant tissue, but the contents of these elements in corn and wheat grains suggest that the use of organic sources do not represent potential risk to the consumption of grains these cash crops.