Trace elements in Brazilian agricultural limestones and mineral fertilizers

Knowledge of the concentration of elements other than those found in the “guaranteed analysis” for mineral fertilizers or in other soil amendments is important when considering the nutrient supply to plants. The possible accumulation to toxic levels of these micronutrients and other trace elements in soils and the potential harm to the environment must be considered. In this study, we evaluated a number of mineral fertilizers and other soil amendments that are sold in Brazil for twelve elements: boron (B), iron (Fe), manganese (Mn), copper (Cu), zinc (Zn), nickel (Ni), cobalt (Co), cadmium (Cd), chromium (Cr), lead (Pb), barium (Ba), and strontium (Sr). Sixty samples of several materials were analyzed including rock phosphates and phosphate fertilizers, agricultural limestones, gypsum, nitrogen‐phosphorus‐potassium (NPK) mixtures and micronutrient sources. Limestone samples contained a wide concentration range for Fe, Mn, Ba, and Sr. Relatively high concentrations of B were found in several rock phosphates and phosphate fertilizers, and Zn was detected in fused phosphates. In general, most of samples contained low concentrations of the potentially toxic heavy metals, but considerable concentrations of Cd and Pb were detected in some of the micronutrients sources and high Cr levels were present in fused phosphates.