CHARACTERIZATION OF AN ACIDIC VOLCANIC ROCK MINING RESIDUE AND ASSESSMENT OF ITS NUTRIENT RELEASE POTENTIAL FOR STONEMEAL
The fertilization of soils with application of comminuted acidic volcanic rock is an alternative that can partially or completely replace the use of soluble chemical fertilizers. This technique is called stonemeal. Nutrient extraction studies were conducted in the laboratory to determine the capacity of a rock dust sample from a crushing facility in Nova Prata Municipality, Rio Grande do Sul. The study material was an acidic volcanic rock residue collected in the Extraction Industry Union Quarry, Nova Prata, Rio Grande do Sul, with a particle size range of < 0.6 mm. Chemical, mineralogical, physical and physicochemical analyzes of the rock dust were performed. Nutrient extraction tests were also carried out in 2% citric acid solution (CA) and in a solution of organic acids from the rhizosphere (OAR) for two temperature levels: 25 °C and 50 °C. The nutrient release studies were performed in duplicate by extraction and subsequently, the concentrations of Ca, Mg, K, Fe, Cu, Mn and Zn were determined.
There was a significant variation in results between the two extraction solutions: the 2% CA solution resulted in higher release of Ca and the OAR solution increased the release of K.