Caracterização e potencial agromineral de um regolito de Riachão das Neves-BA

Abstract

Ensuring the nutritional quality of the soil is crucial to optimize crop productivity. Fertilizers, therefore, must provide the essential nutrients for plant growth, however, increase production costs. Rocking consists of a technique of applying waste rock powders directly to the soil, aiming to restore essential nutrients and also to correct the pH of the medium. The rochagem involves applying rock powder residue directly to the soil, with the aim of restoring essential nutrients and correcting the pH of the medium. The study proposes to evaluate the mineralogical composition, solubility of nutrients in aqueous medium of the rock powder manufactured by the company GEOFERTIL in the mine of Riacho do Pintor, located in Riachão das Neves, Bahia and to evaluate the changes in soil characteristics. The water retention capacity was measured by slowly adding 25 mL of water to 20 g of dry rock powder, which resulted in a water retention capacity of 44.11%. Solubility tests were carried out with citric acid solution and acetic acid at 0.02 mol L-1 in water at pH 6.5. In intervals of 0.5, 2.0, 8.0, 32, and 128 hours, one gram of rock powder was mixed with 40 mL of the solutions. Rock powder Geofertil and Ekosil were used in an incubation assay on sandy and clayey soils at doses of 6, 12 and 24 tons per hectare for both soil types. In addition to limestone and dolomite, doses of 2.42 and 2.32 t/ha for clay soil and 1.32 t/ha and 1.52 t/ha for sandy soil, respectively. The Zero Charge Point of the Geofertil rock powder indicates that when adding it in soil with pH greater than 4.12 will occur the predominance of negative charges. Potentially toxic elements were quantified and all the concentrations found were lower than the maximum established in the normative instruction Normative No. 5 of 2016 MAPA. The elements solubilized as a function of time were expressed in accumulated quantity as a function of accumulated time, and phosphorus (P) released accumulated amount of 260.7 mg/L in 42.5 hours of contact. Potassium released 454, 214 and 130 mg/L of K accumulated in 42.5 hours for the extractors water, citric acid and acetic acid respectively. Calcium and Magnesium had similar behavior in the release of nutrients, totaling at the end 153 and 191 mg/L in the accumulated time of 170.5 hours for calcium and magnesium respectively. Silicon also had a similar behavior when comparing the extractors, but it stands out for citric acid in the accumulated time of 42.5 hours, releasing 298.12 mg/L of (Si). The elements iron and manganese stood out with citric acid releasing 3476 and 1028 mg/L in 170.5 hours accumulated. In the incubation time of 25 days the powders of GEOFERTIL and EKOSIL rocks were not able to correct the soil pH in comparison with the calcitic and dolomitic limestones. The results showed that Geofertil rock powder can provide potassium and some other micronutrients, besides causing changes in the dynamics of nutrient release to the soil solution mainly in sandy soils, Its greatest potential refers to water retention capacity, which can greatly contribute to alleviate water stress in regions and periods of low rainfall.