Análises de um substrato remanescente da mineração de bauxita, produção de vermicomposto a partir de resíduo do cogumelo shimeji e seu potencial sobre Megathyrsus maximus cv. Mombaça associado a adubação fosfatada

Abstract

Mining is an important economic activity for the municipality of Poços de Caldas/MG, where despite its recognized economic importance, it can have serious consequences for the environment, as it requires large excavations to remove the ore, leaving a remaining substrate with relevant restrictions for the establishment of plants, mainly due to the loss of organic matter. In this aspect, solid waste is another important environmental problem faced by society, and this is mainly due to high global demographic growth. The agro-industrial sector generates significant amounts of waste, and is divided into many different segments, areas, products and services. Thus, the present work was divided into 3 (three) stages, the first of which consisted of the preparation of a vermicompost from waste from the shimeji mushroom agroindustry. The second in the physicochemical characterization of a remaining substrate from bauxite mining in the municipality of Poços de Caldas. The third was to test the establishment of the forage Megathyrsus maximus cv. Mombaça in remaining substrate from bauxite mining using phosphorus dosages associated with the vermicompost produced. The vermicompost presented the following concentrations in g/kg, respectively for macronutrients: N, P, K, Ca, Mg and S (15.5; 3.5; 2.7; 54.5; 8.4; 2. 5), while the concentrations of micronutrients Zn, Fe, Mn, Cu and B, in mg/kg, were respectively (210.0; 2369.0; 613.0; 52.0; 31.8). When characterizing the remaining substrate, the following average chemical composition was found: pH 5.57; 1.60 mg dm-3 of P; 26.23 mg dm-3 of K; 0 cmolc dm-3 of Al; 1.57 cmolc dm-3 of Ca, 0.24 cmolc dm-3 of Mg, 3.22 cmolc. dm-3 of H, 5.10 cmolc. dm-3 CTC, 36.53% V, 2.35 dag. dm-3 of MO, 2.43 mg dm-3 of Zn, 109.07 mg. dm-3 of Fe, 49.33 mg. dm-3 of Mn, 0.10 mg. dm-3 of Cu, 0.20 mg. dm-3 of B. Clay contents varied from 50.5% to 64.7%, sand from 18.6 to 37.0% and silt from 5.2 to 23.4%. While the soil density varied from 1.009 to 1.245 g/cm3, the particle density from 1.961 to 2.410 g/cm3 and the total porosity from 38.53 to 57.50. Such assessments focused on depths 0-20; 20-40 and 40-60 cm. When establishing the forage, the treatments evaluated were T1 (without compost + 0 phosphorus), T2 (with compost + 0 phosphorus), T3 (without compost + 60 ppm phosphorus), T4 (with compost + 60 ppm phosphorus), T5 (without compost + 120 ppm phosphorus), T6 (with compost + 120 ppm phosphorus), T7 (without compost + 240 ppm phosphorus) and T8 (with compost + 240 ppm phosphorus). As a response, production of dry matter in the aerial part and accumulation of macro and micronutrients in the dry mass produced were evaluated in 2 subsequent cuts (1 cut at 90 days and the 2nd cut at 120 days), as well as the sum of these cuts. For the plant's dry matter production, in cut 1, applying treatment with compost and 240 ppm of phosphorus promoted an increase of 2,283.3 % in relation to not using compost and 0 phosphorus, and in cut 2 there was an increase of 641.6% compared to not using the compound and 0% of phosphorus. The initial establishment of the forage Megathyrsus maximus cv. Mombaça in remaining substrate from bauxite mining in the municipality of Poços de Caldas-MG is limited, even using doses of phosphorus recommended for cultivation, in the absence of application of organic vermicompost. The accumulation of macro and micronutrients in treatments using the Shimeji compound is maximized by doses of P, with the exception of Copper.