Bioindicadores da qualidade do Solo Rizosférico do milho cultivado com resíduos de mineração e aditivos biológicos.

Abstract

Soil quality is measured from the joint analysis of its physical, chemical, and biological attributes; and can be negatively influenced by intensive use and inappropriate management. Due to their high sensitivity, bioindicators are shown to be quite efficient in determining soil quality. Vermiculite mining residues are widely used in agriculture because they contain essential nutrients for plants in their composition. However, vermiculite has low solubility, making it necessary to use biological additives. In view of this, the objective was to evaluate the influence of formulations based on vermiculite mining residues and biological additives on some bioindicators of soil quality. The experiment was carried out in a completely randomized design, with seven treatments and four replications. The treatments (T) comprised two controls: T1= no fertilizer application and T2= conventional fertilization with soluble sources and five formulations based on vermiculite mining residues: T3= formulation 1 (vermiculite residue); T4= formulation 2 (vermiculite residue + bovine manure); T5= formulation 3 (vermiculite residue + bovine manure + Bacillus subtilis); T6= formulation 4 (vermiculite residue + bovine manure + Bacillus amyloliquefaciens); T7= formulation 5 (vermiculite residue + bovine manure + Bacillus subtilis + Bacillus amyloliquefaciens). After 40 days of corn cultivation, the occurrence and density of microorganisms, edaphic respiration, biomass carbon and metabolic quotient (qCO2) were evaluated in the rhizospheric soil. The evaluation of the rhizosphere microorganisms was carried out by the method of drip plating by inoculation of serial dilution of the soil, the carbon of the microbial biomass was determined by the irradiation/extraction method, the microbial respiration of the soil was measured by the capture of the C-CO2 produced in the soil by NaOH in a hermetically closed environment, while the metabolic quotient was calculated by the ratio between the respiration rate and the biomass carbon. The occurrence and density of microorganisms were detected in all analyzed soil samples, highlighting actinomycetes and bacteria. Treatments with biological additives showed the best results for respiration, T2 provided the highest values for microbial biomass carbon and T6 increased qCO2. Therefore, treatments with vermiculite residues, manure and biological additives had a positive influence on corn rhizosphere bioindicators.