Paclobutrazol in the microbiota of a soil cultivated with ‘Palmer’ mango tree

The soil and climatic conditions of the Brazilian semi-arid region allowed the expansion of the mango crops to serve the internal and external markets, through technologies for managing the production season with the use of plant regulators. This study evaluated the effect of different levels of the plant regulator paclobutrazol (PBZ) on the microbial activity of an Argisol cultivated with 'Palmer' mango, in the semi-arid region of northern Minas Gerais. The work was set up in a randomized block design with five levels of PBZ applied to the soil, equivalent to 0.75, 1.50, 2.25, 3.00 and 3.75 g of active ingredient per linear meter of canopy, in addition to one control, in four replications. For the evaluations, a composite sample formed by 15 sub samples of soil collected between 0 and 0.1 m depth and at 0.3 m around the trunk of the plant was used. PBZ was applied and soil respiration (evolution of C-CO(2) was evaluated every seven days. At the end, carbon in the soil microbial biomass (MBC), soil microbial metabolic quotient (qCO(2)), and percentage of fungi or bacteria were determined by plaque counting. PBZ promoted a negative impact on the soil microbiota, increasing the damage with PBZ levels, indicated by the lower values of microbial respiration and MBC. PBZ levels greater than 0.75 g a.i. per linear meter of canopy promoted a marked reduction in MBC and higher levels of qCO(2), an ecological indicator of microbiota stress.