The objective of this work was to evaluate the microbial activity and phosphate solubilization potential of a soil cultivated with soybean under different phytosanitary management strategies. The experiment was conducted in the field in a Cambic red-yellow Argisol. Ten treatments were arranged in a randomized block design with four replications. The effect of fungicide + herbicide application (endosulphan + tebuconazole) was evaluated in the plots, while weed control management was studied in the subplots (hoed or unhoed control; single-dose or sequential glyphosate application; single-dose fomesafen + fluazifop-p-butil application). Soil samples from the inter-row were collected when plants reached the R2 stage and were used to measure soil respiratory rate, microbial biomass carbon (MBC), metabolic quotient (qCO2), phosphate solubilization potential, and pH. The phyto-sanitary management strategies evaluated did not affect soil respiratory rates. The herbicides tested influenced soil MBC and qCO2, variables directly related to soil quality. Glyphosate applied in a single dose or sequentially, either in combination with endosulphan + tebuconazole or not, led to lower qCO2 values (0.075-0.079 mg μg-1 d-1) and higher MBC (239.64 - 312.82 μg g-1), indicating less soil disturbance. Higher phosphate solubilizing activity, 425 and 472 mg L-1 , were observed for the treatments with single-dose or sequential application of glyphosate, respectively, in the absence of endosulfan + tebuconazole. Agrochemical application on soybean shoots affects the activity of soil microorganisms in the plant rhizosphere.
microbial biomass; transgenic soybean; metabolic quotient
