Interação glifosato e fósforo sobre a microbiota do solo no ecótono Cerrado-Amazônia plantado com soja transgênica

Abstract

The increased use of glyphosate due to various applications in the same crops as well as phosphate fertilizer, can modify the soil microbiota. The objective of the study was to evaluate the interaction of glyphosate and phosphate on the microbiota of a soil with no history of glyphosate use, growing GM soy ( RR ) in 4 differents sampling dates . For this purpose colony forming units (CFU) of fungi and bacteria were counted, in addition, microbial biomass carbon (MBC), basal respiration (BR), metabolic quotient (qCO2 ), and microbial quotient (qMIC) were determined. The study was conducted in a completely randomized design in a 4 x 2 x 4 factorial scheme, 4 glyphosate concentrations (0, 0.9, 45, and 90 kg ha-1 acid equivalent isopropylamine salt), 2 levels of phosphorus (270 and 540 kg ha-1 P2O5), and 4 soil sampling dates (0, 1, 10, and 40 days after treatment application) with 4 replications. In the three-way interaction, at the highest concentration of glyphosate and phosphorus after 40 days, decreased by 7.8% the number of bacterial CFU and increased MBC by 2.3 times, but no significant differences were observed in BR, qCO2 or qMIC for the same treatment. There was a significant reduction in fungal CFU in two-way interactions at the highest concentration of glyphosate. Under the experimental conditions, the highest concentration of glyphosate in duplicate interacting with phosphorus level was toxic to cultured bacteria and fungi, however, it did not interfere negatively on soil microbial activity.