Agroecological Assessment of the Stabilizing Effect of Phosphogypsum on Bacillus subtilis in Sod-Podzolic Soil Contaminated with Pb and Zn

The article presents the results of an agroecological assessment of the stabilizing effect of phosphogypsum at a dose of 150 g/m² on the metabolic activity of Bacillus subtilis in sod-podzolic soil contaminated with Pb and Zn. The enzymatic activity (protease and lipase) of the bacteria and the intensity of microbial respiration (CO₂ emission) were analyzed at concentrations of the studied heavy metals in the arable horizon material at levels of 0.1 MAC, 1 MAC, and 2 MAC. Against the background of high and nearly proportional sensitivity of protease, lipase, and respiratory activity of B. subtilis to a multiple increase in doses of lead and zinc, the stabilizing role of phosphogypsum is clearly expressed. Its application, even in a relatively small dose for an ameliorant (equivalent to 1.5 t/ha), on soil contaminated with Pb at the level of 2 MAC, contributed to a twofold reduction in the inhibitory effect of Pb on the respiratory, protease, and lipase activity of B. subtilis. In the case of Zn contamination of sod-podzolic soil, the application of phosphogypsum is also very effective and leads to a qualitative increase in the biological activity of B. subtilis: nearly 2-fold in lipase activity, 1.8-fold in protease activity, and 1.4-fold in respiratory activity. Keywords: AGROECOLOGICAL ASSESSMENT, BACILLUS SUBTILIS (L), HEAVY METALS, STABILIZATION OF BIOLOGICAL ACTIVITY, LIPASE, PROTEASE, MICROBIAL RESPIRATION, LEAD, ZINC, PHOSPHOGYPSUM