Possibilities of restoring homeostasis of soil exposed to terbuthylazine by its supplementation with HumiAgra preparation

Terbuthylazine is an active substance of herbicides that has been commonly used in the European Union Member States and also on other continents. It has been included into the plant protection strategy as a substitute of atrazine. Terbuthylazine was expected not only to protect plants against weed infestation but also not to contaminate the natural environment. For this reason, a study was conducted to determine terbuthylazine impact on the counts of soil microbiota, the structure of bacterial and fungal communities, and activities of soil enzymes. In addition, the study evaluated the efficacy of soil supplementation with a HumiAgra preparation in terbuthylazine detoxification. Terbuthylazine was found to promote the development of Actinobacteria bacteria and to inhibit that of Acidobacteria, Chloroflexi, Firmicutes, Gemmatimonadetes, and Proteobacteria. In addition, the terbuthylazine-treated soil offered favorable conditions for the development Ascomycota and Mortierellomycota fungal, but less beneficial ones for the development of Basidiomycota and Aphelidimycota. Terbuthylazine also contributed to changes in the activities of soil enzymes. Soil supplementation with the HumiAgra preparation stimulated the proliferation of organotrophic bacteria and actinobacteria, while inhibited fungal development. The preparation elicited a beneficial effect on Chloroflexi, Firmicutes, and Gemmatimonadetes bacteria, and an inhibitory effect on Acidobacteria, Actinobacteria, and Proteobacteria, especially in the terbuthylazine-contaminated soil. In addition, it increased the OTU number of fungal belonging to Ascomycota, and reduced OTUs of fungal belonging to Mortierellomycota, Basidiomycota, and Aphelidimycota. Finally, its stimulated activities of all enzymes tested and effectively reduced terbuthylazine content in the soil. The study results enable concluding that terbuthylazine disrupted the soil homeostasis and that the HumiAgra preparation proved to be a better biostimulant of the enzymatic than microbiological activity of the soil.