Research institution: Federal University of Uberlandia, Institute of Agricultural Sciences
Laboratory: Agricultural and Environmental Microbiology Laboratory
Researcher: Professor Dr. Adao de Siqueira Ferreira – Soil Microbiologist
Abstract
Arsenic is a metalloid widely distributed in the environment and recognized for its high toxicity and carcinogenic potential. In agricultural soils, arsenic contamination may compromise essential biological processes related to ecosystem functioning and crop productivity. This study aimed to evaluate the effects of realgar (As2S4) and arsenic trioxide (As2O3) on microbiological, biochemical, and ecological indicators of soil, as well as on plant growth—promoting microorganisms and soybean seed germination. Controlled experiments were conducted with increasing doses of arsenic applied to incubated soil, followed by the determination of microbial respiration, microbial biomass carbon, metabolic quotient, enzymatic activities, and bacterial diversity analyses through sequencing of the 16S rRNA gene. In addition, biological assays with beneficial bacteria and seed germination tests were performed. The results showed that arsenic increased microbial respiration and the metabolic quotient, accompanied by reductions in microbial biomass carbon and carbon use efficiency, indicating physiological stress in the soil microbiota. Enzymatic activities, particularly dehydrogenase and phosphatase, were significantly reduced, demonstrating a direct impact on biochemical processes associated with nutrient cycling. Experiments with microorganisms revealed high toxicity of As2O3, with Bradyrhizobium japonicum being more sensitive than Azospirillum brasilense, suggesting a potential reduction in the efficiency of microbial bioinoculants in contaminated soils. In germination assays, a progressive reduction in germination percentage and an increase in morphological abnormalities of soybean seedlings were observed with increasing arsenic doses. Furthermore, trivalent arsenic reduced bacterial diversity in the soil, highlighting the potential risk associated with the application of fertilizers contaminated with arsenic to soil microbial communities. Overall, the findings demonstrate that arsenic exerts multiple impacts on soil microbiota, affecting microbial and biochemical properties, microbial diversity, and the performance of beneficial microorganisms used as agricultural bio inputs.
Download full study results
Download Field Study