Reduction of microbial load in soil by gas generated using non-thermal atmospheric pressure plasma

Elevation of the microbial load in soil resulting from contamination with organic wastes of biological origin increases the chances of emerging soil-borne pathogens and disturbance of nutrient cycling. We analyzed the potential of gas generated using atmospheric-pressure non-thermal plasma as a tool for reducing the microbial load in soil and its impact on the soil microbial community and fertility. The gas generated by a cylinder-type single pair of dielectric barrier discharge (DBD) electrode plasma inactivated over 90 % of bacterial cells and fungal spores after 5 and 20 min of treatment, respectively, in both suspension and vermiculite. Gas generated using four pairs of DBD electrode plasma eradicated approximately 50 % of bacterial cells and 40 % of fungal spores in nursery soil. It also eliminated approximately 10-29 % of aerobic natural microbiota in field soil after 60 min of treatment. The diversity of microbial species in the plasma gas-treated field soil was slightly lower than that in the untreated soil, and the relative abundances of the phyla Proteobacteria and Basidiomycota were reduced in the plasma gas-treated soil. Spinach plant growth and nitrate levels increased significantly in the plasma gas-treated field soil. Our data suggest that plasma-generated gases can be used for soil sanitation with no drastic changes to the soil microbial community and soil fertility enhancement.