Changes in microbial properties and community composition in acid soils receiving wastewater from concentrated animal farming operations

• Wastewater application changed microbial community composition at all sites.
• Wastewater application decreased microbial qCO2 and PLFA stress indicator.
• pH and EC controlled microbial community composition under wastewater application.
• Wastewater application reduced nutrient and acidity stresses on acid soil microbes.

The increasingly intensified animal industry in recent decades has resulted in the discharge of a large amount of wastewater with high concentrations of organic matter and nutrients into the ambient environment, which influences soil properties. In this study, we applied a multi-parameter approach to investigate changes in soil microbial properties and community compositions from three acid soil sites that differed in land-use patterns and histories of receiving wastewater. Wastewater had been applied to the sites for 2–20 years. Compared to controls, soil pH, EC and total nutrients were significantly higher in soils receiving wastewater, as well as average increases of 149 mg kg−1 for microbial biomass carbon and 0.19 mg CO2–C kg−1 h−1 for basal respiration; whereas the metabolic quotient and the ratio of saturated to monounsaturated phospholipid fatty acids decreased by 13% to 31%, and 32% to 61%, respectively. Soil microbial communities of all sites changed with the impact of wastewater application and showed significant increases in bacteria, especially Gram-negative bacteria. The differences in microbial metabolic profiles from all sites were reduced by wastewater application. Soil pH and EC were the two most important factors controlling microbial community composition under wastewater application. These results suggested that wastewater application could reduce stress on acid soil microorganisms by providing more organic carbon and nutrients, and through neutralization of soil acidity.