Municipal wastewater biosolids are nutrient-rich residuals with potential as crop fertilizer, if their alkalinity does not adversely affect soil biochemical processes. This study assessed the potential soil enzyme activity after three annual applications of biosolids in a conventionally tilled field under silage corn (Zea mays L.). Biosolids were municipal wastewater sludge treated by mesophilic anaerobic digestion, lime stabilization, or composting, compared with urea fertilizer and an unfertilized control. Generally, the potential soil enzyme activity did not change with biosolids application, but the N-acetylglucosaminidase activity increased in soil amended with lime-stabilized biosolids, which also had higher soil pH and greater soil NH₄⁺ concentration.