Metabolic quotient and specific enzymatic activity in response to the addition of organic amendments to mining tailings

Adding organic amendments to mining tailings to ameliorate extreme conditions that limit plant growth is a common practice in reclamation projects; still, the impact on microbial activity is not commonly considered. This work aimed to explore the use of the metabolic quotient and specific enzymatic activity as indicators of microbial carbon use efficiency in response to adding organic amendments to mining tailings. An experiment in vitro on adding organic amendments: compost, biochar, a mixture of them, and no addition on mining tailing from Taxco, Guerrero, Mexico, was established. Carbon mineralization, microbial biomass, and the enzymatic activity of β-glucosidase, phosphatase, polyphenol oxidase, and dehydrogenase were measured, while specific enzymatic activity and metabolic quotient were calculated. The results showed that microbial activity increased by adding all organic amendments in the following order: compost > mixture > biochar. In the treatment with the addition of compost, we observed a higher carbon mineralization and a greater enzymatic activity. The treatment with adding biochar showed similarities with the control treatment in parameters related to carbon dynamics, such as β-glucosidase, dehydrogenase, and carbon mineralization. This reflects microorganisms’ trade-off between investing energy in searching for resources or using them to improve their biomass clearly to view the specific enzymatic activity and metabolic quotient indicators.