Effect of Eisenia foetida earthworms on mineralization kinetics, microbial biomass, enzyme activities, respiration and labile C fractions of three soils treated with a composted organic residue

The aim of this work was to assess and compare the influence of Eisenia foetida Savigny earthworms on C mineralization rate, labile C fractions (water-soluble C and water-soluble carbohydrates), microbial biomass C, and enzyme activities (dehydrogenase, urease, phosphatase and β-glucosidase) in three soils of varying texture treated with a composted organic residue and cropped with Avena sativa L. Mineralization decreased with the addition of earthworms to the sandy and clay-loam soils, especially in sandy soil (by about 4 μg CO2-C g−1 day−1). There were no significant effects on the amount of CO2 evolved from clay soil due to the addition of E. foetida. The addition of E. foetida to sandy soil significantly decreased microbial biomass C and increased microbial metabolic quotient the qCO2 (CO2-C to biomass C ratio). The addition of E. foetida did not affect the microbial biomass or the qCO2 of the clay-loam and clay soils.