EFFECT OF CHEMICAL INDICATORS AND RESPIRATORY ACTIVITY ON THE RESIDENCE TIME OF VERMICOMPOSTS

Vermicompost is considered an environmental quality to manage agricultural residues because it improves the structure, provides nutrients to the soil, and helps to mitigate the impact on the environment. The objective of this study was to know the residence time by applying a kinetic model of carbon mineralization, evaluating chemical and biological parameters obtained during the processing time of a vermicompost. Earthworms (Eisenia fetida) were used comparing different doses of residual sludge (LR) at 0, 10, 20 and 40 Mg, keeping constant the dose of domestic waste (RD) and cattle manure (EV) at a ratio of 1:1 (dry basis). An AxB factorial design was used, where A represented the LR dose and B the type of residues (RD and EV); thus, eight treatments with nine replicates were compared. The pH, organic matter (MO), total nitrogen, C/N ratio, respiratory activity, C mineralization, and residence time were determined. The results of the treatments indicate a slightly alkaline trend. MO was different among treatments, with higher percentage of MO in EV and LR with 40 Mg of LR (28.92 ± 10.78 %, F (7,88) = 2.63, p ≤ 0.01). The percentage of total N was low, but the treatment containing 40 Mg of LR and RD (1.04 ± 0.62 %, F7,88 = 3.87, p < 0.01) stood out. C/N ratios < 20, indicating stability, were recorded in the treatments with LR and EV. The vermicompost obtained by 40 Mg of LR and EV complied with a minimum residence time (less than 70 days) during its processing, which makes it a highly recommendable option for application in agriculture.