Vermicomposting cow manure with earthworms for different lengths of time affects the quality of the resulting organic fertilizer. The study found that shorter vermicomposting periods have high microbial activity, while longer periods lead to physical and chemical changes in the compost. The aromaticity of organic matter increases initially, then decreases. Thirty days of vermicomposting produce good fertilizer, but 120 days are needed for optimal results.