Effect of Different Substrates on Composition and Quality of Vermicompost

Abstract

A field experiment was conducted during September 2024 to March 2025 at the Vermicompost Unit, Division of Soil Science, College of Agriculture, Pune, to evaluate how different organic substrates, in combination with microbial consortia, affect the composition and quality of vermicompost. We hypothesized that substrate type, when integrated with microbial consortia, would significantly influence nutrient enrichment, microbial activity, and heavy metal content in the final vermicompost product. The experiment followed a completely randomized block design with seven treatments—tree litter, button mushroom spent compost, wheat straw, soybean straw, coconut coir, sugarcane trash, and farmyard manure—each replicated three times. Defined microbial consortia were introduced during composting to enhance microbial-mediated decomposition. Vermicompost derived from tree litter showed superior quality, recording the highest organic carbon (23.96%), total nitrogen (1.93%), available phosphorus (0.68%), and potassium (1.25%). Micronutrient concentrations (Fe: 1575.07 mg kg⁻¹, Mn: 426.38 mg kg⁻¹, Zn: 299.30 mg kg⁻¹, Cu: 184.95 mg kg⁻¹) were also highest in the tree litter treatment. Additionally, heavy metal content (Cd: 0.28, Pb: 0.49, Cr: 0.36 mg kg⁻¹) was lowest in this treatment. Enhanced microbial enzyme activities—including dehydrogenase (34.90 μg TPF g⁻¹ 24 hr⁻¹), acid phosphatase (3.84 μg PNP g⁻¹ 2 hr⁻¹), and urease (118.42 μg NH₄⁺-N g⁻¹ day⁻¹)—further confirmed improved biological quality. Tree litter vermicompost also exhibited lower bulk density (0.73 g cm⁻³), finer particle size (<4 mm), and optimal color (very dark greyish brown, 10YR3/2). These results suggest that tree litter, when combined with microbial consortia, serves as an optimal substrate for high-quality vermicompost production, with enhanced nutrient content, reduced contaminants, and improved biological activity—offering practical benefits for sustainable agriculture.