Effect of Eisenia fetida on Nutrient Composition of Vermicompost Produced from Barberry Waste

Abstract

This study tested vermicomposting of seedless barberry (Berberis vulgaris var. Asperma) pruning residues to create nutrient-rich organic fertilizer and reduce chemical fertilizer dependence. Barberry, widely grown in South Khorasan, Iran, produces about 36 ton of unused biomass annually. In this study, a comparison was carried out on three raw materials: barberry leaves, a 1:1 mixture of leaves and branches, and branches inoculated with Eisenia fetida earthworms. Inoculation used 0.5 kg packages with 20 gr of earthworms in aerated containers (23°C and 60-70% humidity) for 50 days. Analyses of mature vermicompost measured pH, electrical conductivity, organic carbon, and macro- and micronutrients (N, P, K, Ca, S, Fe, Zn, Mn, Na, B, Cl). ANOVA and LSD tests showed substrate strongly influenced nutrient enrichment. Pure leaves produced the highest nutrient levels, with nitrogen reaching 2.76 % (vs. 1.14 % in branch-only compost), potassium 2.99 %, calcium 1.87 %, and sulfur 0.05 %. Phosphorus ranged 1,135–1,645 mg kg⁻¹ across treatments. Micronutrients were also greatest in leaf vermicompost iron 30.7 mg kg⁻¹, zinc 1.91 mg kg⁻¹, sodium 6,600 mg kg⁻¹, and boron 18.9 mg kg⁻¹— while chloride exceeded 10,000 mg kg⁻¹ in all samples. Leaf-branch mixes showed intermediate values; branches alone were lowest. The findings demonstrate that E. fetida accelerates mineralization and boosts nutrient availability, making barberry leaves a superior feedstock for producing high-value vermicompost.