OICC Press International Journal of Recycling of Organic Waste in Agriculture 2251-7715 2026 08 05 Effects of Organic Feedstock Type on Nutrient Transformation and Chemical Characteristics of Vermicompost Produced by Eudrilus eugeniae 10.57647/ijrowa.2026.1504.32 EN Suttayot Yimpoolsap https://orcid.org/0009-0003-6960-4427 Journal Article 2026 08 05 Purpose: This study evaluated how four agricultural residues coconut coir (CC), leaf litter (LL), water hyacinth (WH), and corn cob (CCOB) mixed with dairy manure influence nutrient transformation and maturity of vermicompost produced by Eudrilus eugeniae. The practical aim was to identify which feedstock yields the most stable and nutrient-rich vermicompost for tropical agricultural use. Method: A completely randomized design (CRD) with four feedstock treatments and three replicates was used. Each mixture was precomposted for 21 days before vermicomposting for 44 days. Key parameters (pH, EC, OM, NH₄⁺, NO₃⁻, PO₄³⁻) were analyzed, and nutrient-transformation ratios (NH₄⁺/NO₃⁻, NO₃⁻/PO₄³⁻) were calculated. One-way ANOVA, ANCOVA, and repeated-measures ANOVA assessed treatment effects, while PCA identified dominant nutrient-association patterns. Results: Precompost properties varied significantly across feedstocks, particularly for nitrogen fractions. Although most values satisfied the Thai organic fertilizer standard (pH 5.5 - 8.5; EC < 10 dS/m; OM ≥ 20%), elevated NH₄⁺/NO₃⁻ ratios indicated incomplete stabilization prior to vermicomposting. After 44 days, EC and NH₄⁺ declined markedly, whereas NO₃⁻ and PO₄³⁻ increased, reflecting enhanced mineralization and nitrification processes as inferred from observed chemical transformation patterns during vermicomposting. ANCOVA demonstrated that feedstock chemistry exerted a stronger influence on nutrient dynamics than initial precompost values, especially for EC and NH₄⁺. PCA revealed contrasting nutrient pathways: WH and CCOB exhibited stronger mineralization intensity, whereas LL and CC maintained greater organic stability. All vermicomposts reached NH₄⁺/NO₃⁻ < 1, indicating chemical maturity suitable for agricultural application. CC produced the most stable nitrate-rich vermicompost, suggesting its suitability as an optimal feedstock. Conclusion: Vermicomposting dairy manure with locally available residues generated nutrient-enriched composts that met national quality standards. Feedstock type strongly governed nitrogen and phosphorus transformation pathways, offering a practical basis for selecting substrates in tropical vermicompost production. Highlights • Organic feedstock type significantly influenced nutrient transformation during vermicomposting.• Vermicomposting improved nitrogen availability and reduced the C/N ratio of organic materials.• Eudrilus eugeniae effectively converted agricultural organic wastes into nutrient-rich vermicompost.• Different feedstocks produced distinct chemical characteristics in the final vermicompost.• Vermicomposting enhanced the fertilizer potential of organic waste materials.