Physical and Chemical Quality Testing of Compost from Solid Waste Formulations of Oil Palm Plants (Elaeis guineensis Jacq.) Based on Analysis of Variance and National Quality Standards

This study aimed to evaluate the physical and chemical quality of compost derived from six solid waste formulations of oil palm (Elaeis guineensis Jacq.) and to identify the best formulation according to Indonesian Ministry of Agriculture Regulation No. 70/Permentan/SR.140/10/2011 and National Standard SNI 7763:2018. The research was conducted from May to June 2024 in Sei Beringin Village, Indragiri Hilir Regency, Riau Province, Indonesia. Six formulations (K1–K6) were prepared with varying proportions of decanter solid, boiler ash, biochar, oil palm fronds, and chicken manure, using Effective Microorganism-4 (EM-4) as a bio-activator, composted for 35 days. Physical parameters (temperature, Munsell colour, odour, texture, and weekly pH) and chemical parameters (total N, P₂O₅, K₂O, organic C, C/N ratio, pH, moisture content) were analysed using SNI 7763:2018 methods. To support scientific comparison between formulations, one-way Analysis of Variance (ANOVA) was applied based on three analytical technical replicates per formulation (laboratory CV 1–4%), followed by Tukey–Kramer HSD multiple comparison tests (α = 0.05). All formulations met physical maturity criteria. Chemically, ANOVA revealed highly significant effects of formulation (p < 0.001) on total N (F = 35.82; η² = 0.937), P₂O₅ (F = 78.55; η² = 0.970), K₂O (F = 105.08; η² = 0.978), aggregate N+P+K (F = 58.65; η² = 0.961), C/N ratio (F = 45.72; η² = 0.950), and pH (F = 17.49; η² = 0.879); organic C was not significantly different (F = 1.29; p = 0.331). Formulation K5 (30% chicken manure) exhibited significantly the highest N+P+K (7.75%) and the most favourable C/N ratio (21.1). Moisture content across all formulations (58.8–63.2%) exceeded the SNI maximum of 25% and requires post-composting drying.