ABSTRACT
This study investigates the effects of anaerobic composting on soil properties, including key metrics such as electrical conductivity, organic matter, and the carbon-to-nitrogen (C/N) ratio. The composting procedure used a combination of cow horns, corn cobs, palm oil sludge, and fruit debris collected from several places in Benin City, Nigeria. The study's goal was to determine the impact of these components on soil quality through anaerobic composting. A comprehensive analysis of compost samples A2 and A4 revealed detailed insights into their physicochemical properties and prospective agricultural applications. Compost A2, made up of fruit waste, corn cob, cow horn, and palm oil sludge, has a slightly acidic pH (7.25 ± 0.54) that promotes nutrient availability and microbial activity in different soil types. Compost A4, made entirely of fruit waste, has an alkaline pH (9.38 ± 0.32), indicating limitations in acidic soils but potential benefits in alkaline soil settings. The electrical conductivity and moisture content of the composts differed, indicating variable salt concentrations and moisture retention capabilities that could have an impact on soil salinity and microbial activity. Compost A2 had moderate conductivity (1391.10 ± 15.2 uS/cm), while compost A4 had slightly higher values (1439.4 ± 38.00 uS/cm), indicating different salt content levels and the need for different management measures to minimize soil salinity. A2 composts had significantly higher ash content (7.14 ± 0.4%) than A4 composts (1.02 ± 0.32%). This difference indicates varied mineral concentrations and inorganic residues, which are most likely impacted by compost ingredients and breakdown processes. The carbon-to-nitrogen (C/N) ratio, which measures the balance of carbon-rich organic components and nitrogen-containing molecules, revealed the composts' varying breakdown stages and stability levels. A4 composts had higher C/N ratios (738.21 ± 246.92) than A2 composts 3 (344.26 ± 39.76), indicating advanced decomposition and increased stability. Sodium levels, which are important for soil structure and plant growth, also varied amongst compost kinds. Compost A2 had higher salt content (309.8 ± 3.2 mg/kg) than A4 composts (229.5 ± 4.5 mg/kg), possibly due to sodium-containing components such palm oil sludge in A2. Furthermore, pot trials revealed significant increases in total organic carbon and organic matter levels in compost-amended soil pots, demonstrating the beneficial effects of compost supplementation on soil fertility. The observed decrease in the carbon-to-nitrogen ratio over time indicated increased nitrogen availability, which is critical for maintaining plant nutrient absorption and soil health. Fluctuations in soil sodium and electrical conductivity, together with elevated electrical conductivity levels indicating enhanced soil nutrient levels, supported the beneficial effects of compost supplementation on soil nutrient availability. Keywords: Anaerobic composting, soil properties, compost characterization, electrical conductivity, organic matter, total organic carbon, carbon-to-nitrogen ratio, sodium content, agricultural applicability, soil fertility, nutrient availability, sustainable soil management.
