Comparative evaluation of humic substance production from organic wastes in tropical vermicomposting using Eisenia foetida

Abstract

The valorization of organic waste through vermicomposting has emerged as a sustainable strategy for producing humic substances, which are critical for improving soil fertility and reducing dependence on chemical fertilizers. This study compared the efficiency of humic and fulvic acid production from six organic wastes: bovine, equine, ovine, and rabbit manure, vegetable waste, and a 50:50 mixture of bovine and equine manure using Eisenia foetida under tropical conditions. All substrates underwent aerobic pre-composting (16–28 days), followed by 30 days of vermicomposting. Key parameters influencing humification included substrate porosity, aeration, and carbon/nitrogen ratios ranging from 12:1 to 50:1. Statistical analysis showed significant differences among treatments (p < 0.05). The bovine-equine mixture yielded the highest humic acid concentration (24 %), followed by equine (21.8 %) and rabbit manure (18.9 %). Ovine manure produced the highest fulvic acid content (3.3 %), while bovine and vegetable waste had the lowest yields. These findings demonstrate that substrate blending enhances microbial activity and humification efficiency. Vermicomposting provides an effective and low-cost solution to convert organic waste into humic-rich biofertilizers, supporting circular agriculture and sustainable soil management.