Assessment of compost maturity using germination index in biochar amended caged layer manure compost

Abstract:

The present study was conducted to evaluate the effect of biochar incorporation and passive aeration techniques on the maturity of compost prepared from caged layer manure (CLM) using germination index (GI) as a biological indicator. Composting experiments were carried out at the Livestock Farm Complex, Veterinary College and Research Institute, Namakkal, Tamil Nadu, India during summer and monsoon seasons. Nine treatments comprising different combinations of caged layer manure, biochar and coconut coir pith (CCP) waste under passive aeration and static composting systems were evaluated. The C:N ratio (20:1) and moisture content (50–60%) were maintained uniformly in all treatments. Compost maturity was assessed through seed germination and root elongation tests using cowpea and sorghum seeds. The germination index values ranged from 85.40 to 152.88 per cent during summer and 81.63 to 133.72 per cent during monsoon season. Among the treatments, compost amended with 50 per cent biochar and 50 per cent coconut coir pith waste under passive aeration with a V-shaped pipe system (T₅) recorded the highest pooled germination index value (137.32 ± 13.86%), whereas the static composting control without carbonaceous amendment (T₉) recorded the lowest value (83.30 ± 4.56%). The germination index values obtained in all treatments were above the minimum maturity threshold of 70 per cent, indicating satisfactory compost maturity. Biochar-amended treatments exhibited significantly higher germination index values than the control groups, suggesting enhanced degradation of phytotoxic compounds and improved compost quality. The study concluded that incorporation of biochar, particularly under passive aeration with a V-shaped pipe system, improved compost maturity and produced superior quality compost suitable for agricultural application.