Carbon-to-nitrogen optimization for vermicomposting broiler poultry litter

The potential benefits of bioconversion of commercial broiler poultry litter (PL) to vermicompost (with Eudrilus eugeniae ) were studied by optimizing the carbon-nitrogen ratio (C/N) using coconut ( Cocos nucifera ) coir pith (CP) and farmyard manure (FM) as co-substrate. In this experiment, after optimizing the carbon to nitrogen ratio (C/N) at the levels of 25, 30, and 35, the pre-composting of PL followed by vermicomposting was done, and PL and FM alone were used as the control group. After pre-composting, the earthworms ( Eudrilus eugeniae ) were introduced, and the vermicomposting process was continued for 90 days, and the samples were analysed on days 45 and 90 of vermicomposting. The study revealed a significantly ( P < 0.01 ) higher Feedstock Vermicompost Conversion Ratio (FVCR) of 54.1 ± 0.9 in FM treatment group. This was followed by Broiler poultry litter + coir pith + FM at C/N 35 (PLCPFM35: 47.5 ± 0.6), Broiler poultry litter + coir pith + FM at C/N 30 (PLCPFM30: 45.3 ± 0.4), Broiler poultry litter + coir pith at C/N 35 (PLCP35: 45.1 ± 1.2) and Broiler poultry litter + coir pith at C/N 30 (PLCP30: 41.8 ± 0.6). An increase in total Ca (g kg −1 ) was recorded during 90th day sampling and ranged between 27.0 ± 5.4 and 21.6 ± 2.6 g kg −1 in treatment groups, where earthworm activity was high. The total K level (g kg −1 ) at the end of 90th day ranged between 12.1 ± 0.1 and 21.6 ± 0.4 with increasing trend. PL vermicompost exhibited favourable physicochemical features, including significant ( P < 0.01 ) nitrogen mineralization and the absence of phytotoxic compounds. The experiment revealed that commercial PL either in its raw form or at a C/N of 25, was unsuitable for vermicomposting, but vermicompostability improved after optimizing the C/N to 30 and 35 respectively. These findings indicate that Eudrilus eugeniae (African nightcrawler) can effectively maximize the bioconversion of PL into high-quality vermicompost, provided the substrate materials are carefully balanced.