Effect of Selected Chicken Manure-Charged Biochar on Growth of Ralstonia Solanacearum in Vitro

A study was conducted in vitro to assess the antibacterial effect of specific chicken manure-charged biochar extracts against Ralstonia solanacearum at the microbiology laboratory of Egerton University. The study tested charged biochar extracts from various feed stocks: maize cobs (MC), maize straw (MS), rice husks (RH), bean wastes (BW), and eucalyptus branches (EU). The extracts consisted of plain biochar and charged biochar with poultry manure. The physico-chemical properties of biochar were assessed according to established standard procedures. The antibacterial efficacy of charged biochar extract was evaluated by mixing nutrient agar (NA) in petri dishes with 0.5 ml of the extracts prior to solidification, followed by the spread of 0.1 ml of bacterial suspension on each plate. Sterile distilled water served as a negative control, while copper oxychloride was utilized as a positive control. The plates were incubated at 28°C for 48 hours in growth chamber. The experiment was arranged in a completely randomized design (CRD) with three replicates. Charged biochar exhibited higher nitrogen content than that of plain, with bean waste charged biochar having the highest at 1.5% and plain eucalyptus biochar lowest at 0.4%. For available phosphorus, maize cob charged biochar exhibited the highest with 1846 mg/kg while the lowest was plain rice husk biochar at 671.5 mg/kg. Organic carbon at 74.2% for maize cob charged biochar was the highest and EUPB exhibited the lowest 23.5%. Porosity was high in plain biochar as compared to charged, while charged biochar exhibited higher density than plain with the lowest 0.6 for MCPB and highest 1.0 for rice husk plain biochar. The antibacterial assay indicated that all biochar extracts significantly suppressed the growth of R. solanacearum compared to the negative control. Charged eucalyptus biochar reduced pathogen growth by 100% which was the highest inhibition while plain maize straw was lowest at 1.19%. These results proved that charging biochar, especially that derived from bean wastes and eucalyptus, with chicken manure not only increases the nutrient content but as well enhances its potential of controlling bacterial wilt.