Inoculation of fly ash amended vermicompost with phosphate solubilizing bacteria (Pseudomonas fluorescens) and its influence on vermi-degradation, nutrient release and biological activity

Due to the crucial role played by microbes during vermicomposting, deliberate inoculation of composts with specialized microbes as a way of further optimizing the vermicomposting process has been suggested. This study evaluated the potential of inoculating fly ash – cow dung – waste paper vermicompost with phosphate solubilizing bacteria (P. fluorescens) in improving vermi-degradation, nutrient mineralization and biological activity. Incorporation of E. fetida plus P. fluorescens accelerated the biodegradation process as indicated by the significant decrease in C/N ratio (P = 0.0012) resulting in a final C/N ratio of 11 compared to the control which had C/N ratio of 18. Inoculation with P. fluorescens resulted in improved availability of Olsen P which amounted to 48.3% more Olsen P relative to the control. The inoculation also caused a big decrease in alkaline phosphatase activity but yielded the highest FDA activity. Inclusion of E. fetida with or without P. fluorescens did not significantly influence microbial growth, however, these two treatments had relatively more colony counts compared to the control. It is concluded that the interaction of E. fetida earthworms with P. fluorescens can optimize vermi-degradation, nutrient release and biological activity during vermicomposting of fly ash- cow dung – waste paper substrate. It would be interesting to establish whether Pseudomonas species inoculated at different rates, or their combination with nitrogen fixing bacteria would have the same or better effects on the vermicomposting of fly ash- cow dung – waste paper substrates.