Influence of Microbial Inoculation of Igneous Rock Phosphate-Amended Cow and Pig Manures on Vermidegradation and Nutrient Release

Abstract

Vermicomposting using Eisenia fetida has been shown to improve phosphorus mineralization from rock phosphate (RP). There is, however, a lack of information on the potential of integrating microbial inoculants like phosphate-solubilizing bacteria (PSB) during vermicomposting as a way of improving vermidegradation, and the release of nutrients from igneous RP-amended composts. This study evaluated the potential of using Eisenia fetida and Pseudomonas fluorescence in enhancing the vermidegradation, and nutrient release in igneous RP- amended cow and pig manure-based vermicomposts at a C/N ratio of 30. Compost maturity, nutrient and phytotoxicity parameters were measured to determine vermicompost quality. Final vermicompost results showed that the pig manure treatments achieved greater maturity as indicated by lower C/N of 10.3, high humification index (HI) of 7.6%, and humification ratio (HR) of 12.89% in the treatment with E. fetida and P. fluorescence. The inclusion of E. fetida alone in cow manure treatment resulted in the highest Olsen P of 2600 mg/kg, followed by the pig manure treatment with E. fetida only (2246.15 mg/kg). In conclusion, both E. fetida and P. fluorescence are necessary in the vermicomposting of RP-enriched pig and cow manure for efficient vermi-degradation and nutrient release.