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.
Highlights
The major challenge associated with world population growth has been the generation of huge quantities of solid waste
The higher earthworm biomass observed in pig manure compared to cow manure-waste paper rock phosphate (RP)-enriched vermicompost could be due to differences in the availability of nutrients in the mixture [30]
Pig manure treatments maintained higher levels of NH4 -N and Olsen extractable P than cow manure-based treatments (Table 1) and possibly other nutrients that were not analysed. This implies that higher nutrients concentrations in pig manure could have explained at least partially the much higher earthworm biomass treatments observed in pig manure treatments than in cow manure-based treatments, as the pH, Electrical Conductivity (EC), nitrates and ammonium in the pig manure showed favourable conditions for the growth of earthworms (Table 1)
Summary
The major challenge associated with world population growth has been the generation of huge quantities of solid waste. The global production of solid waste is estimated to be 1.3 billion tons per year and expected to double by 2025, with the organic wastes fraction ranking the highest among the solid waste generated [1]. Recycling of nutrients from solid waste through composting and vermicomposting have been studied to reduce the inappropriate disposals of these organic wastes in agricultural lands [2,3]. There has been a growing realization of the importance of organic nutrient sources in improving overall soil quality. Vermicomposting is one technology that has gained momentum in recent years as having the potential for converting both organic and inorganic waste materials into nutrient-rich fertilizer sources [4,5]
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