| Phosphorus deficiencies are limiting crop production in agricultural soils worldwide. Locally available sources of phosphate rock (PR) are being recognized for their potential role in soil fertility improvement. For applications of PR to be effective, the phosphorus must be made plant-available. Modification with acid-producing microorganisms has the potential to increase the agronomic effectivenss of PR. For this thesis, four strains of Aspergillus niger were screened for phosphate solubilization and acid production. Response surface methodology was used to optimize medium conditions for citric acid production. Lastly, PR solubilization from additions of PR to an A. niger ATCC 9142 culture medium at cultivation onset, was compared with additions of PR to the acid-containing culture supernatant. The two treatments were found to solubilize equivalent PR, with solution P values ranging from 219-382 mg/l. Future research is necessary to optimize this process and to investigate the effects of such phosphorus mobilization on plant growth. |
