Conversion of cassava wastes for biofertilizer production using phosphate solubilizing fungi

Two fungi characterized as Aspergillus fumigatus and Aspergillus niger, isolated from decaying cassava peels were used to convert cassava wastes by the semi-solid fermentation technique to phosphate biofertilizer. The isolates solubilized Ca3(PO4)2, AlPO4 and FePO4 in liquid Pikovskaya medium, a process that was accompanied by acid production. Medium for the SSF fermentation was composed of 1% raw cassava starch and 3% poultry droppings as nutrients and 96% ground (0.5–1.5 mm) dried cassava peels as carrier material. During the 14 days fermentation, both test organisms increased in biomass in this medium as indicated by increases in phosphatase activity and drop in pH. Ground cassava peels satisfied many properties required of carrier material particularly in respect of the organisms under study. Biofertilizer produced using A. niger significantly (p < .05) improved the growth of pigeon pea [Cajanus cajan (L.) Millsp.] in pot experiments but product made with A. fumigatus did not.