Abstract: Most of the agricultural lands in the tropics are highly weathered and depleted of plant nutrients, particularly phosphorus resulting in a decline in crop production. Phosphate rock can be used to correct the phosphorus levels but its effectiveness is generally low compared to water-soluble phosphate fertilisers such as single superphosphate or triple super phosphate due to its low solubility in soils. Incubation and glasshouse studies have shown that physically mixing phosphate rock and water-soluble phosphate fertiliser can significantly improve its solubility and has been attributed to phosphoric acid produced from the hydrolysis reaction in the soil of monocalcium phosphate in superphosphate dissolving the phosphate rock. However, the phosphoric acid could also be dissolving iron and manganese minerals in soil which subsequently lowers the dissolved phosphorus levels from phosphate rock by precipitation reactions, thus the need to carry out further experiments in other systems like water to investigate as to whether the increased phosphorus levels in the mixtures is due to dissolution of phosphate rock by phosphoric acid or increased phosphorus levels from increased amounts of superphosphate. Effect of combinations of a commercially available water-soluble phosphate fertiliser (single superphosphate) and gafsa phosphate rock material in the ratios of gafsa phosphate rock to superphosphate of 1:1, 1:4, and 4:1 in 25 mL and 100 mL deionized water were set up. The findings of this study were that superphosphate was found to be responsible for the increase in the extractable phosphorus concentrations. This was due to the fact that there was enhanced dissolution of gafsa phosphate rock in the mixture from the hydrolysis reaction of monocalcium phosphate by phosphoric acid and with the pH values increasing as both the extractable calcium and phosphorus decreased an indication that both metal solutions affected the dissolution through the formation of metal precipitates.
Keywords: Superphosphate, Gafsa Phosphate Rock, Dissolution, water.
Title: Effect of Combinations of Phosphate Rock and Superphosphate on Dissolution of Phosphate Rock in Water
Author: J.O. Owiti, C.K Chepkwony, T.K. Kinyanjui
International Journal of Life Sciences Research
ISSN 2348-3148 (online), ISSN2348-313X (Print)
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