Characterisation of Phosphate Rock Deposits in Sokoto State for Agricultural Use

Phosphate rock deposits in Sokoto State, North West Nigeria, represent a strategic mineral resource with the potential to supply fertiliser feedstock for Nigerian agriculture, reducing dependence on imported phosphate products. This study characterises the mineralogy, geochemistry, and physical properties of phosphate rock samples from the Sokoto phosphate deposit, evaluating their suitability for direct application as agricultural fertiliser or as feedstock for single superphosphate production. Samples were collected from exposed sections of the phosphate horizon in the Dange Formation at three localities, following a systematic channel sampling programme. Total phosphate content expressed as diphosphorus pentoxide, cadmium concentration, and the reactivity index were determined as primary quality parameters. X-ray diffraction identified francolite, calcite, quartz, and clay mineral phases, while scanning electron microscopy characterised grain morphology. Acid digestibility tests using citric acid and formic acid were conducted to evaluate the agronomic effectiveness of direct application. The study evaluates whether the cadmium-to-phosphorus ratio meets European Union and Food and Agriculture Organisation guidelines for safe agricultural use. Beneficiation requirements to upgrade phosphate grades below cut-off are assessed using mineralogical liberation data. Findings are communicated to the Raw Materials Research and Development Council and the Federal Ministry of Agriculture to support domestic fertiliser production policy. Keywords: phosphate rock, fertiliser, Sokoto State, francolite, agronomic effectiveness.