Effect of Phosphate Rock Addition on Soil Organic Matter

The fertilizer treatments consisted of four rates of Ogun phosphate rock (0, 30, 60 and 90 kg P ha-1 ) and triple super-phosphate at 40 kg P ha-1. Legume treatment consisted of Mucuna and cowpea and was planted as a pre-rice crop. Soil samples were collected and analyzed for organic carbon. Four pellets of Ogun phosphorites labelled OG1, OG2, OG3 and OG4 were randomly selected and subjected to X-ray fluorescence analysis, the mixture of different pellets used for the experiment was also analysed. Loss on ignition from the different pellets and the mixture was recorded. The organic carbon content of the raw phosphate rock was determined too. Results showed the Loss on ignition which represent a combination of moisture and CO2 varied from 11.67 – 16.27%organic carbon content of Ogun phosphate rock (0.31%) was higher than other phosphate rock materials, Sokoto (0.12%) and Togo (0.12%). There was a significant increase in organic carbon as a result of Ogun phosphate rock addition (p< 0.05) in the greenhouse with soil samples from Ibadan but no significant effect was observed with samples from the other two sites, but a gradual increase was noticed. Increases of 8.2%, 12.5% and 14.8% in organic carbon were recorded for OPR applied at 30, 60 and 90 kg ha-1 respectively over control pot for soil sample from Abeokuta without incorporation of legume.