Impacts of Land Use and Soil Depth on Phosphorus forms in Soils of Basement Complex Geology, Ogun State, Nigeria

Abstract

Soils derived from basement complex geology were investigated to assess the impact of land use and different depths on phosphorus forms. Two locations were selected across the basement complex geology and consequent upon the land use types (cultivated arable crop and fallowed arable crop land) in each of the locations, two profile pits were dug. Results showed that the soils were similar in texture (loamy sand surface horizons overlying sandy clay loam subsurface horizons), while soil pH (5.95-7.15), Ca (2.5-5.8 cmol/kg), Mg (1.0-15.5 cmol/kg), total exchangeable acidity (TEA) (0.1-1.5) and OC (0.4-10 g/kg) varied across the geological formation. The abundance of the P forms followed the pattern: Iron-P (33.73 mg/kg) > Labile-P
(32.76 mg/kg)> Aluminum-P (17.98 mg/kg)>Water soluble-P (15.38 mg/kg)>Ca-P (4.49 mg/kg), indicating that the distribution of the P forms in the geology had Fe-P as the most abundant P-forms and Ca-P as the least abundance. There was negative and significant relationship between the Al-P and Avail-P, Ca, Mg, k, pH and Ca-P in all the land uses and soil depths, indicated that an increase in the Al-P will lead to decrease in the Avail-P and Ca-P in the soils. Since the relationship among the element was the same across the land uses and the soil depth, it was concluded that land use and soil depth had no significant influence on the forms of phosphorus of the basement complex geology.