Phosphorus adsorption characteristics of selected southeastern nigerian soils

Abstract

The phosphorus adsorption characteristics of selected Southeastern Nigerian soils from Ikom, Bende and Ihiagwa were evaluated. P adsorption isotherm was obtained by shaking soil samples with 0, 10, 20, 30, 40 and 50 ppm P in 0.01M CaCl2 solution. P adsorption maxima (b), affinity constant (k), buffering capacity and P sorbed at 0.2 ppm equilibrium solution were estimated. Also adsorbed P was correlated with some soil properties. The adsorption isotherm showed that the capacity to adsorb phosphorus varied in the order; Ikom> Ihiagwa> Bende. The values for the P sorbed at 0.2 ppm solution, buffering capacity, adsorption maxima and affinity constant were 43.28, 43.30, 34.48 and 12.95 ug/g respectively for Ikom, 3.86, 7.78, 29.50 and 0.21 ug/g respectively for Bende and 8.48, 10.00, 33.11 and 0.57 ug/g respectively for Ihiagwa soils. The capacities to adsorb P was significantly and positively correlated with soil clay (r = 0.94), exchangeable aluminum (r = 0.72), soil pH (r = 0.83), whereas the correlation with exchangeable calcium (r = -0.56) and organic carbon (r = -0.72) were significantly negative. The implications are that the higher the soil pH, clay level, exchangeable aluminum, adsorption maxima and affinity constants the higher the soil adsorption capacities whereas the reverse will occur the higher the soil organic carbon and calcium levels. The study shows that Ikom soil will require higher P fertilization rates than the other two soils for optimum plant growth. Also management practices involving the use of organic matter and liming as basis for P adsorption reduction would be useful for improved crop production in these soils. The use of P adsorption isotherm as a valid tool for P fertilizer management is recommended for Southeastern Nigerian soils.

Agro-Science Vol. 4 (1) 2005: pp. 50-55