Phosphorus Sorption in Soils Overlying Basement Complex Rock, Alluvium, Coastal Plain Sand and Imo Shale Parent Materials

This study aimed at evaluating phosphorus (P) sorption capacities in Soils overlying basement complex Rock (A), Alluvium (B), coastal plain sand (C) and Imo shale (C) parent materials.

Completely randomized design was used to collect soil samples from 5 depths in 3 replications from Idanre, Koko, NIFOR and Uhomora in Nigeria.

Samples collected were analyzed in the central analytical laboratory of the Nigerian Institute for Oil palm Research, Benin City, Nigeria between march 2016 and September 2017.

60 soil samples were equilibrated in 25 ml of 0.01 M CaCl2 containing various concentration of P as KH2PO4 to give 0, 50, 100, 150, 200 and 250 mg/L P for 24 hours (h) at room temperature 25 ± 2 oC. Genstat statistical package was used to calculate Analysis of variance, correlation of Phosphorus sorption index (PSI) with soil properties, coefficient of variation, means separation and Least Significant difference (LSD).

The rate and %P adsorption increased with increasing concentration of P added to the soils. The P sorption capacities of the soils considering Freundlich model decreased in the order of D > B > C >A. %P adsorbed was highest in D soils with value of 15.19% for 100 mg/kg P added. The PSI correlated with organic carbon r = -0.58 P ≤ .05 in C soils, r = 0.44 P ≤ .05 in D soils, it also correlated with N r = -0.58 P ≤ .05 in C Soils, K r = 0.57 P ≤ .05, r = 0.49 P ≤ .05 in C and D soils respectively.

D soils sorbed more P than other soils hence the D soils will require more P fertilization to attain optimum P concentration in soil solution, however further study is required to determine the form of P sorbed by these parent materials.