ABSTRACT

The study was carried out to determine the competitive adsorption of sulphate and phosphate ions on two benchmark soils. The work involved field and laboratory studies. For field work, profile pit was dug at each of the two benchmark soils. The locations of the pits were Amakama and Bende. Soil samples were then collected from soil horizons of each of the profile pits. The laboratory studies were in three parts. The first part involved the determination of the physico - chemical parameters of the soils. The resull obtained in this study showed that the mean percentage sand. silt and clay for Amakama soil were 61.24 ± 1.69, 4.26 ± 0.52 and 34. 26 ± 0.52 respectively; the corresponding values in Bende sOil were .2.35 ± 3. 59, 11. 45 ± 1 .87 and 66.20 ± 5. 19 respectively. The mean plI and percentage organic matter for all the soils were 5.28 ± 0.08, 4.91 ± 0.15 and 0.91 ± 0.30, 1.13 ± 0.24 respectively. The second part of the laboratory studies was the determination of various forms of P and S in the soils. The mean values for saloid -P, Al - P. Fe - P, Ca - P, occluded P. occluded Fe - /Al - P, residual - P. organic - P, bray -I P, and lray 11 P were 194.03 ±2.84, 50.86 ± 8.45, 168.48 ± 9.63, 35.30 ± 11.04, 119.57 ± 10.21, 33. 19 ± 4.49, 32.38 ± 3.79, 35.22 ± 5.95, 9.46 ± 1.34 and 16.49 ± 2.33 respectively for Aihakama soils, the corresponding values in Bende soils were 200.99 ± 3.96, 71.35 ± 12.30, 288.20 ± 9.54, 425.99 ± 29.01, 197.53 ± 5.16, 28.50 ± 3. 57, 71.17 ± 8.45. 7.38 ± 1.45 and 12.05 ± 2.34 respectively. Total sulphur, organic sulphur, inorganic sulphur and available sulphur gave the following means for Amakama and Bende soils 373.94 ± 32.69 and 393.20 ± 34.14; 346.34 ± 34.73 and 361.67 ± 33.38; 23.32 ± 7.93 and 32.13 ± 2.32; 243.05 ± 45.36 and 358.87 ± 32.28. The last Prt of the laioratory studies was to determine the ellect olsuiphate on phosphate adsorption and effect of phosphate on sulphate adsorption on the top soils of the two benchmark soils. The presence of sulphate in the equilibrium mixture had depressive effect on the adsorption P by surface soil of Amakama especially at the higher level ol P application. The effect of S and P adsorption on Bende soil was not consistent. The effect of P on S adsorption on the two soils studied was not consistent. For both soils and ions (P043and SO) studied, the relationship between the amount of ions added and amount adsorbed was linear when the adsorption data were fitted into Freundlicl and Lahgmuir models. The Freundlich model could only explain adsorption ol sulphate at Bende location with 0.Oorng/g phosphate addition.