Potassium forms and quantity–intensity relationships in some wetland soils of Abeokuta, Southwestern Nigeria

Abstract

The study was carried out to assess forms of potassium (K) and K quantity–intensity relationships in six wetland soils in Abeokuta, Southwest Nigeria. Collected soil samples from pedogenic horizons of six profile pits were analyzed using appropriate techniques. The soils were loamy sand – sandy clay with very low to moderate (0.04–2.55%) organic carbon, low–medium (4.29–22.29 cmol kg⁻¹) effective cation exchange capacity, high base saturation (89.42–99.56%), and low available phosphorus (≤1.90 mg kg⁻¹). Values of exchangeable-K (0.05–0.20 cmol kg⁻¹), mobile-K (0.26–1.53 cmol kg⁻¹), reserved-K (0.51–2.56 cmol kg⁻¹), residual-K (0.42–2.21 cmol kg⁻¹), and total-K (1.02–3.32 cmol kg⁻¹) were low. The buffering capacity of the soils for K (88.10–273.2 cmol kg⁻¹(mol.L⁻¹)^½) and labile-K at specific site (4.48–16.43 cmol kg⁻¹) were moderate and the free energy of replacement (5512.17–8414.94 J mol⁻¹) was low. The results suggest that the soils have low capacity to fix K and could, therefore, release applied K fertilizer appropriately for crop uptake. The low-K status of the soil can be corrected by application of K fertilizers.

Keywords:

• wetland soils
• forms of potassium
• buffering capacity
• labile potassium
• free energy of replacement