Document Type: Regular Paper
Department of Geography, Environmental Science and Planning, University of Swaziland, Private Bag 4 Kwaluseni M201, Swaziland
Directorate of Research Development, Walter Sisulu University, Nelson Mandela Drive, P/Bag XI Unitra 5117, Eastern Cape, South Africa
Soil productivity is generally associated with poor nutrient status and the physical condition of the soil, but the effect of soil mineralogy on soil productivity has received little attention. In this qualitative study, interactions between mineralogy and physico-chemistry and their role on the productivity of two luvisols, an arenosol and a vertisol are investigated. Minerals identified in the soils included smectites in the vertisol, kaolinite, quartz, hydromica, albite and biotite in the luvisols and arenosol. The presence of smectite in the vertisol has resulted in it having a higher organic matter content, higher cation exchange capacity, higher water holding capacity, and low bulk density than both luvisols and the arenosol. Both luvisols and the arenosol were dominated by quartz, feldspars and kaolinite, which are chemically inert compared to smectite and have fewer effects on soil cation exchange capacity, water holding capacity, and bulk density. The effect of soil mineralogy and physico-chemistry on the productivity of these soils is reflected in the yield of spinach (Spinacia oleracea variety Fordhook giant) grown on the different soils where spinach yield on the vertisol was the highest followed by that of the luvisols and then the arenosol.