Abstract:
Soil hydraulic and hydraulic-related physical properties are key to soil productivity and
these properties are widely studied. Nevertheless, their spatial variability is least
understood. Two sites were selected for this study (University of Venda Experimental
farm and Roodeplaat, Agricultural Research Council farm). The objectives of this study
were to determine the spatial variability of soil water content, water infiltration and
hydraulic conductivity on selected soils. Field measurements were done on a 20 m ×
20 m. Soil hydraulic and hydraulic-related physical properties were studied at two
depths, 0 – 0.2 m top soil and 0.2 – 0.4 m sub soil. The field was irrigated to saturation
and let to drain freely for two days. The soil was quickly secured in water cans to avoid
further loss of water by evaporation and taken to the laboratory for analysis. Data was
analysed using ordinary kriging method in ArcMap® software version 10.4 to generate
spatial variability maps and semi variograms. The University of Venda Experimental
farm had lesser spatial variability with coefficient of variation ranging from 9.6 to
33.4%. The spatial variability of soil was very low confirmed by contour maps depicting
slightly homogeneity. Whereas, the soil hydro-physical properties displayed greater
spatial variability at Roodeplaat, Agricultural Research Council Experimental farm.
The empirical variograms of spherical model fits were also assuming weak spatial
dependence with a curve variogram. The coefficient of variation ranged from 10.5 to
51.9%. Therefore, the greater variability at Roodeplaat, Agricultural Research Council
Experimental farm indicated that coarse soil texture under conventional tillage has a
greater influence on the spatial variability of the soil hydro-physical properties.
