Spatial analysis of soil hydraulic properties of an alfisol in Akure, Southwestern Nigeria

Abstract

The knowledge of soil hydraulic properties and processes leads to better predictions of both agricultural and environment impact. The objectives of this research are to determine, predict and compare the relationship between measured and estimated soil hydraulic properties and also spatially characterize these properties using geostatistics. Mini disc infiltrometer at a suction rate of 2 cm per second was used for the determination of soil hydraulic properties at different points of an alfisol in Nigeria. Soil samples (100, 200 and 300 mm depths) were also analyzed to determine soil bulk density (BD), total porosity (PT) and water holding capacity (WHC). The coefficients of variation (CV) of the textural classes indicate a non-considerable variability of the sand (CV=6%), silt (CV=20%) and clay (CV=3%) contents. From the statistical and spatial analysis for the different parameters, the variability of hydraulic conductivity (48%>33%>31%), cumulative infiltration (40%>26%>23%), soil water sorptivity (19%>11%>8%), followed the trend upper soil layer (0–100 mm) > middle (100–200 mm) > lower (200–300 mm) soil layers. Hydraulic conductivity and infiltration were more pronounced in soils with higher organic matter content (OMC) and PT. Pedotransfer models (PTF) for prediction of hydraulic conductivity (K), soil water sorptivity (Sw) and cumulative infiltration (I) from basic soil properties such as OMC, PT were developed and validated using multiple-linear regression method. K, Sw and I predicted by the PTF models were significant for the upper and middle soil layers respectively (r = 0.812 and 0.670; 0.825 and 0.670, and 0.820 and 0.670). Contour and wireframe representation were used to spatially analyze the soil hydraulic properties across the field. These contour and 3D surface plots are useful for establishing farm operating conditions, especially in water, fertilizers or pesticides management.