SPATIAL VARIABILITY OF HYDRAULIC CONDUCTIVITY AND SOIL WATER REPELLENCY IN AN ALFISOL IN AKURE

Abstract

Spatial variability of hydraulic conductivity and water repellency in an alfisol was investigated using a field based measurement. A mini-disk infiltrometer was used to measure the infiltration rate of water and ethanol into the soil at 40 points evenly distributed in four major farm locations (A-D) in the Federal University of Technology, Akure (FUTA). Soil physical and chemical properties were also measured. Spatial distribution and variability of hydraulic conductivity and water repellency were also examined using geo statistical techniques like kridging, contour maps and semi-variograms. Results showed that hydraulic conductivity exhibited a strong linear negative relationship with repellency index, correlation coefficient (𝑅= 0.8844 ) which means as water repellency increased hydraulic conductivity of the alfisol decreased. Descriptive analysis showed that location B had the highest mean of hydraulic conductivity (K = 4.86 x 10-4 cms-1) and the lowest mean water repellency (R = 1.03). Relationship between some selected soil physical and chemical properties, hydraulic conductivity and water repellency were examined using simple linear regression method and their relationships varied from weak to strong linear positive relationships. The coefficient of variation (CV) of hydraulic conductivity is maximum at location A with a value of 46% and lowest at location C with a value of 23%. Locations A and B had a slightly skewed distribution with skewness values 0.48 and 0.37 respectively while locations C and D had negative skewness values (−0.72 and −0.81) respectively. Repellency index for Location B had the highest coefficient of variation with a value of 72% while locations A, C and D have coefficient of variation values 50%, 38% and 13% respectively. The distribution of the whole repellency index is just slightly negatively skewed with a skewness value −0.19 and kurtosis value of 0.26. An average positive correlation with sand percentage 𝑅=0.764) and a strong negative correlation with water holding capacity (𝑅=0.875) at P = 0.05. Hydraulic conductivity showed a positive correlation with total porosity (𝑅=0.581) and soil organic carbon (𝑅=0.846).Repellency index showed a negative relationship with sand percentage (𝑅=0.648) and a strong positive relationship with water holding capacity(𝑅=0.849). It also showed a significant positive relationship with soil organic matter (𝑅=0.589) and strong negative relationship with soil organic carbon(𝑅=0.684). This research facilitates a better understanding of the soil hydraulic properties behavior and water management at the Federal University of Technology, Akure experimental farms and also useful to soil scientists, mode of irrigation systems and land managers in the study areas.