SPATIAL ANALYSIS OF INFILTRATION AND HYDRAULIC CONDUCTIVITY OF AN ALFISOL SOIL IN AKURE

Abstract

The knowledge of soil hydraulic properties and processes leads to better predictions of both agricultural and environment impact. Soil hydraulic properties also define the relationship between soil moisture, hydraulic head and hydraulic conductivity, thus controlling how water moves through the soil. This research concentrated on hydraulic conductivity as a function of soil water content and soil water sorptivity and its main objective was to analyse spatial variability soil hydraulic properties of 100 m × 60 m Alfisol in the Research and Training Farm of the Federal University of Technology, Akure, South Western Nigeria. Mini disc infiltrometer experiments were conducted at a suction rate of 2 cm per second at different points on the field. Soil samples were analyzed to determine soil bulk density, total porosity and water holding capacity. The coefficients of variation of the textural classes indicate a non considerable variability of the sand, silt and clay contents. From the statistical and spatial analysis for the different parameters, it was found that the soil hydraulic parameters had larger variability than bulk density, total porosity and water holding capacity. Hydraulic conductivity, cumulative infiltration, soil water Sorptivity, and other soil properties had larger variability at the upper soil layer (0 – 100 mm) than in the middle (100 – 200 mm) and lower (200 – 300 mm) soil layers. The spatial variation and three dimensional plots of the soil hydraulic properties confirmed that the peak values were not concentrated to any part of the field and the variation seems to be arbitrary in the soil layers. Increasing bulk density lowers the soil pores and in consequence reduced the soil hydraulic properties of the experimental plot. Hydraulic conductivity was more pronounced in soils with higher organic matter content. Values for hydraulic conductivity, soil water sorptivity and cumulative infiltration were significantly different among the soil layers.