An Integrative Hydrogeophysical-Hydropedological Studies of the Hydrologic Impact of Agricultural Management Practices

We integrate a van Genuchten water retention function for clay soils into the analysis of electrical resistivity and soil core-sampling data to assess possible changes in vadose zone properties induced by agricultural management practices in a Texas Vertisol. The field data were collected at two sites that were established at the US Department of Agriculture Grassland Soil and Water Research Station, Riesel, Texas. One site was cultivated for crop production and the other grass pasture. Significant variations in resistivity and soil-moisture dynamics between the two sites were observed in the upper 2 m of the soil, especially within the root zone. It could be inferred that the continuous pulverization of the soil in the cultivated site has created a situation where the moisture easily bypasses the near-surface with subsequent accumulation at depth in the soil. On the contrary, following rainfall, moisture is preserved around the root zones in the pasture and it is apparent that the rate of water percolation through the soil is lower. In general, this study shows that, an integrative hydrogeophysical and hydropedological method is a potentially viable approach for characterizing management-induced changes in vadose zone properties and for visualizing spatial pattern of moisture flux in soils.