IMPACT OF SOIL PHYSICAL AND CHEMICAL PROPERTIES ON THE VARIABILITY SATURATED HYDRAULIC CONDUCTIVITY (KSAT) AT SMALL SCALE

Saturated hydraulic conductivity (Ksat) plays a significant role in controlling drainage and movement of solutes in soils. The purpose of the current study was to examine the impact of different soil properties including the soil nutrients on the variability of Ksat. Johnson Permeameter was used to determine the Ksat from six randomly selected sampling locations along the slope (150 m transect at 25 m intervals) of the James Madison University (JMU) Student Farm. Soil samples were collected (0-60 cm depth at 20 cm intervals) from each location to analyze soil physical (particle size distribution, organic carbon, bulk density) and chemical (pH, EC) properties. Laser diffraction method was used to determine the particle size distribution (PSD) of the soil samples. Soil organic carbon (OC) content was analyzed using the loss on ignition method. Bulk density, pH, EC, and porosity of the samples were determined following the USDA, NRCS guidelines. Data were analyzed using a forward stepwise regression model (using R statistical software) to determine the soil properties that influence on the Ksat. Results of the study revealed that there is a greater variability in Ksat along the gradient. Part of this could be due to the variability of soil texture along the gradient as we observed a significant increase in the sand content (%) in the topsoil layer (0-20 cm) along the gradient. Besides, there was a gradual reduction in the bulk density towards the downward slope irrespective of the sampling depth. As a result of decreasing the bulk density, we observed a gradual increase in the porosity (%) which could increase the permeability of the soil. Regression analysis showed that there was a significant positive correlation between the Ksat and the organic carbon (%), EC, sand (%) and pH. Conversely a significant negative correlation was observed between Ksat and clay (%) contents. These findings suggested that there is a greater spatial variability of ksat especially with varying soil conditions at the small-scale level.