Spatial Variability of Soil Moisture and Its Correlation with Soil Texture As Affected by Land Use.

Soil moisture is of critical importance to plant water uptake, microbial transformation, and solute transport. The field heterogeneity in soil physical properties and vegetation are believed as the main reasons leading to the highly variable soil moisture in both space and time. A precise description of spatio-temporal behavior of soil moisture is required in hydrological models as well as agricultural management. This study is aimed to quantify the temporal dynamics of spatial variability of soil moisture and its correlation with soil texture within and across two land use systems. A 48m by 3m transect located at the University of Kentucky’s Spindletop Research Farm, Lexington, KY, is evenly distributed across two established land use systems, cropland and grassland. Soil matric potentials at depths of 10, 30, 50, 70, 90 and 110cm were investigated along the transect at 1m interval using a hexagon of six tensiometers. A parallel set of capacitance probes was installed 1m apart to monitor soil water content at 10cm increments down to 1m depth. Meanwhile, a 100cm soil core was taken at every 1m and divided into 10cm increment for soil texture analysis. After killing all the plants by herbicide in spring, matric potential and soil water content were measured weekly. With this experimental design, we were able to 1) analyze the spatial variability of matric potential and soil water content at different depths over time; 2) investigate the spatial correlation between soil moisture and soil texture within and across two land use systems; 3) explore the influence of mean soil moisture on the spatial structures of matric potential and soil water content; and 4) derive the field soil water retention curve at high spatial resolution.