Sensors exist that allow rapid mapping of bulk soil electrical confurther research. Variation in bulk soil EC may occur ductivity (EC); however, the utility of these sensors for Kentucky producers is unknown. The purpose of this study was to assess the at spatial and temporal scales including the microscale nature and the causes of soil EC variability and to make a first assess-(variation in EC at distances or times less than the ment of its potential utility in Kentucky, particularly for fields consampling interval) and macroscale (variation in EC at taining soils derived from limestone residuum overlain by loess. Varidistances or times equal to or greater than the sampling ous geostatistical, correlation, and regression analyses were conducted interval). Errors associated with mapping procedures, at seven locations to examine EC map variability. Sensor drift and such as interpolation, are a function of measurement errors associated with changes in coulter depth were minimal. Bulk intensity and have been given considerable attention in soil EC related fairly well with clay content across locations and the literature for grid soil sampling (e.g., Mueller et al., sample dates (r 2 ϭ 0.40); however, many site-and time-specific correla-2001; Mueller and Pierce, 2003) but not EC mapping. tions were better. Clay (maximum r 2 ϭ 0.75), moisture content (maxi-It would be ideal if measurement error, microscale varimum r 2 ϭ 0.76), Ca (maximum r 2 ϭ 0.67), and Mg (maximum r 2 ϭ 0.64) were positively correlated with EC, and depth to argillic or ability, temporal variability, and errors associated with cambic horizon (maximum r 2 ϭ 0.62), depth to fragipan (maximum mapping were small and if macroscale spatial variability r 2 ϭ 0.81), and depth to bedrock (maximum r 2 ϭ 0.32) were negatively accounted for the greatest proportion of the EC variabilcorrelated with EC. A multiple-regression model (R 2 ϭ 0.70) was ity observed. developed to predict EC that included nine factors: clay, sand, soil Many of the factors governing soil EC variability are moisture, buffer pH, base saturation, Ca, soil temperature, depth to understood. The spatial and temporal variability of bulk cambic and argillic horizon, and slope. Soil EC variability was spatially soil EC is affected by the complex movement of elecstructured, and spatial patterns were stable over time; however, the trons through soil. Electrons may travel through the degree to which these patterns could be observed depended on the water in soil macropores, along the surfaces of soil minmapping procedures used. Our research suggested that EC mapping erals (i.e., via exchangeable ions), or through alternating may have utility for Kentucky farmers.

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Utilizing soil electrical conductivity (EC) measurements and terrain attributes for precision management will require secondary soil information for adequate interpretation. The objective of this study was to determine whether readily available second-order soil surveys were of adequate quality to aid with interpreting soil EC and terrain data. For three locations in Kentucky, USA, first-order soil surveys were created, second-order surveys reports were obtained, elevation was measured and used to calculate terrain attributes (slope, aspect, plan curvature, profile curvature), and bulk soil electrical conductivity was measured. Three analytical methods (an ordinary least squares analysis and two random field analyses), visual map assessment, and examination of least-squares means were used to assess the relationships between soil EC measurements, terrain attributes and first-and second-order soil surveys. The OLS and random field analyses were problematic. However, the ranking of the OLS F-statistics appeared to reflect the general relationship between landscape variables and first-order soil surveys. The landscape variables related particularly well with soil properties that had been impacted by past soil erosion. Unfortunately, however, second-order soil surveys in this study were not created at suitable scales to adequately interpret EC and terrain data regarding erosion history or other attributes. While these surveys may provide some useful information, field measurements, sampling, and observations will likely be required to develop high quality interpretations of soil EC and terrain attribute data.