Pedon-Scale Soil Property Uncertainty Estimates: Insights from High-Depth-Resolution, in-Situ, Visible Near Infrared Spectroscopy.

Collection of soil property data is expensive.  For field surveys, compromises need to be made between spatial or depth-wise resolution of sample collection and the cost of sample analysis.  In an attempt to minimize the cost of soil profile measurements, traditional soil sampling often utilizes composite soil samples collected on fixed depth intervals or horizons.  These composite samples provide information on the expected value of a soil property within given depth interval but provide no information on the variability of soil property within these intervals.  In order to estimate the variability of soil properties within depth intervals, more samples are needed; a prospect that is unpalatable or cost-prohibitive with traditional laboratory measurements.  In this study we demonstrate how new in-situ visible near infrared (VisNIR) spectroscopic techniques can provide insight into the pedon-scale variability of soil properties.  We utilized a penetrometer-mounted VisNIR probe to collect in-situ VisNIR at high-depth-resolutions (5 cm).  High-resolution in-situ VisNIR provided soil data on resolutions that were heretofore unavailable.   This new high-depth-resolution data can provide novel information on inter-horizon variability of soil properties.