Monday, November 5, 2007 - 11:15 AM
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Soil Moisture Variation Reveals Soil Textural Features Using Electromagnetic Induction Mapping.

Hiruy Abdu1, David Robinson2, and Scott Jones1. (1) Utah State University, 4820 Old Main Hill, Logan, UT 84322-4820, (2) Stanford University, Department of Geophysics, Stanford, CA 94305-2215

Knowledge of the spatial distribution of soil textural features is important for determining soil moisture storage and soil hydraulic transport properties. Geophysical methods, in particular electromagnetic induction (EMI) surveys, are being used to infer soil spatial heterogeneity at the field scale due to their non-destructive nature, rapid response and ease of integration onto mobile vehicular measurement platforms. From EMI measurements the soil apparent electrical conductivity (ECa) is acquired and can be related to a number of soil properties including: soil salinity, moisture content, and texture. The purpose of this study is to develop a procedure to non-invasively map field-scale soil texture with minimal calibration. Geo-referenced ECa measurements were taken using a DUALEM 1-S ground conductivity meter on four days with different field soil water contents on a 50 x 50 m field site at the Utah State University's Greenville Farm. Temporal stability analysis was then used on the EMI maps to determine if spatial patterns appear in the data. Our results suggest that there are distinct zones with different textural properties. This non-invasive mapping approach has the potential to reveal the spatial distribution of time-invariant subsurface properties using repeated EMI surveys taken over a range of field soil moisture levels. These maps would be informative for modeling and experimental design purposes in ecological, environmental and agricultural applications.