Tuesday, November 14, 2006
178-23
Geophysical Investigations of Soil Moisture at the Univ of Mississippi Soil Moisture Observatory.
Robert M. Holt, Craig Hickey, and Matthew S. Aufman. Univ of Mississippi, Dept of Geology and Geological Engineering, 118 Carrier Hall, University, MS 38677
Geophysical and remote sensing technologies are being increasingly used to investigate the properties of shallow soils. To provide a facility for detailed study of soil – geophysical interactions, we have constructed a Soil Moisture Observatory (SMO) at the University of Mississippi (UM). The 5 acre SMO is located in a former agricultural field at the UM Field Station, a 740 acre tract of land with restricted access located 11 miles from the UM campus in Oxford, Mississippi. The soils present at the SMO consist of silty and sandy loam. We have collected over 120 continuous soil cores using a direct-push sampling probe and installed 120 shallow neutron access tubes at the site. Continuous soil samples were taken to a depth of 1.5 m and analyzed for particle size distribution, porosity, bulk density, iron content, moisture content. At each of the access tube locations, we have collected over 18 months of bi-monthly observations of soil moisture content, apparent electrical conductivity determined from a Geonics EM38, and electrical resistivity determined using a Stinger electrical resistivity meter. Our studies of loamy soils in north Mississippi show that temporal variations in soil moisture influence EM results and suggest a complex relationship between soil moisture and EM measurements. We are attempting to exploit this relationship and develop pedotransfer function models, using a neural network model, to predict soil moisture from EM and soil property data.