Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 1/1/2008
Publication Date: 6/10/2008
Publication URL: http://hdl.handle.net/10113/20207
Citation: Daniels, J.J., Vendl, M., Ehsani, R.M., Allred, B.J. 2008. Electromagnetic induction methods. In: Allred, B.J., Daniels, J.J., Ehsani, M.R. Handbook of Agricultural Geophysics. Boca Raton, FL: CRC Press. p. 109-128. Interpretive Summary:
Technical Abstract: Electromagnetic induction geophysical methods are finding greater and greater use for agricultural purposes. Electromagnetic induction methods measure the electrical conductivity (or resistivity) for a bulk volume of soil directly beneath the surface. An instrument called a ground conductivity meter is commonly employed for relatively shallow electromagnetic induction investigations. In operation, an alternating electrical current is passed through one of two small electric wire coils spaced a set distance apart and housed within the ground conductivity meter, which itself is positioned at, or a short distance above, the ground surface. The applied current produces an electromagnetic field around the "transmitting" coil, with a portion of the electromagnetic field extending into the subsurface. This electromagnetic field, called the primary field, induces an alternating electrical current within the ground, in turn producing a secondary electromagnetic field. Part of the secondary field spreads back to the surface and the air above. The second wire coil acts as a receiver measuring the resultant amplitude and phase components of both the primary and secondary fields. The amplitude and phase differences between the primary and resultant fields are then used, along with the inter-coil spacing, to calculate an "apparent" value for soil electrical conductivity (or resistivity). This chapter discusses in detail the basic principles, equipment, field procedures, and data analysis/interpretation for electromagnetic induction methods.