Geoscience Reference
In-Depth Information
tAble 1.2
physical properties Responded to by Geophysical Methods
Geophysical Method
physical property
Resistivity
Electrical resistivity (or electrical conductivity)
Electromagnetic induction
Electrical conductivity (or electrical resistivity)
Ground-penetrating radar
Dielectric constant and electrical conductivity
Magnetometry
Magnetic susceptibility and remanent magnetism
Self-potential
Electric potential gradient
Seismic
Density and elastic moduli (bulk modulus, shear modulus, etc.)
multiple geophysical and nongeophysical spatial data sets. Consequently, GIS will play a
greater role in the analysis of geophysical data collected in agricultural settings. Further-
more, as the practice of precision agriculture continues to grow, there is expected to be an
increasing need to input geophysical data into the GIS used to make proper management
decisions in regard to different areas of a farm field.
6. Expert system computer software and learning-capable computer software incorporating
neural networks will be developed for specific agricultural applications to automatically
analyze and interpret geophysical data.
7. Tomographic procedures will be employed to obtain geophysical data in agricultural set-
tings when the situation is warranted. It is usually not possible to conduct geophysical sur-
veys in an agricultural field during the growing season, once the crop emerges and begins
to develop. Tomographic data collection and analysis procedures are a potential solution to
this field access problem, allowing the within field horizontal spatial pattern of a physical
property to be determined without actually having to obtain geophysical measurements
inside the field. Tomographic data collection and analysis procedures can also provide
valuable geophysical information even for circumstances when field access is not a prob-
lem. For the geophysical field measurement tomographic approach, geophysical energy
source and sensor locations are moved along the perimeter of the field. They will typically
involve multiple source and sensor positionings in which the geophysical sensor locations
are always on opposite or adjacent sides of the field with respect to the side of the field
where the geophysical energy source is located. A map of the horizontal spatial pattern for
some physical property within an agricultural field is then generated with measurement
data from a sufficient number of geophysical source and sensor positionings used as input
for image reconstruction computer software employing inversion techniques.
8. The application of geophysical methods to agriculture will eventually become a well-
recognized subdiscipline of geophysics, at which time it may become appropriate to use the
contracted term “agrigeophysics” instead of the longer term “agricultural geophysics.”
RefeRenCeS
Allred, B. J., J. J. Daniels, N. R. Fausey, C. Chen, L. Peters, Jr., and H. Youn. 2005a. Important considerations
for locating buried agricultural drainage pipe using ground penetrating radar.
Appl. Eng. Agric.
v. 21,
pp. 71-87.
Allred, B. J., M. R. Ehsani, and D. Saraswat. 2005b. The impact of temperature and shallow hydrologic con-
ditions on the magnitude and spatial pattern consistency of electromagnetic induction measured soil
electrical conductivity.
Trans. ASAE.
v. 48, pp. 2123-2135.
Allred, B. J., M. R. Ehsani, and D. Saraswat. 2006. Comparison of electromagnetic induction, capacitively
coupled resistivity, and galvanic contact resistivity methods for soil electrical conductivity measure-
ment.
Appl. Eng. Agric.
v. 22, pp. 215-230.
