Geoscience Reference
In-Depth Information
5.11 ReSIStIvIty Method ApplICAtIonS In AGRICUltURe
Research investigations have provided some valuable insight on potential applications and limita-
tions with regard to using resistivity methods for agricultural purposes. There are clear indications
that resistivity methods can be a valuable tool for assessing salinity conditions in farm fields
(Rhoades et al., 1976, 1990). Kravchenko et al. (2002) combined topographic information and EC
a
data (obtained with a Veris 3100 Soil EC Mapping System) to map soil drainage classes. Studies
have also focused on determining the relationship between various soil properties and the apparent
soil electrical conductivity (σ
a
, EC
a
) as measured with galvanic contact resistivity methods. Using
conventional resistivity equipment at a location near Quebec City, Canada, Banton et al. (1997)
found that EC
a
was moderately correlated with soil texture (% sand, % silt, and % clay) and organic
matter, but not with porosity, bulk density, or hydraulic conductivity. Johnson et al. (2001) found
a positive correlation at their Colorado test site between EC
a
(measured with a Veris 3100 Soil EC
Mapping System) and bulk density, percentage clay, laboratory-measured soil electrical conduc-
tivity, and pH; but a negative correlation between EC
a
and total and particulate organic matter,
total carbon, total nitrogen, extractable phosphorous, microbial biomass carbon, microbial biomass
nitrogen, potentially mineralizable nitrogen, and surface residue mass. These two studies (Banton
et al., 1997; Johnson et al., 2001) imply that soil properties can interact in a complex manner to
affect the EC
a
measured with resistivity methods.
The apparent resistivity (or apparent electrical conductivity) of a soil can also be measured with
electromagnetic induction methods. Studies carried out using electromagnetic induction methods
have shown the feasibility of using EC
a
for estimating herbicide partition coefficients (Jaynes et al.,
1995), determining clay-pan depth (Doolittle et al., 1994), and monitoring soil nutrient buildup from
manure applications (Eigenberg and Nienaber 1998). Consequently, with the proper equipment, it is
probable that resistivity methods could also be employed to estimate herbicide partition coefficients,
determine clay-pan depth, and monitor soil nutrient buildup.
A rather interesting example regarding an agricultural application of resistivity methods involved
using a constant separation traversing resistivity survey to provide insight at a field research facil-
ity on the soil salinity impact due to different drainage water management practices. Figure 5.16
shows the field research site setup composed of four test plots. No buried drainage pipe network was
installed at the C1 test plot. Test plot C2 contained a buried drainage pipe network, but this drainage
pipe network was used only to remove excess water from the soil. Test plots S1 and S2 were subirri-
gated during the growing season. Subirrigation can be described as the addition of water to a buried
drainage pipe network for the purpose of irrigating crops through the root zone.
75
41.3385
70
C1
65
41.3380
N
C2
60
41.3375
55
S1
41.3370
50
Lysimeter and
Monitoring Well Group
45
41.3365
S2
40
-84.434
84.433
-84.432
84.431
-84.430
Longitude
35
fIGURe 5.16
Apparent soil electrical conductivity (EC
a
) map of field research facility used for assessing
different drainage water management strategies. Values for EC
a
are in mS/m.
