ῑ ῌ ῐ
J. Jpn. Soc. Soil Phys.
ῐ῎῍ῑῒ῏
No. 23, p. .-῍/- ῎,**,῏Application of Electromagnetic Induction Terrain
Conductivity Meter to salinity assessment
in salt-a#ected soils
ῌRegional salt-a#ected soils map in northeastern Thailandῌ
Chaiyanam DISSATAPORN*, Hajime NARIOKA**, Pramot YAMCLEE*
and Somsri ARUNIN** Land Development Department, Phahon Yo Thin Road, Chatuchak,Bangkok +*3**, Thailand** Okayama University, -ῌ+ῌ+ Tsushima-naka, Okayama 1**ῌ2/-*, Japan
Abstract
The electromagnetic induction terrain conductivity meter, “EITCM”, has been used for thesalinity assessment in salt-a#ected soils in northeastern Thailand. This paper brieﬂy discusses
the applicability of the electromagnetic method for delineating the salt distribution within thelandscape and determining the salt content in soil at the depth up to -* m. This information
together with hydrological data and present landuse is useful for the base of the salinity
management in northeastern Thailand. A case study presented the results of the use of theelectromagnetic terrain conductivity meter in some major salt-a#ected soils of Nakhonratchasima province. The results of the investigation revealed that the source of salt in theprocess of soil salinization underlies the salt-a#ected soils. High-elevated areas play an importantrole for the water supply in the process of soil salinization. Variations of the reading might be dueto the salt content, moisture content and soil type. Accuracy of the reading must be carefully
considered when the survey for soil proﬁles is carried out in the areas where high clay content andlow moisture content.
Key words : Electromagnetic induction terrain conductivity meter, electrical conductivity, salta#ected soils map, northeastern Thailand

Introduction
Salt-a#ected soils in the northeastern Thailand spatially spread in low-lying paddy ﬁelds.
The a#ected areas were estimated of seventeen
percent of the region or ,.2/ million ha (Department of Land Development, +323). The majorsoluble salt is NaCl in the soil solution and in
the groundwater resulting in the adverse
e#ects to soils and plants as well as environments. The salt derives from rock salt of theMahasarakram Formation underlying salta#ected lands and contaminates to shallow

groundwater (Williamson, et al. +322). The further extension of salt-a#ected soils is due todeforestation in recharge area, salt making, theconstruction of reservoirs and the mismanagement of irrigation (Arunin, +32.). Salt-a#ectedsoil map was developed through the interpretation of aerial photos, satellite imagery,hydrogeological maps and soil survey. Field
checks were done by collected some soil samples for laboratory analysis. Mapping units
were classiﬁed by degree of salinity into /classes as very strongly, strongly, moderately,slightly and non salt-a#ected areas and poten-44  23

tial salt-source areas (Department of Land Development, +33+).
Counter measures for the salinity control in
the northeastern Thailand are based on the
mapping units of the salt-a#ected soil map.
Agronomic practices and soil amendments including organic and inorganic substance aswell as green manuring are recommended forincreasing rice yields in slightly and moderately salt-a#ected soils, while salt tolerant trees
and halophytic grasses are cultivated in verystrongly and strongly salt-a#ected soils.
Reforestation with trees of salt tolerance, fastgrowing, and high water use is recommended
for preventing the secondary salinization in
potential salt-a#ected soils (Arunin, +33,).
The salinity assessment is essential to ensurethat recommendations for the management ofsalt-a#ected soils is fruitful. Mismanagement
may cause further expansion of salt-a#ectedsoils. Further more, it will be laborious topersuade farmers to acquire new technology(Abrol and Fireman, +311).
Various methods or techniques can be used
for assessing salt-a#ected soils. Extent of salt
patches, native halophytes in landscapes andcertain symptoms of crops as a result of stressimpound by salt are simple characteristics ofsalt a#ected-soils (Arunin, +32.).
But thedegree of salinity can only be speciﬁed byanalyzing soil samples for the concentration ofsoluble salts as electrical conductivity of thesaturation paste extract (Ece, dS/m) (Soil Science Society of America, +313). Sources of salt
underlie salt-a#ected soils. Subsurface conditions can be investigated at the shallow depth
which a hand auger can be drilled. Poweraugurs or drilling equipment can not be
employed. Subsurface conditions can be partly
obtained from one hydrogeological map at + :/**,*** scale which is only suitable for broad
scale purposes (Piancharaen, +31-). Cores drilling for salt, petroleum and groundwater exploitations are available in many places(Krairapanond, et al., +33, ; Japakasetr and
Suwanich, +32.). Groundwater hydrology is,**,investigated with the installation of piezometers in many major salt-a#ected soils in thenortheastern Thailand in order to investigating the relationship between groundwater andsalinity hazards in the region (Dissataporn etal., +33-).
As salt-a#ected soils are dynamic, more replication of sampling are required especially inlarge-scale mapping. Rapid, portable, nondestructive and surface applied method forassessing the soil electrical conductivity andlocating the spatial distribution of salt withinsoil proﬁles as well as within a landscape arerecommended. The recent commercial fourelectrode and electromagnetic technique are
accepted as the practical procedure for immediate assessing salt-a#ected soils (Rhoades, +33,).
The four-electrode resistivity techniquemeasures the average soil electrical conductivity by sending the electrical current into a soil
proﬁle through current electrodes while potential electrodes read the voltage di#erences.
The depth of reading depends on the spacing
between current and potential electrodes. A
regression model for converting the bulk soil
electrical conductivity to the laboratory value
was developed (Department of Land Development, +323)
The electromagnetic terrain conductivity
technique is a simple and rapid method fordelineating the distribution of average soluble
salt in a soil proﬁle from the soil surface to thedepth of 1./, +/ and -* m when the coil spacingof +*, ,* and .* meters, respectively (McNeil,+32*). The technique is widely used for quantify the soil salinity (Cameron et al., +32+ ;McFarlane, et al., +321 ; Williams and Hoey,+321 ; Dixon, +323 ; Cannon, et al., +33.). The
advantage of this instrument is rapidness but
there are various factors which a#ect the terrain conductivity (McNeill et al., +33,) Linear
regressions between the soil electrical conductivity and the terrain conductivity at each
depth of sounding were developed (Cook andWalk, +33,). The low conductivity on the
upland corresponds to the recharge area while῎ῌ῍ : Application of Electromagnetic Induction Terrain Conductivity Meter to salinity assessment in salt-a#ected soils

45

the high conductivity indicates discharge area
(Bullock and Williams, +321). Williams andArunin (+33*) identiﬁed the recharge and discharge area from the average ratio of the electromagnetic terrain conductivity of -* m depth
to ,* m depth, -* m depth to 1./ m depth and +/m depth to 1./ m depth of sounding at Nakorn
Ratchasima in northeastern Thailand. The
ratio greater or less than unity indicates recharge and discharge area, respectively.
The objective of this paper is to describe theuse of the electromagnetic technique for salinity assessment and to determine the accuracyof this technique in identify the soil and watersalinity of the salt-a#ected soils in northeastern Thailand.
Principle of operation and instrumentation
The EITCM measures the average apparent
electromagnetic terrain conductivity (Eca) of
the soluble salt concentration in a soil proﬁle in
mS/m. The terrain conductivity of +.* mS/m isequal to ,/ ppm of NaCl concentration. The
instrument consists of the transmitter and receiver meters connected with the magnetictransmitter and receiver coils, respectively.
The conﬁgurations of coils can be applied inhorizontal and vertical dipole mode which provide the depth of sounding of *.1/ and +./ timesof the distance between two magnetic coils,
respectively. Surveying the soil conductivity
can be done at the coil spacing of +*, ,* and .*m (Fig. +).
The transmitter coil with an alternating current generates time-varying magnetic ﬁelds at
frequency of 0,.**, +,0** and .** Hz to the soil
proﬁle, respectively. They induce small currents in the soil proﬁle, and they produce secondary magnetic ﬁelds. The magnitude of thesecondary magnetic ﬁeld depends on the concentration of soluble salt, moisture content andclay content. The receiver coil determines theprimary and secondary magnetic ﬁeld, and calculates the ratio between primary and secondary magnetic ﬁelds, which yield the bulk apparent electrical conductivity of the soil

Fig. +

Electromagnetic induction terrain conductivity meter, EITCM, in horizontal
dipole mode and vertical dipole mode.

proﬁle. The depth of reading depends on the
primary electromagnetic current frequency, on
the distance between the transmitter and receiver coil and on the coil conﬁguration. The
coils in horizontal dipole mode with the coilseparation of +*, ,* and .* m and primary electromagnetic currents at frequency of 0,.**,+,0** and .** Hz provide the depth of soundingof 1./, +/ and -* m from the soil surface, whilethat in vertical dipole mode conﬁguration provides depth of sounding of +/, -* and 0* m fromthe soil surface, respectively. Survey of terrain
conductivity by the EITCM is commonly usedin horizontal dipole mode as the reading invertical dipole mode is sensitive to low conductivity materials and geologic structure, fractures while the reading in horizontal dipole
mode is insensitive to those of materials. From
this reason, the accurate conductivity can beobtained from the horizontal dipole mode. Further more, alignment of coils in vertical dipole
mode is very di$cult to adjust (McNeil, +32-).
Operating procedure
Two persons are needed for operating the
EITCM. The instrument needs to set up inorder to cut down the magnetic ﬁeld of earth46  23

and air before starting survey. This set upprocedure is repeated during the survey wherever encounter low terrain conductivity area.
The transmitter coil in horizontal dipole modeis placed vertically to the soil surface where
subsurface features are interested. Electromagnetic currents are sent from the transmitter coil in the horizontal direction. The cable,.* m long, is connected between the transmitter and receiver coil. The coil and frequency
current switch are ﬁrstly set at .* m distance.
Receiver coil is moved forward and backward
upon the coil separation meter in order to ﬁx
the coil separation at .* m apart. Digital bulk
apparent electromagnetic conductivity in ms/
m from the soil surface to the depth of -* m isrecorded as well as landuse, landform and salt
patches. The coil separation and frequency
current are set to ,* and +* m, respectively.
The receiver coil is moved forward to transmitter coil to ,* and +* m spacing, respectively.
Repeatedly procedure is done in order to measure bulk salt concentration at the depth of +/and 1./ m. Vertical dipole mode can be done ashorizontal dipole mode by laying down bothcoils on the soil surface. Electromagnetic currents are sent from the transmitter coil in vertical direction. As the EITCM is sensitive to
any metallic material, the measurement should
escape from fences and electricity cables.
Survey technique
The electromagnetic induction survey using
the EITCM have been carried out investigatedin salt-a#ected areas of northeastern Thailand
since +33,. The horizontal dipole mode withthe coil separation of +*, ,* and .* m was usedat the spacing of one-kilometer grid basis. Topographic maps at scale of + : /*,*** and aerial
photos were used for locating the geographic
position. Later on, Global Positioning System(GPS) was employed for rapid locating. Bulk
apparent electromagnetic terrain conductivity,.2,02- records, at depths of 1./, +/ and -* m fromsoil surface with global coordinates were obtained and recorded in database. Further more,when close spacing need to be surveyed and,**,Fig. ,

Salinity assessment
Thailand.

in

northeastern

the geographic position can not be accurately
located by GPS. Sites are marked on aerial
photos and later geographic positions are readby computer program (Fig. ,).
Interpretation
The salinity data have not yet been converted into standard soil salinity because ofunavailable instruments for collecting soil
samples. The computer software Surfer for
Windows was used for contouring the apparent electromagnetic conductivity of the soil
proﬁle at depths of 1./, +/ and -* m from the soil
surface, respectively. Contours are producedby kriging method which is a useful geostatistical gridding method (Surfer for Windows,+330). Salinity is classed by adverse symptomsof plant and soil due to salinity into / classes as
non-salt-a#ected soils (*ῌ2* mS/m), slightly
salt-a#ected soils (2*ῌ+,* mS/m), moderately
salt-a#ected soils (+,*ῌ+0* mS/m), severely salta#ected soils (+0*ῌ,** mS/m) and very severely
salt-a#ected soil (,** mS/m).
Isoconduc-ῑῌῐ : Application of Electromagnetic Induction Terrain Conductivity Meter to salinity assessment in salt-a#ected soils

tivity in Surfer format was exported in to DXF
interchange ﬁles. They were read into digitalformat of Arc info. Digital map of salt-a#ectedsoils covering the whole salt-a#ected soils ofnortheast Thailand is being developed.
Case study
Site characterization
The study area is in Nakhonratchasima province where salinity is major problem of theKorat basin. Soils are spread on the geologic
Mahasarakram formation that is believed tothe source of salt for the process of salinization(Phiancharoen, +31-). A topographic map ispresented in Fig. - a with the +* m contour andmain drainage. A height above mean sea levelof the area ranges from +2* to ,.* meter. Mostof the area is in low terrace and slightly undulating. Lam Chiang Krai and Lam Khang
Phlu, which is tributary of Chi River, are themain drain of the area. The average rainfall
and evapotranspiration is +,+*2 and +,21- mm
per year, respectively. According to the soil
salinity map of the northeastern Thailand at
the scale of + : +**,***, salt-a#ected soil spreads
in the lowest elevation and along the river.
The degree of salinization is in scale of very
severely, severely and moderately salt a#ectedsoil (Department of Land Development, +33+).
Methodology
Salt-a#ected soils of Nakhonratchasima province were surveyed by the EITCM in horizontal dipole mode with the coil spacing of +*, ,*and .* meters. The average apparent terrain
conductivity, ,3- records, at the depth of 1./, +/and -* m from soil surface were recorded including present landuse, landform and salt
patches. Groundwater salinity from nested piezometers at the depth +/ m from the soil surface were collected. The statistic package,
SPSS for Windows, was used for analyzing thecharacteristic of the terrain conductivity andthe linear relationship between the terrain conductivity and the depth of reading. The salinity distribution at each depth of reading andgroundwater salinity was contoured by com-47

puter program, Surfer for Windows. EXCEL
drew the salinity distribution by depth andposition of site of reading from mean sea level
along cross section A-B.
Result of measurement
The terrain conductivity from the soil surface to the depth of 1./, +/ and -* m from thesoil surface ranged from +3ῌ-**, -+ῌ-** and .,ῌ
-** mS/m, respectively. The means values ofterrain conductivity at the three depths ofreading were +-2, +/, and +1, mS/m, respectively. The standard deviation of the terrain
conductivity at the depth of 1./, +/ and -* mvaried from 0/, 0, and 0* mS/m, respectively.
The high correlations were found among thethree depths of reading of 1./ῌ+/, 1./ῌ-* and +/ῌ
-* with the correlation coe$cient of *.3/., *.2++and *.22*, respectively. It was observed fromthe frequency distribution of the terrain conductivity that there were +0 stations where theterrain conductivity at the three depth of reading were -** mS/m, which is the maximum
reading of this instrument. The regression
analysis between the terrain conductivity ofthe three depths was developed in order toclarify the salt distribution within the soil
proﬁle. Linear regression equations between
the terrain conductivity at the depth of 1./, +/and -* m are as follow :V (1./ m)῏῎+0.,11῍+.**2 V (+/ m), R,῏*.3+*
V (1./ m)῏῎+-.,10῍*.211V (-* m), R,῏*.0/1
V (+/ m)῏῎,.-**῍*.3*+ V (-* m), R,῏*.1..
where V (1./ m) : Average conductivity of soil
proﬁle to 1./ m depth
V (+/ m) : Average conductivity of soil
proﬁle to +/ m depth
V (-* m) : Average conductivity of soil
proﬁle to -* m depth
The coe$cient of determination (R,) of thethree regression equations were 3+, 0/.1 and
1...ῌ, respectively.
The linear regression
models can be explained 3+, 00 and 1.ῌ of thevariation of the dependent terrain conductivity, respectively. From the three regression
equations, it can be explained that when V (1./m) and V (+/ m) is equal to +, V (-* m) is greater

48ΐῐ῎῔῕ῑ ῒ 23 ῏ ῌ,**,῍than V (+/ m) and V (1./ m), while V (+/ m) is as
well greater than V (1./ m). Thus, the averageterrain conductivity of soil proﬁle increases
from soil surface to the maximum depth ofreading. Further more, the terrain conductivity at the depth of +/ and -* m from the soil
surface can be estimated from the terrain conductivity at 1./ m with these regression equations.
Salt distribution maps at the depth of 1./, +/and -* m from the soil surface with map units
and the topographic map of the study area
were shown in Fig. -. The magnitude of apparent terrain conductivities were classed into
non, slightly, moderately, severely and very
severely salt-a#ected soils in order to characterize the distribution of the salt concentration
within a soil proﬁle and within a landscape.
Fig. - a and -b indicated that there was anaccumulation of salt in soil proﬁle from the soil
surface to the depth of 1./ m. Very severely
salt-a#ected soils spatially spread in the alluvium plain of the main drainage of the study
area. It occurred mostly in the areas where theelevation is less than ,** m. Non salt-a#ectedsoils where the terrain conductivity is less than
2* mS/m were situated at the elevation greaterthan ,+* m. Isoconductivity maps of the soil
proﬁles at the depth of +/ and -* m from soil
surface showed that the areas of very severely
salt-a#ected soils increased with the depth ofsounding. Further more, the area of non salta#ected soils decreased with the depths ofsounding, indicating the increase of the soluble
salt content with the depth under non-salt
a#ected soils at the depth more than 1./ m fromthe soil surface (Fig. - c and - d). The result ofcross-section AB showed that the degree ofsalinity in the high elevation areas was low
and gradually increases further down slope.
Low salinity could be detected in the undulating area. Salinity sharply increased with depth
in alluvium plain while in the high elevation
area there were little change in the terrain
conductivity with depth (Fig. - f).
Groundwater salinity from the nested pie-zometer at the depth of +/ m from the soil
surface was shown in Fig. - e. Groundwatersalinity ranges from less than + to ./ dS/m. It
was found that low salinity groundwater islocated in the high elevation area while very
high salinity is located in the ﬂood plain.
Discussion
The EITCM was employed for the salinity
assessment in northeastern Thailand. It has
been proved that this technique can provide
reliable data on the salinity distribution withina landscape and within a soil proﬁle. The
technique is easy for application, as no soil
samples are taken. Further more, it is thesurface treatment without inserting electrodes
as Four-probe resistivity. The receiver coils
can be adjusted from the coil separation metercomparing to four-probes resistivity meter,
which need to adjust electrode spacing by tapemeasuring. Two persons are minimum requirement for operating electromagnetic terrain conductivity.
As the instrument can detect an average terrain conductivity of a soil proﬁle from the soil
surface to the depth of 1./, +/ and -* m, it not
only enables to locate the salt concentration
within the landscape but also within the soil
proﬁle which can not be observed by aerial
photos or satellite imagery. Data collectedfrom the study area can indicate that salta#ected soils occur in the ﬂood plain of thethree main drain of the study area. The sourceof salt can be situated at the depth of +/ and -*m from the soil surface in the salt-a#ected soils.
Further more, the terrain conductivity of asoil proﬁle, greater than +,* mS/m, can befound at the depth of -* m from the soil surface
in the high-elevated areas. The salt content
situated at the depth more than -* m from thesoil surface may be higher than +,* mS/m if
the instrument can operate at depth more thanthat of from soil surface. From this reason it
can be shown that salt underlies Korat Basineven in the high-elevated area that were classiﬁed as non salt-a#ected soils (Piancharoen,῎ῌ῍ : Application of Electromagnetic Induction Terrain Conductivity Meter to salinity assessment in salt-a#ected soils

Fig. -

49

Topographic map (a), isoconductivity maps (mS/m) at depth 1./, +/ and -* m (b, c, d)groundwater salinity (dS/m) at depth +/ m (e) and cross section of terrain conductivity andheight from mean sea level (MSL) (f).

50ΐῐ῎῔῕ῑ ῒ 23 ῏ ῌ,**,῍+31-). Salt in the deeper proﬁles can not be
observed because of the limitation of the instrument. In addition, salinization in this area
can not occur because these areas are in thehigh elevation, and salt at the depth more than-* m can not move up to the soil surface andleaching by rainfall is normally dominant inthese areas. On the other hand, the result of theelectromagnetic survey indicates that salt in
the high-elevated areas is not situated at thedepth where it can be a source of salt in theprocess of soil salinization, ie, saline seep
(Sinanuwong and Takaya, +31.). Further more,
the high-elevated areas in the salt-a#ected soils
are the areas where they might supply waterfrom the rainfall for the process of salinization.
This local recharge should be aware of water
management for salinity control (Dissataporn
et al., +33-).
The distribution of the terrain conductivity
in the soil proﬁle at each depth can be used for
identifying the recharge and discharge area.
As in the recharge area salt is leached down thesoil proﬁle by water and accumulated in the
deeper proﬁle. While in the discharge area salt
moves up to soil the surface by the capillaryrise from the shallow saline groundwater andaccumulated in the upper soil proﬁle (Williams
and Arunin, +330). But the terrain conductivity
in the discharge areas increases with the depthof reading. This can clarify that the source ofsalt situates in the salt-a#ected soils and themagnitude of the accumulation of salt is much
more than the accumulation of salt in theupper surface by the process of the capillaryrise and the evaporation soil surface.
It is observed that sixteen sites in the very
severely salt-a#ected soils class comprised of-** mS/m for the whole depth of reading,which is the maximum reading of the instrument. Salinity in these sites may be greaterthan -** mS/m if the digital model, which canmeasures more than -** mS/m, is used (McNeil,+32*).
The distribution of the terrain conductivity
at the depth of +/ m from the soil surface partly

coincided with the groundwater salinity at thesame depth (Fig. - c and - e). It can be seenfrom this comparison that the terrain conductivity might be used for identifying soluble salt
in soil proﬁles. The variation of these two data
may be due to the di#erence in the sample
densities. Simple nonlinear regression equations of the terrain conductivity at the depth of
1./, +/ and -* m from the soil surface and theelectrical conductivity of the groundwater at
the same depth were developed (Yamclee et al.,+330). It was found that the regression equation of the terrain conductivity could explain
about 22, 11 and 2+ῌ of the variation of thegroundwater salinity at the depth of 1./, +/ and-* m from the soil surface, respectively. From
this study it can be seen that variations of theterrain conductivity may be caused by otherfactors about +,, ,- and +3ῌ, respectively.
The low terrain conductivity in the highelevated areas may be due to the low salt concentration and moisture content.
As thegroundwater level in these areas is always situated at the depth more than / m from the soil
surface. Thus, the terrain conductivity of thesoil proﬁle measured in such places may be
confounded by moisture content especiallyreading at the depth of 1./ m from the soil
surface. While in the salt-a#ected soils, thegroundwater table is always at the depth of ,ῌ
- m from soil surface. The di#erence in moisture contents can be ignored in the salta#ected soils. On the other hand, as salta#ected soils in northeast occur mostly insandy soils which clay contents are not the
major constitutes of these soil types. Thus, thevariations of the terrain conductivity in the
sandy soils are not due to clay content. The
high terrain conductivity found in the ﬂooded
plain areas of the main drain may be interferedby the clay content in the soil proﬁle (Williams
and Hoey, +321 ; McNill et al., +33,).
These variations could be accepted for thesalinity assessment in the regional scale.
Anyhow, the anomaly of the terrain conductivity and electrical conductivity of soils should῎ῌ῍ : Application of Electromagnetic Induction Terrain Conductivity Meter to salinity assessment in salt-a#ected soils

be further investigated, as the terrain conductivity is relying on not only soluble salt but
also clay and moisture. It is necessary to develop the regression equation for converting theterrain conductivity to the electrical conductivity of the saturation paste especially in theclayey soil proﬁle and in the high elevation
areas where clay content and moisture content
could interfere the terrain conductivity ; respectively. The calibration can be done for the
1./ m reading as a hand auger can be drilled.
Soil samples from the soil surface to the depthof 1./ m must be collected and mixed together.
Saturation extract of soil paste is used formeasurement of the soil electrical conductivity. Regression of the average terrain conductivity and soil electrical conductivity can be
developed. This ﬁnding will be useful forassessing the soil salinity in standard unit. As
the salinity at the shallow soil proﬁle is themain purpose for salinity assessment in agriculture production.
Since the terrain conductivity is used directly for classifying salt-a#ected soils and the
responses of the terrain conductivity for eachsoil types and landscape are not the same. The
terrain conductivity for each map unit should
be classed for each catchment area. Surveyors
can class the terrain conductivity for each map
units from salt patches and native halophytes
as well as symptom of plants.
In addition, the electromagnetic terrain conductivity meter measuring in the vertical
dipole mode is sensitive to geologic structure,faults. Salinity survey should not only measure in horizontal dipole mode for the terrain
conductivity but also in vertical dipole mode.
As faults were claimed to be a channel of the
deep saline groundwater which contacts with
the Mahasarakram Formation. This saline
groundwater leak through these channels andcontaminate to the shallow groundwateraquifer (Imaizumi et al., +330). This information is useful for considering the salinity control.
Electromagnetic terrain conductivity with51

the short intercoil spacing and the single current frequency has been useful for the salinity
assessment in the agricultural production area
as it is portable, one man operate, rapid, rootzone reading and can be related to laboratory
analysis (Dissataporn et al., +33-).
The information from the electromagnetic
technique can be considered in planning theland-use strategy for the salinity control. It
can be a basis data for reducing the cost ofhydrological study which need to install expensive piezometers.
Further more, Salta#ected soils map in GIS format can be usedwith other map layers, land use, elevation, hydrology, for predicting areas risk for salta#ected soils.
Conclusion
The EITCM was used for salinity assessing
in northeastern Thailand. This technique issurface application, non-destructive, rapid andeasy to operate. It immediately locates the salt
concentration with in a landscape and within asoil proﬁle. The results of mapping indicatedthat sources of salt in the process of the soil
salinization is underlie the salt-a#ected soil.
The deviation of the bulk conductivity withina landscape and within a soil proﬁle may comefrom the di#erence in moisture content andclay content. Subsurface conditions can beinvestigated in more details by this technique.
Anomaly of the terrain conductivity from theelectrical conductivity of soil paste must be
found out even for the shallow depth of reading.
Reference
Arbol, I.P. and M. Fireman (+311) : Alkali and saline
soil identiﬁcation and improvement for crop
production. Central Soil Salinity Research Institute.
Arunin, S. (+32.) : Characteristics and managementof salt a#ected soil in the Northeast of Thailand. --0ῌ-/+. In Ecology and management ofproblem soils in Asia. Food and Fertilizer
Technology Center for the Asian and Paciﬁc
Region. Taipei, Rep. of China.
Arunin, S. (+33,) : Strategies for utilizing salt

52ΐῐ῎῔῕ῑ ῒ 23 ῏ ῌ,**,῍

a#ected lands in Thailand. Proceeding of theInternational Symposium on Strategies for
Utilization Salt A#ected Lands. pp. +1ῌ+/, February +33,, Central Plaza, Bangkok, Thailand.
Cameron, D.R., de Jong, E., Read, D.W.L. andOosterveld, M. (+32+) : Mapping salinity using
resistivity and electromagnetic inductive techniques. Canadian Journal of Soil Science. 0+ :01ῌ12.
Cannon, M.E., Mckenzie, R.C. and Lachapelle, G.
(+33.) : Soil salinity mapping with electromagnetic induction and satellite-based navigation
methods. Canadian Journal of Soil Science. ,. :--/ῌ-.-.
Cook, P.G. and Walk, G.R. (+33,) : Depth proﬁle ofelectrical conductivity from linear combination of electromagnetic induction measures.
Journal of Soil Science Society of America. /0: +*+/ῌ+*,..
Department of Land Development (+323) : Annual
report of Department of Land Development,
Ministry of Agriculture, Bangkok, Thailand. p.
+30 (in Thai).
Department of Land Development (+33+) : Distribution of salt a#ected soil s in Northeast region. +: /**,*** map.
Dissataporn C., Tokotkla, A. and Arunin, S. (+33-) :Salt tolerance of kallar grass Leptochloa fusca(L.) Kunth. Workshop on Research Activities
of ADRC Contributed to Agricultural Development in Northeast Thailand. pp. +ῌ-, Sep +33-.
ADRC, Khon Kaen, Thailand.
Dixon, P. (+323) : Dryland salinity in a subcatchment at Glenthompson, Victoria. Australia Geographer. ,* : +..ῌ+/,.
Imaizumi, M., Wichaidit, P., Sukchan, S. and Srisuk,
K. (+330) : Mechanism of salinization ofgroundwater in Phrayuen area, northeast
Thailand. Proceeding of Seminar on Geophysical prospective for groundwater development
and hazard prevention. +, December +330.
Chareonthani H
Japakasetr, T. and Suwanich, P. (+32.) : Potash androck salt in Thailand. Mineral Bulletin no. ,.
Department of Mineral Resources. Thailand.
Krairapanond, N., Krairapanond, A., Sinthuwanich,D. and Junpet, T. (+33,) : Environmental
impact of rock salt mining operations on land
and water resources of Northeast Thailand.
Proceeding of International Symposium on
Strategies for Utilizing Salt A#ected Lands.
February pp. +1ῌ,/, +33,, Bangkok, Thailand.

-*3ῌ-,,.
McFarlane, D. J., Engel, R. and Ryder, A.T. (+321) :Investigation of a saline valley on Allandale
Research Farm. Technical report Western
Australia Department of Agriculture. No. /2 :+0.
McNeil, J.D. (+32*) : Electromagnetic terrain conductivity measurement at low induction numbers. Tech. Note TN 0. Geonics Ltd.
McNeil, J.D., Topp, G.C., Topp, W.D. and Reynolds,
W.D. (+33,) : Rapid, accurate mapping of soil
salinity by electromagnetic ground conductivity meters. SSSA Special Publication -* : ,*3ῌ,,3.
Piancharoen, C. (+31-) : Hydrogeological map ofnortheastern Thailand (Scale + : /** /**). Department of Mineral Resources. Thailand.
Rhodes J.D. (+33,) : Recent advances in the methodology for measuring and mapping soil salinity. Proceeding of the International Symposium on Strategies for Utilization Salt A#ected
Lands. pp. +/ῌ+1, February +33,, Central Plaza,
Bangkok, Thailand.
Sinanuwong, S. and Takaya, Y. (+31.) : Saline soil
in northeast Thailand. Their possible origin as
deduced from ﬁeld evidence. Southeast AsianStudies +, : +*/ῌ+,*.
Soil Science Society of America (+313) : Glossary ofsoil science terms. Soil Science Society ofAmerica. Madison, Wisconsin.
Williams B.G. and Baker, G.G. (+32,) : An electromagnetic induction technique for reconnaissance survey for salinity hazards. Aust. J. Soil
Res. ,* : +*1ῌ+2.
Williams B.G. and Hoey, D. (+321) : The use of electromagnetic induction to detect the spatial
variability of the salt and clay contents ofsoils. Australian Journal of Soil Research. ,/ :,+ῌ,1.
Williams, B.G. and Arunin, S. (+33*) : Inferring recharge/discharge areas from multifrequency
electromagnetic induction method. Technical
Memorandum 3*/++. CSIRO.
Williamson D.R., Turner, J.V., Peck, A. J. andArunin, S. (+323) : Groundwater hydrology andsalinity in a valley in Northeast Thailand. In
Groundwater Contamination. IAHS. Pub. No.
+2/.
Yamclee, P., Dissataporn, C., Pongwichian, P. andArunin, S. (+330) : Prediction of groundwatersalinity by geonic technique. Soil and Water
Conservation Journal. 0 : ./ῌ/0.

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