Geological Approache “Saline Soil Area Development in the Northeast”

Saline Soil Area Development
in the Northeast:

Geological approaches

2

THE ROYAL GRACE OF

On August 9th 2007, His Majesty the King granted an audience to the
executives of the Department of Mineral Resources (DMR) to inform about the
geological situation and present geological maps of Thailand. His Majesty the King
gave an initiative to the DMR executives to conduct a geological research study in
the Northeastern part of Thailand to determine the causes of the area’s saline soil
and propose a proper solution to the problem present.
In response to the King’s advice and initiative, the DMR has set up a project
called “Saline Soil Area Development in the Northeast”. A small saline affected area
located within Nam Un watershed, Sakon Nakhon Province has been selected as
the first study area.

The project employs three main strategies to sort out three different
problems, which are: geological, agricultural and communal. The strategies
include the study on the origins of the saline soil and causes of salt dispersion in
the area; soil quality improvement methods; and selecting salt tolerant plants and
rice strains for use in affected areas.
The Saline Soil Development Learning Center has been set up at Tambon
Haiyong, Phangkhon District, Sakon Nakhon Province. Here, the development
model from the study is passed on to groups of farmers to further test and distribute
the proposed solutions to the community to be applied in other affected areas.

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HIS MAJESTY THE KING

The Royal words on 9th August 2007

“…A hazard has recently occurred in the Northeastern areas; rain
water eroded down to the deeper soils and caused saline soil in many rice
paddy fields. As I noticed such problems, the Land Development Department
and other departments must integrate to solve this problem because this
hazard did indeed occur. This level of salinity is serious and is very harmful
to plants…”

“…The level of salinity in the salt affected soil at Khao Tao pineapple
farm is getting higher after every crop. The foot hill of Khao Tao is covered
with alkaline soil, transported from surrounding hills, my suggestion to solve
this problem is to move the alkaline soil up to the top…”

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What Are Saline Soils?

Saline soils are soils containing high concentration of soluble salts which
obstruct the growth of plants. Excessive salt damages plants by disrupting their
intake of water and interferes with the absorption of nutrients. The table below
shows the 5 classes of generally recognized saline soils and the effect on crops.

Very strongly Only a few very tolerant crops
saline yield satisfactorily

Conductivity (dS/m)16 0.8 Salt Concentration (%)

Strongly saline Only tolerant crops yield satisfactorily

8 0.4
0.2
Moderately saline Yields of many crops are restricted 0.1

4 Slightly saline Yields of sensitive crops may be restricted
2 Non saline Salinity effects negligible

Many provinces in the Northeastern part of Thailand (Isan) have been
affected by saline soils which are caused mainly by dissolved sodium chloride
from deep seated rock salt. During every dry season salt is interspersed on the
lowland ground surface and it is leached away in the rainy season. The soil salinity
has rapidly dispersed and has lowered the quality of life for many people; causing
many economical, social and environmental problems.

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What to Do With Saline Soils?

In February 2008, the DMR launched the project called “Saline Soil Area
Development in the Northeast” to study the causes and solve these soil salinity
problems.The Integration of geological, agricultural and the communal strategies
among participating offices and organizations are vital to the success of the
project. The organizations involved are as follows: Office of Natural Resources
and Environment, Sakon Nakhon Province; Rice Department; Department of
Groundwater Resources; Pimai Salt Co., Ltd.; National Science and Technology
Development Agency (NSTDA); Land Development Department, etc.

The geological work that has been prepared is effective in creating a
strong foundation for our continuing work due to its useful application in various
exploration techniques including geological, geophysical and geochemical surveys
on the saline soil project. The study of rice selection in particular has yielded great
success. The success of our demonstration rice field, along with the participation
of the people, has resulted in an Action Plan for the entire Haiyong Community.

Salinity in the salt affected study area Gravity lows delineate salt domes

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The Saline Affected Areas

The Khorat Plateau covers one third of the country. Twenty nine percent of
the Northeastern part, about 30.4 million Rais*, is mapped as saline soil terrains
with 3 degrees of salinity.

(*1 Rai covers an area of 40x40 square meters)
1. Strongly saline terrain

covers 1.4 million Rais of salt surface ground.
2. Moderately saline terrain

covers 5.7 million Rais of scattered salt surface ground.
3. Slightly saline terrain

covers 23.3 million Rais of some scattered salt surfaced ground

Non-saline terrain, slightly saline terrain,
75.6 Million Rais 23.3 Million Rais

Saline terrain,
30.4 Million Rais

moderately strongly
saline terrain, saline terrain,
5.7 Million Rais 1.4 Million Rais

There are fifteen provinces affected by the salinity as follows: Udon Thani,
Sakon Nakhon, Nakhon Phanom, Khon Kaen, Kalasin, Chaiyaphum, Maha
Sarakham, Roi Et, Yasothon, Amnat Charoen, Nakhon Ratchasima, Buri Ram,
Surin, Si Sa Ket, and Ubon Ratchathani.

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Strongly Saline
Moderately Saline

Sakon Nakhon Basin

Udon Thani Sakon Nakhon
Khon Kaen Nakhon Phanom

Kalasin

Chaiyaphum Khorat Basin Roi Et
Yasothon
Maha Sarakham
Amnat Charoen

Buri Ram Surin Ubon Ratchathani
Si Sa Ket

Nakhon Ratchasima

The strongly and moderately saline terrains covering fifteen provinces of Isan are
located over the two sedimentary basins of the Khorat plateau

Saline soil is caused naturally by rock salts that are dissolved by the
groundwater and dispersed in the lowland where the groundwater table is very
shallow. One serious, but avoidable, cause of the saline soil crisis is deforestation.
The forest stabilizes groundwater table and simultaneously humidifies the
atmosphere by absorbing groundwater via the roots and evaporating it through the
leaves. Without the forest, groundwater table will rise up close to the ground surface
and the air will be dry. These conditions are suitable for saline soil occurrences.

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The Khorat Plateau and the

Under the Khorat Plateau lay various clastic sedimentary rocks of the
Khorat group including conglomerate, sandstone, siltstone, shale and mudstone.
Since the Mesozoic Era (251-65 million years ago), these sediments have been
continuously deposited into a continental basin under an arid to semi-arid climate.
At the end of the Era, after the seawater transgression dried out by the
aridity, rock salt beds hundreds of meters thick were left behind. The rock salt was
finally covered with very fine grained sediments transported by wind and water.
The uplifting of the Khorat Plateau caused deformations and fractures in the
rock sequence. Under great load pressure, the rigid rock salt behaves as a plastic
body and flows upward through weak zones in the upper rock units to form salt
domes. The fractured cap rocks can easily collapse when the top of the salt domes
are leached by groundwater. Nowadays, many reservoirs spread throughout the
Khorat plateau indicate the shallow buried salt domes.

Forest Humid air

Fault Salt dome Groundwater table

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Hidden Gigantic Rock Salt

The cause, the shortcuts and the catalyst

The northeastern saline soil is caused mostly by rock salt being dissolved

and dispersed by groundwater. However, the saline soil would not have spread

widely over the plateau without the necessary shortcuts and

catalyst. The salt domes act as shortcuts

allowing the source of the salt to Capillary zone
move closer to the surface, while

the faults act as pathways for

upward movement of the saline Fractures Groundwater table
groundwater.
Salt dome
After the groundwater

dissolves the salt domes, the

catalyst to the saline soil crisis is the

capillary force which pulls the brine up,

against the gravity, to the surface. At this point, pure water

evaporates from the brine and only salt is left behind. This process happens

continuously under dry weather conditions where the groundwater table is

shallower than 4 feet and the top soil is sandy.

Capillary zone

Salt affected terrain

Groundwater table rises up Salt dome

Dry air Deforest

Younger formation Fault
Rock salt formation Older formations

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The Geological Solutions o

The DMR has acted in response to the King’s advice and initiative to help
people in saline soil affected area by cooperating with participatory offices and
organizations to study on the soil quality improvement. Many solutions have been
derived from the intensive study. The solutions are as follows: the use of salt
leaching technique, the use of organic fertilizer, and the selection of salt tolerant
plants and rice types for the area.

The geological investigation by the DMR indicated that the saline soil is
caused by the leakage of saline groundwater. One good solution to this problem
is the salt leaching technique. However, a better solution is to avoid the catalyst of
the crisis by humidify the soil with agricultural materials, e.g. rice-husk, rice-straw
and cover crops.

Further geological study has also identified a method to enhance the
efficiency of saline soil protection by using geological materials found in the vicinity
i.e., bentonite for saline
groundwater trapping
and the clay of Nawa
rock unit for soil structure
improvement.

Bentonite deposits are mostly found in mud seepages

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on the Saline Soil Problems

Bentonite is a combination of clay minerals altered from igneous rocks or
volcanic tuff, e.g. montmorillonite, beidellite, nontronite, saponite and hectorite.
When wet, bentonite absorbs water and forms an impermeable film which
inactivates the capillary force. Bentonite deposits in the northeastern are mostly
found in mud seepages in some provinces, e .g. Chaiyaphum and Sakon Nakhon
Provinces.

The clay of Nawa is a weathering product of mudstone, claystone and shale
of the Nawa rock member which is sitting on top of the rock salt beds. It composes
of kaolinite, montmorillonite and quartz. Nawa clay can prevent the leakage of
plant nutrients from the soil by absorbing water along with essential nutrients into
its molecule’s stacked layers. Nawa clay is found in undulating terrains in some
provinces, e.g. Sakon Nakhon and Khon Kaen Provinces.

Most of the clays found in river banks and in alluvial planes in the farm vicinity
are satisfactory for soil structure improvement.

Typical Nawa clay at Nawa District, Nakhon Phanom Province
The reddish brown Nawa clay is found laying weathered and eroded under the lateritic layer.

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Six Steps to Improve

The results returned from the integrated study of the DMR and alliance
indicated that saline soil in the northeastern is caused by deep seated gigantic rock
salt being dissolved by groundwater. It is then dispersed to the top soil by seeping
through the voids between sediment particles, which is most likely to happen in dry
sandy soil. The most straightforward way of improving saline soil would be to leach
out the salt and prevent its return. In addition, in order to yield better crops, some
integration of agricultural techniques has been proposed.

Salty water is delivered to the prepared pond for tilapia farming

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the Salt Affected Areas

1. POND Prepare a pond to collect saline water from the salt leaching
process. This brackish water is useful for some fish farming, e.g. Nile tilapia and
Mozambique tilapia.

2. SALT LEACH Leach out the salt from the saline soil by flooding the rice
field with water fifteen centimeters high. Keep the field flooded for a few days.
Deliver the water to the prepared pond. Repeat the process 2 - 3 times.

3. CLAY FILL Fill up the rice field with the clay of the Nawa formation and
surrounding areas. To improve the soil structure, use approximately 10 tons of clay
per Rai.

4. BENTONITE SEAL Trap the saline groundwater with an impermeable
film of bentonite (if available). Use approximately 1 ton of bentonite per Rai.

5. NUTRIENT ADD Improve plant nutrients in the soil with natural fertilizer,
organic fertilizer or manure.

6. SALT TOLERANCE PLANT Select saline tolerant plants such as Khao
Dawk Mali 105 or RD6.


* Steps 3-5 can be applied at the same time and then plough together.

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The success of the project “Saline Soil Area Development in the Northeast”
depends greatly on the royal grace, the people participation and the integration
among participatory offices and organizations. The studies of saline soil problems
have resulted in effective geological approaches to lower the salinity of the soil and
protect the land from increasing salinity, as well as saline tolerant plants and an
action plan for the Haiyong Community. These satisfactory results have led to the
improvement of soil quality by six steps and the opening of the Saline soil develop-
ment learning Center

At the learning center, the development model from the study is passed
on to groups of farmers to further experiment and share the results among the
community to be applied in all other saline soil affected areas. The Demonstration
Center for Knowledge Distribution directed by head farmer Khruea Suwanchai-rob
is the experimental farm located at Tambon Haiyong, Phangkhon District, Sakon
Nakhon Province.

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The Steps Forward

Learning Center

3026 55 Km. to Sakon Nakhon

Uncle Khruea Suwanchai-rob and the map to his learning center
The lessons learned from this project have been applied in other salt
affected areas in the northeastern and transferred to related academic hubs
whose aims are to:-
• Distribute the knowledge
• Apply in other affected areas
• Select volunteer farmers to build up administrative farms and
learning centers.

The lessons learned have been transferred to academicians and farmers.

The Department of Mineral Resources
manages geological issues and geological resources

through people's participation
for the benefits and happiness of the whole society.

Published in 2015
Division of Mineral Resources Conservation and Management
Department of Mineral Resources (DMR)
Ministry of Natural Resources and Environment (MONRE)
75/10 Rama VI Road, Ratchathewi, Bangkok 10400
www.dmr.go.th