IJERD – International Journal of Environmental and Rural Development (2013) 4-2

Research article
erd

Chemical Properties of Soils in Reforested and Bare Areas
in Salt Affected Area of Khon Kaen Province, Thailand
JEERANUCH SAKKHAMDUANG
Graduate School of Agriculture, Tokyo University of Agriculture, Tokyo, Japan /Recearch Center, Institute of Environment Rehabilitation and Conservation, Tokyo, Japan

MACHITO MIHARA*
Faculty of Regional Environment Science, Tokyo University of Agriculture, Tokyo, Japan
Email: m-mihara@nodai.ac.jp
Received 21 December 2012

Accepted 30 January 2013(*Corresponding Author)

Abstract Salt affected soil is a severe environmental problem in northeast of Thailand.
About 16.82 percent of the total land area in the region is accounted for the salt affected
area. In the study area of Phra Yun district, Khon Khaen province, there were manystudies since 1990 and 18 governmental projects of Thailand have been conducted forrehabilitating salt affected soil since 1999. However, attention has been paid to the current
condition of salt accumulation in Phra Yun district, after many studies and projects havebeen implemented. So in this study, soil survey was conducted in four areas, Eucalyptus(Eucalyptus camaldulensis) reforested area and adjacent bare area, Acacia (Acacia
ampliceps) reforested area and adjacent bare area. Disturbed and undisturbed soil samples
were collected for analyzing physical and chemical properties of soils. The differences inchemical properties of soils were analyzed by t-test statistical method. The results showedthat EC1:5 values of soils in reforested and adjacent bare areas were significantly different
at 99%. The sodium and calcium concentration of soils at the same depth in reforested andadjacent bare areas also showed significant different at 95% and 99%. Moreover, there
was a tendency that EC1:5 values, sodium and calcium concentration decreased with soil
depth due to accumulation of salts at the surface layers. Although many studies andprojects have been implemented in Phra Yun district, salt accumulation has been stillsevere, especially in bare areas. In addition, it was clearly observed that reforested areas of
Eucalyptus and Acacia tended to be lower in electrical conductivity, sodium and calcium
concentration than that of adjacent bare areas. Thus, it was concluded that reforestation isan effective approach to rehabilitate salt affected soil.
Keywords salt affected soil, reforested areas, chemical properties of soil

INTRODUCTION
Salt affected soil is a severe environmental problem in northeast of Thailand. Total area of thisregion is 16.928 million hectares while the salt affected land covers 2.848 million hectares or about
16.82%. From the rock salt stratum, called Mahasarakam formation, laid under soil surface at 100
m to 200 m deep, salt components are rising associated with soil water to ground surface. Salt
affected soil is not only an environmental problem but also economic and social problems in rural
areas.
Capillary rise of saline groundwater is one of the main causes of salinization (Kohyama andSubhasaram, 1993). One of the practices to prevent salinization is interrupting capillary rise of
saline groundwater (Mihara et al., 2009) and to control the saline groundwater level (Dissataporn etal., 2002). Among several practices for controlling saline groundwater level, reforestation is also
recommended to lower saline groundwater and mitigate salt accumulation (Yamklee et al., 1995
and Yuwaniyama, 2011).
Khon Kaen province is one of the provinces in northeast of Thailand that faces salt affectedsoil problem. The salt affected area covers around 10.85 percent of total area. Salt affected soil

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problem is severe in Phra Yun district, Muang district, Ban Fang district and Ban Phai district(Khon Kaen province, 2005; Topark-ngarm, 2006).
Phra Yun district is one of the salt affected areas of Khon Kaen province. Agriculture is themain occupation of villagers in the district, paddy rice and sugarcane are the main agricultural
products. Topography of this area ranges from flat land to rolling hills, elevation varies from 175 to
190 m above sea level. Paddy rice was cultivated in lowland areas while in the hill areas villagers
grown sugarcane, cassava and Eucalyptus trees. Average income of population in Phra Yun district
is 58,673 Baht or around 1,884 USD per year (Phra Yun Community Development Office, 2012).
In the study area, there were many studies about causes, effects and distribution of salt
affected soil since 1991 (JICA, 1991). Besides that, 18 governmental projects of Thailand havebeen conducted for rehabilitating salt affected soil since 1999 (Land Development Department,
1999, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, Land Development Office of Region 5(Khon Kaen), 2000, 2010, 2011a and 2011b).
Main activities of government projects for suppressing and/or ameliorating salt affected soil
problem in the study area included; introducing salt tolerant rice species to farmers, increasing riceproductivity by organic fertilizer and green manure application. Making groundwater drainage
system, promoting salt tolerant tree included Eucalyptus camaldulensis and Acacia ampliceps andhalophyte grass, Sporobolus virginicus in severely salt affected areas as well as planting fast
growing trees in recharge areas to prevent salinization.
Moreover, in 1985, Agricultural Development Research Center (ADRC) has established incooperated with Japan International Cooperation Agency (JICA), Thai Government and Khon
Kaen University (JADES, 1997). The aims of the center are: 1) classification of agro-ecologicalzones and land use planning, 2) development of farm management system and 3) development of
low-input technology. One of the activities of ADRC was to suppress salinization and ameliorate
the salt affected areas.
However, attention has been paid to the current condition of salt accumulation in Phra Yun
district, after many studies and several projects have been implemented. Therefore, the objective of
this study is to investigate chemical properties of soils in reforested and bare areas in salt affectedarea of Khon Kaen Province, Thailand.
METHODOLOGY

Acacia area

Bare area

Eucalyptus area

Bare area

Fig. 1 Areas of conducted soil profile survey and collected soil samples
In January 2012, soil profile survey was conducted in 4 areas, Eucalyptus (Eucalyptus
camaldulensis) reforested area and adjacent bare area, Acacia (Acacia ampliceps) reforested area

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IJERD – International Journal of Environmental and Rural Development (2013) 4-2

and adjacent bare area. According to soil profile in Eucalyptus reforested area, 3 disturbed and 9
undisturbed soil samples were collected while from the adjacent bare area of Eucalyptus, 5
disturbed and 15 undisturbed soil samples were collected. In Acacia reforested area, 2 disturbed
and 6 undisturbed soil samples were collected while from the adjacent bare area of Acacia, 3
disturbed and 9 undisturbed soil samples were collected. Soil samples were analyzed for physicaland chemical properties. The physical properties of soils including soil texture, dry density, specificgravity and soil permeability were analyzed. In addition, soil chemical properties including pH,
electrical conductivity (EC1:5) value, sodium, calcium, total nitrogen and total phosphorus
concentration were analyzed. The differences in chemical properties of soils were analyzed by ttest statistical method.
RESULTS AND DISCUSSION
Physical properties of soils in reforested and bare areas
The soil textural classes of soils from 4 study sites were sand, sandy loam and loamy sand. Soils
specific gravity ranges between 2.62 to 2.66. Dry density of soils in 4 study sites ranges from 1.54
to 1.80 g/cm3. The highest percentage of loss on ignition was found in topsoil of Acacia reforested
area 3.63% (Tables 1 and 2).

a Eucalyptus reforested area b bare area adjacent to
Eucalyptus

c Acacia reforested aread bare area adjacent to
AcaciaFig. 2 Soil profiles in 4 areas
Table 1 Physical properties of soils in Eucalyptus reforested area and adjacent bare area
Depth fromsoil surface
Horizon(cm)
Soil in Eucalyptus area
0 – 40A1
40 – 45
A2

Soil texture

Specific
gravityDry density(g/cm3)

Ignition loss (%)

Saturated
permeability(x10-3 cm/s)

S
LS

2.62
2.65

1.80
1.79

0.89
0.67

125.90145.1045 – 100
A3
LS
Soil in bare area adjacent to Eucalyptus area
0 – 10
Dress layer 1
L
10 – 25
Dress layer 2S
25 – 34
Dress layer 3
LS
34 – 44A1LS
44 – 100
A2
SL

2.64

1.78

0.47

127.60

2.64
2.64
2.62
2.65
2.66

1.54
1.67
1.56
1.62
1.62

3.59
0.68
1.24
1.2
1.37

0.10
133.700.50
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IJERD – International Journal of Environmental and Rural Development (2013) 4-2

Table 2 Physical properties of soils in Acacia reforested area and adjacent bare area
Depth fromsoil surface
Horizon
Soil texture(cm)
Soil in Acacia area
0 – 10A1
S
21 – 80
A2
S
Soil in bare area adjacent to Acacia area
0 – 15A1LS
15 – 22A2LS
22 – 70A3
LSSpecific
gravityDry density(g/cm3)

Ignitionloss (%)

Saturated
permeability(x10-3 cm/s)

2.64
2.65

1.58
1.62

1.04
1.35

134.20
51.20

2.64
2.66
2.63

1.63
1.64
1.63

3.63
1.33
1.02

41.90
122.4095.90

Chemical properties of soils in reforested and bare areas
As shown in Fig 3, the EC1:5 values of soils in 4 areas were significantly different at 99%. The
EC1:5 value in topsoil of Eucalyptus reforested area was the lowest at 0.01985 mS/cm and thehighest value was topsoil of bare area adjacent to Eucalyptus at 20.00 mS/cm.
EC (mS/cm)
0

10

20

30

0
10 A**

a**

b**

B**

20
30

a

Depth (cm)

a

40
50

A**

Eucalyptus area

B**

Bare area adjacent to
Eucalyptus area

60

Acacia area

70
Bare area adjacent to
Acacia area

B**

80

A**

**Significant differnce at 99%

90

Fig. 3 Electrical conductivity values (EC1:5) of soils in 4 areas
The sodium and calcium concentration of soils at same depth in 4 areas showed significant
difference at 95% and 99%. It was observed that sodium concentration was the lowest in topsoil of
Eucalyptus reforested area at 1.84 mg/kg and the highest concentration was topsoil of bare areaadjacent to Eucalyptus at 21,447.86 mg/kg (Fig. 4, left side).
Calcium concentration was the lowest in topsoil of Eucalyptus reforested area at 10.10 mg/kg
and the highest concentration was topsoil of bare area adjacent to Acacia at 1,926.84 mg/kg (Fig 4,
right side). Moreover, there was a tendency that the EC1:5 values, sodium and calcium
concentration decreased with depth due to accumulation of salts at the surface layers.
As shown in Fig. 5 (left side), the total nitrogen concentration of soils in 4 areas was
significantly different at either 95% or 99%. A significant difference at 95% in the total nitrogenconcentration were found in soil of 2nd layer and 3rd layer of Eucalyptus area and adjacent bare area,
while a significant difference at 99% were found in topsoil of Acacia area and bare area adjacent to
Acacia. The highest total nitrogen concentration at 522.89 mg/kg was found in Acacia reforested
area due to high amount of nitrogen in Acacia leaf litter. Low total nitrogen concentration in topsoilof Eucalyptus plantation might be due to allelopathic affect of Eucalyptus trees to soil
macronutrients (Tilashwork, 2009).

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IJERD – International Journal of Environmental and Rural Development (2013) 4-2

Sodium concentration (mg/kg)
0

0

10000

A**

20000

Calcium concentration (mg/kg)

30000

0

10

20

20
30

1500

2000

B** b**aa aaDepth (cm)

40

1000

A** a**

B**

a* b*

10

30

Depth (cm)

500

0

B**
A**

50

Eucalyptus area

40

B**
A**

Bare area adjacent to
Eucalyptus

50

Acacia

60

60

70

70

Bare area adjacent to
Acacia
B**

B**

80

80

A**

A**

*Significant difference at 95%**Significant difference at 99%

90

90

Fig. 4 Sodium concentration (left) and calcium concentration of soils (right) in 4 areas
The total phosphorus concentration of topsoil of Acacia area was significantly different at
95% from that of adjacent bare area. The total phosphorus concentration found in 4 areas was
relatively low ranging from 0.67 to 6.64 (Fig.5, right side). From the result, the highest value of
total phosphorus was found in the bare area adjacent to Eucalyptus area, the possibility isfrequently burning residues in bare area might be increase total phosphorus in soil (Li et al., 2012).
Total nitrogen concentration (mg/kg)
0

200

400

Total phosphorus concentration (mg/kg)

600

0

0
b**

A

0

a**

A

10

10

20

20

2

a*

4

6

8

b*

Eucalyptus

40

a

30
a
B**

Depth (cm)Depth (cm)

30

A**

50

80

50
60

60
70

Bare areaadjacent to
Eucalyptus
Acacia40

Bare areaadjacent to
Acacia

70
B**

80

A**

**Significant difference at 99%*Significant difference at 95%

90

90

Fig. 5 Total nitrogen concentration (left) and total phosphorus concentration (right) of soils
in 4 areas
Table 3 Changes in salt affected areas in Phra Yun district, Khon Kaen province

Year

1991
2003

Severely affectedarea(salt crust cover
more than 50%)
(ha)
310
441.6

Strongly affectedarea(salt crust cover
10- 50%)
(ha)
1,480
1,404

Moderately
affected area
(salt crust cover1- 10%)
(ha)
3,550
4,250

Source; JICA (1991); REO 10 (2003)© ISERD
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Total salt
affectedarea (ha)% of total
area(17,200
ha)

5,340
6,095

31
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IJERD – International Journal of Environmental and Rural Development (2013) 4-2

Although 18 development projects of Thai government has been conducting in the study area
since 1991, the results of this chapter revealed that the soil salinity still severe, especially in barearea. Moreover, the salt affected areas are increasing from 31 percent of total district area in 1991
to 35 percent in 2003 (Table 3-3).
Strategy for promoting reforestation in salt affected area
Based on the results of this study, it was supported that reforestation is an efficient way torehabilitate salt affected soil. However, low economic benefit with reforestation became theconstraint for the locals to grow more trees in salt affected area of Khon Kaen province, Thailand(Sakkhamduang et al., 2012).
In 2001, Sakkhamduang et al. report that agro-forestry system in Salt affected area in Khon
Kaen Province had a lower practice than that of in non-salt affected area according to the salt
affected soil condition. Agro-forestry practices on salt affected area can be categorized into five
types; patch forests, trees on paddy bunds, tree plantations associated with animal husbandry, homegardens and trees in vegetable gardens. Moreover, Im-Erb et al. (2004) reported that an agroforestry system being promoted on 2003 in recharge area of Nakhon Ratchasima province was well
accepted by farmers according to their additional income.
Thus, agro-forestry system that combined salt tolerant tree with salt tolerant or halophyte
vegetables or field crops should be introduced to farmers in the study area for increasing theirincome as well as rehabilitating salt affected soil.
20m

20m

0

20m

0

20m

Fig. 6 Cross section and top views of home garden, one of agro-forestry systems existing insalt affected area
CONCLUSION
Many government projects have been implemented in Phra Yun district since 1991. The activity of
those projects included; introducing salt tolerant rice species to farmers, increasing riceproductivity by organic fertilizer and green manure application. Making groundwater drainage
system, promoting salt tolerant tree included Eucalyptus camaldulensis and Acacia amplicep andhalophyte grass, Sporobolus virginicus in severely salt affected areas as well as to planting fast
growing trees in recharge areas for preventing salinization.
Although several projects were implemented, salt accumulation is still severe; especially inbare areas that has EC value of 20 mS/cm. In addition, it was clearly observed that reforested areasof Eucalyptus and Acacia tended to be lower in electrical conductivity, sodium and calcium
concentration than that of adjacent bare areas. Moreover, Thaweethavornsawat (1999) reported thatthe decreasing of forest area in Phra Yun district increases the distribution of salt patches in thearea. Thus, it was concluded that reforestation is an effective approach to rehabilitate salt affectedsoil.

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ACKNOWLEDGEMENTS
The authors would like to extend the gratitude to the villagers in the study area for their great
support during the field study as well as to ERECON, Institute of Environment Rehabilitation andConservation, Japan for providing the scholarship of my Ph.D research in TUA, Tokyo Universityof Agriculture, Japan.
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