Advances in Environmental Biology

Advances in Environmental Biology, 8(13) August 2014, Pages: 960-965
AENSI Journals
Advances in Environmental Biology
ISSN-1995-0756
EISSN-1998-1066
Journal home page: http://www.aensiweb.com/AEB/
Studying the effect of Leaching on the Reduction of Salt and Sodium in the Saline
Sodic Soil of Ramshir, Khuzestan (Iran)
Mansoor Shabani, Kamran Mohsenifar, Ebrahim Panahpoor
Department Of Soil Science, College Agriculture, Khouzestan Science and Research Branch, Islamic Azad University, Ahvaz, Iran
ARTICLE INFO
Article history:
Received 3 August 2014
Received in revised form
27 September 2014
Accepted 24 October 2014
Available online 3 November 2014
Keywords:
Ramshir, Salt, Leaching, EC and
Empirical model
ABSTRACT
Due to its geographical status, Iran is located in an area of the earth where most zones
are arid and semi-arid. Hence, soil salinity is natural in such conditions. Leaching is the
only way to reduce soil salt. Yet, with respect to the aridness of the area, water
deficiency as well as the risk of sodium spread in soil, a scientific method is necessary
to estimate required water. This study estimates the water required for leaching and
reducing salt and sodium levels in Ramshir soil. Accordingly, 12 plots (3 replicates and
4 depths of irrigation water) of 1m2 were leached in four stages (25cm in each) and
sampled. The Electrical Conductivity (EC) and Exchangeable Sodium Percentage
(ESP) in soil were measured. And, the percentage of leached slat was calculated. Using
SPSS software and examining different empirical models, the best model with
maximum coefficient of determination was selected by for leaching the soil of the area.
Results indicated that adding average 100cm water to soil, electrical conductivity was
reduced from an average 27.03 to 16.93dS/m.
© 2014 AENSI Publisher All rights reserved.
To Cite This Article: Mansoor Shabani, Kamran Mohsenifar, Ebrahim Panahpoor, Studying the effect of Leaching on the Reduction of Salt
and Sodium in the Saline Sodic Soil of Ramshir, Khuzestan (Iran). Adv. Environ. Biol., 8(13), 960-965, 2014
INTRODUCTION
Soil is the major foundation of civilization for every country. In fact, soil is the vital material without which
human being cannot live. A hundred million humans’ life is directly related to soil and agriculture. And, soil is
the only element of living [1].
In saline and (or) saline sodium soils, due to the increase of soluble salts densities in soil profile, water
absorption by plant root done based on osmosis phenomenon is disrupted. And, it hinders and stops plants’
growth. Besides, some ions existing in the saturated extract of soil (e.g. sodium, chlorine, and bromine) result in
especial plant poisonings [2].
In most cases, the increase of soluble salts density in the saturated extract of soil accompanies the increase
of exchangeable sodium ion (Exchangeable Na+) in the exchangeable soil complex. The adverse effects of
exchangeable sodium on plants growth can be attributed to factors such as plant poisonings, lack of nutritive
balance in plants, and the increase of soil reaction level (pH) [2].
Due to its geographical status, Iran is located in an area of the earth where most zones are arid and semiarid. In this country, evaporation level in some areas is 8 times their precipitation level [3].
Raj and Nath (1980) reported that the leaching of soluble salts is basically done by mass flow. They
concluded that one unit volume of water is adequate for leaching a great deal (%90) of soluble salts from soil
profile. Concerning the determination of water required for leaching soluble salts from soils profiles [4].
Rio (1957), Dileman (1963), Hoffman (1980), Pazira and Kawachi (1981), and Verma and Gupta (1989)
presented a variety of empirical models with the mathematical equations of hyperbolic and exponential
functions. Each of these equations is determined based on soil texture, initial salinity, and the condition of the
place where leaching experiments were conducted. In addition to Rio (1957) equation, intermittent flooding
method was applied to set the equations (derivation of Pazira) [5].
To estimate the water volume required for leaching soluble salts in southeast saline and sodium lands of
Khuzestan Province, Pazira and Keshavarz (1997) presented empirical (exponential) model. To study the
feasibility of leaching soluble salts from soils profiles in south Khuzestan Province [5].
Mohsenifar et al (2006) presented reverse empirical model. They reported appropriate correlation between
theoretical and empirical number [6].
Corresponding Author: Kamran Mohsenifar. Department Of Soil Science, College Agriculture, Khouzestan Science and
Research Branch, Islamic Azad University, Ahvaz, Iran.
Tel: 989133857322 E-mail: [email protected].
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Advances in Environmental Biology, 8(13) August 2014, Pages: 960-965
Comparing between two leaching methods in saline and sodium soils of Roudasht in Isfahan and in his
experimental condition, Mohammadi (1992) concluded that intermittent leaching is more effective in leaching
salt [7].
Determining water required for leaching soluble salts from soils profiles, Rajabzadeh et al (2011) selected
exponential model as the appropriate model [8].
Soils of the area under study are considered among the arid areas soils. They are saline and sodium soils As
a result, leaching is one of the major methods for controlling soluble salts in these soils [9]. Leaching can be
done by circumscribing the land and placing considerable depth of water on soil. Then, soluble salts existing in
soil interface will move deeper into soil. Regarding the shallow water flow in arid and semiarid areas, the
volume of water required for reducing salts is significant. And, it is required to present a quantitative equation.
Idris AĞAR, A. (2011), reclaimed saline and sodic soil by using divided doses of phosphogypsum in
cultivated condition. The results showed that required depth of leaching water is approximately 2.3 times of soil
depth to be reclaimed, for leaching 50% of the soluble salt from the soil profile. the relationship between the
ratio of depth of leaching water (Dlw) to soil depth (Ds) and the final soil salinity (C) to initial soil salinity (Co)
was found, the equation is given as follow; [10]
C
0.036 100
DLW
C0
 12.79e
DS
R2=0.74
C
Where ( C ) is Percentage of initial salt remaining in the soil profile to depth of leaching water and (
0
DLW
)
DS
is applied per unit depth of soil.
And Exchangeable sodium removal equations as follows:
PGap  7.078e 0.196GRT
R2=0.827
Where PGap is applied amount of phosphogypsum and GRT is calculated theoretical gypsum.
Cucci G. and et al. (2013) investigated the effect of irrigation with saline and sodic water. He reported did
not show any significant effect of irrigation water’s salinity and sodicity, and of the leaching fraction, on soil
type. The use of irrigation water with 0.1 M salt concentration caused an increase in (ECe) from an initial
average value of 0.71 dS/m-1 to 13.9 and 19.5 dS/ m-1, at the end of the first and the second irrigation season,
respectively [11].
This study conducts field experiments in Ramshir, Khuzestan to reduce the salinity and sodium level of soil,
draw leaching curve for the area, and present an appropriate model for desalinating soil.
MATERIALS AND METHODS
The area under study (22000 hectare) was located in southeast Khuzestan Province and in Ramshir between
E25′:49 to 23′:49 and N53′:30 to 56′:30 . Regarding weather, the area was classified as sub-desertic climate
with hot, long, and dry summers and short and temperate winters. Jarahi River was the only source of water in
this area [12].
A part of Sen Village lands in Ramshir was selected. This experiment was conducted with strong drifts in
four stages and three replicates. Besides, to estimate the level of salt before leaching, a plot was considered as
control and sampled without adding water.
In the first stage, 250 liter (25cm) water was added to each plot. Then, one plot was randomly selected
among each replicate. And, after gravity water withdrawal, samples were prepared from 0-25, 25-50, 50-75, and
75-100cm depths using soil auger (Figure 1). Sampled plots were omitted from the experiment. And, another
250 liter was added to the remaining ones. After gravity water withdrawal from each replicate, sampling was
randomly done from 0-25, 25-50, 50-75, and 75-100cm depths. Similarly, leaching was carried out down into
100cm depth. Samples were prepared and submitted to laboratory for the calculation of EC and SAR after being
dried in the air.
To examine the effect of leaching on different depths of water, SPSS was applied. The ratio of leaching
water (DLW) to depth of soil (DS) as X (independent variable) and the difference between final EC (ECf) and
equilibrium EC (ECeq) to the difference between initial EC (ECi) and ECeq (
EC f -EC eq
EC i  EC eq
) as Y (dependent
variable) were entered into SPSS Software. Then, the efficiency of empirical model was extracted by the
software.
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Advances in Environmental Biology, 8(13) August 2014, Pages: 960-965
Dw=
25+25cm
Dw=25cm
Dw=25+
Dw=
25+25+25cm 25+25+25cm
Dw=
Dw=25cm
25+25+25cm
Dw=
25+25cm
Dw=25+
25+25+25cm
Dw=25+
Dw=
25+25+25cm 25+25cm
Dw=
Dw=25cm
25+25+25cm
Fig. 1: plots arrangement.
RESULTS AND DISCUSSIONS
The physical characteristics of four layers of soil, soil texture, and the depth of water required for supplying
the water deficiency, electrical conductivity, and exchangeable sodium percentage were calculated (Table 1). As
seen in Table 1, soil texture down into 75cm depth is loam and sandy loam between 75cm and 100cm.
Before leaching, maximum EC is related to 0-25cm depth (48.6 dS/m). Average soil salt was reduced to
8.95 dS/m after leaching.
Table 1: The physical characteristics of different layers of soil and depth of water required for supplying the water deficiency of different
soil layers in the study area.
Row
layer (cm)
Depth (cm)
Soil Texture
Soil Water
ECi (dS/m)
SARi (Before
content (cm)
Before leaching
leaching)
1
0-25
25
L
0.5
46.8
38
2
25-50
25
L
4.14
20.8
25.2
3
50-75
25
L
4
17.4
23.9
4
75-100
25
SL
3
23.1
26.2
EC and SAR of leaching water were respectively gained 3.08ds/m and 5.2 (Table 2).
Table 2: Quality of leaching water.
Sampling date
Day
Month
13
12
Year
2012
EC( )
3.08
pH
SAR
8
5.2
Down into 100cm depth and after leaching via adding 100cm leaching water, EC was reduced from an
average 27.03 to 16.93 dS/m. Exchangeable Sodium was also reduced from 28.33 to 21.89 (Figures 2, 3 ).
As shown in Figure 2, salt accumulation was in the soil surface before leaching. Salt accumulation
transported to 25-50 cm and up to 100 cm in soil, after adding 25 cm and 100 cm water, respectively.
Fig. 2: EC in different depths of leaching water.
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Kamran Mohsenifar et al, 2014
Advances in Environmental Biology, 8(13) August 2014, Pages: 960-965
Before leaching, sodium accumulation was in soil surface, so sodium accumulation transported to 25-50 cm
and up to 100 cm in soil, when 25 cm and 100 cm water were added, respectively (Figures 3).
Fig. 3: The ESP in various depths of leaching water.
The average percentage of salt and sodium leached by 100cm leaching water was calculated for 100cm of
soil.
Upon leaching, the percentage of salt and sodium leached down into 100cm of soil indicated decreasing
trend. That is, %22.73 and %37.35 respectively remained for salt and sodium (Figure 4). It is opposite of the
results reported by Idris AĞAR, A. (for leaching 50% of the salt, required 2.3 times of soil profile depth)
Fig. 4: The average percentage of salt and sodium leached by 100cm leaching water.
Regarding the deficiency of water in each layer, the leaching water was determined. Due to the lack of
humidity in 100cm depth, 11.64cm of 100cm water was applied to remove the shortage. Practically, 88.36cm
was also used for leaching salt.
By omitting the water deficiency of each layer of soil, the net value for different depths of leaching water
(DLW) was calculated (Figure 5).
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Advances in Environmental Biology, 8(13) August 2014, Pages: 960-965
Fig. 5: Different layers of water deficiency in cumulative and leaching water depth for different depths of
irrigation water
The equilibrium of soil EC was gained 7.6dS/m. That is, regarding the EC of leaching water (3.08), it is
impossible to reduce soil salinity further.
To develop the optimum empirical model, SPSS was applied. The ratio of net depth of leaching water
(DLW) to depth of soil (DS) as X (independent variable) and the difference between ECf and ECeq to the
EC -ECeq
f
difference between ECi and ECeq (
) as Y (dependent variable) were entered into SPSS software.
ECi  ECeq
The optimum model was gained by the coefficient of determination 0.856 of quadratic model (Equation 1).
Similarly, for ESP, the optimum model was set by the coefficient of determination 0.846 of quadratic model. It
is in accordance with the results reported by Mohsenifar et al (2006). Yt, Rajabzadeh et al (2011) introduced the
exponential model as the appropriate model (Equation 2).
Equation 1
Equation 2
Suggestions:
To leach salt, it is required to determine the depth under modification and add the same amount of water to
soil. Here, it was seen that - at the same time of using 100cm water applied to leach salt – sodium was also
leached. Then, there is no risk of spreading sodium in lands. Hence, it is not required to use materials modifying
and improving soil. It is suggested that – although there is no risk of sodium spread in soil under study – this
experiment be replicated by different modifying materials (lime, gypsum, sulfuric acid, sulfur and …). It is also
proposed that the experiment be carried out in other areas with different salinities and acidities.
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