沙漠研究 22-1, 17 -20 (2012 )"ICAL 1 / DT X"

Journal of Arid Land Studies－Refereed Paper－

Phytodesalination of a Salt-Affected Soil with Four Halophytes in China
Yuji SAKAI*1), Yuanyuan MA 2), Chi XU2), Haiyan WU2), Wenbi ZHU2) and Jinhui YANG2)
Abstract: In arid and semiarid regions of China, the decrease in agricultural production due to excessive salts is a very serious
problem. Salt-affected soil distributes mainly at north, west, around Bohai Sea, and the mid-stream of the Yellow River. We could
have ameliorated salt-affected soil such as alkali soil, saline-alkali soil by using flue gas desulfurization gypsums. Consequently, theeffectiveness of these desulfurization by-products as soil amendments could be confirmed. However, soil containing much salt suchas sodium chloride spreads widely in Tianjin city around Bohai Sea. In order to ameliorate this soil, it is necessary to remove muchsalt in soil at first. Phytodesalination refers to the use of halophytes to remove sodium from the soil. This plant-based method is ofgreat importance especially for several developing countries. In this research, treatments by four halophytes, Artemisia argyi L.,
Limonium bicolor K., Melilotus suaveolens L., and Salsola collina P. were tested in pot experiment by using three salt-affected soils(Dagang district, Xiqing district and Jixiang county) in Tianjin. Soil properties were evaluated by pH, EC, ESP (exchangeablesodium percentage) and ions concentration (Na, Ca, Mg, Cl, HCO3, CO3 and SO4) before and after plant growing. Consequently, Naand Cl concentrations and EC at all test pot decreased after the growth of halophytes, and Na concentration in two halophytes
increased. Moreover, we could propose the new soil amelioration method to add desulfurization gypsum to soil after
phytodesalinization because of both high pH and high ESP after treatment.
Key Words: Electrical conductivity, Halophyte, pH, phytodesalination, Salt-affected soil

1. Introduction
1.1. Soil problems in China
Soil salinity is a widespread environmental problem,
particularly in arid and semi-arid regions of the world. Thisproblem affects crop production on over 800 million hectares,
or a quarter to a third of all agricultural land on earth (Szabolcs,1989; Rengasamy, 2010). Salt-affected soils occur within theboundaries of at least 75 countries (Szabolcs, 1994), and thesesoils also occupy more than 20% of the global irrigated area
(Ghassmi et al., 1995).
China suffers from among the most severe landdegradation problems in the world. The rapid increase indesertification since the 1970s and its tremendous impact on
China’s environment, society, and economy have received
considerable attention. The area of salt-affected soil in Chinais about 9.9 × 105 km2 (Wang et al., 1993). Salt-affected soil
distributes mainly at north, west, around Bohai Sea, and the
mid-stream of the Yellow River. Tianjin’s soil was classified
as part of the sodic soil district around the Gulf of Pohai. The
cultivated area is 4,856 km2 and occupies about 41.3% of total
area (National Bureau of Statistics of China, 2006). Almost
all of this area is dry agricultural land. About 38% of the total
cultivated area is salt-affected soil, which is classified asfollows: slight (salinity = 0.1-0.2%), 54%; medium (salinity =0.2-0.4%), 27%; heavy (salinity = 0.4-0.6%), 7%; and sodic

soil (salinity > 0.6%), 12%. Soil salinization has progressedin Tianjin because of alkalization due to desalinization,
groundwater capillarity, and irrigation. In particular, salt
concentrations in the soils of the coastal area are higher thanthose of other areas in Tianjin. This soil was classified assalinized soil because the salt consists mostly of sodium
chloride.
Sakai et al. studied the amelioration of salt-affected soil byusing flue gas desulfurization by-products in China (2004,2007, 2010). However, it is necessary to remove much salt insoil before ameliorating by using desulfurization by-products insoil that contains much salt such as sodium chloride.
Salinity is the major environmental factor limiting plant
growth and productivity. Several methods were established toreclaim salt-affected soils and were grouped into hydraulic,physical, chemical, and biological approaches. The latter
involves several techniques among which, phytodesalinationrefers to the use of Na-hyperaccumulating plants to remove
sodium from the soil. This plant-based amelioration method
is of great importance especially for several developing
countries. China has about 430 halophytes species, which fall
into 66 families and 198 genera (Zhao et al., 2002).
According to Qadir and Oster (2004), vegetative
bioremediation is a function of four main factors: (1) CO2
partial pressure within the root zone, (2) root proton release (inthe case of N2-fixing plants), (3) improvement of soil porosity
by root expansion, and (4) shoot sodium content (removed by* Corresponding Author: sakai@cc.kogakuin.ac.jp2665-1 Nakano-machi, Hachioji-shi, Tokyo 192-0015, Japan
1) Department of Environmental and Energy Chemistry, Kogakuin University, Japan

2) Department of Horticulture, Tianjin Agricultural University, China

the harvest). Several authors encourage the use of Na+ and Clhyperaccumulating halophytes for soil desalination (Zhao,1991; Keiffer and Ungar, 2002; Zhao et al., 2005).
The objective of our research is to examine salt-affectedsoil amelioration in Tianjin by using four halophytes.

2. Materials and Methods
2.1. Site location
Tianjin is situated in the northeastern part of North China
Great Plain, bordering the Bohai Sea in the east, leaning against
the Yuanshan Mountain in the north, with its terrain traversing
the Haihe River through north and south. It has become thehub of communications of North China and the gateway of thecapital city. The climate in Tianjin is warm, semi-dry tohumid and monsoon with typical features of the warm
temperature zones. The average temperature in January is
1ºC high and –8ºC low, the average temperature in July is
31ºC high and 23ºC low. Annual rainfall is on average 560mm, 80% of which falls between June and September. Dueto the cold winter and hot summer, usually two crops aregrown each year, one from late winter until summer andanother from late summer until winter. In arable fields
traditionally irrigated winter wheat is grown from November
until June, followed by rain-fed maize from June until
September/October. In horticulture a wide variety of crops isgrown. In winter many crops are protected with plastic
against the cold wind (Duart and Corré, 2003).
2.2. Halophytes
Artemisia argyi L. is an herbaceous perennial plant growing
in forest side, waste land, orchard and nursery, propagated byseed and rhizome (Zhang and Hirota, 2000). The height isfrom 20 cm to 120 cm. The leaves have been used for a longtime as a traditional Chinese medicine to treat many diseases
such as asthma (Zheng et al., 2004).
Limonium bicolor K. is perennial weed growing in seashore,
sand dune and grassland of alkaline soil, propagated by root andseed (Zhang and Hirota, 2000). It is a halophytic flowering
plant species that is tolerant to a wide range of harshenvironments (Bouchereau et al., 1999), indicating that it hasdeveloped molecular and physiological systems to adapt toadverse stress conditions. It is a desirable plant for studies
characterizing genes and mechanisms responsible for plantstress tolerance (Ban et al., 2011). The height is from 20 cm to70 cm. Radical leaf is obovate-spoon form, 2-7 cm length.
This plant has the cymose panicle on top of stem, white sepal,
and yellow petal.
Melilotus suaveolens L. is annual or winter annual weed
growing in mountainous district, circumference of arable land,roadside, river side and bush, propagated by seed. The heightis from 60 cm to 90 cm and leaf is ternately compound leaf.
Leaflet is oblong-oblanceolete and yellow papilionaceous flower
attach racemosely on leaf axil (Zhang and Hirota, 2000).
Salsola collina P. is common annual weed of up-land field
and orchard, growing in alkaline soil and dry land, propagatedby seed. Stem is branching at lower part and leaf is columnar,
succulent. Flowering time is in July-October, spike on upper
part of branch (Zhang and Hirota, 2000).
2.3. Sampling and Measurement methods
Soil samples were collected in Dagang district (DG),
Xiqing district (XQ), and Jixiang county (JX) of Tianjin.
Seeds of four halophytes, (A): Artemisia argyi L., (B):Limonium bicolor K., (C): Melilotus suaveolens L., and (D):Salsola collina P. were collected on the Tianjin Agricultural
University Campus in Tianjin, China. Twenty healthy seeds
were planted in each of three pots (25 cm in diameter and 20
cm in height) as replicates for each treatment in a greenhouse.
In the pot test, 4 kinds of wild halophytes were cultivated in 3
kinds of salt and alkali soils selected from the wastelands ofDagang district, Xiqing district and Jixian county of Tianjin city.
Plants were grown in a temperature (18-32ºC) and humidity(50-70%) controlled greenhouse. To compare the effects ofsalinity on three soils, the height and stem diameter of plants
were measured together with soil properties. Soil samples
were dried (45ºC) in 48 hours, ground using a pestle andmortar, and passed through a 1 mm sieve before the all
chemical analysis.
Soil properties (pH, EC, CEC,exchangeable Na, soluble ions such as Ca, Mg, SO4, CO3,HCO3, Cl) before and after growing these plants weremeasured. The pH, electrical conductivity (EC), and solution
cations were measured using 1:5 water extracts. The cationexchange capacity (CEC) was determined using 1 N NaOAc at
pH 8.2. Ca2+, Mg2+ and SO42- contents of soil solution were
measured by titration with ethylene diamine tetraacetate.
CO32- and HCO3- in the saturated paste extracts weredetermined by titrimetric method using 0.010N H2SO4. Cl
was determined by titration using 0.005N AgNO3 solution.
Plant samples were dried, ground, and analyzed for Na and K
contents using a 0.5% HNO3 solution and measured bytitration.

3. Results and Discussion
3.1 Soil Analysis
The chemical properties (pH, EC, ESP, and CEC) of three
pot test soils (Dagang (DG), Xiqing (XQ), and Jixian (JX)) are
shown in Table 1. Soil pH, EC and ESP in DG soil have thehighest values among three soils. XQ soil has high ESP value

Table 1. Chemical properties of Dagang, Xiqing, and Jixiang soils.
pH [-]

EC [dS/m]

ESP [%]

CEC [cmol/kg]

Dagang (DG)

8.5

57.0

66.2

15.6

Xiqing (XQ)

8.2

10.8

51.4

4.0

Jixian (JX)

7.6

5.9

1.5

23.1

9.5(a)

9

pH [-]

8.5
8JX-C

JX-D

JX-B

JX

JX-A

XQ-C

XQ-D

XQ-B

XQ

XQ-A

DG-C

DG-D

DG-B

DG

7DG-A

7.5

pot test

70(b)

60

EC [dS/m]

5040
30
20

JX

JX-A

JX-B

JX-C

JX-D

JX

JX-A

JX-B

JX-C

JX-D

XQ-D

XQ-C

XQ-B

XQ

XQ-A

DG-D

DG-C

DG-B

DG

0DG-A

10

pot test

70(c)

60

ESP [%]

50403020

XQ-D

XQ-C

XQ-B

XQ

XQ-A

DG-D

DG-C

DG-B

DG

0

DG-A

10because of low CEC value. JX soil has the largest CEC andlowest values in pH, EC, and ESP.
Soil pH, EC, and ESP in test pot before and after thegrowth of halophytes were measured (Fig. 1(a), (b), (c)). In
pot test in Dagang soil and Xiqing soil, pH values after theplant growth increased compared with that before growth (Fig.
1(a)). In the case of pot test in Jixian, pH values in Artemisia
argyi L. (A) and Salsola collina P. (D) is almost the same as thevalue before the growth, and pH value is slightly higher in thecase of Limonium bicolor K. (B) and is slightly lower in
Melilotus suaveolens L. (C). In the all cases of Limonium
bicolor K. (B), soil pH after the growth was increased (Fig. 1(a)).
Soil EC decreased drastically after the growth of four
halophytes in three salt-affected test soils (Fig. 1(b)). SoilESP decreased in the case of both DG soil and XQ soil after thegrowth of four halophytes (Fig. 1(c)). By contrast, ESP in JX
soil increased after the growth. The increase of the hydraulicconductivity due to the root growth allows the leaching of Na+
below the effective rooting depth. As a result, the drasticallydecrease of EC value after the halophyte growing could beconfirmed. Moreover, salt-affected soils, especially, sodic
soils are ameliorated by the provision of a readily available
source of Ca2+ to replace excess Na+ on the cation exchange
complex. The displaced Na is leached from the root zone
through the application of excess irrigation water.
3.2. Plant analysis
The height and diameter of stem of four halophytes after
four months were measured (Figs. 2 and 3). In Figures 2 and3, the measurement results in normal soil (CK) (CEC =73.0cmol/kg, ESP = 8.2%) were added to results of halophyte
A, B, and C. The height and diameter of stem of A in pot test
was lower and smaller than that of CK. In the case of C, theheight and diameter of stem was higher and bigger than that ofCK. In halophyte B, the height was almost the same value,
but the stem diameter increased with the increase of soil EC.
Therefore, the growth of Limonium bicolor K. (B) accelerates
with the increase of salt concentration and has the possibility ofabsorbing salts in soil.
The correlation coefficients of Na and K concentration in
halophyte with the diameter of stem were significant (Figs. 3 and4): 0.809** and 0.836**, respectively (P values < 0.05*, 0.01**).

4. Conclusion

pot test
Fig. 1. Changes in soil pH, EC, and ESP in each pot test before andafter the growth of four halophytes. (Site: Dagang (DG), Xiqing(XQ), Jixiang county (JX), Halophytes (A): Artemisia argyi L., (B):Limonium bicolor K., (C): Melilotus suaveolens L., (D): Salsolacollina P.)

Four halophytes were effective for amelioration thesalt-affected soil that contains much salt and confirmed thegood correlation between the growth of halophytes and Na andK content in halophytes. Moreover, we propose the new soilamelioration method to add desulfurization gypsum to soil afterReferences
120

DGXQJXCK

height [cm]100
806040200ABCD

halophyteFig. 2. Comparison of the height of halophytes after the growth.
1.6
DGXQ
JX
CK

diameter of stem [cm]

1.4
1.2
10.8
0.6
0.4
0.2
0A

BCD

halophyteFig. 3. Comparison of the diameter of stem of halophytes after thegrowth.
1.6
DG
XQ
JX
CK

diameter of stem [cm]

1.4
1.2
10.8
0.6
0.4
0.20A

B

CD

halophyteFig. 4. Concentrations of Na and K in four halophytes after thegrowth.

phytodesalinization because of both high pH and high ESPafter treatment.

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