IJERD – International Journal of Environmental and Rural Development (2015) 6-1

Research article
erd

Site-specific Soil Conservation Approaches in Desertificationprone Areas in the Inner Mongolia Region, China
KINGSHUK ROY*
College of Bioresource Sciences, Nihon University, Kanagawa, Japan
Email: roy.kingshuk@nihon-u.ac.jp

TOSHIHARU SHIMOWATARI
College of Bioresource Sciences, Nihon University, Kanagawa, JapanZHANG WEI
China Agricultural University, Beijing, China
Received 20 January 2015

Accepted 31 May 2015(*Corresponding Author)

Abstract Desertification is still a severe problem in the Inner Mongolia region of China,
despite the country’s efforts to stop land degradation. The authors carried out periodic fieldsurveys for over a decade in different desertification-prone arid lands of Northern China.
Based on a series of experiments and analyses, this paper proposes locally-tailoredtechnologies that can ensure greater participation, and lead to more effective, sustainablemeasures to combat desertification in the area. Specifically, the potential of both cotton andcoal ash as water-holding materials was experimented with sandy soil. From the results, anamount of 0.5% (by weight) cotton and 3% (by weight) alkali-treated coal ash (named
artificial zeolite) mixed with sandy soil could ensure water retention in the soil and sofacilitate upland crops growing in arid environments. The results also showed that, if mixed
individually with the soil, both of these materials demonstrated constant positive effect aswater-holding materials. However, dual application (both the items mixed together withsoil) did not show constant positive effect. In addition, to diversify the potential uses of coalash, the effects of artificial zeolite as a particle film sprayed over plant-leaves were also
tested. The results showed that cotton plants with a particle film that were grown in sandy
soil tended to transpire less water than those plants without a particle film on their leaves.
Finally, since the properties of applied forms of coal ash (i.e. the artificial zeolite) differ
based on the processing methods (alkali treatment) used, proper selection of the type of
artificial zeolite could further diversify its potential uses, for example as a salinity mitigatorin arid soil.
Keywords desertification, site-specific, water-holding material, arid land, sustainability

INTRODUCTION
Afforestation has been the most popular measure used to combat desertification in many arid land
areas of the world as well as in the Inner Mongolia region in China, which is experiencing severe
desertification. Afforestation plays a very significant role in desertification control, but planting
trees is not the only measure against desertification. Instead, when only the planting of trees is
considered and no measures are considered regarding farmland to enhance the per area unit output,
the prevention of desertification fails in many cases (Fan and Zhou, 2001). Massive man-madeforests that include plants, such as poplar, larches, pines, birches, oaks, elms, lindens, and willows,
have been established in the Inner Mongolia region to prevent desertification; however, the illegal
cutting down of plants, i.e., deforestation, occurs frequently in the region (Liu, 2014). Despite
different land conservation and restoration efforts undertaken by the Chinese communes based on
ideological motivation and regulatory steps, the reality is that the encroaching rate of desertification
due to deforestation exceeds the status of prevention (Cao, 2008). Such a situation emphasizes theⒸ ISERD

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necessity of revising the basic strategies for participation in land conservation. In other words, sitespecific sustainable soil conservation approaches could encourage the mitigation of thedesertification syndrome in the Inner Mongolia region. This study thus investigated the potential
natural resources in north China that could feasibly be used as a tool(s) to combat desertification ina sustainable way. We identified the cotton plant as an alternative/complementary plant in the Inner
Mongolia region because China is the largest producer of cotton in the world and because domestic
production is mainly concentrated in the northwest Xinjiang region (Xinjiang Uyghur Autonomous
region), which is a neighbor province of Inner Mongolia. The climate and ecology of the Xinjiang
and Inner Mongolia regions are very similar. Unlike other quick growing forest plants in Inner
Mongolia, such as poplars and pines, perennial cotton plants have little value as an alternative fuelor precious wood, and are less likely to be the target of illegal wood-cutters. At the same time,
cotton has a high potential to be a cash crop. Therefore, to introduce and to grow the cotton plant inInner Mongolia would not be a difficult task from eco-environmental and socio-economic
standpoints; however, since the existing status of the production, marketing, and distribution
channels of cotton products (cotton wool and fibers) are concentrated in the Xinjiang region, andbecause the people in the Inner Mongolia region are not accustomed to growing cotton as uplandcrops, to make the cotton a cash crop in the Inner Mongolia region, problems associated withcertain factors, such as extension, marketing, and price-fixing, would arise at the initial stage
because of the imbalance in the demand-supply of the products in the locality. Therefore, theauthors also attempted to diversify the usage of cotton products in the region. Due to its nature andproperties, cotton wool is an organic substance and has good water-holding capacity. Therefore,
wasted and/or un-used portions of cotton wool can be used as an organic water-holding material in
sandy soil.
In addition, the Inner Mongolia region is an important coal production base with more than aquarter of the world’s coal reserves located in the province, which produces millions of tons of coal
fly ash as a by-product every year. Coal ash or fly ash, usually refers to ash/residue produced
during combustion of coal, is the largest quantity of industrial waste residues in China (Tang et al.,2013). To find out effective/recycle use(s) of this product is a big issue in that region. The Chinese
government has initiated some steps to recycle it as an alternative raw material for concrete andcement materials (Yi et al., 2012). In this regard, we attempted to use this waste material as a soil
improver, which could facilitate plant growth in the sandy soil. Accordingly, we experimented withcoal ash’s nature as a water-holding material not by applying it to farmland soil in its original form
but in the form of an artificial zeolite (alkali treated coal ash) because the latter has superior
physico-chemical properties than in its original form (Henmi, 1997).
This paper aims for and focuses on the identification of the site-specific problems related tosoil conservation in the Inner Mongolia region as well as the sustainable measures that involve
introducing locally originated water holding materials by using cotton plants/wools and alkalitreated coal ash (waste) based on basic experiments and investigations. In addition, to diversify theuses and the application of cotton and coal ash in the region, other potential uses of the materials
were investigated.
METHODOLOGY
Study Sites
Inner Mongolia is the third largest province (an autonomous region) in China, and it has atemperate continental monsoon climate with a sharp rainfall gradient from 50 mm to 450 mm in thewest and northeast parts, respectively, while the evaporation capacity is above 1200 mm in mostareas of this region. Most of the rainfall occurs in the summer season (May to September). The
region is characterized by a diverse ecosystem, including vast forests and agricultural lands as wellas the world’s largest temperate grasslands and extensive sandy lands and deserts (Bai et al., 2004).
Land degradation/desertification caused by deforestation and over-grazing has been severe. Between
1980 and 2000, Inner Mongolia’s population increased by 26%, from 18.76 × 106 to 23.72 × 106. TheⒸ ISERD

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most affected degraded grassland area in the region is the Xilingol League (a prefecture level
division of Inner Mongolia) where the population increased by 19%, livestock increased 177%, andthe grassland productivity decreased by 30% within the period of 1980 to 2000 (Zhen et al., 2014).
The authors carried out field surveys periodically in different parts of the Inner Mongolia region
from 2000 to 2009. The surveyed sites included grasslands and agricultural lands at five different
administrative areas named Xilinhot County, Erenhot County, Zhenglan Banner (a county level
division of Inner Mongolia), Abag Banner, and Sonid Right Banner of the aforesaid Xilingol
League along with one more site at Wuchuan County in Hohhot City (a prefecture level city). Allof these sites were prominent for desertification. The Xilingol area in particular, located in central
Inner Mongolia, had been a fertile prairie in northern China, but desertification and sand storms
have increased in the past decades. Fig. 1 shows the locations of the surveyed sites at Xilingol
League and Hohhot city, while Table 1 presents the major soil and vegetation types in thegrassland-dominated study sites.

Fig. 1 Study sites at Xilingol League in Inner
Mongolia region, China

Table 1 Major soil and vegetation types in the study sites of Inner Mongolia region
Study site

Soil type

Vegetation type

Dominant species

Xilinhot County

Chestnut

Typical steppe

Stipa species, Cleistogenes species

Erenhot County

Brown

Desert steppe

Stipa species

Zhenglan Banner

Chestnut

Typical steppe

Stipa species

Abag Banner

Chestnut

Typical steppe

Artemisia species, Stipa species

Sonid Right Banner

Brown

Desert steppe

Artemisia species, Stipa species

Wuchuan County

Chestnut

Desert steppe

Stipa species, Artemisia speciesⒸ ISERD

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Materials and Methods
Cotton and coal ash as water-holding materials: A series of indoor and outdoor experiments
were carried out by mixing cotton and alkali-treated coal ash (named artificial zeolite, henceforth
AZ) with soils (sandy and loamy soils). The indoor experiments were carried out inside an artificial
climate chamber (Fig. 2), whereas the outdoor experiments were conducted in farmland (Fig. 3).
Both of these establishments are located within the campus of the College of Bioresource Sciences,
Nihon University, Japan.
For the indoor experiments, seedlings of Chinese cabbage (Brassica chinensis L.) were used as
test plants and grown in pots filled with river sand that is used for gardening purposes. Pieces of torn
cotton wool were added at three different weight ratios (0.1%, 0.3%, and 0.5%), while Na-type
artificial zeolite (Maeda Corporation, Japan) was added to the soil (sand) at the weight ratio of 3%. A
total of 25 pots that included five replications of each item of the controls (non-treated), cotton-mixed(0.1%, 0.3% and 0.5%), and AZ-treated soils, were used to cultivate the test plants. The same doses ofchemical fertilizer (N:P:K=8:8:6) and water were used to facilitate the natural growing of the plants.
The soil moisture was measured by using a W.E.T sensor (DIK-691A; Daiki Rika Kogyo Co., Ltd.)
coupled with a time-domain reflectometer, while the physiology of the shoot-part of each plant (shootlength and number of leaves) was measured periodically throughout the growing period. In addition,
the pF values at each condition of the soil and plant weights (dry weights) were also measured.
On the other hand, for the outdoor experiments, cotton plants (Gossypium hirsutum L.) weregrown in four adjacent plots (each with a dimension of 180cm length×30cm width) with the same soil
texture (Andosol, also known as Kanto loam); however, the treatments of the soil in each plot weredifferent, namely, the control (non-treated), the 0.5% (by weight) cotton-mixed soil, the 3% (byweight) AZ-mixed soil, and the cotton plus AZ-mixed soil. In the outdoor field, Ca-type AZ wasused, and the same amount (g) of 0.5% cotton and AZ (g) was mixed in the dual application plot. To
measure the periodic in-situ soil moisture and the pF, soil-moisture sensors (ECH2O-10; Decagon
Devices, Inc.) attached to a data logger (Em5b; AINEX Co., Ltd.) and tensiometers (Daiki-8331;
Daiki Rika Kogyo Co., Ltd.) were installed at each plot, respectively. The W.E.T sensor (DIK-691A;
Daiki Rika Kogyo Co., Ltd.) was also used to cross check the recorded soil moisture values. Periodic
measurements of the physiology of the plant-shoots (shoot length and number of leaves) as well as
the biomass (dry weight, fresh weight) of the plant bodies were also carried out.
Coal ash as a particle film on plant-leaves: Inside a glass house (Fig. 4), a total of 24 cotton
plants (Gossypium hirsutum L.) were grown in cultivation pots filled with two different textured
soils (12 plants of each soil), namely, sand and Andosol/Kanto loam. A small amount of Ca-type
AZ (Chubu Electric Power Co., Inc., Japan) with the pH value adjusted to 7 was mixed with waterand sprayed over the foliage sections in equal numbers of the 6 young cotton plants (6 replications)from each soil type. The remaining 6 plants from each group (soil type) received no foliar-spray.
After drying-up, the dust-like particle film created partial blockage to the stomata at the upper leaf
surface. The plants were then grown by applying the usual doses of compound fertilizer(N:P:K=8:8:6). The parameters related to the plant growth, such as shoot length, number of leaves,stem-diameter, leaf-temperature, and leaf area as well as the daily transpiration rate were measured
periodically. In addition, at the latter half of the growing stage, a 10-day long dry-down experiment
was carried out on the plants by applying water equal to the 80% of their daily transpiration
amounts. To identify the status between the transpiration and the available water for plant growth,
this watering scheme followed a similar procedure as described by Sinclair and Ludlow (1986).
Finally, the dry weights of the plants were measured.
Other potential uses of cotton and coal ash: Salinity is also an issue in many arid lands and insome areas of our study sites as well. To investigate the potential of coal fly ash and cotton as
salinity mitigators, a number of experiments (Kaneuchi et al., 2008; Roy et al. 2009; Nishimura andRoy, 2010) have been carried out by applying AZ and waste cotton materials to different types of soil
with different protocols. This paper will present an experiment in which a small amount of Ca-type AZⒸ ISERD

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Fig. 2 Experiments inside the artificial
climate chamber

Fig. 3 Experimental plots with cotton-plants
growing in different conditions

Fig. 4 Experiments inside the glass house witha particle film sprayed over cotton plants

Fig. 5 Experiments of artificial zeolite andcotton gauze as salinity mitigators

Table 2 Major physico-chemical properties of artificial zeolites (AZ) and soils used in theexperiments
Type

Particle size

EC
(dSm-1)

pH
(H20)

Na

Exchangeable cation
cmol(+) kg-1
K
Ca

Mg

CEC
cmol(+) kg-1

Sand

0.2～2 mm

0.12

6.9

0.8

0.1

0.5

0.1

6.5

Andosol

0.02～2 mm

0.33

6.2

0.3

2.9

2.6

0.6

18.7

Ca type AZ

5～100 μm

1.60

9.8*

122.0

15.3

151.0

1.9

260.8

Na type AZ

5～100 μm

1.10

11.2

160.0

11.4

111.0

0.2

210.0

Note: * Except the pH adjusted to 7 for fA zeolite during particle film spray(named fA zeolite, Maeda Corporation, Japan) was applied to the top surface of artificially-prepared(by 5% sodium chloride solution) saline soil (Andosol/Kanto loam) filled in 8 Wagner pots (Fig. 5).
The treatments in every two pots were different. Of the 8 pots, two had 5mm thin AZ-layers
applied directly to the top of the soil, while the same amount of AZ was sealed in between the
double-fold cotton gauze pockets in two other pots. Five-fold cotton gauzes were laid over thesurface soil in two pots, and two remaining pots were kept under no-treatment (control) conditions.
The pots with moist saline soil were placed in an artificial glass chamber (relative humidity: 60%,
average temp: 25°C) for 30 days. The soil samples from the upper layers were collected, and theconcentrations of specific ions (Na+ and Ca++) in the soil samples were investigated by using anⒸ ISERD

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Atomic Absorption Spectrophotometer (AA-6800; Shimadzu Corporation, Japan). Also, the electricalconductivity of the soil samples was measured by using an EC meter (B-173; Horiba, Japan).
Table 2 presents the major physico-chemical properties of artificial zeolite (AZ) and farmland
soil (Andosol/Kanto loam) used in the different experiments.
Statistical Analysis
All data were statistically analyzed using MiniTab statistical software. Particularly; mean, standard
deviation, and percentage were determined using descriptive statistics. Mean of treatments werecompared by One-way ANOVA (Analysis of Variance) at 0.50 significance level.
RESULTS AND DISCUSSION
Cotton and coal ash as water-holding materials: Fig. 6 and 7 show the variations in the average
physiological growth (shoot length) and the soil moisture content under each condition (treatment)
throughout the growing period carried out for the indoor experiments. As can be observed from thefigures, while the AZ-treated soil had the highest soil moisture content accounting for an average of 35% higher than the other pots, the plant-growths (shoot lengths) were better in the order of 0.5% cottontreated, 0.3% cotton-treated, and AZ-treated soil. Fig. 8 illustrates the pF-soil moisture curve ineach treatment from which it was found that regarding the effective pF range to grow plants (pF=1.8
1418

Soil moisture (%)

Shoot length (cm)

12
10
8
6
4

Control
0.1% Cotton
0.5% Cotton

20AZ
0.3% Cotton

15
12
9
6
3
0

Control
0.1% Cotton
0.5% Cotton

AZ
0.3% Cotton

Date (month/day)

Date (month/day)Fig. 6 Variations in the shoot length (B. chinensis)
at different treatments of soil (indoor)

Fig. 7 Variations in the soil moisture content at
different treatments of soil (indoor)

35

Control
0.1% Cotton
0.5% Cotton

AZ
0.3% Cotton

Soil moisture (%)

30
25
20
15
10
5
0
0

1

2

3

4

Soil pF

Fig. 8 Soil moisture retention curves atdifferent treatments of soil (indoor)

Fig. 9 Plant growth at different treatmentsof soil (indoor)Ⓒ ISERD

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90

500

AZ+Cotton
AZ
CottonControl

450

Yield (g)Shoot length (cm)

120

60

AZ+Cotton
AZ
CottonControl

400

30

350

0

300

Treatment

Observation period

Fig. 10 Variations in the shoot length (G. hirsutum) Fig. 11 Variations in the yields of cotton balls at
at different treatments of soil (outdoor)
different treatments of soil (outdoor)

3

3

AZ+Cotton
AZ
CottonControl

AZ+Cotton
CottonAZControl

2.5

Soil pF

Weight (kg)

3.5

2

2.5
1.5

1

2

Treatment

Date (month/day)Fig. 12 Variations in the dry weights of plants
at different treatments of soil (outdoor)

Fig. 13 Variations in the soil pF values atdifferent treatments of soil (outdoor)

to 3.0), the AZ-treated soil followed by the 0.5% and 0.3% cotton-mixed soils had better soil
moisture capacity. In addition, considering other measured parameters, such as the plant weight
and the number of leaves, the AZ-treated soil and the 0.5% cotton-mixed soil were found to be themost suitable treatments among all of the treatments when using them as water-holding materials forthe soil. Fig. 9 shows the average growing conditions of the plants under each condition.
Fig. 10, 11 and 12 show the average variations in the representative physiological parameters,
including the shoot length, yield (weights of cotton balls), and dry weight of the plant bodies (shootplus root), for cotton plants grown in outdoor plots. From the figures, it can be seen that AZ andcotton wool mixed independently with soil favored the cotton growth/production; however, whenthese materials were mixed together and applied jointly to the soil, the growth/production trailed
behind the control (no-treatment) condition. A similar tendency was also found for other measured
parameters (number of leaves, biomass). The specific problems related to the dual application of
AZ and cotton wool that may be caused by poor function are: slaked finer particles of soil/AZ
blocked pores of the cotton wool, the formation of a type of a soil crust, reduced infiltration andwater movement through the soil, and the hampered growth/yield of the plants. Fig. 13 shows theperiodic variations in the soil pF values with each treatment. While the pF values in all of the plots
ranged from 1.25 to 2.5 (within the range suitable for plant growth; pF =1.8 to 3.0), the cottontreated plot showed the most stable values that ranged from pF= 1.5 to 2.5 followed by the AZⒸ ISERD

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treated plot with pF values that ranged from pF= 1.3 to 3.0 throughout the growing period. On theother hand, unlike the indoor experimental results, the soil moisture content did not show distinct
differences among the treatments in the outdoor experiments.
Coal ash as a particle film: Variations in the transpiration rate of the plants grown with andwithout a particle film in both types of soil (sand and Andosol) are presented in Fig. 14, while Fig.
15 and Fig. 16 present the variation in the shoot lengths and the dry weights of the plant bodies.
From the figures (Fig. 15 and Fig. 16), it can be observed that the plants with a particle film
sprayed over the leaves had slightly higher average growths than the plants with no particle film inboth types of soils. A similar tendency was also found in cases of other physiological parameters(number of leaves, stem-diameter, and leaf area); however, in the case of the daily transpiration rate,
the tendency varied in the soil types both before and after the dry-down period (Fig. 14). To
identify the specific effect of each treatment on the transpiration, the normalized transpiration rates(daily relative transpiration rates normalized against the plant growth) for each treatment wereplotted against the fractions of transpired soil water (the ratio of daily transpired soil water to thewater at field capacity) following the Sinclair and Ludlow (1986) method (Fig. 17). From thedifference/degree of inclination between the two approximate straight regression lines of the same
soil with and without a particle film, the results show that cotton plants with a particle film thatwere grown in sand transpired less water than the plants without a particle film on their leaves.
Uses of cotton and coal ash as potential salinity mitigators: Variations in the average ionconcentrations (Na+ and Ca++) at the top surface soil in the pots with different treatments arepresented in Fig. 18, while the average EC concentrations are presented in Fig. 19. The results showthat the AZ application (direct application and inside cotton gauze packets) reduced the concentrationof Na-ion in the topsoil; however, the Ca-ion concentrations also reduced slightly in comparison withthe control and cotton gauze treatments (Fig. 18). The reason is that the type of artificial zeolite usedin the experiment (Ca type) was not saturated by specific exchangeable ions (Ca++) and was part ofCa-ion thus transmitted from the topsoil to the finer AZ particles. The variation in the average EC
values at the end of the experiment as shown in Fig. 19 also supports the tendency found in the caseof changes in the Na-ion concentration in the topsoil. Therefore, it can be said that AZ has a great
potential to be used as a salinity mitigator; however, depending on the properties of AZ, such as thetype/method of alkali used to process the coal ash, the extent of salinity mitigation will vary.
Moreover, the salinity mitigation capacity can be maximized while using AZ in cotton packets.
CONCLUSION
The experiments carried out in this study focuses on different potential uses of cotton and coal ash
as soil improvers by using them as soil water holding materials, as transpiration reducers by using
them as foliar particle film materials, and as salinity mitigators by using them as salt absorbents inarid land soil (sandy and loamy). The results show that mixing small amounts of these items(artificial zeolite: 3% by weight; cotton wool: 0.5% by weight) with soil (sandy and loamy types)
could facilitate plant growth in arid land soils (sandy and loamy). In addition, if used as a particle
film, pH-adjusted (to 7.0) coal ash (artificial zeolite) can sustain plant growth with lesstranspiration, and this anti-transpiration capacity maximizes in sandy soil in comparison withloamy soil. Moreover, based on the type/processing of the materials, utilizing the higher cationexchange capacity (CEC) of artificial zeolite, specific ions responsible for salinization (Na+, K+,
Ca2+, Mg2+ and Cl-) can be removed from soil (loamy), and this salinity mitigation capacity
maximizes if it is used in packs made of cotton gauze. These experimental findings demonstrate thediversified potential uses of cotton and coal ash in an arid land environment. In other words,
potential and proper uses of two locally tailored items to combat desertification in the Inner
Mongolia region are identified from this study.
The sustainable conservation of natural resources, such as soil and water, of an area incorporates
many bio-physical and socio-cultural interdisciplinary actions regardless of being a developing orⒸ ISERD

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65

Dry-down experimentDry-down experiment

60

90

Shoot length (cm)Daily transpiration (mL)

110

70
50
Andosol with particle film
Andosol without particle film
Sand with particle film
Sand without particle film

30
10

55
50
45
40

Andosol with particle film
Andosol without particle film
Sand with particle film
Sand without particle film

35
30

Date (month/day)

Date (month/day)Fig. 14 Variations in the transpiration rate byplants with and without a particle film

8

Fig. 15 Variations in the shoot length of plants
with and without a particle film

1.4

Normalized transpiration rate

Shoot

Dry weight (g)

Root
6

4

2

0

Particle film

No particle(Andosol) film (Andosol)

Particle film

No particle(Sand)

film (Sand)

1

0.6

0.2
1

0.8

0.7

0.6

0.5

0.4

0.3

Fig. 17 Variations in the transpired amount of soil
water during the dry-down experiment

3.5

Na ion3

Ca ionEC (dS m -1)

Concentration (cmol(+) kg -1)

Fig. 16 Variations in the dry weights of plants
with and without a particle film

2

0.9

Fraction of transpired soil water

Treatment

2.5-●Particle film (Andosol)-●No particle film (Andosol)-●Particle film (Sand)-●No particle film (Sand)

1.5
1

2.5
2
1.5
1

0.5

0.5
0

0
AZ+Cotton
gauze

AZ

Cotton gauze

Control

AZ+Cotton
gauze

Treatment

Fig. 18 Variations in the average ion-concentration
at surface soil with different treatmentsⒸ ISERD

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AZ

Cotton gauze

Control

Treatment

Fig. 19 Variation in the average EC values atsurface soil with different treatments

IJERD – International Journal of Environmental and Rural Development (2015) 6-1

developed country. From the case studies in the study sites, it is not easy to conclude that ecoenvironmental and natural resource problem(s) are always easier to manage in a specific area
because it depends on the facts and the circumstances of each case. As stated in the methodology
section, we carried out a number of preparatory experiments to set and to determine the mostsuitable ratios among the concerned parameters (e.g., soil, water, cotton, coal ash, and vegetation)in our study area, which was the Inner Mongolia region. Some of the study sites as well as otherpotential resources in this particular region (studies are currently being conducted) are not includedin this paper; however, the results and the analyses discussed in this paper outline that the locallyavailable/waste materials, specifically cotton and coal ash in our study, have a great potential to be
used as soil improvers that facilitate plant growth and thus combat desertification in a site-specificand sustainable way. To achieve the best results, carrying out outdoor experiments in the study
fields and convincing the local people to accept the extension of our technologies would be more
effective from the perspective of field-application. Also, follow-ups and feasibility surveys at theinitial stage (if accepted by the local people) would be necessary.
ACKNOWLEDGEMENTS
The authors would like to express thanks to the students of the International Environment
Conservation Lab at the College of Bioresource Sciences, Nihon University, Japan, for theirsupport in carrying out the experiments and sample analyses. Thanks are also due to the students ofChina Agricultural University who assisted a great deal during our field visits. Prof. Jiang-sheng
Wei and his colleagues of Inner Mongolia Agricultural University also cooperated in the fieldsurveys. Part of the field investigations to the study sites was covered by grants-in-aid of JSPS
(Japan Society for the Promotion of Science). We are also grateful to the anonymous referees of thejournal for their valuable comments and suggestions.
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