Vetiver System for Land Reclamation

Reviewer

Hanping Xia

Application of the Vetiver System in the Reclamation of Degraded Land

Hanping Xia1, and Wensheng Shu2

1
South China Institute of Botany, Chinese Academy of Sciences, Guangzhou 510650, China
2
School of Life Sciences, Sun Yatsen (Zhongshan) University, Guangzhou 510275, China

Abstract: Land degradation is becoming one of the severest environmental issues in the world, especially
in developing nations. Land degradation, usually accompanied by soil erosion, always results in a
decrease or complete loss of land productivity, and produces on-site and off-site pollution to soil and
water. The methods for land reclamation are various, including physical, chemical and biological. The
cost for reclamation of degraded land using old methods is huge, but far cheaper, using new biological
methods. Vegetation or revegetation is a chief biological measure, but the key is choosing the right
species. Trees, shrubs, creepers, and herbs can be used to reclaim degraded land, but the best species are
grasses due to their strong resistance to adverse conditions, and fast-growing feature. Among them,
vetiver (Vetiveria zizanioides) is the most typical representative. As a species of land reclamation, vetiver
has various kinds of miraculous characteristics and functions, such as rapid growth, huge biomass,
massive and long roots, strong abilities to control erosion and stabilize slopes, and huge capacities of
phytoremediation. Applications around the globe as well as in China indicate that vetiver is really a
miracle species for land reclamation, including reclamation to barren mountains or hills, contaminated
water and soil, mined lands, quarries, etc. It exhibits a very wonderful future in South China for land
reclamation.
Key words: Vetiver System, land reclamation, phytoremediation, erosion control, sustainable
development
Email contact: Hanping Xia <xiahanp@scib.ac.cn>

1 INTRODUCTION

Land degradation is referred to a reduction or loss in the capacity of land to supply benefits to
humanity. It results from an intricate nexus of social, economic, cultural, political, and natural forces
operating across a broad spectrum of time and spatial scales (Barrow, 1991; Daily, 1995). A great part of
land degradation is derived directly from soil erosion. The two ecological processes, generally concurrent,
usually cause a serial of other ecological and social problems. Among them, the most prominent one is
on-site and off-site pollution, thus causing a decrease of land productivity or land degradation in the lower
reaches. The main factors evoking land degradation consist of natural or artificial factors, and the artificial
from industrial or agricultural development, etc. With the development of human society, land
degradation evoked by artificial factors is becoming more and more conspicuous, accounting for a far
greater part of degraded lands.

2 SEVERE SITUATION OF LAND DEGRADATION AROUND THE GLOBE

It is estimated there has been nearly 2_109 hm2 soil degraded due to excessive artificial activities
since 1945, accounting for 15% of the total terrestrial areas. Of this, about 750 _106 hm2 (38%) are
classified as lightly degraded (defined as exhibiting a small decline in agricultural productivity and
retaining full potential for recovery); about 910_106 hm2 (46%) are moderately degraded (exhibiting a
great reduction in agricultural productivity; amenable to restoration only through considerable financial
and technical investment); about 300_106 hm2 (15%) are severely degraded (offering no agricultural
utility under local management systems; reclaimable only with major international assistance); and about
9_106 hm2 (0.5%) are extremely degraded (incapable of supporting agriculture and unreclaimable) (Daily,
1995). Up to 2000, 50% of wetlands in the world have been destroyed, and 50% of rivers polluted;
desertification has influenced over 100 nations, nearly 1 billion people. At present, the forest resource
vanishes at the speed of 16_106 hm2 annually (Qing et al., 2002). Therefore, it is very urgent to control
land degradation and to reclaim the degraded lands.

3 COMMON METHODS FOR LAND RECLAMATION AND THEIR COSTS

In order to rehabilitate or reclaim degraded lands, especially mined lands, various methods have
been utilized globally. Of them, the physical and chemical methods, such as irrigation, burying, filtration,
or removal of pollutants, or similar treatments (Table 1), are extensively used (Bradshaw, 1997; Xia and
Cai, 2002). However, these methods are generally expensive, and sometimes are impossible to carry out,
for the volume of contaminated materials in many cases is very large, especially those produced by
mining and industrial production.
So far, information on rehabilitation cost is still lack. In general, however, the rehabilitation for
degraded lands by common methods is quite expensive. For example, it is estimated that cleanup of
hazardous wastes by conventional technologies is projected to cost at least $400 billion in the U.S. alone;
and cleanup of the U.S. sites contaminated with heavy metals alone can cost $7.1 billion while mixtures
of heavy metals and organics bear an additional $35.4 billion price tag (Salt et al., 1995). UNEP’s
estimates of the direct annual cost of all preventive and rehabilitative measures range between $10.0
billion and $22.4 billion, and the direct, on-site cost of failure to prevent desertification during the period
1978–1991 at between US $300 billion and $600 billion.

4 VEGETATIVE MEASURES FOR LAND RECLAMATION

If wastes cannot be effectively treated or removed, off-site pollution, usually coming from wind or
water erosion or leachate, must be prevented first. An effective approach is the vegetation measure, one
of the most practical and economical methods for pollution control and land reclamation. Table 1 shows
that the long-term treatment measures for mined land restoration are almost all vegetation or tolerant
species selection. However, revegetation to polluted sites is often difficult and slow due to the hostile
growing conditions, which include the toxicity of heavy metals, organic compounds, strong acidity, etc.
Table 1 The major problems of mined land and their Immediate and long-term treatment
measures for rehabilitation or reclamation*
Limiting factor Problem Immediate treatment method Long-term treatment method
Heavy metal Too high Organic matter or tolerant Tolerant or hyperaccumulator
Acidity Too low species
Lime species
Tolerant species leaching
Too high Pyritic waste or organic Weathering or tolerant species
Organic matter Deficiency matter
Manure, sludge, garbage Vegetation or tolerant species
Nutrient N deficiency N fertilizer Legume or other N-fixer
Deficiency of Appropriate fertilizer Mineral weathering or tolerant
other elements species
Moisture Too wet Drainage Tolerant species
Too dry Irrigation or cover Tolerant species
Structure Too compact Rip or scarify Vegetation
Too loose Press or cover with fine Vegetation or leaching
material
Organic pollutant Too high Covering or irrigation Biodegradation
Salinity Too high Irrigation Tolerant species
Stability Erosion Cover Vegetation
Slippage Engineered measure (e.g. Vegetation or engineered measure
soil–keeping stone wall)
Texture Too coarse Organic matter or clayed soil Natural weathering
Too fine Organic matter Vegetation
*Cited from Bradshaw (1997), and Xia and Cai (2002); slightly modified

In fact, vegetation or revegetation for erosion control, pollution mitigation and land reclamation
has been used since ancient times, usually based on past experience, observation, or empirical methods.
For example, there was precise recordation in a Chinese ancient agricultural monograph named “Huai
Nan Zi” and finished some 2000 years ago that it should adopt different tillage and culture measures to
fertile soil, infertile land, high mountain, and low hill; the places that are not suitable to plant crops
should be vegetated with trees or bamboos.
The resurgence of the practice in a more scientific and methodical manner began in the 1930s in
Europe. Over the last two decades, the practice has become more popular due to heightened awareness of
environmental issues as well as its availability, persistence, and cheapness (Bradshaw and Chadwick,
1980; Peng, 2003). The planting of grasses, legumes, shrubs and trees have been used for quite a few
decades for land reclamation with varying degree of results. However, it is very important to select
appropriate plant species according to the different soil and topography situations. Eucalyptus and Acacia
are two types of usually used pioneer trees for land reclamation in tropical and subtropical regions like
China, due to their some excellent characteristics, such as rapid growth and relatively strong resistance to
harsh environments. But eucalyptus has lots of negative ecological effects. 1) It has a huge water
absorbing capacity, which makes ground water level decrease distinctly. 2) Some kinds of eucalyptus,
such as E. exserta and E. urophylla, have strong allelopathic effects, or have significant inhibitions on
seedlings growth of many plants, thus making the undergrowth sparse or scarce (Zeng and Li, 1997). 3)
Eucalyptus hardens the soil surface (Zhou, 1997a). Acacia like A. mangium or A. aurifuliformis, has also
been utilized extensively in the tropics and subtropics for the identical goal. As a pioneer, it takes good
effect for land reclamation and ecological restoration in the early stage, but its ecological effects decrease
gradually about twelve years later. Another drawback often encountered with A. mangium is that its
branches are rather brittle and prone to snap in the event of strong winds or typhoons (Hengchaovanich,
stem-flow, possibly up to hundreds of litres a day during rain, resulting in local scouring
(Hengchaovanich, 1999). Apart from this above, the dribbling water drops from leaves of broad-leaved
trees generally have larger diameter than those from coniferous trees or from atmospheric precipitation;
as a result, they increase the dash of waterdrops to the forest land, especially in the situation of low
intensity of rainfall. Therefore, the canopy of broad-leaved forest without understory generally hampers
the topsoil conservation on forestland (Zhou, 1997a,b). It is well-known that Eucalyptus and Acacia
almost all formed pure artificial forests with little or even without understory, therefore they both are not
very suitable for erosion control and land reclamation.
Obviously, plants used for land reclamation should be species with strong resistance, rapid growth,
and good rehabilitation effect. Grasses and herbaceous legumes are generally the first choice because the
majority of the two kinds of plants have strong vitality and infertility-enduring ability; furthermore the
latter can fix nitrogen. However, compared with grasses, the resistance of legumes to adverse conditions
is still limited, on the whole; they cannot survive in some very harsh habitats. As to grasses and other
creepers, many of them have strong resistance and huge biomass and therefore some of them can be used
effectively to reclaim degraded land. However, there are still many species of grasses that are not very
suitable to be as land stabilization. For example, Miscanthus (e.g. M. floridulus and M. sinensis), and
Arundinell nepalensis generally grow on rocky mountains, but their roots are neither so massive nor
strongly penetrative. Another example, Wedelia trilobata can produce a very quick and good covering
effect on a barren land surface, but it has an allelopathy to other plants, and furthermore it is easily to
prone to become a weed. Therefore, it is natural and also imperative to look for a new plant species for
the purpose of land reclamation that is cheap, effective, persistent, and easy to be cultivated and managed.

5 VETIVER TECHNIQUE FOR LAND RECLAMATION

Vetiver (Vetiveria zizanioides), a perennial grass, has been widely accepted as a better alternative
for land reclamation in the past a twelve years due to it’s following excellent features: 1) strong resistance
to adverse conditions, which adapts it to various harsh weather and environmental conditions; 2) strong
ability to remove pollutants, which makes it rehabilitate the polluted land rapidly; and 3) huge biomass,
including shoots and roots, which makes it effectively ameliorate the degraded soil and cover barren land
rapidly. Today, the application of vetiver technique is increasingly extensive.

5.1 The Earliest Application in China

In the spring of 1991, the first project was carried out in Xingning County, East Guangdong for the
purpose of recovering a barren red soil slope called ‘Red Skin Hill’ (RSH) (Ao et al., 1993). This is the
earliest application for land reclamation in China (Xia et al, 1996; Xia, 2001). Prior to conducting the
Vetiver Eco-engineering, the slope had been tried to cover artificially four times, but none had success
due to the harsh environmental conditions of RSH. One year after applying the vetiver technique, dense
vetiver hedgerows were formed and erosion was controlled and furthermore tree saplings began to grow. 29
months after applying the technique, the content of most soil nutrients increased except for available P (Table 2).
Moreover, soil moisture in the fruit-grass complex garden was increased by 4–42%, relative humidity increased
by approximately 4–5%, and air temperature in summer decreased by 1–3 degrees centigrade, compared with the
pure fruit grarden garden (Table 3). Nine years later, the little tree saplings planted in those days became forest,
and the original ‘Red Desert’ finally became an ‘oasis’ (Xia, 2001). As a result the soil quality was enhanced and
the farmland microclimate was ameliorated distinctly.
Table 2 Changes of soil properties 29 months after applying the Vetiver System on the Red Skin
Hill (RSH)
Depth Organic matter Total N Hydrolytic N Available P Available K
Sampling
No. (%) (%) (mg/kg) (mg/kg) (mg/kg)
locality
(cm) Before* After Before After Before After Before After Before After
1 Top of 0-20 1.10 1.07 0.039 0.063 37.5 57.4 0.8 0.6 13.3 19.1
RSH
2 Top of 20-40 0.66 0.95 0.032 0.061 33.4 56.7 1.6 0.7 11.6 15.4
RSH
3 Top of 40-60 0.81 0.74 0.038 0.059 36.3 48.2 1.1 0.6 8.34 15.4
RSH
4 Middle of 0-20 0.41 0.49 0.018 0.028 37.9 49.5 1.0 0.3 17.8 26.5
RSH
5 Middle of 20-40 0.36 0.38 0.016 0.027 36.2 45.8 0.9 0.3 23.2 22.0
RSH
6 Middle of 40-60 0.37 0.57 0.020 0.025 38.1 46.1 0.9 0.2 17.8 24.9
RSH
* “Before” means before planting vetiver, and “After” means after planting vetiver for 29 months

Table 3 Comparison of microclimatic characteristics between two ecosystems of pure fruit garden
(Citrus grandis) and fruit-grass complex garden(C. grandis-V. zizanioides)
Observing Ecosystem Soil surface Soil temperature in Air temperature at Relative humidity
date type temperature (_) 20 cm deep (_) 1.5 m high (_) at 1.5 m high (%)
(dd/mm/yy) Max. Min. 8:00 14:00 17:00 8:00 12:00 17:00 8:00 12:00 17:00
13/07/95 Pure fruit garden 44.5 25.0 27.8 32.0 30.6 26.7 34.5 26.6 87 62 93
Fruit-grass 40.5 23.7 26.5 29.0 28.0 25.3 32.5 25.7 91 67 97
complex garden
14/07/95 Pure fruit garden 43.3 23.3 27.8 29.1 27.5 25.8 31.4 24.3 94 69 99
Fruit-grass 39.6 22.3 26.7 27.2 27.0 25.9 30.3 24.3 95 72 100
complex garden

5.2 Recent Applications in China

5.2.1 Garbage landfill
Garbage landfill is the most disgusting place to urban people because it is extremely foul and
poisonous; furthermore, it produces severe on-site pollution and results in extreme degradation of land. In
1997, the first reclamation project for landfill was conducted in the South China Institute of Botany,
which was the first one in China and probably the first one in the world in this respect of VS application
(Xia, 1998). Vetiver grew quite well in the landfill and even better than in other habitats. This is probably
because it could absorb a lot of pollutants from landfill as nutrients. Two years later, the landfill, through
vetiver’s successful rehabilitation, became a very fertile nursery garden (Xia, 2001; Xia et al., 2002).
Afterwards, a far bigger landfill, named Guangzhou Datianshan Garbage Landfill, was partially
rehabilitated with vetiver in the year 2000–2001 by one company in Guangzhou. The aim of the project
was stabilizing embankments of the landfill, preventing leachate from flowing out and abating the
concentration of pollutants in leachate. At present, land reclamation for garbage landfill is conducted in
some places of Guangdong, including Zhuhai, Zhongshan, Maoming, etc. The academic research and
practice of Guangdong indicate that the VS is perhaps the most promising in application of garbage landfill.
5.2.2 Mined land
Apart from landfill, phytoremdiation and rehabilitation for mined land is another main battlefield of VS.
It is well known that metalliferous mining activities produce a large quantity of waste materials, such as
tailings and wastewater. They contain excessively high concentrations of heavy metals and therefore result in
severe pollution problems and lots of land degradation.
The first mine conducting VS in Guangdong is the Lechang Pb/Zn mine located in the north of the
grasses, bahia (Paspalum notatum), bermuda (Cynodon dactylon), Imperata cylindrica, in the mine tailings
was carried out. The result indicates that the height and biomass of vetiver are significantly greater than those
of the other three grasses; moreover, the growth performance of vetiver is the best among the four species (Shu
et al., 2002). Thereafter, a pot experiment coming from Xia and Shu (2001) shows that vetiver has strong
uptake ability to 2 heavy metals, Pb and Zn, stronger than bahia; but it is inferior to bahia with regard to uptake
of Cu (Table 4). In addition, it can be seen from Table 5 that vetiver roots assume a bigger retention capacity to
heavy metals than bahia roots, inferring that vetiver keeps relatively more amounts of heavy metals in its roots
than bahia.

Table 4 Comparison of vetiver and bahia with regard to the ability to absorb heavy metals after they
both grow in a Pb/Zn mine tailings for 130 days
Species Pb Zn Cu
Shoot Root Shoot Root Shoot Root
Vetiver 46.3a (7.1)* 309.5a (23.8) 105.1a (5.0) 380.4a (14.9) 6.9a (0.9) 25.2a (3.7)
Bahia 95.7b (7.6) 218.5b (26.3) 171.8b (23.4) 331.8b (21.2) 18.1b (1.8) 64.2b (9.0)
*Means (with (SD), n=4) followed by different letters in the same column indicate a significant difference at
P=0.01 according to t-test.

Apart from the Lechang Pb/Zn mine, VS has been used to successfully rehabilitate Maoming oil
shale mine tailings and Daboshan iron mine of Guangdong (Xia et al., 2000, Lin et al., 2003). Besides
phytoremediation and revegetation, vetiver has also been utilized to treat leachate draining from mine
lands (Xia et al., 2003; Shu, 2003; Shu and Xia, 2003). The experiments and applications reconfirm that
vetiver is a potential plant for wastewater and leachate purification, especially for removal of heavy
metals or organic compounds from wastewater.
5.2.3 Quarry
Quarries and rocky hills are always “the hardest bone” to eco-restoration. In the last four years, VS
has began to be applied in the field and won success one after another. The earliest vetiver eco-
engineering for quarry revegetation began in 2000. At that time, 2 quarries, Shen’ou and Huada, in
Shenzhen were concurrently restored by 2 private companies (Xia, 2001). In the last two years, a newly-
typed vetiver technique that can make rock headwalls become green quickly was invented jointly by
South China Institute of Botany and Guangzhou Eco Environmental Science and Technology Co. Ltd.
The technique has been accepted and heard as a patent by China National Knowledge Property Bureau
(the application number is 03113672.9). At present, the new technique has been applied in Zhuhai and
Guangzhou for rapid revegetation of quarries, especially for headwalls; its effects are quite remarkable
(Zhang and Xia, 2003). The main reasons why the new vetiver technique can revegetate headwalls
quickly is due to the following aspects. 1) Deep, massive roots can penetrate weathered rocks or grow
deeply down along stone wall; thus vetiver can provide other plants with an effective protection barrier.
2) The extremely strong tolerance of vetiver to drought makes it grow normally in such dry environment
like quarries. 3) Some engineering measures offer a basic framework for vetiver and other plants to grow
on the headwall.

5.3 Application of VS around the Globe

As early as the middle of 1990s, vetiver was used to successfully rehabilitate acid sulfate soils
without any fertilizer, due to vetiver’s extremely strong tolerance to soil Al (68% saturation) and acidity
(pH3.8) (Truong and Baker, 1996). Thereafter, vetiver was also used to rehabilitate various kinds of
contaminated mine lands, including coal, gold, and bentonite mines (Truong, 1998; Bevan and Truong,
2002). For instance, in an attempt to rehabilitate an old coal mine tailings dam with high sodicity and
extremely low N and P contents, five tolerant species were tested: vetiver, marine couch (Sporobolus
complete mortality was recorded after 210 days for all species except vetiver and marine couch. Vetiver
survival was significantly increased by mulching rather than fertilizer application; and furthermore
mulching and fertilizers together increased growth of vetiver by 20 t hm-2, which was almost 10 times
higher than that of marine couch (Truong, 1998).
An experiment conducted in Thailand indicates that vetiver can absorb pesticides (Pinthong et al.,
1998). Thereby, vetiver hedgerows against soil erosion not only save the fertility of cultivable land but
can function as a living filter for capturing unwanted foreign chemicals or contaminants before they reach
non-polluted soil and downstream areas. In fact, the capturing function includes two aspects, uptake of
roots and holdup of hedgerows. For example, Truong et al.(2002) found that vetiver hedges trap 86% of
total endosulfan and 67% of chlorpyrifos in the sediment of runoff water in the first year of growth alone,
and trap 48% of diuron, 73% of N, 52% of P and 55% of S in the second year. The above findings
indicate that vetiver has the potential to offer farmers an additional simple management practice which
will reduce soil movement off-site while reducing the risk of off-site pollution by agrochemicals and
nutrients.
Due to the miraculous effects in erosion control, land reclamation, pollution mitigation, and other
aspects, the Vetiver System has become a key or an effective measure of sustainable development in
some regions of the world (Xia et al., 1998; Booth and Adinata, 2003).

6 THE FUTURE PERSPECTIVE OF VS FOR LAND RELCAMATION IN CHINA

As narrated above, the whole globe is now under unprecedented land degradation and environmental
pollution. China, owing to rapid population increment and economic development, has become one of the
severest nations with special reference to land degradation and environmental pollution.
In China, there has is a large quantity of degraded land. For example, the area of soil erosion is
about3.56_106 km2, accounting for 37% of the country’s total land area. There is 80% of the Loess Plateau
region suffers from soil erosion. The area of desert and desertification is up to 1.49_106 km 2, accounting
for 11.5% of the total land area. The degraded areas of China’s farmland, grassland, forestland, and
freshwater surface are 28_106, 132_106, 31.2_106 , and 0.245_106 hm2, respectively, accounting for
20–30% or so of the respective total areas (Ren and Peng, 2001). In South China only, there are
approximately 5–6 million ha of lands losing their productivity per year.
As early as the 1980s, there were over 8000 national and 230 000 private mining companies in China.
Although parts of illegal private companies were closed in recent years, environmental problems resulted from
mining are still quite conspicuous, which produce 600 million tons of waste materials and destroy 25 000 hm2
of land per year (Qin et al., 2002). Therefore, it is urgent to control the pollution and reclaim the polluted land
resulting from the mining industry.
In China, many cities, including Guangzhou, have formed a situation that garbage or landfill
encloses city. Thereby, urban garbage and its effluent are also problem remains to be solved.
There are at least 13,000 quarries in Guangdong alone waiting for revegetation. At present, the
Guangdong Provincial government has made the decision to close and revegetate large parts of the
quarries.
The past and present experiences have clearly indicated that the Vetiver System is quite appropriate
for solving the above problems occurring in South China. Therefore, the VS exhibits a huge application
perspective in the southern regions of China.

7 CONCLUSION

Land degradation is becoming increasingly severe and extensive in the world. It and soil erosion
usually cause: 1) land and water pollution; 2) poverty and disease; and 3) social instability and even
chaos. The traditional reclamation techniques are expensive and lack of ecological benefits. The newly
ecological reclamation technique for degraded land includes three aspects: phyto-stablization of degraded
land to reduce wind and water erosion; phyto-amelioration of soil to increase soil organic matter and
nutrients; and revegetation of degraded land to vegetatively cover barren land. If the reclaimed land was
mined or contaminated land, two more aspects should be included: utilization of constructed wetlands to
purify heavy metals or other contaminants in wastewater and phytoextraction of heavy metals or other
contaminants from soils. Vetiver grass, due to its unique characteristics, such as higher biomass, fast
growth, strong root system, higher metal tolerance and uptake ability, etc., has been documented to play
an important role in reclamation of degraded land and even realization of sustainable development.
What’s more, this technique is showing a quite promising future around the globe, especially in South
China.

Acknowledgments
Parts of work shown in the paper was supported by Guangdong NSF Group Project (003031). The
authors wish to thank Dr. Paul Truong, the principal soil conservationist of Resource Science Centre,
Department of Nature Resources, Queensland, Australia for providing some reference material and for his
corrections to the paper.

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A Brief Introduction to the First Author

Dr. Hanping Xia (H.P. Xia), a restoration ecologist, is working at the South China Institute of Botany,
Chinese Academy of Sciences. Since 1991, he has been engaged in a wide range of R&D on the Vetiver
System for the purpose of soil erosion control and polluted environment mitigation, including highway slope
stabilization, land reclamation and re-greening, quarry rehabilitation, mine and landfill phytoremediation,
wastewater purification, etc. He creatively initiated “the Vetiver Eco-engineering” from his working
experience of many years. So far he has one monograph and over 30 academic papers in this aspect published.