Richard G. Grimshaw
Asia Technical Department
The World Bank
Washington D.C. USA.
Abstract
The paper summarizes research results and field observations of the use of vetiver
grass, Vetiveria zizanioides, and indicates its use as an important and effective
vegetative hedge that when grown on the contour significantly reduces the flow of sediment
from eroding sites and reduces runoff, both simultaneously, and at a low cost, compared to
more traditional engineered practices. Vetiver grass has unique characteristics. The paper
also sets out evidence that vetiver grass grows over a wide range of site conditions; is
non competitive with adjacent crops; is not a weed; is resistant to pests and diseases; is
used as a fodder for livestock; is used for stabilizing earth embankments, drainage lines,
roads etc.; is fire resistant and is known to repel rodents; and needs minimum
maintenance. The main impediment to extending its use and application is because of poor
technology transfer systems, and the lack of training of farmers and technicians.
Introduction
This paper summarizes the findings of research and the observations of the writer in the
resurgence of the use of vetiver grass as an important technology for sustaining
agricultural productivity in the tropics and semi-tropics. As a result of an early
initiative by the World Bank [1] vetiver grass was re-introduced to development projects
in India as a low cost vegetative system for soil and water conservation. Its use and
potential was further amplified in a number of papers [2, 3, 4, 5, and 6]. This paper is
dedicated to summarizing the findings of a growing number of independent scientists and
users of vetiver grass who, in recent years, have demonstrated the uniqueness of the grass
and its use as a formidable technology for enhancing soil moisture and conserving soil.
Soil fertility maintenance and soil moisture availability are the two most important
elements critical to sustainable agricultural production. The priority given to these two
activities over the past 4,000 years has allowed the Chinese nation to survive and feed
its large population [7], both past and present, whereas other societies have crumbled
because of the failure to maintain these key activities. At a time when a great deal of
attention is being paid to simple low cost technology for sustainable agriculture, vetiver
grass provides one very good, widely and easily applicable technology that is practical,
proven, effective, and profitable.
The Vetiver Grass Technology (VGT), in its most common form, is simply the establishment
of a narrow (less than 1 meter wide) live stiff grass barrier, in the form of a hedge,
across the slope of the land. When applied correctly the technology is effective on slopes
from less than 1 to over 100%. A well established vetiver grass hedge will slow down
rainfall runoff, spreading it out evenly, and will trap runoff sediments to create natural
terraces. All this is possible with out the use of complex hydrological data and design,
and without the aid of high cost consultants and surveyors. It is truly a farmers'
technology, created by farmers; one that went unobserved by most developers and
scientists. Its uniqueness is in the characteristics of the plant.
Methods and Materials.
The hypothesis underlying the use of VGT was set out in a small hand book for farmers, now
in its third edition, "Vetiver Grass (Vetiveria zizanioides). A Method of Soil and
Moisture Conservation" [8 and 9]. The claims that were made for VGT under this first
edition and subsequent editions [10] were at times disputed by scientists, and as a
result, have and continue to be intensively investigated by many scientists and farmers.
This paper draws on these works, and is supported by the authors own observations in
countries in Asia , Africa, Central America and the Caribbean. It describes the results of
the tests and experiments, and cites the authors. In some instances the paper reports on
observations that are not backed by research, but are conclusive for their very existence
under the conditions described.
Results and Discussion.
Claim # 1. A vetiver grass hedge-row is an effective measure for soil and moisture
conservation..
Research at ICRISAT, India [11] compared VGT with stone barriers, lemon grass, and bare
ground (control) under natural (total rainfall 689 mm.) and artificial rainfall
conditions. In all cases VGT was the most effective technology for reducing soil and water
losses. VGT reduced rainfall run off by 57%, and soil loss by over 80%. Their results
clearly showed from the experimental hydrographs the enhanced delay in release of run off
from the vetiver plots, an interesting feature that could be applied as an upper catchment
flood control measure. The same research team [12], confirmed that in the next year
vetiver performed even better. Vetiver shows a distinct improvement in efficiency as the
hedges become older and more dense. At CIAT, Colombia [13], vetiver was compared to other
vegetative systems grown in conjunction with cassava. At 11 months (rainfall 1240 mm.)
vetiver hedges reduced soil loss from 142 tons/ha for bare fallow to 1.3 tons/ha.for
cropped cassava between vetiver hedges Rainfall run off was reduced from 11.6% to 3.6%.
Other researchers have reported similar results. Evidence [14] shows strong positive
correlation between soil loss and water runoff reduction when VGT is applied on black
vertisols in western India, and that VGT is significantly superior to other hedge type
barriers. In Louisiana [15], demonstrations conclusively show the impact of vetiver hedges
on sediment retention. In Malaysia [16] large scale experiments have demonstrated
substantial sediment deposits behind vetiver hedges, in one case of about 1 meter in 1
year.
Farmers have in nearly every case reported favorably on the use of VGT. A farmer [17] has
used vetiver on the family sugar cane farm in Natal, South Africa, for over 70 years as a
means of stabilizing road sides. Since 1989 he has protected 186 ha. of his farm with
vetiver hedges. Erosion losses have been reduced substantially and rainfall runoff was
reduced to the extent that in a very serious drought in 1992 not one of his young lychee
trees was lost. Vetiver grass users in Central America, amongst them those from Honduras
[18], confirm that vetiver hedges are the most cost effective method of soil conservation,
as do users, [19] in Ethiopia, and other African countries. The feedback from 17 farmers
in Layete, Philippines [20], gives clear indication of the impact of VGT and its
superiority over other systems. It should be noted that vetiver grass can regenerate from
stem nodes. This means that as the sediment builds up behind and within the vetiver hedge
to form a terrace, the grass will grow up with the rising terrace - in Fiji terraces with
risers as high as 3 meters have been formed naturally [1] under such conditions.
There is no evidence to show that vetiver grass hedges are inferior to other types of
hedge. To the contrary, evidence suggests that vetiver hedges are the most effective of
all vegetative barriers.
Claim # 2. Vetiver grass will grow over a wide range of site conditions.
Experiments [21] with vetiver under saline and sodic conditions in Australia demonstrated
that vetiver will tolerate high levels of salinity up to ECse of 15 mScm-1 without
appreciable reduction in dry matter yields. Investigations [22] into the tolerance of
vetiver to a range of soil pH have been carried out, and demonstrate the tolerance of
vetiver to pH levels as low as 3.8 with soil Al toxicity levels of 68% - indications are
that vetiver may be one of the most tolerant crop (and pasture?) species to Al toxicity.
It was also demonstrated that vetiver could be established on soils of pH 9.9, and that it
survived well when adequate levels of P and N were supplied. Vetiver grass has been
demonstrated to grow under a wide variety of soil types, depths, and structure. The growth
of vetiver on five different soil types in Malaysia [23] was compared; and although growth
of vetiver differed from one soil type to another, in all cases vetiver grew reasonably
well. It was also demonstrated that vetiver can be established on ex-tin mining land,
leading to the rehabilitation of such degraded land. In India, vetiver grows as strongly
on the black vertisols as it does on the alfasols. Vetiver grows well on upland as well as
wetland conditions, demonstrating its xerophytic and hydrophytic characteristics [23].
Vetiver's cold tolerance limit is around - 9.5� C [24], although some plants have
survived short spells at - 15� C [25].
The greatest constraint to the growth of vetiver is rainfall. It grows in low rainfall
areas of 300 - 400 mm, but requires greater management attention. Under these conditions
it is more difficult to establish vetiver; and due to seasonal extremes, caused by
overgrazing and periodic droughts etc. vetiver, like all other plants, suffers. As a rule
of thumb vetiver will grow under most site conditions throughout the tropics and
semi-tropics. It does best on well drained soils. It will not grow in areas that have
extreme cold during winter months, and where there are perma-frost conditions. Except for
the effect of temperature vetiver will grow at most altitudes. In Honduras [18] vetiver
grows quite well at 2,800 meters. Vetiver hedges have been established [26] in western
Ethiopia at 2,000 m. Vetiver has survived snow conditions at 3,000 meters in Lesotho [27].
Vetiver has high potential for growth in saline areas [28] in Australia, and was
successfully used for the rehabilitation of the derelict sodic Ussar lands of north west
India [6].
Overall evidence points to vetiver tolerating a very wide range of site conditions,
including those that may be considered extremely hostile to plant growth. Vetiver will be
even better adaptable to different sites as accessions are identified that are more
specific to site conditions.
Claim # 3 Vetiver grass is non competitive with adjacent crops.
Most evidence indicates that vetiver does not reduce significantly yield of adjacent row
crops. Experiments [13] in Colombia indicate no yield loss reduction of cassava when grown
with vetiver hedgerows, whereas there was a 33% reduction in yield with elephant grass
(Pennisetum purpureum) hedges. Similar experimental results are demonstrated in
Maharashtra, India [30] and Malaysia[16] and confirmed by farmers from South India to
Fiji. Sugar farmers in Natal, South Africa[17] and Fiji [8] report production gains.
Experiments [31] over the period 1989 to 1991 at Akola, Maharashtra, India, on Lithic
Ustorthent soils under an average rainfall of 840 mm. showed that crops grown in
association with vetiver hedges had superior levels of production. Average total
production was 17.1% and 32.3% higher for crops grown in vetiver protected plots compared
to crops grown in fields with graded bunds and across the slope cultivation respectively.
The highest monetary return was recorded for vetiver associated crops - Rps 6,833 -
compared to Rps 5,969 and Rps 5,065 for graded bunds and across the slope cultivation.
Moisture Use Efficiency was the highest for vetiver plots, as was the level of residual
nutrients. These researchers also compared the effectiveness of vetiver grass with other
vegetative barriers. In all there were four comparisons - Vetiveria zizanioides (Vetiver
Grass), Leuceana leucocephala (Subabul),Cymbopogon flexuosus (Lemon Grass), and
Chrysopogon martini (Tikhada). Yield of seed cotton was 25.5% higher with vetiver than the
untreated control, and compared to 24%, 15%, and 11% for leuceana, lemon grass, and
Chrysopogon respectively. In all cases the highest mean soil moisture percentage, profile
and available moisture storage were recorded for vetiver. Farmers in the Philippines
indicated that corn and rice planted near a Mura (vetiver) hedge row performed better
[20]. A one year only experiment [12] on the red soils at ICRISAT, Hyderabad, India showed
contrary evidence that maize when grown in association with vetiver hedges had a reduced
grain yield, although the total biomass was not effected. Further observations on these
plots may resolve these contradictions, and it may be appropriate to use crops, such as
sorghum and millet, that are more common to the area than maize.
Although in some instances there is evidence of competition with the crop row immediately
adjacent to the vetiver barrier, most experimental results, and overwhelming farmer
reports indicate that there are no negative yield changes, and that to the contrary, most
crops show positive responses to vetiver barriers. It should be noted that vetiver
hedge-rows use up less land than other barrier systems, and thus (all other conditions
remaining equal) the overall yield per unit area can be expected to be higher.
Claim # 4 Vetiver grass is not a weed, it is not invasive.
There is no evidence of vetiver being invasive under upland rainfed conditions [6]. There
is some evidence of natural spreading under swamp conditions [32 and 33]. Nowhere is it
seen as a threatening weed (note this is not the case for other hedge species such as
Leuceana sp. that can become a major weed if not managed properly). Its roots are not
stoloniferous, some of the accessions originating from south India rarely flower, and if
they do the seeds are mostly sterile. Vetiver, probably originating from Guatemala, now
grown in Louisiana has at one site not flowered for 25 years [34]. Vetiver is propagated
vegetatively. In Zambia vetiver hedges at Msamfu Research Station have remained intact for
more than 60 years [8]. One of the main objectives of the National Research Council�s
review [6] of Vetiver was to verify whether vetiver might be a threat as a potential weed.
The review found that in the majority of instances vetiver was not invasive, but it
strongly recommended that only the non seeding accessions be used. Evidence suggests that
accessions from south India are less prone to seeding than those from north India. There
are reports that accessions introduced from India to ARS stations in Mississippi were very
fertile and germinated strongly. This seems not the case of the Le Blanc accessions near
Baton Rouge, Louisiana, nor those of Boucard [35] at Leakey, Texas. More research is
required into the flowering habits of vetiver in relation to cultivar, climate, rainfall,
and day length. Molecular diagnostics [36] linked with rigorous biometric analysis were
used to identify relationships between different vetiver successions. DNA was extracted
from young leaf tissue. It was found that the Boucard accession, and what is known as the
Huffman accession (believed to originate in Guatemala) were essentially the same genotype,
and they were very different from the three accessions received from India. There are
believed to be over 20 accessions of vetiver grass introduced to the United States.
Molecular diagnostics offers a means to identify different accessions and to correlate
positive biological features relevant to the accession. This should result in a more
scientific and controlled use of vetiver with potentially better results.
In Thailand [37] over 30 different accessions of Vetiver have been identified. These
accessions often differ markedly in character and include six accessions of an upland
species of vetiver identified as Vetiveria nemoralis. These accessions include some that
flower, but produce sterile seed, and others that have seed that germinate more freely.
A rather broad conclusion is that at most sites vetiver has rarely been recorded as
invasive, and if germinated seedlings are present, they can be easily removed by
cultivation (the probable reason that farmers never see it as a problem). There are clear
differences in accessions and these differences need better identification so that in the
longer term the most suitable accessions can be identified and matched to site and need.
Claim # 5 Vetiver grass is extremely resistant to pests and diseases.
Vetiver is extremely resistant to insect pests and diseases [23 and 24]. There is evidence
from India [38] that when dead vetiver plant material is effected by termites there may be
an allelopathic reaction that prevents regrowth of vetiver from the center of the plant,
and under severe drought conditions, new young shoots on the periphery of the plant are
grazed out and the plant is killed. Alternatively, and most probably, the termite cast is
too tough for the new young shoots to penetrate. Management by burning may eradicate this
problem. Reports from Brazil [39] suggest that vetiver is resistant to Meloidogyne
javanica and M. incognita race 1 (root knot nematodes), both serious root nematodes in
tobacco. In China there have been reports that vetiver has been effected by rice stem
borer [24], and although this has not effected the growth of the vetiver, the latter might
act as a host plant. However in Fujian (south east China), where vetiver has been grown in
close association with rice for many years, this does not seem to be a problem. In most
cases pests and diseases in vetiver can be best controlled through burning, and as will be
noted later in this paper burning may have an important place in the general management of
vetiver hedges.
Evidence to date indicates that overall, vetiver is resistant to pest and diseases, and is
not seen as a serious host plant.
Claim # 6 Vetiver grass is not eaten by livestock.
Where there are other more palatable grasses vetiver grass is normally ignored by
livestock, this an important feature if the grass hedge is to remain intact for many
years. There has been very little research carried out on the management and feed value of
vetiver as a fodder. It has been observed on many occasions, under farm conditions, that
if the hedge is managed correctly, regular harvesting of young leaves is possible, and
that these young leaves provide a maintenance ration. In Malaysia sheep will not eat
vetiver in the field when there is an abundance of other more palatable species, but cut
tops when fed to penned sheep were readily consumed. In China and Malaysia vetiver has
been successfully fed to grass carp. In eastern Indonesia, under very dry conditions,
vetiver was eaten by cows and horses. Under good management young vetiver leaves have a
nutritive value similar to napier grass with Crude Protein levels of about 7.0%. Under
good conditions high volumes of green leaf are available. In Texas [35] under irrigated
conditions, production of dry matter at more than 100 tons per ha. per annum, equivalent
to about 350 tons of fresh leaf, has been achieved. Reports [40] from China indicated
mulch production from vetiver of 11.4, 14.7, and 17.8 tons of green weight per 100 sq.
meters of hedge row over three consecutive years. Note 100 sq. meters in this case was
equivalent to 230 linear meters of hedge. There is little doubt that with some improved
management vetiver would make an adequate dry season fodder, particularly if combined with
a high protein forage. Farmers at Gundalpet, India, have been using vetiver for centuries
as a field boundary, and for fodder, where during the peak growing season it is cut once
every three weeks. Reports for its use as a fodder come from many other countries
including China, Guatemala, Honduras, Niger, and Mali. Some accessions are known to be
more palatable - i.e. the so called �farmer� cultivar from Karnataka, which had been
selected by farmers over decades as a softer and more palatable cultivar.
In areas where there are more palatable species of forage grass or where livestock are
absent, users who require an inert grass that can be developed with minimum management
should look to vetiver. There are excellent examples of this application demonstrated in
Costa Rica [41] for the protection of mango orchards on steep slopes.
Whether vetiver will be used as a fodder will be determined by the management objectives
of the user. One thing required is the identification and screening of accessions that are
more palatable and manageable as a dual purpose conservation and forage plant.
Claim # 7 Vetiver grass can be used for structural strengthening of earth embankments,
drainage lines, roads, gully control etc.
There is world wide evidence to support the use of vetiver for embankment stabilization
[9, 10, 17, 27, 42]. Vetiver has been used successfully in Malaysia, India, South Africa,
West Indies, and Brazil for stabilization of road sides. Vetiver has been used in
conjunction with geotechnic applications for embankment stabilization in Nepal. It has
been tested successfully [27] to stabilize gold mine slag heaps in South Africa. It has
been used[10, 33] to stabilize flood embankments, river and canal embankments in
Bangladesh. Because its great strength and capacity to absorb shock vetiver has potential
in the stabilization of canal banks against the force and shock of boat wash - hence the
Panama Canal Commission is showing interest in the application of vetiver to the Canal.
The Vetiver Network has received positive reports of vetiver being used to reduce erosion
in small dam spillways in Zimbabwe [39], gullies in Fiji [8], and drainage ways in
Guatemala, South Africa, Malaysia, and Nepal [16, 17, 41, 42]. More recently reports have
been received of vetiver being used for the protection of building sites when located on
sloping land [27].
VGT can be used effectively for the stabilization of irrigation channels [43]. Experiments
using irrigation channels with vertical side slopes compared vetiver on unlined slopes and
vetiver on polyethylene lined slopes. The side slopes planted with vetiver in the
polyethylene lined channels remained vertical, and nearly so in the unlined slopes. The
results indicated the high ability of vetiver to bind the soil (a sandy loam), and the
potential for designing channels with much steeper slopes with the resultant saving in
land area.
VGT has been used in many countries as a very effective means for gully control. Because
of its strength vetiver can withstand high velocity water flows that are normally
associated with gullies, and can grow up and through deep deposits of sediment that are
formed behind vetiver hedges established in gullies. As a result natural steps are formed
in the gullies. Where gabbions are used to stabilize gullies and waterways, vetiver, if
planted in association with the structures will help stabilize them. At sites where high
water velocities can be expected vetiver may best be planted from polybagged planting
material to assure quick establishment, and may in the first year require protection by
sand bags as well as pegging with bamboo stakes.
It is likely that vetiver will be more widely used for embankment stabilization as
engineers become aware of its potential. It has a very important potential in non arable
areas for gully control.
Claim # 8. Vetiver grass is fire resistant and repels rodents and other animals.
Vetiver is well known for its resistance against fire. This resistance has resulted in its
survival in sugar cane fields that are burnt prior to harvesting. In South Africa vetiver
is used to protect forestry firebreaks from erosion [27], and that this method is accepted
by the forest insurance companies. Young burnt vetiver (burnt as a result of a mass of cut
and dried leaf) under Malaysian conditions recovered fully in four weeks [16].
Historically nomadic herdsmen in grazing the flood plains of the Niger River in Mali, West
Africa, have burnt vetiver in order to get a quick flush of grass for grazing. Vetiver's
resistance and quick recovery from burning is primarily due to its protected crown and
from its deep root system and associated nutrient storage that enables quick recovery. It
is these same characteristics that allows fire to be used as a maintenance system for
vetiver in drier areas where large amounts of dry leaf material accumulates in vetiver
hedges, burning �clears� out the hedge and reduces the incidence of termite infestation.
There is conflicting evidence on vetiver's effectiveness to deter rodents and other
animals. Farmers are continually reporting that rats appear to be repelled by vetiver and
do not burrow into the root system. In fact on Nepal's irrigation schemes many farmers
have planted vetiver on their inter-field bunds in order to reduce rat infestation [42].
Recently a forester in Papua New Guinea [44] reported that thus far (3 years), the
notorious bush pigs have not up rooted vetiver grass hedges.
Claim # 9. Vetiver grass needs no maintenance or management
Initially in the dissemination of VGT the claim for minimum or no management was based on
its use in higher rainfall areas such as Fiji and the West Indies. In these areas
experience showed that on cultivated lands vetiver maintained itself well, the only
maintenance being an annual cutting. Following its introduction to less favorable climatic
conditions such as in the semi arid areas of central India (rainfall 500 - 600 mm.) it has
been found that selection of quality planting material, planting at the correct time
(under such climatic conditions the planting window is quite small), gap filling in the
first year or so, planting via the use of polybags (container plants) under extremely
difficult conditions, the use of fire as a management tool to eradicate excess dead plant
material etc., and using different planting techniques to match different site conditions
are all important management aspects that require good practical judgement. Management
experiments [15, 16, 23, and 30] have shown that management plays an important role in the
level of success of vetiver hedges as an erosion control system. There is conclusive
evidence that just �sticking the grass in the soil and forgetting about it" does not
often lead to success, for that matter most technologies fail when this approach is taken.
Studies in Andhra Pradesh [45] and in the Philippines [20] show where farmers have
understood the technology and apply and manage it properly the system is effective. When
government undertakes the work for the farmer,we find the farmer less committed to VGT;
maintenance is not carried out and the hedge system degenerated. On the other hand VGT
applied in Costa Rica [41] in a citrus orchard (free of livestock) showed no signs of
deterioration with no maintenance after five years. Another study [46] shows that on very
small farms (less than 0.5 ha.) farmers are loath to put any barrier across their land as
they take up potential food crop production areas. In such cases we need to be more aware
of farmer practices and encourage farmers to use VGT as a boundary demarcation as has been
practiced for centuries by farmers in Gundalpet in south India, and by thousands of
farmers outside the city of Kano in northern Nigeria.
Claim # 10. Vetiver grass is a low cost and economic system of soil and moisture
conservation.
An economic analysis [3, 47] compared establishing vetiver grass hedges at less than $30
per ha. with more than $500 per ha. for conventional engineered systems. Economic rates of
return for the latter are around 20% compared to more than 90% for vetiver. The costs of
establishing vetiver hedges varies from site to site. On gentle sloping lands vetiver
hedges may be established 50 meters apart, and thus only 100 meters of hedge per ha. of
protected land is required. On steep lands of 60% the distance between hedges may be 4
meters or less, requiring 2,500 meters of hedge per ha. The cost of planting material
varies depending on how it is produced. It will cost more if propagated by hand in a
commercial nursery, less expensive by mechanized methods, as done by the Boucard brothers
in Texas, and even less if existing farm hedges are divided for replanting as new hedges.
In India a farmer can dig and plant 200 meters in a day - cost $3 per day. �Commercial�
vetiver nursery enterprises in India were paid in 1987 about Rupees 0.01 per planting
slip. At three slips per hole planting material would cost about Rupees 300 (US $ 10 per
km. of planted hedge). In Thailand good quality bare rooted �slip producers� are paid in
1993 US$ 2,600 per ha. which at 1.25 million slips per ha. is equivalent to US 0.2 cents
per slip or US$ 60 per km. In Thailand polybag vetiver is produced and planted at US 62
cents per meter. The mechanized cost [35] of planting of vetiver, including cost of
planting material, is estimated at about US $175 per mile. In the USA protecting 1 ha. of
land on a 4% slope would, using six lines of hedge-row, cost about US $ 90.
Benefits from using vetiver grass hedges are less easy to determine. In most instances
soil loss is quickly and permanently reduced, reductions of erosion losses from 143 tons
to 1.3 tons per ha. in one year are not uncommon [13]. Short term yield gains have been
demonstrated in India [31] resulting in estimated Benefit Cost ratios of more than 2:1.
Some farmers in India have reported no crop loss in drought years when using vetiver,
whilst their neighbors have lost their unprotected crops. Other benefits that should be
quantified include the value of vetiver as a mulch (in China US 2 cents per kg), as a fuel
(vetiver has an energy value of about 55% of that of coal), and as a fodder. Indirect
benefits include value of otherwise lost soil and soil nutrients, value of increased
ground water recharge, its value in upper catchment flood protection and reduced
maintenance cost of embankments. If one assumes the benefits between engineered systems
and vetiver grass to be the same (which they are not - vetiver�s being superior) then the
low cost of vetiver compared to engineered systems (about one fifth) should rank VGT as a
priority technology. Detailed costs of vetiver hedge development [3] show its superiority
over other systems, including engineered structures, in terms of benefit cost ratios.
Conclusions
The foregoing establishes strong evidence that vetiver meets the requirements of a long
term, low cost, vegetative technology for soil and moisture conservation as set out in the
first edition [9] of the handbook �Vetiver Grass (Vetiveria zizanioides) A Method of
Vegetative Soil and Moisture Conservation�. The proof not only rests in the above
experimental results but by an expanding group of users around the world who seem to be
voting �aye" by including VGT as part of their farm management practices. Nowhere is
this more vividly demonstrated than the mass introduction of VGT in Thailand [37, 48] over
the past two years. Educating farmers in soil conservation is a slow process and needs to
be accelerated. Vetiver grass is one of a number of tools that can be used in conjunction
with other methods (contour tillage, no-till, appropriate nitrogen fixing cover crops
etc.) to reduce soil erosion. Vetiver has special merit in its characteristics as a
durable, relatively inert, and highly effective grass that when grown as a hedge halts
sediment flows and reduces rainfall run off.
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