This chapter presents 22 of the concerns most commonly raised about vetiver, together with what seem to be the best available answers. These pages reflect the general state of knowledge in the early l990s. They result from reviews and comments collected from a dozen experienced vetiver specialists and a dozen vetiver skeptics.
Will Vetiver Stop the Loss of Soil?
The accumulation of experiences worldwide is convincing: vetiver hedges can indeed block the passage of soil. They may not stop a hillside from slumping, but they can keep topsoil on site and, over time, retard most surface erosion. In many cases they can also help fill up gullies.
With the experiences of India, Fiji, China, Malaysia, St. Lucia, St. Vincent, South Africa, Malawi, the United States, Haiti, and other nations, it can be said with confidence that hedges of this deeply rooted perennial are indeed capable of catching eroded soil and helping to build up terraces that stabilize the site. Moreover, they seem capable of doing so under many conditions except where freezing occurs. The actual amount of erosion controlled on any given site cannot now be predicted with confidence, but, at least in some cases, the reductions can be dramatic.
It should be understood that, in a strict sense, vetiver doesn't stop erosion. The soil between the hedges is still free to move. However, the hedges block its further progress and prevent it from leaving the site.
Although it has the power to hold back soil, there are undoubtedly sites where vetiver will fail: climates may be too dry or too cold, slopes may be too steep or too boulder-strewn, or soils too toxic or too shallow, for example.
Is It Safe?
Vetiver is already so well known in so many countries that any serious threat from its use for erosion control would by now be obvious and widely reported. However, there are fertile types in India that could become hazardous if they are distributed.
A major reason for confidence in vetiver's safety is that the plant will seldom have to be introduced anywhere. It is already found throughout the tropics and has been there for at least a century. Apparently it has never spread in an uncontrolled manner or become a major nuisance. Possibly, such difficulties may be found as people investigate this plant more thoroughly, but, by and large, vetiver has not become a problem.
It is important, however, that only the right kind of vetiver be used. The types of South Indian origin apparently produce nonviable seeds and must be maintained by vegetative methods. Luckily, this is the fragrant-root type that has been spread throughout the tropics. In areas where it has been planted for decades, or in some cases for more than a century, it has seldom (if ever) spread from seed. In a few areas vetiver is reported as an escape, but even there it neither spreads rapidly nor is considered a nuisance.
On the other hand, types of vetiver grown from seeds introduced from northern India into the United States in 1989 have formed seeds and have germinated in areas adjacent to small plots in Georgia. This fertile type should not be introduced to new areas. It has long been used to protect canal banks in irrigated agriculture in northern India and the neighboring Terai of Nepal without becoming a pest or spreading uncontrollably from seed. Nonetheless, at this time, because of its potential hazard, only vegetative materials should ever be planted. Vetiver must never be propagated from seed.
Does Vetiver Reduce Runoff Water?
Yes, although by how much will depend on local conditions and is not now known.
A key claim for the vetiver system is that contour hedges of this grass can slow down and hold back moisture that would otherwise rush off and be lost to the slopes. This claim appears to be valid. For example, in Karnataka, India, farmers who plant vetiver can dig behind their hedges and find moist soil when their neighbor's land is parched. Similar observations have been made elsewhere. In many areas, this ability to hold moisture on the slopes, and thus increase infiltration, will likely boost crop yields and appeal to farmers, foresters, and civil authorities.
On the other hand, vetiver is not a barrier in the sense of being like a wall. Its hedges are more like tight filters laid across the land: they slow down runoff and retard its progress, but do not physically dam it up. Shallow runoff seeps through the lower part of the hedge; deeper runoff pours through (or even over) the upper parts. In this way, runoff is neither ponded nor concentrated but stays spread across the slope as it fell. The vetiver method contrasts with rock walls, dirt barriers, and other mechanical methods that hold, concentrate, or divert water off site.
Vetiver supporters see this ability to keep the water spread out across the slopes as a major advantage. They are probably right, at least for most locations. Much of today's most dramatic erosion is caused when runoff concentrates and scours out the land in "gully washers."
Will Farmers Adopt Vetiver?
In most places, yes-but not everywhere.
This simple, cheap, and easily understood way to control soil losses should be highly acceptable to farmers, foresters, and other potential users throughout the warm parts of the world.
For one thing, vetiver is not demanding. Its hedges are seldom more than 1 m wide and therefore take up little land. It generally requires relatively few plants to establish the hedges. It can be installed by farmers using their own labor and materials. It requires little or no maintenance once established, and the hedges can last for years.
For another, there are incentives for farmers to use vetiver. In most cases, the hedges will guide the bullock, the tractor, or the hoe along the contour. The resulting contour farming alone will likely conserve soil and improve moisture, and thereby give better yields, healthier plants, quicker growth, and more resistance to droughts and other hazards.
The appeal to self-interest could be powerful, obvious, and rapid; however, it is likely that certain farmers will resist the vetiver technique. Some will have farms so small that they cannot afford even the tiny strips occupied by vetiver hedges. Some will have narrow farms running up and down the slope (a common way of subdividing land among family members in some locations) so that hedges across the slopes would make plowing and other operations impractical or inconvenient. And some will care little for the land or its future (they may, for example, be tenant farmers, resentful of the landowner).
Will Farmers Dig Up Their Hedges?
One criticism leveled against vetiver relates to the fact that its roots are worth money. Farmers, the critics charge, will dig up their hedges whenever cash becomes more important to them than erosion, which is to say almost always.
Reportedly, farmers have already dug up vetiver erosion hedges at least once in both Indonesia and Haiti. However, although such experiences will inevitably occur again, they will undoubtedly be few, far between, and seldom repeated. There are three major reasons for this:
· Difficult harvesting. Vetiver roots are threadlike strands that form lacy networks throughout a large volume of soil. To obtain the roots in quantity, therefore, vast amounts of dirt must be dug. Except in loose, light soils, the workload is enormous, especially considering the small amount of root obtained. Even in volcanic ash and sandy bottomlands, the task of digging vetiver roots is so difficult that it is often hard to find people willing to do it.
Also, separating the soil from the intricate roots involves
extreme drudgery. Commercial production is usually done only near waterways
where the soil can be washed off.
· Lack of markets. The total world demand for vetiver oil is only about 250 metric tons per year (see sidebar, page 78). Moreover, there is little or no "elasticity" in the market, and the prospects for anyone to sell larger supplies are poor. Indeed, demand has been declining in recent years, and existing producers are more than capable of meeting any likely rebound. Currently, organized production is found in only three countries: Haiti, Indonesia (actually, only Java), and the tiny Indian Ocean island of Reunion. It is unlikely that they can be undercut because production costs in Indonesia and Haiti are probably as low as could be achieved anywhere. Further, the world's vetiver-oil buyers have contracts and relations with the traditional producing nations; they are therefore unlikely to turn to a new supplier without extraordinary financial or oil-quality inducements.
· Lack of facilities. To extract the oil from the roots is not easy or cheap-it demands a steam-distillation facility. Such a relatively expensive factory is unlikely to be an attractive investment in areas that don't already have one.
Does Vetiver Affect Adjacent Plants?
The answer is not clear. Depending on the crop and the level of stress at the site, some edge effects will undoubtedly be noted. However, neither vetiver nor its roots are inherently spreading, and in most cases, the effects should be minimal.
In theory, vetiver should compete with immediately adjacent plants for the use of water and nutrients, but in practice it doesn't seem to. Some yield reduction has been observed in the rows nearest the hedges in certain crops at certain sites (maize in India, for example). However, whether this results in an overall decrease in yield is as yet unclear- gains from the improved moisture levels across the whole field may well offset the losses at the upper and lower edges.
Certainly in some cases (cotton fields laced by vetiver hedges in South India, for example), no obvious edge effects are seen; the plants beside the hedges are as tall and productive as those elsewhere across the field. Perhaps this is because topsoil and organic debris washing off the fields accumulate behind the hedges and overcome any competition from the grass.
Is Vetiver Prone to Pests and Diseases?
No, but certain diseases and one potentially serious pest are known. In future these or other organisms might restrict the plant's usefulness to certain locations or climatic zones. Also, they might increase the need for the care and maintenance of the hedges.
Although vetiver plants are usually remarkably free of disease, several fungi have been identified in a few locations. For example, two smuts and a leaf blight (Curvularia trifolii) have been identified on vetiver plants in Bangalore, India. In Malaysia, three fungal diseases (tentatively identified as species of Nigrospora, Curvularia, and Helminthosporium) have been observed, but they do not appear to be virulent.
As for pests, a potentially nasty stem borer has been found in China. A severe but localized infestation of Eupladia grubs has been found in Africa. And termites are known to attack the dead stems, a particular problem in dry areas. None of these insects, however, seems to be a devastating threat to the plant's worldwide use.
Is Its Soil Adaptability as Broad as Claimed?
Vetiver's edaphic limits are unknown, and there are undoubtedly sites in which it will not grow. Nonetheless, the plant seems to tolerate a remarkable array of soil types.
There are well-documented examples where vetiver is growing in very adverse soils. For example:
· Coastal sand dunes in South Africa.
· Extremely acid soils (with pH as low as 4.0) in Louisiana.
· Highly alkaline soils (pH up to 11) at Lucknow, India.
· Black cotton clays (which heave and split and eject most plants) in Central India.
· Barren soils with little fertility or organic matter in South China and other places.
· Waterlogged soils in the black cotton clays, and even swamps, of India.
· Parched land. In the arid state of Rajasthan, India, vetiver is common.
· Saline soils in Australia.
Although vetiver can survive on many hostile sites, it should not be expected to grow there with its full vigor. On many poor soils the plant will probably be difficult to establish, its growth will be retarded, and its ability to form a hedge to catch erosion will be long delayed. Some fertilization will often be required on such sites to create and maintain fully functioning hedges.
What Range of Climates Can the Plant Withstand?
Details are unknown, but vetiver's climatic limits seem to be remarkably broad. The plant, however, cannot reliably withstand freezing conditions.
Heat seems to be no barrier. Vetiver is reported to grow vigorously under some of the most torrid conditions faced by farmers anywhere.
On the other hand, vetiver is definitely limited by cold. It can take a mild freeze, but even this may be misleading. An erosion-control barrier must be able to function for years to be reliable; should a hedge die with even infrequent cold snaps, all the soil accumulated behind it would be left vulnerable.
From experiences in New Zealand and southern England, it appears that vetiver will succeed only where the sun is hot and bright. Maritime temperate locations may prove too cool and cloudy for the hedges to form up quickly.
Aren't There Other Species that Can Do the Same Job?
So far, no other plant with all of vetiver's major qualities has been found. However, some have certain of its qualities.
It would be most desirable to have additional species to use in narrow vegetative barriers. They could extend the geographic range of hedgerow erosion control, give farmers more options, and provide substitutes for vetiver should it ever get struck down by epidemic disease.
Effectiveness of other species is also a management question. Napier grass might be as efficient as vetiver if kept as a much wider hedge, but it would require significantly more care, expense, and labor-as well as replanting every few years.
Isn't It a Threat to Have Erosion Control Based on a Monoculture?
Yes. At present, however, there seems to be no alternative for use in narrow hedgerow barriers against erosion.
The job vetiver can do is so important that it would be absurd not to take advantage of it just because some unknown disease may possibly break out in future. Research should be maintained on alternatives (see Appendix B), but vetiver is currently the only practical species for low-maintenance, single-plant hedgerow erosion barriers.
Although the vetiver found almost everywhere in the tropics is the same species, it has been scattered in myriad locations for a long time, and it is possible that the germplasm is not as genetically uniform as might appear.
Will the Plant Foster Diseases or Pests that Might Attack Crops?
Perhaps, but there is no evidence for it at present.
Vetiver belongs to the same subtribe of the grass family as maize, sorghum, lemongrass, and citronella. It is therefore not unexpected that it will be susceptible to some of the same maladies. A more serious fear, however, is that bands of this perennial across the fields might act as sources of infections that damage the crops.
To date, no one has reported that vetiver hedges can act this way. They of course take up only a small area and are unlikely to produce massive populations of pests even in the worst of cases. Thus, although they may provide cozy places for pests to overwinter, the probability of serious problems seems slight. It is likely, also, that management practices (such as periodically burning and topping the hedges) will further minimize any threats.
Is Vetiver Sterile?
Certain types appear to be sterile in that they do not spread under normal circumstances. However, whether they produce truly sterile seed or whether they germinate only under special and unusual conditions is not clear.
It is legitimate to fear that any grass belonging to vetiver's subtribe could become a weed. Others have become so: shattercane and Johnson grass are just two examples. But the South India form of vetiver is not considered a weed in the dozens of places where it has been planted around the world. Also, the weedy members of the subtribe tend to be annuals. The perennials, such as vetiver, show a marked tendency toward low seed-set and an absence of female flowers. This makes them less aggressive.
It is important, however, that any vetiver planted be of the South India type. This is the type now spread widely through the tropics. As previously noted, a second type growing wild in North India is flowering and fertile and produces seedlings under conditions of high humidity and high soil moisture.
Although in one or two cases even the "sterile" vetiver has been declared a weed, it was a mild nuisance rather than a spreading terror. In hundreds of locations, the plant is considered benign at worst and highly beneficial at best. Indian farmers, for example, do not see it as a weed, even where it has been on their farms for centuries.
Generally, vetiver grows only where people plant it.
How Long Will a Hedge Last?
Vetiver is a perennial and, at least in some locations, hedges formed from it seem capable of surviving for decades.
This grass is remarkably persistent. On the island of St. Vincent in the Caribbean, vetiver barriers have been used for 50 years and some are still active even without maintenance. On an experiment station in northern Zambia, vetiver is reportedly still in the same lines that were planted 60 years ago. Some boundary strips in vetiver's native region of India are purported to be at least 200 years old.
Do Vetiver Hedges Require Maintenance?
There are mixed reports on this, but probably a rough trimming every year or two will be needed to keep most hedges in the best operating condition.
Although vetiver stays in place without requiring attention, it tends to break up into clumps if not trimmed. This usually takes a long time, however. Fiji's sugarcane fields offer an example where hedges given little or no maintenance produced excellent results for more than 30 years.
On the other hand, it is reported in St. Lucia that the hedges get rough and ragged unless they are periodically trimmed. One hedge in St. Lucia showed some gullying where gaps had formed, but it had been abandoned for probably more than 30 years. In addition, the flat surface of the terrace showed signs of sheet erosion (rocks on top of the soil) because water had drained too fast through the thinned hedge.
Trimming the hedges is usually not difficult. Generally, farmers merely run a plow along the edge to cut off any spreading tillers and cut back the tops with a machete. The effort can provide at least small amounts of forage, mulch, animal bedding, or thatch.
Is It Expensive?
The vetiver method is inherently low cost.
Compared to terracing, bunding, or land leveling, vetiver is very inexpensive. In the red soils area of China, for example, the mechanical techniques cost, on average, $900 per hectare; vetiver, by contrast, costs less than $200. A similar ratio has been measured in India, where the cost for bunds was $60 per hectare and for vetiver less than $20 per hectare.
These figures were for initiating a vetiver program. They include costs for nurseries, the production of planting materials, the planting process itself, and perhaps some early maintenance (watering, fertilizing) to give a hedge a head start. As the critical mass of hedge builds up, the farmers obtain planting material from their own plots at no cost.
Once established, the hedge requires little or no expense. Constructed soil-conservation measures, on the other hand, require constant, and sometimes extremely costly, maintenance.
When the whole system is taken into account, vetiver in many places may more than pay for itself in improved crop yields. Yield increases of 25-60 percent have been recorded for contour cultivation of cotton, sorghum, and other crops in India.
Is It Easy to Establish?
In most places in the tropics it should be easy to establish vetiver hedges. In some, however, careful tending and perhaps years of delay will be required before the hedges are fully serviceable.
Vetiver is easily planted by hand, but machines (tobacco- or vegetable- or tree-seedling planters, perhaps) could also be used. The main work is to break up sprigs and to set them in the soil.
Any shortage of planting materials will, in most cases, be temporary. Over the years, a little patch of nursery can produce planting materials that can cover vast areas. Under irrigation and fertilization, a single hectare of nursery can, within a few months, provide enough slips to plant about 150 km of hedgerows, which, depending on slope, could protect up to 450 hectares.
Although vetiver establishes amazingly well where conditions are at least moderately favorable, delays and disappointing results can occur where conditions are difficult. For example, it requires good management to get vetiver established in very dry areas. Here, several years may pass before the plants have grown together to form tight hedges.
Must the Hedges Be Unbroken?
Whereas a gap in an earth bund is catastrophic because the impounded body of water pours through, a vetiver hedge is not a solid barrier and it need not be perfect to work. Because the hedge filters water and doesn't dam it or divert it, it is tolerant of an odd gap. Nonetheless, a continuous hedge is desirable, and there are some reports of "gappy" hedges exacerbating erosion by channelling the water.
It is tolerant of other imperfections as well. For example, the hedge need not be exactly on the contour nor have perfectly even growth. Any low points will tend to gather more soil and trash and therefore will respond with more sediment accumulation, eventually forming a level terrace. Bunds and berms, on the other hand, must be on the exact contour because they function by damming or diverting the runoff water.
Wouldn't a Plant with More Uses be Better?
Maybe, in some situations.
Some have said that to be acceptable to farmers, any erosion-blocking plant should be more palatable to animals. That way, they say, people will put in the hedges to feed their livestock. Without some such incentive, they claim, farmers won't respond.
We are not convinced of this argument. Indeed, if a grass barrier is too palatable to livestock, it may lose its effectiveness. Animals are found almost everywhere in Third World countries, and wildlife or livestock will reduce an edible erosion barrier to ground level, especially in the dry season when feeds are in short supply. The advantage of vetiver, however, is that once it is established, livestock do not affect its usefulness.
Actually, though, vetiver yields several products that can be sold without damaging its effectiveness; for example, its stems and leaves can be used for making ropes, hats, brushes, thatch, mats, and fuel. They also make excellent mulch and animal bedding. In some places, vetiver is an important medicinal plant and, although the whole plants are shunned by animals, young vetiver leaves are palatable to livestock and can be used as feed.
Does Vetiver Cause Erosion?
It may seem ironic, but it is nonetheless true that vetiver cultivation is barred from certain parts of Indonesia solely because it "causes soil erosion." This had led several people to denounce all efforts to promote the wider use of vetiver. After all, they point out, more vetiver is grown for oil in Indonesia than anywhere else except Haiti; surely Indonesians must know the plant and its performance.
Closer inspection, however, shows that the culprit is not vetiver itself but the specific way farmers grow and harvest it there. It is so difficult to dig up the roots that the plants are grown in special sites where the soil is extremely light. Only there can the farmers obtain the roots with a reasonable effort. When the time comes, they rip the plants out, leaving behind trenches of loose dirt that could hardly be more erodible if designed for the purpose. Some farmers even place their rows up and down (rather than across) the slopes. This allows the rain to scour the land in an even more disastrous manner.
When vetiver hedges are established on the contour and left in place, there is no evidence that they cause erosion.
Is It Difficult to Get Rid of?
Vetiver is easily killed by slicing off the crown with a shovel or other implement. It is also easily eradicated by systemic herbicides. It is so easy to remove that in some places it is used in crop rotations as a fallow crop.
Why Hasn't Vetiver Been Widely Used Before?
We don't know why.
Over the past 50 years, the main approach to worldwide erosion control has been oriented toward engineered systems, such as terraces, bunds, or contour drains. The use of vegetative systems is generally not attractive to conservation specialists trained in engineering techniques.
Another major approach worldwide is the use of cultural systems such as crop rotations, contour planting, ridge planting, and mulches. Erosion-control hedge technology has been lying dormant.
Vetiver belongs to the same part of the grass family as maize, sorghum, sugarcane, and lemongrass. Its botanic name, Vetiveria zizanioides (Linn) Nash, has had a checkered history-at least 11 other names in 4 different genera have been employed in the past. The generic name comes from "vetiver," a Tamil word meaning "root that is dug up." The specific name zizanioides (sometimes misspelled zizanoides) was given first by the great Swedish taxonomist Carolus Linnaeus in 1771. It means "by the riverside," and reflects the fact that the plant is commonly found along waterways in India.
For a plant that grows so well on hillsides, vetiver's natural habitat may seem strange. It grows wild in low, damp sites such as swamps and bogs.
The exact location of its origin is not precisely known. Most botanists conclude that it is native to northern India; some say that it is native around Bombay. However, for all practical purposes, the wild plant inhabits the tropical and subtropical plains throughout northern India, Bangladesh, and Burma.
THE TWO TYPES
It is important to realize that vetiver comes in two types-a crucial point because only one of them is suitable for use around the world. If the wrong one is planted, it may spread and produce problems for farmers.
The two are:
· A wild type from North India. This is the original
undomesticated species. It flowers regularly, sets fertile seed, and is known as
a "colonizer." Its rooting tends to be shallow, especially in the damp ground it
seems to prefer. If loosed on the world, it might become a weed.
· A "domesticated" type from South India. This is the vetiver that has existed under cultivation for centuries and is widely distributed throughout the tropics. It is probably a man-made selection from the wild type. It is nonflowering, nonseeding (or at least nonspreading), and must be replicated by vegetative propagation. It is the only safe type to use for erosion control.
It is not easy to differentiate between the two types-especially when their flowers cannot be seen. Over the years, Indian scientists have tried to find distinguishing features. These have included differences in:
· Stems. The South Indian type is said to have a thicker
· Roots. The South India type is said to have roots with less branching.
· Leaves. The South India type apparently possesses wider leaves (1.1 cm vs 0.7 cm, on average)
· Oil content. The South India type has a higher oil content and a higher yield of roots.
· Physical properties. Oil from the wild roots of North India is said to be highly levorotatory (rotates the plane of polarized light to the left), whereas that from the cultivated roots from South India is dextrorotatory (rotates polarized light to the right).
· Scent. The oils from the two types differ in aroma and volatile ingredients.
Whether these differences are truly diagnostic for the two genotypes is as yet unclear. However, at least one group of researchers consider that the two vetivers represent distinct races or even distinct species. Perhaps a test based on a DNA profile will soon settle the issue.
Like its relatives maize, sorghum, and sugarcane, vetiver is among the group of plants that use a specialized photosynthesis. Plants employing this so-called C4 pathway use carbon dioxide more efficiently than those with the normal (C3 or Calvin cycle) photosynthesis. For one thing, most C4 plants convert carbon dioxide to sugars using less water, which helps them thrive under dry conditions. For another, they continue growing and "fixing" carbon dioxide at high rates even with their stomata partially closed. Since stomata close when a plant is stressed (by drought or salinity, for instance), C4 plants tend to perform better than most plants under adversity.
The vetiver plant is insensitive to photoperiod and grows and flowers year-round where temperatures permit. It is best suited to open sunlight and will not establish easily under shady conditions. However, once established, plants can survive in deep shade for decades. They tolerate the near darkness under rubber trees and tropical forests, for example.
In its general aspect a vetiver plant looks like a big, coarse clump grass-not very different from pampas grass, citronella grass, or lemongrass. It can, however, grow to be very tall. Under favorable conditions the erect stems (culms) can reach heights of 3 m.
For purposes of erosion control, vetiver has a number of singular architectural and anatomical features:
· Habit. The plant has an erect habit and keeps its leaves
up off the ground. This seems to be important in allowing the hedge to close up
tight, and it also allows crops to be grown next to the plant.
· Resistance to toppling. Unlike many grasses, vetiver is "bottom heavy." It shows no tendency to fall over (lodge), despite its very tall culms.
· Strength. The woody and interfolded structures of the stems and leaf bases are extremely strong.
· Year-round performance. Although vetiver goes dormant during winter months or dry seasons, its stems and leaves stay stiff end firmly attached to the crown. This means that the plant continues stopping soil, even in the off-seasons or (at least for some months) after death.
· Self-rising ability. As silt builds up behind a vetiver plant, the crown rises to match the new level of the soil surface. The hedge is thus a living barrier that cannot be smothered by a slow rise of sediment. Like dune grasses at the beach, it puts out new roots as dirt builds up around its stems.
· "Underground networking." Vetiver is a sod-forming grass. Its clumps grow out, and when they intersect with neighboring ones they intertwine and form a sod. It is this that makes the hedges so tight and compact that they can block the movement of soil.
· Clump integrity. For all practical purposes, vetiver has no running rhizomes or stolons (Actually, it does have small rhizomes, which, because they are folded back on themselves, don't run outwards in the normal manner). This, too, helps keep the hedge dense and tight. The clumps do not readily die out in the center. Unlike most other clump grasses, even old vetiver plants seldom have empty middles (This is especially the case if they have been periodically topped).
The crown of the plant is generally a few centimeters below the surface of the ground. It is a "dome" of dead material, debris, and growing tissue, much of it a tangled knot of rhizomes. These rhizomes are very short-1 cm or less-and are often turned back on themselves. It is apparently for this reason that vetiver stays in clumps and does not spread across the land.
To separate the slips for planting, the often massive crown is cut apart. It is sometimes so huge that it has to be pulled out of the ground with a tractor and cut up with axes. In nurseries, however, young slips are easily separated.
Leaves and Stems
It is, of course, the leaves and stems that are crucial in this living-hedge form of erosion control. Vetiver leaves are somewhat like those of sugarcane, but narrower. Although the blades are soft at the top, the lower portions are firm and hard.
On some vetiver types the leaves have edges sharp enough to cut a person. Actually, this is due to tiny barbs. There is a lot of variability, however: some plants are fiercely barbed, some not. The ones used for oil and erosion control tend to be smooth edged. Topping the plants is an easy way (at least temporarily) to remove the bother of the barbs.
The leaves apparently have fewer stomata than one would expect, which perhaps helps account for the plant withstanding drought so well.
It is the stems that provide the "backbone" of the erosion-control barrier. Strong, hard, and lignified (as in bamboo), they act like a wooden palisade across the hill slope. The strongest are those that bear the inflorescence. These stiff and canelike culms have prominent nodes that can form roots, which is one of the ways the plant uses to rise when it gets buried. (It also moves up by growing from rhizomes on the crown.)
Throughout their length, the culms are usually sheathed with a leaflike husk. This possibly shields them from stresses-salinity, desiccation, herbicides, or pestilence, for example.
The flower (inflorescence) and seedhead are very large: up to 1.5 m long. Both are brown or purple in color. The flower's male and female parts are separated. As in maize, florets in the upper section are male and produce pollen; in vetiver, however, those below are hermaphrodite (both male and female).
Perhaps most basic to this plant's erosion-fighting ability is its huge spongy mass of roots. These are not only numerous, strong, and fibrous, they tap into soil moisture far below the reach of most crops. They have been measured at depths below 3 m and can keep the plant alive long after most surrounding vegetation has succumbed to drought.
The massive, deep "ground anchor" also means that even heavy downpours cannot undermine the plant or wash it out. Moreover, because the roots angle steeply downwards, farmers can plow and grow their crops close to the line of grass, so that little cropland is lost when the hedges are in place.
The roots can grow extremely fast. Slips planted in Malaysia produced roots 60 cm deep in just 3 weeks .
One of vetiver's great benefits, of course, is that once it is planted it stays in place. It is therefore not pestiferous and seldom spreads into neighboring land.
Actually, though, seeds are often seen on the plant. Why they fail to produce lots of seedlings is not known. Perhaps they are sterile. Perhaps they are fertile but the conditions for germination are seldom present. Or perhaps people just haven't looked hard enough.
Under certain conditions some seeds are indeed fertile. These conditions seem to be most commonly found in tropical swamps. There, in the heat and damp, little vetivers spring up vigorously all around the mother plant.
Vetiver is an "ecological-climax" species. It outlasts its neighbors and seems to survive for decades while (at least under normal conditions) showing little or no aggressiveness or colonizing ability.
The oil emits a sweet and pleasant odor. It is used particularly in heavy oriental fragrances. Although primarily employed as a scent, it is so slow to evaporate from the skin that it is also used as a fixative that keeps more volatile oils from evaporating too fast. Because it does not decompose in alkaline medium, vetiver oil is especially good for scenting soaps. In at least one country it also serves as a flavoring, primarily to embellish canned asparagus or sherbets.
The oil in vetiver roots has a pleasant aroma. The perfumery industry describes it as "heavy," "woody," or "earthy" in character. It is obtained by steam distilling the roots and is used in fine fragrances and in soaps, lotions, deodorants, and other cosmetics. Occasionally its scent dominates a perfume, but more often it provides the foundation on which other scents are superimposed.
Haiti, Indonesia (actually only Java), and Reunion (a French island colony in the Indian Ocean) produce most of the world's vetiver oil. China, Brazil, and occasionally other nations produce smaller quantities. Reunion produces the best oil, but Haiti and Indonesia produce the most. Haitian oil is distinctly better than Indonesian and not far behind the Reunion oil (known in the trade as "Bourbon vetiver") in quality.
Although reliable statistics are unavailable, world production of vetiver oil is currently about 250 tons a year. Annual consumption is estimated to be:
It seems unlikely that demand will increase beyond these figures, even to match population growth. In recent decades, the international perfumery industry has generally decreased its use in new products. This decision was taken primarily because Haiti manipulates the price of its oil, Indonesia's oil is indifferent and variable in quality, and Bourbon oil is expensive. A completely synthetic vetiver oil cannot be manufactured at a realistic price, but alternative materials such as cedarwood oil can be substituted. For these reasons, world vetiver-oil consumption is likely to remain roughly at current levels.
Also, some countries have given up producing vetiver oil. For example, Guatemala, which was once an exporter, no longer produces any (even for local use), and Angola (until the early 1970s a regular supplier to the international market) has given up as well.
Adapted from S.R.J. Robbins, 1982 Some Ingredients in Vetiver Oil
American Vetiver Oil
The United States is not known as a vetiver-oil producer, but as this book was about to be printed we learned that Texas farmers Gueric and Victor Boucard are perhaps the most advanced vetiver growers of all. Since 1972, the Boucards and their late father have been designing implements to plant, harvest, and process vetiver for its oil. These days the Boucards grow the crop on as much as 40 hectares (depending on market prices). All the necessary steps- from large-scale nursery operations to digging to roots-are mechanized. (A modified rock-picker has proved ideal for tearing up the roots.)
To us, the surprising thing is that the grass survives in this far-from-tropical location (nearly 30°N latitude and above 500 m). However, Gueric Boucard indicates that this is no problem: "I just cut them off near the ground each fall," he says, "and they have survived temperatures down to -7°C winter after winter, and one cold snap below -12°C for several hours."
As already noted, the dried roots are used in India to prepare the traditional "khus-khus" screens. When moistened, these both cool and scent the air passing through, and they are believed to protect people against insect pests as well.
The oil occurs primarily in the roots, but traces of it in the foliage may nonetheless account for the plant's inherent resistance to pests and diseases. The oil is known to repel insects, for example. People in India and elsewhere have long placed vetiver root among their clothes to keep insects away. There seems to be validity in this. In experiments, vetiver root has protected clothes from moths, heads from lice, and bedding from bedbugs. The oil repels flies and cockroaches as well and may make a useful ingredient in insect repellents.
The oil is extremely complex, containing more than 60 compounds. In the main, these are bicyclic and tricyclic sesquiterpenes-hydrocarbons, alcohols, and carboxylic acids. Those that repel insects are minor constituents, including &-vetivone, B-vetivone, khusimone, and khusitone (see illustration, previous page).
As noted previously, the plant's environmental limits are unknown. They are, however, surprisingly broad.
As far as moisture is concerned, an established vetiver plant can grow in sites where annual rainfall is perhaps as little as 200 mm. At the other extreme, it also shows tremendous growth where annual rainfall is 3,000 mm. And in Sri Lanka it grows where rainfall is as much as 5,000 mm.
As far as temperature is concerned, this tropical species can take any amount of heat but cannot be counted on to survive subfreezing conditions. For example, plants in Georgia (USA) survived when soil temperatures reached -10°C without apparent damage but died when soil temperatures reached -15°C.
Vetiver is remarkably free of disease. However, Fusarium (the most widespread cause of rotting in fruits and vegetables) reportedly attacks it, notably during rains.
Perhaps of greater import is the leaf blight caused by Curvularia trifolii. This disease of clover and other crops may attack vetiver also during the rainy season. Malaysian researchers recommend that growers top the plants (at a height of 20-30 cm) to remove any infected foliage. Copper-based fungicides such as Bordeaux mixture also control this blight.
In Malaysia, a detailed investigation of vetiver has located yet more fungal species . These had little effect on the plant itself, but they might eventually prove troublesome in crops grown near vetiver hedges. They include the following species:
· Curvularia lunata leaf spot in oil palm)
· C. maculans (causes leaf spot in oil palm)
· Helminthosporium halodes (causes leaf spot in oil palm)
· H. incurvatum (causes leaf spot in coconut)
· H. maydis (causes leaf blight in maize)
· H. rostratum (causes leaf disease in oil palm)
· H. sacchari (causes eye spot in sugarcane)
· H. stenospilum (causes brown stripe in sugarcane)
· H. turcicum (causes leaf blight in maize).
Termites sometimes attack vetiver, but seemingly only in arid regions. Except where the termite mound covers the whole plant, only dead stems in the center of stressed plants are affected. Normally no treatments are required.
In at least one location in India, grubs of a beetle (Phyllophaga serrata) have been found infesting vetiver roots.
Perhaps the most serious pest threat comes from stem borers (Chilo spp.). These were found in vetiver hedges in Jianxi Province, China, in 1989. In Asia and Africa, some of these moth larvae are severe cereal pests (for example, the rice borer of Southeast Asia and the sorghum borer of Africa).
Until this potential problem is better understood, vetiver plantings should be carefully monitored in areas where stem borers are a problem. This is both to protect the hedges and to prevent them from providing safe havens for these crop pests. A severe pruning seems to keep the larva from "overwintering" in the vetiver stems and a timely fire might also be beneficial.
Vetiver has outstanding resistance to root-knot nematodes. In trials in Brazil it proved "immune" to Meloidogyne incognita race 1 and Meloidogyne javanica.
Currently, vetiver is propagated mainly by root division or slips. These are usually ripped off the main clump and jabbed into the ground like seedlings. Although the growth may be tardy initially, the plants develop quickly once roots are established. Growth of 5 cm per day for more than 60 days has been measured in Malaysia. Even where such rapid growth is not possible, the plants often reach 2 m in height after just a few months.
It is easy to build up large numbers of vetiver slips. The plant responds to fertilizer and irrigation with massive tillering, and each tiller can be broken off and planted. It is important to put the nurseries on light soil so the plants can be pulled up easily.
Planting slips is not the only way to propagate vetiver. Other vegetative methods follow:
· Tissue culture. Micropropagation of vetiver began in the
· Ratooning. Like its relative sugarcane, the plant can be cut to the ground and left to resprout.
· Lateral budding. Researchers in South Africa are having success growing vetiver "eyes" (intercalary buds on surface of crown) in seedling dishes.
· Culms. As noted in chapter 2, young stems easily form new roots. This can be an effective means for propagating the plant. Laying the culms on moist sand and keeping them under mist results in the rapid formation of shoots at each node. This is an effective way to propagate new plants from hedge trimmings.
· Cuttings. One Chinese farmer has successfully grown vetiver from stem cuttings. The cuttings, each with two nodes, are planted at a 60° angle and then treated with a rooting hormone-in this case, IAA (indole acetic acid). He achieved 70 percent survival. An interesting point was that the original stems were cut in December, buried in the ground over the winter, and the cuttings were made in early spring and planted in April.
Normally, hedges are established by jabbing slips into holes or furrows. They can be planted with bullock, trowel, or dibbling stick. In principle, at least, the techniques and machines developed for planting tree or vegetable seedlings could also be employed.
To establish the hedge quickly, large clumps can be planted close together (10 cm). On the other hand, when planting material is scarce, slips can be spaced as far apart as 20 cm. In this case, the hedge will take longer to close.
Prolonged moisture is highly beneficial for the quick establishment of the hedge. For best results, fresh and well-rooted slips, preferably containing a young stem, should be planted early in the wet season (after the point when there is a good chance the rains will continue). In drier areas it is helpful to plant them in shallow ditches that collect runoff water. For the most rapid establishment of vetiver lines, weeding should be done regularly until the young plants take over. Clipping the young plants back stimulates early tillering and makes the hedge close up faster.
Usually, little management is needed once the hedge is established. However, cutting the tops of the plants produces more tillering and therefore a denser hedge.
Vetiver is a survivor. It is difficult to kill by fire, grazing, drought, or other natural force. However, if necessary, it can be eliminated by slicing off the crown. Because the crown is close to the surface, it can be cut off fairly easily with a shovel or tractor blade. Also, although the plant is resistant to most herbicides, it succumbs to those based on glyphosate.
In light of the massive environmental destruction now caused by erosion, any system that retards soil loss would seem to be a candidate for instant and widespread use. Indeed, if the power of the vetiver system is as great as now appears, in a few decades the world could see thousands of kilometers of vetiver hedges in a hundred different countries, in climates from lush to harsh, and in sites from verdant to sparse.
But the experiences so far are limited, and many uncertainties
remain. It is time, therefore, for a wide-ranging exploration of this new, and
seemingly revolutionary, technique.
In this chapter we identify some of the important, as well as some of the interesting and challenging, actions that could be taken to help vetiver progress in an orderly, responsible, and yet rapid manner.
CONTINUATION OF WORLD BANK EFFORTS
As discussed earlier, it has been World Bank agriculturists who have reintroduced the vetiver method of erosion control. Their enthusiasm and energy have stimulated people all over the world and it will be of inestimable value to the testing and adoption of vetiver if these activities continue.
The World Bank staff also created the Vetiver Network-a service that collects and disseminates vetiver information and maintains an address list of more than 2,000 vetiver specialists and aficionados. With interest in this grass rising rapidly, continued support for this activity is essential. Such a service prevents duplication of effort and ensures that interested people receive constant updates of information on experiences with vetiver in other parts of the world.
The fostering of a new technology like this is not, however, a normal World Bank operation, and it would be prudent for other organizations to initiate a complementary operation to take over should the abandonment of this project occur.
It is clear that vetiver could become a vital component of land use throughout the warmer parts of the world. It might be a low-cost way to protect billions of dollars of investment already made in agriculture and forestry, not to mention roads, dams, and other public works throughout Africa, Asia, and Latin America. It also could become a backstop built into future projects as a way to help protect the environment from many soil disturbances.
At present, however, that is all speculation. It is critical for countries to establish vetiver trials quickly, which would serve to show local decision makers what this grass has to offer their programs and projects.
To expedite, motivate, and assure success in such a massive number of trials, we suggest consideration of what could be called a "vetiver SWAT team." This might involve a small number of vetiver specialists, brought in on short-term assignment to show local authorities how and where to put in small vetiver demonstration trials.
These trials might be incorporated into specific projects dealing with topics such as those discussed below.
In farming areas, trials could be particularly effective. With vetiver hedges reducing rainfall runoff, farmers should encounter more moisture in their soils so that crops produce higher yields and tolerate drought better. Given a successful demonstration, the word is likely to spread rapidly from farmer to farmer. Thus, not only the environmental stability of an area but also its productivity may increase.
Foresters are likely to be impressed as well. By holding soil and moisture on site and by providing windbreaks, vetiver strips would be particularly valuable in the early stages of tree growth. At present, a huge proportion of tree-planting projects are failing because of dismal rates of establishment and survival. Vetiver might also act as a barrier against ground fires and creeping grasses, both of which often devastate young tree plantings.
At least initially, engineers are likely to be apathetic (if not apoplectic) toward the idea of using a grass for erosion control. The past 50 years or so have seen the rise in popularity of erosion controls based on bulldozers, land surveys, and engineered systems such as terraces, berms, bunds, and contour drains. By contrast, a strip of grass seems puny and insignificant.
However, demonstrations are likely to persuade everyone that vetiver hedges can protect and enhance the performance, as well as extend the useful lifetimes, of many structures made of steel, concrete, or asphalt. For instance, vetiver could help protect footpaths, railroads, and road cuts from washouts and slips. In addition, it has potential benefits for wastewater treatment and flood-control facilities. Further, because it can withstand lengthy submergence (more than 2 months has been reported), it can be planted along the edges of dikes, irrigation canals, bridges, and dams to prevent scouring.
Most observers have despaired of the possibility of radically reducing the vast amounts of silt washing every day into ditches, canals, reservoirs, rivers, harbors, estuaries, and other waterways worldwide. This would be a massive, perhaps impossible, task for any erosion-control technique. Vetiver, though, just might work. Rows of this grass across critical watersheds should reduce silt buildup downstream. Indeed, although huge plantings would be required, government authorities might find the expense and effort far outweighed by the financial benefits of extending the useful life of multimillion-dollar water projects, not to mention the protection of wetlands, coral reefs, and other vital economic environments.
The advantage of the vetiver system is the fact that it is applicable on a wide scale with little equipment, planning, or logistics. Further, it is likely to appeal to those actually occupying the land. This is vital: farmers and foresters may well protect their land with little or no urging-not for soil conservation per se, but for the increased yields fostered by the moisture held back by the vetiver hedges, not to mention the by-products of vetiver-fire control, forage, mulch, thatch, and so on.
Wherever in the tropics localized flash flooding is a problem, vetiver could be part of the solution-especially when the flooding is caused by denuded watersheds that can no longer soak up and hold back the rainfall and runoff.
Although rain falls infrequently in arid lands, it often adds up to considerable amounts. Moreover, desert rains are often intense deluges and the water rushes away uselessly down wadis and washes. Paradoxically, the water the desert needs so desperately is lost by flooding.
Vetiver barriers across those wadis and washes would likely capture the floodwater to recharge the thirsty aquifers beneath. Walls of vetiver would also hold back silt in which crops might grow vigorously.
In addition, vetiver hedges might prove excellent as windbreaks in decertifying areas. Already, palm fronds are used for wind protection in the Sahel, for example (see Appendix A). These palm-frond fences look somewhat like rows of dead vetiver, but it is likely that the living, growing, real thing would be far better-especially given vetiver's ability to withstand undermining and to "rise up" as sand or soil collects around it.
There is currently a great interest in keeping agriculture productive and self-sustaining. Although vetiver has seldom been considered in the many parleys, papers, projects, and predictions, keeping the soil on the site is the most fundamental part of the process. Vetiver, therefore, could be a key to success in many of the different sustainable agriculture systems under development for Third World conditions.
This and other vegetative systems of erosion control should provide long-term stability and, if combined with good crop-rotation practices, such as the use of green manures and organic mulches, could lead to stable sustainable farming that might even render slash-and-burn cultivation obsolete in many places.
Trials are urgently needed throughout the tropics.
Despite general opinion, vetiver hedges can provide a number of products that are especially useful to farmers in the tropics. These products can be harvested without sacrificing erosion control. They will provide farmers with extra income, and this should enhance everyone's interest in establishing vetiver hedges on their lands.
These products include:
· Mattress stuffing;
· Animal bedding; and
· Mats, baskets, and screens.
Setting up markets for local vetiver products may be one of the best incentives for inducing the mass planting of vetiver hedges throughout any neighborhood.
Although vetiver has been grown in scores of countries for decades or even centuries, not a lot is known about the plant itself. Studies should be undertaken of topics such as plant morphology, physiology, ecology, and cold tolerance.
Despite the general impression that vetiver is a single clone, it contains much variation. In one project in India, for example, six different botanical collections grown side by side were strikingly different in color, rigidity, flowering, and other features. Each type could easily be distinguished, for example, by the length and strength of the culms and by the barbs on the leaf margins .
Everyone interested in vetiver should now search through the germplasm for "super vetiver" cultivars for erosion control. Attributes to look for include the following:
· Method of forming clumps;
· Persistence of clump integrity;
· Structural strength;
· Root form; and
· Level of sterility.
Much valuable research could also be accomplished by studying details of the plant's physiology. Researchers experienced in the study of maize, sorghum, or sugarcane could provide useful insight here. More information is required on the following subjects:
· Seeding variability within and among genotypes.
· Flowering. Some cultivars have flowering heads; most have none.
· Structural unity. Why don't the stems rot and fall off?
· Nitrogen fixation. Does vetiver by any chance benefit from associated nitrogen-fixing bacteria as does Bahia grass and some other tropical grasses? Most C4 grasses have associated nitrogen fixation by Azospirillum that live in the rhizosphere.
· Allelopathy. Does vetiver adversely affect neighboring plants?
· Silica content of leaves. Is a high silica content what repels insects?
· Mycorrhizae. Are vetiver roots colonized by the beneficial fungi called "mycorrhizae"? Can mycorrhiza inoculations benefit the plant's growth?
· Water relations. What gives the plant its ability to withstand waterlogging and even submergence on the one hand and severe drought on the other?
· Mineral nutrition.
To understand more completely the potential for problems as this plant goes global, we need to understand its gynecology (the structure, development, and distribution of vetiver communities in relation to their environments). For example:
· What is the plant's best ecological niche?
· What other plants grow with it under normal conditions?
· Which animals, microorganisms, and insects associate with it?
· What are its soil interactions?
· What are its shade and water tolerances? Growth chamber studies could be useful here.
· Is the oil in vetiver roots fungicidal? Bactericidal?
Vetiver's gravest limitation is that it is currently restricted to the warmer parts of the world. Wherever cold occurs, even infrequently, the plant cannot be relied on to hold back soil down the years. Breaking through this cold barrier would open the possibilities of using vetiver with confidence in the frost-prone parts of the planet. This might best be done by an organized search for winter hardiness among the various genotypes.
In most cases vetiver can merely be planted and left alone. Nonetheless, a detailed knowledge of the conditions for its optimum performance would be extremely beneficial. Research on this might include subjects such as:
· The best spacing between the hedges down the
· The best spacing between the plants within the hedges;
· The nutrients that, at the time of planting, ensure optimal survival and growth; and
· Relations between pruning and regrowth.
Other features of hedge establishment and maintenance worthy of investigation include:
· Mass planting techniques. The machines used to plant
tobacco, beach grasses, trees, and vegetables should be tested.
· Herbicide sensitivity tests.
· Assessment of weediness.
· Potential as host for pests and diseases.
Effects on nearby crops also deserve detailed investigation. These include checking for the following:
· Nitrogen deficiency in the soil next to the
· Competition for other nutrients;
· Root interactions with neighboring plants; and
· Moisture deficiencies in the soil beside the hedges.
The integration of vetiver into various farming systems also deserves study. For example, how might vetiver hedges be fitted into alley cropping, slash-and-burn, terrace farming, horticulture, rice paddies, large-scale mechanized agriculture, and other types of farming?
RESTORING DEGRADED SITES
Degraded lands are so prevalent and so vast in the tropics and subtropics that to restore even a fraction of them may seem impossible. In this regard, vetiver unaided can do little, but it offers a starting point, or at least a ray of hope. To finally have a way to preserve whatever meager soil remains is a first step. From this, techniques for integrating various crops, trees, or wild plants that will help to rebuild the capacity of the land can then be envisaged.
Something of this sort has been pioneered in northern New Zealand where earlier this century huge barren coastal dunes were slowly rolling over valuable farmland. Nothing would grow in the sand- nothing, that is, until marram grass, Ammophila arenaria, was tried. This salt-tolerant European species put down deep roots, collected wind-borne sand, and stabilized the giant sandy juggernaut in just a few years. That was a feat, but the true payoff occurred after foresters planted a shrubby legume (Lupinus arboreus) amongst the grass. The sand then began to build up fertility (notably nitrogen) and organic matter. Within another year or two, the site was fertile enough for pine seedlings to thrive among the shrubs. The eventual result: the giant dunes were tamed; for decades the forest there has provided much of the timber used in Auckland, the country's largest city.
Marram grass is not like vetiver, but it acted as a rugged pioneer that enabled the restoration of this highly degraded site. Vetiver, with its even broader adaptability and greater potential, seems likely to do the same for many barren lands in the tropics and subtropics. This possibility should be evaluated.
An idea as revolutionary as this one opens several possibilities for innovations, a few of which are discussed below.
These days everybody thinks of farms in terms of hectares or acres. But John Greenfield suggests that in extremely arid or thin-soiled areas "a one-dimensional farm" might be run along the back of a vetiver hedge. It would be only one row wide, but might run for many kilometers. The crops would grow in the narrow band of soil trapped behind the hedge and would also be watered by the concentrated runoff. This is an unconventional notion, of course, but it just might be a way to get productive farming into areas so arid that people now consider the production of any food or tree crops impossible.
Warding Off Weeds
As mentioned earlier, vetiver is reputed to be a barrier to grassy stoloniferous weeds. This should be investigated. If it proves true, vetiver hedges would likely be planted in many places not to stop erosion but to stop the invasions of Bahia, St. Augustine, couch, kikuyu, or other pestilential grasses that constantly creep into farmers' crops on silent stolons.
Blocking Crabs and Rats
Creeping grasses are not the only pests that might be held at bay. Vetiver's dense network of oil-filled roots may block burrowing creatures of various kinds. Examples of such subterranean pests are the crabs that attack paddy bunds; and moles, mole rats, and other burrowing animals.
This, too, is an unorthodox idea, but not an idiotic one Trials at Kericho in Kenya have already shown that mole rats cannot abide a vetiver root in their burrows. They cast it out or tunnel around it and block it off, apparently to keep the smell from their living quarters (Information from C.O. Othieno).
As earlier noted, insects avoid vetiver oil and vetiver roots. This might have some modern utility. Would solid bands of vetiver block termites, fire ants, or other insidious underground insects? Might the oil or the smoke from burning roots be used against household pests and vectors of disease?
Vetiver burns in a lively fashion when the tops of the plant are dry. But in many places its roots, tapping into reserves of deep moisture, keep the plants lush and green long into the dry season. Bands of these succulent plants across hill slopes are said to make good firebreaks. This may not be a wholly reliable method of fire prevention, but many fires in rural Third World areas creep along the ground through the dry grasses. It seems possible, therefore, that stout, unbroken lines of vetiver might be a godsend to foresters and farmers who, only too often, see years of effort and millions of investment dollars go up in smoke in a single afternoon.
One small plant is a big constraint to cereal production in Africa and India. Usually called striga or witchweed, it is a parasite that spends its first few weeks of life living off the juices of other species. Its roots bore into neighboring roots and suck out the fluids. The vegetative victims are left dried out and drained of life.
Unfortunately, striga thrives in maize, sorghum, millet, cowpeas, and other valuable crops. Millions of hectares of farmland are constantly threatened; hundreds of thousands are infested each year. And today, nothing can be done. When striga breaks out, farmers abandon their land. Some of the most productive sites now lie idle-victims of this abominable sapsucker.
Vetiver is a member of the same subtribe of grasses as sorghum and maize, and it may prove to be a sacrificial barrier to the spread of striga. Alternately, the oils in its roots may suppress this powerful parasite that does its dirty work underground. Sucking in a dose of vetiver oil may be enough to do it in.
In Zimbabwe, wildlife researchers have found that blocks of napier grass, strategically placed, can attract nightly flocks of weaverbirds. These grain-devouring pests (usually called quelea) like to roost together in the tall grass after a day in the fields. The simple concept of providing a man-made haven for the night offers a means for capturing them in quantity. On moonless nights they can be approached and either caught for food or otherwise destroyed.
Despite the promise inherent in this approach to one of the world's worst pest problems, there are at present several operational difficulties. One may well be overcome using vetiver, which would likely be an ideal grass for creating the trap roosts. Compared with napier grass, vetiver would be permanent, nonspreading, and safe from wandering wildlife or loose livestock. Given further innovation, perhaps blocks of vetiver will eventually be used as "lenses" to focus flocks of pestiferous small birds wherever they are a farm problem (More information on the pioneering work in Zimbabwe can be found in the companion report on Africa's promising native cereals, Lost Crops of Africa Volume 1: Grains. For information on BOSTID publications, see page 162. Napier grass is mentioned in Appendix B).
Vetiver represents a whole new approach to erosion control. The hedge concept is a point of departure for future elaborations. We have included a section on the idea of searching for more species to use where (or if) vetiver fails. For details see Appendix B.