Erosion's Enemy

Vetiver grass is todayŐs best plant for preventing soil and moisture losses on rainfed arable lands. ItŐs cheap and proven effective under diverse field conditions. Low establishment costs and minimal maintenance make vetiver grass especially useful to subsistence farmers in developing countries. The vetiver technology for soil conservation has already been tested in many countries throughout the world from India to Fiji.

Unlike man-made structures that cost a lot to build, vetiver grass is a simple technology requiring no engineering experts. Planted as hedgerows, a barrier against erosion becomes effective in a few years, and the farmer can do it all himself with little or no help. And best of all, itŐs a natural solution that becomes a permanent part of the landscape.

Contour Hedges

When planted as a vegetative contour hedge, the densely tufted vetiver grass (Vetiveria zizanioides) blocks the erosive force of runoff. By slowing down runoff, the hedge can filter out silt that has already begun to settle. Silt then collects behind the vetiver hedges, and over the years it slowly builds into a natural terrace, anchored by dense spongy vetiver roots as long as 3 meters. In addition to saving soil, water is also held up by the hedge and has more time to seep into the ground, thus reducing runoff and increasing water retention. Water slowly passing through the hedge then spreads over a larger area and increases plant available moisture (Figure 1).

To be effective, vetiver hedges must be planted along the contour, or ŇaveragedÓ contour in rough terrain. Depending on growing conditions and spacing, a line of vetiver slips will take 1 to 4 years to close into a dense barrier. Slips should be planted at the beginning of the rainy season with a spacing of no more than 20cm. A vertical interval of 2 meters between hedges should be adequate. Although vetiver hedges require little maintenance once established, pruning will promote tillering and reduce time to hedge closure. Low pruning will eliminate any light competition between hedge and crop. Otherwise, vetiver hedgerows donŐt compete with crops and, when planted in only 50cm strips, take little land out of production.

Vetiver grass has many good traits:

  • wide temperature range (-9ˇC to 45ˇC)

  • pH tolerant (4.5 to 10.5)

  • low seed viability prevents spreading

  • fire resistant

  • unpalatable to livestock

  • not susceptible to diseases, insects, or rodents

  • vertical roots do not compete with crops

  • long-lived perennial plants up to 100 years

  • source of mulch and thatch
  • Some potential problem areas include saline, cold and drought tolerance, because their limits have not yet been established. This is not necessarily unfavorable, for example vetiver grass has been successful from 600 to 6000mm of rainfall and has survived dry seasons of 10 months. It has also been successful from sea level to 2600m above MSL. However, there are local markets for the aromatic oil distilled from vetiver roots, and this has led to the uprooting of plants in a few areas.

    Plant Material

    Vetiveria zizanioides has been found in over 70 countries worldwide. The best way to find plant material is to track it down in your own country. If vetiver doesnŐt grow in your area, look for an herbarium by contacting universities, agriculture departments, or botanical gardens. They should be able to tell you where to find vetiver if it has been reported in your country. If not, try the Vetiver Information Network at the World Bank in Washington, D.C., or the Royal Botanical Gardens, Kew Richmond, Surrey, TW9 3AB, England.

    After finding plant material, propagate vetiver grass by using root divisions or slips. Establishing a vetiver nursery or hedge from seed is too risky due to low seed viability and peculiar germination requirements.

    Low-Cost Alternative

    Vetiver contour hedges for soil conservation provide a cheap alternative to physical structures like bench terraces, embankments, and their waterways. They require no engineering technology or equipment, a lot less labor to establish, and wonŐt wash out in heavy rains. At 1/10 to 1/100 the cost, vetiver hedges take less land out of production to do the same job.

    Farmers with plant material can install their own vetiver hedges at no cost. After the hedge becomes permanent in a few years, thereŐs no maintenance. When combined with contour farming, the vetiver hedge increases moisture conservation, leading to yields more than 50% better than traditional cultivation.

    Smyle, J.W. and Magrath, W.B. (World Bank). (1990).. Vetiver grass - A hedge against erosion. Paper presented at the American Society of Agronomy annual meetings in San Antonio, Texas. Oct. 22, 1990.

    World Bank. (1990).. Vetiver grass (Vetiveria zizanioides): A method of vegetative soil and moisture conservation. Second edition. World Bank, Washington, D.C.

    World Bank. (1990).. Vetiver grass: The hedge against erosion. Third edition. World Bank, Washington, D.C.

    World Bank. (1990).. Vetiver Newsletter, March 1990, no. 3. World Bank, Asia Technical Dept., Agriculture Div., Washington, D.C.

    For plant material:

    A.G. Allison, Director
    Agricultural Services
    MASDAR, Ltd.
    141 Nine Mile Ride
    Finchampstead, Berks
    tel. (0) 734 730750
    fax (0) 734 730002