How do I use The Vetiver System?

Sunday, November 2, 2008

When used in the role of soil conservation and slope stabilization, Vetiver provides a simple and economical method to bind the soil with a deep and massive finely-structured root system. Vetiver roots are, per unit area, stronger and deeper than tree roots.
A well planned conservation project must follow three fundamental rules for laying out the plants:

1. Plants must always be set in continuous hedges following surface contours. The hedge should provide an even barrier to the surface water flow, and create a filter that will retain the soil and allow the water to pass at a reduced speed. An improperly leveled hedge could direct the water flow to its lowest elevation, resulting in increased soil losses in that location.

2. New plants should be set at a separation of 4 to 6 inches (10 to 15 cm) within the hedge. The most effective way to start a new hedge is by using small, well-rooted plants that have been grown in a healthy, pest-free environment. A good root system in the new plant will ensure nearly 100% survivability and kick-start the project by 2 to 3 months.

Alternatively, a bundle of three tillers (growing root segments), called a slip, can be planted directly on the soil every 4 inches (10 cm). Bare-root slips have a very high mortality when planted in poor soils, and this method is only viable when a large supply of mature plants is available for division. Allow for an additional three months of project completion when using this method. Vetiver hedges are fully effective only when plants form closed hedgerows. Gaps within clumps must be quickly replanted with new or relocated plants.

3. Multiple hedges may be required to stabilize a slope. A single hedge at the top of the slope is usually not enough to stabilize a slope, and does nothing for surface soil erosion. Multiple rows are required, and the separation between them will depend on the slope angle, soil type, and the current erosion/stability conditions. There is no magic formula to determine the proper row separation in a new project. The Vetiver Systems Applications – Technical Reference Manual provides some guidelines in section 3.9:
  • a 30° slope requires six plants per square meter (i.e. 7-10 plants per linear meter) and a distance between rows of about 5.7 feet (1.7 meter).
  • a 45° slope requires 10 plants per square meter (i.e. 7-10 plants per linear meter) and a distance between rows of about 3 feet (1 meter).
Warning: The Vetiver System is a new technology. As a new technology, its principles must be studied and applied appropriately for best results. Failure to follow basic tenets will result in disappointment, or worse, adverse results. As a soil conservation technique and, more recently, a bioengineering tool, the effective application of the Vetiver System requires an understanding of biology, soil science, hydraulics, hydrology, and geotechnical principles. Therefore, for large-scale projects that involve significant engineering design and construction, the Vetiver System is best implemented by experienced specialists rather than by local people themselves. Get professional assistance when appropriate.

Note: Photos are from stabilization work done at the Blackberry Eco-lodge in India. Click here to see more on the great work they did.

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