VETIVER GRASS SYSTEM
Vetiver (Chrysopogon zizanioides L) is a very unique tropical plant. The species is sterile, non invasive and has to be propagated by clump subdivision. The plant can be grown over a very wide range of climatic and soil conditions if planted correctly.
Its massive finely structured root system that can grow very fast. This deep root system makes Vetiver plant extremely drought tolerant and difficult to dislodge by a strong current. When Vetiver grass is grown in the form of a narrow self-sustaining hedgerow it exhibits special characteristics that are essential to many of the different applications that comprise the Vetiver System. A good hedge will reduce rainfall runoff by as much as 70% and sediment by as much as 90%. A hedgerow will stay where it is planted and the sediment that is spread out behind the hedgerow gradually accumulates to form a long-lasting terrace with Vetiver protection. It is a very low cost and labor-saving technology.
Vetiver grass can be used to protect river basins and watersheds against environmental damage, particularly point source environmental problems relating to: 1. sediment flows and 2. excess nutrients, heavy metals and pesticides in leachate from toxic sources.
Results of numerous trial and mass applications of Vetiver grass in the last 20 years in many countries also show that the grass is particularly effective in natural disaster reduction (flood, landslide, road batter failure, river bank, irrigation canal and coastal erosion, water retaining structure instability etc.), environmental protection (reduction of land and water contamination, treatment of solid and liquid waste, soil improvement etc.), and many other uses. Vetiver Systems can be used by most of the sectors involved in rural and community development.
Morphological characteristics of Vetiver Grass
Vetiver grass is solid, hard, and woody. The stem is upright, with an average height of 1.5-2 m. The leaves are narrow, along the edge of the leaves are sharp teeth. The cluster roots do not grow wide, but they are 3-4 m deep and 2.5 m wide after two years of planting. The roots of Vetiveria zizanioides contain the best quality of oil.
Vetiveria zizanioides is commonly used because of its non-granular character, mainly propagated by cloning methods so it can not grow as a weed (Hanping, 2000).
Vetiver needs a rainfall of about 300 mm, but over 700 mm is probably more suitable for grass to survive during droughts. Normally Vetiver requires at least three-month rainy season, ideally with monthly rains. As C4 plants, it is intolerant to shading. Shading will reduce its growth and in extreme cases, may even eliminate Vetiver in the long term.
There are 12 species known, but currently there are 3 species of Vetiver grown to keep the soil.
Vetiveria zizanioides L
There are two species of Vetiver originating in the Indian subcontinent:
This is from south India have been cultivated and have large and strong root systems. These accessions tend towards polyploidy and show high levels of sterility and are not considered invasive. It should also be noted that most of the research into different Vetiver applications and field experience have involved the south Indian cultivars that are closely related to Monto and Sunshine. DNA studies confirm that about 60% used for bio-engineering and phytoremediation in tropical and subtropical countries are of the Monto/Sunshine genotype.
This native Vetiver species are wide spread in the highlands of Thailand, Laos, and Vietnam and most likely in Cambodia and Myanmar as well. It is being widely used in Thailand for thatching purpose. This species is not sterile, the main differences between C. nemoralis and C. zizanioides, are that the latter is much taller and has thicker and stiff stems, C. zizanioides has a much thicker and deeper root system and its leaves are broader and has a light green area along the mid ribs.
Few existing plants have the unique attributes of multiple uses, environmentally friendly, effective and simple to use as Vetiver grass. Few existing plants that have been known and used quietly over centuries have suddenly been promoted and widely used worldwide in the last 20 years as has Vetiver grass. In Vietnam, Vetiver has been promoted in nearly 50 provinces. Strong evidence from scientific and practical studies further confirms that Vetiver is the right choice for environmental protection.