Vetiver Grass - A Hedge Against Erosion --- A General Description
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There are twelve known varieties of vetiver grass, the most important is Vetiveria zizanioides. For centuries the oil extract from the roots of V.zizanioides has been used in the perfume trade. Indigenous peoples have recognized vetiver for its medicinal uses, for thatching, mulch, and feed, and for soil and moisture conservation. In more modern times the sugar industry has used vetiver grass quite widely as contour conservation hedges and for the stabilization of road sides and embankments. Vetiver once thought to be confined to wetlands thrives over a range of ecological conditions. It grows both on highly acidic (< pH3) and alkaline soils (pH11). Its roots will grow to depths of 3 - 4 meters. It is not effected seriously by pests or diseases. Many cultivars are non flowering, these when combined with a non spreading root system prevents "escape". Each clump of vetiver is extremely dense, so dense that if con figured correctly will act as a near perfect filter. The grass is easy and cheap to establish, and needs minimum maintenance. The average root strength is estimated at 75 Mpa. Roots of vetiver will increase soil shear strenght by 35% at a depth of 0.6 meters

When planted as a contour hedge it acts as a continuous filtering system, that slows down rainfall runoff, reduces rilling and gullying, and collects soil sediments at the hedge face. Soil and nutrient loss is reduced, soil moisture and ground water improves significantly, and natural terraces and ground leveling develops behind the hedge. An important feature is that vetiver grass takes up minimal space and is virtually non competitive with adjacent crops. Apart for soil conservation uses vetiver is seen to be an important grass for the stabilization of road embankments, canals, bridge abutments, landslide prevention etc. In other words it is a biological alternative to structural reinforcing techniques.

In south India, near the city of Mysore farmers have grown vetiver for years as hedges to demarcate farm boundaries, just as farmers in Kano, Nigeria, have done so for centuries (V. nigratana). Since the mid 80's vetiver technology has been introduced to over 100 countries. Dissemination was achieved through videos, slides, newsletters, journal articles, and small books - all of value to end use users - farmers, extension workers and NGOs. Demand for information has accelerated as a result of the recent National Academy of Sciences (Washington DC) scientific review of vetiver under a committee chaired by Dr. Norman Borlaug. The published report "Vetiver Grass - The Thin Green Line Against Erosion" endorses all the work to date and calls for further efforts to introduce vetiver as a major technology for soil and moisture conservation in the tropics and sub tropics.

Research has been carried out by numerous agencies working in tropical areas. Research by CIAT in Colombia (1800 mm rainfall per annum) shows soil loss reductions from 143 tons (no protection) to 1.3 tons per hectare (protected by vetiver), no reduction in crop yields, and reduced water run off. At ICRISAT south India (650 mm per year) soil loss reduction is significant and the rate of runoff in these dry areas is greatly reduced, by as much as 60%. Yoon (Malaysia) and Materne (Louisiana) have undertaken some remarkable and practical demonstrations of its use, function, and management. In recent years work by Australian and Thai scientists point to the use of vetiver for the mitigation of environmental problems resulting from toxic minerals. At the same time feed back from growers including large South African sugar growers and small farmers in Ethiopia, India, China, Central America and the Philippines all confirm the tremendous potential of the grass and its use in soil and moisture conservation.