Introduction

soil erosion

       Farm land in the tropical zone are prone to the problem of soil infertility, for instance, soil deterioration due to high rate of erosion. The use of land without proper conservation measures which imposes a risk of loss of organic content in the soil results in a rapid decrease of soil productivity and agricultural products. This leads further to greater dependence on production factors which means higher production cost and thus causes the filling up of water souces. The systematic use of vetiver grass for various purposes provides a valuable and beneficial strategy for soil management and preservation of natural enrivonment, particularly with respect to maintenance of soil moisture and mitigation of soil erosion in steep slopy areas.

       Vetiver grass is a variety of grass that can be used for soil enrichment and at the same time, for environmental preservation. To grow vetiver grass, there should be some management techniques as well as tending and care for example replanting vetiver tillers to maintain continuous ground cover. Vetiver grass has numerous advantages for agriculture and besides, it does not create a problem by becoming a weed.

Utilization of Vetiver Grass on Farm Land

       The utilization of vetiver system can be classified according to the patterns of land use as follows:
       1. Paddy fields: Vetiver grass can be planted along the edges of the dikes surrounding the paddy fields to mark the boundary. In addition, vetiver leaves can be used as mulch for vegetables and field crops in the paddy fields after the harvesting season. This helps increase organic matters and maintain soil moisture for crops that are cultivated in the dry season, thus providing a method of saving water supply that would otherwise be used for growing a second rice crop and in this relation, encouraging efficient use of land.

       2. Plots of field crops: Vetiver grass should be grown in rows alternating with field crops in low-lying areas. The grass helps retain rainwater that seeps through a wall of its roots which penetrates down to the lower layers of soil. It also enhances the friability of the soil by making the soil loose and improving air ventilation. Moreover, vetiver leaves can be used as mulch between rows of field crops to maintain soil moisture. This represents another method to increase organic components in the soil and simultaneously, allow translocation of plant nutrients from the lower layers to the upper layers of the soil.
       3. Plots of vegetables, ornamental plants and floral plants: Vetiver grass can be used to grow along the raised beds or around the plots of vegetables, ornamental plants and floral plants. Its leaves can be cut off to use for covering soil surface in place of hay which was used in the traditional method and is currently difficult to find. This not only reduces the expenses in transporting hay from the paddy fields, but also prevents erosion of the raised beds. Vetiver grass has an advantage over hay in that it can be grown in the area and does not have to be transported from elsewhere.
       4. Plots of fruit, rubber and palm trees:
        4.1 Existing orchards: The land with existing orchards is considered a complete system which is already secure and sustainable. Therefore, similar to the fertile forests, cultivation of vetiver grass is neither necessary nor appropriate in such areas because the grass cannot grow as it normally does owing to weak exposure to sunlight. However, vetiver grass hedgerows can be established in the areas that face drought and erosion. If the perennial trees are not older than 3 years or are not close enough to one another, vetiver grass can be grown in rows parallel with the rows of fruit trees outside the shade, in a circle around the fruit trees at a radius of 1.5-2.0 m. on flat land, or in an inverted semi-circle on slopy land. This way, vetiver leaves can serve as mulch covering the tree bases to help maintain soil moisture and prevent soil erosion.

vetiver grass in a paddy field

vetiver grass grown in the plot of vegetables

vetiver grass grown along the sides of a new road in sandy soil with pebbles and rocks

       4.2 Newly-established orchards: In orchards where fruit and rubber trees are just planted, vetiver grass should be grown along the contours parallel with the rows of perennial and fruit trees. Otherwise, it can be planted in a full circle at a radius of 1.5-2.0 m. surrounding the trees on flat land or in an inverted semi-circle in slopy areas depending on the kind and size of the trees. The leaves should be trimmed off and used as ground cover to conserve soil moisture and maintain soil fertility, which would eventually help transform the deteriorated, dry and abandonned land into a fertile forest with edible products. To maximize productivity, a mixture of compost or manure with 15-15-15 chemical fertilizer should be applied to enrich the soil at a rate of 25 kilograms per rai (1 rai = 0.4 acres).
       The examples of vetiver application in all the four patterns of land use include cultivation of vetiver grass to demarcate the boundary of paddy fields in Pattalung Province; cultivation of vetiver grass together with fruit trees in areas with steep slopes in the Doi Tung Development Project, Mae Fah Luang District, Chiang Rai Province; as well as cultivation of vetiver grass in the plots of field crops under the sandy soil condition with pebbles and rocks which is prone to inundation in Kaengkrajan District of Phetchaburi Province. There, vetiver grass is grown alternating with rows of field crops and lemon trees to lessen the magnitude of floods. The water permeates slowly through the roots of the grass which penetrate into the condensed part of the lower layers of the soil between pebbles and rocks about 50-75 cm. deep below the surface. This constitutes a natural low-cost method to drain the flooded water. However, vetiver leaves should be cut off regularly at a height of 30 cm. First cutting should be done about 3 months after vetiver grass has been planted in order to accelerate tillering and next cuttings every 1-2 months. In areas with steep slopes, the leaves should be placed at the bottom of the clump uphill to trap silts and crop residues. The number of rows of vetiver grass to be established depends on the gradient of the slope, the number of water detention areas at each level of slopes as well as the appropriate horizontal (6-10 metres) and vertical (1.50 metres) spacing between fruit trees.

       5. Plots of integrated farming: There are many models for growing vetiver grass in the plots where integrated farming is being implemented. Since the integrated farming system is characterized by biodiversity which comprises single cropping and integrated cropping systems and differences in terms of topography, the uses of vetiver grass in each pattern of farming are accordingly different. In steep slopy areas, the benefits of vetiver grass are diverse ranging from covering the ground as mulch to preserve soil moisture, increasing organic content in the soil, enabling the translocation of plant nutrients from the lower layers to the upper layers of soil, to reducing the risk of erosion. On the other hand, on flat land with deteriorated soil, the advantage of vetiver grass is demonstrated emphasizingly with regards to nourishment or rehabilitation of soil and improvement of soil moisture.
       Here are the experiment results of using vetiver grass in the plots of integrated farming conducted by Soil Science Division, Department of Agriculture.

       5.1 Cultivation of vetiver grass in rows: With a spacing of 6.0 m., vetiver leaves can be trimmed off to use for mulching approximately 1.8-2.6 tons/rai/year which provides nutrients composed of nitrogen, potassium and phosphorus at about 17-44, 1-6 and 36-80 kilograms/rai/year respectively.
       5.2 Cultivation of vetiver grass in a circle on flat land (at a radius of 2.0 m.) or in areas with mild slopes but existing in different directions: Vetiver leaves can be trimmed off to use for mulching, approximately 50-70 kilograms/culm/year which increases soil moisture up to 35 percent.
       5.3 Cultivation of vetiver grass in various patterns of integrated farming with fruit crops as the dominating plant: Vetiver hedgerows can reduce the quantity of runoff and the intensity of soil erosion by 2-6 and 6-36 times respectively. It was found that the amount of runoff and the rate of soil erosion decreased to the minimum level in the plots with pineapple as the intercropping plant and contrastingly, remained at the maximum level in the plots with banana as the intercropping plant.

       The optimal benefit from growing vetiver grass in various integrated farming patterns is that the deteriorated land with unproductive soil and subject to drought has been developed and transformed into a fertile sustainable agricultural system, the products of which can feed our lives. Once the fruit trees become mature, give yields and cover the whole area like a forest, the role of vetiver grass will eventually disappear.

Tiller Preparation and Vetiver Cultivation on Farm Land

       Tillers that are used can come from government agencies who prepare them in plastic bags at the age of about 45 days, or from propagation plots and other natural habitats. A whole clump is dug from the ground and then the roots and culms are cut to 10-15 cm. and 20 cm., respectively. After that, the shoots are bound together and soaked in water for about 5-7 days. Once new roots have developed, they are ready for transplanting.

       1. Vetiver is  grown  along  contours across the slopes. The inter-row spacing is 1.5 m. vertically or 6-10 m. depending on the inter-plant spacing of fruit trees that is to be adjusted upwards or downwards in relation to the contour curves. After the contour lines have been determined, the ditches are then prepared to a depth of about 10-15 cm. for further transplanting. If the slopes are made up of poor quality or low fertility soil, then a mixture of 15-15-15 chemical fertilizer with compost or manure in a proportion of 25 kilograms per rai should be added to the soil before transplanting. This will enhance vetiver growth performance. When fruit trees are still young, other crops such as corns, soya beans, green beans and cabbages can be cultivated simultaneously. Vetiver leaves should be cut before they begin to flower and placed over the crops grown between the vetiver rows and/or around the bases of the fruit trees.

vetiver hedgerows along the contours of a slope

       2. A season that is most suitable for vetiver cultivation is the beginning of the rainy season in which the soil contains enough moisture. If cultivation is carried out in an irrigated area, then vetiver should be planted before the rainy season arrives to enable proper growth performance and ensure effective functioning. In general, it takes at least 3 months for vetiver to establish and grow new, thick clumps, depending on the fertility level of the soil.

Vetiver Cultivation for Conservation of Soil Moisture and on Fields of Fruit or Perennial Trees

       Generally, the land that has been set aside for field and fruit crops farming are found in areas which rely heavily on rainwater and face severe drought. Therefore, water supply is constantly insufficient for crop cultivation which brings damages to the crop production and national economy. Efforts to solve the problem of insufficient water supply for the rainfed farming areas have been to use available water supply efficiently and to conserve as much moisture from rain as possible in the soil. Compared to other methods, utilization of vetiver to conserve soil and water on farm areas is considered a simple and low cost technique which farmers can apply on their own and does not require too much care.
       To maintain quick and stable growth performance, vetiver should be looked after in the following ways. It is very important to replace dead tillers with new ones. Once the vetiver grows maturely, their leaves are to be cut to 30 cm. above the ground which helps vetiver to grow faster and in denser clumps. In addition, vetiver leaves that are cut should be used to cover the soil or as mulch to reduce water evaporation from soil surface. Moreover, regular cutting of the leaves also prevents vetiver from flowering and thus allows it to grow more tillers and form thicker, closely knitted clumps. This will serve as a strong wall capable of filtering silts and at the same time absorbing water in the soil, thus enhancing soil moisture and supporting crop cultivation. Finally, farmers need to choose the methods and forms of cultivation which are suitable to the characteristics of their land.

Patterns of Vetiver Cultivation According to Different Conditions

       1. On slopes - Areas which consist of steep slopes are found mostly in the northern and southern parts of Thailand in which farmers prefer to grow fruit and perennial trees along hillside ditches or on bench terraces. A major obstacle under these conditions is the erosion of embankment due to heavy rain, especially with the newly constructed ones. So a simple solution to this problem is to grow vetiver along hillside ditches or on the far side of the bench terraces to enhance the soil and water conservation and prevent soil erosion.
       For areas which contain slopes but with no constructed bench terraces or embankment, vetiver can be grown together with fruit or perennial trees along contours across the slopes. The inter-row spacing should be 1.5 m. vertically or 6-10 m. depending on the interval between the fruit trees. But for areas with very steep slopes, vetiver should be grown in a half-circle with a radius of 1.5-2.0 m. at the base of the trees facing uphill to increase the efficiency in preserving water and filtering silts.

densely grown vetiver hedgerows on a steep slopy area

       2. On flat land - Usually areas which are not slopy and flat will not face serious problems of eroded and loss of surface soil. But even on flat  land, heavy rainfall still poses some problems because water cannot be absorbed into the ground immediately. Therefore, vetiver cultivation is still necessary to maintain soil moisture and retain topsoil, especially for farming areas which are vulnerable to drought and thus rely heavily on rainfed. Under such conditions, vetiver can be grown in a single row around the area, in a line between the rows of fruit trees or field  crops,   and in a circle,  or a  half-circle  around  the  bases  of  fruit  trees  with  a  radius  of 1.5-2.0 m. Using vetiver to cover the soil not only increases moisture and organic content in the soil, but also facilitates the translocation of plant nutrients underground thus improving fertility of the soil.

rows of vetiver alternating with rows of fruit and field crops

a vetiver hedgerow to trap silts and dried leaves

Summary

       In conclusion, the purposes of vetiver cultivation on farm land are primarily to prevent or reduce surface soil erosion, to conserve soil moisture, to enhance organic content, to translocate plant nutrients underground by covering the soil with vetiver leaves, and to mark the boundaries of an area. Vetiver culms can be used to filter silts and allow only some portion of water to flow through. As for the roots, they will penetrate vertically into the soil and serve as a wall to let water seep down, loosen the soil, and enhance proper ventilation underground. The leaves that are used to cover the soil will increase organic content and preserve soil moisture. When the leaves have fully been decomposed, it will release nutrients valuable to vegetables, floral plants and ornamental plants. Vetiver is also grown on raised beds to prevent erosion of the edge while the leaves are used as soil cover in place of hay. If certain areas in which fruit or perennial trees are already planted and appear to sustainably remain fertile and abundant, then it is not necessary to grow vetiver. For areas in which fruit trees are grown but still have some spaces between them, vetiver can be grown in a long  line across the slope to preserve moisture and prevent soil erosion. Or otherwise, vetiver can be grown in a semi-circular pattern to receive waterflow and trap silts outside the shade area between the trees or at least 1.5-2.0 m. away from the bases of the trees.

Copyright © 1996 Chaipattana Network Webmaster. All right reserved.
Reproduction of the information contained in this web site without permission is prohibited.