Description
Vegetative lines involve the planting of lines of vetiver grass following the contour lines, along stream banks and roadsides, in order to create a hedge. These hedges act like semi-permeable barriers, aimed to hinder surface erosion as they slow down run-off and retain sediments picked up by excess rainwater. This set-up improves water infiltration and helps to increase the ground moisture level. Their root systems also help stabilize the soil and prevent further soil erosion.
PRE-CONDITIONS FOR IMPLEMENTATION
- Maintenance: vetiver stripes require regular maintenance and protection from grazing animals in the first two years (establishment phase).
- Transportation: transporting vetiver grass from the nursery can be quite demanding if the planting location is far from the nursery, thus considering distance from nurseries should be part of the planning process.
- Surrounding species: A hectare of cropland usually requires about 250 linear meters of contour hedge.
- Sensitivity to surroundings: One of the downsides of vetiver grass is that is does not tolerate shading well, especially during the establishment phase.
- Layout: In order to be effective, vetiver grass should be densely planted, without gap in between the clumps of grass.
- Vegetation choice: Vetiver grass is a good choice for this intervention as it is resistant to different types of climatic conditions: rainfall from 600mm to 6000 mm /year and extreme temperatures of -14°C to 55°C. Vetiver grass can support high levels of toxicity by manganese, aluminum and other metals and high levels of soil acidity, salinity, alkalinity, and acid sulphate conditions. This species can survive several months submerged in water, is non-invasive, fire resistant, and regrows quickly. It can be used as mulch, fuel (vetiver energy value is 55% the energy value of coal), and as fodder. Vetiver grass can grow on slopes of > 50% and can be planted on a high variety of soils (red latosols, black cracking vertisols, roadside rubble, C-horizon gravels, laterites, sodic, and saline soils).
METHOD OF APPLICATION
In order to achieve vegetative lines, vetiver bunches are dug up and separated into sprouts, cut to a length of 10 cm and then replanted 10-15 cm apart from each other along the contour lines, right before the rainy season starts. On slopes steeper than 10%, the hedges are located 5 m apart from each other on vertical distance, forming lines about 200 m long. The work starts at the top of the slope and continues downslope. Usually, a double line of vetiver grass is recommended in order to create more efficient hedges.
OTHER
Very similar to the intervention described above is the so-called “Vegetative lines with cactus”. This intervention is based on the same principle as the Vegetative lines with vetiver grass, but it is suitable for drier environmental conditions (0 – 600mm). Like some other interventions, over time, this type of intervention can lead to the formation of terraces due to tillage and water erosion between the hedges.
Looking at the economic investment, the cost of the intervention is mostly influenced by the slope, and therefore the number of lines that need to be planted, availability of materials and labour. Nevertheless, maintenance plays a very important role in this type of intervention and its cost must be taken into account. It is often necessary to re-fill the gaps along the hedges to ensure their continued efficiency as barriers. Before the dry season, the height of vetiver grass bunches needs to be reduced and kept down to approximately 50 cm in order to prevent them from burning. It is also worth remembering that vetiver grass is not suitable for fodder because it is not appetizing, therefore the cut material is usually used for mulching.
This intervention is very efficient in stabilizing Demi-lunes, Eyebrow terraces or Negarims
BENEFITS
This intervention contributes to:
COSTS
Estimation of costs and benefits of intervention:
| Establishment cost | It depends on the slope but less than US $25/ha |
| Labor time | In India, a farmer can dig and plant 200m in a day, cost US $4 a day |
| Maintenance cost | It depends on the level of damage of vetiver grass and how many slips need to be substituted. |
| Benefits | Yield increases between 15% - 50% |
| Benefit of nursery | The farmer earns USD $2600/ha on the sale of quality vetiver strips.
A well-managed nursery can produce around 3 million of planting slips/ha/year (enough to plant 100km of hedge row). |
Source: case study based in India, 1998.
CASE STUDIES
South Africa:
An example of vetiver grass lines following the contour in a sugar cane cultivation can be found here, where this technique is used to stabilize the slope and prevent soil erosion.
Australia:
Here is an example of vetiver grass used for erosion and sediment control in a soil contaminated by heavy metals in a coal and gold mine area in Queensland, Australia.
Indonesia:
Vetiver grass strips can bring consistent benefits such as stabilization of soils where vegetables are grown, and contributing to increased soil fertility. A good example in Bali, Indonesia, can be found here.
FIND OUT MORE
- Click here for a good list of alternative suitable species, and their geographical adaptability, to use for the grass stripes.
- Here you can find more case studies from Asia, Africa and Latin America
- A useful and complete guide about vetiver grass can be found here.
- This article offers a list of possible uses of vetiver grass, such as medicinal and domestic uses.
