Description
Vegetative lines involve the planting of lines of vetiver grass following the contour lines, along stream banks and roadsides, 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 setup improves water infiltration and helps to increase the ground moisture level. Their root systems also help stabilise the soil and prevent further soil erosion. Thus this provides increased stabilisation of embankments, gully erosion, roads and slopes. Furthermore, water runoff and soil runoff reductions are observed, at around 57% and 80% respectively.
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). Furthermore, vetiver grass is resistant to different types of climatic conditions: rainfall from 600mm to 6000 mm /year and extreme temperatures of -14°C to 55°C, and could survive several months submerged in water. Vetiver grass can support high levels of toxicity by manganese, aluminium and other metals and high levels of soil acidity, salinity, alkalinity, and acid sulphate conditions. All in all, they provide great solutions as they are non-invasive, fire resistant, and regrow quickly and be used as mulch, fuel (vetiver energy value is 55% the energy value of coal), and as fodder. Finally, vetiver grass is very efficient in stabilising Demi-lunes, Eyebrow terraces or Negarims.
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.
PRE-CONDITIONS FOR IMPLEMENTATION
- 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 metres of contour hedge
- Sensitivity to surroundings: One of the downsides of vetiver grass is that it does not tolerate shading well, especially during the establishment phase.
- Layout: In order to be effective, vetiver grass should be densely planted, without a gap in between the clumps of grass.
METHOD OF APPLICATION
Steps of implementation
- Preparation: Vetiver bunches are dug up. Bunches are separated into sprouts. Sprouts are cut to a length of 10 cm.
- Planting: Sprouts are replanted along contour lines. They are spaced 10-15 cm apart from each other. On slopes steeper than 10%, hedges are placed 5 m apart vertically. Planting begins from the top of the slope and continues downslope. A double line of vetiver grass is recommended for more efficient hedges.
- Maintenance phase: Vetiver stripes require regular maintenance and protection from grazing animals in the first two years (establishment phase).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 appetising, therefore the cut material is usually used for mulching.
Considerations for application
- Economic investment depends on the slope and number of lines needed.
- The availability of materials and labour also influences costs.
BENEFITS
This intervention contributes to:
COSTS
Estimation of costs and benefits of intervention:
| Establishment costs | 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 costs | 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). |
CASE STUDIES
Description
The commercial farm in Kwa-Zulu Natal, South Africa uses vetiver grass barriers, where sugarcane is grown on a large scale under a rainfall regime of around 1,000 mm per year. The purpose of these hedges is to protect the land from surface erosion by creating semi-permeable barriers, allowing excess runoff to filter through but holding back sediment. Maintenance is very important, as vetiver often requires ‘gapping-up’ to keep the barrier dense, and it needs also to be cut back before the dry season to prevent it from burning.
2. Vetiver grass used for soil erosion and sediment control in soil-contaminated areas, in Australia
Description
Australia's mining industry faces significant challenges in rehabilitating mine tailings, which often contain high acidity and heavy metal contamination. Vetiver grass has emerged as a promising solution for these issues. Through strategic planting at various mine tailings sites across Australia, vetiver grass has demonstrated remarkable adaptability and resilience. Its extensive root system effectively stabilises soil, reducing erosion and minimising contaminant dispersion. In addition to erosion control, vetiver grass plays a crucial role in absorbing and accumulating heavy metals from the soil, contributing to the remediation of contaminated sites. This process, known as phytoremediation, enhances soil structure, nutrient levels, and overall ecological resilience. As a result, vetiver grass creates conditions favourable for the establishment of diverse plant species, promoting ecosystem restoration and biodiversity. The successful application of vetiver grass underscores its potential as a sustainable rehabilitation tool for mine tailings in Australia. By harnessing the ecological functions of this resilient grass species, mining companies can achieve cost-effective and environmentally sound solutions to mine site remediation challenges. Integrating vetiver grass into rehabilitation strategies aligns with the broader goal of promoting long-term environmental sustainability and community well-being within the mining industry.
FIND OUT MORE
External Sources
- This article offers a list of possible uses of vetiver grass, such as medicinal and domestic uses.
- Here you can find more case studies from Asia, Africa and Latin America
- Click here for a good list of alternative suitable species, and their geographical adaptability, to use for the grass stripes.
Guides
- A useful and complete guide about vetiver grass can be found here.
