Led by the late Diti Hengchaovanich of Erocon Sdn Bhd, Kuala Lumpur and supported by Dr. P.K.Yoon (vetiver researcher and consultant – now 87 years old!), the 1990s vetiver trials on Malaysia’s East–West Highway were conducted along the Gerik–Jeli stretch, particularly near Banding Island and Lake Temenggor in the Titiwangsa Range. This region was selected for its steep terrain and erosion-prone slopes, making it ideal for testing vetiver’s slope stabilization capabilities. THESE TRIALS WERE THE FORERUNNERS OF PRESENT DAY VETIVER APPLICATIONS FOR INFRASTRUCTURE SLIOPE STABILIZATION. – MANY OF THE MANAGEMENT AND APPLICATION PROBLEMS FACED THEN REMAIN WITH US TODAY.
Key Locations of the Vetiver Trials
– Gerik–Jeli Highway (Federal Route 4): This is the primary segment of the East–West Highway where the trials took place. It spans from Gerik in Perak to Jeli in Kelantan. The main trial area locations were near Banding Island and Lake Temenggor, located roughly midway along the highway. The area features steep slopes and heavy rainfall, which posed serious erosion challenges. Vetiver was planted on highway embankments and cut slopes to test its effectiveness in stabilizing disturbed terrain. In total 30 linear km of vetiver hedge was planted. The exact locations appear not to be recorded but some were in the vicinity of a fill slope at: 5°32’40.94″N 101°19’39.57″E – see image
Purpose and Outcomes of the Trials
The trials aimed to assess vetiver’s engineering performance for slope stabilization and erosion control.
The downloadable consultancy report by Dr. P. K. Yoon focuses on the potential use of Vetiver Grass Hedgerows (VGHR) for engineering purposes, particularly in soil erosion control and slope stabilization along the East-West Highway in Malaysia. The study was initiated following the recognition of Dr. Yoon’s pioneering work in this area, which earned him several awards from the World Bank. The primary purpose of the research was to evaluate the effectiveness of VGHR in complementing engineering structures and to address the challenges faced in implementing this bioengineering solution. Key research questions included the characteristics of Vetiver grass that make it suitable for engineering applications and the practical challenges encountered during the project.
Research Methods
The research employed a practical trial approach, where VGHR was established along the East-West Highway. The methodology included the use of specially developed “foam plants” for planting, which were closely monitored throughout the process. Yoon supervised the production, transportation, and planting of the Vetiver grass to ensure adherence to quality specifications. Data collection involved assessing the establishment rate, growth vigor, and effectiveness of VGHR in preventing soil erosion and stabilizing slopes.
The study found that VGHR established rapidly, with significant root development observed within weeks of planting. The deep and extensive root systems of Vetiver grass effectively anchored the soil, preventing erosion even during heavy rainfall. The hedgerows demonstrated a remarkable ability to trap soil wash and stabilize slopes, with roots reaching depths of up to 3.6 meters. The project also highlighted the importance of quality planting materials and proper planting techniques in achieving successful outcomes.
The implementation of Vetiver Grass Hedgerows (VGHR) in the East-West Highway project faced several challenges, including:
- Timing Delays: The project was initially planned for completion in 3 months, but engineering works were delayed due to adverse weather, leading to overgrown and rejected foam plants.
- Poor Field Supervision: Lack of proper supervision resulted in shallow planting, no pre-soaking of plants, exposure to direct sun, and poor maintenance of site nurseries, causing poor establishment or total losses.
- Human Damage: Vandalism and willful pulling out of plants by workers from other sub-contractors damaged established hedgerows.
- Elephant Damage: Elephants trampled established VGHR, though the plants were expected to recover if promptly repositioned.
- Wash-Out: Heavy monsoon rains dislodged plants, necessitating replanting and support with bamboo stacks or sandbags.
- Weed Competition: Weeds like Mikania micrantha and creeping legumes shaded out VGHR, requiring herbicide application or hand-weeding.
These challenges were addressed through stringent specifications, close supervision, and adaptive measures to ensure successful VGHR establishment.
The quality of planting materials significantly impacts the success of Vetiver Grass Hedgerows (VGHR) in several ways:
- Vigorous Growth: High-quality planting materials, such as young tillers or culm-branches, ensure vigorous growth and rapid establishment of VGHR. Older or senescent materials are less effective.
- Root System: Container plants with active root masses (e.g., enmeshed in foam or soil) anchor firmly in the ground, preventing dislodgment by floods and enhancing drought resistance.
The following characteristics make Vetiver grass a sustainable and cost-effective solution for soil conservation and slope protection.
- Consistency: Using non-seeding, domesticated types of Vetiver zizanioides avoids the risk of invasive weed formation and ensures uniform performance.
- Transplanting Success: Properly conditioned plants in site nurseries, treated with anti-transpirants and foliar feeds, recover quickly from transplanting shocks, leading to higher survival rates.
- Long-Term Efficacy: Quality materials, combined with correct planting techniques, ensure the hedgerows remain functional and effective in soil erosion control for years.
- Poor-quality materials or improper practices can lead to failures, undermining the technology’s reputation.
The key benefits of using Vetiver grass in engineering projects include:
- Deep and Vigorous Root System: Vetiver grass develops deep roots (up to 3.6 meters), providing strong soil anchorage and preventing erosion.
- Effective Erosion Control: Its dense hedgerows trap soil wash and stones, reducing surface and sub-soil erosion.
- Self-Adjusting Growth: The hedgerows adapt to soil accumulation, growing taller to avoid burial and maintaining effectiveness.
- Drought Resistance: Deep roots access moisture, enabling survival during dry periods.
- Complement to Engineering Structures: It enhances slope stabilization and reduces maintenance costs for infrastructure like highways and culverts.
- Fast Establishment: High-quality planting materials ensure rapid growth, forming functional barriers within months.
Yoon concluded with respect to Malaysia:
(a) Use of Quality Planting Materials and Quality Planting Techniques: “ the success of Vetiver planting for engineering purposes is dependent on the quality planting material and the proper planting technique”. Unfortunately, far too many contractors have jumped on to the bandwagon. In their greed to maximise profits, they used poor quality materials and doubtful planting practices. These have resulted in failures that give an undeserved bad name to the Vetiver Hedgerow Technology.
- b) Import of Untested Planting Materials. Yoon’s pioneering work in Malaysia started all the current uses of VGHR for soil erosion control in Malaysia. He has no reservations with their adoption in the Agricultural Sector (Malaysia plantation industry) as the practitioners are disciplined and know the importance of using the proper tested cultivars. However, he was most concerned with users in the construction, infrastructure and engineering sector; they have no experience regarding the proper selection and use of correct cultivars and may not fully appreciate the long term consequence of a wrong choice. Vetiver grass occurs naturally in abundance in many neighbouring countries (Thailand). Unscrupulous contractors may resort to getting cheap but untested materials from suppliers in those countries. (Note… it is generally found that nursery propagated vetiver results in the best performing plants at the end application site).
(c). Untested planting materials may not perform well as unselected planting materials occurring in the wild are of poor vigor with poor rooting system. Of grave concern is the import of seed-bearing cultivars which could become a weed in Malaysia. Of even greater danger is the import of a cultivar which could be an alternative host for any pest and disease of economic importance to the major agriculture crops in Malaysia. The Consultant strongly urges that major users of VGHR to check the PROVENANCE of the Vetiver grass to be used. THIS IS THEIR RESPONSIBILITY.
Today, 2025, many of the issues and challenges reported by Yoon remain, and we continue to see unscrupulous contractors, poor designers, poor quality applications, and substandard vetiver plants. However, we also see many examples of excellent applications using quality vetiver applied according to correct design specification, especially where the client is well focused on a quality product, and where the supplier of plant material and site installer are experienced and disciplined.