Vetiver Systems at work for Soil Conservation in the Fijian islands - A Review

Fourteen years ago Paul Truong and Colin Creighton visited Fiji on behalf of the Government of Queensland to review the impact of vetiver and to find out if it had any invasive features. Their report is an interesting and enlightening review and is well worth reading. The summary of the report is below. The full report can be found at: http://www.vetiver.org/Fiji%20Rep.pdf
Dick Grimshaw




REPORT ON THE POTENTIAL WEED PROBLEM OF VETIVER GRASS AND ITS EFFECTIVENESS IN SOIL EROSION CONTROL IN FIJI


by Paul Truong, Natural Resource Management, Indooroopilly and Colin Creighton Regional Manager, Land Use and Fisheries, Townsville


Report on a study tour of Fiji between 4 and 11 June 1994


SUMMARY


BACKGROUND


A study tour to Fiji was carried out by Mr Colin Creighton, Land Use and Fisheries Regional Manager (North) and Dr Paul Truong, Principal Soil Conservationist, between 4 and 11 June 1994. The aim was to look at the effectiveness of Vetiver grass as a soil erosion control measure and particularly its weed potential in the sugar industry where Vetiver grass has been used for over 40 years. Subsidiary activities were to gain information on Fiji's sugar industry, assess the appropriateness of catchment management and Landcare concepts to the management of Fiji's natural resources and evaluate progress with the ACIAR funded Underwater Visual Census Fish Stock Assessment project.


FINDINGS


1. Vetiver grass is not a weed. Following its introduction late in the 1800's and extensive planting for soil erosion control since 1950, Vetiver has not become a weed either in agricultural lands or other environments including wetland habitat.


People interviewed, including farmers, research and extension officers of the Fijian Sugar Corporation, agricultural advisers and executives of sugar mills were surprised when being asked whether Vetiver had become a weed in Fiji. They all emphasised that Vetiver remains where planted. Most sites visited are between 25 and 40 years old and Vetiver has only spread around its base through tillering. The seed situation is somewhat akin to sugar cane - while racemes form, no viable seed occurs and no seedlings become established. The only possibility where Vetiver could establish on sites where it was not intentionally planted, was when a living clump of Vetiver was dislodged from its original site accidentally, such as land slips and by road building machinery as observed in the field. On such occasions Vetiver clumps only moved a short distance down the slope and remained there. Clumps in locations such as creeks did not rapidly expand in size and would appear to be, as with Vetiver on dry land, very slow growing beyond the initial clump size. When it is not wanted, Vetiver can be eliminated by ploughing or repeated burning or applications of herbicide such as roundup.


2. Vetiver hedge system is a simple, practical and very effective soil erosion control method. When planted on contour lines Vetiver hedges are very effective in controlling soil erosion in sloping canelands by trapping eroded soil moving down slopes and ensuring water is slowed and dispersed across the contour. The hedges system is very simple and can be easily established by farmers. Numerous sites were observed where Vetiver had resulted in the retention of soil, forming a terrace effect on sloping lands. An example is a site with 12% slope with a terrace of at least 1.4m formed over a 25 year period. In a simple demonstration trial, the Vetiver hedge system improved yield by 55% (from 31 to 48 t/ha) on a steep slope near Rakiraki, through its retention of soil on this otherwise stony profile.




All people interviewed - farmers, research and extension officers from the Fiji Sugar Corporation and soil conservation officers from the Fijian Department of Primary Industries considered Vetiver hedges system a simple and effective method of soil conservation.


3. Other applications of Vetiver hedges. In addition to its main use in soil erosion control in canelands, Vetiver was also used widely to stabilise embankments, terraces, to delineate farm boundaries and recently for soil erosion control for cash crops on slashed and burnt plots on steep hill sides. Application within Queensland on disturbed lands such as quarries, road embankments and subdivisions are substantial and will enhance overall catchment management.


4. Proper maintenance is needed. Although farmers agree that the Vetiver hedge system is very effective in soil erosion control, they are reluctant to establish new hedges. The reasons given are the hedges take up too much land, they hinder farm machinery operation and sometimes harbour rats. However, extension staff pointed out that all these can be overcome by providing simple and regular maintenance to the hedge. Most farmers do not look after their hedges, so after 20-25 years a single 0.3m row has spread to between 2.5 to 3m wide row and terraces built up by trapped soil reached up to 2m high.


Fijian experience has found that if the hedges were trimmed every 3-4 years to keep them at approximately 0.5m wide, and trapped soil spread uphill, the hedge system did not take up too much land, farm machinery could be driven across and it did not harbour pests such as rats. In Australia, this maintenance could be achieved by deep ripping the upper edges of the Vetiver contour, with respreading of soils upslope as might be required from time to time.


CONCLUSION AND RECOMMENDATION


Mr V Seru, the Officer in Charge of Land Use and Soil Conservation of the Fijian Department of Primary Industries made the following summary:


"There is no doubt in my mind that Vetiver grass provides a very effective means of soil erosion control on steeplands. It is not a weed, it is very simple and practical for farmers to use, it does not compete with crops but it is a living barrier and it needs proper maintenance to provide the maximum benefit".




We are confident that the sterile Vetiver cultivar Monto, will very unlikely be a weed under all Queensland dryland and wetland conditions. Its effectiveness in soil conservation has been proven both in Queensland and overseas hence its release will only benefit Queensland primary industries and catchment management generally. It is recommended that:


* work on existing field trials in the Johnstone and Atherton Tablelands be intensified,


* further demonstration sites established in North Queensland's cropping lands; and


* activities to develop and promote a Vetiver management system appropriate to various Queensland industries and environments be enhanced.