Vetiver grass—A thin green line against erosion

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opportunities for using cellular level selection or somaclonal variability, while rapid hybridisation can be achieved through anther culture. The final chapter in the book by G.A. Norton et al. examines the role for systems analysis in rice pest management. The authors argue that pest damage to the rice crop and the way that farmers view this, is a complex matter that involves technical, social and economic issues. Computer-based techniques can be used as research and management tools to assist in drawing together and analysing these different issues, and exploring management options. However, the authors also point out the crucial importance of first identifying and defining the bounds of the problems in the field, using what they term 'soft' analytical techniques. These involve, among other things, structured meetings where scientists, extension staff and other field agents, and, as appropriate, farmers, get together to clearly define the problem and the relevant issues that have to be addressed. There is little doubt that this approach has not often been adopted by researchers in the past, and much of the research-agenda has been scientistdriven. However, it is also true to say that one of the best examples of the integration of sound science with technology transfer is the FAO Integrated Pest Control Program in Rice in Asia. This project embodies some of the principles developed in this chapter, but is focused primarily on the major practical issues facing the farmer, in terms of monitoring pest and natural enemy numbers, and the need to avoid or reduce pesticide treatments. In exploring the scope for applying their 'soft' analytical approach to national rice pest problems, the authors use examples from Malaysia and China. The chapter also provides an account of how computer-based technologies can be used to draw together all information, including that derived from the 'soft' analytical procedures discussed earlier. The authors describe this as the 'hard' systems analysis approach, and they use the brown planthopper as their example in describing the techniques available. The systems that have been developed allow for better use of the existing data bases on the pest, but, of greater

significance, is their role in simulation modelling and expert systems. The authors demonstrate the tremendous scope for simulation models to reproduce problems and potential solutions, that could not be examined experimentally in the field without prodigious commitment of resources, that are simply not available these days. The management options developed through simulation can be tested and modified, or be totally recast, after these have been evaluated in the 'real world' of the rice farmer. The other area discussed in the chapter is expert systems, where the authors explain how computer technology can be used to reproduce the thought processes that farmers, extension agents and others use in arriving at management decisions. There are some very exciting developments in this field, which will prove valuable in many areas, not least training. In conclusion, this a most useful publication that contains a wealth of information for those involved in rice pest research. However, its value extends beyond rice, and those involved with pest management in other cropping systems will no doubt find many of the chapters most useful. G. ROTHSCHILD ACIAR GPO Box 1571 Canberra, A C T 2601 Australia SSD1 0 1 6 7 - 8 8 0 9 ( 9 3 ) 0 0 4 7 1 - C

Vetiver grass

Vetiver Grass--A Thin Green Line Against Erosion. National Academy Press, Washington, DC, 169 pp. 1993, ISBN 0-309-04269-0.

The National Research Council (USA) is a private, non-profit self-perpetuating society of distinguished scholars engaged in scientific and engineering research, dedicated to furthering science and technology and their use for the general welfare. The report reviewed here was prepared by an ad hoc advisory panel of the Board on Sci-

195 ence and Technology for International Development. Support for the Project was provided by the Division of Environment of the International Bank for Reconstruction and Development, the Soil Conservation Service of the USDA, and the Office of the Science Advisor of the Agency for International Development. The list of contributors to the study filled two and a half pages of one and two-line entries from countries in all continents of the world. Vetiver grass ( Vetiveria zizanioides) can be described as a technique for all kinds of erosion control, under almost all sorts of conditions in almost all soil types, in almost all climatic regions except those with freezing conditions for long periods each year. This study was undertaken in recognition of the significance of erosion in depleting productivity worldwide, and the role that vetiver grass has played, and could play, in providing a means ofcontroUing massive erosion in regions in which the rural populations were too poor a n d / o r too uneducated to invest in and understand the technological approaches to soil conservation which have evolved in developed countries. In many cases the land parcels are too small for earthmoving machinery to operate. The Foreword points out that "erosion is literally costing the earth", and getting worse, especially in areas in which swelling populations are placing increasingly greater pressures on a dwindling land resource. Two World Bank agriculturists had a vision that a little known tropical grass, known as khus-khus' in many local areas, could provide the answer to soil erosion in the world's warmer regions, where the combination of highly erodible soils, intensive rains, pressures on the land, and the inability to adopt high-tech approaches to soil conservation, are greatest. This book describes the findings of the NRC Panel whose task was to "assess the truth (on) vetiver and to project its promise into the future".

1. A simplified description of vetiver grass Vetiver is a tall (up to 2 m) grass with coarse stems and leaves (5-8 m m ) which develop into

a large tussock (30-50 cm or more in diameter). These are resistant to most herbicides, but not glyphosate. The dense mass of roots (up to 3 mm diameter), spreads downwards and outwards from the base of the plant, these produce an oil which is used as a source of scent, and also an insect repellent, in some countries. Cutting the tops of the plants causes dense tillering which thickens up the hedge. There are several species of Vetiveria, some of which produce viable seed. To avoid unintentional spread, plantings of Vetiveria zizanioides should be of the South India type, this being used safely in many tropical countries without fear of spread from seed. But there are many ways of propagating it vegetatively for planting.

2. How vetiver is used |n practice It has been used in some countries to mark out property boundaries or the boundaries of fields, its potential for controlling erosion, when planted on the contour often unrecognised. Its advantages as a boundary marker are that it does not spread, that it does not compete unduly with crop plants, but can prevent stoloniferous species such as couch grass from invading. In other cases, in areas where it had been introduced some 30 years previously for erosion control on steep tropical hillsides, it was so effective that the locals had forgotten why it had been introduced. The chapter entitled 'Worldwide experiences' provides a brief discussion on its use in some 40 countries. The chapter on 'Case studies' describes its use in bringing a wide range of seemingly impossible erosion situations under control, in places such as: ( 1 ) the U.S.A. (an army tank manoeuvre range in a fragile water catchment ); ( 2 ) St. Lucia (where, among other things, householders use it to prevent mud and water from invading their backyards); (3) India (for reclaiming and revegetating, to native species, a large saline area with a thick crust of alkaline (pH l 1, sodic clay); (4) Malaysia (where one plant split into 57 pieces, was increased to 16 000 plants in 7 months with 200 000 plants distributed by 18 months); (5) South Africa (where it has been established on pure sand on a steep

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roadside batter facing salt-laden winds above the sea-shore, and on a badly eroded site of pure kaolin, and a railway embankment rebuilt after a collapse under conventional treatment); (6) Madagascar (where it is used in the bottom of graded ditches to carry run-off slowly and safely from 45 ° slopes).

control on farming, grazing lands and public works. When agricultural and soil conservation authorities in various countries are able to prove to their satisfaction that it will not become a weed, by avoiding types with viable seed, vetiver grass will make many difficult soil conservation problems easy. R.W. CONDON 20 Quest Avenue Yowie Bay N.S. W. Australia

3. Some conclusions

There are few, if any, experiments on the use of vetiver which could provide statistical data to prove its effectiveness in erosion control. Where this has been attempted, the controls and other non-vetiver treatments have often been washed out and destroyed. There is enough in the case histories and applications of vetiver in a multitude of situations to show that vetiver works as a "practical and probably powerful solution to soil erosion for many locations throughout the warmer regions of the world". In many places it is used to allow natural processes to build terraces and to stabilise the 'risers' of terraces, or to reinforce earthen banks and bunds which might otherwise be often washed away in heavy downpours on steep 45 ° slopes. The line of dense vetiver stems, perhaps up to 1 m thick, allows water to seep through slowly, causing it to drop its silt load behind the barrier. The editors have indicated a wide range of situations in the Third World for which they suggest that vetiver could be the means of bringing a serious erosion problem under control, and for non-erosive situations in which it could be put to use, ( 1 ) for dune stabilisation to protect desert villages from being overwhelmed by sand, (2) as permeable water-spreaders to turn flash floods in desert wadis to provide deep-seated moisture for crops, as living gully checks, (3) for stabilising gully floors and walls, as artificial wetlands for sewage and other effluents, (4) for protecting river and dam banks and levees, the list is limited only by limits to the imagination. In the developed world, it can be used in much the same ways to substitute for expensive earth-works, in stabilizing engineering works, and in erosion

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Research with Farmers

Research with Farmers: Lessons From Ethiopia. S. Franzeland, H. van Houten (Editors), CAB International, Wallingford, UK, 1992, ISBN 0 85 1988148. Countries such as Ethiopia are critically dependent upon their agricultural sectors. Agricultural technology development is a key to the improvement of that sector and eventually the whole economy. Farming Systems Research (FSR) has been mooted as a means of assisting the development of adoptable technologies. It does this by bringing farmers and researchers into closer communication by various means. The original concepts of FSR (e.g. TAC, 1978 ) have been much debated and modified. While the early models may have been overly expensive (Menz, 1981 ), they were invaluable in setting a trend of enhanced communication and accountability for agricultural researchers. Research with Farmers represents one of the second generation of studies, explicitly recognising the limitations of the early stylistic FSR models, and attempting a more pragmatic and cost-effective mode of operation. Some genuine successes are documented, in terms of modifying emerging technologies through interaction between scientists, farmers and economists. The ability of FSR teams to define and prioritise re-