DO MIRACLE PLANTS EXIST?
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CTA. 1988. DO MIRACLE PLANTS EXIST?. Spore 16. CTA, Wageningen, The Netherlands.
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One often hears about new plant varieties that are reputed to make deserts bloom and bank accounts blossom. But such dreams rarely come true in the real world. Such was the case with jojoba and guayule, exotic plants which did not fulfil the great...
One often hears about new plant varieties that are reputed to make deserts bloom and bank accounts blossom. But such dreams rarely come true in the real world. Such was the case with jojoba and guayule, exotic plants which did not fulfil the great expectations which were based on them. That is one reason why more attention is now at last being given to native trees that have already proved their worth. Only a few years ago, jojoba was being promoted by Third World activists and environmentalists as a miracle plant. Considered by some as a 'way to stop desertification' or as 'liquid gold', it was also supposed to save whales from extinction. Such a reputation naturally attracted media attention which made it front page news. Planting jojoba in the Sahel thus became good not only for the Sahel but for the world at large. Some groups or NGOs even went so far as to adopt it as their main goal. Such enthusiasm was not without foundation as Simmondsia chinensis or jojoba without dou bt has many advantages. This bushy species actually does grow well in very dry areas such as the deserts of Mexico or Arizona, its native region. An annual rainfall of 100 - 500 mm is all it needs to grow. It is resistant to both heat waves and temperatures approaching freezing and demands little in the way of soil fertility as long as it has good drainage. When it is about five years old and three metres high, this undemanding shrub begins to produce pods containing oily seeds. These can be used to produce an oil that is, above all, an excellent lubricant because it keeps its viscosity even at high temperatures. As with the whale oil that is normally used, it performs extremely well in gear boxes and transmissions. There are also other uses in the pharmaceutical, cosmetic and even food industries. Jojoba oil also has the advantage of keeping a long time without going rancid. On the basis of such promising information, many people believed that one only needed to plant jojoba to regenerate the Sahel and thereby increase the incomes of poor farmers and reducing the debts of their countries. Unfortunately, there is often a big difference between what is supposed to happen and what actually happens. To date, not a single jojoba bush has borne fruit in West Africa. It has now been realized that the climate in the Sahel is hardly appropriate for this plant. Trials that were done in Senegal, and repeated in Australia, confirmed that to blossom and produce fruit the jojoba needs winters that are both cool and humid! Furthermore, it responds better to alternating periods of short and long days, preferably with large temperature differences. In other words there are major problems with growing this plant in the Sahel. To add to these biological problems, there are also difficulties in getting farmers to plant jojoba, even along side their food crops. Even if it does grow, it must be protected for several years from livestock (who adore it) before one can hope to reap any benefits. But without fertilizers or irrigation, yields remain very low and quite insufficient to persuade farmers to grow it. After all, they can hardly be expected to include the whale conservation factor in their calculations! Launching grandiose development programs based on jojoba can thus be compared to building castles in the air... On the other hand, it would be unfortunate to abandon jojoba completely. But more detailed studies are needed to determine what can reasonably be expected from growing this crop in Africa. First of all, selection trials are necessary to find productive varieties best adapted to the climates of each region. Attention must also be given to cost-effective production systems that are easy for farmers to develop. For the moment, it is primarily the USA and Israel that are working with experimental plantations but they are limited by high labour costs, particularly of harvesting. Only Latin America currently seems to have all the conditions needed to make jojoba worth growing. Despite these difficulties, the jojoba fad continues to interest people and not a week goes by without a specialized documentation centre receiving a request for information on this plant. In France, a company has even started the in vitro reproduction of jojoba and some farmers in the Mediterranean region have started experimenting with it. Jojoba has thus become the perfect example of one of those plants that economic or political factors have pushed to the forefront as a 'miracle' species before any long-term tests have been done. It was the projected shortage of traditional petroleum-based lubricants that prompted the USA to do research on jojoba in the same way that it was the supply problems of rubber latex during World War II that resulted in research being done on another rubber olant. the auavule. Broken promises The bushy guayule plant, which is native to Latin America, contains latex in its cells rather than in lactiferous channels as is the case with rubber trees. The proportion of rubber compared to the dry weight of the plant ranges from 10% in wild plants to as high as 25-35% in cultivated plants. To extract it, the plant must be uprooted as it cannot be tapped. As with jojoba, guayule also grows in arid zones. It can survive with 250 mm of rain per year but it grows better with 450 mm. Could guayule be the rubber tree of the desert or the industrial plant that arid regions have yet to find? In northern Cameroon and in Senegal the hopes did not last long. The guayule shoots grew well during the first year or two but then died. They needed a cold winter which is difficult to reproduce in the southern Sahara. On the other hand, the Morrocan climate seems more promising and an experimental plantation of 40 hectares has been established. Generally speaking, these American species have not lived up to expectations in crossing the Atlantic. Adapting plants to new climates is no easy task and certainly cannot be done as rapidly as one often thinks. The American continent has already provided many useful species to Africa, such as maize and cacao, but many years were needed to ensure the adaptation and distribution of such crops. While the future potential of so-called miracle plants deserves attention, they should not be considered as overnight solutions to already pressing problems. Unfortunately, common African plants have attracted very little mei die attention. The disappointment caused by the failure of introduced species and a better evaluation of the conditions needed for development, however, have provoked new interest in the potential of trees that have been firmly rooted in African soil for centuries. Physic nut, Jatropha curcas L. which grows throughout the tropics has recently emerged from the shadows. This hardy tree stands up well to droughts and poor soils. It is traditionally grown in hedges (because animals avoid it), cut for fuel wood, or used for its many medicinal qualities well known to local people. Above all, physic nut produces oilrich seeds for about 50 years once it is established after four or five years of growth. Until the last World War, this oil was used to make laundry soap and candles. Studies also showed that it could be used to fuel diesel engines. But the development of the petroleum industry soon dissipated what limited interest had been shown in this little tree found in arid zones. The oil crisis, however, sparked new interest in this plant. Recent studies have confirmed old data: physic nut oil can, without any special treatment, replace diesel oil in small motors. The fuel consumption is somewhat higher but the power generated is about the same. This local energy source could be very useful in fuelling pumps, mills and small agricultural motors. It is easy to produce as the physic nut grows readily and its oil can be extracted without any major problems. Small processing units can even be established at the village level. This multipurpose tree has thus many advantages for farmers. Those in Cape Verde were among the first to recognize its value and to start growing it. On plots abandoned for growing annual crops, more than 100,000 physic nut seedlings are being planted. They act as wind breaks, help prevent soil erosion and increase the water retention capacity of the soil. Periodic trimming also generates a supply of fuel wood. But it is the projected production of soap and fuel that prompted people to invest in this crop. Part of the oil will eventually enable the production of 4.5 t of soap per year, enough to satisfy the demands of about 120 families. Another part will fuel the 22 kw motor powering the semi-industrial processing equipment. The rest will be used to fuel a generator capable of providing the basic electricity needs of an entire village. It could also be used in homes to reduce fuel wood consumption and to replace the lamp oil used for lighting. Such developments have already begun and the first results are encouraging. By exploiting it in this way, physic nut can become an inexpensive and easily integrated tool for local development, particularly for promoting small industry. To optimize its potential, research remains to be done on selecting more productive varieties, developing better cultivation techniques and experimenting with simple yet efficient processing systems. The gum tree The gum acacia, familiar to people in the Sahel, is also benefiting from a revived and long overdue attention. Growing throughout the Sudan-Saharan region, this multi-purpose tree joined the ranks of others that, weakened by droughts and overcutting, slowly disappeared from the landscape. About 4-6 m tall, this thorny tree is specially known for its golden pink excretions, the famous Arabic gum. But it is also a source of forage favoured by livestock and a hard wood which makes excellent charcoal. Finally, it helps to retain soil moisture thanks to its well developed root system and, as with all leguminous plants, it fixes atmospheric nitrogen and thereby increases soil fertility. The orchards of gum acacia in the Sudan now provide most of the world's gum, which is used primarily in the drug and confectionery industry. In Kordofan, the trees are harvested from seven to 12 years before being pruned. During the four or five years that it takes for them to return to production, food crops are interplanted between the trees. In West Africa, production has become very limited despite the high prices paid (1000 CFA per kg for the harvesters). In Mauritania, production plummeted from 6000-8000 t per year in 1972 to 150 t in 1986. And this despite the fact that demand greatly exceeds supply on the international market. To respond to this situation, numerous projects have recently been started. The regeneration of old gum plantations has already begun in Senegal, Mauritania, Mali and Niger. Experiments are also being conducted with village plantations using unproven varieties that are both more productive and more resistant to drought. These plantations, however, require careful maintenance, especially during the first few years. The young trees must be protected from animals by wire fences or thorn hedges and watered during a year or two to ensure their establishment. Finally work is needed on ways of improving the traditional tapping methods which often kill the tree by removing two or three metres of bark with one swipe of a machete. Training must, of course, be an integral part of such programmes. By returning the gum acacia to its former glory, one would also reduce the stress on the Sahelian ecosystem and favourize a cash crop that has little competition on the international market. Other plants that have long been part of the African landscape and its local economies can, if favourized play a significant role in the development of such areas. The often forgotten shea butter tree for example, is the third export crop of Senegal but it receives virtually no research attention. This despite the fact that its nuts have always been collected by women and transformed into butter. This is the same product that eventually reaches the cosmetic counters of European stores where it is bought by people with delicate skin! The list of these trees and other plants that are poorly known by researchers and development workers is very long: the neem tree with its insecticidal powers; Acacia albida which helps to regenerate soils; the kenaf which can be used for paper production and the many other trees that provide highly appreciated food products. The list of potential uses is also very long. From domestic facilities up to export products, the diverse potential of these numerous local plants merits much more attention. This opportunity is actually more valuable in the short term than the development of exotic species brought in from other countries, if not continents. While the latter may have some remarkable points in their favour, their ecological and social integration often poses many difficult problems that soon cause their miraculous reputations to be forgotten. REFERENCES Martin. G. and A. Mayeux, 1984. Reflexions sur les cultures oleagineuses energetiques. IN: Oleagineux, Vol. 39(5) CIRAD/IRHO. 1988. Une plante oleagineuse d'avenir,,le jojoba. Biblioaraphy. Naigeon, C., 1987. Pourghere. graine de relance. IN: Inter Tropiques, No. 22
SubjectsCROP PRODUCTION AND PROTECTION;
- CTA Spore (English)