NOTES ON MAIN FINDINGS
Prepared by Norman Jones AGRAF and Christian Taupiac AFTES
World Bank, Washington DC
Prosopis sp. is known worldwide as a leguminous nitrogen fixing tree, able to adapt to arid conditions or salines soils. It provides fodder and fuelwood but also has a reputation as a weed and undesirable thorny tree in many circumstances. Extensive research has been carried out in its natural range (southern and northern America) also in counties where it is exotic (India, Mauritania, Sudan) resulting in better understanding of its potential.
(i) on the genetics : Although the Peruvian origin seems to be one of the best, it is proved that individual tree variation is critical, therefore clonal production from selected trees is recommended. Priority may be awarded to thornless trees and in situ grafting on wild rootstock may be a way to disseminate genetically improved prosopis.
(ii) on the uses : Prosopis is the only tree able to yield 2.5 tons of wood/ha/year where nothing else can grow. On salines soils in India this can rise to 12 tons. However, in better soil conditions other, less aggressive species would be recommended.
(iii) on the products : Prosopis timber has very good technological properties (low shrinkage, high resistance), these and its red brown color makes it attractive for high quality furniture and flooring. It can also be considered as a major component for food and fodder production from its fruits/pods.
(iv) on the commercial front: There are examples of private businesses based on prosopis wood products including furniture and flooring, fuelwood, barbeque wood chunks, charcoal and also food and fodder products are marketed in Brazil, Haiti and Peru.
(vi) on available information : the resource person for prosopis is Dr. Peter Felker, Texas A&M University, Campus Box 218, Kingsville TX 78363 (Tel. 512 595 3966).
Like any other multi-use tree, the sustainability of projects using prosopis as a development tool is directly related to the capacity of the local beneficiaries to integrate this tree into their agricultural system.
Prosopis is better known as mesquite but like many trees has various names in different countries. It is a legume and the genus is essentially American, extending from Texas through Mexico into South America as far as Chile, containing forty four species with only four indigenous to Africa and Asia. Many are aggressive pioneers and because of this the genus is considered a weed in many parts of its natural distribution and even in some countries where it is exotic. Prosopis is a nitrogen fixing tree and this, coupled with its pioneer habit has caused it to be introduced to many countries in Africa and Asia. It will grow in virtually any reasonably frost free conditions and its ability to adapt to arid conditions ensures its acceptance in many dry countries. The best known and most widely planted species is Prosopis juliflora, in India P. cineraria is indigenous and locally important and similarly P. africana in West Africa. The following notes show prosopis as a valuable "tool" of immense value to poor communities in dry areas and on problematic sites, but like all tools it is best used in skilled hands and for specific tasks.
The workshop was attended by representatives from its natural range (Texas, Mexico, Peru, Argentina) and where it has been introduced (Cape Verde, the Gulf States, Haiti, India, Mauritania, Niger, Senegal, Sudan). Delegates from international and national development and donor agencies attended together with representatives from a number of NGO's and industries working with prosopis. All delegates are pro-prosopis but there are also many around the world who consider the species a noxious weed. The following notes outline the versatility of the genus in general terms, details on its various characters can be obtained from the pool of specialists contacted through the workshop organizer Dr. Peter Felker, Texas A&M University, Campus Box 218, Kingsville TX 78363 (Tel. 512 595 3966; EM [email protected]).
The Prosopis Niche
Throughout its natural distribution prosopis has potential as a valuable timber for furniture and flooring, it is commonly used for carving both figures and bowls. The branch wood and off cuts are excellent fuel wood and can be converted into high grade charcoal. Prosopis plantations can yield 2.5 t/ha/an where little else will even grow and on saline soils in India has produced biomass of 12 t/ha/an. In recent years scientists in Peru have worked on the use of prosopis fruits (pods) as food and fodder. As an exotic it is most frequently planted on extremely problematic sites, exceptionally dry or in some cases saline. In Sudan and the Gulf States it is planted to stabilize moving sand, on parts of the Indian Gangetic plain to rehabilitate saline soils and in many countries - Haiti, Mali, Niger, Senegal, for fuel wood and fodder on hostile sites. Many prosopis are extremely thorny so it is planted as hedges to keep cattle either in or out.
The importance of a nitrogen fixing species with strongly pioneer characters must never be under estimated. There are many countries in the world with extensive areas of badly degraded lands caused by inappropriate agriculture and/or the climatic extremes of heat and dryness. The FAO delegate pointed out that 500 million people live in dry lands throughout the world and are amongst the poorest of all people. Many such sites are entirely barren and under these circumstances any plant growth is better than nothing - even if it gives only a little fuelwood, fodder or even shade. Some sites, like those shown during the papers from Sudan and the Gulf States, need stabilization to prevent moving sand destroying farmland or the remaining marginal sites. In Niger and Senegal prosopis is used for hedges and also woodlots for fuel. In these countries soil amelioration is being recognized as an additional benefit from prosopis planting. This should not be overlooked, especially in countries where the climatic conditions will support seasonal cropping, provided soil quality is improved.
The potential for food and fodder wherever prosopis will grow has been generally overlooked. Many villagers collect pods and feed them to their livestock but the Brazilian, Haitian and Peruvian delegates demonstrated there is much more value to these valuable pods once they have been processed. Delegates were supplied with cookies and bread made from prosopis fruits and it can be used to increase coffee volumes and even in ice cream. The Brazilian delegate is a rancher with a thriving business converting prosopis fruits into food and fodder products. A delegate from Haiti described the organization of his company collecting and processing fruits for fodder which is blended with corn, soya or cotton waste. At Piura University in Peru scientists are studying methods for industrializing prosopis pods and their results could prove extremely valuable for the poor, living on dry marginal lands around the world.
In Argentina and Texas prosopis timber is used for furniture making. It has an interesting color, brown or pink when freshly cut changing to dark reddish golden brown. The physical and mechanical properties are as good as or surpass many widely marketed hardwoods. It is stable and heavier than teak or walnut with exceptional surface hardness making it ideal for flooring. Since floors are usually laid using strips or small blocks even small diameter prosopis can be used for such products. Flooring and some beautiful colonial style furniture was displayed by the delegate representing a Texas manufacturer. Prosopis (mesquite) flavors are popular for barbecues in the States and a manufacturer from Texas described the manufacturing process for "mesquite cookin chunks" used to replace charcoal. Another delegate was an American businessman representing a firm importing prosopis charcoal from Mexico. The Haitian delegate also stressed the importance of prosopis for charcoal, 60% of people in Port-au-Prince rely on charcoal for cooking.
Experience with hardy often fast growing tree species which have been extensively planted as exotics has demonstrated that studies on the genetic variation are critical to continuing success. Species of prosopis have been transferred to many countries with neither knowledge nor records of the genetic base of the populations. During the workshop there was mention of similarities between the exotic populations in Mali, Senegal and Haiti and it was suggested that this may relate to the French influence in each of these countries in the past. Genetic studies are being carried out in a number of universities and institutes and the delegates from Santiago University, Argentina gave an excellent summary of their work. Prosopis species are essentially out-crossers which results in a high degree of between tree variability providing great potential for improving selected characters once they are genetically identified. Possibly one of the most important observations to date is the extensive within family variation suggesting that the critical unit for early improvement is the individual tree rather than family or provenance. Modern forest science has utilized mass clonal production following rejuvenation as a tool to maximize such benefits.
During the final session the panel appointed to review the proceedings made a number of observations. Many stressed the need for improving cooperation between scientists working with prosopis throughout the world and it is important that centers are identified as reference points for researchers and anyone using prosopis for any purpose. The potential social advantages of prosopis were highlighted as they link the basic needs of animal care with human requirements. It was recognized that a lot more work is needed on the genetics of the genus in order to obtain information concerning the biodiversity. One delegate emphasized the importance of extending the thornless population because of its obvious advantage to farm forestry. Also the novel idea of grafting improved material onto "wild" rootstock established by natural regeneration. An operation manual is needed written in a "how to do it" vein and in such a way as to be easily understood and translatable into different languages. Most panel members recognize that extension work is essential if arid countries throughout the world are to reap maximum benefit from this hardy, valuable tree. It is very important that prosopis is planted where it is most needed and not planted where other even more valuable species would give better returns. Delegates were urged to go home and organize local meetings to ensure NGO's understand the benefits possible from correctly handling prosopis.
Our Personal Views
The fascinating slides presented by the delegates were interspersed with pictures of poor nurseries and badly treated planting stock. Planters are fortunate that prosopis is such a hardy species. All nurseries seen had raised stock in poly-bags and presenters regularly referred to very long nursery periods. Modern nursery research has proved two important points, firstly, if plants are to be raised in containers some form of root training is needed and there are containers of many sizes and shapes on the market called rigi-pots, rootrainers, groove tubes, etc. which fulfil this need. These are placed on raised frames and ridges inside the cells ensure roots grow downwards, when they emerge through the aperture in the base of the container they are "air-pruned", developing growing points inside the pot ready for immediate growth after transplanting. Secondly, the potting substrate should be organic, however, most nurseries use whatever local soil is available sometimes mixed with a little animal manure. Research has shown that fibrous root systems develop best in organic mixtures so methods of composting any organic waste must be developed. If this is scarce nursery managers must grow plants for compost production. From the slides seen there is obviously great potential to quickly significantly improve tree survival and growth.
Current genetic research suggests selection and propagation of individuals will provide the best potential for improvement. Prosopis workers and planters should therefore learn from mistakes made by rubber planters - rubber is also a tree with multiple (latex and timber) end products. They concentrated breeding on latex, overlooking the potential of timber. Prosopis will need breeders looking for high fruit yields, wood biomass, timber and site adaptability. The sooner some outstanding phenotypes (trees of outstanding form) are selected and cloned the better. Where research into selection is advanced the best trees can be cloned and either rooted material or scions exported to countries where prosopis is needed. Scions or budwood should also be used for grafting rootstock already established in the field from natural regeneration to improve plant quality. In some countries farmers could plant 100 to 200 thornless trees per hectare for timber and interplant the rest of the area with grafted clones of heavy fruiting cultivars to provide income from food and fodder production.
The various species of prosopis are generally hardy and easy to handle in nurseries. Only the Indian species (cineraria) shows consistent problems related to its sensitivity to tap root damage - a problem which can be overcome with rigi-pots. The ease of establishment is sometimes misused resulting in prosopis being planted on sites which would be more productive under other forest species or for purposes other than tree planting. Through its aggressive colonization habit prosopis may spread onto valuable farm land. So care must be taken when planning a prosopis planting program. There are also cases where problematic sites have been planted and the resultant crop completely cleared for fuel or other purposes leaving the site to become barren once again. Planters must ensure good management practices are taught to villagers so that the benefits of the species are sustainable on these poor sites.
The wood of prosopis is a good fuel, can be converted into good charcoal and also the timber is used for many of the purposes high quality hardwoods are used. In the indigenous prosopis forests there is potential for expanding wood industries. If techniques to utilize small diameter woods and other methods of small wood utilization are developed a timber industry could develop serviced by trees from marginal dryland sites outside the natural range.
This was an important workshop and it is obvious that though prosopis may find its way onto the wrong sites due to its aggressive pioneering nature its benefits on difficult sites and in its natural habitat are many and must be harnessed. There is plenty of valuable technical information concerning site selection, preparation and choice of the best planting stock already available. More technical work is underway but it is important that what is known of the benefits of prosopis is put into practice on the vast areas of problematic sites around the world.