The widespread land degradation caused by inappropriate land management, unsustainable agricultural practices, overgrazing and deforestation resulting in clearing of vegetation cover and increased soil erosion is the most serious environmental concern in Eritrea. The annual rate of soil loss from cropland is estimated at 12-17 t ha−1 and crop yield is declining at the rate of 0.5 per cent per annum owing to soil erosion. The dependence on biomass (charcoal, firewood, agro-residues and cow dung) for domestic energy contributes significantly to forest and woodland clearance. A number of these unsustainable practices have resulted in a reduction in Eritrea’s terrestrial biodiversity, although it appears that coastal and marine biodiversity resources have remained relatively stable. |
The long history of sedentary rainfed agriculture has changed the land use/land cover systems and caused environmental degradation which has led to the degradation on forest ecosystems and loss of forest area, habitat fragmentation, soil degradation and biodiversity losses. There are various interventions carried out such as afforestation programs, area closures, soil and water conservation/water harvesting, agronomic practices and distribution of energy stoves to combat land degredation. However, agroforestry can be an important alternative system that has to be dealt widely through the integration of trees on farms that will result in ecologically, socially and economically sustainable farming system (Lundgreen, 1982). |
In Eritrea, a package known as the Minimum Integrated Household Agriculture is widely introduced at household level by the Ministry of Agriculture. This package enhances agroforestry practices at household level through the integration of crops, livestock and trees with multiple purposes. This is an indication that packages are implemented that could enhance agroforestry practices in combining trees, crops and livestock. Planting of more fodder trees would increase fodder availability, which would benefit both livestock and crop production. The above intervention ensures that woodlots are also established mainly for production of poles, and more fruit trees could improve nutrition (Ministry of Agriculure, 2007). |
The objective of this paper is to review and compile the indigenous agroforestry practices that has been practiced for centuries and are available in scattered documents so that adequate intervation can be made in the farming system. Besides, there were limited research programs carried out in Agroforestry in Eritrea which have not been published. This paper provides limited information on research efforts done and findings in order to enhance joint research cooperation with academic and research institutions in collaboration with regional and international institutions that are interested in agroforestry. It will also serve as a reference and source of information for extension workers, development agents and policy makers so that agroforestry could be given attention that it deserves for social, economic and environmental benefits. |
Concepts of agroforestry Agroforestry, social forestry, community forestry, village forestry and farm forestry are all terms used to describe tree growing that is undertaken outside forest areas. These terms are often used to describe very similar activities, but in theory they have slightly different meanings. The trees in an agroforestry system are not necessarily planted. Instead natural regeneration of trees may be protected, or mature trees may be deliberately left in the fields or pastures. Agroforestry systems often involve management of trees and shrubs and utilization of their products. The trees and shrubs will have an impact on the other components in the landuse system. Hence, agroforestry systems are normally characterized by ecological and economic interactions between woody perennials and crops or livestock (Tengnäs, 1994). Agroforestry definitions and concepts have their own limitations but agroforestry practices usually possess the following features (Amonum et al., 2009, Rocheleau et al., 1988 and Lundgreen, 1982). Agroforestry is a distinct multiple land use system which includes a combination of agricultural, forestry, horticultural and animal husbandry sub systems and practices. Agroforestry integrates trees with crops and or animals for reducing risk and increasing overall productivity. It is a risk aversion mechanism so that farmers could minimize the risk of crop failure by growing a variety of products on the same piece of land. Agroforestry practices have greater diversity compared to monoculture and production could be distributed over a longer period. It could also provide income that is more stable with increased cash flow. It provides benefit to farmers who may have difficulty storing or marketing farm produce. More efficient utilization of soil resources such as moisture, nutrients and sunlight is achieved in agroforestry to get multiple products which is not possible under monoculture.
There are three basic types of agroforestry systems based on their compositions namely agrisilviculture, which is a combination of crops and trees, silvopastoral, it is a combination of pasture and or animals and trees and agrosilvopastoral, it is a combination of crops, pasture and trees. Other specified agroforestry systems practiced are apiculture, which is bees and trees, aquaculture fish with trees including shrubs and wood perennials as well as multipurpose wood lots (Rocheleau et al., 1988). The socio-economic and environment benefits of agroforestry systems can be summarized as follows (Baumer, 1990 and Lundgreen, 1982). Contribute to the supply of firewood better than monoculture. Woody perennials are less affected than herbaceous plants by temporary water deficits, hence, agroforestry with woody perennials could increase directly or indirectly the production of food both in quality and quantity. There is an increased stability of food supply due to the diversity of plants in the system. The system contributes to the sustainability of the environment in maintenance of soil fertility, reduce wind speed and create a favourable microclimate to improve the productivity of crops/livestock. Woody perennials are selected not only to give wood products but also provide tannins, flowers, medicines, dyes, etc. The farming systems contribute to the improvement of economic and social conditions in rural areas not only by increasing profitability, sustainability and food security including increasing the purchasing power.
Farmers have always grown trees on their land with the expectation that it will have beneficial effects for the soil and crop yields. This capacity of trees and other plants to restore soil fertility was observed in several farming systems. It is also proved that the topsoil in forests is usually rich in nutrients and has a good structure. It has been concluded that the cycles of carbon and other nutrients under natural vegetation are relatively closed with little leakage of carbon. However, much research work is needed to discover and verify the effect of trees on the properties of soil. The status of the soil is one of the most important factors that determine how a crop will perform in a certain site. The moisture content in the soil is another important factor, and trees growing with the crops will also have an impact on the moisture content of the soil (Rocheleau et al., 1988 and Tengnäs, 1994). Agroforestry practices Agroforestry has been practiced for many centuries in Eritrea. The indigenous practices have contributed to the reduction in environmental degradation for decades. It is better to build on the available indigenous knowledge of agroforestry which can be easily adopted by farmers rather than introducing a new one. In this section the most important existing indigenous agroforestry systems are described and the practices that should be used to improve the system are included so that some form of improvements could be introduced by farmers and extension agents. Multipurpose trees scattered on crop lands (Parkland) Spatial arrangement: In most farming areas there are scattered trees growing in the fields. Often such trees were left when the land was cleared for agriculture, or naturally dispersed seeds may have germinated and the seedlings been deliberately protected during farming operations. In such cases, the spatial arrangement is a random one. The benefits to be obtained from the trees, in terms of soil fertility and soil structure, are normally more clearly seen in areas where little or no inorganic fertilizer is used (Bein, 1997, Habte and Araya, 2004 and Tengnäs, 1994). Management: The system consists of 10-20 trees with a density estimated to be 40 to 60 trees per hectare; farmers normally pollard the branches of the trees to be used for fencing, fire wood and for construction. Tree-management practices will depend on the tree and crop species concerned and the need for tree products. With a light-demanding crop, pollarding or pruning is essential, but this does not apply to shade-tolerant crops or to trees that naturally only have light shade. An example of species that need and tolerate pollarding are Balanites aegyptiaca (Bein, 1997 and Tengnäs, 1994). Some birds build their nests on trees and feed on grain and have long been a problem for cultivation of certain crops such as sorghum. Traditionally, both children and adults would spend much time guarding crops, but at this time it is not possible to get labour for such activity. The most destructive bird species in this respect is the red-billed quelea, Queleaquelea, which may sometimes invade cultivated areas in very large numbers in sorghum producing regions of Eritrea. Hence, proper pollarding or management of trees would solve the problem of shading and damage of crops by birds (Negassi et al., 2002 and Tengnäs, 1994). Benefits: A variety of products can be harvested from the trees, and among service functions soil improvement, wind-speed reduction and improved microclimate are important. Too many trees can cause reduced yields due to shade, and trees may attract birds which may be a threat to crops. Competitive trees with shallow roots, such as eucalypts, pines and Acacia mearnsii should be avoided. Trees that cannot be pollarded and which grow to a considerable size producing dense shade should also be avoided, e.g., Acrocarpus fraxinifolius, Other trees to avoid are Croton megalocarpus, Cupressus lusitanica and Ficus benjamina, Nematode build-up has been reported under Sesbania sesban (Bein, 1997, Habte and Araya, 2004 and Tengnäs, 1994) Species: This is known as a parkland agroforestry in which widely spaced pollarded trees are grown in croplands of sorghum (Sorghum bicolor), millet (Pennisetum glaucum) and taff (Eragrostis tef). Livestock rearing is also a part of this farming system which is similar to that of the semi-arid Sahelian zone of West Africa such as Burkinafaso and Niger. In the parkland agroforestry system in Eritrea, Faidherbia albida, Balanites aegyptiaca and Acacia tortilis and Cordia africana and Olea africana are traditionally managed in both crops and pasture grasses growing beneath the trees for the provision of fuel, fodder, fruit, shade and shelter (Bein, 1997 and Negassi et al., 2002). Wind breaks and shelter belts Preliminary surveys have shown that windbreaks and shelterbelts are planted to protect irrigated farms and settlements areas from strong and dry winds. Temporary thorny branches are used for protection of individual tree seedlings especially if the windbreak is a single row. Strips trees/shrubs planted to protect fields, homes or other areas from wind and blowing soil. Shelter belts reduce wind speed preventing soil erosion with about 50 per cent reduction in loss of soil nutrients. A wind break can consist either of a single row of trees with a spacing of 1.5 to 2.0 m or if it is more than one row the spacing used is 4-5 m within the rows (Bein 1997 and Negassi et al., 2002). Trees normally used as a wind break in Eritrea are Azadirachta indica (neem) Senna siamea, Delonix regia, Prosopis chilensis, Conocarpus lancifolius, Schinus molle, Eucalyptus camaldulensis, Eucalyptus cladocalyx and Eucalyptus globulus (Bein 1997 and Habte and Araya 2004). Trees on soil conservation structures Spatial arrangement: Trees can be planted as biological soil-conservation measures (tree strips), either in combination with grasses or alone. Trees alone are effective enough only on gentle slopes (less than 8%). On steeper slopes combinations with grasses are desirable, trees can also be planted on terrace edges in order to stabilize the structure and make maximum use of the land. Trees planted on the edge of a terrace will not have ideal moisture conditions but are effective for stabilizing the soil. Fruit trees, which need the best moisture conditions, can be planted just below the edge of the terrace where they can benefit from run-off and more moisture generally (Tengnäs, 1994). Benefits: The products and services obtained from the trees will depend on the choice of species. The role of stabilizing structures and making the land productive is essential. If perennials are grown on bunds, for example, the structures will become more permanent. Trees planted in the conservation structures could also reduce soil erosion but the trees and shrubs should be trimmed to hedgerows and placed above and between trees as a trash line. Limited plantations have been done in specific areas of Debub Zone, Eritrea with Acacia polyacantha (Bein 1997 and Negassi et al., 2002). Establishment of trees: The spacing for trees and shrubs intended to stabilize terraces can be 1.5-3.0 m for trees and 0.3-0.5 m or wider for shrubs if the farmer so wishes (Tengnas, 1994). Initial establishment can always be more dense and thinning can be carried out later to obtain the final spacing. On steeper slopes an option is to grow trees on every second terrace to avoid having too great a density of trees. There is no quantitative data available to show the increase in crop yield and the degree of reducing soil erosion due to such practice. Live fences and hedges Spatial arrangement: Live fences may be established all around the farm, but it is most common to establish such a fence around the homestead. The live fences are also found around many schools, and church and mosque compounds (Habte and Araya, 2004, Lundgreen, 1982 and Negassi et al., 2002). A live fence controls the movement of domestic animals. Live fences are also used as ornamental planting, improvement of the micro climate, demarcation of land, soil and water conservation, provision of security or privacy and to prevent shelter to backyard poultry. Establishment and spacing: Very many individual shrubs are required to make a fence or a hedge. Thus, the propagation method must be simple and cheap. Direct seed sowing or use of cuttings (depending on species) is primarily recommended. It may be better to raise seedlings in an on-farm nursery since they have small seeds and are relatively slow starters (Tengnäs, 1994). It is best to plant seeds, seedlings or cuttings in two staggered rows so that an impenetrable fence or hedge is formed. The distance between the rows can be 15-30 cm with the same space within the rows. Directly sown fences must be well looked after and protected initially (Habte and Araya, 2004, Negassi et al., 2002 and Tengnas, 1994). Benefits: Fences and hedges are often multipurpose. Some of their uses are to provide shade and a windbreak for the compound, control movement of cattle, provide protection for chickens against birds of prey, provide privacy, production of mulch, fruit, bee forage or wood and help in soil conservation. There are few risks involved as live fences require labour for maintenance, and if they are not maintained they lose their intended function and begin to compete with crops. The latex of Euphorbia tirucalli is very poisonous and dangerous for the eyes. Fences and hedges may harbour snakes, and some shrub species may turn into weeds, e.g., Lantana camara. Anotherplant, Thevetia peruviana is also very poisonous (Tengnäs, 1994). Species: The trees that are mostly used as live fence in Eritrea are Euphorbia tirucalli, Opuntia ficus indica, Euphorbia abyssinica and Agave sisalana depending on the location. Other benefits include production of fuel wood, fruit, fodder and fiber (Bein, 1997 and Habte and Araya, 2004). Wood lots in villages and community The need for timber and poles for construction purposes is one of the most common reasons for people to plant and grow trees. Few indigenous tree species grow as straight as some of the exotics, hence, these exotic species are very popular for building materials. Eucalypts are commonly grown for poles since they are fast growing, straight, easily split and the wood is reasonably durable. Several farmers plant Eucalyptus cladocalyx, Eucalyptus globulus and Eucalyptus camaldulensis to make use of unused land and to contribute to wood supply. Eucalyptus has become a vital asset due to ease of establishment and production by coppicing, its wide range of uses and growth performance, which is preferable compared to other species (Bein, 1997 and Tengnäs, 1994). Wood lots are planted near the villages, on road sides and waste lands; it reduces the time needed for collecting fire wood leaving more time for the more productive activities such as soil cultivation, food preparation and cooking etc., the wood lot provides wood for fuel so that the dung and other organic matter used as fire wood will be applied in the crop fields to improve soil fertility (Bein, 1997). As far as resistance to decay and termite attack is concerned, the best species are the indigenous ones. Many indigenous trees produce wood that can last for many years without treatment with preservatives. Many exotic trees are also problematic in areas where termites are common. Seedlings of eucalyptus and Casuarina spp. are very susceptible to termite attack, and grevillea may also be attacked. In such areas it is still recommended to promote the use of indigenous trees for construction, but continuous efforts have to be made to ensure regeneration for a sustainable supply (Tengnäs, 1994). Trees along river banks and water ways Spatial arrangement: River banks are prone to erosion if they are not well covered with vegetation. Furthermore many important indigenous trees are riverine, i.e., they occur naturally only or mainly along water courses. Thus, vegetation along rivers is important both from an environmental point of view and for the production of special commodities, e.g., medicine or fruits. There is no particular spatial arrangement needed to be used for that purpose (Tengnäs, 1994). Benefits: It prevents erosion of stream banks which affects large areas of productive land every year, it decreases evapo-transpiration of water from the river; it provides shade, fodder for livestock, construction material, fiber, fruit and other products. Species: Tree planting along river banks in the western lowlands of Eritrea is a common practice among farmers engaged in horticultural crops, the indigenous trees available naturally or left purposely along the river banks are Acacia nilotica, Arundo donax, Prosopis species, Famarix species, Ziziphus spina christi, Hyphaene thebaica and Cactus are used to stabilize the soil (Bein, 1997, Habte and Araya, 2004 and Negassi et al., 2002). Trees on range lands Spatial arrangement: Scattered trees in rangeland are beneficial in many ways, e.g., providing shade for livestock and herdsmen, fodder and wood. Normally such trees are scattered at random and there is no need to be particular regarding any regular spatial arrangement. Establishment and spacing: Any propagation method may be applicable, but use of seedlings can be recommended since it is essential to minimize the period during which protection is needed. Natural regeneration should be considered before tree planting is recommended, but both the methods can be used at the same time. Protection of the existing vegetation is the first priority (Tengnäs, 1994). If there are already a few trees, protection of natural regeneration should be the second option to consider. If trees need to be actively planted or sown, priority should be given to indigenous trees since they are generally better conservers of water than exotics. Spacing will depend on species and purpose, but usually no large pieces of land should be put under trees. Hence, normally a few trees will be planted at selected places and a fixed spatial arrangement will not be relevant. Management aspects: As always, protection during regeneration is important with young trees. Other management steps will depend on the species and the purpose for which the trees are intended. Sites along rivers are often fertile and, therefore, are often used for growing vegetables. Pollarding and pruning can then be considered for minimizing shade (Negassi et al., 2002 and Tengnäs, 1994). Benefits: The most important benefits are improved supply of fodder and environmental benefits, e.g., shade. Certain species may suppress the growth of grass and such species should, of course, be avoided. In the central highlands, lowlands and western escarpment silvi-pasture is the dominant land use system, a tree protected for fodder also has other uses such as shade, firewood, gum and nectar for bees and protects the soil from erosion, the rangelands also provide food for humans during periods of famine due to moisture stress where the leaves are used as vegetables, e.g., Faidherbia albida (Bein 1997 and Habte and Araya, 2004). Species: The dominant species with high dry matter content and nutritive value (crude protein >20% of DM) have been identified as feed sources. These include Acacia tortilis, Acacia senegal, Acacia seyal and Acacia nilotica. Other non-leguminous species are Balanitesaegyptica, Ziziphus spina christi, Dodoneaviscosa, Hyphaenethebaica and Cadabafarinosa could be specified (Bein, 1997, Habte and Araya, 2004 and Negassi et al., 2002). Research on agroforestry in Eritrea This paper focuses on research in agroforestry conducted from 1999 to 2002 in some locations of Eritrea. The research efforts did not continue as expected after 2002 due to shortage of resources. Limited and most relevant research topics were selected, reviewed and included in this paper. These are on hedgerow intercropping on barley, short duration improved fallow on barley and the effect of increasing distance and direction of Faidherbiaalbida on taff (Eragrostisteff). Effect of hedgerow intercropping on barley Alley cropping is an agroforestry practice where crops are grown between lines of trees and/or shrubs that are managed and spaced at regular intervals in cropland. According to Tengnas (1994) this practice is labour intensive, relevant mainly in areas with small farms and a high population density or where labour is not a limiting factor. This practice has received much research attention and is regarded as having promise for solving problems of declining soil fertility in situations where farmers cannot afford to use inorganic fertilizers at the recommended rates. Research findings indicate that alley cropping is not feasible in areas where the average rainfall is less than 800 mm annually. In this study, three spacing of Leucaenaleucocephala at 4.5 m, 6 m and sole crop were tested at Halhale, Eritrea (1807 m altitude) to assess its effect on barley yield and biomass. The test was done as a Randomized Complete Block with four replications. The yield was very much affected by poor rainfall in some years. There were no statistical significance differences in biomass among different hedgerow intercropping. The results averaged for1999 to 2002 showed that 4.5 m alley gave the highest biomass of 1,578 kg ha−1, even though this was non-significant (Table 1). The main benefits in conducting the research of alley cropping is the potential for sustaining or improving soil fertility. Other important benefits can be fodder, small-size wood and improved microclimate. Labour has sometimes been regarded as a constraint since the management of hedgerows requires a lot of work. Competition for moisture has been recognized as an obstacle, which is much more severe in drier conditions. This practice is not recommended in places where the annual average rainfall is less than 800 mm unless irrigation facilliteis are available. Leucaena often turns into a weed in warm and moist areas if it is not properly managed so adequate management practices are required (Tengnäs, 1994). Effect of short duration improved fallow on barley When land is fallowed after certain period of cultivation in order to restore soil fertility, shrubs can be sown to speed up the process. These shrubs can fix nitrogen and add organic matter to the soil. The shrubs require little management once they are well established but protection from livestock is an absolute necessity. In situations when the shrubs are densely spaced thinning can be done for harvesting of staking materials and for firewood. When land is to be brought back under cultivation, some shrubs can be left to supply propagation materials for the next fallow period. The main benefits of improved fallow is quick restoration of soil fertility and wood production. The potential problems encountered are mainly damage of the vegetation by livestock and increased labour demand for the establishment as well asup rooting of shrubs (Tengnäs, 1994). A study on the effect of fallow on the grain yield and biomass of barley was conducted in the Eritrean highlands. The trees used for the one year fallow system were Sesbaniasesban, Crotalaria grahamiana, Cajanuscajan and Tephrosiavogelii. Additional treatments tested were continuous cereals and natural weed fallow. The test was conducted in a Randomized Complete Block Design with four replications in a plot of 81 m2. Trees were planted at a spacing of 1 x 1 m and the tree biomass was cut, chopped and incorporated in to the soil, which was cropped with barley. The results showed that there was significant differences with highest grain yield being obtained from the fallow land planted with Crotalaria grahamiana (1,165 kg ha- followed by Sesbaniasesban (1,152 kg ha−1) with 708 kg ha−1 increase when compared to continuous cropping and 383 kg ha−1 increase compared to natural weed fallow (Table 2). The grain yield (kg ha−1) was the lowest for barley planted after continuous cropping of cereals. This is an indication that fallow planted with leguminous trees might increase the yield due to high nitrogen fixation in the soil that contributed to the yield increase of barley. Effect of increasing distance and direction of Faidherbia albida on taff Five increasing distance of 1, 3.5, 6, 8.5 and 11 m as well as direction of the tree on north, south, east and west were tested for the grain yield and biomass of taff. The grain yield and biomass of taff was not significant at an increasing distance from the tree. However, the grain yield and biomass were significantly different when the direction of the tree was taken into account. In general, it can be concluded that trees introduced in the farm have a complex interaction but might increase the relative humidity and suppress soil evaporation by shading effect of the tree canopy. The grain yield was relatively the highest at increasing distance of the tree in 3.5 m with 1667 kg ha−1 followed by a distance of 8.5 m with a yield of 1603 kg ha−1 even though it was non-significant. The biomass was also highest at 3.5 m (4061 kg ha−1) increasing distance from the tree followed by 6m (3822 kg ha−1) which was consistent. The direction of the tree revealed that south direction from the tree gave the highest yield (1704 kg ha−1) and biomass (3964 kg ha−1). The lowest yield was obtained in the crop field located in the east direction of the tree (Table 3). Several microclimate factors such as relative humidity, temperature and sunlight favors crops grown under Faidherbia albida. Much is still unknown on the effect of the species hence further research is essential to understand its agroforestry potential. Faidherbia albida is found mostly along the river banks and in woodland areas in Eritrea. The tree produces more leaves during the dry season. Farmers have different views on beneficial effect of the tree on crop yield. There are several farmers who claim that it increases crop yields grown in its vicinity. Challenges in agroforestry system The most important obstacles in agroforestry are land /tree tenure, scarcity of water for seedling production and erratic rains during the planting season. Direct seeding can also be done but it carries the risk of failure in poor-rainfall years. Active planting or seeding of trees should normally focus on trees for fodder, shade or fruit. Farmers who deal with agroforestry are not given incentives in kind, which could be in the form of farm tools, seed, fertilizers, etc. However, model farmers who are planting trees in watershed areas are given incentives like bicycles, solar panel, farm tools, etc. It will encourage them to plant more trees in the afforestation program but the same could be done particularly for agroforestry. Lack of adequate awareness, training and demonstration to farmers, particularly in agroforestry so that various tree species might not be planted in the wrong environment partly because of lack of information on suitable alternatives. The research on agroforestry was carrie d out from 1998 to 2002 but it did not continue as expected due to shortage of resources and facilities. Hence, there is an urgent need to continue the work provided resources and facilities are guaranteed.
Recommendations Create community awareness on the benefits of agroforestry; train farmers on the types of branches that can be removed during pollarding without damaging or killing the tree and suitable protection and management of young trees. Creating awareness on the wise utilization of the woody species in the area which is crucial in order to prevent the loss of valuable tree species. The governmental and nongovernmental organizations should promote different agroforestry practices to conserve indigenous woody species. The need of indigenous practices of agroforestry should be realized because the techniques have been used for generations and have contributed to the environmental degradation. Thus, it is important to build on the available indigenous knowledge of agroforestry so that it can be easily adopted by farmers. The livestock breeds existing and the local landraces of crops have become adopted to the environment and are also accepted to the farming community. Proper care is required during tree planting such as wind break so that competition between trees and annual crops is minimized. Assessment and surveys to be done on the role of trees and shrubs in reducing soil erosion and improving crop productivity. Relevant combinations of trees and crops need to be identified and agreed with farmers. Some trees compete severely with crops and trees like eucalyptus should not be planted on soil conservation structures in crop lands. It is necessary to establish demonstration sites to show the benefit of agroforestry practices and be able to show some of the suitable tree and shrub species for agroforestry practices. Tree planting along the river banks need to be combined with windbreak establishment. It is very important to consider the indigenous species rather than exotic species along water ways so that the biodiversity of local species might not get depleted. Tree legumes are very important source of high protein rich forage for subsistence and commercial livestock production. The forage trees provide animal feed during the dry periods when herbaceous species are not available. Thus, it is necessary to introduce drought tolerant leguminous trees which improve the forage production in dry areas. Research work on agroforestry need to be revitalized through a joint project proposals with regional research and academic institutions with the participation of farmers.
Top Conclusion New trees are not planted in the parkland agroforestry and the trees available are naturally grown in the field, hence there could be a gradual decrease in the density of trees. In addition, assessment was not done on trees and shrubs planted on soil conservation structures in preventing the amount of soil loss and the extent on productivity of crops. The demonstration activities that were carried out were limited with regards to useful trees and shrubs that have agroforestry potential. Agroforestry is most used as an agricultural system for small scale farmers and is generally accepted for soil improvement and conservation. Agroforestry is recognized as a land use system which is capable of yielding both wood and food, while at the same time conserving and rehabilitating eco-system. |
Top Figures | Fig. 1.: Parkland agroforestry
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| | Fig. 2.: Agroforestry in soil and water conservation
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| | Fig. 3.: Range lands and protein banks
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Tables | Table 1.: Effect of hedgerow intercropping on barley (average of 1999 to 2002)
| | Treatment | Biomass (kg ha−1) | | 4.5 m alley | 1578 | | 6.0 m alley | 1372 | | Control | 1522 | | Mean | 1118 | | LSD 5% | NS |
| | | Table 2.: Effect of one year improved fallow on barley
| | Treatment | Grain yield (kg ha−1) | Biomass (kg ha−1) | | Crotalaria grahamiana | 1165 | 3165 | | Sesbaniasesban | 1152 | 3075 | | Cajanuscajan | 1140 | 3123 | | Tephorsia vogelii | 1041 | 2963 | | Continuous cropping cereals | 457 | 1514 | | Natural weed fallow | 782 | 2152 | | Mean | 956 | 2665 | | LSD 5% | 335 | 791 |
| | | Table 3.: Average yield of taff as influenced by the distance and direction from Faidherbia albida (1992-2002)
| | Treatment | Grain yield (kg ha−1) | Biomass (kg ha−1) | | Distance (m) | | 1.0 | 1389 | 3500 | | 3.5 | 1667 | 4061 | | 6.0 | 1567 | 3822 | | 8.5 | 1603 | 3494 | | 11.0 | 1472 | 3422 | | Mean | 1540 | 3660 | | LSD 5% | NS | 200 | | Direction | | North | 1609 | 3769 | | South | 1704 | 3964 | | East | 1409 | 3444 | | West | 1436 | 3462 | | Mean | 1540 | 3660 | | LSD 5% | 215 | 150 |
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