Live fences can be divided into two basic categories; living fence posts and live barriers or hedges. Live fence-posts are widely spaced, single lines of woody plants that are regularly pollarded and used instead of metal or wooden posts for supporting barbed wire, bamboo or other materials. Hedges are thicker, more densely spaced fences that generally include a number of different species and usually do not support barbed wire (Budowski, 1987). The International Center for Research in Agroforestry (ICRAF) currently defines live fencing as, "a way of establishing a boundary by planting a line of trees and/or shrubs at relatively close spacing and by fixing wires to them." (Huxley, 1997).
Although farmers have probably been using live fences for centuries, much of the early literature contains only a few references to a few cases in Peru, Cuba, Nigeria, and Costa Rica. The published information is limited to an identification of the species involved and brief descriptions of their management. As a result of studies conducted in Costa Rica, Budowski identified over 90 species being used for live fences. The most common species in Costa Rica are Gliricidia sepium, Erythrina berteroana, E. costaricensis, Bursera simaruba, Spondias purpurea, Diphysa robinioides, Jatropha curcas, Yucca elephantipes and Croton glabellus (Budowski, 1987). Another study by Sauer in 1979 identified 57 species of trees used as fence posts.
The primary purpose of live fences is to control the movement of animals and people, however, they have proven to be extremely diverse, low risk systems that provide farmers with numerous benefits (Rocheleau et al., 1988). "Besides their main function...living fences may provide fuelwood, fodder and food, act as wind breaks or enrich the soil, depending on the species used." (Westley, 1990).
Live Fence Posts
Live fence posts are commonly found in conventional barbed wire fences. In many cases, the trees and shrubs that appear along fence lines, originate from seeds deposited by birds perching on dead fence posts and the fence wire. In other cases, farmers may deliberately plant stakes of easy to root species such as Gliricidia sepium, Erythrina spp., Spondias spp., and Bursera simarouba. The live fence posts are far more durable than traditional wooden posts as they are less prone to attack by termites and decay fungi.
When grazing or browsing animals are part of the farming system, the only way to establish live fence posts and eventually a living fence, is to start with a conventional wire fence supported by dead fence posts and to gradually establish live fence posts to substitute for the decaying posts.
Ideally, the species used for live fence posts must have the ability to rapidly form a callus and cover over the point of attachment of the wire to the post. The callus protects the wood from attack by decay fungi and wood-boring insects. Tree or shrub species that have a resin or sap that is corrosive to metal, should be avoided. Otherwise, the wire breaks a few months after being attached to the live fence post.
The example on the right shows a live fence post of Spondias mombin (hog plum, tapereba) in Honduras. Many Spondias species are used in the tropics for demarcating boundaries. An added benefit is that they also yield edible and nutritious fruit.
Gliricidia sepium is the most common live fence post species in Central America and in other tropical areas because of the ease with which large stem cuttings root and its multiple uses such as forage, green manure and its properties as a rat poison. Farmers commonly start the establishment of Gliricidia live fence posts by planting a few large (1.5-2.0 m) stakes in the existing conventional wire fence. These stakes normally take root within a month or so and farmers allow the shoots to grow for 6 to 10 months before cutting them back. After the first pruning, subsequent prunings can be carried out every 4 to 8 months. Shoot pruning at intervals of 6 to 8 months result in woody sprouts that are suitable for use as stakes. Farmers are thus able to multiply live stakes for their fence posts within a year or two after establishing the first live fence posts.
Most resource-poor food crop farmers do not have sufficient capital to purchase barbed wire. As an alternative, more and more farmers are using a number of different tree and shrub species to establish dense, often thorny, hedges to protect their crops. The image on the right shows a livestock enclosure formed by a living fence of a thorny and unpalatable Caesalpinia sp.
Another alternative often used by farmers is the combination of easy to establish live fence posts and poisonous or unpalatable species. The example on the left is from southwestern Ethiopia and illustrates the combination of Erythrina abyssinica with Euphorbia tirucalli. The latex of E. tirucalli is highly toxic and the plant is generally avoided by livestock.
If well established, these natural barriers can deter both animal and human trespassers from entering into the farm.
Many farmers also use live fences as a method of demarcating their farms (Fortmann, 1985). Although agroforestry may not be appropriate under certain land tenure circumstances, live fences can serve as one method of securing land ownership where the law permits.
The example on the right, shows the use of Dracena usambarensis to clearly demarcate boundary lines in the Chagga homegardens on Mt. Kilimanjaro, Tanzania. Farmers periodically harvest stakes of Dracena for sale as potted house plants (Fernandes et al, 1984)
Products and Services from Live Fences
The term "multi-purpose trees" is often used when referring to some of the more common agroforestry species like Leucaena, Calliandra, Gliricidia and others. "Tree legumes can provide fuelwood, nutrient-rich mulch, erosion control and land stabilization, as well as other products such as food and fencing materials...and a source of high quality forage for ruminants (Gutteridge, 1994).
Farmers can also collect seeds from these live fences that can serve as functional seed banks. For example, in Cameroon, where an increasing number of farmers are becoming interested in experimenting with agroforestry, non-governmental organizations are buying seeds of Calliandra calothyrsus from farmers at a cost of 4,000 CFA (US $8.00) per kilogram for distribution to other farmers. Seeds of Tephrosia vogelii, a bi-annual, leguminous shrub used for shorter-term live fences and improved fallows, can be bought in the market during most of the year within the region of the Kom ethnic group in the northwest province (Cherry, unpublished data).
Protection of Farmland
In the river valleys of eastern Sonora, Mexico, flood plain farming is dependent upon living fencerows. Propagated fencerows of willow and cottonwood maintain, extend and enhance flood plain fields. These ecological filters also protect fields from cattle, harbor agents of biological control of pests, and provide renewable supplies of wood (Nabhan, 1977). Farmers often allow live fences to grow tall and serve as wind breaks to protect cropland.
Fodder and Fuelwood
Leaves, branches and twigs pruned from livefences and live fence posts provide farmers with an on farm source of fodder and fuelwood. Pruning intervals of 2 to 3 months yield more leafy material than pruning intervals of 4 to 8 months which result in more woody material (Duguma et al., 1988). This allows farmers to choose which product is of higher priority during different times of the year and adjust their management techniques accordingly. A study in Embu, Kenya found that fresh foliage of Calliandra calothyrsus increased butterfat content of milk by about 10% when fed to lactating cows (Franzel et. al., 1996). Live fences around the perimeter of the farm can act as nutrient traps, preventing loss of nutrients that could normally be lost through leaching or surface runoff.
Fruits, Flowers and Medicinal Products
Farmers can also plant fruit trees to supplement their diet and provide the household with important micro-nutrients, often lacking in some diets. The fruit can also be sold in the market to contribute to household income. There are a number of tropical fruit trees that have been incorporated into live fencing systems in Cameroon either as fence posts or within live fence hedgerows including guava, citrus, Bush plum (Canarium sp.), Inga edulis, Spondias mombin, Moringa oleifera, and a variety of palm species. A variety of medicinal plants (Prunus africana, Columbrina spp., Comiphora spp., Azadirachta indica) are often grown in living fences. "Large flowers of itabo or izote, Yucca elephantipes, can be sold from $.50 to $1.00 each in local markets" (Budowski, 1987).
Live fencing is one form of agroforestry that can provide a range of products and services on farmlands. Although live fencing systems are very old and traditional, the extent of the many potential benefits and the number of different farmer-developed systems are currently not well understood or even well documented. We can learn a lot from farmers who have been using live fences in their various farming systems and assist in farmer-to-farmer transfer of these technologies.
Problems of competition with nearby crops and pasture grasses have been documented by Fernandes et al., (1993) and Ong et. al., (1996) and more information is required on the most appropriate species and management strategies to optimize the functions of live fences. The many land tenure laws in developing countries are as diverse and complex as the many farming systems. These laws need to be well understood before looking at how trees, live fences and agroforestry can be incorporated into local farming systems. The development of agroforestry, and live fences, must take account of existing patterns of land distribution and control (Vabi, 1994).
Budowski, G. 1987. Living Fences in Tropical America, a widespread agroforestry practice. In: H.L. Gholz, ed. Agroforestry: realities, possibilities and potentials. Dordrecht, The Netherlands: Martinus Nijhoff, 169-78 pp.
Duguma, B., B.T. Kang and D.U.U. Okali. (1988). Effect of pruning intensities of three woody leguminous species grown in alley cropping with maize and cowpea on an Alfisol. Agroforestry Systems, 6, 19-35.
Fernandes, E.C.M., O'Ktingati, A. and Maghembe, J. 1987. The Chagga homegardens: a multistoried agroforestry cropping system on Mt. Kilimanjaro (northern Tanzania). Agroforestry Systems. 2: 73-86.
Fernandes, E. C. M., C. B. Davey, and L. A. Nelson. 1993. Alley Cropping on an acid soil in the upper Amazon: Mulch, fertilizer and hedgerow root pruning effects. pp. 77-96. In: ASA Special Publication 56. Technologies for Sustainable Agriculture in the Tropics. Am. Soc. Agron., Madison, WI.
Fortmann, L. 1985. Trees and Tenure ICRAF, Kenya.
Franzel S., Arimi H, Karanja J. and Murithi F. 1996. Calliandra calothyrsus: boosting milk production and income for farm families in Embu. In: Proceedings of the First National Agroforestry Conference, Muguga, Kenya, March 1996.
Gutteridge, R.C. & Shelton, H.M., (1994) Forage Tree Legumes in Tropical Agriculture CAB International, Wallingford, UK 1-11
Huxley, P. 1997. Glossary for agroforestry. ICRAF, Kenya.
Nabhan, G. P. 1977. Living Fencerows of the Rio San Miguel, Sonora, Mexico: Traditional Technology for Floodplain Management. Human Ecology, 97-111 pp.
Ong, C. K. and P. Huxley 1996. Tree-Crop Interactions: a physiological approach. CAB International, Wallingford, 73-150 pp.
Sauer, J. D. (1979) "Living fencing in Costa Rican agriculture." Turrialba 29 (4): 255-261
Rocheleau, D., F. Weber, and A. Field-Juma 1988. Agroforestry in dryland Africa. Nairobi: ICRAF 18-19 pp.
Vabi, M. 1994. Land Tenure and Potentials for Agroforestry Development in the Northwest Province of Cameroon. pp. 27-36 in: USAID Proceeding of an Agroforestry Harmonization Workshop. Yaounde, Cameroon.
Westley, S.B. 1990. Living Fences. Agroforestry Today, Vol. 2, #1.
Financial support for the development of this web page was kindly provided by the Cornell Agroforestry Working Group (CAWG) of the Cornell International Institute for Food Agriculture and Development (CIIFAD).
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