Living Fences:
Agroforestry in Sub-Saharan Africa
Beginning fence.
Courtesy of http://ppathw3.cals.cornell.edu/mba_project/livefence.html
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Living fences have
a few major differences from hedges. They require less maintenance,
are planted further apart, and are usually combined with other
materials, such as barbed wire. Used all over the world, these
structures are greatly beneficial to the people who use them.
(Macklin)
Types:
Though there are two main types of
living fences, major distinctions between them will not be made
in this article. For reference, live fence posts are widely spaced
woody plants in single rows that are pruned regularly and used
instead of posts. Barrier hedges are spaced closer together, are
thicker, involve multiple species, and usually do not include
any other types of fencing material. (Cherry and Fernandes)
Typical Living Fence:
Usually surrounding
barbed wire, these trees and shrubs grew in their location from
seeds dropped by birds that had perched on the fence. Also common
are farmers deliberately planting seeds of species that easily
take root. Traditional living fences can be more durable than
wooden posts, as they are less susceptible to termites and fungus.
It is important that the species that make up the fence have the
ability to form a callus rapidly to cover the attachment site
of the wire; trees that produce sap should be avoided, as this
can be corrosive to metal. An alternative to barbed wire for those
who cannot afford it is to use several different species to create
a thorny hedge. (Cherry and Fernandes)
Purpose:
The original purpose of living fences
was to control basic movement of both people and animals. However,
as their benefits were realized, more and more farmers began using
them for a broader range of activities. (Cherry and Fernandes)
Advantages:
- fuelwood
- fodder
- sustenance for people (such as fruit)
- wind breaks
- fertilizer
- ownership boundaries
- mulch
- erosion control and a way to stabilize the land
- forage for small mammals
- increase in labor yield
- if leguminous trees are planted, can provide much needed nitrogen
into the system
- fibers for cloth
- shade
- construction materials
- medicines
(Cherry and Fernandes) (Martin 1991)
Disadvantages:
- Excessive growth can lead
to an increase in labor for pruning
- Competition of the fence with other crops for major resources
(Martin 1991)
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Short living fences surrounding a dwelling.
Photo by ICRAF, in Nairobi.
Courtesy http://www.winrock.org/forestry/factpub/Slidesho/Into.htm
Living fence lining a road.
Photo by Bill Macklin
Courtesy of http://www.winrock.org/forestry/factpub/Slidesho/Intro.htm
Photo by Janet Stewart.
Courtesy of http://www.winrock.org/forestry/factpub/Slidesho/Intro.htm
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Live-Wattle Fence Method:
- plant developed seedlings
at suitable distances apart
- weave branches from one tree into another
- tape the branches together where they meet
- Once the trees begin to increase in diameter the trees should
grow together firmly at the contact point.
- Depending on tree species, after 1 or 2 years you should no
longer be able to force the branches apart.
- The seedlings have developed into one low tree that has numerous
root systems. This makes it hard for an individual tree to die
off, due to the support of the roots. This should eliminate gaps
as well.
- Barbed wire can be placed at the top of the fence, if desire
- More
on live-wattle fences
(Herran 1955).
Small Farm:
- research trees in your area that
may already be used for living fences.
- If you do decide to select a new species, look for the following
characteristics:
o Cattle resistance
o Rapid growth from seed
o Other uses beside just a fence
o Long lifespan
- use posts with a barbed wire or a wire screen
- spread the plants so that they fill the spaces between the posts
rapidly
- fertilization is not necessary, but pruning should be done in
the dry season each year
(Martin 1991)
Species:
There are few widely used species,
though a few are mentioned here. It is important to remember that
using a non-native specie for your fence post may have more negative
effects than positive ones on your land and the ecosystem. When
possible, use native species that have already been tried and
tested as living fences.
Taken directly from Dr. Franklin W. Martin's article The
Living Fence: Its Role on the Small Farm. For more information
on each species, click its name.
Gliricidia
sepium, Mother-of-cacao (madre-de-cacao, madera negra,
mata raton). This small leguminous tree is so well known to farmers
in some countries and so useful that it has been given a medal
in Honduras. Common from low to medium elevations, the tree prefers
a medium rainfall, and is well adjusted to a periodic dry season.
The tree can be propagated from branches. An old living fence
post will tend to produce a large number of long, narrow branches,
perfect for planting. The branches root readily but the rate of
growth is moderate. Gliricidia can also be propagated from seed.
A narrow fence with broad crown is produced. Its lifetime is almost
indefinite. The wood of old trunks become black and very hard,
and so are useful for many small objects. Animals tend to feed
on the foliage, but in fences most is borne out of their reach.
The foliage is a useful feed in moderate amounts but there is
some question of its toxicity in large amounts. Flowers, buds,
and very young leaves are often cooked as a vegetable. The dry
seeds are poisonous and are ground and mixed with other grains
as a rat poison. Leaf fall occurs during the dry season and the
leaves make valuable mulch. The tree was used in the past as a
shade tree for cacao and coffee, but now has been replaced by
Inga species. On triennial pruning a good quantity of firewood
is produced. Pruning also results in root dieback and release
of nitrogen to the soil.
Erythrina
berteroana, Dwarf immortelle (bucar o bucare enano). This
leguminous tree is small to medium in size, and is commonly used
as a living fence post or a support tree for vine crops. Other
Erythrina species may be substituted it. The tree is covered with
dense foliage that is perennial. Because the leaves are not lost
during the dry season, this tree is best suited for regions with
somewhat more rainfall than is required by Gliricidia. Propagation
is from branches, big or little, usually planted where they will
be used. However, seeds can also be used. Growth is moderate to
rapid. The fence is narrow with a dense crown. The foliage is
attractive to animals and frequently used for feeding rabbits,
sometimes with ill effects.
The wood is soft and of limited use except for fuel. On pruning
the tree a large amount of useful mulch is produced. The seeds
are poisonous. This is a favorite shade tree for coffee in Central
America.
Yucca
elephantipes , Yucca azote. This is one of the most common
plants in living fences in Central America. Cuttings of branches
large and small are frequently planted close together, and as
they grow, make a practically impenetrable wall. The tree is easy
to propagate, slow to grow and has a long life. The flowers are
edible.
Bursera
simaruba, Gumbo limbo (indio desnudo, jinote). Gumbo limbo
is especially appropriate for dryer areas where madre-de-cacao
is not suited. Planted as large posts, it will root even under
fairly dry conditions. This tree has few other uses, for even
its wood is soft and short lived.
Moringa
oleifera, Horseradish tree. This "vegetable tree"
is one of the most successful plants in ECHO's seedbank. It handles
dry seasons well and grows especially quickly the first year.
The Asian Vegetable Research and Development Center in Taiwan
has developed a gardening plan which starts with palisade of moringa
grown from closely spaced seed. Trees are pruned at about head
height, and the leaves used as a nutritious cooked vegetable or
for animal feed.
see
more seed species
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There are many conservation
projects currently running in Africa. Most are based on the knowledge
that permanent soil is needed to sustain agriculture, especially
conservation agriculture. However, biomass availability is limited.
(Ashburner et al. 2002) Read
more about Conservation Agriculture in Africa.
Living fences are numerous in Africa, and highly diverse. A few
of the more well known are listed below.
Kenya:
In Embu, Kenya, it was found that,
when fed to cows, new foliage of Calliandra calothyrsus
raised the butterfat in milk by roughly 10%. In general, farmers
often use the living fence as a source of wood and animal feed.
In this particular region it was found that pruning between 2
to 3 months created a higher leafy yield than pruning every 4
to 8 months (higher woody yield). (Cherry and Fernandes)
West African Sahel
(subsistance farmers): In
this area, where free animal browsing threatens dry-season gardens,
non-living fences were constructed. Made of barbed wire, dead
woody material, and crop residues, these fences had to be rebuilt
every year. This practice negatively impacted both the soil, from
erosion, and living trees, which were harvested regularly to provide
the dead wood for these fences.
To help solve this problem, the Institut de Recherche en Biologie
et Ecologie Tropicale (IRBET)-ICRAF started a collaborative agroforestry
project. They state that the idea was to involve farmers in an
exploratory on-farm trial to see how well their technology worked
and to see whether live fences appealed to farmers. Their plan
had as the potential to raise farm income and productivity while
protecting the environment.
Live fences were originally introduced in Burkina Faso in the
early 1980s, and were made up of only one species: Acacia nilotica.
Sadly, researchers at this time did not work with the farmers,
which led to low adoption rates of this procedure. IRBETs new
goal in this project was to work with farmers; assessing what
they needed and developing a fence that would both protect the
farmer, protect the land, and provide by-products as well. (Author
unknown)
Read
Kabre's story
Jatropha Fences in Mali:
Farmers have been using
this plant to make hedges for generations. The physic nut (Jatropha
curcas) is a drought-resistant perennial that is not eaten
by animals and can grow on marginal soils for up to 50 years Among
its uses are the medicinal properties of its oil, a substitute
for the gazoil used in diesel engines of that region, and soap
making. Malis development is affected in several ways from this
plant:
- prevention of erosion
- elevation of women (through soap making)
- reduction of poverty through income generation
- source of renewable energy
- More about
Jatropha.
(Henning 2002)
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Ashburner, J., Friedrich, T., and Benites, J. (2002). Opportunities
and constraints for conservation agriculture in Africa. Leisa
Magazine: October. [On-line]. Available: http://www.ileia.org/2/18-3/13-14.PDF.
Author unknown. (date unknown). Burkina Faso: Living fences come
alive. ICRAF. [On-line]. Available: http://chemsrv0.pph.univie.ac.at/ska/zifence.htm.
Cherry, S. D., and Fernandes, E. C. M. (date unknown). Live fences.
Cornell University. [On-line]. Available: http://ppathw3.cals.cornell.edu/mba_project/livefence.html.
Henning, R. K. (2002). Using the indigenous knowledge of Jatropha.
IK Notes: World Bank. [On-line]. Available: http://www.worldbank.org/afr/ik/iknt47.pdf.
Herran, K. (1995). Living fences. Originally published in Permaculture
Journal (8). [On-line]. Available: http://www.rainforestinfo.org.au/good_wood/livng_fs.htm.
Macklin, Bill. (date unknown). Agroforestry practices. Slide show.
[On-line]. Available: http://www.winrock.org/forestry/factpub/Slidesho/Intro.htm.
Martin, F.W. (1991). The living fence: its role on the small farm.
[On-line]. Available: http://www.tropical-seeds.com/tech_forum/growingtech/living_fence.html.
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