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Maize Grown on
Trees
Farmers are introducing trees into their farms to
provide fertilizer, fruit, firewood and livestock fodder. Photo:
World Agroforestry Centre
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Green fertilizers gain ground in Malawi as affordable
and sustainable improvers of soil health, crop yields and food
security.
Most farmers in Malawi harvest 1 ton or less of maize per
hectare without any type of fertilizer. The country suffers acute
food shortages, and in rural areas this is a direct result of
declining soil fertility. Using mineral fertilizers alone is
unsustainable both economically, because few Malawians can afford
them, and environmentally, as their long-term use fails to improve
soil structure and texture.
For decades, scientists have evaluated various nitrogen-fixing
tree and shrub legumes such as sesbania, gliricidia and tephrosia,
which farmers can plant either in sequential fallow or intercropped
with maize to improve soil fertility. These plants draw nitrogen
from the air and transfer it to the soil through their roots and
leaf litter and when their pruned leaves and other biomass are
incorporated into the soil.
A 10-year experiment involving the continuous cultivation of
maize with gliricidia yielded more than 5 tons per hectare in good
years and averaged 3.7 tons per hectare without using any mineral
fertilizers.
"Farmers can double their yield of maize," explains
Festus Akinnifesi, the regional coordinator for Southern Africa of
the World Agroforestry Centre, "or even triple it if they use
a small quantity of mineral fertilizer."
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"In the past, we often went hungry," says Mary
Sabuloni, a widow and mother of eight. "I used to get about 10
bags of maize from my fields. Now I get at least 25 bags and I can
feed my family all year round."
Faidherbia albida is another fertilizer tree that has
captured the interest of scientists and farmers in Africa.
This species has reverse leaf phenology, which means it sheds its
nitrogen-rich leaves early in the rainy season and regrows them
when the dry season begins. This makes it highly compatible with
food crops because it does not compete with them for light during
the cropping season, when only bare branches spread overhead while
crops grow. Faidherbia is a natural component of farming systems in
many parts of Africa, from Senegal to Ethiopia.
In Malawi, maize yields increased by up to 280% when grown under
the canopy of faidherbia trees. In Zambia, unfertilized maize
yields in the vicinity of faidherbia trees averaged 4.1 tons per
hectare, more than three times the 1.3 tons harvested beyond the
tree canopy.
Women farmers in Malawi are benefiting from
fertilizer trees through increased crop yields. Photo: World
Agroforestry Centre.
In 2009, Akinnifesi and his colleagues conducted an Africa-wide
meta-analysis of green fertilizers. From 94 peer-reviewed studies
they found that green fertilizers can increase average maize yields
by up to 1.6 tons per hectare. Based on the average consumption of
1.5 kilograms per person per day, this equates to an additional 3
to 4 months' supply of maize for a family of six. Greater
increases were recorded on land with low-to-medium potential,
typical of the plots worked by poor farmers who cannot afford
mineral fertilizer.
A man surnamed Majoni in the village of Jiya in southern Malawi
used to get 30 to 40 bags of maize from his land when he could
afford mineral fertilizers. After the money ran out, he got just 6
to 9 bags. In 2006, after establishing and attending to fertilizer
trees, his land yielded 70 bags of maize.
"My soil is now very rich and much better at retaining
water," Majoni says, adding that he has enough maize for
himself and his family and plenty left over to sell. His neighbors,
who used to accuse him of witchcraft, are now adopting the same
agroforestry technologies.
Through the Irish Aid-funded Agroforestry Food Security
Programme in Malawi, farmers are encouraged to use technologies
developed by the World Agroforestry Centre and incorporate trees on
their farms to provide fertilizer, fruit, firewood and livestock
fodder. In the past 3 years, over 300,000 grafted materials and
seedlings raised in centralized and community nurseries became
available to farmers. The fruit varieties being supplied are those
that the World Agroforestry Centre has identified as maturing
early, growing large, and producing nutritious, tasty fruit.
To combat a shortage of fuelwood and building timber, farmers
establish woodlots around their fields using fast-growing trees.
This not only satisfies local needs but takes pressure off
Malawi's remaining woodlands.
Agroforestry technologies are disseminated across Malawi through
farmer groups, training, nurseries and demonstration plots.
Extending these lessons to other countries will require strong
partnerships with donors, national research and extension systems,
nongovernmental and community organizations, and the private
sector.
"We need to refine, adapt and extend the unique attributes
of these trees to the millions of other food crop farmers who
desperately need homegrown solutions to their food production
problems," says Dennis Garrity, director general of the World
Agroforestry Centre.
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