Abstract:

Agroforestry ranks high among the significant initiatives in improving Sustainable
Land Management (SLM). Indigenous tree species for integration in agroforestry
systems stands a high chance of success because these species are already adapted
ecologically, and are socially accepted compared to foreign species. Therefore, the aim
of this study was to improve our understanding of how selected indigenous trees can
be managed to improve land productivity and income of small-holder farmers in
Uganda. The desired result is to increase the use of indigenous trees species for
increased productivity of cropping systems.
A household survey was conducted to assess the conservation and use values
indigenous tree species. Based on this study, four indigenous tree species were
selected for further investigation. The selected trees pecies include Makhamia lutea,
Albizia coriaria, Cordia africana and Faidherbia albida) were selected from three
agroecological zones (Humid eastern highlands in Mbale and Bududa, sub-humid
eastern plains of Tororo and Lira, and the semi-arid Karamoja.
Cordia africana was been investigated for its potential to provide shade in coffee
banana cropping systems with field studies conducted in Bududa and Mbale districts
in eastern Uganda. Generally, coffee productivity was better in terms of size,
succulence and quantity of the berries per bush; and overall bush vigour under C.
africana tree shade as compared to where there was no tree shading. Crown pruning
of C. africana shade trees was the most plausible management practice that farmers
were practicing on their farms.
Faidherbia albida is a species that has been widely reported to have important soil
fertility benefits. However, it has been reported to have a highly restricted distribution
with the niche being found only along banks of rivers and streams. The tree species is
thus being investigated for its distribution in the Karamoja region of Uganda and for
its potential to be included in future scaling-up to other dry lands areas in the country.
Using ecological information from literature, spatial interpolation techniques were
used to develop a map showing that 44% of Uganda is suitable for integrating F. albida
in agroforestry systems.
Makhamia lutea was investigated to determine the optimum distance between the tree
and the crops is not well-known. Fifteen paired plots with and without Makhamia
were planted with maize and the influence of the tree on maize yield was measured.
The yield of maize was not affected by Makhamia but the soil organic matter 15%
higher in Makhamia compared to non-Makhamia plots.
For Albizia coriaria, the challenge is to quantify the contribution of soil quality
improvement to the yield of crops under appropriately prune the canopy to a level of
openness needed to optimize yield of beans. A field trial comparing beans under
Albizia tree and those away from the influence of the tree but similar environment
showed that the yield of beans was 30% higher, indicating that the soil improvement properties of the leguminous Albizia can be used to improve the yield of beans in
semi-arid parts of Uganda.
Albizia coriaria is another leguminous tree that improves soil fertility and does not
compete with shallow-rooted crops such as beans. The challenge is the heavy crown
that requires appropriate pruning to allow enough light through the canopy.
Appropriate canopy openness needs to be determined.
Results from this project show that indigenous tree species have the potential to
contribute to improve the productivity of agricultural land and income of farmers.
The challenges that needs to be addressed in order to realize the full potential of
agroforestry with indigenous tree species include how to disseminate information on
appropriate tree management practice that farmers need to undertake to optimize
tree-crop interactions; testing options for integrating unconventional tree species in
new practices such as Maesopsis eminii I coffee-banana agroforestry and Faidherbia
albida in semi-arid area outside the natural range in Uganda.
A number of publications were developed including one peer-reviewed journal
article, three technical reports, a training manual on shade management for yield
optimizing in coffee-agroforestry systems and a brochure on the distribution range of
Faidherbia albida in Uganda were developed.