Abstract:
This study examined the hypothesis that incorporation of Gliricidia sepium (Jacq.) Walp.) (gliricidia), a fast-
growing, nitrogen-fixing tree, into agroforestry systems in southern Malawi may be used to increase the input of
organic fertilizer and reduce the need for expensive inorganic fertilizers. The productivity of maize (Zea mays L.),
pigeonpea (Cajanus cajan L.) and gliricidia grown as sole stands or in mixed cropping systems was examined at
Makoka Research Station (latitude 15 ◦ 30 ′ S, longitude 35 ◦ 15 ′ E) and a nearby farm site at Nazombe between
1996 and 2000. Treatments included gliricidia intercropped with maize, with or without pigeonpea, and sole stands
of gliricidia, maize and pigeonpea. Trees in the agroforestry systems were pruned before and during the cropping
season to provide green leaf manure. Maize yields and biomass production by each component were determined
and fractional light interception was measured during the reproductive stage of maize. Substantial quantities of
green leaf manure (2.4 to 9.0 Mg ha −1 year −1 ) were produced from the second or third year after tree establishment.
Green leaf manure and fuelwood production were greatest when gliricidia was grown as unpruned sole woodlots
(c. 8.0 and 22 Mg ha −1 year −1 respectively). Improvements in maize yield in the tree-based systems also became
significant in the third year, when c. 3.0 Mg ha −1 of grain was obtained. Tree-based cropping systems were most
productive and exhibited greater fractional light interception (c. 0.6 to 0.7) than cropping systems without trees (0.1
to 0.4). No beneficial influence of pigeonpea on maize performance was apparent either in the presence or absence
of gliricidia at either site in most seasons. However, as unpruned gliricidia provided the greatest interception of
incident solar radiation (>0.9), coppicing may be required to reduce shading when gliricidia is grown together
with maize. As pigeonpea production was unaffected by the presence of gliricidia, agroforestry systems containing
gliricidia might be used to replace traditional maize + pigeonpea systems in southern Malawi.
