multipurpose tree species research for small farms: strategies ... - part

Experiments have been established at four sites
to identify higlh-yielding shrub legumes and to
study nutrient responses in three key species. The
sites were chosen for their soil properties and are
representative of major areas to be developed for
agriculture in Soutbeast Asia. All experiments are
being harvested at t :.ce month intervals. Legumes
with great promi.: include "odariocalytv roides,
Sesbania sesban, and Cajanus cajan, while the
effect of the leiicaena psyllid has severe!y reduced
the yield of Leucaena leucocephala at most sites.
Nutritional experiments have highlighted the
general responses to phosphorus and calcium (as a
nutrient), alnd the importance of lime-induced
trace e!ement deflcicncies.
Background
In many tropical count! ies, shrub legumes are
multipurpose plants used for fodder, living fences,
hedges, shade, fuelwood, ero,.on control, and as a
source of nitrogen for other crops. They are
considered to have the potclialfor higher y¢ields
than herbaceous legumes, and to retain their leaves
longer into the dry season. In the southern
?hilippines and eastern lndonesia, farmers have
widely adopted shrub legume-based cropping
systems, which represent one of the few sustainable
food producion systems suitable for the uplands of
Soutiheast Asia.
The predoinii ant shrub legume grown is
Leucaena which has adapted to neutral and
alkaline soils, but does not thrive in the acid soils
vormmon in the tropics. At prest .; there is little
IknowLcIge of what species are most suitable for
specific soils or particular environments, or how
the plants can be managed to give sustainable
levels of increased growvfa.
Recently, Lcucaena has been severely attacked
y the psyllid, thus intensifyijg the need to search
lor possible alternative species.
Multipurpose Shrub Legumes for Infertile Soils
in the Tropics
B. Gunawan, RA. Bray, B.Palmer,M. Panjaitan
and T. Ibrahim
Research Institute for Animal Production
Bogor, Indonesia
CSIRO Division of Tropical Crops and Pastures
Cunningham Laboratory
Brisbane, Australia
191
The research objectives are to evaluate the
performance of a range of shrub legumes in
diverse soil/climatic environments; to
characterize the nutrition requirements of a
range of shrub legumes ar.1 define the soil
factors limiting their growth; and to collect and
maintaiin shrub legume genetic resources.
Some of the earlier research results have
been presented elsewhere (Gunawan et aL 1987;
Bray el al. 1988).
Methodology
The experiments consist of two types of trials:
nutritional trials and species comparison trials.
The four sites chosen for this work were Sei
Putih and Sembawa in Indonesia, and Utchee
Cieek and Silkwood in Australia. Relevant soil
ch,i racteristics are presented in Table 1.
The sites were carefully chosen so that all
were acidic and represented the soils of lowest
fertility in the region. There were similarities
between the soils at Sei Putih and Utchee Creek
in that both have low exchangeable calcium and
low aluminum saturation. The soils at Sembawa
and Silkwood both have low exchangeable
calcium and high aluminum saturation.
However, the former pair of ;oils have
developed with a relatively higher fertility status
and are expected to support higher production.
The field experiments at Semiawa and Sei
Putih were planted at the beginning of
December 1986 in good soil conditions after
adequate rainfall. The experiments at Utchee
Creek and Silkwood were planted in late
February of 1987 in rood soil conditions after an
excellent month's rain.
To be successful as a multipurpose shrub
legume for the infertile soil of the tropics any