Proceedings of a workshop on research methodologies Medan ...

at 40 d intervals (Siregar, 1983), as opposed to 39.4 tons if cut at 150 cm and 70 d
intervals (Krishnamurthy and Mune Gowda, 1982). Horne et al. (1985), in reviewing
the effect <strong>of</strong> plant density (tree per M 2 ) on the yield (per ha per year) <strong>of</strong> Leucaena, has
indicated that Leucaena planted at higher density produced better yields than at lower
density.
Leaf yield <strong>of</strong> E. poeppigianagrown at 6 m x 6 m spacing in a Costa Rican c<strong>of</strong>fee
plantation increased as the prunning frequency increased for 1, 2 and 3 times per year,
while the reverse was true for the stem yield (Pezo et al., 1989).
Planting systems have also been shown to affect yields (Nitis et a/., 1991).
Gliricidiasepiumplanted as fence (0. 1 m spacing) as alley cropping (0.5 m spacing) and
as guard row (1.0 m spacing) and harvested 4 times a year, produced 0.2, 1.5 and 1.9
kg DM per tree per year, respectively. However, when the yield was expressed per 100
m row, the DM yield become 207, 297 and 195 kg DM, respectively.
Experiments in dryland farming aieas showed that :ihrub legumes grown as fence
and cut at 1.5 m height produced more forage during the 4-month wet season than
during the 8-month dry season (Nitis et al., 1989). A similar trend was also observed
for fodder trees lopped at 2 m height.
Topography was shown to be a source <strong>of</strong> variation in yield (Nitis et al., 1989).
Leucaena and Hibiscus grown on a flat area produced more fodder than either on
slopes or flat-sloped areas. The reverse apparently occurs with Gliricidia.
Yields <strong>of</strong> FST vary according to their association with other forage species (Nitis
et al., 1989). During the wet season, yield <strong>of</strong> Gliricidia was the highest when in
association with Cenchrus and during the wet season the yield was highest when in
association with Hibiscus. For Leucaena, yield was the highest when in association with
Grahamstylo during both the wet and dry seasons. Among fodder trees, yield <strong>of</strong> Ficus
was highest when in association with Verano stylo, while yield <strong>of</strong> Lannea was higher
when in association with Grahamstylo during the wet season and with Gliricidiaduring
the dry season. Association with food crops such as sweet potato and cassava increased
the leaf yield <strong>of</strong> Acacia, Peltophorum, Leucaena and Eucalyptus by 257, 255, 250 and
196%, respectively (Petmak, 1983).
Predicting the Yield
Dry matter biomass production <strong>of</strong> tree stands has been estimated using simple
equations (Petmak, 1983). However, plant characteristics and age can affect accuracy
<strong>of</strong> predictions. Khan and Pathak (1989) showed that in predicting the leaf yield <strong>of</strong>
Leucaenagrown under wet land conditions, the age <strong>of</strong> the plant, height and site <strong>of</strong> the
diameter should be taken into account. For instance, when Leucaena was 4.5 years old,
the collar diameter (CD) was a better variable to estimate yield, while for 7.5 years old
I ::caena, the diameter at breast height per se was not a good predictor.
Shrub and Tree Fodder Quality
Chemical composition
Various studies on the chemical composition <strong>of</strong> FST in Malaysia (Devendra, 1979),
the Philippines (Gerpacio and Castillo, 1979), Nepal (Panday, 1982), India (Ranjhan,
1985), and Indonesia (Nitis et al., 1985) have concluded that the crude protein (CP)
content <strong>of</strong> the leaves is higher than that <strong>of</strong> natural grasses. Nutrient concentration
varies within and between the shrub and tree species (Panday, 1982). Leaves <strong>of</strong> Ficus
clavata contained high CP and ash; while leaves <strong>of</strong> Ficus lacor contained high crude
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