Growth, wood yield and energy characteristics of Leucaena leucocephala, Gliricidia sepium and Senna siamea at age four years

Growth, wood yield, specific gravity, calorific value and chemical composition (ie. % Lignin, Alpha-Cellulose and Beta and Gamma-Cellulose Contents) were determined for Leucaena leucocephala, Gliricidia sepium and Senna siamea at age four years. The study was conducted to assess the wood biomass productivity and energy potentials of the species for use as fuel wood.

Trees were spaced 2m x 0.6m (8333 plants/ha) and were established on a gritty clay loamy soil classified as Ferric Acrisol (FAO/UNESCO) with pH ranging between 4.2 and 5.3. There were three blocks each of which carried one tree species. Within each species block, four sampling plots were demarcated and used as replications in a completely randomised design.

Tree height varied from 5. 94m for L. leucocephala to 9.16m for S. siamea and diameter at breast height from 4.46cm for L. leucocephala to 5.80cm  for s. siamea. Wood yield (on oven-dry weight) of S. siamea was 86.2 t/ha and was the highest. L. leucocephala produced 39.3t/ha and was the least. Branch of the species contributed between 12 and 24% of total wood yield. Wood specific gravity ranged from 0.63 for S. siamea to 0.67 for L. leucocephala. There was a general decrease in specific gravity from the butt end towards the crown for all the species. Calorific values did not differ significantly between species. However, stems of all species had significantly higher calorific values than branches. Chemical composition varied within and between species. Energy production of S. siamea was 385 x 10⁶Kcal/ha and was the highest for all the species. G. sepium was intermediate between S. siamea and L. leucocephala in all the parameters measured.

On selection of species for fuelwood plantation establishment, S. siamea would be a better choice than L. leucocephala and G. sepium in terms of higher wood energy production per hectare, (385 x 10⁶Kcal/ha). However, in terms of fuel burning quality expressed as Fuelwood Value Index (FVI) L. leucocephala can be the best (FVI, 2488).