Evaluation of fuel wood and maize production in woodlot system of Leucaena leucocephala and Senna siamea

A study was conducted at the Institute of Reneiab1e Natural Resources (IRNR) farm, University of Science and Technology (UST), Kumasi-Ghana from April 1997 to July 1998 to determine the fuelwood production from woodlots of Leucauna leucocephala and Senna sianlea 5 years and 8 months after coppicing and to evaluate the performance of maize in the woodlot fields after the trees have been clear-felled. The two tree species were established in April 1988 using seedlings raised in plastic containers. Leucaena leucocephala was planted at 1m x 2m spacings (5000 plants/ha) while Senna siamea was planted at 2m x 3m spacings (1666 plants/ha) . The first harvesting of wood from the woodlots had been done in April 1992. In April 1997 and 1998, four sampling plots were demarcated within each woodlot and the trees within the demarcated plots evaluated for height, diameter at breast height (DBH) and above- ground biomass production. The two species were also assessed for their energy potential (specific gravity and calorific value) Maize crop (variety “Obatanpa”) was grown after wood harvesting for the two main seasons using fertilizer application of 0-0-0, 30-15-15 and 60-30-30 N-P-K kg/ha in the two woodlot and in an adjacent natural fallow plot. The fertilizer treatments were randomly allocated in the three fallow systems in an andomized Complete Block Design with three replicates. oj1 samples were collected at 0-15cm depth after land clearing in the three areas and at the end of the cropping season and analysed for particle size distribution, pH, total N, Organic C and exchangeable cations. The results of the study showed that, five years after coppicing, mean height varied from 7.17m for Leucaena to 12.839 for Senna. Diameters at breast height were 3.47cm for Leucaena and 6.65cm for Senna. Fuelwood productions (oven-dry weight) were 58.78 t/ha and 209.24 t/ha for Leucaena and Senna respectively Eight months after coppicing (third coppicing), Leucaena reached 2.22m with DBH of 1.26cm while mean height and mean DBH of Senna were 4.39m and 2.7cm respectively. Fuelwood productions (oven-dry weight) were 5.13 t/ha and 17.34 t/ha for Leucaena and Senna respectively. Wood specific gravity of 5 year old coppice regrowth vari’d from 0.71for Leucaena to 0.73 for Senna. Calorific values were 4672.6 cal/g for Leucaena and 4596.0 cal/g for Senna. Total energy content was 274.6 x 10 Kcal/ha and 961.6 x 100 Kcal/ha for Leucaena and Senna respectively. Results of the soil analysis showed that the three fallow systems (Leucaena woodlot, Senna woodlot and natural fallow) brought about noticeable enrichment to the soil particularly with respect to organic matter and exchangeable bases within the first 15cm of the soil profile. Soil textural analysis showed that there was an amelioration of soil structure through the increase in silt content and the reduction in sand and clay contents. During the first two years of cropping after fallow clearing, maize grain yields without fertilizer declined from 1.54 to 0.63 t/ha, 1.98 to 1.42 t/ha and 2.21 to 1.07 t/ha in Leucaena woodlot, Senna woodlot and natural fallow plots respectively. At 30-15-15 N.P.K. kg/ha, yields declined from 3.38 to 2.27 t/ha, 3.08 to 2.39 t/ha and 3.1 to 1.84 t/ha in Leucaena woodlot, Senna woodlot and natural fallow plots respectively. With the addition of 60-30-30 N.P.K kg/ha, the decreases were 3.92 to 3.48 t/ha, 4.00 to 3.15 t/ha and 3.76 to 2.47 t/ha in the Leucaena woodlot, Senna woodlot and natural fallow plot respectively. Thus, the rates of yield decline without fertilizer were 142.5, 39.4 and 106.3% in Leucaena, Senna and natural fallow respectively. At half rate of fertilizer, yields declined by 49, 2\4 and 68.7% respectively in Leucaena woodlot, Senna woodlot and natural fallow plots respectively. At full rate of fertilizer, the rates of decline were 12.7, 26.9 and 51.9% in Leucaena woodlot, Senna woodlot and natural fallow respectively. It is concluded that at low and high fertilizer inputs, maize grain yields in Leucaena and Senna woodlots can be maintained at a higher level than in natural fallow; while without fertilizer, Senna sianiea woodlot can sustain yield better than Leucaena woodlot and natural fallow. The sustainability and the benefits of biomass obtained from coppicing (fuelwood, construction material and fodder) make the woocilot system more beneficial than the natural fallow system.

Source: KNUST