Agroforesto:Systems 16: 119--128, 1991. © 1991 Kluwer Academic Publishers. Printed in the Netherlands.

Fuelwood production from Leucaena leucocephala established in fodder crops at Mtwapa, Coast Province, Kenya

B. J A M A 1 and A. GETAHUN 2 i International Council for Research in Agroforestry, P. O. Box 30677, Nairobi, Kenya; 2 p. O. Box 62360, Nairobi, Kenya

Key words: fuelwood, Leucaena Ieucocephala, agroforestry, intercropping, single-lines, double- lines, fodder production, yields

Abstract. Fuelwood production from a high density leucaena-based fodder production experi- ment at Mtwapa, Coast Province, Kenya is reported. Leucaena with and without other fodder crops namely, Cassava, Bana and Napier grass, formed the main-plot treatments while leucaena densities ranging from 6;250 to 100,000 ha -I planted in single- or double-line planting arrangements formed the sub-plot treatments of the split-plot design used. Each treatment was replicated four times. The experiment was established and maintained without the use of fertilizer, pesticides, irrigation. Hand weeding was done only during the first year.

After 2.7 years growth, height and diameter measurements were taken before cutting back the leucaena stems to 0.5 m above ground. Utilizable fuelwood (twigs greater than 0.5 mm diameter) was then sun-dried for 3 months and dry weights taken.

Fuetwood yields were significantly reduced by the fodder intercrops. Yield from leucaena intercropped with fodder crops were, on average, 30% lower than yield from sole stands of leucaena. Mean yields of the single-line plantings ranged from 13.7 to 21.2 tons ha-:. Yield from the double-line plantings were lower (on average 10%) than that of single-line plantings and were as well highly variable. Unlike tree heights, diameters in the single-line planting arrangement were not affected significantly by the fodder intercrops. In the single line plantings, yield of fuelwood from sole stand of leucaena was higher at all in-row spacings than the yield from intercropped leucaena. Increase in in-row spacing of leucaena generally led to reduced yield of fuelwood.

Fodder yields of intercropped Cassava, Bana and Napier grasses were near normal in the first year but zero or negligible in the remaining 1.7 years. Implications of the prolonged tree establishment period on fodder yields after opening of the canopy are discussed.

Introduction

Energy needs of nearly 95% of households in rural Kenya is met through fuelwood and crop residues. Supply is however estimated to fall short of demand by about 40% [Beijer Institute, 1984]. In areas with high and/or increasingly growing populations, allocation of land to agriculture and live- stock production often leaves no room for fuelwood production. Integration of multipurpose trees and shrubs such as Leucaena leucocephala that provide nutritious fodder and high-energy-value fuelwood [NAS, 1980] into fodder production plots could simultaneously be managed to generate fuel- wood.

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In the humid coastal strip of Kenya, many farmers are introducing dairy animals into their farms and establishing fodder crops. In this regard, leucaena is planted by some of these farmers either in sole stands or in mixture with other fodder crops such as napier grass (Pennisetum pur- pureum) and cassava (Manihot esculenta). Casual on-farm observations however indicate that leucaena is cut back for fodder early before it has developed sufficiently large basal diameters that is necessary to support frequent coppicing. Numbers of leucaena coppice shoots (and hence fodder yields) are directly correlated with stem diameter [Brewbaker, 1987]. For farmers who could invest in a prolonged but the necessary period of leucaena establishment, resultant fuelwood harvests could contribute significantly to the households' energy and/or cash needs. For such farmers, an under- standing of the effects of leucaena spacing (i.e., stand density) and her- baceous fodder crops on potential fuelwood and fodder yields becomes important.

This paper reports effects of three fodder crops and four in-row spacings of leucaena on the yield of fuelwood harvested after 2.7 years at Mtwapa, Coast Province, Kenya. The effect of planting arrangement, i.e., single-verses double-line planting on leucaena growth and fuelwood yield is also explored.

Materials and methods

(a) Treatment, experimental design and management

Six months old seedlings of Leucaena leucocephala, var. K28 raised in polythene bags were planted in August 1985 into a previously plowed and harrowed fallow land. The trees were spaced 2 m between-rows and 0.1, 0.2, 0.4 and 0.8 m within rows. The resultant stand densities of 50,000, 25,000, 12,500 and 6,250 stems ha -1 were planted into a single-line planting arrangement experiment. Twice that density (i.e., 100,000, 50,000, 25,000 and 12,500 stems ha -1 were planted into a second adjacent experiment with a double-line planting arrangement. The double line rows were separated from each other by a 0.1 m wide clear strip. The two experiments were separated by a 4 meter wide path.

Once the task of planting leucaena seedlings was complete, fodder crops, viz, Cassava (Manihot esculenta), Napier and Bana grasses (two cultivars of Pennisetum purpureum) were planted from one-meter long cuttings into the 2-meter wide leucaena alleys. The fodder crops were spaced 1.0 x 1.0 m with a 0.5 m gap between the leucaena and the first crop rows. This spacing of fodder crops gave a stand density of 10,000 plants ha-L Neither the leucaena seedlings nor the fodder crops were irrigated.

Leucaena only and/or with Cassava, Napier and Bana grasses formed the main-plot treatments; in-row spacing of 0.1, 0.2, 0.4 and 0.8 m formed the sub-plot treatments of the split-plot design used. Each treatment was repli-

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cated four times in a randomized block design. Gross plots measured 12 X 8.0 m (i.e., 96 m2). Net plots of 10 X 6 m (i.e., 60 m 2) were used for yield assessment. No fertilizer and/or other chemicals, e.g., herbicides, pesticides were applied during the experimental period. The plots were kept weed-free by hand-weeding for one year (up to August, 1986); thereafter canopy closure smothered most weeds.

After 2.7 years growth, leucaena was cut back to 0.5 m above-ground and the utilizable fuelwood (i.e., woody material with diameter greater than 5 ram) weighed. The wood was sun-dried for 3 months at an average mean minimum temperature range of 21 to 25 °C before weighing. Due to lack of oven or moisture meter at the site, no moisture content determinations was attempted. For comparison however, this harvest after 2.7 years is com- parable to oven-dried yields from 2-4 years rotation cycles of leucaena under pure stands [Brewbaker, 1987]. Moisture at harvest depends on tree age, ranging from about 55 percent at 1 year to 45 percent at 4 years and 35 percent at 7 years [Relwani et al., 1985]. Measurements of tree height and diameter at breast height (dbh) (i.e., 1.3 m above ground) were taken in July, 1987.

Data on yield of fuelwood, tree heights and diameters were subjected to standard analysis of variance; a fixed effects split-plot model was used. Standard error of differences of means is used to separate significant differ- ences between means of treatments.

(b) Study site

The study area lies in the Coast Province of Kenya, 15 m above mean sea level, 9 km inland from the Coast, latitude 3°50'S and longitude 39°45'E. Mean annual rainfall at the site for the period 1975-1981 was 1260 ram, received in two seasons, namely "long-rains" (April-June), and "short-rains" (October-December). Total annual evapotranspiration for the same period was about 2200 ram. The mean minimum temperature was 21 to 25 °C; the mean maximum ranged from 27 to 36 °C. Relative humidity was generally above 70%.

The loamy textured soils classified as Ferric cambisols (FAO) or Incep- tisol -- Oxic tropepts (USDA classification system) are moderately acid in reaction, generally adequate in potassium, calcium and manganese but low in magnesium, phosphorous and organic matter [Bashir, 1988]. The area is nearly level, with a slope of less than 2%.

Results

Fuelwood yield

Yield of fuelwood in the single-line planting arrangement (Table 1) was

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r e d u c e d by the stat is t ical ly significant effect of the f o d d e r crops . Thus, yield of w o o d f rom the con t ro l plots ( leucaena-only) were significantly h igher than yield f rom plots i n t e r c r o p p e d with fodder . A n excep t ion to this was o b s e r v e d at 0.8 m in- row spacing. O n average, fue lwood yields of l eucaena in ter - c r o p p e d with fodde r c rops were 30% lower than that of the con t ro l plots.

The effect of in - row spacing of l eucaena was also obse rved to be highly significant. This effect was app rox ima te ly 30 t imes that of in teract ion.

F u e l w o o d yie ld dec l ined with inc rease in in - row spacing. The excep t ion to this obse rva t ion was at 0.4 m in - row spacing of l eucaena i n t e r c r o p p e d with Cassava in tercrop . This may expla in the small bu t significant in te rac t ion de tec ted . However , the effects of the ma in plots (i.e., f o d d e r in te rc rops) and sub-plo ts (i.e., in - row spacings of leucaena) were respec t ive ly 9 and 30 t imes higher than the in te rac t ion effects.

Table 1. Fuelwood yield (t ha -1 year -1) from single-line planting arrangement of Leucaena leucocephala.

Intercrops leucaena in-row spacing (m)

0.1 0.2 0.4 0.8 Mean

Control (leucaena only) 31.8 28.4 17.0 7.5 21.2 leucaena 4- Cassava 24.8 23.8 10.3 9.5 17.1 leucaena + Napier Grass 24.1 21.9 5.9 2.9 13.7 leucaena 4- Bana grass 20.4 18.1 5.7 10.4 13.7

Mean 25.3 23.0 9.7 7.6 16.4

Standard error of difference of means of intercrops x in-row spacing of leucaena = 1.7. Standard error of difference of means within the same level of intercrop ~ i .8. C.V. % intercrop x in-row spacing ~ 15.8.

Table 2. Fuelwood yield (t ha -1 year-l.) from double-line planting of Leucaena leucocephala.

Intercrops leucaena in-row spacing (m)

0.1 0.2 0.4 0.8 Mean

Control (leucaena only) 17.5 15.5 24.1 16.0 18.2 leucaena + Cassava 22.3 18.2 14.1 9.5 16.0 leucaena 4- Napier Grass 16.1 17.0 5.5 19.2 14.4 leucaena 4- Bana grass 4.7 13.2 12.7 9.7 10.1

Mean 15.1 15.9 14.1 13.6 14.7

Standard error of difference of means of intercrops x in-row spacing of leucaena = 2.9. Standard error of difference of means within the same level of intercrop = 3.1. C.V. % intercrop x in-row spacing ~ 30.5.

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In the double-line plantings, fuelwood was also affected significantly by main-plot treatments (i.e., the fodder intercrops). The control plots had a significant 26% higher yield than the mean yield of the intercropped plots. The differences between mean yields of the intercropped plots were not significant. Interaction effects were significant but small (about 7 times lower) compared to main-plot effects. Effects of in-row spacing were significant but again small compared to that of the main-plots (i.e., fodder intercrops). With the exception of the cassava intercrops that resulted in a consistent decline of yield with increase in in-row spacing, the rest of the treatments showed no particular trends. The high coefficient of variation (30%) of the yields indicates presence of large random error effects associated with the double- line planting arrangement. On average, yield of the double-line plantings were 10.4% lower than single-lines.

Tree heights

Tree heights in both planting arrangements were significantly reduced by the fodder crops compared to the control plots (Table 3). The effect was how- ever more pronounced in the double than the single-line planting arrange- ments. Differences between effects of fodder crops as well as interaction of the different fodder crops and in-row spacings of leucaena were not statis- tically significant. The lack of significant differences in tree heights between the control plots and the plots with cassava intercrop in the double-line planting arrangement (Table 3) is however noteworthy.

Table 3. Effect of fodder intercrops on heights and diameter of Leucaena leucocephala in single and double-line planting arrangements.

Intercrops Single-line planting Double-line planting

Height (m) Diameter (cm) Height (m) Diameter (cm)

Control (leucaena only) 5.2 3.4 3.8 2.7 leucaena + Cassava 4.7 3.3 4.0 2.6 leucaena + Napier grass 4.7 3.3 2.7 1.8 leucaena + Bana grass 4.6 3.2 2.6 1.7

Mean 4.8 3.3 3.3 2.2

Standard error of difference of means of tree heights in single-line plantings = 0.1; C.V. % = 8.5. Standard error of difference of means of tree diameters in single-line plantings ~ 0.2; C.V. % = 20.1. Standard error of difference of means of tree heights in double-line plantings = 0.2; C.V. % 12.8. Standard error of difference of means of tree diameters in double-line plantings = 0.2; C.V. % ~ 13.7.

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Table 4. Effect of in-row spacing on height and diameter (dbh) of Leucaena leucocephala in single and double-line planting arrangements.

In-row spacings (m) Single-line planting Double-line planting

Height (m) Diameter (cm) Height (m) Diameter (cm)

0.1 4.1 2.4 3.0 1.9 0.2 5.2 3.2 3.2 2.1 0.4 4.7 3.4 3.1 2.0 0.8 5.1 4.1 3.8 2.7

Mean 4.8 3.3 3.3 2.2

Standard error of difference of means of tree heights in single-line planting = 0.1, C.V. % = 8.5. Standard error of difference of means of tree diameters in single-line plantings = 0.2, C.V. % = 20.1. Standard error of difference of means of tree heights in double-line plantings = 0.2, C.V. % = 12.8. Standard error of difference of means of tree diameters in double-line plantings = 0.2, C.V. % = 13.7.

Generally, significant interaction between fodder crops and the in-row spacings of leucaena coupled with the negative effects of the nar row double- row planting arrangements obscured detect ion of part icular trends in tree heights. The great majority of stems in the double-l ine planting ar rangement remained stunted and were over topped by the end of the first year.

Tree diameters

While effects of bo th fodder crops and in-row spacing of leucaena on tree diameters of double-l ine planting ar rangement were significant, in the single- line plantings, only the effects of in-row spacing was statistically significant. In bo th planting arrangements, tree diameters generally increased with increase in in-row spacing of leucaena (Table 4).

Discussion

The significant reduct ions in fuelwood yield f rom treatments with fodder crops could be attributed to compet i t ion for be low-ground resources much like weeds do. Weeds have been shown to inhibit establishment of leucaena [Hill, 1970] and /o r to reduce yields at maturi ty even when weed control measures such as spot weeding was provided [Maghembe et al., 1986]. Because of their rapid rates of growth relative to cassava, the grass species

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used were generally more competitive. The negative effects of fodder crops on tree growth were manifest, for example, in the significant reductions in tree heights and diameters. The lack of significant effects of the fodder crops on tree diameters in the single-line plantings is in agreement with observa- tions of others [Maghembe et al., 1986; Lulandala and Hall, 1987].

Notwithstanding the significant but small interaction effects, yield of fuelwood and tree diameter declined consistently with increase in in-row spacing of leucaena. This observation, which is in agreement with that of others [Lulandala, 1987; Guevarra, 1978; Van den Beldt, 19821 suggests that (a) reduced stand density and, (b) reduced tree diameter are better correlated with yield of fuelwood from leucaena than tree height. Tree heights did not decline with decrease in-row spacing, an observation also made by Mag- hembe et al. [1986]. Tree height may be influenced more by site conditions than by spacing [Smith, 1962], except at very high stocking [Van den Beldt, 19821 .

In the double-line planting arrangements, tree diameters appeared to be influenced more by increased competition from the close plantings of the double rows than by the fodder crops. This planting arrangement resulted generally in higher percent mortality and poor establishment compared to the single-lines. Hence, low stand density, tree heights and diameters (Table 3) could be some of the reasons for lower yields (on average, 10%) of the double-line planting compared to the single-lines. Observations similar to this is made also by Bhatia et al. [1985] working with high density planting of leucaena.

• Of most relevance to the study's objectives were the high fimlwood yields generated after only 2.7 years of tree growth. In the single-line planting arrangement, the highest yields were obtained from 0.1 m in-row spacing with a range of 20 -32 t ha -1 year -1. This range of fuelwood represents an annual supply for 20 -32 persons in rural Kenya, assuming a consumption rate of one tonne person -1 year -1 [Beijer Institute, 1984]. An in-row spacing of 0.1 m and between-row spacing of 2 m gives a stand density of 50,000 leucaena plants ha -~. Because a planting arrangement of 2 × 0.1 m may be too narrow for on-farm conditions, the spacing could be adjusted to either 4 X 0.05 m or 8 × 0.025 m without affecting stand density. The narrow in- row spacing may be achieved by direct seeding leucaena and thihing after germination instead of planting from seedlings. In hot-humid conditions, leucaena establishes well from direct seeding if scarified and weeded initially [Duguma et al., 1988; Oakes, 1983; Takahashi and Ripperton, 1949].

In studies with no intercrops, yields closer to the ones of this study were obtained at only 10,000 plants ha -1 [Brewbaker, 1987]. The differences in yield between these two studies may be explained by differences in site, stocking and management conditions. This study however demonstrates that yield kom double-line planting arrangement is inferior to that of single-lines. Where double-line planting arrangement may still be desired (for instance, on slopy lands), more planting material, enhanced competition between rows,

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low tree-survival, reduced growth and final yield as observed in this study are likely outcomes. The use of two different species may minimize competition in double-line planting arrangements.

The lack of significant differences in effects of the fodder crops on tree diameters, particularly in the single-line planting arrangement raises issues of practical importance. It does, for instance, suggest realization of high leucaena forage from the developed stumps once the coppicing phase starts. For farmers who could afford the waiting period of stump development, the benefits could be improved yields of leucaena forage. In the first year, normal yields of Bana, Napier and Cassava fodder were realized from the inter- cropped plots. Only the control plots could therefore be considered to have had a prolonged fallow of 2.7 years. The control plots had also a higher weed load and required more time to weed in the first year than the intercropped plots. This suggests that trade-off between cost of weeding sole plots versus reduction in yield of fuelwood due to intercropping are important factors that may influence potential adoption of the technology. In the intercropped plots, costs of weeding leucaena may be covered indirectly by the intercrops.

After the first year, fodder production from the intercrops was negligible. This was due mainly to the rapid canopy closure of the narrowly spaced 2-meter wide leucaena rows and the prolonged period of tree establishment. Following harvest of fuelwood, yields of fodder crops could however increase significantly due to good weed control measures achieved. In the study area, weeds have been estimated to account for 40-42% of crop losses [Michieka, 1981]. Also, impacts of improved soil fertility that is often associated with fallow periods [Nye and Greenland, 1960] could be signifi- cant. Observations of Pathak et al [1982] of 150 and 84% increases in the respective yields of first and second fodder crop after only 2 years of leucaena fallow strengthen speculations for enhancement of soil fertility and fodder yields. In addition, biological N-fixation by leucaena could contribute to improve yields of fodder intercrops, especially in soils of low available-N such as Mtwapa.

In conclusion, this study has shown that significant amounts of fuelwood could be realized where sufficiently long periods of leucaena establishment is feasible. However, assessment of the fodder yields of leucaena and that of its intercrops after harvests of fuelwood become important follow-up studies for two reasons:--

(a) to quantify benefits associated with residual and/or current stand densities on the intercrops;

(b) to explore potentials of rotational fallow cycles to periodically provide fuelwood but also to replenish soil macro- and micro-nutrients that may be lost in fodder harvests.

Results on the above issues covering an additional 2-year period are now becoming available and will be reported in a separate paper. In summary, it has been possible to continue harvesting leucaena fodder as well as the

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replanted intercrops at least 6 times per year without any apparent soil fertility decline. The single-line plantings have continued to out-yield the double-line planting modules.

Acknowledgements

We are greatly indebted to the management of the Mtwapa Farmers' Training Centre and Mtwapa Agroforestry/Energy Centre for making the plots available for the study and managing the trials respectively. We are also grateful to Mr. P. Muraya of ICRAF for assistance in analysis of data. Our thanks also goes to Mrs. Sarah Okoth for typing the manuscript.

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