Alternative uses

Gliricidia is a truly multipurpose tree with a variety of uses complementing its role as a source of fodder. Its ease of establishment from large vegetative cuttings makes it suitable for living fences where it can also act as a windbreak, or as a support for climbing crops such as yam, pepper, vanilla and passion fruit. The excessive new tree growth is browsed or lopped for fodder, while the blossoms provide pollen and nectar for honeybees during the short flowering period.

Gliricidia serves a variety of soil protection and improvement purposes. As well as the fencing and support roles noted above, it is often interplanted with plantation crops as shade and to provide green manure or mulch. It has long been used as a shade tree in tropical plantations of tea, coffee and cocoa, with benefits including ease of husbandry and propagation, good coppicing, a canopy structure that permits a desirable level of shade and a deep, non-competitive root structure (Budowski et al., 1984). Associations with annual crops provide both shade and nutrients. It is this further role as a source of nutrients in alley cropping that makes it ideally suited to the improvement of farming systems through both maintenance of soil fertility for crop production and provision of high protein feed for ruminants.

Alley farming systems, developed by the International Livestock Centre for Africa (ILCA) and the International Institute of Tropical Agriculture (IITA) for the humid regions of the developing world, employ foliage to both improve the soil and to provide animal feed. They have led to increased maize yields, due to the benefits of nitrogen fixation by the root nodules and by the addition of nutrients supplied as either green manure or mulch. Timely pruning is essential since failure to remove superfluous foliage can cause decreased crop yields due to excessive shading, together with increased risk of trees being blown over during heavy storms. Foliage incorporated into the soil as green manure, rather than applied to the surface as mulch, results in faster leaf decomposition and nutrient release. In drier areas and areas subject to soil erosion, mulching may be more appropriate to reduce soil temperature and increase soil moisture retention. Wilson et al., (1986) suggested that shrubs may be more suitable than herbaceous legumes for soil restoration in the humid tropics. The nitrogen released from decomposing plant tissue may be more important than that exuded from roots in such environments.

In numerous agroforestry systems, nutrient release by leaf decomposition is regarded as the most important factor in the restoration of soil fertility. Roskoski et al., (1982) measured rhizobial activity in situ in a 20-year-old stand of G. sepium and estimated annual nitrogen fixation to be only 13 kg/ha/year. In comparison, Yamoah et al., (1985) reported that prunings released 252 kg nitrogen/ha/year when G. sepium was intercropped with maize. This would represent nitrogen both from the soil and from rhizobial fixation. While Gliricidia is known to form nodules, there is little information available regarding the efficiency of nitrogen fixation under normal farm conditions.

As a source of nitrogen and organic matter, Gliricidia is often added to rice fields at mudding up. Gliricidia compost was compared with cow, pig, goat, and poultry manure for effects on rice growth. The highest grain yield, 5.7 t/ha, resulted from the application of both Gliricidia and pig manure (Joseph and Kurakose, 1985).

A balance should be sought between the use of the foliage as mulch, as green manure or as fodder, depending upon the nature of the farming system. The deep rooting habit of leguminous trees is an important feature in the prevention of soil erosion, especially with increased cultivation of more precarious hillsides.

Aken'Ova and Atta-Krah (1986) noted additional benefits of improved weed control in alley cropping, while Obando (1987) indicated a possible allelopathic effect of Gliricidia on the common weeds Bidens pilosa and Melanpodium perfoliatum in Costa Rica. Sclerotial viability of Rhizoctonia solani, a pathogen of rice, is reduced by the addition of green Gliricidia leaves to the soil (Lakshmanan and Nair, 1984). Hot water infusions of the leaves are used as pesticides against external parasites of livestock, including dogs, and chopped leaves placed in the nests serve a similar purpose in poultry husbandry (NFTA, 1989).

Hot compresses of Gliricidia leaves, bark and roots are used to treat wounds, warts and bites, and skin rashes are cured by bathing in hot water infusions of the leaves (NFTA, 1989).

The wood of Gliricidia is hard and heavy (specific gravity 0.75) with a coarse texture and irregular grain. It is not easy to work but finishes smoothly and is extremely durable. It is used to fashion agricultural implements and small carpentry items which show great resistance to termites and decay. While Soetrisno et al., (1984) produced satisfactory wood pulps in Indonesia, Yantasuth et al., (1985) considered G. sepium unsuitable for pulping in Thailand.

A calorific value of 4900 kcal/kg is commonly cited for Gliricidia when used as a fuelwood, and it has been described as an outstanding fuelwood tree by Brewbaker et al., (1982)