Management

Gliricidia tends to shed its leaves during the dry season and in Central America flowering and fruiting often take place while the trees are bare (February to April). In parts of Asia and the South Pacific, flowering is in the wet season and seed production is then often poor. Mature pods are strongly dehiscent, throwing their contents up to 25 m from the parent tree and creating problems for seed collection. The seeds show no dormancy, germinating readily as soon as moisture becomes available. If the opening rains are followed by a dry spell, many seedlings growing from naturally dispersed seed will die before they can become established. While there is considerable variation between individual trees, Gliricidia is not generally a heavy seeder (Salazar, 1986; Atta-Krah, 1987), although the seed maintains viability for well over a year when stored at 17°C and 50% humidity (NFTA, 1986). Trees grown from seed appear to produce stronger and deeper root systems than those which are vegetatively propagated, so are more suitable for use on sloping land, or where drought and high winds are potential problems.

Propagation by long stakes is easy, giving rise to the Caribbean common name of quickstick. Mature, leafless cuttings (6-12 months growth), 0.5-1.5 m long, produced a strike rate of some 85% when bark stripping was combined with regular watering (Glover, 1986). Chadhokar (1982) reported best results from fresh stakes 1.0-1.5 m in length and 3-5 cm in diameter, when about 15 cm of the stake was embedded in the soil. Coating the exposed ends with vaseline, wax, mud or polythene aided survival by reducing moisture loss.

The ease of vegetative propagation and the widespread use of Gliricidia as living fence posts established from long stakes, coupled with seed production difficulties, has probably resulted in the exploitation of only a small proportion of the existing germplasm. There are collections of seed held at international centres such as the Nitrogen Fixing Tree Association in Hawaii and the Oxford Forestry Institute in the UK (NFTA, 1989). Testing these seed resources should be given priority, although there would appear to be scope for further collection and selection from native populations in order to obtain provenances with desirable characteristics before the gene base becomes further eroded. Wider use of seed would enable superior individuals to be selected from both natural and artificially established populations.

In alley cropping, in order to leave adequate space for annual crops, it is common to plant the trees in rows 4-10 m apart on flat land, reducing the spacing to 2-3 m as the slope of the land increases. In either case, spacing within the row is 10-50 cm. The trees are pruned at the end of the first year and subsequently managed with periodic cutting of re-growth to prevent excessive shading of the inter-planted crops. It has been reported that delaying the age at first cutting encourages root development. Chadhokar (1982) recommended one or two harvests per year for the first two or three years, followed by an 8-12 week cutting cycle (4-5 cuts/year) to maximize the yield of foliage. Two cuts during the wet season delayed leaf fall and flowering during the subsequent dry season (Simmonds, 1951). Reduction of the leaf canopy at this time also protected trees from the ravages of storms and hurricanes in the Caribbean.

Little work has been reported on tree spacings for forage production. Unlike Leucaena, which can be easily maintained as a hedge for direct grazing, Gliricidia does not respond well to repeated cutting close to ground level, although NFTA (1989) reported that it would tolerate a cutting height of 40-90 cm. Partly as a result of its use as living fence posts, it is common to see the trees growing with a single trunk to a height of at least 1.5 m, branching profusely above that height. This implies management under what would be basically a cutting regime and the optimum pattern and density in plantations would then be determined by the methods of harvesting and transporting the cut material. Densities in excess of 3000 trees/ha are probably rare in practice, although NFTA (1989) noted spacings of 1.0 x 0.25 m in protein banks and Wiersum and Dirdjosoemarto (1987) quoted spacings ranging from 1 x 1 m to 2.5 x 2.5 m for woodlots in Indonesia. In fence lines, spacings of 0.5-3.0 m are common.

Under a cutting regime, some of the cut material is usually fed fresh to livestock, although sun-dried leaf material is easy to store for later use. Dried foliage is well accepted. Gliricidia lacks the fermentable carbohydrates necessary to make high quality silage unless it is ensiled with molasses and formic acid additives (Kass and Rodriguez, 1987). Wilting also improves the quality of the silage.

At wide spacings of 10 x 10m in a parkland grazing system, Gliricidia can provide shade and foliage to animals and small quantities of nitrogen to the companion grass species without reducing grass yield through excessive shading.