A quick guide to useful nitrogen fixing trees from around the world
Gliricidia sepium trees will fully repay your efforts to obtain uniform germination and good establishment. Like other trees, initial gliricidia establishment is slow, and “tender loving care” is advisable during this period.
1. Seed Source/Provenances. Preliminary results of provenance evaluations indicate that NFTA 220, NFTA 224, NFTA 245, CFI 14/84 and CFI 16/84 are fast-growing provenances adapted to a wide range of environmental conditions. The International Livestock Centre for Africa (ILCA) has available a high-yielding bulk (HYB) seed lot which is a composite of four fast-growing provenances. The Oxford Forestry Institute has a collection of 30 provenances available for evaluation free of charge. To select the best seed source for a particular area it is recommended that 8-10 provenances, along with local provenances, be evaluated.
2. Seeds. Good seeds should be well dried, insect-free, fungus-free, and weed-free. Gliricidia has from 6,000-13,000 seeds per kg, depending on variety. Seed sources are listed annually in NFTA’s “NITROGEN FIXING TREE RESEARCH REPORTS”, or can be obtained from this address.
3. Storing Seeds. Keep seeds dry in a tightly-closed plastic bag or jar, and they will last for years, longer if refrigerated.
4. Scarification. Gliricidia seeds require no pretreatment, unlike most other leguminous trees. Just plant them. They will germinate in 7-10 days.
5. Inoculation. Gliricidia is a legume, and bacterial inoculation is necessary for good modulation and growth. In countries where gliricidia is native or naturalized, it is often well modulated by local bacteria. Thus, use of local soils in the nursery can suffice. Outside of this range, it is sometimes inoculated. If not, inoculum specifically effective for gliricidia can be obtained from NifTAL, P.O. Box “O”, Paia, Maui, Hawaii 96779
6. Transplant or Seed Directly? Gliricidia establishment is initially slow, with at least 6 weeks in the small seedling stage (to 30 cm). At this stage, seedlings are extremely susceptible to weed competition. Transplanting of nursery-grown stock will typically give higher survival rates than direct seeding because seedlings have a head-start in terms of competition. However, raising seedlings requires extra labour in the nursery and in transplanting. Good weeding is necessary if gliricidia is direct seeded. After the small seedling stage, growth is more rapid, and the trees can effectively compete with weeds.
For a small local nursery, almost any type of seedling container can be used. However, the roots of seedlings raised more than 6-8 weeks in containers spiral and become rootbound, negatively effecting their subsequent growth in the field. For this reason, seedlings should not be kept too long in the nursery, or open- ended containers should be used, and the seedlings given regular root-pruning. A rich soil mixture is recommended for the nursery. Peat or other organic matter should be added to enrich poor soils. Fungi causing damping off are not serious on gliricidia, but use of a fungicide may be advisable for large-scale production. The use of stump cuttings has been successfully practiced. Grow seedlings to at least a 1 cm diameter stem, then cut the root at 15 cm, the shoot at 25 cm, and roll in mud, or otherwise keep wet, until they are planted.
7. Cuttings. Another very useful characteristic of Gliricidia is that it starts very readily from cuttings, although root development is poor compared to that of trees grown from seeds. Recommended size for cuttings is 2-6 cm in diameter and 30-100 cm in length. Stakes should be planted at least 20 cm below the ground, and the below-ground section of the cutting should be “wounded” with several scattered cuts to promote rooting. Cuttings should be planted as soon as possible after harvesting to enhance survival rates. They should be kept in a bucket of water or wrapped in a wet cloth until they are planted, as they can loose viability when dried. Cuttings need to receive a good supply of water until they are well established.
8. Planting. We recommend spacings ranging from 1×1 m to 2×2 m for woocdlots; single rows with 50 an spacing. for living fences; in rows 1 m apart and trees 10-20 cm apart within the rows for fodder banks (forage grasses can be intercropped in these rows); and for alley cropping, planting in rows (on contours) that are 2-3 m apart. The spacing within the rows for alley cropping depends on the slope of the land. For flat to moderate slopes, 20-50 cm between trees will give maximum tree and crop production. For steeper slopes, closer spacings are recommended for better erosion control. Initial spacings as close as 2.5 cm between trees have been used successfully on very steep slopes in the Philippines. These trees should be thinned to wider spacings as they mature. Good initial land preparation and weed control are extremely important for any plantings.
9. Environment and Soil. Gliricidia is widely adapted, thriving in semi-arid to wet tropics. It prefers warm climates (mean annual temperature of at least 20oC. It does not tolerate frost. Gliricidia grows on a wide range of soil types, even in highly disturbed areas. Different provenances perform better in different conditions, and provenance trials are advisable.
10. Pests and Diseases. Aphids and some fungi can cause damage to gliricidia, however, chemical control is not advised. Young seedlings require protection from browsing animals.
11. Harvesting Seeds. Gliricidia seeds well in some areas and not at all in others. Fruiting occurs in the dry season after the trees shed their leaves. Collect pods from a large number of outstanding trees. Pods are harvested when they begin to turn yellow/brown, as the pods will “explode” to scatter seeds upon full drying. Seeds are extracted by drying the pods in the sun. Label carefully as to variety and source, and store as noted above.
For additional information, write:
Nancy Glover (author), Development Associate for Latin America, NTETA, P.O. Box 680, Waimanalo, HI 96795. (Provenances, nursery production and agroforestry systems).
Colin Hughes, Oxford Forestry Institute., South PaLrks Road, Oxford OXI 3RB,
United Kingdom (Provenances).
Akwasi Atta-Krah, IL-CA, P.M.B. 5320, lbadan, Nigeria (Provenances, alley cropping)
A publication of the Forest, Farm, and Community Tree Network (FACT Net)