Erythrina is native to the tropics and subtropics from Bolivia to Panama, and naturalized to Central America, Africa, and Malaysia. Erythrina grows rapidly, produces abundant biomass, is easily propagated from cuttings, coppices well, and fixes nitrogen. The wood, however, is generally of poor quality. In Costa Rica local farmers know Erythrina for its potential to improve soil quality. Conditions at the research site are a Typic Humitropept soil type, a mean annual temperature of 20.5¡C, and annual precipitation of 2,636 mm.

A selection program is a major component of the nitrogen-fixing-tree program at CATIE. It includes an arboretum containing 28 species, a clonal archive with six local species, and clonal trials. The program was implemented to collect and preserve genetic germplasm, to evaluate the material collected for use in agroforestry systems, and to serve as a source of material for local distribution. A nursery was established to supply CATIE and other national institutions.

Trials

Protein supplement. As animal fodder Erythrina was more palatable to ruminants than G. sepium. When compared with concentrates for increasing weight gain and productivity, Erythrina was not as effective, but is a more affordable alternative. However, the presence of alkaloids in the seeds may limit potential use as animal feed. The presence of such alkaloids in the foliage of selected clones is being evaluated.

As a source of green manure, Erythrina yielded almost 12 tons/ha/yr when cut back to the crown twice yearly. Erythrina is also being evaluated as a mulch for cassava, maize and beans. Applied a rate of 40 tons/ha (8t/ha/DM) a mulch of E. poeppiginia has maintained maize and bean yields at 3t/ha and 1t/ha for more than eight years without any application of mineral fertilizer.

Alley cropping trials are testing the effect of E. peoppiginia on associated maize and beans since 1982. Trees were planted at 6 x 3m spacing and pruned twice yearly. Bean yields increased significantly with the application of prunings; maize yields began showing increases only in the 7th and 8th years of the trial. Soil tests showed increases in K but decreases of available P in the alley-cropping system: accumulation of P in the tree stump may be significant where P is limiting.

There is little quantification of the N fixed by Erythrina; long-term studies are underway. In alley cropping systems, a response to mineral N was frequently observed with beans but not with maize. Nodulation is currently being studied by the University of Costa Rica.

Shade. Erythrina is widely used as a shade tree for coffee and cacao because of its rapid growth rate. A 2.5m stake of E. poeppiginia planted at the CATIE site can grow up to 4.5m in 6 months, with a diameter of 8-10cm.

Other trials are evaluating Erythrina as a shade treefor cocoa, coffee, pepper, and true yams. As a coffee shade, E. poeppiginia can produce the same yield increase as 132 kg/ha of mineral N. In Central America Erythrina is primarily used for live fencing. Research is being done to determine optimal spacing, and cutting regimes. Biomass production, but not fodder quality, was found to decrease when trees were pruned less than every six months; however it is unlikely that a fence can be a significant source of animal feed.

For more information:

Donald L. Kass, Coordinator IDRC Projects
CATIE, Turrialba, Cosa Rica
Fax: 506-56-1533