Erythrina edulis
Introduction '''''Erythrina edulis''''' ('''basul''') is a nitrogen fixing tree that is native to the Andean region from western Venezuela to southern Bolivia. Nowadays it is known in Venezuela as "frijol mompás", in Bolivia, Peru and Northwest Argentina as "psonay", "pajuro", "sachaporoto del basul" or "poroto del sacha", in Colombia as "chachafruto", "balú", "baluy" or "sachaporoto" and in Ecuador as "guato". Although it is widely known, it is not commonly cultivated. Future research is needed, especially in agroforestry. Basul is a legume and so it produces protein-rich beans covered in pods which can be used for human or animal nutrition. The leaves and branches can be used as fodder. Besides the agricultural aspects, ''Erythrina edulis'' can also be used as a fence plant.
Cultivation ''Erythrina edulis'' is a vigorous, fast-growing precocious legume species, and is considered one of the easiest trees to grow. As it is sensitive to the cold, it grows only in the tropics and is not suitable for temperate regions. Optimum temperatures are between ), and it grows in a broad range of altitudes (from 900 to 3200 a.s.l.). In its native habitat, the average annual precipitation varies between . ''Erythrina edulis'' grows best in well-drained soils with a sandy or clayey texture and a pH ranging from 5.5 to 7. ''Erythrina edulis'' is a totipotent plant and thus propagates easily. Hence, stems can be cut and planted into the soil and will sprout. Propagation can also be achieved by planting mature seeds and in most cases they germinate easily. Grafting is another possibility; the advantage is that seed production will start earlier. The seeds must be planted very soon after harvesting because they lose their viability 8 days after harvesting. The viability can be extended to 20 days when the seeds are covered in a thin paraffin layer. ''Erythrina edulis'' produces a raceme of red flowers, which are pollinated by bees, wasps and birds. The ripening of the seeds is not synchronized.The tree can live for decades and the older it gets, the more grain it will produce. A three- to four-year-old tree can produce about  of grain per year, while a 20-year-old tree reaches  of grain per year. Thanks to the symbiosis with ''Rhizobium'' bacteria, ''Erythrina edulis'' can fix atmospheric nitrogen and therefore does not need any additional nitrogen fertilizer.
Agricultural importance ''Erythrina edulis'' is a suitable crop for agroforestry. Thanks to nitrogen fixation, other crops included in an intercropping system with ''E. edulis'' benefit from higher nitrogen content in the soil, and the tree has potential to make wasteland more productive.''E. edulis'' can produce food during scarcity, because the seeds are normally ripe when the previous year's stocks are exhausted but when it is still too early for the new harvest. The trees can be grown in association with other cash crops as sugar cane, coffee and cacao. A basul tree can grow very high (). As it provides shade, the tree can serve to protect sun-sensitive crops from strong radiation. This association is beneficial not only for the sun-sensitive crop but also for basul, since it is less harmed by pests when grown in association with other plants, compared to a monoculture. Combinations with coffee, cacao, pepper, betel and grape have been observed.Because of the advantages of spatial diversity and the sustainability of agroforestry systems, this form of cultivation continues to gain importance. Little is known about ''Erythrina edulis'', even in the origin region, apart from some rural areas of Colombia.
Basul as a food source Basul can be used as a food source for humans and animals. The tree carries pods with grains. The length of these pods varies between , with an average around . The green pods can be eaten, but it is more common to eat the mature grains. Every pod contains 6 grains, which are  long and have a weight between . The fresh grains have a high water content, around 80%. Due to this water content, the grains cannot be stored very well. On dry matter basis, the grains have a protein content between 18 and 23%. The protein is composed like protein in most legumes, with a high lysine content and lower concentrations of sulfur-containing amino acids (methionine and cysteine) and tryptophan. The grains also contain a high amount of starch (26-40%). The amino acid pattern of the seeds of ''Erythrina edulis'' forms a good complement to cereals and tubers.To use the grains in human food, they need to be boiled or fried for at least 45 minutes. If the grains are eaten raw frequently, they can be toxic because they contain some alkaloids. All the other ''Erythrina'' species contain much more alkaloids and are thus much more toxic. Some of these species resemble ''E. edulis''; the difference is clear for a trained eye, but less experienced people should be careful with harvesting and eating the beans.The cooked beans can be used in soups, cakes, salads, tortillas etc. They can be dried after the boiling process, ground and used as flour for different purposes.The grains are not yet very common. Usage is typically limited to periods when other food supplies are scarce, but the South American governments are advertising ''E. edulis'' in the Andes. For example, they distribute recipes to raise awareness of this possible food source. Also the Colombian government is trying to conserve these beans in cans with the aim to provide an opportunity to store them longer and to open the export market.The leaves, seeds, and pods can all be used as animal fodder. The leaves have a high protein content (around 24%), and are rich in potassium and poor in calcium. When the pods and grains are used as fodder for chickens, fish, pigs or rabbits, they need to be boiled first, otherwise they can be toxic because of the alkaloids. The boiling process is not necessary when the pods and grains are fed to goats and cattle.
Future improvements The tree does not have a particular harvest time. The harvest times vary for each tree, even between trees grown in the same location. The grain is often used when other food is scarce, for instance during the rainy season. This is good for small farmers who only use the products from their own farm for feeding their family and animals, but not for breeding. One of the goals is to synchronize the harvest time of all the seeds in one cultivar.Another goal is to find a solution for the storage problem. The seeds cannot be stored due to the high water content, so finding or developing a cultivar with a lower water content in the seeds has value. Presently this problem is avoided by making flour from the seeds very soon after harvesting. Also the viability of the seeds needs to be improved. ''Erythrina edulis'' is not produced on a large scale yet, but the tree has potential for small-scale farmers because of the different uses (food, fence, fodder,...). Also, in South America, and as well in the rest of the world, very few crops are cultivated and used as both food and fodder sources. ''Erythrina edulis'' can change this and can benefit biodiversity.
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