Legumes

Some species of legumes are very important as foods for humans and domestic livestock. The seeds of legumes are typically highly nutritious and rich in protein, carbohydrates, oils, fiber, and other nutrients. However, the protein-rich nature of legume seeds, a consequence of their nitrogen-fixing symbiosis, is perhaps their most important attribute as a food for animals. Numerous species of legumes are grown in agriculture, and it is likely that there are other species of legumes of potential agricultural importance that have not yet been discovered, especially in the tropics.

One of the most important agricultural legumes is the peanut or ground-nut (Arachis hypogaea), originally native to Brazil but now cultivated much more widely. After the above-ground flowers of the peanut are pollinated, their supporting stem turns and forces its way into the ground where the flowers then develop into their familiar, shelled fruits. Peanuts can be eaten raw or roasted, pulverized into peanut butter, or baked into cakes and cookies. Peanuts are also used to manufacture an edible oil. Sometimes a fungus known as Aspergillus flavus will infest stored peanuts. This fungus will excrete a potent toxic known as aflatoxin which can cause liver damage and perhaps lead to the development of cancers. In addition, some people develop an extreme allergy to peanuts, and these hypersensitive individuals can be killed by inadvertently eating any food containing peanuts.

Another very important species of legume is the soybean (Glycine max), originally native to Southeast Asia. This species can be eaten cooked or as fresh Red clover (Trifolium pratense). JLM Visuals. Reproduced by permission.

sprouts, or it can be processed into a protein-rich material known as tofu, another substance known as soy flour, or into a nutritious drink known as soy-milk. Soybeans are important ingredients in some of the meat substitutes that have recently been developed such as vegetarian hot dogs. Soybeans are also pressed to produce edible oils.

The seeds of many other species of legumes are also eaten. These include the chick pea (Cicer arietinum), lentil (Lens esculenta), common pea (Pisum sativum), broad or faba bean (Vicia faba), cow pea (Vigna sinensis), common bean (P. vulgaris), mung bean (Phaseolus aureus), Lima bean (P. lunatus), and scarlet runner bean (P. multiflorus). The entire pod of the carob (Ceratonia siliqua) can be eaten and is similar to a candy because of the naturally large concentration of sugar that it contains.

The licorice (Glycyrrhiza glabra) is a perennial herb that is native to southern Europe and Asia and is now cultivated more widely. The rhizome of licorice is mostly used in the preparation of candy and to much smaller degrees to prepare medicinals, shoe polish, and to flavor tobacco.

Some species of legumes are important in agriculture as nitrogen-rich forages for domestic livestock. Species of forage legumes that are commonly cultivated in North America include alfalfa or lucerne (Medicago sativa), sweet clovers (Melilotus officinalis and M. alba), birds-foot trefoil (Lotus corniculatus), vetches (Vicia cracca and other species), and various species of clovers, including red clover (Trifolium pratense), white clover (T. repens), hop-clovers (T. agrarium and T. procumbens), and alsike clover (T. hybridum). Legumes are also used as a so-called "green manure" or soil conditioner which is grown and then ploughed into the ground to improve the soil quality in terms of organic matter and fixed nitrogen.