Cassava (Manihot esculenta)

Description

Manihot esculenta, commonly called cassava, manioc, yuca, macaxeira, mandioca and aipim, is a woody shrub native to South America of the spurge family, Euphorbiaceae. Although a perennial plant, cassava is extensively cultivated as an annual crop in tropical and subtropical regions for its edible starchy tuberous root, a major source of carbohydrates. Though it is often called yuca in Spanish America and in the United States, it is not related to yucca, a shrub in the family Asparagaceae. Cassava is predominantly consumed in boiled form, but substantial quantities are used to extract cassava starch, called tapioca, which is used for food, animal feed, and industrial purposes. The Brazilian farinha, and the related garri of West Africa, is an edible coarse flour obtained by grating cassava roots, pressing moisture off the obtained grated pulp, and finally drying it (and roasting in the case of farinha). The cassava root is long and tapered, with a firm, homogeneous flesh encased in a detachable rind, about 1 mm thick, rough and brown on the outside. Commercial cultivars can be 5 to 10 cm (2.0 to 3.9 in) in diameter at the top, and around 15 to 30 cm (5.9 to 11.8 in) long. A woody vascular bundle runs along the root's axis. The flesh can be chalk-white or yellowish. Cassava roots are very rich in starch and contain small amounts of calcium (16 mg/100 g), phosphorus (27 mg/100 g), and vitamin C (20.6 mg/100 g). However, they are poor in protein and other nutrients. In contrast, cassava leaves are a good source of protein (rich in lysine), but deficient in the amino acid methionine and possibly tryptophan. Cassava is the third-largest source of food carbohydrates in the tropics, after rice and maize. Cassava is a major staple food in the developing world, providing a basic diet for over half a billion people. It is one of the most drought-tolerant crops, capable of growing on marginal soils. Nigeria is the world's largest producer of cassava, while Thailand is the largest exporter of cassava starch. Cassava is classified as either sweet or bitter. Like other roots and tubers, both bitter and sweet varieties of cassava contain antinutritional factors and toxins, with the bitter varieties containing much larger amounts. It must be properly prepared before consumption, as improper preparation of cassava can leave enough residual cyanide to cause acute cyanide intoxication, goiters, and even ataxia, partial paralysis, or death. The more toxic varieties of cassava are a fall-back resource (a "food security crop") in times of famine or food insecurity in some places. Farmers often prefer the bitter varieties because they deter pests, animals, and thieves. In 2016, global production of cassava root was 277 million tonnes, with Nigeria as the world's largest producer having 21% of the world total. Other major growers were Thailand, Brazil, and Indonesia. Cassava is one of the most drought-tolerant crops, can be successfully grown on marginal soils, and gives reasonable yields where many other crops do not grow well. Cassava is well adapted within latitudes 30° north and south of the equator, at elevations between sea level and 2,000 m (6,600 ft) above sea level, in equatorial temperatures, with rainfalls from 50 mm (2.0 in) to 5 m (16 ft) annually, and to poor soils with a pH ranging from acidic to alkaline. These conditions are common in certain parts of Africa and South America. Cassava is a highly-productive crop when considering food calories produced per unit land area, per unit of time. Significantly higher than other staple crops, cassava can produce food calories at rates exceeding 250,000 kcal/hectare/day, as compared with 176,000 for rice, 110,000 for wheat and 200,000 for maize (corn). Cassava, yams, and sweet potatoes are important sources of food in the tropics. The cassava plant gives the third-highest yield of carbohydrates per cultivated area among crop plants, after sugarcane and sugar beets. Cassava plays a particularly important role in agriculture in developing countries, especially in sub-Saharan Africa, because it does well on poor soils and with low rainfall, and because it is a perennial that can be harvested as required. Its wide harvesting window allows it to act as a famine reserve and is invaluable in managing labor schedules. It offers flexibility to resource-poor farmers because it serves as either a subsistence or a cash crop. Worldwide, 800 million people depend on cassava as their primary food staple. No continent depends as much on root and tuber crops in feeding its population as does Africa. In the humid and sub-humid areas of tropical Africa, it is either a primary staple food or a secondary costaple. In Ghana, for example, cassava and yams occupy an important position in the agricultural economy and contribute about 46 percent of the agricultural gross domestic product. Cassava accounts for a daily caloric intake of 30 percent in Ghana and is grown by nearly every farming family. The importance of cassava to many Africans is epitomised in the Ewe (a language spoken in Ghana, Togo and Benin) name for the plant, agbeli, meaning "there is life". In Tamil Nadu, India, there are many cassava processing factories alongside National Highway 68 between Thalaivasal and Attur. Cassava is widely cultivated and eaten as a staple food in Andhra Pradesh and in Kerala. In Assam it is an important source of carbohydrates especially for natives of hilly areas. In the subtropical region of southern China, cassava is the fifth-largest crop in term of production, after rice, sweet potato, sugar cane, and maize. China is also the largest export market for cassava produced in Vietnam and Thailand. Over 60 percent of cassava production in China is concentrated in a single province, Guangxi, averaging over seven million tonnes annually.