Distribution
Barley is grown in more than 100 countries: the 10 main barley producers (Russian federation, France, Germany, Ukraine, Canada, Australia, Spain, Turkey, UK and USA) account for 75% of the total world production. Barley importers include countries that use it primarily for feed, as Saudi Arabia (29% of exported barley), Iran and Syria, and beer producers like Belgium and the Netherlands (FAO, 2011; OECD, 2004).
Though its origin is still debated, it is believed that wild barley is an indigenous plant in the Middle East and adjacent regions of North Africa. It was domesticated more than 7000 years ago (Cecarelli et al., 2006; OECD, 2004). Its cultivation spread from the Middle East to northern Africa, and moved South along the Nile, into Ethiopia, as early as 5000 BCE (Cecarelli et al., 2006). It spread to northern and western Europe and later to North America, Australia, and southern Africa (Ellis, 2002).
Modern barley is the most widely distributed cereal crop (Ecocrop, 2011; Duke, 1983). Barley is cultivated from 70°N (in Norway) to 17°N (around tropical Timbuktu, Mali). It can be found down to 53°S in southern Chile (Ecocrop, 2011). Barley is commonly found at higher latitudes, higher elevations and in drier places than cereals such as wheat and oats. Thanks to its short growing season (some cultivars mature in 60-70 days), it can be found at higher latitudes than wheat (Duke, 1983) and it does well in areas that are too hot or dry for wheat because it ripens before harsh conditions occur. In the tropics, barley is found at higher elevations than other cereals (above 1800 m and up to 4500 m in the Himalayas) (Ecoport, 2011).
Optimal growth conditions are an annual rainfall ranging from 190 mm to 1760 mm, average day temperatures of about 20°C and soil pH between 4.5 and 8.3 (Duke, 1983). Barley thrives on well-drained, fertile loams or light clay soils and does better on alkaline than on acid soils. Low pH may induce aluminium toxicity (Duke, 1983). Barley does not withstand waterlogging but has good salt tolerance (up to 1% salt in the soil)(Duke, 1983).
Barley is grown as a winter crop in areas with comparative mild winters, as in Mediterranean basin and India (Duke, 1983). In other regions, such as the highlands of Ethiopia, barley can be cropped twice a year. Barley can be sown with wheat in mixed cropping systems, examples being in Eritrea and northern Ethiopia (Cecarelli et al., 2006).