Source: Magness et al. 1971
Barley is the fourth most important grain crop in the United States. Acreage planted in 1966 and 1967 averaged about 10.6 million, with an average yield for the two years of 381.7 million bushels.
Barley is one of the most ancient of cultivated grains. Grains found in pits and pyramids in Egypt indicate that barley was cultivated there more than 5000 years ago. The most ancient glyph or pictograph found for barley is dated about 3000 B.C. Numerous references to barley and beer are found in the earliest Egyptian and Sumerian writings.
The origin of barley is still not known. There are differing views among researchers as to whether the original wild forms were indigenous to Eastern Asia, particulariy Tibet, or to the Near East or Eastern Mediterranean Area, or both. Possibly in a crop so long cultivated this can never be resolved with certainty. J. R. Harlan, in U.S.D.A. Handbook 338, Barley: Origin, Botany, Culture, Winterhardiness, Genetics, Utilization, Pests, summarizes the evidence for different viewpoints.
Species and Characteristics of Barley
Three species of Hordeum constitute the barleys under cultivation.
They are derived species, not known as such in nature. All have 14 cbromosomes in the diploid stage and inter-cross readily. They are characterized as follows:
Hordeum vulgare L. These are 6-rowed barleys with a tough rachis or spike stem. All florets are fertile and develop normal kernels. Within the species are two groups: (1) The typical group in which lateral kernels are only slightly smaller than the central one. (2) The intermediate group in which lateral kernels are distinctly smaller than central ones. This group may contain kinds with sterile or near sterile lateral spikelets. The two groups may overlap and are not fully distinct.
Hordeum distichon L. This species is the 2-rowed barleys with a tough rachis. The central spikelets all contain a fertile flower, while flowers in the lateral spikelets are either male or sexless. Two groups of varieties occur: (1) The typical 2-row group, with lateral flowers containing lemma, palea and reduced sexual parts. (2) The deficiens group, with lateral flowers containing no sexual parts.
Hordeum irregulare E. Aberg and Wiebe. This is an irregular barley with a tough rachis, but with lateral flowers reduced in some instances to a stem piece only; and others fertile, sterile or sexless. Central spikelets contain fertile flowers and set seeds.
A number of species of Hordeum are native in various parts of the world. Hitchcock (Manual of Grasses of the United States, Ed. 2, U.S.D.A. Misc. Pub. 200, 1951) lists 11 species of barley grasses as occurring in the United States. None of the native species is in cultivation.
Barley plants are annual grasses which may be either winter annuals or spring annuals. Winter annuals require a period of exposure to cold in order to produce flowers and set seeds, thus are planted in the fall. They form a rosette type of growth in fall and winter, developing elongated stems and flower heads in early summer. If seeded in the spring they fail to produce seed heads. Winter varieties form branch stems or tillers at the base so several stems rise from a single plant. The winter varieties of barlev are more hardy than winter oats, but somewhat less hardy than winter wheat. Around a fourth of the barley grown in the United States is of winter varieties. Spring varieties do not require exposure to cold in order to devlop seed heads. Also, they do not have a typical rosette stage and so develop fewer tillers than winter varieties. They are the only kind adapted to areas with very cold winters. For best production they should be seeded as early as land can be worked in the spring.
The stems of both winter and spring varieties may vary in length from 1 to 4 feet, depending on variety and growing conditions. Stems are round, hollow between nodes, and develop 5 to 7 nodes below the head. At each node a clasping leaf develops. In most varieties the leaves are coated with a waxy chalklike deposit. The density of this varies, and in some varieties no waxiness is present and leaves are glossy. Shape and size of leaves varies with varietv, growing conditions, and position on the plant.
The spike, which contains the flowers and later the mature seeds, consists of spikelets attached to the central stem or rachis. Stem intervals between spikelets are 2 mm. or less in dense headed varieties and up to 4 to 5 mm. in lax or open headed kinds. Three spikelets develop at each node on the rachis. Barley varieties are classed as 2-row or 6-row. In 2-row varieties only the central spikelet develops a fertile flower and seed. In 6-row varieties all three of the spikelets at each node develop a seed.
Each spikelet has two glumes rising from near the base. These are linear to lanceolate and flat and terminate in an awn. The glumes minus the awn are about half the length of the kernel in most varieties, but this varies from less than half to equal to the kernel in length. Glumes may be covered with hairs, weakly haired or hairless. The awns on the glumes may be shorter than the giume, equal in length or longer. The glumes are removed in threshing.
The barley kernel consists of the caryopsis, or internal seed, the lemma and palea. In most barley varieties the lema and palea adhere to the caryopsis and are a part of the grain following threshing. However, naked or hutless varieties also occur. In these the caryopsis is free of the lemma and palea and threshes out free as in wheat. This type is grown mainly where barley is used for human food and is rarely found in the United States.
The lemmas in barley are usually awned. Awns vary from very short up to as much as 12 inches in length. Edges of awns may be rough or "barbed" (bearded) or nearly smooth. Awnless varieties are also known. In 6-row barley awns are usually more developed on the central spikelets than on the lateral ones.
The barley kernel is generally spindle shaped. In commercial varieties grown in the United States length ranges from 7 to 12 mm. Kernels from 2-rowed varieties are symmetrical. In 6-rowed varieties the third of the kernels from the central spikelets are symmetrical, but the two-thirds from lateral spikelets are twisted. The twist is most apparent at the attachment end, less conspicuous at the terminal. The dorsal surface of kernels is smooth, the ventral surface grooved.
The period from flowering until barley is ready for harvest may vary from 40 days to as long as 55 days, varying with varieties and climatic conditions.
Cultivated Variety Groups
Some 150 varieties of barley are cultivated in the United States, many on a minor scale. Varieties are constantly changing as new ones are devloped and tested while others pass out of cultivation. These varieties fall into four general groups, as follows:
Manchuria - OAC 21 - Aderbrucker Group- These are 6-rowed, awned, spring-type varieties with medium sized kernels. The type is believed to have come originally from Manchuria. Plants are tall with open or lax, nodding heads. They tend to shatter badly in dry climates. These are grown mainly in the upper Mississippi Valley and are extensively used for malting.
Coast Group. These varieties trace to North African ancestry and are grown in California and Arizona, also in the Inter-Mountain Region. They are 6-rowed, awned, with large kernels, and short to medium length stems. Spikes are medium to short, dense and generally held erect to semierect. They mature early and are not prone to shatter. They have a spring growth habit but may be fall or winter seeded in California and Arizona where winters are mild.
Tennessee Winter Group. Varieties of this group trace to the Balkan-Caucasus Region or Korea. They are 6-rowed, avrned, with mid-long lax spikes which tend to nod. Plants are medium tall, of winter habit. These varieties are fall seeded and are grown in the southeastern quarter of the United States.
Two-rowed Group. This group includes types tracing to Europe and Turkey--the Turkish type being adapted to areas with marginal rainfall. Varieties in this group are grown principally in the Pacific and InterMountain States and to some extent in the Northern Great Plains. Varieties are mainly spring type though 2-rowed winter varieties are known. Some varieties are used mainly for malting, others for feed.
Half or more of the barley grown in the United States is used for livestock feed. As feed it is nearly equal in nutritive value to kernel corn. It is especially valuable as hog feed, giving desirable portions of firm fat and lean meat. The entire kernel is used in feed, generally after grinding or steam rolling. Malt sprouts from malting as well as brewers grain--byproducts of brewing--are also valuable livestock feeds.
Around 25 percent of the barley crop is used for malting in the United States. Of the malted barley some 80 percent is used for beer, around 14 percent for distilled alcohol products, and 6 percent for malt syrup, malted milk and breakfast foods. For malting, the barley is steeped in aerated water in large tanks for 45 to 65 hours, then transferred to germinating tanks or compartments where it is held with intermittent stirring for 5 to 7 days at temperatures of 60-70°F. During this treatment root sprouts emerge, but not the stems. This "green" malt is then dried in hot air kilns. For making beer the dried malt is crushed between rollers, mixed in proper proportions with slightly warm water, and held under rigidly controlled temperatures. The starch is converted by enzymatic reaction into maltose and dextrins. Proteins are also broken down by enzyme action. Upon completion of this process the solids settle out, the extract is filtered, then boiled with hops to add flavor, then cooled. Yeast is added to ferment the sugars into alcohol and carbon dioxide. The hop residue and proteins are then removed and the product (beer) is aged, chilled, filtered, pasteurized and bottled. Keg beer is similar but is not pasteurized or bottled. The solids from this process (brewer's grain) are a valuable livestock feed.
Barley for human food is made into pearl barley by using abrasive disks to grind the hulls and bran off the kernels. Alter three successive "Pearlings" or grinding operations all the bull and most of the bran is removed. At this stage the remaining kernel part is known as pot barley. Two or three additional pearlings produce pearl barley, in which most of the embryo is removed. These later pearlings also produce barley flour. Pot and pearl barley are used in soups and dressings. The flour is used in baby foods and breakfast cereals, or mixed with wheat flour in baking.
Barley is also grown as a hay crop in some areas. For hay, only smooth-awned varieties or awnless are used. Winter barley also may be pastured moderately before the stems start to elongate. It furnishes nutritive pasturage, and grain yields are not seriously reduced.