Source: Magness et al. 1971
Oats are the third most important grain crop in the United States. They are grown to some extent in every continental state. Average acreage planted to oats, 1961-65, was 27,902,000. Production during that period averaged 953,426,000 bushels. However, the importance of oats as a farm crop is decreasing. Acreage planted during the 3-year period 1954-56 averaged near 46 million. This declined to an average of about 22.6 million for the period 1965-67.
Most oats -are used for livestock feed. Less than 5 percent of the total production in this country is used as food - mainly in the form of breakfast food and oat flour. Some acreage is also used for pasture, hay, and silage.
Oats are believed to be mainly Asiatic in origin. Different kinds of oats probably came from different parts of that continent or Europe. As a cultivated crop oats appear to be substantially later in origin than wheat. Early use of oats appears to have been medicinal. Not until about the beginning of the Christian era are references to oats as a cultivated crop found in literature. Cultivation of oats was extensive in Europe prior to the discovery of America, and the earliest settlers brought seed to the new world. They are now an important crop in all temperate zone countries.
The oat plant, like wheat, is an annual grass with kinds and varieties adapted either to fall Planting and midsummer harvest or spring planting and late summer harvest. In general, overwintering kinds are grown where winter climates are mild - as throughout the Cotton Belt and in the western portions of the Pacific States. Spring seeding is generally practiced in other areas.
The early growth of the plant consists of leaves and a greatly shortened stem, giving a rosette type of plant. The early habit may be prostrate, semi-prostrate or upright. Tiller or branch buds under the soil surface grow into additional "branch plants" or tillers. The number of tillers formed depends on density of seeding, variety and growing conditions. In general, varieties adapted for spring Planting form relatively few tillers, while up to 30 tillers may form on fall varieties under favorabfe conditions. However, all may not produce panicles.
With fall seeding, plants generally remain in the rosette stage until spring. With spring seeding this stage is relatively short. The main stem and tiller stems then push upward reaching to 2 or more feet, again depending on variety and growing condition. These stems terminate in a large, generally loose panicle on which the flowers and seeds or kernels are borne.
The panicle consists of a central stem or rachis, side or rachis branches which rise in whorls at the nodes, and spikelets in which the flowers and seeds are borne. Each main and lateral stem or rachis terminates in a spikelet, but spikelets also are produced at the nodes of the branch stems. The panicles may be spreading in equilateral fashion, or one-sided. From 20 up to 150 spikelets may be produced on one panicle' Spikelets often droop or hang downward but may be upright. The spikelets are subtended by two loose membranous glumes, which generally are longer than the spikelet and largely cover it during flower and seed development. These are removed in threshing. In hulled varieties the spikelets usually contain three florets or flowers, one of which is rudimentary and nonfunctional. Generally two kernels or seeds are produced per spikelet, but sometimes only one develops. In so-called naked oats 3 to 7 flowers may be produced per spikelet.
The oat flower consists of the palea and lemma which enclose the sex organs - the stamens and single ovary. The palea may be awned or awnless and it and the lemma enclose and adhere to the developing ovary or seed, except in so-called hull-less oats. Thus they are a part of the seed following threshing in most kinds. The oat kernel, also termed caryopsis or groat, is the part remaining after removal of the palea and lemma. It is elongated - spindle in shape, up to about 0.5 inch in length and 0.125 inch or less in width. It is generally thinly covered with fine, silky hairs and includes the seedcoat layers of cells, the starchy endosperm, and the embryo.
When used for feed the whole oat as it comes from the thresher, which include the palea and lemma but not the glumes, is fed either whole or after grinding. In products used for food the lemma and palea are removed.
Large Naked Oat (Hull-less Oat). A. nuda L. In this species the kernel or caryopsis is loose within the palea as in the major kinds of wheat. The origin of the species appears to have been Central and Eastern Asia. Several varieties have been introduced or have been developed in this country, but they are grown only to a very limited extent.
Small Naked Oat. A. nudibrevis Vav. This oat differs from the large in that panicles are small, stems are smaller and more slender, the kernel is much smaller, and the chromosome number differs so this species does not hybridize with most other oats. This oat is not grown commercially in the United States.
Wild Red Oat. A. steriles L. This species is believed to be that from which cultivated red oats developed. It is characterized by large, hairy lemmas, which have strong twisted awns and adhere tightly to the kernel. Three botanical varieties are recognized. This species has become naturalized in some areas in this country but is not in cultivation.
Red Oat. A. byzantina C. Koch. A number of important cultivated varieties of both winter and spring habit are included in this species. In red oats the two flowers in the spikelet adhere tightly to each other and separate by fracture of the rachilla or stem at the base. The lemmas adhere to the kernel and have weak, non-twisted awns. Stems are usually slender and rather stiff and reddish in color. Panicles are small, narrow and erect with relatively few spikelets. Glumes are somewhat longer than in common oats. Red oat varieties are the kinds generally grown in the southern half of the United States. Stanton (loc. cit.) describes 50 varieties of red oats, many of which are still cultivated.
Desert Oat. A. wiestii Steud. This species, introduced into this country for study, appears native to the Eastern Mediterranean Area. Stems'are slender, medium high, and stiff. It differs from the wild oat, A. fatua L., in having shorter, more slender lemmas that terminate in two bristle-like glume points. Juvenile growth is upright. The species is not in cultivation.
Slender Oat. A. barbata Pott ex Link. This species has small, weak stems, resulting in a decumbent growth habit. Panicles are equilateral, rather large, and drooping. Seeds fall to the ground at maturity. The species is now widely distributed throughout the world. The origin is believed to be Europe. The species is not grown as a grain crop but has become naturalized widely. In California it is a reseeding range grass.
Sand Oat. A. strigosa Schreb. In this species the lemmas are lance-like, extending to two distinct points. The plant has small, erect stems. Panicles are near equilateral. The species is widely distributed in Europe and bas become naturalized in California. It is not grown as a grain crop.
Abyssinian Oat. A. abyssinica Hochst. ex Rich. This oat is similar in habit to the desert oat, A. wiestii, but differs in chromosome number. Stems are erect, rather small and fairly stiff. Panicles are equilateral, medium sized, very drooping. This species is grown to some extent in Abyssinia but not in the United States.
Wild Oat. A. fatua L. This species is now widely distributed throughout temperate regions and is a troublesome weed in Northern States and in Canada. The plant resembles the common oat, A. sativa L., but is of greater vigor. Panicles are very large and drooping. The spikelets carry long twisted awns and separate from their pedicels by abscission, dropping when ripe. Thus the plant is self seeding. The species is of some value for hay or pasturage but is not grown for grain.
Common Oat (Tree Oat). A. sativa L. This is the most important of the cultivated oats. Stanton (loc. cit.) in 1955 listed 146 varieties of common oats, most of which were grown commercially in some part of the United States although production of many of them was very limited. Numerous new varieties have been released since that time, while a good many he listed are no longer grown. Included are many varieties of winter and of spring habit. The plants of different varieties differ in vigor and height. All are charcterized by a panicle that is roughly pyramidal in shape with equilateral branches that spread outward. Many varieties are awnless, and in awned varieties, usually only the first flower is awned. Lemmas and paleas adhere to the kernel and may be white, gray, yellow or black in color. Shape and size of grains also are highly variable. Basal hairs are few, under the lemma. The species can be distinguished from red oat, A. byzantina, by the fact that spikelets of common oats separate from the pedicel by fracture leaving no basal scar, while in red oats and some other species separation is by abscission - leaving a definite scar.
Side Oats (Common Side Oats). A. sativa L., subsp. orientalis Schreb. This sub-species is of much less economic importance in the United States than the common or tree oat since varieties of it are generally oat varieties are of spring type. The principal of this sub-species is the panicle which is of the stem axis. Side branches on the panicle stem, but branches definitely turn to one side also tend to turn upward more than in common oats. Like in the common oat, lemmas and paleas adhere to the kernel and may be black, gray, yellow or white in color. Stanton (loc. cit.) lists 18 varieties of side oats, none of which is grown extensively.
Oats are a nutritious feed for all classes of livestock. The hull, composed of lemma and palea, comprises on the average about 23 percent of the weight of the whole grain. Oats are high in mineral content and also in several vitamins. Formerly largely fed to horses, oats are now used as feed for dairy cattle and poultry as well. Oat hulls from milling are used in poultry mash. For food use, the groat or inner kernel is rolled into flakes and used as oat meal in breakfast foods and baking. Oat flour contains an antioxidant which is used to preserve quality by delaying rancidity. Oat flour may also be mixed with wheat flour for multigrain baked products.
Oat straw is more nutritious and palatable than wheat straw and is important as a supplementary feed on many farms. Fall sown oats fumish nutritious and palatable winter grazing in areas having mild winters.