Oats (Avēna), a genus of edible grasses, containing many species, among which are some valuable for the grain which they produce, and some useful for hay. The Linnean genus Avena, as now restricted, has the spikelets in loose panicles, the glumes as long as the florets, and containing two or more florets; the paleæ firm, and almost cartilaginous, the outer palea of each floret, or of one or more of the florets, bearing on the back a knee-jointed awn, which is twisted at the base. The awn, however, tends to disappear, and often wholly disappears in cultivation. Those species which are cultivated as corn-plants have comparatively large spikelets and seeds, the spikelets—at least after flowering—pendulous. The native country of the cultivated oats is unknown, although most probably it is central Asia. There is no reference, however, to the oat in the Old Testament; and although it was known to the Greeks, who called it Bromos, and to the Romans, it is probable that they derived their knowledge of it from the Celts, Germans, and other northern nations. It is a grain better suited to moist than to dry, and to cold than to warm climates, although it does not extend so far north as the coarse kinds of barley. The grain is either used in the form of groats or made into meal. Oatmeal cakes and porridge form great part of the food of the peasantry of Scotland and of some other countries. Oatmeal is now more largely used as food amongst the wealthier classes than formerly, but with the working-classes, alike in town and country, it is losing favour. No other grain is so much esteemed for feeding horses. Besides a large quantity of starch—about 65 per cent.—and some sugar, gum, and oil, the grain of oats contains almost 20 per cent. of nitrogenous principles, or protein compounds, of which about 16 or 17 parts are Avenin, a substance very similar to Casein (q.v.), and two or three parts gluten, the remainder albumen. The husk of oats is also nutritious, and is mixed with other food for horses, oxen, and sheep. From the starchy particles adhering to the husk or seeds after the separation of the grain, a light dish, long popular in Scotland under the name of sowans, is made by means of boiling water. The grain is sometimes mixed with barley for distillation. The Russian beverage called kvass is made from oats. The straw of oats is very useful as fodder, bringing, for that purpose, a higher price than any other kind of straw.
The varieties of oats in cultivation are very numerous, and some highly esteemed varieties are of recent and well-known origin. It is doubtful if they really belong to more than one species; but the following are very generally distinguished as species: (1) Common Oat (A. sativa), having a very loose panicle, which spreads on all sides, and two or three fertile florets in each spikelet, the paleæ quite smooth, not more than one floret awned; (2) Tartarian Oat (A. orientalis), also called Hungarian Oat and Siberian Oat, distinguished chiefly by having the panicle much more contracted, and all turned to one side; (3) Naked Oat (A. nuda), differing from the Tartarian oat chiefly in having the paleæ very slightly adherent to the seeds, which, therefore, fall readily out of them, whilst in the other kinds they adhere closely; (4) Chinese Oat (A. chinensis), which agrees with the last in the characters of the paleæ and seeds, but is more like the common oat in its panicle, and has more numerous florets, 4–8, in the spikelet; (5) Short Oat (A. brevis), which has a close panicle turned to one side, the spikelets containing only one or two florets, each floret awned, the grains short. Almost all the varieties of oat in cultivation belong to the first and second of these species. The naked oat is cultivated in Austria, but is not much esteemed. The Chinese oat, said to have been brought by the Russians from the north of China, is prolific, but the grain is easily shaken out by winds. The short oat is cultivated as a grain-crop on poor soils at high elevations in the mountainous parts of France and Spain, ripening where other kinds do not; it is also cultivated in some parts of Europe as a forage plant.—Besides these, there is another kind of oat, the Bristle-pointed Oat (A. strigosa), regarded by some botanists as belonging even to a distinct genus, Danthonia, because the lower palea is much prolonged, and instead of merely being bifid at the point, as in the other oats, is divided into two long teeth, extending into bristles. The panicle is inclined to one side, very little branched; the florets, two or three in a spikelet, all awned, the grain rather small. This plant is common in cornfields, is cultivated in many countries, but chiefly on poor soils, and was at one time much cultivated in Scotland, but is now scarcely to be seen as a crop.—Not unlike this, but with the panicle spreading equally on all sides, the outer paleæ merely bifid, and long hairs at the base of the glumes, is the Wild Oat (A. fatua), which is generally regarded by farmers as a weed to be extirpated, springing up so abundantly in some districts as to choke crops of better grain. Its awns have much of the hygrometrical property which gains for A. sterilis, a species found in the south of Europe, the name of the Animal Oat, because the seeds when ripe and fallen on the ground resemble insects, and move about in an extraordinary manner through the twisting and untwisting of the awns. The seed of the Wild Oat has been sometimes used instead of an artificial fly for catching trout.—Amongst the species of oat useful not for their grain but for fodder are the Downy Oat-grass (A. pubescens) and Yellow Oat-grass (A. flavescens), both referred by some botanists to the genus Trisetum—the short awn being like a middle tooth in the bifid palea—and both natives of Britain, the former growing on light ground and dry hills, especially where the soil is calcareous, the latter on light meadow-lands.
Far more ground is occupied with oats in Scotland than with any other grain. In all the higher districts it is almost the only kind of grain which is cultivated. Throughout Scotland it is the crop that is chiefly sown after land has been in pasture for one or more years. The seed is generally sown broadcast by hand over the ploughed land, which is afterwards well harrowed and rolled. Sowing by broadcast or drill machines is now largely practised, and in this case the harrowing is done before the seed is sown. On soils that are infested with annual weeds, such as charlock, it is common to drill the seed, which permits the land to be hand-hoed and thoroughly cleaned. Oats thrive best upon deep and good soils, especially if enriched by decayed vegetable matter. They yield but poorly on thin sandy soils, where they suffer sooner from drought than barley, rye, or wheat. The produce per acre varies from 20 to over 80 bushels, weighing from 36 lb. to 48 lb. per bushel. Common yields run from 32 to 56 bushels; average weight from 40 lb. to 44 lb. per bushel. A crop of 45 bushels per acre will absorb and carry away about 55 lb. of nitrogen, 46 lb. of potash, and 19½ lb. of phosphoric acid per acre. Few soils, in ordinary tillage, require the direct application of potash for oats. Very light soils are most likely to need it. Superphosphate of lime and nitrate of soda are suitable manures for oats; common quantities being from 1 to 2 cwt. of the former and from ½ to 1 cwt. per acre of the latter, applied as a top-dressing. The Potato Oat is a variety generally cultivated in the best soils and climates. It is an early and productive variety. The Hopetoun Oat is also much sown in the earliest districts. The Sandy Oat is still more largely sown, more particularly when the climate is inferior and wet. It is not liable to be lodged with rains, and the straw is of fine quality for fodder. All these are varieties of the Common Oat. The White and Black Tartarian are much cultivated in some districts. They are very productive, and well suited for feeding horses, cattle, and sheep. On the continent of Europe this grain is seldom seen of quality equal to what is produced in Scotland; even in most parts of England the climate is less suitable to it, and it is less plump and rich.