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(sweet clover), a genus of biennial, less frequently annual, plants of the family Leguminosae (pea family); the genus comprises approximately 20 species, which are found in Europe, northern Asia, Middle Asia, northern Africa, North America, and Australia. Eleven species grow in the USSR (mainly in the Caucasus).
The stem of sweet clover is erect, branching, and usually smooth, up to 3 m high. The trifoliate leaves have leaflets with dentate edges. The inflorescence is an axillary raceme with a large number of small yellow or white flowers. The pods are rounded and contain one seed or, sometimes, two or three seeds. The root system is strong and penetrates up to 2 m into the ground. White sweet clover (M. alba ) and yellow sweet clover (M. officinalis ) are the most widely cultivated species. Sweet clover is resistant to cold weather and droughts. It grows best in soils rich in lime. Sweet clover desalinizes saline soils and enriches them with nitrogen. It is promising for the improving of alkaline soils of the forest steppe, steppe, and semidesert. Sweet clover is highly resistant to diseases and pests in comparison to other leguminous plants.
Sweet clover is a valuable forage plant rich in vitamins and mineral salts. It is just as valuable a forage as alfalfa and clover. The chemical composition of the white sweet clover when it begins to blossom is 73.2 percent water, 4.4 percent protein, 0.5 percent fat, 9.7 percent cellulose, 10.5 percent nitrogen-free extractive substances, and 1.7 percent ash. One hundred kilograms of herbage contain 17.5 fodder units and 3.3 kg of digestible protein; 100 kg of hay contain 44.0 fodder units and 11.6 kg of digestible protein. All types of livestock eat sweet clover. It is grown for pasture, silage, hay, and hay meal. It contains the aromatic substance coumarin, and for this reason animals eat it unwillingly in the first days of pasturing, but they soon grow accustomed to it. During the course of a summer sweet clover is eaten up by grazing livestock two or three times. In the first year sweet clover is harvested for silage a month before the frost, and in the second year, when it begins to flower. As a rule, it is ensiled together with a mixture of other cereal grain crops. Sweet clover is mowed for hay when it begins to flower. The yield of herbage from white sweet clover growing naturally varies from 20 to 50 centners per hectare, while the hay yield is 10-30 centners; in cultivated areas the yield of herbage is 200 or more centners per hectare, and the hay yield is 30-50 centners.
In the USSR sweet clover is grown in the Urals, Siberia, the Baltic republics, and the northern regions of the Kazakh SSR. The best crops to plant before planting sweet clover are row crops. Sweet clover is sown in spring, summer, or autumn. (It is best sown in early spring.) In crop rotation it is often sown as a cover crop for grain crops, and in the second year it is used to occupy fallow lands. The best means of sowing sweet clover are wide-row sowing with a plow and continuous row sowing. The standard quantity of seed is 20-25 kg per hectare. The seeds are sown at a depth of 2-3 cm. After sowing, the soil is packed to accelerate the appearance of seedlings, which usually appear on the fifth to tenth day. Sweet clover is grown to maturity for its seeds in most regions of the USSR. The seed yield is 6-15 centners per hectare. The most common varieties of white sweet clover are Kuuziku 1, Medet, Bashkir, Estonian, Kerch’ 1, and Alfalfa-type 9654; the most common varieties of yellow sweet clover include Al’sheevskii and Siberian. In the southern steppe regions sweet clover is sown to fasten the sands. It is a good honey-bearing plant: from 1 hectare of sweet clover bees can collect 200-600 kg of high-quality honey. Sweet clover is used in medicine to make medicinal plasters, in the tobacco industry to aromatize tobacco, and in the liqueur and vodka industry to make liqueurs.
REFERENCESuvorov, V. V. Donnik. Moscow-Leningrad, 1962.
V. V. SUVOROV