Medicago(redirected from Bur Clover)
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(medic), a genus of plants of the family Leguminosae. They are mainly herbaceous perennials and annuals. The branching stems measure 70-90 cm tall (sometimes up to 150 cm) and form a bush. The leaves are trifoliate and oblong, with small stipules adnate to the bases of the petioles. The inflorescence is a raceme with 15 to 20 brightly colored flowers. The fruit is usually a sickle-shaped or spiral pod, with yellow or yellow-brown seeds that range in shape from oval to reniform. The root system, which is rodlike, thick, and branched, extends deep into the soil (5-10 m or greater). Outgrowths with nodule bacteria form on the slender roots. In perennial species, the upper part of the root (crown) has buds from which new stems annually sprout.
There are approximately 100 known species of Medicago in Europe, Asia, and Africa. In the USSR there are about 60 species, many of which are cultivated for hay and green feed. The plants are used for grazing and in mown form as fodder, hay, grass meal, and silage. All types of medic feeds are eaten by cattle; the green feed and grass meal is also eaten by poultry. The digestion coefficient of medic feeds is as high as 70-80 percent. One hundred kg of forage contain 21.7 feed units and 4.1 kg of digestible protein; 100 kg of hay contains 45.3 feed units and 10.3 kg of digestible protein. The hay contains much calcium and is rich in vitamins. Feed made from Medicago promotes rapid growth of animals and development of strong bone structure.
The Medicago are native to Iran and the foothills and mountains of Middle Asia and the Caucasus. The plants were first cultivated in Middle Asia approximately 5,000 years ago. About 2,000-2,500 years ago they were imported into ancient Greece, ancient Rome, and North Africa; subsequently their range of distribution extended throughout Europe, North and South America, and Australia. Medics are widely cultivated in the USA, Argentina, and India.
In the USSR, there is widespread cultivation of medic primarily in the southern regions. The plant’s cultivation is particularly significant as a rotational crop with cotton in regions with irrigation farming. When provided with enough moisture and warmth, medic yields large harvests of hay. On fertile soils in nonirrigated regions, two or three mowings are obtained (60-90 quintals of hay); on irrigated land, there are four to seven mowings (200-250 quintals of hay per hectare). Cultivated species include alfalfa (Medicago saliva, with violet or lilac flowers in an elongated raceme), M. falcata (with yellow flowers in a short raceme), their hybrid form (with mottled flowers ranging in color from blue to yellow), and M. coerulea (with small, violet flowers). Alfalfa and its hybrid form have the greatest economic significance. Alfalfa has been cultivated for a long time on irrigated lands in Middle Asia and Transcaucasia; hybrid alfalfa has been cultivated predominantly in the forest-steppe and steppe zones. In the USSR more than 200 selected and local varieties of Medicago have been developed and studied.
The Medicago are sown in field or pasture rotations, usually with such nurse crops as barley, spring wheat, and millet. On irrigated lands nurse crops often are not used. With small plantings, crop rotation is not used, and the plants are raised on reserve plots. When using a cropping system for soil conservation, the Medicago are sown on slopes, together with other grasses. Autumn tillage, typically used for spring cereal crops, is conducted. During the autumn plowing, organic and phosphorus-potassium mineral fertilizers are applied. In arid regions snow retention is practiced during the winter. In the spring the soil is harrowed and cultivated one or two times. The seeds are sown in rows spaced 8-15 cm apart. Seeds are sown 2-3 cm deep in clayey and loamy soils, and 3-4 cm deep on sandy loam. After the nurse crop is harvested, the Medicago are top-dressed with phosphorus-potassium fertilizers (they usually do not require nitrogen fertilizers). In subsequent years the land is harrowed or disked and topdressing is applied; in irrigated regions the land is watered at each mowing. In field crop rotations medic is usually used for two or three years; in forage rotations, for up to five years. When grown for hay, the plants are harvested sometime between budding and early flowering; measures are taken to preserve the leaflets—the most valuable parts of the plants for feed. When cultivated for seeds, the plants are harvested when 70-75 percent of the pods have turned brown.
The most harmful insect pests of Medicago include alfalfa plant bug, the alfalfa weevil (Phytonomus), the alfalfa snout beetle (Otiorrhynchus ligustici), the clover seed chalcid (Bruchophagus), the clover-flower midge, and the gall gnat Cecidomyia leguminicola. Control and preventive measures include placing new sowings no closer than 500 m from former plantings and dusting plantings with pesticides. Particularly harmful diseases include common leaf spot, yellow leaf blotch, black stem, and powdery mildew. Control measures are disinfection of seeds, proper maintenance, and spraying plantings with fungicides. Various parasitic dodders may cause considerable damage to medic harvests. Measures to control such damage include low cutting of infected plantings until the dodders flower, followed by destruction of the cut mass and deep plowing of the plot; herbicides can also be used.
REFERENCELiutserna. Moscow, 1964.
M. I. TARKOVSKII