No data as yet) MOLYBDENUM IN SWEETCLOVER GROWING ON MINE SPOILS by James A. Erdman and Richard J. Ebens The total molybdenum in soil where cattle have been known to be affected is not high, ranging from 1.5-10 ppm in the study described by Barshad (1948). In alkaline soils, however, a large percentage of this element may be soluble in water. Barshad (1948) stated, "Growing plants, particularly legumes, are able to absorb amounts of molybdenum harmful to cattle from soils that contain as little as 1.5-5.0 ppm total Mo." The proportion of copper to molybdenum in the forage is considered to be more critical than the total amount of molybdenum in either the soil or plants. Copper-to-molybdenum ratios of about 5:1 or less in winter herbage from the British Isles have caused swayback in lambs and hypocuprosis in cattle (Alloway, 1973). A copper-to-molybdenum ratio of about 7:1 is apparently optimum for cattle, according to the University of Missouri's veterinary toxicologist, A. A. Case (written communication, 1974). Similar ratios were cited by Alloway (1973) for control farms. Clearly, where legumes are a substantial part of the pasturage in molybdic and alkaline soils, certain types of livestock can be severely affected. Concern over the possible incidence of molybdenum-induced imbalances in animals grazing in regions associated with coal utilization is not new, although more information seems to be available on the effects of fly ash on the content of forage than on the effects of coalmine spoils (Furr and others, 1975; Gutenmann and others, 1976). The only documented case of molybdenosis in cattle from the western coal regions is the report by Christianson and Jacobson (undated), which describes an area where uraniferous lignite was burned in rotary kilns in order to concentrate the uranium, and the molybdenum in the ash contaminated the surrounding pasturage. The most recent interest in molybdenum-related nutritional problems was expressed by Martens and Beahm (1976) who cautioned, "Molybdenum availability of some fly ashes is sufficiently high that levels in plants grown on fly-ash soil mixtures can be hazardous to grazing animals." There are reasons for our interest in sweetclover and its molybdenumaccumulating potential other than its abundance and widespread occurrence on the coalmine spoils that we studied. Legumes are recommended in seed mixes for reclamation because of their nitrogen-fixing capabilities, and sweetclover, in particular, is considered one of the more suitable plant species for spoil bank stabilization. Finally, the forage value of sweetclover rates very high. According to A. A. Case (written communication, 1975), "Sweetclover is a wholesome and very nutritious legume, ranking along with other clovers in its nutritional value, perhaps just less than alfalfa, which is considered the 'queen' of legumes for forages and hay purposes." Although under most circumstances, sweetclover is not considered a toxic plant, Case does warn of changes that can occur where it grows in altered environments. I/...