TRACE ELEMENTS IN ANIMALS 149 



Mitchell and Stewart in which a field with a low cobalt content 

 of the soil (about 1-8 p.p.m.) was divided into two halves, one 

 of which was manured with 2 lb. cobalt chloride + 3 cwt. super- 

 phosphate per acre, the other with 3 cwt. superphosphate only. 

 Four to five weeks after this manuring fifteen lambs were 

 allowed to run on each half of the field, the two groups being of 

 equal value at the start. After 6 weeks the difference in the 

 appearance of the lambs of the two groups was striking, all 

 those on the half of the field with added cobalt being in fine 

 condition, whereas eight of the fifteen lambs on the other half 

 of the field showed severe pining while the remaining seven 

 animals were in poor condition. 



While the effectiveness of cobalt manuring in increasing the 

 cobalt content of the herbage of ' pining ' lands can be regarded 

 as established, work by Mitchell, Scott, Stewart and Stewart 

 (1941) indicates that such manuring requires care. They find by 

 spectrographic analysis that the herbage growing on cobalt - 

 treated soil may take up an abnormally large amount of molyb- 

 denum. Where the herbage without cobalt treatment already 

 had a fairly high molybdenum content, this latter may be so 

 increased by cobalt manuring that it approaches the molyb- 

 denum content of the herbage of teart land, so that danger of 

 scouring may ensue. Analyses of the herbage from two soils, one 

 with a low, the other with a high molybdenum content, cut 15 

 months after various degrees of cobalt manuring, are shown in 

 Table XX. Since Lewis has shown that molybdenum uptake is 

 reduced by the use of acidic nitrogenous fertilizers (see p. 135), 

 and since teartness occurs on neutral and alkaline soils, it would 

 seem inadvisable to apply cobalt in the form of a cobalt-rich lime 

 or in conjunction with fertilizers having an alkaline reaction. 



Table XX. Cobalt and molybdenum contents of herbage from 

 soils treated with cobalt chloride. (Data from Mitchell, 

 Scott, Stewart and Stewart) 



