The residual effect of pasture cobalt applications on some soils in South East Scotland

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Abstract
There are extensive areas in Scotland and other parts of Britain where, because of low soil cobalt status, the cobalt concentration of pasture herbage is below the 0–1 /fg/g D.M. regarded as the requirement for grazing ruminants (Agricultural Research Council, 1965). A common method of overcoming the effects of cobalt deficiency in livestock occurring within these areas is to apply cobalt sulphate to the pasture. Following work carried out by Stewart, Mitchell & Stewart (1941, 1942) and Stewart etal.(1946) the standard recommended application of cobalt sulphate for pasture has remained at 2 kg/ha for many years, an application generally expected to last for 3–5 years. However, in South East Scotland there are doubts about the adequacy of such treatment which has led to a reappraisal. Significant increases in uptake of cobalt by herbage following applications to land at this rate are not always observed and sometimes there is no appreciable increase in ‘available’ soil cobalt as determined by acetic acid extraction.