The effect of applying cobalt sulphate to soil on the cobalt content of herbage

Abstract. Two hill pastures in north Dyfed, Wales, were each treated at reseeding in 1971 with 2.25, 4.5 and 9.0 kg ha^?1 cobalt sulphate. Herbage samples for analysis of Co content were taken in summer at each site from 1971 to 1976 and also at site 1 from 1977 to 1983. Acetic acid extractable Co was measured in soil samples taken each winter for the same period at both sites. At site 1, on a peat, the treatments continued to give worthwhile increases in herbage and soil Co after 13 years. At site 2, on a mineral soil, the residual effects were small and lasted no more than four years. It is suggested that me lower response and residual value at site 2 is due to higher levels of exchangeable and easily reducible manganese.