Effect of cobalt application on the cobalt status of pastures 3. Comparison of chelate and sulphate as cobalt sources for topdressing deficient pastures

Abstract

Cobalt chelate (Co EDTA) and cobalt sulphate (CoSO₄), applied in liquid and solid forms, were compared as sources of cobalt (Co) for topdressing pasture at a site located within a paddock where grazing lambs responded to vitamin B₁₂ injection. The two materials were equally effective in increasing pasture Co concentration but the effects from both lasted only about 100 days. Rate of application of both materials affected the maximum pasture Co concentration obtained but did not greatly influence the duration of the response. There was a small advantage at first from the liquid form but it did not persist. It is concluded that Co EDTA is no better than CoSO₄ and because of its high relative cost it cannot be recommended for topdressing pastures. There is a need for a slow-release source of Co that will maintain pasture Co concentration at an adequate level for lambs for much of the grazing season but until such material becomes available a recommendation on a more effective use of CoSO₄ is made.

Keywords:

• pasture cobalt
• cobalt sulphate
• cobalt EDTA
• fertiliser application