Pasture uptake from solid and liquid applications of cobalt and copper sulphate

Abstract

Uptake of cobalt (Co) and copper (Cu) by ryegrass- white clover based pasture was measured from December 1999 to March 2000 at Woodlands Research Station in Southland. Treatments were control, cobalt sulphate (CoSO4) at 120 and 240 g/ha initially and 60 g/ha monthly, and copper sulphate (CuSO4) at 5 and 10 kg/ha initially and 1.25 kg/ha monthly, applied in either solid or liquid forms. At 120 g CoSO4/ha applied as solid and liquid, pasture Co content was significantly (P<0.05) elevated above control for up to 3 weeks after application. CoSO4 applied initially at 240 g/ha in both forms significantly increased pasture Co above control for 6-7 weeks after application. For the December monthly application, neither solid or liquid application of 60 g CoSO4/ ha significantly increased pasture Co from 2 weeks after application. Later applications resulted in both forms of CoSO4 significantly increasing pasture Co above control for up to 3 weeks after application. Pasture Co was significantly higher from liquid compared to solid application in February and March. When applied in one application, 5 kg solid CuSO4/ha significantly increased pasture copper (Cu) content above control for 3 weeks, 5 kg liquid CuSO4/ha had an effect for 4 weeks, 10 kg solid CuSO4/ha for 5 weeks, and 10 kg liquid CuSO4/ha for 13 weeks. Monthly applications of 1.25 kg CuSO4/ha significantly increased pasture Cu above control for 1-2 weeks after application in all months. There was a significant increase in pasture Cu from liquid compared with solid application in February and March. The short duration of effect of the high rates of CoSO4 and CuSO4 suggest that, if required, they should be applied at a time when the animal can build up stores of Co and Cu in the liver before a critical period. In summer/autumn, when rainfall is lower, CoSO4 and CuSO4 if required, should be applied as liquid, 1 week before the pasture is grazed. These recommendations assume that the increase in pasture uptake of Co and Cu would result in greater Co and Cu availability to the animal. Keywords: CoSO4, CuSO4, pasture, Co content, Cu content