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

Abstract

<jats:p>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</jats:p>

The effectiveness of autumn spray applications of cobalt sulphate, copper chelate and copper sulphate on Southland pastures

“…While this could account for these higher concentrations with lower application rates, there was sufficient rainfall in the first 3 weeks of the trial to wash the chemicals off the leaves, so that uptake through the roots could occur. The Co results measured here further confirm the findings of earlier workers (Morton & Smith 2000;Pringle et al 2000) where spray applications result in significant pasture Co increases, but also indicate that these increases in pasture Co levels can be extended into the autumn with a second application for those few occasions where this may be necessary. This is more likely to occur on soils with low Co and no history of Co application (Sherrell 1990a), than on soils with a history of Co application due mainly to the reserves of Co in the soil maintaining higher Co concentrations for longer (Sherrell et al 1990).…”

“…The 6 week duration of the effect of the Co liquid application was similar to that found previously in Southland (Morton & Smith 2000;Metherell 1989), while for the CuSO 4 it was longer (Morton & Smith 2000). However in this experiment the maximums reached in the first 5 days following application for both Co and Cu were somewhat higher than those found by Morton & Smith (2000), but for the Co were similar to that of Metherell (1989). Both these previous studies were conducted with late spring/summer applications.…”

“…While effects of autumn applications as used here follow similar patterns to these earlier ones, the duration of the effect was longer, perhaps due to the slowing of pasture growth in autumn and hence a greater concentration of Co or Cu within the plant. This occurred despite the application rates of the Cu used in this study being lower than those of Morton & Smith (2000). It is possible that the initial higher concentrations are due to the adherence of the spray to the surface of the plant rather than movement into the herbage.…”

“…Grace (2002) has suggested that applying 12 kg Cu SO 4 /ha in late-March was effective in maintaining an adequate Cu status of grazing deer for up to at least 10 months, provided herbage levels are increased to at least 45 mg Cu/kg dry matter (DM) for at least 8-12 weeks. However Morton & Smith (2000) found a short duration of effect of high rates of CuSO 4 from summer application, which suggests that CuSO 4 should be applied at a time when the animal can build up stores of Cu in the liver before a critical period. They also found that immediately following application, pasture levels of Cu were elevated sufficiently to cause some animal health concerns.…”

“…However the magnitude of the pasture response is dependent on soil status and pasture composition, with clover known to have a higher content of Cu and Co than grasses (Grace 1992;Sherrell & Rawnsley 1982;Sherrell 1990b). Earlier work (Pringle et al 2000;Morton & Smith 2000) has suggested that applications of liquid CoSO 4 resulted in higher plant concentrations than applications of the solid form when applied in summer. Sherrell (1990b) also found that liquid Co applications resulted in higher initial plant concentrations, but this difference was relatively short lived.…”