| Popis: |
The current requirement of copper for optimum growth of pasture, and production and health of sheep on the sandy soils of the upper south-east regions of South Australia was investigated in three consecutive years at three sites each of which had previously been treated once with copper. In a glasshouse study copper applied to virgin soil, obtained from areas next to the sites, increased the growth of subterranean clover. Dry matter production of herbage grown in enclosures on developed soil that had received copper 14-23 years earlier did not respond to additional applications of copper fertilizer. The concentration of copper in grazed herbage, where no additional copper was applied, was usually greater than 6 mg/kg dry matter. Sheep liveweight and greasy wool production were not increased by subcutaneous injections of copper at any site and the concentrations of copper in blood plasma and liver of untreated sheep were consistently greater than those associated with copper inadequacy in sheep. Also the copper treatments did not affect the fibre diameter or copper concentrations of the fleeces, and steely wool was not observed. We concluded that a copper dressing of 2 kg/ha to these soils provides adequate copper for pasture and sheep production for at least 23 years and that repeated dressings are unwarranted. |
