Summary. This paper briefly describes common mineral disorders affecting livestock at pasture in Australia, their mineral requirements, factors affecting these requirements and laboratory methods of assessing the mineral status of the animal. The benefits and limitations of mineral analyses of soil and pasture samples for the purposes of identifying and preventing mineral disorders of the grazing animal are discussed. Mineral analyses of pasture are of particular value in the identification of the causes of copper and magnesium deficiency and of acute calcium deficiency in livestock. Selective grazing, adventitious ingestion of soil and variability in the mineral reserves of the animal, however, limit the usefulness of pasture analyses to identify a mineral disorder in the grazing animal.

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Summary. The effectiveness of foliar applications of zinc sulfate to decrease cadmium (Cd) concentration in wheat grain was assessed at 3 field sites in South Australia—Tumby Bay, Cummins and Keppoch. Foliar zinc (Zn) treatments were found to significantly (P<0.001) decrease Cd concentrations in grain at only 1 site, Tumby Bay. At this site the highest foliar Zn treatment (0.67 kg Zn/ha), which consisted of 2 applications of 0.33 kg Zn/ha applied early and late, decreased the mean Cd concentration in grain from 0.025 mg/kg for the nil treatment to 0.017 mg/kg. Timing of application of foliar Zn had no significant effect on Cd concentration in wheat grain. The effect of soil applications of zinc sulfate on grain Cd concentration was assessed at Tumby Bay only. There was no significant difference in grain Cd concentration between the soil Zn treatments. The results from this study suggested that the current recommended rates of foliar applications of Zn to ameliorate Zn deficiency are not high enough to decrease Cd concentration in wheat grain. This is most likely due to the recommended foliar rate of 0.33 kg Zn/ha not providing excess Zn to the plant such that there is enough Zn to be translocated to the root, which is the site of Cd uptake by the plant. The results suggest that the benefits of foliar Zn to minimise Cd concentration in grain are variable or that the rates used to correct Zn deficiency under field conditions are too low to decrease Cd uptake. Further work is required to distinguish between the 2 possibilities.

In the three experiments reported, the selenium content of pastures was shown to be substantially affected by applications of sulphate fertilizer. Where pasture yields responded to sulphur topdressing, selenium levels in the legumes present were reduced by as much as 50 per cent due largely to yield dilution effects. On a second site, where pasture responses to sulphur were not obtained, selenium levels were also depressed, in this case indicating the existence of an antagonism between sulphur and selenium. A subsequent nutrient solution culture experiment indicated that an antagonism existed between sulphate and both selenate and selenite forms, with the effects being much stronger in the case of the selenate. The implications in animal production of the effects of applied sulphur on pasture selenium levels and of the associated increases in pasture sulphur levels are discussed.

The efficacy of foliar applied manganese (Mn) in preventing Mn deficiency in safflower (Carthamus tinctorius L. cv. Gila) was assessed in a black clay soil in the South-East of South Australia. The application of Mn significantly increased seed yield? from 1040 to 1450 kg/ha, through an increase in the number of seeds per plant. Maximum yields were attained by a foliar application of 500 g/ha of Mn. In the youngest open leaf the critical nutrient range (CNR) for Mn was 9-13 8g/g, while for the upper primary stem a CNR of 2-3 8g/g was determined. The CNR for Mn in the seed was found to be 5-6 8g/g.