EFFECTS OF PHOSPHATE AND LIME APPLICATIONS ON PASTURE ZINC STATUS

The effects of phosphate and lime applications on pasture herbage zinc (Zn) concentrations and uptake were studied in the presence and absen ce of added Zn on a Wakanui silt loam soil at Lincoln, Canterbury, New Zealand. Pasture yield and Zn concentrations were monitored at approx imately monthly intervals for a period of one year. There were very sm all effects only on pasture yield as a result of the phosphate and lim e applications. Phosphate applications showed some indications of prod ucing small increases in herbage Zn concentrations and uptake, possibl y as a result of Zn impurities in the superphosphate fertiliser used. In contrast, application of lime produced much more consistent decreas es in herbage Zn concentrations and uptake. EDTA-extractable soil Zn c oncentrations were also significantly decreased by lime application. T he results of this study indicate that on soils where Zn is not alread y marginal or limiting pasture growth, application of superphosphate o r lime is unlikely to induce Zn deficiency.