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 absence of added Zn on a Wakanui silt loam soil at Lincoln, Canterbury, New Zealand. Pasture yield and Zn concentrations were monitored at approximately monthly intervals for a period of one year. There were very small effects only on pasture yield as a result of the phosphate and lime applications. Phosphate applications showed some indications of producing small increases in herbage Zn concentrations and uptake, possibly as a result of Zn impurities in the superphosphate fertiliser used. In contrast, application of lime produced much more consistent decreases in herbage Zn concentrations and uptake. EDTA-extractable soil Zn concentrations were also significantly decreased by lime application. The results of this study indicate that on soils where Zn is not already marginal or limiting pasture growth, application of superphosphate or lime is unlikely to induce Zn deficiency.