A comparison of methods to raise zinc concentration of apple leaves.

Little residual increase in leaf Zn concentration was measured after spray application of ZnSO4 at silver tip or postharvest or after sprays of Zn50 or chelated Zn at tight cluster in a series of multi-year field experiments in three Delicious apple (Malus domestica Borkh.) orchards. In contrast, Zn applied to the soil surface or within peat plugs inserted in the soil increased leaf Zn although sometimes to toxic concentrations in a different orchard comparing foliar- and soil-applied Zn.Key words: Apple, Zn deficiency, leaf Zn