Effectiveness of zinc sulfate and zinc chelate as foliar sprays in alleviating zinc deficiency of wheat grown on zinc-deficient soils in Western Australia

The relative effectiveness of zinc chelate (Zn-EDTA, 15% Zn) and zinc sulfate (23% Zn) applied as f o l k sprays for alleviating zinc deficiency of wheat was assessed. The experiments were conducted at 3 sites in 3 different years, in the Newdegate district about 350 km south-east of Perth, Western Australia. Each source was sprayed at 6 rates of Zn, to define the relationship between grain yield and the amount of foliar Zn applied for wheat grown on Zn-deficient soils where no Zn had been previously applied. The levels of Zn sprayed were 0, 25, 50, 100,200 and 400 g/ha (experiment 1); and 0, 28, 56, 112, 225 and 450 g/ha (experiments 2 and 3). Foliar-applied zinc chelate was 1.4-1.7 times more effective than zinc sulfate applied at the GS 14 growth stage. However, the sprays were equally effective when applied at the GS 23-24 growth stage. Zinc sulfate banded with the seed at sowing produced the highest grain yields.