EFFECTIVENESS OF SOME COPPER-COMPOUNDS APPLIED AS FOLIAR SPRAYS IN ALLEVIATING COPPER DEFICIENCY OF WHEAT GROWN ON COPPER-DEFICIENT SOILS OF WESTERN AUSTRALIA

The effectiveness of copper oxychloride (Cu2Cl(OH)3, 52% Cu) and chelated Cu (Cu-EDTA, 15% Cu) were compared with the effectiveness of copper sulphate (CuSO4, 25% Cu) as foliar sprays for alleviating Cu deficiency and obtaining maximum grain yields of wheat (1.93-2.5 t/ha). The experiments were conducted over 4 years at 4 sites in the Lake Grace and Newdegate districts, about 300-350 km south-east of Perth, Western Australia. Each source was sprayed at 6 or 7 rates of Cu to define the relationship between grain yield and the amount of foliar Cu applied for wheat grown on soils where Cu had not been previously applied. The levels of Cu sprayed in experiment 1 were 0, 21, 63, 125, 250, and 375 g/ha, and for experiments 2, 3 and 4, the levels of Cu were 0, 25, 50, 100, 200, 400 and 800 g/ha. The relative effectiveness of foliar-applied chelated Cu and Cu2Cl(OH)3, compared with CuSO4, was 1.72-2.24 and 0.47-0.63, respectively. Although the relative effectiveness of each product was different, similar quantities of each were required to achieve maximum wheat grain yield because of the difference in the Cu contents of each source of Cu. The amounts of Cu product sprayed for maximum grain of wheat varied within the ranges 0.9-1.8 kg/ha, 0.8-1.2 kg/ha and 0.8-1.8 kg/ha for CuSO4, chelated Cu and Cu2Cl(OH)3, respectively.