Effectiveness of soil dressings and foliar sprays of copper sulphate in correcting copper deficiency of wheat (Triticum aestivum) in Queensland

Abstract

One field and two glasshouse trials were conducted to test the effectiveness of soil and foliar applications of copper sulphate in correcting copper deficiency of wheat on a severely deficient, nearneutral clay soil in the Western Downs region of Queensland. In the field, when wheat was stressed for water from late tillering (Feekes stage 5) to anthesis (Feekes stage 11) , soil dressings of 2.5-10.0 kg CuSO4.5H2O ha-1 increased early vegetative growth but foliar symptoms of copper deficiency reappeared during stem elongation, and grain yields were negligible at all rates. A single foliar spray of 2% CuSO4.5H2O applied at mid-tillering (Feekes stage 3) also did not correct the deficiency completely: foliar symptoms reappeared and grain yield was low (141 kg ha-1). A double spray treatment, the first applied at mid-tillering and the second just before booting (Feekes stage 10), was more effective and resulted in a grain yield of 800 kg ha-1. In a glasshouse experiment supplied with adequate water, a soil dressing equivalent to 16 kg CuSO4.5H2O ha-1 (3.2 mg Culpot) completely corrected the deficiency. In a second glasshouse experiment, 2% CuSO4.5H2O solution was applied as single sprays at Feekes stages 3, 8, 9, 10 or 11, or as double sprays at Feekes stages 3 + 8, 3 + 9, 3 + 10 or 3 + 11. The most effective single spray was that applied at Feekes stage 10, but maximum dry matter and grain yield were obtained when a double spray was applied at Feekes stage 3 + 10. The effectiveness of soil and foliar applications of CuSO4.5H2O for correcting Cu deficiency of dryland wheat in Queensland soils are discussed in relation to water regime and supplying adequate Cu for both vegetative and reproductive growth.