COPPER DEFICIENCY OF WHEAT - EFFECTS OF SOIL-WATER CONTENT AND FERTILIZER PLACEMENT ON PLANT-GROWTH

In rainfed wheat (Triticum aestivum L.) growing on copper (Cu) deficient soil, the top 15 cm of the soil profile where Cu fertilizer is placed, may dry out during the growth of the crop. It is unknown if this event would decrease the plant's access to the applied Cu. In a glasshouse experiment, wheat was grown in a severely Cu-deficient Chromustert where the Cu-fertilized soil was either watered throughout the experiment or not watered after the early stem extension stage of growth. Copper was applied in granules of a thermoplastic polymer matrix impregnated with CuSO4.H2O (Cu-polymer) or as finely ground CuSO4.5H2O (Cu-sulfate) at rates of 0 and 30 mg Cu pot-1 (equivalent to 0 and 37 kg ha-1). The plants were harvested at grain maturity when measurements of dry matter and grain production, and content of Cu, nitrogen (N) and phosphorus (P) were recorded. In both water regimes, plants grown in pots without added Cu produced no grain. The addition of Cu-polymer generally failed to overcome Cu deficiency in both water regimes. However, when the soil containing the Cu-polymer was watered throughout the experiment, Cu content of the shoots increased and a few deformed grains were formed. Plants receiving Cu-sulfate produced grain, but only when the Cu-fertilized soil was watered throughout the experiment. The addition of Cu-sulfate increased the content of Cu, N, and P, the yield of straw, and the number of tillers in both water regimes. The results illustrate the interaction between availability of applied Cu, water regime, Cu uptake, and grain formation in wheat, and demonstrate the importance of timeliness of rainfalls which rewet the Cu-fertilized soil of rainfed wheat crops growing on Cu-deficient clay soils.