Effect of nitrogen on the availability of previous and current applications of copper fertiliser for grain yield of wheat grown in south-west Western Australia
1993
Brennan, R.F. (Western Australian Dept. of Agriculture, Albany. Albany Regional Office)
Twenty-one field experiments located in different rainfall zones on a range of soils that had been fertilised with Cu fertiliser 16-23 years previously were used to examine the effect of level of N fertiliser on the grain yield of wheat. At 20 sites, there was no further response to currently applied Cu fertiliser. The highest level of N fertiliser applied (46-92 kg N per ha) did not induce Cu deficiency in wheat plants. The addition of Cu increased Cu concentration in the youngest emerged blade (YEB) and grain, whilst increasing the rate of N fertiliser generally decreased these concentrations of Cu. At 2 sites in the Jerramungup district, the addition of N induced Cu deficiency in wheat, which reduced grain yields. Increasing the rate of N fertiliser reduced Cu concentration in the YEB to deficient levels. At 1 high-yielding site, the highest level of N (92 kg per ha) reduced Cu concentration to 1.0 mg per kg in the YEB and 1.0 mg per kg in the grain without reducing grain yield. It was concluded that high levels of N fertiliser application did not increase the wheat plants' requirement for Cu fertiliser where Cu fertilisers had been applied at the recommended level in the past 23 years. Where Cu fertiliser has been applied at lower-than-recommended levels in previous years, Cu deficiency occurred where high levels of N were applied.
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