Response of a conventional and a semi-dwarf wheat, and rape, to superphosphate

Abstract

The effects of seven levels of superphosphate (nil, 40,80,120, 200 and 300 kg ha-1) on Eagle, a conventional wheat, and Condor, a semi-dwarf wheat, and Oro rape, were studied in 1975 and 1976 near Yass, New South Wales. The experiments also provided limited information on the combined effects of nitrogen fertilizer (70 kg N ha-1) and wheat sowing rates (30 and 60 kg ha-1). In both years the response to superphosphate by the two wheats was similar, the highest superphosphate rate more than doubling yield, but the response by the rape was much less. Condor outyielded Eagle by 32%, and Oro by 63%. Wheat yields were 22% greater at the higher sowing rate. In 1975, nitrogen reduced wheat yields by 23%. There was no residual effect on 1975 fertilizer treatments on crops sown in 1976. The effect of increasing superphosphate rates was due to the production of more spikes per hectare; the heavier sowing rate also increased this yield component. The superiority of Condor over Eagle lay in the production of more, and greater weight of, grains per spike.