Animal Production Science Animal Production Science Society
Food, fibre and pharmaceuticals from animals

Effect of late application of nitrogen on the yield and protein content of wheat

WM Strong

Australian Journal of Experimental Agriculture and Animal Husbandry 22(115) 54 - 61
Published: 1982


On the Darling Downs the growth and yield of a semi-dwarf wheat (cv. Oxley) under supplementary irrigation was increased by the application of up to 400 kg/ha of nitrogen (N) at planting. Nitrogen at 50 or 100 kg/ha applied at the boot stage to supplement 100 kg/ha applied at planting increased grain yield by 459 and 478 kg/ha, respectively. However, yields were still below those where all the N was applied at planting. In contrast, supplementary N (0, 25, 50 or 100 kg/ha) at flowering or after flowering generally did not increase grain yield. One exception to this was where only 50 kg/ha was applied at planting; an additional 100 kg/ha at flowering increased grain yield by 602 kg/ha. Applied at planting, more than 200 kg/ha of N was needed to produce premium grade wheat (i.e. protein content above 11.4%). To achieve this protein content where 100 kg/ha had been applied at planting an additional 100 kg/ha was needed at the boot stage or 50 kg/ha at flowering. Applied after flowering, up to 100 kg/ha of additional N produced wheat of a protein content too low to attract a premium payment. A similar quantity of N was assimilated whether the entire N application was applied at planting or where the application was split between planting and boot or flowering. Less N was assimilated when the application was split between planting and after flowering. More N was assimilated from soil than from foliar applications at the boot stage. Soil and foliar applications were equally effective at flowering in increasing the amount of N assimilated as well as the grain protein content. However, after flowering foliar application was the more effective method. The application of N at flowering to increase the protein content of this semi-dwarf cultivar is not an attractive commercial practice. The price ratio of premium to Australian Standard White wheat in recent years (<1.071 ) is less than that needed (1.0954-1.3013) to justify splitting the N application to lift grain protein content above 11.4% at the expense of yield.

© CSIRO 1982

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