EFFECTS OF HIGH RATES OF NITROGEN ON NEEPAWA WHEAT GROWN UNDER IRRIGATION. I. YIELD AND PROTEIN CONTENT

Abstract

A hard red spring wheat (Triticum aestivum L. cv. Neepawa) was grown at five sites in southern Alberta during a 3-yr period in irrigated field experiments in which rates of N and P, and N source were varied. Response of yield and protein content varied between sites and treatments, mainly because of differences in soil nutrient levels, soil texture, and irrigation management. The highest yield, 53.3 q/ha, was obtained on a clay soil that contained relatively high levels of available N and P. Grain yield and protein content responded mostly to N. Yields were maximized with about 100 kg N/ha on soils where fertility was relatively low. The highest protein content (dry basis) was 20.7%. When soil N was relatively low, it was possible to increase the protein content 51–76% by applying high rates of N, either to the soil or as a urea spray at flowering, and by subjecting the plants to a soil moisture stress during the flowering stage. N applied as a urea spray did not affect grain yield.