Maximizing spring wheat productivity in the eastern Canadian Prairies II. Grain nitrogen, grain protein, and nitrogen use

The marketability of spring wheat (Triticum aestivum L.) across the Canadian prairies is largely dependent on grain protein content. New high-yielding cultivars require a large investment in fertilizer N to achieve milling quality standards. When high rates of N fertilizer are applied, N use efficiencies tend to decrease, lowering returns on investment. The objectives of this study were to identify patterns of N use for spring wheat cultivars and how they are influenced by agronomic management practices. Field trials were conducted in 2018 and 2019 in Manitoba, Canada, to evaluate N uptake timing, N remobilization from vegetative tissue and the resulting grain N yield and protein content. Three spring wheat cultivars were evaluated using five N fertilizer treatments with and without an application of a plant growth regulator (PGR). When high N rates were applied, average N use efficiency, for grain N production, was 60%. On average 21-36% of N uptake occurred after anthesis and this portion was highly dependent on late-season precipitation. Targeting increases in early season N accumulation and grain-fill remobilization, to produce optimal grain N levels, may be used to managing risk associated with unknown precipitation during the growing season. Cultivars tested produced similar grain N levels through fundamentally different N use patterns, indicating that there may be opportunity for breeding programs to target N use patterns that best fit environmental conditions of the Canadian prairies to maximize grain N production.