Synergism of Nitrogen Rate and Foliar Fungicides in Soft Red Winter Wheat

Projected global demand for small grain cereals emphasizes the need for sustainable intensification with higher crop yields. Field studies on soft red winter wheat (Triticum aestivum L.) examined interactions among three fertilizer N rates, eight fungicide application strategies, and various cultivars grown in nine field environments in Ontario, Canada. A synergistic response occurred when a high rate of N was applied with a fungicide strategy that controlled disease. Overall, compared to a typical N rate of 100 kg ha(-1) and no fungicide, yields increased by an average of 1.45 Mg ha(-1) when N was applied at 170 kg ha(-1) with the most intensive fungicide treatment pooled across sites. This yield response varied from 0.80 to 2.11 Mg ha(-1) depending on field site and pooled across cultivars. Fungicide strategies that included a T2 (flag leaf timing) or T3 (anthesis timing) produced the highest yields across environments, especially at the high N rate and in most cultivars. The crop response to fungicide depended on the susceptibility of the cultivar to foliar disease and whether the field environment was favorable for disease development. High N rates increased spike numbers and kernels spike(-1), whereas fungicides mainly increased kernel weight and kernels spike(-1). Prior to an economic analysis, results from this study indicates clear potential for increasing wheat performance by intensifying management with increasing N and deploying fungicide application strategies, especially in some cultivars and in high yielding environments that may be favorable for disease development.