Effect of Nitrogen Fertilizers on Severity of Tan Spot of Winter Wheat

Field experiments were conducted over a 3-yr period in a split-plot design with the winter wheat (Triticum aestivum) cultivar TAM 105. Main-plot treatments were no fertilizer, NH 4 SO 4 , and CaNO 3 (each at 112 kg/ha total N); and subplots were presence or absence of tan spot. Fertilizers were applied in the fall (one-third of total N applied), late March (one-third), and late April (one-third). Disease evaluation was at the soft dough stage (.)