CHLORIDE FERTILIZER EFFECTS ON STRIPE RUST DEVELOPMENT AND GRAIN-YIELD OF WINTER-WHEAT

Seven winter wheat [Triticum aestivum] cultivars grown in the field on an Aquultic Argixeroll (pH 5.5) were spring topdressed with (NH4)2SO4 or NH4Cl to determine the effect of chloride (Cl) on the progress of stripe rust disease. Choride rates of 0, 76,152, and 304 kg ha-1 were applied at a constant N rate of 120 kg ha-1. Plots were inoculated with Puccinia striiformis, using a composite spore collection representing races common in the Willamette Valley of Oregon [USA]. Stripe rust severity was determined weekly, and disease progress curves were generated for each Cl treatment on the four cultivars developing the disease. Chloride reduced the apparent infection rate on Purplestraw, Yamhill, and Rew cultivars in one year but increased the apparent infection rate on Rew in another year. Results confirm that Cl-containing fertilizers can influence stripe rust development, but the effects are small and of questionable practical value. Chloride applied at 76 kg ha-1 significantly increased grain yield by an average of 0.50 Mg ha-1, possibly by reducing stress from take-all root rot caused by Gaeumannomyces graminis var. tritici.