SULFUR AND NITROGEN-FERTILIZATION OF WINTER-WHEAT

Winter wheat (Triticum aestivum L.) is used throughout the Great Plains for grain and forage production and increased instances of S deficiencies have been reported there in recent decades. Limited recent research data are available from this area on wheat grain yield response to S fertilization, and virtually no data exists on wheat forage response to S fertilization. Field research was conducted for two crop years starting in the fall of 1988 at two sites to evaluate effects of N and S on wheat forage and grain yields and quality. Nitrogen rates (0, 50, and 100 lb/acre as urea-ammonium nitrate [UAN] solution) and S rates (0, 7.5, and 15 lb/acre as ammonium sulfate [AS] or ammonium thiosulfate [ATS] solutions) were evaluated. Protein and S content of early-harvested forage (Feekes stage 3-5, normal grazing period) were consistently and significantly increased by the addition of S. Sulfur content of late-harvested forage (Feekes stage 10, late boot-early heading stage) was increased in 1 of 2 site-years, but S had no effect on protein of late-harvested forage. Sulfur fertilization had minimal effects on wheat forage yield or grain yield and quality. Nitrogen, with or without S, significantly increased protein content of early- and late-season forage at all locations. Less consistent, but sometimes significant, N responses also were observed for forage and grain yields and grain protein.