EFFECT OF IRRIGATION AND NITROGEN FERTILIZER ON THE YIELD AND PROTEIN CONTENT OF SOFT WHITE SPRING WHEAT

Abstract

Field experiments were conducted over four growing seasons in southern Alberta to develop improved irrigation and nitrogen fertilizer recommendations for soft white spring wheat (Triticum aestivum L.). Irrigation to provide available water in the root zone to maturity maintained acceptably low protein content of soft wheat fertilizer-N plus soil test NO3-N levels from 140 to 208 kg ha−1. Nitrogen fertilizer increased protein content in all 4 yr of the study and increased yields each year except 1981 when the soil contained a high level of NO3-N. The protein content was not raised above the level considered acceptable for the domestic Canadian market (10.5%, moist basis) unless fertilizer rates in excess of the economic optimum level were applied. Fertilizer-N response curves were developed for each cultivar, irrigation treatment, and year combination. These were used to show the relationship between yield and the level of fertilizer N plus soil NO3-N which would result in economic optimum yields of soft white spring wheat of acceptable protein content. The results suggest N rates can be increased about 30 kg ha−1 for each t ha−1 increase in the target yield of the producer.Key words: Wheat (soft white spring), Triticum aestivum L., irrigation, nitrogen fertilizer, protein, target yield