Dryland Winter Wheat Yield, Grain Protein, and Soil Nitrogen Responses to Fertilizer and Biosolids Applications

Applications of biosolids were compared to inorganic nitrogen (N) fertilizer for two years at three locations in eastern Washington State, USA, with diverse rainfall and soft white, hard red, and hard white winter wheat (Triticum aestivumL.) cultivars. High rates of inorganic N tended to reduce yields, while grain protein responses to N rate were positive and linear for all wheat market classes. Biosolids produced 0 to 1400 kg ha−1(0 to 47%) higher grain yields than inorganic N. Wheat may have responded positively to nutrients other than N in the biosolids or to a metered N supply that limited vegetative growth and the potential for moisture stress-induced reductions in grain yield in these dryland production systems. Grain protein content with biosolids was either equal to or below grain protein with inorganic N, likely due to dilution of grain N from the higher yields achieved with biosolids. Results indicate the potential to improve dryland winter wheat yields with biosolids compared to inorganic N alone, but perhaps not to increase grain protein concentration of hard wheat when biosolids are applied immediately before planting.