Since World War II and continuing to the present day, University of California (UC) research has established crop-specific “N rate guidelines” (Proebsting, 1948; Hartz and Bottoms, 2009). An N rate guideline is a range of N application rates expressed as a unit of weight area-1 (e.g., kg ha-1) that are generally able to achieve maximum yield. Most often, N application rate guidelines are printed in University of California Department of Agriculture and Natural Resources (UC DANR) publications and are extended to producers through information channels including: bulletins, production manuals, and field days.