Sampling studies in North Dakota conducted from 1994 to 2003 showed that variable-rate N application could be practically directed with zone soil sampling. Results from variable-rate N studies using zone soil sampling were often less than rewarding due in part to the use of a whole-field predicted yield-based formula for developing the N recommendation in each zone. Nitrogen rate studies on spring wheat and durum were established in 2005 through 2009 to reexamine N recommendations. The results of the study and archived wheat N response data showed that the state should be divided into three separate N response regions. Within each region historic yields from low to high productivity are chosen. The gross N rate was determined using the return-to-N concept developed in the US corn-belt states but with additional consideration for wheat protein value. The gross N rate is then modified by credits for previous crop, soil test N from zone soil sampling, tillage systems and other soil characteristics unique to each field or field zone.