Reference strips (areas that have more than adequate nitrogen applied) have been used to normalize SPAD chlorophyll as well as canopy reflectance measurements to determine nitrogen (N) sufficiency of field areas to assess the need for additional N during vegetative growth periods.  Fields that have highly variable soils may require reference strips in several areas to minimize over- or under-applying N to the field.  This paper will address four scenarios for utilizing and/or locating reference strips.  These are: (1) based on the “best” crop condition that may exist in the field, (2) based on an average value from the reference strip regardless of soil texture differences, (3) based on soil map units, and (4) based on apparent electrical conductivity (EC) as a surrogate for soil texture.  Two commercial center pivot-irrigated corn fields with considerable soil variability were used to evaluate reference strip location.  Reference strips that included all the soil differences gave the best indication that in-season N was actually applied were needed by the crop.  Using an EC map as a surrogate for soil texture provides the information required to locate and use reference strips.