Soil test N and P significantly affect crop production in the Canadian Prairies, but vary considerably within and between producer's fields.  This study describes the variability of crop yield, soil test N and P within and between producer's fields in the context of variable fertilizer rates.  Yield, terrain attribute, soil test N and P data were collected for 10 fields in Alberta, Saskatchewan and Manitoba Canada in 2014 and 2015.  The influence of fertilizer management on crop yield, soil test N and P was attributed to the variability between farms.  Development of management zones for fertilizer management of crop yield will benefit from analyses within farms at the field scale.