Adequacy of current fertilizer recommendations for site-specific management

To realize the benefits of site specific management (SSM)/variable rate fertilizer application (VRA), fertilizer management and recommendations must be site-specific. Since most fertilizer recommendations were developed on a state or region scale, it is reasonable to question whether these recommendations can be adequately applied to site-specific management that attempts to account for within-field variability. Uniform fertilizer management across an entire field can result in overfertilization of some areas and under-fertilization of others. In either case, this is an economic loss to the producer. Over-fertilization increases the probability of nutrient loss from erosion or leaching whereas under-fertilization limits yield and grain or forage quality. This chapter discusses the general nutrient and soil amendment areas including nitrogen, phosphorus, potassium, and lime. For each of these areas, the chapter reviews what is the adequacy of current fertilizer recommendations for VRA and SSM.