Maps of soil and crop properties must be of adequate quality for site-specific fertility management to be effective. Therefore, managers should consider assessing map quality in test fields before adopting site-specific fertility management for an entire farm. The objective of this study was to demonstrate how map quality assessment methods could be applied to the site-specific management of a central Kentucky field. Ordinary kriging, inverse distance weighted (IDW), radial basis function, and polynomial interpolation procedures were applied to two soil fertility data sets (200and 300-ft regular grids) from a central Kentucky field. Validation and cross-validation analyses generated substantially different results. Global and local polynomial interpolation procedures produced maps of unreliable quality. Ordinary kriging, IDW interpolation, and radial basis interpolation produced similar maps. Maps obtained using 300-ft grids were generally of poor quality. Substantial improvements occurred only for P soil test values and P fertilizer recommendations with the more intensive 200-ft sampling grids.