Between the years of 1961 and 2001, two 12.5-ha fields in Illinois were sampled for soil pH, and available P and K in a 24.3-m grid. One field was sampled beginning in 1961 while the other field was sampled from 1982. At each sampling, the samples were obtained in the same grid. This resulted in the ability not only to compare grid sample density to delineate fertility patterns within the fields, but also to determine the rate of soil test change with P and K applications, the change in fertility patterns and the change in each grid sample soil test value with time. The results of the study show that without heavy fertilizer applications soil P and K patterns are stable. Heavy applications of P and K mask natural P and K patterns. Changes in soil P and K values are not uniform over time, but vary with soil differences, and resemble natural fertility patterns. Areas requiring limestone additions at the beginning of the study were similar to areas requiring limestone all through the study. Other areas needed little or no pH amendment throughout the study. Individual grids whose values changed drastically between sampling were affected by fertilizer misapplication (P and K), or natural/manmade pH differences at a small spatial scale.