1. Spacial Variability of Soil Test Phosphorus in a Northern Corn Belt Field

For some time, an increasing number of fertilizer dealers, crop consultants, and farmers have reported substantial year-to- year variability in soil test values for phosphorus (P) and potassium (K). Frequently, this variation could be explained by such factors as extremes in soil moisture content at the time of sample collection. In many situations, however, this variation was due to the fact that soil samples were not collected from the same location in the field in two consecutive years. The introduction...