With MAP and DAP prices still relatively high, what concerns, if any, should farmers have about how much value they are getting? Here are a few things that you should know about what happens to P when it is applied to the soil.

"One concern I have is that some growers treat their P and K like balancing a checkbook, trying to calculate what is taken off the field and putting that amount back on in fertilizer. In almost all cases, this type of accuracy is not needed for removal-based guidelines," says nutrient management specialist Dan Kaiser.

This article highlights revisions to Iowa State University (ISU) soil-test interpretations and application guidelines for phosphorus (P), potassium (K) and lime in an update of extension publication PM 1688 "A General Guide for Crop Nutrient and Limestone Recommendations in Iowa."