Southeast Research and Demonstration Farm
Although southeast Iowa soils are generally very productive, phosphorus (P) and potassium (K) must be replenished in them to sustain acceptable crop yields. This study was initiated at the Southeast Iowa Research Farm to examine yield response to these nutrients where each is applied with the other in all combinations ranging from very inadequate (none) to sufficient. Corn and soybeans are grown in alternative years, a common crop rotation practiced in southeast Iowa.
Iowa State University
Henning, Stanley and Doorenbos, Russell, "Rotational Corn and Soybean Responses to P and K" (2001). Iowa State Research Farm Progress Reports. 1839.