Northern Research and Demonstration Farm
A study was conducted from 1976 to 2002 to evaluate the effect of annual phosphorus (P) fertilization on soil P and yields of corn and soybeans. Both crops were grown each year in a rotation by alternating them between two halves of the area. Cornstalks were chisel-plowed in the fall and disked in the spring. Soybean residue was disked in spring. The Webster soil predominated, and there were small areas of Canisteo. Soil pH varied from 6.0 to 8.2. Less than 15% of the area had a pH of 7.3 or higher (calcareous).
Iowa State University
Mallarino, Antonio P. and Rueber, David, "Long-term Phosphorus Fertilization for Corn-Soybean Rotations" (2004). Iowa State Research Farm Progress Reports. 1400.