Karina P. Fabrizzi, Department of Soil, Water, and Climate, University of Minnesota, Anoka, MN, Albert L. Sims, University of Minnesota, Crookston, MN, Daniel E. Kaiser, Dept. of Soil, Water, and Climate, University of Minnesota, St. Paul, MN, Carl Rosen, Department of Soil, Water, and Climate, University of Minnesota, St. Paul, MN, Jeffrey S. Strock, Soil, Water and Climate, University of Minnesota, Lamberton, MN and Jeffrey A. Vetsch, University of Minnesota, Waseca, MN
Phosphorus (P) fertilizer management in Minnesota is based on one of two philosophical approaches, Build and Maintain (B&M) and Sufficiency. In recent years, it is argued that higher fertilizer applications associated with the B&M approach are necessary to obtain and maintain greater production levels in today’s agricultural systems. The purpose of these trials was to establish long-term experiments that could be used to test P management strategies on soils with a defined long-term phosphorus history. Six experimental sites were located across Minnesota. At each site, a split-plot randomized complete block experimental design: whole plot treatment is the targeted or established soil test P (STP) Interpretation Class. The STP classes targeted in the whole plots are Low, Medium, High, and Very High. Soil samples were taken at a depth of 15 cm. All sites had corn-corn-corn-soybean rotation except Crookston (corn-soybean-hard red spring wheat-soybean). All sites had reached significant differences among the four established interpretation classes: Very High>High>Medium>Low class. Results for the end of Phase I indicate that grain yield response to STP classes varies among sites and years. Grain P removal was very responsive to the level of applied P or the target STP class. At all locations, as the Interpretation Class went from Low to High or Very High, the amount of P removed in the grain also increased.