Minnesota Long-Term Phosphorus Trial-Phase II:Testing Yield Response and Potential.

Phosphorus fertilizer management in Minnesota is based on one of two philosophical approaches, Build and Maintain (B&M) and Sufficiency. In Phase I, long-term experiments were established at six sites across Minnesota. At each site, four soil test P (STP) Interpretation Classes of Low, Medium, High, and Very High were established as whole plots over a four year period. The initiation of Phase II started in fall 2014 with splitting each whole plot where one split-plot received no additional P fertilizer, subsequent crop relied on residual soil P established during Phase I, and the other received 168, 101, 34 and 34 kg P₂O₅ ha^-1 in the Low, Medium, High, and Very High whole plots, respectively.  Grain yield and grain P removal response to the added P fertilizer was determined and compared across STP Interpretation classes. Corn was grown at all sites in 2015. Overall, 2 of the 6 sites showed significant response to applied-P only in the Low and Medium soil classification classes (Becker, Crookston). A similar trend was observed at Lamberton, but differences were not significant. Grain P removal was more responsive and 4 of the 6 sites showed greater P removal with applied-P especially in the Low and Medium clasification classes.