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Minnesota Long-Term Phosphorus Management Trials: Phase 1 – The Build Period

Start Date: 2010
Principal Investigator: Albert Sims
Organization: University of Minnesota, Southern, Southwest, and Northwest Research and Outreach Centers
Status: Complete

Background Info

Phosphorus (P) management in Minnesota is based on one of two philosophical approaches: Build and Maintain (B&M) or Sufficiency. Some agriculturalist believe that higher fertilizer applications associated with the B&M approach is necessary to obtain and maintain the high production levels in today’s agricultural systems. In most cases, there is little evidence to support this belief, but seldom do experiments examine the two approaches in side-by-side tests. This research set out to answer the following: Is the maximum yield potential greater or similar in the B&M approach, in which there is little, if any, economic return for annual fertilizer applications, compared to the Sufficiency approach, in which there is generally an economic return for annual fertilizer applications?

Objectives

Establish within the same experiment, four STP interpretation class levels at six locations throughout Minnesota (build period)

Monitor STP levels and determine changes in soil P within defined soil P chemical fractions at various soil depths during the build period. This information will define differences in time and amount of P fertilizer needed to build STP levels at the various locations. In addition, P in defined soil P chemical fractions at various soil depths will monitor where P is located both chemically and physically during this build period.

Monitor crop biomass, P uptake, and yield across various STP interpretation class treatments during the build period. Evaluate crop response to the STP levels during the establishment period

Key Findings

Phase I, results indicate that in most of the cases, the plots achieve the desired extractable soil P levels for each STP category, depending on the soil P extractant evaluated suggested for Minnesota soils. The Morris site is the only one that has lower extractable P values for each category, but we still have to include the soil test P values for 2014 to get a final conclusion for this site. In general, results indicated that for most of the sites, we met the goals proposed on Phase I related to the establishment of the four soil test P categories.

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