Phosphorus Loss Assessment

The Phosphorus Source Assessment Tool

The Phosphorus Source Assessment Tool is used to estimate the relative contributions of various land uses and point sources to P loading in a watershed.

The Minnesota Phosphorus Index

The Minnesota Phosphorus Index (P Index) is a management tool to estimate the relative risk that phosphorus is being lost from an agricultural field and delivered to a nearby ditch, stream, or lake. It allows the user to evaluate management options that can reduce the risk.

Brief descriptions

How to use the Index

  • "The Minnesota Phosphorus Index: Assessing Risk of Phosphorus Loss from Cropland" PDF iconmnpi_umnext08423.pdf (12/18/06) Describes how to correctly use the MN P Index and related tools to assess risk of P loss from agricultural fields. Online version and hard copy are available from University of Minnesota Extension.
  • "Effects of Swine Manure Applications on Soil Nutrient Levels and Phosphorus Loss Risk" PDF iconmnpi_umnext08424.pdf (5/19/07) An example of how to use the MN P Index to analyze swine operations. Online version and hard copy are available from University of Minnesota Extension.

Details about the model

Download the program

To install the Minnesota P Index:

  1. Download the setup program by right-clicking on the link above and saving the file to your computer.
  2. Uninstall any previous versions of the MN P Index.
  3. Run the setup program by double-clicking on <MNPIndexSetup.exe> in your file manager. The program will be installed, and a icon MN P Icon will be placed on your desktop or in your start menu. The default folder location for the program is: C:\Program Files\Minnesota P Index\.

Some of the program changes from the previous version:

  • Corrected some errors in the reports and data export functions.
  • Updated RUSLE2 to the June 2006 version.
  • Anhydrous ammonia injections are now accounted for in estimating the fall soil condition. Previously, anhydrous ammonia was only considered when estimating fall residue cover.

Screening Tool

  • Download the Rapid Phosphorus Index PDF iconrapidpi.pdf (8/25/06)

The Rapid Phosphorus Index (RPI) is a small set of indicators and thresholds based on the MN P Index. It can be used as a screening tool to eliminate the lowest risk sites or highlight the highest risk sites where the full MN P Index should be applied.

The inputs needed for the RPI are manure and fertilizer application rates and method, soil test P, erosion rate, distance to water, and whether the soil is poorly drained.

The RPI is three separate screening tools of varying sensitivity. Choose the one appropriate for your goals. The high sensitivity version identifies sites likely to have a MN P Index value greater than 2; the medium sensitivity version identifies sites likely to be greater than 4; and the low sensitivity version only identifies sites likely to have a MN P Index value greater than 6. The RPI will occasionally mis-identify a field as either higher or lower risk. Consider which type of error you can tolerate. For example, if it is important not to miss any high risk sites, choose a higher sensitivity tool. If it is important to minimize the number of fields analyzed with the MN P Index, choose a lower sensitivity tool.


Workshops and Presentations

Key points:

    • Phosphorus sources and transport mechanisms
    • Structure of the MN P Index
    • How to interpret MN P Index results
    • Where and how is the MN P Index used?
    • What inputs is the MN P Index sensitive to?


Initial funding for development of the Minnesota Phosphorus Index came from the Minnesota Environmental Quality Board and the University of Minnesota Extension Service in response to the results of the Generic Environmental Impact Statement (GEIS) on Animal Agriculture. Current funding is from a U.S. Environmental Protection Agency 319 grant sponsored by the Minnesota Department of Agriculture.

The Phosphorus Index Development Team:

John Moncrief, Paul Bloom, Dave Mulla, Neil Hansen,
Gyles Randall, Carl Rosen, Ed Dorsey, and Ann Lewandowski
University of Minnesota

Input and Critique:

Matt Drewitz and Mark Dittrich
Minnesota Department of Agriculture

Jeff St.Ores, Pete Cooper, and Robin Martinek
Natural Resources Conservation Service

Chris Zadak, Jim Klang, and Dave Wall
Minnesota Pollution Control Agency

Greg Larson
Board of Water and Soil Resources