Extension News

Tool Available to Help Producers Calculate the Iowa P-Index


AMES, Iowa -- Iowa State University (ISU) Extension in collaboration with USDA – NRCS and Iowa Department of Natural Resources (DNR) has developed a publication that can be used as a tool for gathering field information needed for calculating the Iowa Phosphorus Index.  The Iowa Phosphorus Index is a risk assessment tool for measuring the potential of phosphorus delivery from fields to surface waters. It is used in nutrient management and conservation planning tools for the USDA-NRCS and in manure management plans for the Iowa DNR.


DNR regulations require the Iowa Phosphorus Index be calculated for each individual management unit, or field, to establish its risk of phosphorus loss. These calculations require an estimation of sheet and rill erosion using a computer program known as RUSLE2 (Revised Universal Soil Loss Equation 2). RUSLE2 estimates average annual soil erosion as sheet and rill erosion in tons per acre per year for a given unit.


The “Data Collection Worksheet for RUSLE2 and Iowa Phosphorus Index” guides the user on how to collect information needed for RUSLE2 calculations, how to collect information needed for the Iowa Phosphorus Index calculations, and which set of data are appropriate to use for calculations. This publication is available only online at www.extension.iastate.edu/Publications/PM2021.pdf


Users of this publication should keep in mind that this document is an information gathering tool only. It is recommended that the users make sure they have the most recent version of the publication and the software available due to changing regulatory requirements. Calculation of soil loss using RUSLE2 and the Iowa Phosphorus Index should be done with assistance from NRCS service center personnel,  ISU Extension staff or consultants who are trained in interpreting and using the information gathered in this document. Those who have not been trained on RUSLE2 and Iowa Phosphorus Index should seek training and or guidance prior using  either software program.



Contacts :

Angela Rieck-Hinz, Agronomy, (515) 294-9590, amrieck@iastate.edu

Kapil Arora, Field Specialist, (515) 382-6551, pbtiger@iastate.edu

Jean McGuire, Extension Communications and Marketing, (515) 294-7033, jmcguire@iastate.edu