Iowa State University Extension in collaboration with USDA's NRCS and the Iowa Department of Natural Resources has developed a publication that can be used as a tool for gathering field information needed for calculating the Iowa Phosphorus Index. The P-Index is a risk assessment tool for measuring the potential of phosphorus delivery from fields to surface waters.

The P-Index is used in nutrient management and conservation planning for NRCS and in manure management plans for the Iowa DNR.

DNR regulations require the Iowa P-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 P-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 this document is an information gathering tool only. It is recommended that users make sure they have the most recent version of the publication and software available due to changing regulatory requirements. Calculation of soil loss using RUSLE2 and the Iowa P-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.