Your Phosphorus Index
Manure Management Plan

If you have a confinement feeding operation with more than 500 animal units that was constructed or expanded after May 31, 1985, a 2002 state law requires you to implement the Iowa Phosphorus (P) Index as part of your manure management plan. This requirement is not new; yet implementing this particular part of the manure management plan requires a substantial amount of planning.

What is a P Index Plan?
A P Index plan requires that you run the P Index software on each field in your plan that receives manure. This software calculates the potential risk of loss of phosphorus (P) from a field. Depending on your risk rating, it will allow you to continue to apply manure on a nitrogen-based rate or will require that you implement some type of P management plan to reduce that risk of loss of P from the field. Because erosion is the primary factor determining loss of P from fields, the P Index software uses the Revised Universal Soil Loss Equation (RUSLE2) to calculate soil loss.

Phosphorus planning is a good practice for all livestock and crop producers when managing crop nutrients. Livestock producers who are required to submit Manure Management Plans to the DNR are required to include a Phosphorus Index according to a phase-in schedule set by 2002 legislation.

Don’t wait
With fieldwork and planting season upon us, please be advised of the deadline for your manure management plan. If you plan to develop your P Index plan on your own, start early. Make sure your soil samples are recent and have been taken according to the rules. Seek training to ensure the accuracy of using the P Index Calculator and the RUSLE2 software, have your data organized and readily available. Collect the necessary information from your neighbors who may receive manure as part of a manure easement or agreement. You will need to include P Index calculations and have the required soil samples on those fields as well as your own.

DNR field offices notify producers 45 days before the due date of each annual MMP update. If your plan is in the category of requiring a P Index, the notification letter you receive from the DNR field office may specifically state that you need to include the P Index with your next update, or it may simply explain the dates established by the law. In any event, even if you aren’t notified by the DNR, the rules require that you comply with the P Index MMP requirements that apply to your operation.

If you are notified by the DNR that your next MMP update must include the P Index, double check your records to make sure you filed an original MMP between April 1, 2002, and Oct. 24, 2004. If you didn’t, a P Index MMP is not yet required and you should contact the DNR field office to verify your records with theirs.

Hiring a Consultant
If you don’t plan to develop the P Index plan yourself, you should plan to contact a consultant who can help prepare your plan. Please see below for a link to a list of consultants.

If you do plan to hire a consultant, you should start this process early, perhaps two to three months in advance of when your plan is due. If you need to meet the soil sampling requirements, you may need to start that process six to nine months in advance of when your plan is due. Make sure you have copies of all of the needed information.

Below are some things to consider when choosing a manure management plan consultant:

  • Have you developed plans for my type of operation?
  • Have you been trained to develop P Index plans?
  • Will you provide recordkeeping assistance? 
  • What kind of follow-support do you provide for my plan?
  • What do you charge and what services will I receive for this charge? 

The plan for your operation should be more than an application rate; it should allocate nutrients to a field based on what crop will be grown and the nutrients needed to grow that crop. Understanding how the plan was developed and how changes to your daily operation may affect your plan are crucial. Manure is a valuable nutrient resource so manage it wisely

Manure and Nutrient Management Plan Resources
Iowa Manure Management Action Group (IMMAG)

Manure Management Plan Consultants

Iowa P Index Calculator

The Iowa Phosphorus Index and Manure Management Plans for Confinements

IDNR Forms for Manure and Nutrient Management Plans

Data Collection Worksheet for RUSLE2 and Iowa Phosphorus Index

· Iowa Manure Matters Odor and Nutrient Management Newsletter, Spring 2007
· Iowa DNR web site,