Fall 2005

Producers Must Account for Commercial Fertilizer on Manure Application Fields


By Karen Grimes, Iowa Department of Natural Resources

New rule

State law has required manure management plans (MMP) for confinement feeding operations that have more than 500 animal units since 1999. The 500 animal unit capacity includes confinement operations with more than 1,250 finishing hogs, 500 beef cattle or 350 dairy cattle.

These plans are used to determine crop nutrient needs and to plan manure application rates. They are valuable tools for crop producers to make the best use of nutrients, provide the optimum fertilizer for crop growth and to protect water quality. The Iowa Department of Natural Resources enforces this state law.

Until Aug. 26, 2005, animal producers were not required to keep records of additional commercial fertilizer applied to the manured fields. A new rule requires animal producers to track commercial fertilizer application, even on land that they do not own or rent. This new rule will require careful communication and cooperation between crop producers who want to use manure and the livestock producers who produce it.

However, it is important to track these nutrients to prevent over application of fertilizer and possible movement of excess nitrogen (N) or phosphorus (P) to a lake or stream where they can degrade water quality.

Record commercial P and N applied to manured fields

Starting Aug. 26, confinement animal producers who need a manure management plan (MMP) must account for both manure and commercial sources of nutrients applied to crop fields.

If the animal producer owns or rents the land, they must keep records of how much commercial nitrogen and phosphorus has been applied to fields where manure from a confinement is applied. The records should be kept with the manure management plan.

Statement needed when owner or renter is not the animal producer

If a confinement producer does not own or rent all the land where manure is applied, then the confinement producer must obtain a signed statement from the landowner or renter of the crop field, indicating how much commercial fertilizer has been or will be applied. The signed statements must be available at the confinement site prior to manure application. The statements are required even if no commercial N or P will be added.

Crop producers should expect animal confinement producers to contact the landowner, operator or renter to obtain a signed statement of intent. The animal producer will use this statement to adjust rates in the manure management plan, if needed.

Crop producers may also want to obtain a copy of the MMP for the fields that they own or rent.

The total N and P applied cannot exceed the maximum rates indicated in the MMP regardless of the source of the nutrient, commercial fertilizer or manure. If a crop producer decides to add commercial fertilizer that was not listed in their statement of intent, the crop producer must report this to the livestock producer. Crop producers should add additional fertilizer only after fall stalk tests or spring soil tests show the need for additional nutrients.


The DNR has developed a form that producers can use, making the process easier. Producers can check the DNR Web site at http://www.iowadnr.com/afo/forms.html under manure management plans to find form number 542-8167.


Records of actual application rates must be kept for three years or the length of the crop rotation, whichever is longer. Starting in August 2006, records must be kept for five years or the length of the crop rotation, whichever is longer. Livestock producers should keep the statements from crop producers, and any records of fertilizer added to the fields, for the same length of time.

For more information, contact Cindy Martens at (712) 262-4177 in the DNR Spencer field office or the regional DNR field office.


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