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Long dependent on “book values,” manure nutrients have changed over the decades.

Paula Mohr, Editor, The Farmer

August 9, 2022

4 Min Read
liquid manure being applied to field
BETTER DATA: Farmers often rely on old “book values” to estimate nutrient content in manure. University of Minnesota scientists are working to update values, helping farmers to apply the right amount of manure nutrients to cropland.Paula Mohr

For decades, farmers have relied on manure nutrient “book values” to help them figure out and apply adequate amounts of the organic fertilizer to field crops. Book values for manure provide estimates of nitrogen, phosphorus and potassium levels, based on animal species.

As production practices evolved over the years, so, too, has manure content. Different diets, genetics, housing, and manure storage and handling practices can impact nutrient values.

University of Minnesota scientists are taking a new look at manure book values and are in the process of updating nutrient information.

In a recent U-MN Extension blog, Nancy Bohl Bormann, U-MN graduate research assistant; Melissa Wilson, Extension manure management specialist; and Erin Cortus, Extension engineer, explain their current research project that involves the creation of a new manure nutrient database called ManureDB. The scientists collected information on more than 127,000 beef, dairy, poultry and swine manure samples tested at several laboratories between 2012 and 2021. They sorted the data between liquid and solid manure and by species.


They found that manure nutrient data have changed over time compared to older estimated manure nutrient book values listed in Manure Characteristics, published in 2004 by Midwest Plan Service. For example, in liquid dairy manure samples, they found a decreasing trend over time for total nitrogen (N) and phosphorus (P), and an increasing trend in ammonia nitrogen (NH4-N). In liquid beef manure samples, they found an increasing levels of total N, NH4-N and P. In liquid poultry manure samples, they found an increase in NH4-N and potassium (K), and a decrease in P.

In solid swine, dairy and beef manure samples, they noted an increasing trend for total N, P and K. In solid poultry manure samples, total N and K increased.

Evolving manure nutrient values were expected. Animal rations are not the same as 20 years ago, with changes depending on price, nutrient value and availability, Bormann says. Plus, animal housing and manure storage structures make a difference on water usage, which affects nutrient values.

“Animal nutrition, such as the inclusion of DDGs as a feedstuff or phytase, likely plays a large role in changing manure values,” she says. “Excess nutrients get excreted.”

Data collection, access

The scientists are working with the Minnesota Supercomputing Institute on ManureDB. They also are working on data-sharing agreements with additional laboratories. As they have access to data, they will continue to compare and add it to data they have.


“We have had positive feedback from our first cooperating labs and have heard from others that are interested in accessing this resource once it is available to the public,” Bormann adds.

As ManureDB evolves, the scientists say it will become available for public use, possibly by the end of the end of the year.

Most manure book values used today are from samples taken prior to 2003, according to Bormann. However, she has not seen a nationwide effort before to update them.

“Some labs have posted some of their manure nutrient data ranges,” she says. “It is challenging to coordinate multiple laboratories, terminology, analytical methods and common units for comparison.”

The U-MN manure book value research is supported by the USDA National Institute of Food and Agriculture; the Minnesota Department of Agriculture; the University of Minnesota College of Food, Agricultural and Natural Resource Sciences; and the Minnesota Supercomputing Institute.

“We have a diverse array of experts as stakeholders for this project and appreciate their input on this process,” Bormann says. If a lab is interested in learning more about partnering on the project, she encourages staff to contact [email protected].

To view a video with Bormann discussing the research, click on Manure nutrient trends and creating dynamic “book values” through ManureDB, from Livestock and Poultry Environmental Learning Community.

Additional information will be available in the future on the ManureDB website,


About the Author(s)

Paula Mohr

Editor, The Farmer

Mohr is former editor of The Farmer.

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