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Proper manure sampling, analysis and application imperative to get the most value.

Kevin Schulz, Editor

March 26, 2024

5 Min Read
Tractor spreading manure
SPREADING MANURE: A tractor applies manure to a field.Courtesy of National Pork Board

Livestock and crop farmers agree that manure is a valuable resource for crop nutrients, and Nancy Bohl Bormann says it’s important that all parties respect the resource.

Bohl Bormann, a Ph.D. candidate in land and atmospheric science at the University of Minnesota, offers tips for farmers to get the most out of their manure pits and piles.

“One of the biggest things is keeping detailed records” of a farm’s manure samples and application records, she says.

For new operations, samples should be collected annually for the first three years of operation “and then every three to four years after that if there are minimal changes and that aligns with your nutrient management plan requirements,” Bohl Bormann says.

Though Bohl Bormann is currently a Ph.D. student, she has years of practical experience in the field as an environmental services senior manager for the Maschhoffs, a pork production company based in Illinois. Working out of north-central Iowa, she helped farmers create nutrient management plans.

She also encourages producers to collect new samples whenever livestock undergo dietary changes or if other management changes occur that may alter the manure makeup.

The timing of sample collection, before application or at the time of application, each has its pros and cons.

“Obviously, before application it’s nice to have a picture of what nutrients you will have so you can update your planned application rates prior to your application,” she says, “but maybe you won’t get a fully agitated sample, so it may not be the most accurate depending on how soon before you apply.”

Taking samples at the time of application will give the most accurate measure of nutrients that will be applied, “especially if you take numerous samples to get a good picture throughout your manure storage of what you have for nutrients,” she says. The downside of this collection timing is that the analysis may not be complete before application. “But then you can calculate if additional fertilizer is needed,” she says.

Bohl Bormann admits that the best of both worlds is to take samples both before and during application, adding, “as I say, the more samples the better for this variable product that we are dealing with for nutrients.”

Representative sample

Regardless of when a manure sample is taken, Bohl Bormann says it’s best to take a representative liquid sample while a deep pit is being agitated and during pumping if possible. If sampling at another time, “just try to a get the whole manure profile … because sometimes nutrients do settle.”

Safety is also stressed when collecting liquid manure samples, as gases can be deadly, and drowning risks exist.

When it comes to testing solid manure, she suggests taking samples while loading occurs, taking a little from each load or from various depths of a pile “while avoiding the crusty parts.”

Once many samples have been gathered to present a thorough picture of the nutrient profile of liquid or solid manure, Bohl Bormann says, they should be combined and mixed well in a bucket. From this bucket sample, take a subsample and place it in a plastic, sealable container. Then, double bag the container.

“Sometimes I’ll even tape it shut because no one wants to risk any leaks in the mail,” Bohl Bormann says.

Be sure to properly label and complete the submittal form so that the lab will have proper sample identification that you will understand when you receive results back.

Bohl Bormann says that labs may provide containers for sample submissions. Samples should be kept cool or even frozen prior to shipping to the laboratory to minimize microbial activity.

Results are back — now what?

The manure macronutrient of most interest is nitrogen, but producers should know how to read the lab’s manure analysis, including whether nitrogen is reported in total nitrogen or total Kjeldahl nitrogen. TKN does not include nitrate and nitrite, which is a small fraction of the total nitrogen, Bohl Bormann says, so the total N or TKN numbers are usually ever close.

She adds that it’s also important to know how much of the reported nitrogen is in the inorganic fractions such as ammonium-N, nitrate or nitrite, which are plant available, or how much is in the organic fraction, which is not readily available for plants.

Bohl Bormann also encourages producers to be cognizant of the form in which both phosphorus and potassium are reported in the analysis. For instance, P2O5 is equal to P multiplied by 2.29, and K is multiplied by 1.2 to get the K2O level.

Understanding whether the manure was analyzed on a dry or wet basis is important, as well as the unit that is reported, such as a percent, pounds per 1,000 gallons or pounds per ton.

Next steps

Once the sampled manure has been analyzed, then it’s time to apply, and Bohl Bormann says producers need to remember how important it is “to calculate the application rates to match the crop that you’re going to be applying the nutrients to.”

This means that the soil should be properly sampled to indicate what nutrients are needed, and manure-handling equipment should be properly calibrated.

Check out Bohl Bormann’s complete presentation from the Nutrient Management Conference.

The University of Minnesota also has a YouTube page with a variety of manure-management resources.

Introducing ManureDB

As livestock and livestock feeding have changed over the years, so have the values of the manure produced. Nancy Bohl Bormann says published book values are several decades old; thus, as her doctorate project, she is assisting with the creation of a manure-nutrient database called ManureDB.

As she explains, the University of Minnesota received grant funding to create ManureDB, which is a collaboration of laboratories and universities that analyze manure. A public website has been launched from which data can be downloaded.

Manure book values are used for developing manure-management plans, establishing nutrient-management policy, creating a baseline for nutrient-management education, and modeling nutrient cycling and gas emissions.

“You need some sort of baseline to start from, and this will provide that,” Bohl Bormann says.

Currently, there are close to 500,000 samples in the database, and she says more are being processed for entry.

Click here to read a blog that Bohl Bormann recently wrote about the ManureDB project.

About the Author(s)

Kevin Schulz

Editor, The Farmer

Kevin Schulz joined The Farmer as editor in January of 2023, after spending two years as senior staff writer for Dakota Farmer and Nebraska Farmer magazines. Prior to joining these two magazines, he spent six years in a similar capacity with National Hog Farmer. Prior to joining National Hog Farmer, Schulz spent a long career as the editor of The Land magazine, an agricultural-rural life publication based in Mankato, Minn.

During his tenure at The Land, the publication grew from covering 55 Minnesota counties to encompassing the entire state, as well as 30 counties in northern Iowa. Covering all facets of Minnesota and Iowa agriculture, Schulz was able to stay close to his roots as a southern Minnesota farm boy raised on a corn, soybean and hog finishing farm.

One particular area where he stayed close to his roots is working with the FFA organization.

Covering the FFA programs stayed near and dear to his heart, and he has been recognized for such coverage over the years. He has received the Minnesota FFA Communicator of the Year award, was honored with the Minnesota Honorary FFA Degree in 2014 and inducted into the Minnesota FFA Hall of Fame in 2018.

Schulz attended South Dakota State University, majoring in agricultural journalism. He was also a member of Alpha Gamma Rho fraternity and now belongs to its alumni organization.

His family continues to live on a southern Minnesota farm near where he grew up. He and his wife, Carol, have raised two daughters: Kristi, a 2014 University of Minnesota graduate who is married to Eric Van Otterloo and teaches at Mankato (Minn.) East High School, and Haley, a 2018 graduate of University of Wisconsin-River Falls. She is married to John Peake and teaches in Hayward, Wis. 

When not covering the agriculture industry on behalf of The Farmer's readers, Schulz enjoys spending time traveling with family, making it a quest to reach all 50 states — 47 so far — and three countries. He also enjoys reading, music, photography, playing basketball, and enjoying nature and campfires with friends and family.

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