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.