Agricultural engineer Bryan Woodbury (front left) collects a soil sample to characterize soil conditions following the field application of beef manure while agricultural engineer John Gilley (front right) and biological sciences aides Seth Lamb (kneeling) and Charles Hinds (standing) adjust small wind tunnel equipment to be used for air quality measurements. Photo by Peggy Greb.
Agricultural engineer Bryan Woodbury (front left) collects a soil sample to characterize soil conditions following the field application of beef manure while agricultural engineer John Gilley (front right) and biological sciences aides Seth Lamb (kneeling) and Charles Hinds (standing) adjust small wind tunnel equipment to be used for air quality measurements. Photo by Peggy Greb.

There are two types of people: Those who crinkle their nose at the smell of cattle manure and those who acknowledge it slightly, simply stating, “Smells like money.” Two very different reactions spurred by three main compounds that make up two-thirds of manure odors, says United States Department of Agriculture (USDA) and Agricultural Research Service (ARS) scientists.

Two of the compounds, isovaleric acid and butyric acid, are volatile fatty acids produced during manure decomposition, the third is 4-methulphnol, an aromic compound – the combination of the three can create a powerful punch.

“Manure disposal is a big concern for cattle feedlot operators,” says Agricultural Research Service agricultural engineer John Gilley in the Better Information for Improved Beef Manure Management report. “Fortunately, producers can reduce their use of commercial fertilizer—and their production costs—by using manure to fertilize their fields.”

In other words, manure isn’t going anywhere. But maybe its odor can.

According to the researchers, diet is a big contributor in odor emissions from beef manure. If a beef producer is using wet distillers grains with solubles (WDGS), then phosphorus, nitrogen and sulfur levels can increase – resulting in increased odor compounds.

In the study, manure samples were gathered from feedlot pens where a rations ranged in 0, 10 and 30 percent of WDGS. Samples that had levels of 135 pounds of nitrogen per acre were then distributed across test fields in no-till and disk till applications. Air samples were collected prior to water being added to the soil and after to measure moisture’s impact on odor emissions.

What they found was manure tilled into the ground, and then irrigates was the most effective way in reducing manure odors.

“Our results basically confirm that producers who want to use beef manure to improve soil quality can incorporate it into the soil to reduce odors and maintain nutrients,” ARS agricultural engineer Bryan Woodbury says. “Now we’re working on ways to manage manure in the feedlot that will improve its characteristics as a soil amendment.”

To read the full report from ARS, click here.