'Manuresheds' might be the key to managing uneven nutrient distribution

Researchers and partners along ag supply chains around the globe are seeking better ways to manage nutrient-rich manure from today’s animal operations.

Described as a wicked problem, manure management has many interdependent factors making it seem almost impossible to solve. The crux of the issue: the way nutrients move through the system.

Think of it this way: Corn and soybeans are raised for feed in one area, then shipped to a dairy farm in another region. In the past, farms that raised feed for their livestock would likely spread the manure produced by that livestock on their crop ground. Today that is rare and ultimately creates imbalances.

“What we are seeing is uneven nutrient distribution, or a surplus of nutrients in some places, and a scarcity in others,” says Sheri Spiegal, research scientist with the U.S. Department of Agriculture’s Agricultural Research Service. “The roots of this problem really come from how agriculture has changed over the past 60 to 70 years. Before, it was not uncommon for five or six crops and livestock types to be grown on the same farm, with the integration of crops and livestock. That translated into more circularity where nutrients cycled through crops to livestock and back to the crops.”

Through concentration and specialization, U.S. agriculture has seen tremendous productivity gains, but fewer crops or livestock types are grown on a given farm or farming area. “That has led to a more fragmented nutrient cycle in which we lose some of those nutrients in ways we don’t want, and at the same time, we need to import expensive nutrients into other areas,” she says.

Manuresheds

Spiegal and her colleagues have described “manuresheds” as a way to manage uneven nutrient distribution. Taken from the term watersheds, manuresheds return nutrients (in the form of manure) to the same area where they were removed (via cropping).

“Manure is an excellent fertilizer, but to use it efficiently and sustainably it must be returned to the soil at the right place, during the right time, using the right techniques, and in the proper form,” she says. “When managed correctly, there are many benefits of applying manure to the land. But there are many barriers to getting this done right.”

One barrier is the varying nutrient concentrations in manure. Another is transportation; manure is mostly water and is expensive to move long distances. “And, of course, odor is not everyone’s favorite issue,” Spiegal says.

Enter the manureshed initiative. “We are working to systematically remove barriers to the recovery, reuse, and recycling of manure as fertilizer resources. A manureshed is defined as one or more animal feeding operations where manure nutrients from the operations can be recycled to meet environmental, economic, and social goals,” she says.

Manuresheds can be managed on different scales — from the farm to a neighborhood to a region, or even between regions.

It sounds simple enough, but it’s a complex issue that is drawing experts from various disciplines to identify nutrient-rich areas as well as nutrient deserts. “We need to fire on many different cylinders to try to solve this problem,” Spiegal says. “We are doing a lot of mapping to determine where the manuresheds exist, where the potential sinks are located, and how we can create a more sustainable way to manage these nutrients.”

The initiative takes loads of data, improved nutrient mapping, and extensive networks to standardize how manure is managed and address its impacts along the supply chain and in different ecosystems.

“We are working on a Manureshed Action Network, which gets stakeholders together to talk about opportunities and barriers to manureshed management, and hopefully come up with some new collective approaches,” Spiegal says. “Currently, we’re grappling with how to identify the manuresheds where nutrients could ultimately be recycled in terms of nutrient balance, because there’s such a diversity of animal feeding operations.”

Boost collaboration

The issue has no easy answers because it’s not just a simple nutrient issue. There’s also the issue of cost and connecting producers who don’t always work together to help close the nutrient cycle.

“None of us are working alone,” Spiegal says. “It’s an issue that will require better coordination as we try to develop a more sustainable agricultural system.”