Living soil ecosystems add carbon to soils, enabling crop production

Typically, soil mapping shows many Wyoming soils have one percent organic matter or less, says University of Wyoming (UW) Extension Educator Caitlyn Youngquist, who noted that soils across the state are generally very fragile.

While there is a range of soil types across the state, from high mountain lands to deserts and upland plains, several keys are important to maintaining healthy soils, particularly in cropland across the state. 

Carbon cycling

Youngquist explains, “The entire soil system is driven by carbon dioxide and carbon through photosynthesis.” 

With the goal of getting carbon into soils, Youngquist describes carbon dioxide from the atmosphere goes through the process of photosynthesis, where it enters the soil after being processed by the plant.

“Animals also eat the plant,” she continues. “The carbon cycles through the animal and back to the soil in manure.” 

Carbon is lost from systems through erosion. 

“When the wind blows soil into our neighbor’s fields, we’re also sending them a lot of carbon, which is like gold,” Youngquist says.

Crop harvest also removes carbon from the system. 

Additionally, root respiration and organic matter loss can result when soil is tilled, further depleting the carbon in the system. 

“When we think about a healthy soil system, the entire system is driven by organic carbon in the soil because that’s what the soil microbial community eats,” Youngquist says. “Carbon drives the entire food chain under the soil.” 

“We gain carbon into the system – our main goal – through photosynthesis,” Youngquist says, adding carbon comes from living roots, cover crops and through adding carbon in the form of manure and mulch. “We lose carbon through bare soil and erosion, crop harvest and tillage.” 

Fungi

The piece that is missing in carbon cycling, however, is mycorrhizal fungi. 

“Mycorrhizal fungi form amazing associations with plant roots,” Youngquist describes. “The plants feed them carbon in the form of sugars, and then the mycorrhizae go out into the soil and pick up water and nutrients that are hard for plants to get.” 

In many soils in the Big Horn Basin, iron and phosphorus are largely unavailable, so when associations are built with mycorrhizal fungi, the ability of plants to reach and uptake water and nutrients increases by 10 to 100 times, she says. 

“Eight to 90 percent of plants form these mycorrhizal associations,” Youngquist continues. “Sugarbeets do not, and brassicas do not. Most crops do, however.” 

In addition, the fungi produce large quantities of soil carbon and serve to hold soils together, which also helps to reduce erosion. 

“They form glues – called glomalin – and glue little pieces of soil together,” she adds, noting the fungi sit on root hairs of the plants. “They are fascinating organisms.”  

Bacteria

“We also have billions of bacteria in the soil,” says Youngquist. “Very few of them cause disease. Most of them are little soluble bags of fertilizer floating around.”

She continues, “When they die, they pop open and feed plants.”
Bacteria also decompose things in the soil, including dead plants, roots, manure and more. 

Nitrogen fixing bacteria are also important for the soil, particularly for legumes.

Other living creatures 

“We also have nematodes in the soil,” Youngquist says. “A few nematodes cause disease, but most of them do not. They are veracious predators and eat a lot of bacteria and fungi.” 

Microarthropods eat dead bacteria and dead nematodes, then die and are consumed by bacteria.

Earthworms also contribute to the soil environment, stirring up the system and digesting organic matter. 

“Earthworms are a good indication of a healthy system,” Youngquist says.

“There’s a whole food chain that goes on in the soil,” Youngquist comments. “It’s an aggressive food chain, and there’s a feeding frenzy always going on in our soil.” 

Youngquist presented during 2019’s WESTI Ag Days, held Feb. 12-13 in Worland. 

Saige Albert is managing editor of the Wyoming Livestock Roundup. Send comments on this article to roundup@wylr.net.