Soil biology batting order

It’s a rare occurrence for agriculture and baseball to come to a crossroads in pop culture, but that is what happened in the 1989 movie “Field of Dreams.”

Although it might be a stretch of a comparison, building a baseball diamond in the middle of a cornfield isn’t completely unlike establishing a grazing system in a perennial pasture. Instead of attracting ghostly players and out-of-town spectators, though, a well-managed grazing system has potential to draw in a host of biological diversity.

Earlier this month at the Heart of America Grazing Conference in Elizabethtown, Ky., Chris Teutsch gave a nod to the iconic baseball film. “Build It and They Will Come — Managing for Soil Life,” was the title of his presentation in which “they” referred to the numerous species of microorganisms that can proliferate in pasture soils when farmers focus on regenerative principles.

It’s all relative

Before beginning his talk, Teutsch defined two goals for his presentation. The extension forage specialist with the University of Kentucky wanted to instill a deeper appreciation for soil and soil organisms among the audience and equip them with knowledge to implement better soil management on their farms.

He then stated that graziers are in the business of harvesting solar energy. In other words, milk and meat from grazing livestock are ultimately value-added products of the energy produced by plants via photosynthesis. Stewarding pastures in a way that maximizes this energy usage while ensuring the renewability of those forage resources are the keys to making a grazing enterprise a profitable one.

With that said, Teutsch acknowledged there are as many ways to define regenerative grazing as there are farmers who practice it.

“One thing that we are good at as graziers is making up new terms for the same thing,” he joked. Those terms include management-intensive grazing, controlled grazing, rotational stocking, and adaptive grazing. At the end of the day, though, Teutsch said any approach will inherently be regenerative if it is properly executed.

“The basis of regenerative grazing is not only to protect our land source, but to improve it over time,” he asserted. “We do that by building and maintaining a healthy and vigorous sod in the pasture.”

According to Teutsch, that sod — or soil — is comprised of mineral and organic solids, gases, liquids, and living organisms that serve as a medium for plant growth. He emphasized the role of organic matter as a food source for those living organisms, which run the gamut from bacteria, fungi, and protozoa to earthworms, centipedes, and beetles.

Community dynamics

Zooming in on these tiny life forms, Teutsch painted a picture for the microscopic community they create among themselves. Soil organisms are responsible for services like fixing nitrogen, facilitating nutrient cycling, building soil structure, and tunneling to enhance water infiltration. Despite their size, he referred to a study in which the belowground biomass for all types of soil organisms in a single acre of pasture was nearly 14,000 pounds. This included 2,000 pounds of bacteria.

“Think about a bacterium: A microscopic, single-cell [organism],” Teutsch prompted. “We’ve got 2,000 pounds of living bacteria in one healthy acre of grassland. That’s really incredible, and our job as graziers is to manage these organisms in a sequence of the grassland ecosystem.”

In addition to bacteria, Teutsch highlighted some of the other soil organisms that contribute to regenerative systems. Although livestock play a large part in nutrient cycling in pastures, the microorganisms and insects that are busy at work on and below the surface can have a substantial impact on soil health.

Fungi: Teutsch noted there can be more than 6,000 pounds of fungi under a healthy acre of land. These microorganisms grow in long strands called hyphae, and they decompose organic material and complex carbohydrates like cellulose and lignin. With this decomposed material, fungi can fix nutrients into fungal biomass, which is used as fuel for other organisms and reduces nutrient loss in the soil.

Vesicular arbuscular mycorrhizae are a species of fungi that form symbiotic relationships with plants by entering root cells and extending a network of hyphae into the soil. This creates a longer highway for nutrient transport, giving plants greater access to soil nutrients, especially in low-fertility environments. Teutsch added that mycorrhizae also enhance water uptake and serve as a mechanism of nitrogen transport from legumes to grasses.

Earthworms: Teutsch said earthworms can be classified according to their dwelling and feeding behavior as epigeic, and endogeic, or anecic. He explained epigeic worms stay close to the soil surface and feed on plant litter; endogeic worms create systems of horizontal, branching burrows and feed on the soil; and anecic worms dig deep in the profile and deliver organic matter and worm castings to the soil surface — a process called bioturbation.

In addition to their impact on soil aggregation, Teutsch noted earthworms’ role in nutrient cycling. “They decompose manure piles in pasture ecosystems or residue that is left on the soil surface,” he said. “As they break that down, it increases the surface area, and when we increase the surface area, other things like bacteria and fungi can start to break down the material.”

Arthropods: This group of soil organisms ranges from microscopic insects to larger bugs like ants and spiders. Arthropods are categorized as shredders, predators, herbivores, and fungal feeders, depending on what they feed on and how they decompose organic material.

“We like to think of [the soil] as a peaceful environment, but it’s not really peaceful — everything is preying on one another,” Teutsch said about predator insects. “As they prey on one another, they release those nutrients that have been sequestered in a cellular structure.”

Dung beetles also fall under the arthropod category and are further divided into tunnellers, dwellers, and rollers based on how they interact with manure in pastures. Dung beetles largely enhance nutrient cycling, reduce ammonia volatilization in manure, and move manure into the soil as a food source for other microbes. Teutsch noted some researchers have estimated these services have an economic value to pasture ecosystems that is upward of $300 million a year.