The Little Guys of Regenerative Agriculture

Many of us loved making mud pies as kids—it may have been our favorite thing to do outside. But as kids, we likely never thought much about whether or not the soil that made those pies was healthy or if it could be used to grow a garden. We had no idea that healthy dirt was a “thing,” but most of us were not then—and are not now— farmers!

Regenerative agriculture consists of farming practices that enhance the health of agricultural soil—the soil that grows crops in our food system. Soil composition and health can be altered by environmental stressors including harsh climate conditions, physical disturbances and chemical contaminants. But the overall health of soil depends largely on its carbon concentration. The element carbon is a building block of all animal and plant cells and is ubiquitous in our environment. Because carbon is a primary component of agricultural soil, careful carbon management is one of the most important aspects of growing sustainable plants in our food system.

Our last regenerative ag post talked about practices that many farms are utilizing to support carbon management, including no-till farming; composting unused, biodegradable plant products; and planting perennial crops. Now let’s take a deeper dive into our agricultural soil and look at the “little guys”—including worms, bacteria, and viruses—that support carbon sequestration and soil health. As we’ll see, these tiny helpers work right alongside farmers to bring us healthy and renewable crops each year.

Down to Earth

There’s more to soil than just dirt. Soil contains an ecosystem that is abundant in various types of animals, food sources, nutrients and waste. All the elements in the soil ecosystem, both living and nonliving, work to create an ecological balance. And one major balance-keeper is earthworms. Many of us remember digging up these little guys as a kid or even dissecting them in school (those poor worms!), but you’re less likely to know that by studying the variety of species of these worms we can directly assess the healthfulness of soils.

As earthworms feed on organic matter and mineral particles in soil, they have a positive impact on their soil environment. As they eat, they promote beneficial bacteria growth and move deposits of soil from one layer of the ground to another. This bite-sized “tilling” helps move nutrients from lower levels in the soil to higher ones, and vice versa. Earthworms also produce burrows in the soil that aid in soil porosity, create channels for root growth, and increase soil’s water-holding capacity.

Recently, researcher Jacqueline L. Stroud published a journal article that found earthworms to be “primary candidates for national soil health monitoring” and noted positive outcomes in training and supporting farmers to conduct earthworm identification and gauge their impact on farmland soils. Soils that were found to have smaller earthworm populations and less diversity within the earthworms present were less productive and at risk of being overworked. Most participating farmers (57 percent) noted that they would use their worm survey results to change their soil management practices.

Good news about good bacteria

Healthy soil is chock full of beneficial bacteria. Like earthworms, bacteria are a part of the soil ecosystem and aid in soil water dispersal, nutrient cycling, and plant disease suppression. Typically, we are taught to avoid bacteria, but in the case of soil, we say, “bring them on!” The United States Department of Agriculture (USDA) has noted that a teaspoon of productive soil generally contains between 100 million and one billion bacteria. Bacteria display varied activity in soil and are grouped into four categories: decomposers (which convert plant matter into forms of food for other living organisms in the soil); mutualists (which become partners with plants and convert atmospheric nitrogen (N2) into nitrogen for plants); pathogens (which can cause disease in plants but can facilitate helpful antibiotic production in soil); and lithotrophs or chemoautotrophs (which obtain energy from compounds of nitrogen, sulfur, iron or hydrogen instead of from plants or other organic matter).

While we know that bacteria in soil are plentiful, the precise counting and identification of soil microbes is a tough task—fewer than five percent of microbes can be isolated and cultured using conventional techniques. Luckily, researchers have uncovered a new molecular fingerprinting technology called metagenomics. This genetic sequencing technique still comes with some difficulties, but it allows microbes to be studied in their natural habitat and gives one of the most in-depth analyses of the full gamut of soil microbes present for any tested area. Scientists can take a soil sample and sequence all its present DNA, which may come from hundreds or thousands of different microbes.

Now you’re getting smaller

Just when you thought bacteria were the smallest helpers in the soil, we’re ready to spring viruses on you! The viruses associated with soil actually infect the soil bacteria. Little information is known about the impact of these viruses (phages) on the soil microbial community, and it’s tough to know more due to variation in soil ecosystems and limitations in conventional screening tools, but these look to be “good viruses” that provide yet another level of carbon management within the soil.

Recently, a research team at Cold Spring Harbor Laboratory published a first attempt to map the global “soil virome” (soil viral community). The team examined more than 24,000 different soil viral genome sequences and mapped their relationship with living organisms in the soil. Other researchers agree with this scientific team, and there look to be many more exciting soil studies on the horizon.

Soil health is a very complex part of successful farming. As food producers aim to enhance their regenerative ag practices, there are many avenues to travel to see positive outcomes. Many of us would not have thought worms, bacteria and viruses and bugs to be a part of the equation, but it’s exciting to see what advanced soil research is uncovering and how these “little helpers” are busy at work.