"I could never figure out what the sky was thinking, but the soil, she don't keep too many secrets." Those are some of the few words of Doc Platter, an elderly Montana rancher in the television series, "King of the Hill." I apologize for the pop culture reference, but Doc's words may have had more wisdom than most of the show's viewers probably realized.
There's a reason cover crop gurus like Steve Groff encourage farmers to keep a shovel handy. Dig around in soil that's been no-tilled or had cover crops for several years, and you'll likely find what Doc, perhaps inadvertently, was referring to – soil microbes and earthworms, what could be referred to as the herd below ground, as well as root systems and residue, what feeds this "micro herd."
On a recent trip back to southwest Iowa, this was easy to see even on a field that, just four years ago, was being tilled. Digging just a few inches through residue and soil, it didn't take long to find earthworms – a key indicator of soil health.
The dirt underneath
It's part of what Odette Menard, Soil Conservation Hall of Famer from Saint-Hyacinthe, Quebec, would refer to as looking at soil health as a 3D solution – or looking at what happens beneath the surface. While it's easy to focus on the residue left on the surface with no-till, this residue is also necessary to feed the earthworms below.
So, what's the proper stocking rate for this micro herd? You can never have enough, but about 25 worms per square foot or one ton per acre is the ideal amount. As worms eat residue, they also eat soil and bacteria to break down residue as it passes through their digestive systems. The final product is high quality soil. With enough food available, the plow layer of the soil profile will go through an earthworm's digestive tube in five years, according to Menard.
This 3D solution includes soil microbes, which are fed by living roots in the soil. Roots feed mycorrhizal fungi, which secrete a natural adhesive called glomalin, which holds the soil together, improving aggregate stability and water infiltration. When the roots are disrupted with tillage, the fungi are less effective.
It isn't always easy to see what's at work beneath the soil – it's easier to simply focus on residue for erosion control, what Menard refers to as a 2D solution. Looking at the big picture means digging deeper, and as soil health experts often advise, keeping a shovel handy.