The Bison Underground Method

What It Is & How it Works?

Most soils humans interact with are totally broken. They are eroded, compacted, low in organic matter, and missing the biological systems that make soil function. The Bison Underground Method rebuilds healthy functioning soils faster than any other method by leveraging and accelerating the natural systems that built soils over thousands of years. I'm Dr. Steve Adams, geologist, gardener, and founder of Bison Underground. I've spent the last few years obsessed with one problem: most soil, whether it's a backyard lawn, a garden bed, or a farm field, is in worse shape than it was 500 or 1000 years ago. 

What the method is

We use tools or machines (depending on the project scale) to punch narrow vertical holes into the soil, about 2 to 3 inches across and anywhere from 6 inches to 2 feet deep depending on the tool and how compacted the ground is. Then we fill those holes with organic matter, usually compost or alfalfa pellets, but site specific or goal specific blends are possible.

That's the whole method. The reason it works comes down to what soil actually is, how it forms and matures, and what's gone wrong with most of it. Despite being simple to explain, the method is difficult to implement at scale and speed. Nature does this via burrowing animals and other processes over hundreds to thousands of years. We do it in days. 

What soil is, briefly

Soil is a mix of broken-down rock and mineral particles, decayed organic matter, water, air, and living organisms, mixed and layered together and constantly changing. It forms from rock that's already been weathered and broken down into loose material, either in place or transported by glaciers, rivers, or wind. Soil thickness can range from a few inches to over 30 feet in the deepest tropical soils. Over time, physical, chemical, and biological processes work that material over and transform it into something that can support plant life. 

Among the influences that drive this transformation, three matter most: temperature, water, and oxygen. More of each usually means faster soil development, up to a point, but these three regulate the chemical and biological processes doing the actual work. Too hot, too cold, too dry, or compacted soil that blocks air and water movement all stall soil building and are hostile to life. One of the most important products of soil formation is aggregates, clumps of mineral and organic particles bound together by a glue. Aggregates create the pore space that lets air, water, and roots move through soil and protect organic matter. They form as roots, worms, fungi, and microbes utilize organic matter in the soil, and as that organic matter breaks down into humus or other biological excretions, it acts as a glue, binding mineral particles into stable clumps and giving healthy soil its loose, crumbly texture. 

Given enough time and favorable climate conditions, raw parent material is transformed into productive soil. But most of us aren't trying to build soil from scratch. We're working with soil that already went through this process once and then got degraded. This is an important distinction, because it changes what "fixing it" means. We don’t need to redo 1000 years of geological processes. We're restoring something that already existed and still has much of what it needs, just buried, compacted, plowed, and often prevented from healing, because the plants and organisms that once occupied the landscape and soil are gone or significantly diminished.

What damages soil

Three things destroy healthy soil:

  • Erosion — wind and water carrying soil away, worse when there's no vegetation or roots holding it in place. The U.S. loses over 4 tons of topsoil per acre per year on average (USDA NRCS). The Dust Bowl stripped an average of 5 inches of topsoil from more than 10 million acres in the 1930s. A 2021 study found that 35% or more of the cultivated U.S. Corn Belt has lost its topsoil layer entirely, down to the subsoil beneath it.
  • Loss of organic matter — decomposition returns carbon to the atmosphere faster than it's replaced, especially when soil is tilled or plowed and organic matter gets exposed to heat and oxygen. Midwest agricultural soils commonly lost 50% of their organic matter within the first 40 years after being put into cultivation, and urban and suburban soils, stripped, graded, and compacted during construction, are often worse off than that. Organic matter is more abundant closer to the surface, so erosion contributes significantly to organic matter loss as well. 
  • Compaction — heavy equipment, foot traffic, or plowing crush and collapse the pore space that water, air, and roots need to move through soil. Compaction often forms as a distinct hard layer several inches down, sometimes called a hardpan. Compaction and compaction layers are hard to reverse, and is the major limiting factor to soils healing. Compacted soil reduces the ability for water, air, and life to reestablish. 

Compacted soil severely limits the ability of a soil to soak in water, so it floods and runs off instead, taking fertilizer (money) and pesticides (toxic) with it into streams and waterways, where aquatic environments are harmed. And in most damaged soils, the plants, insects, and organisms that would normally help rebuild the soil are gone too, often actively suppressed by chemical inputs.

What people already do, and where it stops working

Most regenerative practices focus on the surface: compost topdressing, mulching, cover cropping, broadforking (using long curved tines to loosen and crack the top foot of soil). All of these genuinely help. The problem is speed and depth.

Compost on the surface is exposed to sun and rain, and most of it decomposes back into the atmosphere before it ever reaches plant roots, which is why people truck in fresh loads every year. Tilling it in just brings older, already-decomposing material back up while tearing apart existing soil structure and biology. Broadforking and aerating open up cracks or small holes, but they're narrow, shallow, or short-lived, and there's no practical way to get organic matter down into them before they close back up.

Cover cropping reduces erosion by keeping plants and roots in the soil after the growing season has ended, and these plants do contribute carbon back to the soil. These approaches just can't get an abundance of organic matter deep enough, and fast enough, to fix soil that's already badly compacted, though all of these practices should be used consistently. The Bison Underground Method isn’t a replacement for cover cropping or adding surface mulch and compost. The method works with these practices, and accelerates soil restoration. An option of our method is to grow a biomass cover crop and at termination, cut the top 2/3rds, mulch and pelletize it, then inject it directly where it was grown, or in nearby soil. 

Why the Bison Underground Method works

Each filled hole becomes a column, reaching down from the surface, that acts as a node or restoration island, ready to bridge out toward other nodes. A small zone where water, air, and organic matter are all available at once, at the depth where the problem exists and where we want to rebuild structure.

Three things happen inside each column:

  1. Water infiltration. Rain hits the surface, finds the hole, and moves straight down instead of running off. Organic matter absorbs water like a sponge, and retains it for use in times of drought. 
  2. Habitat. Worms, fungi, and microbes move in and start colonizing the organic matter, and the surrounding soil. If using an inoculant or compost tea, the success of establishing organisms is almost certain because they have a habitat to establish (compared to dry compacted low carbon soil where they will likely die).
  3. A path for roots. Roots follow the hole down to cooler, moister soil, then spread outward, carrying the restoration zone with them.

This is the same process nature already uses. It's called bioturbation: animals, insects, and worms dig burrows and fill them with organic matter (leaf litter, dung, dead roots). Bioturbation used to happen everywhere, giant earthworm tunnels, badger dens, prairie dogs, but most yards and farms have lost the wildlife that used to do this work for free. Now we're doing it on ourselves, on a schedule, with tools designed for soil too compacted for any animal or machine to easily get into.

Putting organic matter underground also protects it. At the surface, compost bakes and decomposes quickly in the sun and washes away in heavy rain. Buried a few inches down, it stays moist, cool, and lasts long enough for soil organisms to actually use it.

This isn't a one-time fix. One treatment gets you gains that would otherwise take years to develop on their own. Treat the same ground again next season (maybe with a longer tine) and the gains compound. A few seasons in, you've restored ground that would have taken a decade or more to recover naturally.