Will the coming "brown" revolution be as big as the green revolution? The challenge is that it's out of sight, out of mind. And that’s an expensive attitude. The invisible world of soil microbes beneath your feet convert sunlight, water, CO2 and crop residue into crop income, courtesy of the “most incredible zoo,” says Diana Wall, soil ecologist at Colorado State University.

They are out of our sight, but too vital to ignore.

When you apply phosphorus (P) fertilizer, for example, the P may become chemically unavailable before the plant can absorb it, and soil microbes make it available through the growing season by unlocking chemical bonds.

During floods and droughts, soil microbes are what have built soil highways for efficient transport and storage of soil moisture, gases and nutrients.

 “Soil microorganisms decay organic matter and cycle nutrients back into forms that plants can use,” says Jill Clapperton,rhizosphere (root zone) ecologist and president of Rhizoterra, Lolo, Mont.“Tiny soil animals like protozoa, amoebae, nematodes and mites feed on organic matter, fungi, bacteria and each other. Together these activities stabilize soil aggregates, build a better soil habitat and improve soil structure, tilth and productivity.”

Untilled soil has $2,600 worth of free crop nutrients in the top 6 in., says soil microbiologist Kris Nichols with the USDA-ARS Northern Great Plains Research Laboratory, Mandan, N.D.

Soil carbon is the invisible plant and microorganism fuel produced by photosynthesis that feeds the magic microbes that work for us underground. The bottom line, Nichols says, is that working with soil microorganisms improves their fuel efficiency to produce your crop. Just as you control weeds and fertilize soil to optimize field environment aboveground, you can work with soil microorganisms underground to speed their conversion of residue into plant-available forms of N, P and other key nutrients. Your crop changes sunlight to fuel (soil carbon), which builds the machine (plant material and roots) that creates crops.

The valuable link between soil carbon and your crop aresoil microorganisms. They decay organic matter and cycle nutrients back into forms that plants can use, says Clapperton.“Tiny soil animals like protozoa, amoebae, nematodes and mites feed on organic matter, fungi, bacteria and each other. Together they stabilize soil aggregates, building a better soil habitat, improving soil structure, tilth and productivity.”

Soil microbes, fed by carbon, release crop nutrients that are strongly locked to soil calcium, iron or aluminum, depending upon soil pH, Nichols says. Without microbes, vital soil nutrients like P remain present but unavailable to your crop.

Feeding this cycle by extending the growing season (with cover crops and diverse crop rotations) increases the underground fuel (carbon) for your soil microbes, which feed your crop. “By mixing plant species with different rooting depths and architecture we can fill the soil profile with roots, build soil structure (secure the foundation), and feed soil organisms a diverse and varied diet,” Clapperton says.