Timothy Robb peers into a microscope to reveal the underground realm of the living and dying within a fistful of soil. On the glass slide, he sees clumps of golden-brown minerals and organic matter particles, like pebbled splotches of ink. Nearly everything else in the landscape is a microbe, a motley crew of roving shapes, preparing to eat or be eaten. Hairy orbs of protozoa glide around in search of snacks in the flecks of bacteria scattered all around. A nematode, a microscopic worm, thrashes through the scene in a hurry. A tubular strand of fungi stands still, perhaps absorbing the dust of dead plants.
 

“This is called shadow microscopy,” says Robb, the co-owner of Compostella Farm in southern Mississippi, bringing the microorganisms into focus. It’s a way of viewing living specimens under an oblique light, so they appear backlit and magnified, like a shadow box theater. Just prior to this, he diluted the sample in water and shook it, like a “hurricane or earthquake, any biblical catastrophe motion for that soil.” This broke apart the soil’s structure so he could see everything holding it together, like the dark brown curl of fungi.

 

“This is what a really good, healthy fungi strand looks like,” he says. Its uniform, segmented structure, thickness, and color are often good signs, though he adds that it’s not a hard and fast rule, just clues that this might be an architect of healthy soil.
 

As a vegetable farmer, Robb is mostly in the business of life. But his interest in building healthy soil led him down into this shadowy world of decay, where microbes shuffle carbon and nutrients in an endless cycle that sustains all life on Earth. This world appears chaotic at first glance, but Robb insists that it is elegant. An orderly marketplace, really. He’s been working to understand and strengthen this underground economy to replenish his soil.
 

Researchers have increasingly recognized how essential fungi are to sequestering carbon in the soil and some have come to appreciate the outsized role they play in supporting crop health, mitigating climate change, and even sheltering crops from disease. As fungi’s vast benefits come to light, more farmers are tapping into this vital network, learning how to work with beneficial fungi to encourage its growth in the soil, swapping tilling for microscopes.
 

This growing interest in fungal networks on farms quietly challenges the underpinnings of U.S. agriculture. The prevailing model involves taking care of the crop’s nutritional needs with chemicals, bumping up the nitrogen, phosphorus, and potassium in an effort to maximize the yield of the crop. Farm ecosystems are controlled with herbicides that kill weeds and fungicides that kill the fungi in the soil. Common practices, like tilling the soil, disturb the fungal networks and then deepen the dependence on chemical inputs.

 

“We’re reliant on these cheap inputs that are no longer cheap,” says soil ecologist Adam Cobb, whose research focuses on mycorrhizal fungi. He notes that farmers are then subject to the whims of a global market, which tends to skyrocket in price during geopolitical conflicts.

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