Glomalin is a belowground sticky gum holding onto your most valuable soil resource: carbon. “The more glomalin in a soil, the more efficient and healthier that soil probably is,” says Kris Nichols, soil microbiologist, USDA-ARS Northern Great Plains Research Lab, Mandan, N.D.

“Glomalin’s stickiness creates soil aggregates (or pellets or clods), so vital to soil nutrient exchange and water movement. The pore space between aggregates is key to exchanging, storing and transporting carbon, water and gases. They reduce ponding and run-off after heavy rains, and exchange gases between the soil and the surface to support plant roots’ growth and respiration. Without these underground highways created by soil aggregates, crops require more commercial fertilizer to produce the same yields,” Nichols says.

“Glomalin stabilizes soil clods by coating them with a waxy substance to keep water from flowing rapidly into the soil clod and washing away everything,” Nichols says. “This slows down the rate of water entering an aggregate, keeping it more stable.

“Think of soil aggregates also as a soil carbon vault. The vault slows carbon decomposition, similar to time-release fertilizer pellets. This creates a steady level of N and P release through the growing season where the roots can use them, rather than a more rapid release, where they can be quickly lost to wet spring conditions. Glomalin stores carbon in aggregates where only slow-acting microbes live, storing carbon like a slow-release fertilizer to fuel plants and roots.”

Glomalin’s presence in soil reflects soil health. Nichols correlates glomalin levels with less tillage, more diverse crops and longer-season crops. Diversity above ground correlates with diverse carbon forms below ground, available to feed the millions of microorganisms improving your crops’ efficiency, Nichols says.

This wonder substance, glomalin, is produced in and around plant roots by beneficial fungi, fueled by carbon. These arbuscular mycorrhizal fungi have tiny hair-like threads called hyphae that extend roots’ reach, delivering more soil nutrients to plants in return for carbon that came from decomposed surface residue and photosynthesis.

These finely branched, tiny root threads are the workhorse of nutrient procurement and delivery to your crops. Till your soil and you damage this root network, reducing their productivity. As someone raised on a corn-soybean farm in southwestern Minnesota, Nichols knows this concept can be a hard sell. “Tillage also ruptures soil aggregates, clogging soil avenues for nutrient, water and gas exchange,” she says.

Besides producing glomalin, these same arbuscular mycorrhizal fungi work with beneficial soil bacteria to release chemical bonds that prevent soil P from being available to your crops. By breaking these chemical bonds, the AMF literally free more P and other nutrients.

Read more about ways to test the health of your soil from NRCS.