NAU Researcher Unearths the Potential of Fungus in Soil

Professor Nancy Johnson studies mycorrhizas

Professor Nancy Johnson is renowned for her work on fungi and ‘harmonious’ sustainable agriculture.

Northern Arizona University (NAU) research is helping lead the way for farmers to harness the power of soil instead of chemicals to fertilize crops. Nancy Johnson, Professor in the School of Earth Sciences and Environmental Sustainability, is renowned for her work on fungi and “harmonious” sustainable agriculture. 

Johnson has been researching mycorrhizal fungi and their symbiotic relationship with most plants for nearly 30 years. She is the director of NAU’s Soil Ecology Lab, where soil organisms' response to the environment and their effects on plant communities and ecosystem properties are studied.

Understanding symbiotic fungi 

 Mycorrhizal fungi, as a group, associate with nearly all plants on Earth. They provide plants with nutrients and water in exchange for carbohydrates, but scientists are still figuring out the environmental factors that control their distribution and function. 

Mycorrhizal fungi form web-like filaments that spread through the ground and forage for nutrients and water. The filaments are so thin they cannot be seen with the naked eye, yet they are critical to structuring soil and reducing its loss through erosion, explained Johnson.

Johnson’s research focuses on arbuscular mycorrhizas, the most ubiquitous and ancient form of the fungi that evolved concurrently with terrestrial plants more than 400 million years ago. Her work has taken Johnson to sites across the United States and to countries such as Venezuela, Tanzania, and Sweden to measure the symbiotic function of the fungi in different ecosystems.  NAU students have been directly involved in the research and reporting of Johnson’s results. 

"If we could better understand carbon dynamics in soil, we could more accurately predict how agricultural practices, for instance, affect global CO2 levels."

mycorrhizal fungi
Arbuscular mycorrhizal fungi form microscopic spores instead of mushrooms.

Harnessing mycorrhizas for conservation and restoration

 “We continue to discover more efficient and cost-effective ways to harness mycorrhizas for their benefits in sustainable agriculture and ecosystem restoration,” Johnson said. “Mycorrhizal fungi are present in most soils, so the addition of these organisms through inoculation is generally not necessary. However, a better understanding of their interactions with host plants and soil fertility will allow us to manage mycorrhizas to encourage a healthy symbiosis that benefits plants.” 

Johnson’s research also has conservation implications.  Currently, no one is certain how much carbon can be sequestered in the soil beneath grasslands. If the carbon dynamics in soil could be better understood, scientists could more accurately predict how agricultural practices, for instance, affect global CO2 levels. 

“One of the big places where carbon gets stored is below ground, in the soil," Johnson explained. "Because mycorrhizae are so abundant, they are probably a pretty important carbon sink. But we don't really understand the factors that control how much gets stored down there.” 

Contributions from “Inside NAU” and NAU Marketing