Fighting Farmland Pollution with Fungi

With support from the MnDRIVE Environment Initiative, doctoral candidate Laura Bender harnesses the power of soil fungi to help plants absorb pollutants.

by Kyle Wong

To ensure a healthy crop, Minnesota farmers carefully track soil health, nutrients and the quantity of water flowing through their fields. Since 2015, Minnesota’s Buffer Law also requires farmers to tend to historically overlooked land along the edge of these fields. The law mandates a 50-foot buffer along farm fields bordering public waterways, including irrigation and drainage ditches, to help reduce contamination from farm runoff. Instead of corn, soybean and other cash crops, buffer zones are full of perennial plants and trees adept at absorbing excess nutrients flowing from the fields. With financial assistance through environmental programs like the federal Conservation Reserve Program, farmers have both the mandate and the incentives to establish quality buffers. 

Like their commercial counterparts, plants in buffer zones naturally take up nutrients, but researchers like graduate student Laura Bender, hope to improve the process by focusing on fungi living beneath the soil. Soil fungi colonize the roots of buffer plants to form a symbiotic, or mutually beneficial, relationship. “These relationships help plants take up pollutants that would otherwise escape to the waterways, but soils are often degraded through decades of tillage and fertilizer application and compaction,” Bender notes. “The fungi communities that are naturally present in soil are often degraded or absent.” Supported by a 2018 MnDrive Environment seed grant, Bender works to restore those fungal communities to strengthen buffer plants and keep Minnesota waters clean. 

Bender works with several companies working with fungal amendments and measuring techniques. MycoBloom, for example, developed a fungal amendment containing a type of fungus called  arbuscular mycorrhizal (AM). AM fungi have been shown to help plants absorb nutrients more efficiently. But soil types vary across Minnesota, so Bender has worked with farmer Dave Legvold to test the amendment on the buffer zones on his farm. She collects data from his testing site each year to identify how well the amendment might work in the rest of Minnesota.

Bender collects soil and plant samples from the field site’s buffer zone and measures the level of phosphorus, one of the most common farm nutrients harmful to waterways. Alongside the buffer, she also collects dissolved groundwater. The Research Analytics Lab at the University of Minnesota processes the soil, plant and groundwater samples to calculate the phosphorus levels in each component. Bender uses the data to trace the amount of phosphorus that the buffer plants absorb and the amount that escapes to the water. “We’re measuring how the phosphorus level changes each year to see if the fungi amendment is removing it from runoff water that enters the buffer,” she says.

Phosphorus levels in the buffer are only part of the story; Bender wants to observe the interactions between the AM fungi and the buffer plants. To do so, she needs to look below the soil and analyze the mycorrhizal interactions at a microscopic level. Here, she partners with the company MycoRoots to assess how well the AM fungi colonize the roots of buffer plants. MycoRoots documents the surface area of plant roots covered by AM fungi. Bender uses the data to understand the role that mycorrhizal association plays in phosphorus uptake. Data from 2018 and 2019 revealed that plants with high root coverage from AM fungi tended to take up more phosphorus, leading to lower phosphorus levels in both the soil and groundwater. Bender will conduct more data analysis this fall before forming a conclusion. 

Ultimately, Bender hopes to guide state policy to help farmers understand the best practices for their buffers. To build awareness, Bender plans to lead an online workshop this fall to bring farmers, policymakers and industry partners together for a discussion on buffer-related issues and policies. “It’ll be related to specific topics – different fungi people have used, success or failures in certain settings, opportunities for collaboration, etc. The goal is to identify where others have used amendments and how it has worked for them.” 

With additional funding from MnDRIVE Environment and the University’s Institute on the Environment, Bender hopes to continue research and strengthen her partnerships with the community. Proper guidelines on buffer strips and fungal amendments can help Minnesota landowners establish healthy buffers that benefit them financially and help conserve the environment.

This research was supported by MnDRIVE Advancing Industry, Conserving Our Environment at the University of Minnesota.

Kyle Wong is a writing intern in the University of Minnesota Science Communications Lab, majoring in Microbiology. He can be reached at wong0511@umn.edu