Primary Investigator: Chris Lenhart
Co-Investigators: Laura Bender (Graduate Scholar); Kirsten Haus (Northstar STEM Alliance Researcher), Alli Graper (undergraduate honors thesis)
Industry Partners: Legvold Farms; Agricultural Drainage Management Coalition
Award Type: Seed Grant – Graduate Research Scholar

ProblemStreambank vegetative buffers (also known as riparian strips) are required by Minnesota State Law to be maintained along all waterways, to filter out sediment and nutrients such as nitrogen and phosphorus. While riparian buffers effectively remove particulate phosphorus, they don’t do as well removing dissolved phosphorus. Soil fungi within buffer strips can also contribute to removal of dissolved phosphorus by enhancing plant uptake as most native grasses have symbiotic relationships with mycorrhizal fungi to uptake nutrients.  Fungal communities are greatly impacted by decades of farm tillage so when buffers are installed the microbial community is not optimized for phosphorus uptake, nor for native plant establishment, which are both key to buffer function.. Therefore, removal of dissolved phosphorus from buffers and edge-of-field practices to prevent transport into water bodies remains a challenge. 

SolutionThe removal of soluble phosphorus in riparian buffers may be improved by enhancing the symbiotic relationship between plant roots and fungal communities. To test this, Lenhart and Bender have compared multiple riparian vegetative plots – one with and one without mycorrhizal fungi added and with different types of native grass species – within a riparian buffer along a stream in Minnesota. Phosphorus levels in the plants, soil, and water within each plot have been measured and analyzed over the 2019-2020 period to determine whether addition of mycorrhizal fungal to riparian buffers plots improves phosphorus uptake and removal from tile drainage flow routed through the buffer. Additionally, this in situ work is being compared to controlled environment studies being conducted using 100 gallon tanks on the St. Paul campus. 

Impact: Improving the removal of dissolved phosphorus in vegetative buffers would help achieve Minnesota’s State Nutrient Reduction Strategy goals. These goals aim to preserve water ecosystem health by lowering excess nutrient levels that can cause eutrophication and algal blooms. Buffers in sandy, compacted or degraded soils are most likely to benefit from fungal amendments.  Findings from the studies are being

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