URBANA, Ill. – Midwestern agriculture contributes the vast majority of nitrogen in the Gulf of Mexico, causing an oxygen-starved hypoxic zone and challenging coastal economies. State and federal policies have tried for decades to provide solutions and incentives, but the hypoxic zone keeps coming back. A recent study from the University of Illinois offers a new way to understand Midwestern nitrogen dynamics and forecasts future nitrogen loads under various management scenarios across the region. 

“Our model explains what's going on across 83 watersheds in the Midwest, providing a quantitative understanding of why certain watersheds differ in terms of nutrient loss. But the most important contribution is our scenario prediction, which hasn’t been done before. If you increase tile drainage or the corn fraction, how much does the nitrogen load change? We can predict that, and I think that is really exciting,” says Kaiyu Guan, associate professor in Department of Natural Resources and Environmental Sciences (NRES), founding director of the Agroecosystem Sustainability Center (ASC), and senior author on the study.

Guan says a more detailed understanding of nitrogen and water flow dynamics, as well as the ability to forecast the impact of management changes, is a critical step in developing effective policies for nutrient loss reduction from field to watershed scales. 

The research team analyzed the relationship between daily flow rate and nitrate concentration across 83 Midwestern watersheds, finding a universal pattern throughout the region: nitrate increases with flow before leveling off at a high flow threshold.

The study, “Agricultural nitrate export patterns shaped by crop rotation and tile drainage,” is published in Water Research [DOI: 10.1016/j.watres.2022.119468].

Read the full release from College of ACES.