In the Gulf of Mexico, a “dead zone” forms every summer. According to Farm and Dairy, plumes of oxygen-robbing algae, fed by excess nitrogen coming in from the Mississippi River, kill off marine life and threaten the livelihoods of those who fish the Gulf.
“It might not sound like much, given that agricultural drainage only represents a portion of the nitrogen getting into the Mississippi. But 5 to 10 percent is pretty good for an inexpensive, passive system that farmers can put in and forget about,” said Reid Christianson, research assistant professor in the Department of Crop Sciences at U of I and co-author of the study, according to Farm and Dairy.
According to Farm and Dairy, saturated buffers are vegetated strips of land– as little as 30 ft across –between tile-drained fields and waterways. Tile pipes carrying drainage water from the fields usually empty directly into ditches or streams.
“Saturated buffers don’t take a lot of land out of production, and are fairly inexpensive at $3,000 to $4,000 to treat drainage from a field-sized area. Farmers have to be willing to not farm right up to the creek, but in terms of edge-of-field conservation practices, I think saturated buffers fit easily with farming and provide additional benefits like wildlife and pollinator habitat,” said Laura Christianson, assistant professor also in the crop sciences department and co-author of the study.
With other studies showing average nitrogen removal rates between 23 and 44%, this number of saturated buffers would reduce the total nitrogen load in agricultural drainage by 5 to 10%, according to the study.
Laura said the approach required a lot of assumptions. There are no satellite images or maps for tile drainage systems across the Midwest, so the researchers made the assumption that corn or soybeans fields on soil characterized as “poorly drained” were most likely tiled.
“Overall, our assumptions were relatively conservative. We probably underestimated our figures as a result,” Reid said, according to Farm and Dairy.