With water quality guidelines compelling more farmers to act on nitrogen loss, cover crops and split nitrogen applications are becoming more common in the Midwest. But new research shows these conservation practices may not provide environmental benefits across the board.

«As researchers, we tend to look at one type of pollution at a time. Ours is one of the first studies to evaluate the nitrogen cycle more holistically. Conservation practices relating to water quality have gained a lot of attention lately, but it’s also important to know how they might affect emissions of nitrous oxide, an important greenhouse gas contributing to climate change,» says Giovani Preza-Fontes, who worked on the study as a doctoral student in the Department of Crop Sciences at U of I. Preza-Fontes is now a postdoctoral researcher at Purdue University.

As greenhouse gases go, nitrous oxide is a doozy. With a potency 298 times that of carbon dioxide, nitrous oxide is released when soil microbes metabolize nitrogen, an essential nutrient required to grow corn. When soils warm up in the spring and summer, microbes get to work on any nitrogen not taken up by crops, turning a portion into the powerful greenhouse gas.

Some farmers have moved away from the fall anhydrous application, splitting nitrogen between early spring and mid-season. Proponents say this split application is more precise, delivering the exact amount of nitrogen crops need in the moment and leaving less in the soil to be lost in drainage water. Similarly, farmers plant cover crops to take up any excess nitrogen after crops are harvested.

But how do these practices perform in terms of nitrous oxide emissions?

Preza-Fontes, along with assistant professors Laura Christianson and Cameron Pittelkow (now at UC Davis), measured nitrous oxide emissions in corn fields across three seasons. They mimicked various conservation practices, including a pre-season nitrogen application only; split nitrogen applications in spring and at the V6 or V7 corn growth stage; split nitrogen plus a cereal rye cover crop; or no added nitrogen.

Story Source:
Materials provided by University of Illinois College of Agricultural, Consumer and Environmental Sciences. Original written by Lauren Quinn. Note: Content may be edited for style and length.