Corn farmers need more fertilizer annually

Corn farmers in the U.S. Midwest have needed to increase nitrogen fertilizer application by 1,2 percent annually over the past three decades to maximize profitability, according to a study by Iowa State University (ISU).

The trend, linked to nitrogen loss in wetter springs and rising yield targets, challenges the previous assumption that optimal fertilizer rates remain static over time.

Analyzing data from experiments at ISU and the University of Illinois between 1991 and 2021, the researchers found that optimal nitrogen rates rose in parallel with corn yields, which also grew by 1,2 percent per year.

“It’s like a bank account: If you withdraw more, you have to deposit more,” explained co-author Michael Castellano, a professor of agronomy.

The results confirm reports from Iowa farmers, who were already reporting increased fertilizer use.

efficiency gains

Although nitrogen use has increased, practices such as crop rotation, improved drainage, and spring application have improved efficiency.

Today, growers are seeking to apply 0,7 pounds of nitrogen per bushel (a measure of volume), up from 1,2 pounds per bushel 30 years ago.

Matthew Helmers of ISU highlighted that tools such as the recently launched N-FACT (Nitrogen Fertilizer Application Advisory Tool) offer specific recommendations for each area, balancing profitability and sustainability.

More information can be found at doi.org/10.1038/s41467-024-55314-7