Corn farmers are paying a half billion dollars each year to keep up with soil deterioration. A new study out of the University of Colorado (CU) says that nationwide, producers are having to use a third of their fertilizer costs just to keep up with the problem.

Over the past several years, soil deterioration has become one of the largest issues facing agriculture. Long-term soil fertility has been on the decline in agricultural lands around the globe due to salinization, acidification, erosion and the loss of critical nutrients in the soil such as nitrogen and phosphorus. According to Iowa State University, the problem has become so troublesome that land can no longer be cultivated in some areas of the nation and is being abandoned. The impact of soil erosion on water quality can become significant, particularly as soil surface runoff.

Published in Earth’s Future, the report revealed that a third of the fertilizer applied to grow corn in the United States each year is simply compensating for the ongoing loss of soil fertility. Corn farmers generally offset these losses with nitrogen and phosphorus fertilizers, which are also intended to boost yields.

“We know there’s land degradation going on even in U.S. modern agriculture, but it’s really difficult to pin down how much and what impact it has,” said Jason Neff, corresponding author on the paper and director of the Sustainability Innovation Lab at Colorado. “These findings provide more information to farmers so they can make decisions that benefit them economically, but also support a more sustainable form of high-yield agriculture.”

America is one of the most productive corn growing nations, producing more than 4.46 tons per acre farmed. According to the USDA, the nation’s farms produced in excess of 366 million metric tons of corn which generated $14.5 billion in revenue in the 2018-19 season alone. Not coincidentally, the United States is also one of the world’s largest users of fertilizer, applying more nitrogen and phosphorus per acre than its high-yield agricultural counterparts in the European Union.

In the study, the CU group used four scenarios in the Environmental Policy Integrated Climate (EPIC) model, a widely used agronomic model used to estimate crop growth and how crop growth responds to variables like fertilizer, irrigation and climate. Using EPIC, the researchers compared how using no fertilizer or irrigation differed from using only one or the other, or both. Irrigation was an important component of the analyses because while it can increase yields, it also increases erosion and fertilizer runoff.

By separating the impacts of fertilizer and irrigation, they were able to see that in different regions of the country, some aspects were more important than the others for agricultural success. For example, in California, producers needed to add more water. In Ohio, fertilizer additions were more important than irrigation. However, across the country as a whole, the group found that it took one third of fertilizer presently added to cornfields to simply break even, bringing soil fertility back to pre-farmed levels.

“Farmers do what makes sense to grow crops,” Neff said. “When you’re not able to see the cumulative effects of degradation, you have to add fertilizers but you’re not going to know what the financial impact of that underlying degradation is.”

Introducing environmental effects, such as damage to freshwater and marine life, along with the money spent by farmers on chemicals, Neff said that the costs go from billions to more than a trillion dollars every year.

Growing practices like regenerative agriculture, which restore soil fertility on lands actively being farmed, will also reduce the costs and environmental impacts of fertilizer use. Healthier, more fertile soils can also capture more carbon, hold more water and keep excess nutrients from running off into ecosystems that don’t have the ability to handle them.

Neff said that producers can also reduce how often they till their fields, add and increase erosion control measures, as well as use more organic fertilizers like compost. These can actually help reduce the amount of inorganic fertilizers – nitrogen and phosphorus – needed in the soil.

“If you can drop the fertilization while maintaining the yields that we need and the economic outcomes that farmers want, then why not, right? That’s a win-win...My hope is that this information supports national and international efforts to build back soil fertility.”