A new, no-cost Nitrogen Soil Sampling Project aims to help Iowa farmers dial in their fertilizer application rates, potentially helping them cut input costs while delivering meaningful water quality benefits in key watersheds.

The three-year pilot project sponsored by the Iowa Department of Agriculture and Land Stewardship (IDALS) and Iowa Nutrient Research and Education Council (INREC) will conduct nitrogen soil testing for farmers in targeted areas upstream from the Des Moines metropolitan area.

“Farmers are operating in a very challenging economy with low commodity prices and high input costs, including fertilizer prices near record highs,” said Iowa Agriculture Secretary Mike Naig. “With affordability top of mind, this is the perfect time for farmers to take a closer look at their fertilizer management programs.

“This project is a win-win; soil sampling has the potential to save farmers money on fertilizer costs while maintaining yields and de­­livering water quality benefits.”

studying variability
The project will study year-to-year variability in nitrogen availability and evaluate how residual soil nitrogen influences on-farm nitrogen management decisions.

The first phase of the project begins this spring.

INREC is currently enrolling farmers directly north of the Des Moines metro in Boone, Calhoun, Greene, Hamilton and Webster counties. Farmers can start en­­rolling now at iowanrec.org/nitrogen-soil-sampling-project.

“Nitrogen decisions involve many variables,” said Ben Gleason, INREC executive director. “This program gives farmers the chance to work off real numbers from their own fields. In a year where every input dollar matters, that kind of precision can make a difference.”

Residual nitrogen levels can vary widely from year-to-year and field-to-field, with winter conditions often influencing how much is available heading into spring.

Iowa State University researchers have been modeling soil nitrogen conditions this winter, finding residual nitrogen levels higher than average in some regions because of the relatively warm winter weather.

removing the guesswork
Shawn Richmond, Iowa Farm Bureau’s conservation and natural resources policy advisor, said taking soil samples this spring will remove the guesswork from nitrogen application decisions and give farmers reliable, field-level data to understand how much nitrogen is naturally occurring in their fields before applying additional fertilizer.

“I like to think about it as checking the tank; let’s see what’s there,” he said. “Especially at these tough times when margins are razor thin, it’s important to employ as many tools as we can to help us better manage those fertility levels.”

Coupled with the Iowa Nitrogen Initiative’s N-FACT tool, an advanced cropping systems model that forecasts a range of optimal N fertilizer rates based on specific field conditions, Richmond said targeted soil sampling can help farmers fine-tune their fertilizer applications.

“Soil sampling is one of the most important tools we have to balance productivity and environmental protection,” he said. “Not every field is the same. We see a wide range in the economic optimum rates for fertility. Having real-world information allows farmers to use only what they need, which reduces nutrient loss into streams while maintaining strong yields.”

Farmers could potentially use the data to make variable rate nitrogen applications across the field based on soil sample results, said Richmond.

“Variable rate nitrogen application is trending up, and I think it’s likely to continue to do so, especially given some of the cost pressures we’re up against,” he said.

expanding this fall
The IDALS and INREC soil sampling project will expand this fall to include more fields in the Boone, Des Moines, Middle Cedar and Raccoon River watersheds. SoilView will conduct the soil sampling and laboratory testing to inform in-season nitrogen applications.

Participating farmers will be asked to provide basic field information such as crop rotation, nitrogen management, manure use and cover crop history, and complete a short, postseason survey. All data will be anonymized and shared with Iowa State University to support ongoing nitrogen research and the Iowa Nitrogen Initiative’s N-FACT rate recommendations.

To learn more about the Nitrogen Soil Sampling Project, visit iowanrec.org/nitrogen-soil-sampling-project.