Residual soil nitrogen levels may be higher than average heading into the 2026 growing season due to relatively warm winter weather, meaning some fields may need less sidedress nitrogen fertilizer than in a typical year, according to an April 30 announcement.
Iowa State University has developed a tool designed to help farmers interpret soil nitrate test results, commonly known as the late-spring nitrate test. This tool aims to reduce uncertainty about how much nitrogen fertilizer is needed, which can lower the risk of applying too little or too much.
The decision support tool uses data from 62 on-farm trials conducted with the Iowa Nitrogen Initiative between 2023 and 2025. These trials produced 136 unique measurements that estimate both the probability of yield increases from additional nitrogen and the amount of sidedress nitrogen required for economic optimum yields. The maximum corn yield used in these calculations is set at 230 bushels per acre based on trial averages.
Alex Schaffer, research agronomy lead at Iowa Soybean Association, said timing is important because late-spring tests allow for adjustments while crops are still responsive. “It’s relatively rare for farmers to measure soil nitrogen at this point in the season,” he says. “It makes a lot of sense to look and equip ourselves with the information to address some of the water quality challenges we see, while also helping farmers be as efficient and productive as they can be.”
Schaffer said that support from Iowa Soybean Association (ISA) is available for those interested in using this new tool: “We take a lot of soil samples,” he says. “We’d be happy to come out and help a farmer collect a sample or even just talk through it over the phone, explaining where to sample in a field or how to think through a strategy.”
The Iowa Department of Agriculture and Land Stewardship recognizes benefits from late-spring testing. A three-year Nitrogen Soil Sampling Project was recently announced by Secretary Mike Naig and the Iowa Nutrient Research & Education Council. According to IDALS, this free project will conduct testing for farmers upstream from Des Moines metro areas; it aims both at cutting input costs and improving water quality by refining fertilizer application rates.
“Farmers are operating in a very challenging economy with low commodity prices and high input costs, including fertilizer prices near record highs,” says Naig. “With affordability top of mind, this is the perfect time for farmers to take a closer look at their fertilizer management programs.” He added that combining field sampling with tools like N-FACT gives better data for decision-making: “This project is a win-win,” he says. “Soil sampling has the potential to save farmers money on fertilizer costs while maintaining yields and delivering water quality benefits.”
Schaffer said pairing real-time field measurements supported by INREC and IDALS with ISU’s test support offers new opportunities: “Farmers now have tools being paired with real, in-field measurements that the state is supporting farmers to take, at a time when they can still manage nitrogen,” Schaffer says.
The Iowa Soybean Association uses checkoff funds to support programs aimed at increasing demand, conducting research and providing information directly relevant for nearly 37,000 soybean producers across Iowa according to its official website. The association also promotes community engagement through initiatives such as CommonGround Iowa as outlined online, presents annual leadership awards recognizing exceptional contributions as noted on its site, serves as Iowa’s Qualified State Soybean Board according to official sources, and works toward enhancing soybean demand via market development efforts alongside policy advocacy according to its website.
