By Scout Nelson
A recent study from the University of Minnesota is helping corn growers make more accurate nitrogen application decisions with an enhanced soil testing method. This research improves the well-known Pre-Sidedress Nitrate Test (PSNT), offering better guidance during unpredictable spring weather.
The PSNT measures nitrate levels in soil when corn plants have four to six leaves. The updated research shows that 20 parts per million (ppm) of nitrate in the top 12 inches of soil provides 97% of maximum corn yield.
The study analyzed 34 field trials across Minnesota, covering diverse soil types, weather conditions, and cropping systems. Results show spring rainfall has a strong impact on PSNT values. In dry years, the threshold rises to 21.5 ppm, while in wet years, it drops to 17.4 ppm.
If nitrate levels fall below 20 ppm, approximately 12.3 pounds of nitrogen per acre are needed for every ppm shortfall. This allows for precise adjustments based on real-time field conditions.
“Nitrogen decisions are always a moving target, especially when spring weather doesn’t cooperate. The PSNT gives farmers a way to read the field’s nitrogen status in real time, rather than guessing, and allows us to adjust quickly when the soil is coming up short,” said lead author Emerson Souza.
Researchers recommend using 20 ppm as a general statewide threshold but encourage ongoing refinement for different climates and soil types.
The collaborative study involved the University of Minnesota, the Minnesota Department of Agriculture, and USDA-ARS. It was funded by the Clean Water, Land and Legacy Amendment Fund.
“This project highlights the value of collaborative work, goodwill, trust and data sharing to accomplish a common objective,” said Fernández.
This research empowers producers to reduce waste, protect yields, and apply fertilizer more responsibly.
Photo Credit:gettyimages-oticki
Categories: Minnesota, Crops, Corn, Energy, Weather