BROOKINGS, S.D. – South Dakota State University Extension has updated the corn nitrogen Fertilizer Recommendations Guide to reflect lowered rate recommendations.
Forty-five corn nitrogen rate trials conducted from 2018 to 2022 in South Dakota fields showed that the pounds of nitrogen per bushel of corn multiplier can be reduced to a multiplier of 1.0 pounds of nitrogen per bushel of corn.
The updated guide is available at extension.sdstate.edu/fertilizer-recommendation-guide.
Before 2023, the equation used a multiplier of 1.2 pounds of nitrogen per bushel of corn, and was accurate to within about 60 pounds per acre of corn. This new research, funded by the Nutrient Research Education Council, shows that a multiplier of 1.0 pounds of nitrogen per bushel of corn is accurate to within about 35 pounds per acre.
Nitrogen (N) is a nutrient essential to plant growth. Some of nitrogen that crops need is naturally available in soil, and the remaining amount is often supplied through the application of fertilizers.
Every year, corn plants use 98 to 250 pounds of nitrogen per acre. Applying the right amount of nitrogen optimizes crop yields, can increase farmer profits and is better for the environment. Farmers, agronomists, and others involved in making fertilizer rate decisions use an equation to determine the proper amount of nitrogen fertilizer to apply. The equation includes the factors of yield potential, pounds of nitrogen per bushel of corn multiplier, preplant soil test nitrogen to a depth of 0 to 24 inches, previous crops planted, manure application and tillage type.
Jason Clark, SDSU Extension Soil Fertility Specialist, said the improved accuracy means a potential savings of about $36 per acre without decreasing yields. That savings, spread across 6 million acres of corn planted every year in South Dakota, equals about $216 million.
“Research in accurate nitrogen rate recommendations is needed because excessive nitrogen fertilizer applications can reduce fertilizer efficiency, create environmental contamination issues, and reduce grower profits,” Clark said.
Producers are encouraged to use the Rate Guidelines Calculator excel worksheets to determine what will work best in their own fields. There is also a video demonstrating how to use the calculator on the SDSU Extension website, and a fact sheet that provides detailed explanations of the data used to update the fertilizer recommendations.
The nitrogen fertilizer rate recommendation equation is now: N fertilizer rate = Yield potential × 1.0 lbs N/bu - Soil test nitrogen - Legume credits - Manure credits + No-till debit.
For more information, contact Jason Clark, SDSU Extension Soil Fertility Specialist.