By Blake Jackson
The University of Kentucky Cooperative Extension has introduced updated nitrogen (N) fertilizer recommendations for corn in the latest AGR-1 guide, reflecting findings from more than 150 field trials conducted between 2013 and 2023.
According to Dr. John Grove, UK Soils Research & Extension, the research included modern corn hybrids and numerous on-farm studies, providing recommendations better suited to today’s production systems than older fertilizer models.
The revised guidelines assume producers are following sound crop management practices, including proper plant populations, balanced fertility, and effective pest control. They also account for crop rotation, tillage practices, soil drainage, and the potential for nitrogen loss.
For the first time, the recommendations also consider whether no-till fields use cereal cover crops and whether a volatilization inhibitor accompanies surface-applied urea fertilizer.
Economic conditions are another factor. The recommended nitrogen rates were developed using an N-to-corn price ratio of about 0.1. However, during the 2026 season, fertilizer costs pushed that ratio closer to 0.15, meaning some standard recommendations may exceed the most economical application rate.
To compare approaches, five on-farm trials were evaluated using soil samples submitted to a private laboratory. While the updated AGR-1 recommendations ranged from 145 to 165 pounds of nitrogen per acre, the private lab suggested between 170 and 300 pounds per acre based primarily on predetermined yield goals.
In most cases, the lab calculated nitrogen needs by multiplying the expected yield by 1.2 pounds of nitrogen per bushel, without considering field-specific management or soil conditions.
University researchers argue that the yield-goal method oversimplifies nitrogen management. Kentucky field research has shown there is little relationship between a field’s maximum yield and its economically optimal nitrogen rate. Similar findings have also been reported by researchers in Mississippi and Ohio.
The yield-goal formula traces back to research conducted in the 1950s through the early 1970s. More recent evaluations have questioned whether this decades-old approach remains appropriate for modern corn production.
UK researchers encourage growers to use science-based recommendations that reflect current genetics, production practices, environmental conditions, and nitrogen management tools to maximize profitability while improving fertilizer efficiency.
Photo Credit: gettyimages-luc-pouliot
Categories: Kentucky, Crops, Corn