- Urea is a common nitrogen fertilizer for sweet corn production. This two year project evaluated commercially available urea additives for their potential to provide crop production and environmental benefits. Specifically, experiments were designed to evaluate the efficacy of urea fertilizer products containing a urease inhibitor (Agrotain Ultra), or nitrification inhibitors, or a polymer coated urea product (ESN). Products containing nitrification inhibitors (SuperU and Instinct) were evaluated only in 2014, and found to have efficacy similar to ESN in slowing conversion of urea to leachable nitrate-N. The control treatment in all studies was granular urea without additives.