Effects of Enhanced Efficiency Urea on No-tillage Corn Yields and Profit
Larson, J. A., X. Zhou, C. Boyer, X. Yin, M. A. McClure, H. J. Savoy, and M. E. Essington.  2019.  University of Tennessee Extension Publication, W 828.

This publication reviews the profitability of enhanced efficiency (EE) urea products relative to conventional urea and ammonium nitrate fertilizers for no-tillage corn. EE urea is an amended urea product containing urease inhibitors that reduce nitrogen losses to the air for fertilizer applied to the soil surface under no-tillage. Corn yields and profitability for the different nitrogen fertilizer products are from field experiments conducted at Jackson, Milan and Springfield, Tennessee. The key findings are: 1) Urea + nitrogen-(n-butyl)-thiophosphoric triamide (NBPT) and polymer-coated urea (PCU). The two amended nitrogen fertilizers produced the highest corn yields and net returns (corn revenue minus nitrogen fertilizer cost) among the EE urea fertilizers; However, the two amended nitrogen fertilizers did not produce corn yields and net returns similar to ammonium nitrate under no-tillage growing conditions in Tennessee. Ammonium nitrate produced higher yields than urea + NBPT or PCU and was the most profitable nitrogen fertilizer option. However, security concerns may limit its availability as a source of nitrogen for farmers. 2) Urea + NBPT and PCU offer greater potential to improve profitability than urea + maleicitaconic acid copolymer (MICP).The addition of MICP to urea did not improve corn yields or net returns compared with conventional urea. In fact, yields were significantly lower with MICP compared with the other EE urea products.