Enhanced Efficiency Fertilizers: Effect on Agronomic Performance of Corn in Iowa

Management of N in corn (Zea mays L.) production systems attempts to increase crop yields and minimize environment impact. This study evaluated enhanced efficiency fertilizers (EEFs) compared to their non‐EEF forms on grain yield and corn biomass at the beginning of the grain‐filling period, leaf chlorophyll index (CI) measurements, spectral reflectance, and leaf area index throughout the growing season. These studies were conducted on a continuous corn study from 2008 through 2010 stabilized urea with urease and nitrification inhibitors (SuperU [Koch Agronomic Services, Wichita, KS]), urea‐ammonium nitrate (UAN) with and without a urease and nitrification inhibitor (AgrotainPlus [Koch Agronomic Services, Wichita, KS]), and environmentally smart nitrogen polymer coated urea (ESN [Agrium Advanced Technologies, Loveland, CO]). There was no significant effect of EEFs compared to non‐EEF materials on the biomass or leaf area indices (LAI) at the end of vegetative development; however, there were consistently higher yields with the EEF materials. Differences in yield were related to increased leaf CI values during the grain‐filling period and a summation index based on leaf CI was linearly related to grain yield. Use of the EEF materials decreased the rate of leaf senescence with a linear relationship for each year but not a common relationship among years. Application of EEF materials to corn produced a positive impact on grain yield through the increased ability of the corn canopy to maintain green leaf area, capture photosynthetically active radiation (PAR) and convert this energy into larger yields. The effect of EEF materials on improved grain‐fill under rainfed conditions of the central Corn Belt provides effective N management strategies to increase yield.