Physical Coating of Nitrogen Source Improved Corn Yield Compared to Conventional Source or Chemical Intervention.

Increasing economic and environmental concerns in corn production have prompted the need for improved nitrogen (N) management.  In this study, effects of different N sources [urea-ammonium-nitrate (UAN) with methylene urea (UAN-MU), split applied UAN-MU, UAN with Instinct (UAN-IN), UAN with Nutrisphere-N (UAN-NS), and polymer-coated urea (PCU)] on corn response were evaluated at different N rates compared to conventional source, UAN. Leaf chlorophyll was indirectly measured using a chlorophyll meter at different corn growth stages for all N treatments to determine in-season corn N status. At different growth stages taken individually or together, chlorophyll meter readings were significantly correlated to grain yield. The treatment UAN-MU-SP increased grain yields compared to UAN. The treatments UAN-NS and UAN-IN had a mixed result in relation to UAN. The results indicated that PCU consistently performed better than any other N treatment, either UAN alone or UAN with additives. Our results also highlighted effects of inter-annual climatic variation that mediated contrasting responses to different N management.