Corn Yield and Nitrogen Use Efficiency Response to ESN and Urea Blends in the Deep South.

Environmentally Smart Nitrogen (ESN) is a commercially available polymer coated urea (44-0-0) for row crop production. Some regions have shown increased yield and nitrogen use efficiency (NUE) during corn production using ESN compared to urea. Growers and regulatory agencies are interested in ESN to improve yield and NUE in the Deep South.  Since ESN release rates are temperature dependent, data from the Deep South are needed to make policy and fertility recommendations.  The objective was to determine: 1. ESN-N release rates, and 2. Optimization of urea:ESN blends and application timing for yield and NUE.  Blends of ESN and urea were applied either pre-plant or split-applied during four site-years at two sites. Blend treatments were 100% urea, 50:50 urea:ESN, 25:75 urea:ESN, and 100% ESN, plus a 0 N check.  Application timing treatments were 100% at planting or 25% at planting and 75% at V5. Treatments were arranged as a randomized complete block with four replications at Jay, FL and Citra, FL. ESN-N release rates for both at-plant and sidedress application timings were determined using litterbag methodology at both locations during 2015 and 2016. ESN release rates were fit to quadratic functions with R²_adj. >0.813. We hypothesized that incorporated ESN would release N slower than broadcast ESN due to soil temperature differential. Contrary to our hypothesis, incorporated ESN released N faster than broadcast ESN, likely due to prill damage. Incorporated ESN released 50% N in 14-27 days. Broadcast ESN released 50% N in 16-37 days. Corn yield and NUE did not generally respond to differing urea:ESN blends. Given the added expense per unit N of ESN compared to urea, coupled with the lack of yield and NUE response under the conditions of this study, the use of ESN for corn production in the Deep South appears unlikely to have agronomic nor economic returns.