Polymer Coated Nitrogen Release As Affected By Placement and Date of Application in the Southeast.

Environmentally Smart Nitrogen (ESN) is a polymer-coated, slow release urea that is commercially available in parts of the southeastern United States.  The N release rate from ESN is thought to be temperature dependent, so is expected to differ by climate, placement (buried vs. surface-placed), and date of application.  It was hypothesized that N release would be slower for buried ESN compared to surface ESN due to lower soil temperature.  The objective was to quantify N release rates from ESN under Florida growing conditions when ESN was broadcast or incorporated at planting and sidedress application dates for corn and cotton production.  The release rates were determined at two locations (a sandy loam in Jay, FL and a loamy sand in Citra, FL).  3.0 g ESN (44-0-0) were placed in nylon mesh litterbags and retrieved periodically to determine N release. Three deployment dates were April 1, May 1, and July 1, 2015, representing corn pre-plant, corn sidedress/cotton pre-plant, and cotton sidedress applications, respectively.  Bags were either surface-placed or buried at 10 cm depth, representing broadcast and incorporated application, respectively.  April 1 deployment was at Jay, FL only. N release rates from the two locations were similar for each deployment date.  N release rates from buried and surface ESN were similar during the April 1 and July 1 deployments at both sites, but buried ESN released N faster than surface-placed ESN when deployed on May 1 at both sites. It may be that soil moisture limitations inhibited N release from surface-placed ESN during the May 1 deployment, resulting in faster N release from buried compared to surface ESN.