Predicted and Observed N Release From Field-Applied Coated-Urea Turfgrass Fertilziers.

A model has been developed to predict N release from polymer-coated urea fertilizers field-applied to turfgrass.  The principal variables in the model are particle size, coating thickness, and temperature.  The model was tested over a 9-month period on bermudagrass (Cynodon sp.) turf in South Florida, beginning in the fall of 2009, using a selection of polymer-coated urea fertilizers having varying particle sizes and coating thicknesses.   They were expected to release N over periods of 4, 6, and 9 months.  N release was gauged both as turfgrass quality ratings over time, and as N remaining at varying time intervals in granules contained in fiberglass-screen packets placed on the turfgrass surface.  In general, the models predicted the observed N release pattern.  Differences between predicted and observed N release appeared to be due to differences in assumed average and actual temperatures.