VOLATILIZATION AND RAPID DEPLETION OF UREA SPRAY-APPLIED TO KENTUCKY BLUEGRASS TURF

Urea was spray-applied to a Kentucky bluegrass (Poa pratensis L.) turf at a rate of 50 kg N ha-1. Two volumes of solution were used to provide application depths of 0.5 and 2.0 mm. Ammonia volatilization and the rate of disappearance of the applied N were then examined over a 48 hr period. Urea-N was positioned primarily on shoots with the 0.5 mm application, whereas the 2.0 mm application distributed the urea equally between the shoot and the thatch/soil layers. Urea positioned in the thatch/soil was hydrolyzed rapidly, while very little hydrolysis occurred with the urea positioned on the shoots. Cumulative volatile loss amounted to 5.3% and 11.6% of the applied N with the 0.5 and 2.0 mm application, respectively. Applied urea-N disappeared rapidly from the turf/soil system. Approximately 80% and 100% of the applied N was depleted by 48 hr for the 0.5 and 2.0 mm application, respectively. The duration of volatile loss was correlated with the period that the urea-N was resident in the turf profile.