Field-Based Measurement of Ammonia Volatilization Following Foliar Applications of Urea to Putting Green Turf

Data are lacking in the quantification of N loss mechanisms associated with foliar fertilizer applications that are common to golf course and putting green turfgrass management. This study was conducted to measure ammonia (NH3) volatilization after application of foliar N (as urea) to creeping bentgrass [Agrostis stolonifera L. var. palustris (Huds.) Farw. cv. Penn A1] and hybrid bermudagrass [Cynodon dactylon (L.) Pers. x C. transvaalensis Burtt Davy cv. Tifeagle] putting greens in Fayetteville, AR. Urea was spray-applied monthly, May through September, at rates of 0.5 and 1.25 g N m(-2). Ammonia (NH3) volatilization, over a 24 h period, was measured via boric acid trapping within closed, static diffusion chambers. Month of year and N rate significantly affected the amount of N volatilized from the turfgrass canopy. Measured NH3 volatilization was consistently low each year for both species, with average annual NH3 volatilization of 0.35% and 2.55% from creeping bentgrass and hybrid bermudagrass, respectively. A trapping efficiency study was conducted and revealed that 35 to 50% of evolved NH3-N was directly absorbed by plant tissue enclosed within the chambers. While it was determined that the NH3 trapping methodology used here could not account for all of the NH3 volatilized, data from this study does support the conclusion that foliar N (as urea) applications to putting green turf can be made to actively growing plant tissue throughout the season without concern for substantial N loss via NH3 volatilization.