Method for Flux-Chamber Measurement of Ammonia Volatilization From Putting Greens Foliarly-Fertilized by Urea

Foliar fertilization is an increasingly popular method of ensuring golf course putting green nitrogen (N) sufficiency in season. The low cost, high N-content, and favorable handling characteristics of urea (46-0-0) make it a common N-source in foliar treatments of horticultural crops. While numerous investigations confirm incomplete recovery of foliarly-applied urea-N by turfgrass, few field assessments of NH₃ volatilization from greens have been conducted. Meanwhile, NH₃ emissions reduce air quality and contribute to non-point nutrient loading of water resources. The research objectives were to (i) develop a method for field-implementation of closed dynamic/flux chambers to measure NH₃ volatilization from 0 to 24 h following foliar application of urea-N to putting greens; and (ii) infer the significance of flux chamber NH₃-N volatilization measures relative to levels arising from simultaneous static-chamber measures. Creeping bentgrass (Agrostis stolonifera L. “Penn G-2”) putting greens were foliarly treated by 20–44 kg urea-N ha⁻¹ from 2013 to 2015, and NH₃ volatilization measured using H₃BO₃ trap-equipped flux and/or static chamber systems. Flux chamber measures of NH₃ volatilization accounted for 7.1% of the urea-N fertilizer applied 24 h previous. Simultaneous static chamber measures of NH₃ volatilization were an order of magnitude less. A replicated flux chamber trapping efficiency trial showed 63% mean NH₃ recovery. Thus under the duration and conditions described, 7.1–11.2% of foliar urea-N applications can be expected to volatilize from putting greens. Regarding closed chamber system measurement of NH₃ volatilization from small field plots, the described flux chambers afford applied scientists a more precise and efficient method than static chambers.