Comparing Closed Chamber Measures of Ammonia Volatilization from Kentucky Bluegrass Fertilized by Granular Urea1

Abstract

Abstract Easy handling and low unit N cost make prilled urea (46-0-0) a popular fertilizer. While incomplete recovery of granular urea applications by turfgrass is documented, practical guidance for small-plot field assessment of ammonia (NH3) volatilization remains limited. Our objectives were to (i) develop a method for field-implementation of closed flux/dynamic chambers to measure ammonia emission over a 3-day period following granular urea application to turfgrass, and (ii) infer the significance of said measures to levels arising from simultaneous static-chamber measures. A Kentucky bluegrass (Poa pratensis L. ‘Midnight’) lawn was treated with granular urea-N at a rate of 0 or 43 kg.ha−1 (38 lb/A) twice in both 2014 and 2015. Flux chamber measures of mean ammonia volatilization from urea-N fertilizer applied 3 days previous exceeded simultaneous static chamber measures by a factor of 17. Relative to static, the closed dynamic/flux chamber system described affords a more precise and efficient method for measuring ammonia volatilization from small field plots. Furthermore, over a 3-day period of dry conditions and ambient temperatures fluctuating between 10 and 31 C (50 and 88 F), as much as 23.1% of a granular urea application broadcast over a Kentucky bluegrass lawn can be volatilized as ammonia. Index words: flux, gaseous emissions, methods, nitrogen, static, turfgrass. Species used in this study: ‘Midnight' Kentucky bluegrass (Poa pratensis L.).