Mowing and Nitrogen Source Effects on Ammonia Volatilization from Turfgrass

Abstract

Although NH3 volatilization can be a pathway of N loss from turfgrass systems, the magnitude of this loss has not been well quantified, especially from N sources other than urea. The objective of this research was to evaluate NH3 volatilization as affected by N source and mowing of those N sources. The study consisted of mowing treatments (mowed or not mowed) and N sources: (i) urea, (ii) S‐coated urea, (iii) polymer‐coated urea, (iv) methylene urea, (v) ammonium nitrate, and (vi) composted sewage sludge. Mowing treatments were applied by mowing the N sources, which had been applied to bentgrass (Agrostis palustris Huds.) putting greens. The fertilizers were collected and taken to the laboratory for NH3 volatilization measurements, without additional watering. Treatments were applied at an N rate of 14.7 g m−2 to the surface of bentgrass plugs contained in 1‐L jars. Ammonia volatilization over 10 d was measured via boric acid trapping. Two experiments were conducted: one with loamy sand (Exp. 1) and one with an 80:20 sand–peat (v/v) greensmix (Exp. 2). In Exp. 1, mowing never affected NH3 volatilization, so mowing was eliminated from Exp. 2. Over the 10‐d measurement period, urea had greatest total NH3 volatilization, with most released in the first 2 d. Polymer‐coated urea released the least NH3, with greatest release 9 and 10 d after treatment. In descending order, amounts of NH3 volatilization were urea, S‐coated urea, methylene urea, composted sewage sludge, ammonium nitrate, and polymer‐coated urea.