Development of a novel method to measure NH3 fluxes from grass swards in a controlled laboratory environment (a mini-tunnel system)

Abstract

A description of the development of a mini wind-tunnel system for the measurement of ammonia volatilisation from grass swards is given. Tunnel design was based on that of Lockyer (1984), but scaled in order to enable controlled laboratory studies to be carried out and allow investigations of the pathways and mechanisms that control NH3 emission and deposition from grassland swards. The potential of the system was examined by using 15N as a tracer in a study measuring NH3 volatilisation from a source of artificial urine. Deposition along the sward was examined up to 70 cm from the source. Deposition onto the leaf surface and uptake into the leaf via stomata were examined with leaf washing experiments and a compensation point in the range of 0.5–1.9 μg m−3 was calculated.