Construction and Validation of Small Mobile Wind Tunnels for Studying Ammonia Volatilization

Ammonia volatilization is a major nitrogen (N) loss process for surface applied manures and urea fertilizers.Ammonia volatilization is a complex phenomenon requiring specialized research equipment to gather valid scientific data,which is essential for developing management practices to minimize N losses from farms and N inputs to neighboringecosystems. The objectives of this work were: i) to describe a revised version of the small mobile windtunnels originallyreported by Lockyer, and ii) to assess the ability of these wind tunnels to quantitatively recover ammonia lost from dilutesolutions. The design, construction, cost (about $4000 each), physical calibration, and operation of the wind tunnels aredescribed. The tunnels consist of two connected parts: i) a transparent plastic canopy which covers a 1m 2 treatment area,and ii) a sheetmetal cylinder, which houses an adjustable speed motor with attached fan blade and an air sampler to monitorammonia volatilization. Two ammonia lossandrecovery experiments were conducted at constant wind speeds of 0.5 and1.0 m s 1 to assess tunnel performance. Mean ammonia recoveries were 104 6% at 0.5 m s 1 and 104 18% at 1.0 m s 1 .These results demonstrate that the wind tunnels can be valid tools for collecting volatilized ammonia and for making relativecomparisons among N management treatments. Obtaining valid comparison of different management treatments is essentialfor the development of improved N management practices that minimize ammonia losses from manures or fertilizers.