Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 1, 2002
Publication Date: N/A
Interpretive Summary: Ammonia volatilization, the conversion of nitrogen into ammonia gas, is a major loss process for surface applied manures and urea fertilizers. Ammonia volatilization is a complex process requiring specialized research equipment to gather valid scientific data. Sound ammonia loss data is needed for developing management practices to minimize nitrogen losses to the farmer and minimize nitrogen inputs into the Chesapeake Bay. This work describes the design and construction of small wind-tunnels and assess the ability of these wind tunnels to recover ammonia lost from dilute solutions. A detailed description is given of the design, construction, cost, physical calibration, and operation of the wind tunnels. The tunnels utilize a plexiglass canopy which covers about ten square feet of treatment area and is connected to a sheet-metal fan housing. The housing encloses an adjustable speed motor and fan plus an air sampler which can monitor ammonia losses over time. The cost of each tunnel is about $4,000. Two ammonia loss/recovery experiments were conducted using constant wind speeds of 1.1 miles per hour (mph) and 2.2 mph to assess tunnel performance. Ammonia recoveries averaged 104% plus or minus 6% at 1.1 mph and 104% plus or minus 18% at 2.2 mph. These results demonstrate that the wind tunnels can completely recover ammonia lost from alkaline solutions and that wind tunnels are valid tools for studying ammonia volatilization. The tunnels can be used for comparing ammonia losses from various nitrogen management practices, for example: studying tillage effects or comparing crop residue effects. Comparing management practices is essential for developing nitrogen management options for the extension service and soil conservation service that minimize ammonia losses and protect the Chesapeake Bay.
Technical Abstract: Ammonia volatilization is a major N loss process for surface applied manures and urea fertilizers. Ammonia volatilization is a complex phenomena involving both chemical conversion of ammonium-N to dissolved ammonia gas, and physical transport of the ammonia gas into the air. Therefore, studying ammonia losses requires specialized research equipment. Gathering sound ammonia volatilization data is essential for developing management practices to minimize N losses to the farmer and to minimize N inputs to neighboring ecosystems. The objectives of this work were: i) to describe a revised version of the small wind-tunnels originally reported by Lockyer in 1984, and ii) to assess the ability of these wind tunnels to quantitatively recover ammonia lost from dilute solutions. A detailed description is given of the design, construction, cost (about $4,000 each), physical calibration and operation of the wind tunnels. The tunnels utilize a canopy covered 12m mtreatment area connected to a sheet-metal tunnel housing an adjustable speed motor and fan plus an air sampler which can monitor ammonia volatilization over time. Two ammonia loss-and-recovery experiments were conducted at constant wind speeds of 0.5 and 1.0 m/s to assess tunnel performance. Ammonia recoveries averaged 104 percent plus or minus 6% at 0.5 m/s and 104% plus or minus 18% at 1.0 m/s. These results demonstrate that the wind tunnels can quantitatively recover ammonia lost from alkaline solutions. Therefore, wind tunnels are valid tools for collecting volatilized ammonia and making relative comparisons among replicated N management practices to minimize ammonia losses from manures or fertilizers.