Design and Validation of a Laboratory System for Measurement of Volatilized Ammonia

The design of laboratory systems for studying ammonia (NH 3 ) released from fertilizers varies widely, and few designs have been tested to determine the accuracy and precision in measuring NH 3 loss. A standard volatilization system design is needed for reliable and comparable studies of NH 3 volatilization from N fertilizer. The objectives of this study are: (i) to describe the design of a system capable of controlling air flow rate and temperature for laboratory measurement of NH 3 volatilized from N fertilizers; and (ii) assess the system's efficiency and variation in recovering NH 3 lost from NH 4 Cl applied to an alkaline sand media. The system is comprised of individual chambers for soil and fertilizer, where temperature can be varied from room temperature to ∼32°C; humidity is maintained near saturation, air flow rate can be varied, and acid traps are used to capture volatilized NH 3 . Two initial trials (I and II) were conducted at an N rate of 90 kg N ha −1 using air flow rates of 2.00 and 1.00 L min −1 and trapping acid volumes of 50 and 100 mL, respectively. A third trial was conducted at 30°C. A fourth trial (IV) was performed using a range of N application rates (25–250 kg N ha −1 ). The system recovered 89.3 to 97.1% of the N applied over all four trials and provided accurate and repeatable results under the conditions tested. Rapid, precise comparisons of NH 3 volatilization losses from N fertilizers under laboratory conditions can be made with this system.