A Laboratory System to Measure Ammonia Volatilization From Soil and Fertilizer.

The designs of laboratory systems for studying ammonia (NH₃) released from fertilizers varies widely and few designs have been tested to determine  accuracy and precision in measuring ammonia loss from multiple nitrogen (N) sources. A standard volatilization system design is needed for reliable and comparable studies of ammonia volatilization from nitrogen fertilizer. The objective of this study is to describe the design of a system capable of controlling air flow rate, maintaining constant humidity, and varying temperature for laboratory measurement of NH₃ volatilized from N fertilizers. The system is comprised of individual chambers for soil and fertilizer, where temperature can be maintained and monitored between ambient air temperature and 30 ^o C, humidity is maintained at ~100%, air-flow rates can be varied, and acid traps are used to capture volatilized NH₃. 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, temperature of 26° C and trapping acid volumes of 50 and 100 ml, respectively. The acid traps recovered 94.0±1.6% of lost N in trial I and 96.7±1.8% of lost N in trial II. A third trial (III) was performed using a range of N application rates (25 to 250 kg N ha^-1). Measurements indicated the system accounted for 95.7±1.5% of applied N at the 25 kg N ha^-1 rate and 89.3±2.3% at the 250 kg N ha^-1 rate.   These results indicate the system tested provides accurate and repeatable results under the conditions tested. Rapid, precise comparisons of NH₃ volatilization losses from N fertilizers can be made with this system.