Improved method for field-scale measurement of ammonia volatilization

We developed a new method for determination of atmospheric ammonia (NH3) em issions from land-applied nitrogen (N). The new method is a modification of two proven passive flux methods, and is an improvement over these existing methods via reductions in cost, labor and analytical requirements. This ne w method involves use of one rotating mast placed in the center of a circul ar plot (15 m radius). The samplers we use are glass tubes (7 mm by 200 mm) that have been coated on the inside with oxalic acid to trap NH3. This new method was tested against one of the proven methods in a field experiment. A circular plot (15 m radius) was established and urea was applied to supp ly 200 kg N ha(-1). Measurements of NH3 volatilization were then made for s ix days after application. A strong linear relationship was evident between our new method and the reference method for both horizontal and vertical N H3 fluxes, as indicated by correlation coefficients of 0.92 and 0.86 for ho rizontal and vertical fluxes, respectively. The glass tubes that we used co nsistently absorbed more NH3 and measured more total NH3 volatilization tha n the samplers of the reference method. However, given that micrometeorolog ical methods have underestimated NH3 volatilization in the past, we feel th at our method has improved the accuracy of NH3 volatilization measurement. In essence, we believe we have developed an improved method for field-scale determination of NH3 volatilization by reducing initial costs as well as l abor and analytical requirements, without sacrificing accuracy of the volat ilization measurement.