Comparison of different techniques to measure ammonia emission after manure application

Manure application leads to a number of different environmental problems, as ammonia emission, leaching and nitrous oxide emission. The environmental aspects are on local, regional and global scales. New methods for manure applications have to be developed in order to mitigate the problems. During the developing of these methods, measurements of the nitrogen exchange with the atmosphere has to be performed. For this purpose suitable and reliable measuring techniques are needed. A number of methods to measure the NH3 exchange were therefore tested in parallel. Ammonia emission after band spreading of pig slurry on a young wheat crop was measured using five different techniques. Three variants of the gradient technique were used. The techniques were: i) concentration gradients measured over short periods using FTIR spectroscopy were multiplied with the diffusitivity determined by an aerodynamic method, ii) FTIR gradient with the diffusitivity estimated using a trace gas release, iii) integrating gradient technique in which the wind speed weighted average concentration profile was multiplied with the average diffusitivity, iv) A mass balance technique in which the horizontal flux of ammonia entering and leaving the field was measured, v) a chamber technique in which the emission was calculated from the mass transfer coefficient, ambient, and equilibrium concentrations. The results agreed within ca 25 % with one exception for the chamber technique