In Situ Measurement of Ammonia Emissions from Organic Fertilizers in Plot Experiments
- Robert Vandré and
- Martin Kaupenjohann
Ammonia volatilization from slurry in the field is either measured under open atmosphere from large field plots (integrated horizontal flux [IHF], mass balance) or in closed, ventilated chambers (e.g., wind tunnels), which allow the measuring of small plots but influence the climatic conditions. We conducted this study to evaluate a new method for measuring NH3 volatilization on small experimental plots under ambient climatic conditions (including rain and wind). Various pretreated cattle slurries were applied to small plots (2 by 2 m) in tillering winter wheat (Triticum aestivum L.). Ammonia collected by passive samplers on manured plots was compared with NH3 collected on standard plots, where known rates of NH3 were being released via a tubing system (standard comparison [SC] method). Forty-five manured plots were measured simultaneously by comparison with two standard plots. The specific detection limit of this experiment was 2.5 µg NH3-N m−2 s−1 (90 g NH3-N ha−1 h−1). Below this value, the coefficient of variation of measured NH3 release exceeded 30%. Slurry was applied to plastic gutters on two control plots. Measured NH3 losses from these plots accounted for 78% of the absolute NH4-N losses determined by sampling and analyzing slurry from the gutters. Measurement of the control plots was repeated during the ripening of the wheat. A strong deviation between the measurements of the two plots suggested that the accuracy of the new method is limited in dense vegetation. The results are discussed with respect to measurement accuracy and possible sources of error. A comparison with literature reports indicated that the accuracy of the SC method compared favorably to micrometeorological methods and wind-tunnel systems.
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