『Abstract
　Over the past few years the number of biogas slurries, which are generally used as nitrogen fertilizers, have seen a steady increase in Germany. A mechanistic ammonia volatilisation model was developed to predict the ammonia losses of these slurries when applied to bare soil, maize, wheat and rye grass canopies. Data for model development were collected from several field measurements carried out at two locations in Northern Germany between the years of 2007 and 2008. Additionally, the behaviour of the slurries on and in the soil was investigated through the use of infiltration pot experiments. The model includes three main compartments: slurry, atmosphere and soil. The soil compartment model is relatively simple, as the slurry infiltration, nitrification and ploughing dislocation into the soil determined in the experiments showed quantitatively no significant differences between the tested slurries (mono-fermented, co-fermented and pig slurry) and soils (sand soil and loamy sand). Hence, instead of a complex soil model, stable reduction factors, as derived from the experiments, were implemented in the model. Simulated ammonia emissions were statistically compared (root mean square error (RMSE), modelling efficiency (ME), linear regression) to the observed emissions. All evaluations showed an acceptable model performance (RMSE = 1.80 kg N ha^-1), although there were a few number of anomalies which could not be modelled in an adequate way. A model sensitivity analysis showed that temperature and slurry pH value are the main drivers of NH3 volatilization in the model. Following a change of +1℃ or of +0.1 pH unit ammonia volatilization will increase by about 1% and 1.6% of the applied total ammoniacal nitrogen, respectively. We were able to show that a simple model approach could explain most factors of ammonia volatilization in biogas crop rotations.

Keywords: Biogas slurry; Ammonia volatilization; Mechanistic model』

Nomenclature
　Weather data
　PenMonteith
　Atmosphere
　Ploughing
　Ammonium
1. Introduction
2. Materials and methods
　2.1. Model theory
　　2.1.1. Modelling assumptions
　　2.1.2. Slurry/biogas slurry
　　2.1.3. Atmosphere
　　2.1.4. Modelling environment
　2.2. Experiments
　　2.2.1. Experimental design and study sites
　　2.2.2. Meteorological data
　　2.2.3. Soils
　　2.2.4. Organic fertiliser
　　2.2.5. NH3 loss measurements
　　2.2.6. Interaction of biogas slurries with soil
　　2.2.7. Statistics
3. Results
　3.1. Infiltration
　3.2. Effect of ploughing on NH4⁺ contents in the surface soil
　3.3. Nitrification
　3.4. NH4⁺ adsorption capacity in soil
　3.5. Buffer capacity
　3.6. Modelling results
　　3.6.1. Parameterisation
　　3.6.2. Validation runs
　3.7. Sensitivity analysis
4. Discussion
5. Conclusion
Acknowledgement
References