1. Crop emissions Nick Hutchings
Institute of Agroecology, University of Aarhus, Denmark

2. Conceptual model NH3 emission Time Fertiliser emission Crop emission
Crop absorption
NH3 emission
Crop
harvesting
Fertiliser
application
Time

3. Guidebook emission factors
Current emission factors account for:
Emission from fertiliser
Emission from crop immediately after fertiliser application
Crop absorption (crudely)
Current emission factors do not account for:
Emission from senescing/diseased crops

4. Issues Other emissions are decreasing For modelling secondary PMs
Crop emissions relatively more important
For modelling secondary PMs
Higher time resolution
Higher spatial resolution
Emissions depend on atmospheric NH3 concentrations
Unfortunate combination:
Low emission rate per ha x large number of ha
Large uncertainty in emission rate per ha

5. Suggested way forward Review literature Talk to atmospheric modellers
Part of Guidebook revision
Lack information
Talk to atmospheric modellers
Discuss issue under Tier 3 methodology