External inputs
There are three possible sources of external inputs of nitrogen to the soil namely deposition, fertilization and manure (for an overview see Structure of Model). Only one of them, manure, also contains carbon. Deposition enters directly to the uppermost soil compartment and into the pools of mineral nitrogen. Fertilization goes into a special state variable representing undissolved fertilizer that is located on the soil surface. Dissolution into the mineral nitrogen pools is made at continuous rates. Manure is directly mixed into the soil to a specified depth and adds to the litter, faeces or ammonium pools as nitrogen and to the litter and faeces pool as carbon.
Deposition occurs continuously whereas fertilization and manure occur at certain dates that correspond to specified day numbers of the year.
Deposition of nitrogen