Daily Nitrogen Demand for Storage Organs
The StorageNDemandFunction calculates the nitrogen (N) demand for storage in a plant organ, aiming to bring the organ’s N content up to its maximum nitrogen concentration.
Overview
This function determines the additional N required for storage after meeting the structural and metabolic N demands. It ensures that the organ’s N content does not exceed its maximum nitrogen concentration.
Inputs
- maxNConc: A
IFunctionfor maximum nitrogen concentration which the organ can achieve. - nitrogenDemandSwitch: A switch (typically 0 or 1) to modulate N demand based on environmental or physiological conditions. For example, nitrogen demand of wheat stem is switched on from
EmergencetoMaximumGrainLengthstages, and switched off afterwards. - parentOrgan: The organ that implements the
IArbitrationinterface, i.e. an organ whichStorageNDemandFunctionattached to, which provides access to the organ’s properties such as live weight and current N content.
Methodology
The potential biomass after potential allocation is calculated as biomass at previous day (\(DM_{\text{Live}, i-1}\)) plus the potential allocation to the organ (\(A_{\text{P}, i}\)): \[ DM_{\text{Live}, i} = DM_{\text{Live}, i-1} + A_{\text{P}, i} \]
The maximum nitrogen content (potential) at day \(i\) is calculated as
\[ N_{\text{Live}, i} = C_{\text{N, max}} \times DM_{\text{Live}, i} \]
The nitrogen demand for storage is then calculated as the difference between the maximum nitrogen content and the current nitrogen content in the live biomass, adjusted by structural and metabolic demands:
\[ D_{\text{N, Storage}} = N_{\text{Live}, i} - N_{\text{Live}, i-1} - D_{\text{N, Structural}} - D_{\text{N, Metabolic}} \]
Where:
- \(D_{\text{N, Storage}}\): Nitrogen demand for storage at day \(i\).
- \(N_{\text{Live}, i}\): Nitrogen content in the live biomass at day \(i\).
- \(N_{\text{Live}, i-1}\): Nitrogen content in the live biomass at the previous day (\(i-1\)).
- \(D_{\text{N, Structural}}\): Nitrogen demand for structural functions at day \(i\).
- \(D_{\text{N, Metabolic}}\): Nitrogen demand for metabolic functions at day \(i\).
Implementation Details
- The function is part of the
Models.Functions.DemandFunctionsnamespace. - It implements the
IFunctioninterface, allowing it to be used within the APSIM model framework. - During simulation commencement, it identifies its parent organ implementing the
IArbitrationinterface to access necessary properties.
Events
Events Listened For
These are signals or notifications that the function listens for from other parts of the simulation:
| Event | Purpose |
|---|---|
| Commencing | Get parent organ from simulations |
Events Raised to
No events are raised by this function.
Properties
Configurable and Reportable Properties
No configurable properties are available for this function.
Read-Only Reportable Properties
| Property | Type | Description |
|---|---|---|
Value |
double | Storage demands for nitrogen (N) in the organ |
User Interface
StorageNDemandFunction can be added as a child of a NutrientDemandFunctions node in the model tree. Right-click the parent node, select “Add Model…”, and search for StorageNDemandFunction in the Filter Box.
Practical Example
- Ensure that
maxNConcandnitrogenDemandSwitchare properly defined within the organ’s model to avoid calculation errors. - This function is typically used in conjunction with structural and metabolic N demand functions to comprehensively model an organ’s N requirements.