BBCH
A phenological staging system that converts APSIM-NG’s internal growth stages into standardized BBCH (Biologische Bundesanstalt, Bundessortenamt und CHemische Industrie) growth stages for cereals (Meier 2001), providing internationally recognized developmental benchmarks for agricultural research and management.
Overview
The BBCH implements a comprehensive translation system that converts APSIM-NG’s internal phenological phases into the internationally standardized BBCH growth stage codes (Meier 2001) widely used in agricultural research and crop management. This system provides a common language for describing crop development stages across different simulation platforms and field observations, enabling seamless integration between modeling and practical applications.
The BBCH system divides crop development into 10 principal growth stages (0-9), each subdivided into secondary stages, creating a numerical scale from 00 to 99. This model specifically handles cereal crops from germination through harvest, incorporating key developmental milestones such as emergence, leaf appearance, stem extension, flowering, and grain development.
Model Structure
This section describes how this model is positioned within the APSIM framework. It outlines the broader structural and computational components that define its role and interactions in the simulation system.
This model inherits structural and functional behaviour from the following core APSIM components:
Connections to Other Components
This section describes how the model interacts with other components in the APSIM Next Generation framework.
These connections allow the model to exchange information—such as environmental conditions, developmental stage, or physiological responses—with other parts of the simulation system. For a general overview of how model components are connected in APSIM, see the Connections Overview.
| Component | Model | Connection Type | Description |
|---|---|---|---|
| Phenology | Phenology | First Available | Provides current growth phase, stage progression, and fraction completed within phases. |
| Leaf | Leaf | First Available | Supplies leaf appearance, expansion, and cohort data for calculating vegetative stages. |
| Structure | Structure | First Available | Provides final leaf number and structural development parameters. |
Model Variables
This section lists the key variables that describe or control the behaviour of this component. Some variables can be adjusted by the user to modify how the model behaves (configurable), while others are calculated internally and can be viewed as model outputs (reportable). For a general explanation of variable types and how they are used within the APSIM Next Generation framework, see the Model Variables Overview.
Configurable and Reportable Properties
No configurable properties are available for this function.
Read-Only Reportable Properties
| Property | Type | Description |
|---|---|---|
| Stage | double | Current BBCH growth stage value (0-99 scale) calculated from internal phenological state. |
Processes and Algorithms
This section describes the scientific processes and algorithms represented by this component. Each process corresponds to a biological, physical, or chemical mechanism simulated during a model time step. Where appropriate, equations or conceptual summaries are provided to explain how the process operates within the APSIM Next Generation framework.
Reference Table: Phase-Based BBCH Calculations
For reference, the complete mapping of APSIM-NG phases to BBCH calculations:
| Begin Stage | Growth Phase | BBCH Calculation | Description |
|---|---|---|---|
| 1 | Germinating | \(5 \times F_{\text{phase}}\) | Early germination progress |
| 2 | Emerging | \(5 + 5 \times F_{\text{phase}}\) | Emergence from soil surface |
| 3-4 | Juvenile or PhotoSensitive | \(10 + (N_{\text{leaves}} - 1)\) | Initial leaf development |
| 5 | LeafAppearance (before flag) | \(30 + N_{\text{leaves expanded}}\) | Stem extension and node development |
| 5 | LeafAppearance (after flag) | \(50 + 5 \times F_{\text{flag expansion}}\) | Flag leaf emergence |
| 6-10 | Reproductive phases | Linear interpolation | Flowering to maturity |
where \(F_{\text{phase}}\) is the fraction through the current phase, \(N_{\text{leaves}}\) is the number of appeared leaves, and \(F_{\text{flag expansion}}\) is the fraction of flag leaf expansion.
Early Vegetative Development (BBCH 00-19)
The BBCH model calculates growth stages based on the current phenological phase, with different calculation methods applied depending on the developmental stage.
Germination Phase (BBCH 00-05):
During the Germinating phase, BBCH stage is calculated as:
\[ \text{BBCH} = 5 \times F_{\text{germ}} \]
where \(F_{\text{germ}}\) represents the fraction of progress through the germination phase.
Emergence Phase (BBCH 05-10):
During the Emerging phase, BBCH stage is calculated as:
\[ \text{BBCH} = 5 + 5 \times F_{\text{emerg}} \]
where \(F_{\text{emerg}}\) represents the fraction of progress through the emergence phase.
Leaf Development Phase (BBCH 10-19):
During Juvenile or PhotoSensitive phases, BBCH stage is calculated based on the number of appeared leaf cohorts:
\[ \text{BBCH} = \min(19, 10 + \max(0, N_{\text{appeared}} - 1)) \]
where \(N_{\text{appeared}}\) is the number of leaf cohorts that have appeared. This calculation accounts for the “droopy leaf” method where visible leaf tips are one fewer than fully developed leaves.
Stem Extension and Node Development (BBCH 30-39)
When the plant enters the LeafAppearance phase and appeared leaf cohort number is less than final leaf number, the BBCH transitions to stem extension stages:
\[ \text{BBCH} = 30 + \min(9, N_{\text{expanded}} - N_{\text{initial}}) \]
where \(N_{\text{expanded}}\) is the current number of expanded leaf cohorts and \(N_{\text{initial}}\) is the number of expanded cohorts at the start of stem extension. The model assumes node appearance occurs at the same rate as leaf appearance.
Inflorescence Development (BBCH 50-59)
BBCH stage 50 occurs when the tassel becomes visible, which corresponds to the appearance of the flag leaf tip. During flag leaf expansion within the LeafAppearance phase after the final leaf has appeared:
\[ \text{BBCH} = 50 + 5 \times \frac{F_{\text{current}} - F_{\text{BBCH50}}}{1 - F_{\text{BBCH50}}} \]
where \(F_{\text{current}}\) is the current fraction through the LeafAppearance phase and \(F_{\text{BBCH50}}\) is the fraction when BBCH 50 was reached. This assumes the tassel will be half emerged when the flag leaf is fully expanded.
Reproductive Development (BBCH 55-99)
Later stages use linear interpolation between key phenological milestones:
The mapping between APSIM-NG stages and BBCH codes is:
| APSIM Stage | APSIM Name | BBCH Code | BBCH Description |
|---|---|---|---|
| 6.0 | FlagLeafFullyExpanded | 55 | Mid-tassel emergence |
| 7.0 | Flowering | 65 | Mid-flowering |
| 8.0 | StartGrainFill | 70 | Beginning of grain development |
| 9.0 | EndGrainFill | 87 | Physiological maturity |
| 10.0 | Maturity | 99 | Harvest product |
User Interface
BBCH can be added as a child of a Phenology node in the model tree. Right-click the Phenology node, select “Add Model…”, and search for BBCH in the Filter Box.
See Also
- Source code: BBCH.cs on GitHub
References
Meier, U. 2001. Growth Stages of Mono-and Dicotyledonous Plants BBCH Monograph. Federal Biological Research Centre for Agriculture and Forestry.