GerminatingPhase

The GerminatingPhase represents a phenological sub-phase within a plant’s developmental timeline, responsible for simulating the transition from sowing to germination. It defines the conditions under which a seed germinates and completes the phase once those criteria are satisfied. Typically, it spans from the Sowing stage to the Germinated stage, and its completion is determined by either environmental triggers, e.g. soil moisture, temperature, or a user-specified germination date.

Overview

The GerminatingPhase models the transition from sowing to germination in the crop’s phenological development. Germination is assumed to occur on the day after sowing, when any of the following conditions are met:

  • Soil water at the sowing depth exceeds the lower limit (LL15),
  • Soil temperature at the sowing depth is greater than or equal to the minimum soil temperature (as defined by the MinSoilTemperature child function),
  • A specific germination date is provided via the GerminationDate property.

Once any of these conditions is satisfied, the seed is considered germinated, the SeedImbibed event is raised, and the simulation advances to the next phenological phase.

Germination Triggers

Germination occurs in one of two ways:

  1. User-defined germination date

If GerminationDate is specified, germination occurs exactly on that date, regardless of soil moisture or temperature.

  1. Environmental conditions at sowing depth

If no date is defined, germination is triggered when:

  • Soil water content exceeds the lower limit (LL15) for the sowing layer:

SWmm[layer] > LL15mm[layer]

  • Soil temperature at sowing depth exceeds the minimum required value:

SoilTemperature[layer] >= MinSoilTemperature.Value()

  • The current day is not the sowing day.

Sowing Depth: The sowing layer is determined using the value of plant.SowingData.Depth, which maps to the appropriate soil layer index.

Events

Events Listened For

These are signals or notifications that the GerminatingPhase listens for from other parts of the simulation:

Event Purpose
PlantSowing Indicates when the plant is sown, allowing the phase to determine the soil layer depth where seeds are placed. This is essential for checking soil conditions relevant to germination.

Events Raised to

These are signals that the GerminatingPhase sends out to notify other components when actions occur:

Event Description
SeedImbibed Raised when germination occurs, signaling other models or processes to begin their activities related to the germinated seed.

Properties

Configurable and Reportable Properties

Property Type Description Required
Start string Phenological stage at which this phase begins (e.g. Sowing). Yes
End string Phenological stage that marks completion of the phase (e.g. Germinated). Yes
MinSoilTemperature double Minimum soil temperature required for germination (default is 0°C). Yes
GerminationDate string Optional fixed calendar date to override environmental conditions. No
IsEmerged | bool | Boolean flag indicating whether the crop has emerged above the soil surface (i.e. this phase is happening above ground). | No |

Read-Only Reportable Properties

Property Type Description
FractionComplete double Fraction (0–1) indicating how much of the phase is complete. Always returns 0 as germination has occurred in next day of sowing.

Usage

A GerminatingPhase can be used to represent the germination process of a plant, which is primarily influenced by soil moisture and temperature conditions.

See Also