fr_fungicide_model module

simpest.models.fr_fungicide_model

Daily fungicide degradation, tenacity, and efficacy.

This module advances the fungicide state by one day. After an application, the active ingredient decays through two mechanisms: first-order chemical degradation over time and rainfall-driven wash-off (tenacity). The resulting effective dose is mapped to a protective efficacy through a logistic response, and the treatment is retired after a fixed persistence window.

run(input_, parameters, output, output1)

Advance the fungicide state by one day.

Updates the concentration factor, tenacity, degradation, and protective efficacy for the current day. The calculation proceeds in stages:

1. Concentration. On the application day the concentration factor is reset to 1; thereafter it decays exponentially with the previous day's effective degradation.
2. Potential degradation. First-order decay of the initial dose, initial_dose · exp(-degradation_rate · days).
3. Tenacity. Rainfall wash-off reduces the retained fraction by exp(-tenacity_factor · concentration · √precipitation), applied cumulatively across days.
4. Effective degradation. The product of tenacity and potential degradation, i.e. the dose still active on the canopy.
5. Efficacy. A logistic response of the effective degradation, scaled by the initial efficacy.

If no treatment has yet been applied (date_treatment_last.year <= 1) the call is a no-op. All state is cleared once the persistence window of _MAX_DAYS days has elapsed.

Parameters:

Name	Type	Description	Default
input_	InputsDaily	Daily inputs, including date, precipitation, and the last treatment date.	required
parameters	Parameters	Model parameters, including the fungicide group.	required
output	Outputs	Previous day's output state.	required
output1	Outputs	Current day's output state, updated in place.	required

Returns:

Type	Description
None	The function mutates output1 in place.

Source code in simpest/models/fr_fungicide_model.py

def run(
    input_: InputsDaily,
    parameters: Parameters,
    output: Outputs,
    output1: Outputs,
) -> None:
    """Advance the fungicide state by one day.

    Updates the concentration factor, tenacity, degradation, and protective
    efficacy for the current day. The calculation proceeds in stages:

    1. **Concentration.** On the application day the concentration factor is
       reset to 1; thereafter it decays exponentially with the previous day's
       effective degradation.
    2. **Potential degradation.** First-order decay of the initial dose,
       ``initial_dose · exp(-degradation_rate · days)``.
    3. **Tenacity.** Rainfall wash-off reduces the retained fraction by
       ``exp(-tenacity_factor · concentration · √precipitation)``, applied
       cumulatively across days.
    4. **Effective degradation.** The product of tenacity and potential
       degradation, i.e. the dose still active on the canopy.
    5. **Efficacy.** A logistic response of the effective degradation, scaled by
       the initial efficacy.

    If no treatment has yet been applied (``date_treatment_last.year <= 1``) the
    call is a no-op. All state is cleared once the persistence window of
    ``_MAX_DAYS`` days has elapsed.

    Args:
        input_ (InputsDaily): Daily inputs, including date, precipitation, and
            the last treatment date.
        parameters (Parameters): Model parameters, including the fungicide group.
        output (Outputs): Previous day's output state.
        output1 (Outputs): Current day's output state, updated in place.

    Returns:
        None: The function mutates ``output1`` in place.
    """
    pf = parameters.par_fungicide
    last = input_.date_treatment_last

    # Sentinel: DateTreatmentLast.year == 1 means no treatment yet
    if last.year <= 1:
        return

    # Days since last application
    days = (input_.date - last).total_seconds() / 86_400.0

    # -----------------------------------------------------------------------
    # Concentration factor
    # -----------------------------------------------------------------------
    if input_.date == last:
        # Application day: baseline values
        output1.fungicide.concentration_factor = 1.0
        output1.fungicide.tenacity_function = 1.0
        output.fungicide.tenacity = 1.0
    else:
        # After application: exponential decay based on yesterday's actual degradation
        output1.fungicide.concentration_factor = math.exp(
            (output.fungicide.actual_degradation - 1.0) * 3.0
        )

    # -----------------------------------------------------------------------
    # Potential degradation (first-order decay of initial dose)
    # -----------------------------------------------------------------------
    output1.fungicide.potential_degradation = pf.initial_dose * math.exp(
        -pf.degradation_rate * days
    )

    # -----------------------------------------------------------------------
    # Tenacity (rainfall-driven wash-off)
    # -----------------------------------------------------------------------
    output.fungicide.tenacity_function = math.exp(
        -pf.tenacity_factor
        * output1.fungicide.concentration_factor
        * math.sqrt(max(input_.precipitation, 0.0))
    )
    output1.fungicide.tenacity = (
        output.fungicide.tenacity * output.fungicide.tenacity_function
    )

    # -----------------------------------------------------------------------
    # Actual degradation
    # -----------------------------------------------------------------------
    output1.fungicide.actual_degradation = (
        output1.fungicide.tenacity * output1.fungicide.potential_degradation
    )

    # -----------------------------------------------------------------------
    # Efficacy (logistic response to actual degradation)
    # -----------------------------------------------------------------------
    output1.fungicide.efficacy = pf.initial_efficacy / (
        1.0 + math.exp(
            pf.a_shape_parameter
            - pf.b_shape_parameter * output1.fungicide.actual_degradation
        )
    )

    # -----------------------------------------------------------------------
    # Hard stop: zero everything after 30 days
    # -----------------------------------------------------------------------
    if days >= _MAX_DAYS:
        output1.fungicide.efficacy               = 0.0
        output1.fungicide.actual_degradation     = 0.0
        output1.fungicide.concentration_factor   = 0.0
        output1.fungicide.potential_degradation  = 0.0
        output1.fungicide.tenacity_function      = 0.0