RUFAS.routines.field.soil.nitrogen_cycling.denitrification module

class RUFAS.routines.field.soil.nitrogen_cycling.denitrification.Denitrification(soil_data: SoilData | None = None, field_size: float | None = None)

Bases: object

A class to handle the denitrification process of nitrogen in the nitrates pool, as outlined in SWAT section 3:1.4.

Parameters

soil_dataSoilData, optional

The SoilData object used by this module to track the denitrification of nitrates in the soil profile. If not provided, a new SoilData object will be created.

field_sizefloat, optional

The size of the field in hectares (ha). This is used to initialize a SoilData object if one is not provided.

Attributes

dataSoilData

The SoilData object used for tracking denitrification.

Notes

The field size is used to initialize a SoilData object for this module to work with, if a pre-configured SoilData object is not provided.

__init__(soil_data: SoilData | None = None, field_size: float | None = None) → None

denitrify(field_size: float) → None

Conducts the daily denitrification operations.

Parameters

field_sizefloat

Size of the field (ha).

References

SWAT Theoretical documentation section 3:1.4, eqn. 3:1.4.1, 2

Notes

The SWAT Theoretical documentation defines denitrification as “the bacterial reduction of nitrate, NO3-, to N2 or N2O gases” (page 194). This method conducts denitrification by calculating the amount of nitrate that is denitrified, then removing that amount from the nitrate pool and adding it to denitrification emissions tracker.

static _calculate_denitrification_amount(nitrate_content: float, denitrification_rate_coefficient: float, temp_factor: float, organic_carbon_fraction: float) → float

Calculates the amount of nitrate lost to denitrification.

Parameters

nitrate_contentfloat

The nitrate content of this soil layer (kg / ha).

denitrification_rate_coefficientfloat

Rate coefficient that regulates denitrification in this layer of soil (unitless).

temp_factorfloat

The nutrient cycling temperature factor of this soil layer (unitless).

organic_carbon_fractionfloat

The fraction of this soil layer that is made up of organic carbon, in the range [0, 1.0] (unitless).

Returns

float

The amount of nitrate that is denitrified in this soil layer (kg / ha)

References

SWAT Theoretical documentation eqn. 3:1.4.1

Notes

This calculates the fraction of nitrates lost to nitrification as nitrification factor, and bounds it to be in the range [0.0, 1.0]. 0 is the minimum because a negative denitrification factor would indicate nitrous gases turning back into nitrate, which is not an operation that is handled by this module. 1 is the maximum because it is physically impossible to remove more nitrate than there is in the soil.

_calculate_nitrate_effect(nitrate_content: float) → float

Calculates the effect that the soil nitrate level has on the ratio of nitrous oxide to dinitrogen in denitrified nitrates.

Parameters

nitrate_contentfloat

Amount of nitrates (ug N / g soil).

Returns

float

Effect of the soil nitrate level on the ratio of nitrous oxide to dinitrogen (unitless).

Notes

The equation here differs from what was published in Parton et al, [1]. During implementation it was discovered that the equation they published was producing invalid results due to a missing pair of parentheses.

References

[1]

Parton, W. J., et al. “Generalized model for N2 and N2O production from nitrification and denitrification.” Global biogeochemical cycles 10.3 (1996): 401-412.

_calculate_carbon_effect(carbon_respiration: float) → float

Calculates the effect that the soil carbon respiration has on the ratio of nitrous oxide to dinitrogen in denitrified nitrates.

Parameters

carbon_respirationfloat

Carbon respiration from the soil layer (kg / ha).

Returns

float

Effect of the soil carbon level on the ratio of nitrous oxide to dinitrogen (unitless).

References

_calculate_moisture_effect(water_filled_pore_space: float) → float

Calculates the effect that the moisture level has on the ratio of nitrous oxide to dinitrogen in denitrified nitrates.

Parameters

water_filled_pore_spacefloat

Fraction of pore space that is occupied by water in the soil layer (unitless).

Returns

float

Effect of the soil carbon level on the ratio of nitrous oxide to dinitrogen (unitless).

Notes

If the water-filled pore space is 0, then the moisture effect is 0.0.

References

_calculate_pH_effect(pH: float) → float

Calculates the effect that the soil pH has on the ratio of nitrous oxide to dinitrogen in denitrified nitrates.

Parameters

pHfloat

pH of the soil layer.

Returns

float

Effect of the soil carbon level on the ratio of nitrous oxide to dinitrogen (unitless).

References

_calculate_partitioning_factor(nitrate_effect: float, carbon_effect: float, moisture_effect: float, pH_effect: float) → float

Calculates the factor used to determine the ratio of nitrous oxide to dinitrogen.

Parameters

nitrate_effectfloat

Effect of the nitrate level (unitless).

carbon_effectfloat

Effect of the carbon level (unitless).

moisture_effectfloat

Effect of the moisture level (unitless).

pH_effectfloat

Effect of the pH (unitless).

Returns

float

Factor used to partition nitrified nitrates into nitrous oxide and dinitrogen.

References

_calculate_nitrous_oxide_emissions(denitrified_nitrates: float, partitioning_factor: float) → float

Calculates the quantity of denitrified nitrates that are nitrous oxide.

Parameters

denitrified_nitratesfloat

Amount of nitrates that have been denitrified (kg / ha).

partitioning_factorfloat

Factor used to determine how much of the denitrified nitrates are nitrous oxide (unitless).

Returns

float

Amount of nitrous oxide emissions (kg / ha).

References