climag.modvege_consumption

Functions for computing harvested and ingested biomass

References

[1] (1,2,3)

Jouven, M., Carrère, P., and Baumont, R. (2006). ‘Model predicting dynamics of biomass, structure and digestibility of herbage in managed permanent pastures. 1. Model description’, Grass and Forage Science, 61(2), pp. 112–124. https://doi.org/10.1111/j.1365-2494.2006.00515.x.

[2]

Kavanagh, S. (2016). ‘Feeding the Dairy Cow’, in Teagasc Dairy Manual. Teagasc, pp. 201–212. Available at: https://www.teagasc.ie/publications/2016/teagasc-dairy-manual.php (Accessed: 2 November 2022).

[3]

Broad, H. J. and Hough, M. N. (1993). ‘The growing and grazing season in the United Kingdom’, Grass and Forage Science, 48(1), pp. 26–37. https://doi.org/10.1111/j.1365-2494.1993.tb01833.x.

[4]

Eurostat (2022). Glossary:Livestock unit (LSU). Available at: https://ec.europa.eu/eurostat/statistics-explained/index.php?title=Glossary:Livestock_unit_(LSU) (Accessed: 2 November 2022).

climag.modvege_consumption.organic_matter_digestibility(ts_vals: dict[str, float], params: dict[str, float])

Organic matter digestibility

Parameters

ts_valsdict

Dictionary with intermediate time series values

paramsdict

Dictionary of model parameters

Returns

dict

Updated ts_vals dictionary

Notes

Organic matter digestibility of the green vegetative (GV) and green reproductive (GR) compartments. See Equations (9) and (10) in [1].

Digestibility varies among plant parts, with leaves usually being more digestible than stems. The differing digestibility of plant parts may explain why they are grazed selectively. Digestibility of green compartments decreases linearly with compartment age.

This function returns an updated ts_vals dictionary with:

• omd_gv: Organic matter digestibility of the GV compartment [dimensionless]

• omd_gr: Organic matter digestibility of the GR compartment [dimensionless]

climag.modvege_consumption.biomass_ingestion(ts_vals: dict[str, float], params: dict[str, float])

Biomass ingestion through grazing

Parameters

ts_valsdict

Dictionary of intermediate time series values

paramsdict

Dictionary containing of model parameters

Returns

dict

Updated ts_vals dictionary

Notes

The maximum amount of biomass available for grazing and/or harvesting for each structural compartment.

• Maintain the height of the residual biomass after harvest to the minimum residual grass height

• The bulk density is used to convert this height to the equivalent biomass amount. See [1], sec. “Harvested biomass”, Equation (19)

The maximum amount of biomass ingestible based on the stocking rate

• Ingestion takes precedence over harvesting

• The amount of biomass ingested per livestock unit per day is 13 kg DM LU⁻¹ based on average consumption data for dairy cows from [2] and the value used by [3]

• One livestock unit (LU) is equivalent to one dairy cow, based on [4]

The amount of biomass ingested in total for each structural compartment

• This is weighted according to the organic matter digestibility.

• Digestibility varies among plant parts, with leaves usually being more digestible than stems

• The differing digestibility of plant parts may explain why they are grazed selectively

Assumption: when grazed/harvested, 10% of the available biomass in each structural component is lost.

This function returns an updated ts_vals dictionary with:

• i_bm: The total ingested biomass amount [kg DM ha⁻¹]

• bm_gv: Updated standing biomass of the green vegetative compartment [kg DM ha⁻¹]

• bm_gr: Updated standing biomass of the green reproductive compartment [kg DM ha⁻¹]

• bm_dv: Updated standing biomass of the dead vegetative compartment [kg DM ha⁻¹]

• bm_dr: Updated standing biomass of the dead reproductive compartment [kg DM ha⁻¹]

climag.modvege_consumption.biomass_harvest(ts_vals: dict[str, float], params: dict[str, float])

Harvest biomass through a cutting event

Parameters

ts_valsdict

A dictionary with intermediate time series values.

paramsdict

A dictionary containing of model parameters

Returns

dict

An updated ts_vals dictionary

Notes

Harvest biomass through a cutting event at the end of the reproductive period. Maintain the height of the residual biomass after harvest to the minimum cut height. This height is calculated by using the bulk density. See [1], sec. “Harvested biomass”, Equation (19).

Assumption: during harvest, 10% of the harvestable biomass in each structural component is lost.

This function updated ts_vals dictionary with:

• h_bm: The total harvested biomass amount [kg DM ha⁻¹]

• bm_gv: Updated standing biomass of the green vegetative compartment [kg DM ha⁻¹]

• bm_gr: Updated standing biomass of the green reproductive compartment [kg DM ha⁻¹]

• bm_dv: Updated standing biomass of the dead vegetative compartment [kg DM ha⁻¹]

• bm_dr: Updated standing biomass of the dead reproductive compartment [kg DM ha⁻¹]