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Dairy types and N, P and GHG losses

Description

A table and spatial layer of dairy types and their associated loss rates for N, P and greenhouse gases.

 

Date: November 2023 Version: v2

Owner: AgResearch

Contact: Tony van der Weerden (AgResearch)

 

Link to report / paper

Layer of dairy typologies

Table of N, P and GHG losses

Smith C, van der Weerden T, Selbie D. 2023. Quantifying co-benefits and trade-offs of mitigation measures to improve dairy farm N and P losses to water on greenhouse gas emissions from New Zealand dairy systems. J. New Zeal. Grasslands, (accepted).

 

Preview Image

 

Dataset attributes

Spatial extent North Island and South Island of NZ
Spatial resolution Soil data from S-map and FSL is used, Slope derived from a 15m DEM (20m contours), climate data
Temporal extent Data represents the 2019-2020 production year, based on DairyBase data
Temporal resolution Annual loss rates
Evaluation method (Validation) Expert assessment
Evaluation result (Numeric)
Evaluation result (Categorical)
Uncertainty method
Uncertainty data format (Numeric)
Uncertainty data format (Categorical)

 

Methodology

Farm nutrient budgets used previously by Monaghan et al. (2021), were updated to the latest version of the Overseer® Nutrient Budgeting software (version 6.5.0), hereafter referred to as Overseer.
In addition, certain management and production inputs were updated to better represent current farm systems for the 2019-2020 production year using data from DairyNZ DairyBase baseline farm records. Where existing Overseer files were unavailable, new Overseer nutrient budget files were generated using the climate, topography and soil properties typical for that type.
Refer to Smith et al. (accepted - link below) for further information on the development of the dairy typology classification system. Farm management inputs were obtained from the DairyBase files where these were available.

Three files were created for each dairy type:

  • A base file representing a typical average farm for that typology, one representing a higher intensity farm and one representing a lower intensity farm. Typically, the three intensities equated to farm systems 2, 3, and 4, with the occasional system 1 or 5 depending on the dairy type.
  • Nitrogen losses (kg N per ha per year) modelled by Overseer account for N run-off and leaching below the root zone from both livestock urine patches and from other non-urine sources such as fertiliser, or soil mineralisation.
  • Phosphorus losses (kg P per ha per year) modelled by Overseer relate to both overland runoff (main loss process) and leaching below the root zone.
  • Greenhouse gas emissions are split into the short-lived GHG methane (CH4) and long-lived GHGs (nitrous oxide (N2O and carbon dioxide (CO2)), thereby aligning with the suggested methodology for domestic reporting of farm-scale GHG emissions (He Waka Eke Noa, 2022). Methane emissions are reported as kg CH4 per ha per year, whereas long-lived gases are reported as CO2 equivalents (kg CO2e per ha per year), where N2O is converted to equivalent CO2 emissions using the 100-year time horizon global warming potential of 298 kg CO2-equivalent per kg N2O (Forster et al. 2007).

References:

Forster P, Ramaswamy V, Artaxo P, Berntsen T, Betts R, Fahey DW, Haywood J, Lean J, Lowe DC, Myhre G, et al. 2007. Changes in atmospheric constituents and in radiative forcing. In Climate Change 2007: The Physical Science Basis; Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change; Cambridge University Press: Cambridge, UK; New York, NY, USA, 2007; p. 996

He waka eke noa, 2022. Recommendations for pricing agricultural emissions: Report to Ministers. He Waka Eke Noa Primary Sector Climate Action Partnership. Wellington, New Zealand. p. 84

Monaghan RM, Manderson A, Basher L, Smith LC, Burger D, Meenken E & McDowell R. 2021. Quantifying contaminant losses to water from pastoral landuses in New Zealand I. Development of a spatial framework for assessing losses at a farm scale, New Zealand Journal of Agricultural Research, 64:3, 344-364, DOI: 10.1080/00288233.2021.1936572

Smith C, van der Weerden T, Selbie D. 2023. Quantifying co-benefits and trade-offs of mitigation measures to improve dairy farm N and P losses to water on greenhouse gas emissions from New Zealand dairy systems. J. New Zeal. Grasslands, (accepted)

 

Fitness for purpose / limitations

This table indicates whether the dataset is suitable for different types of questions at different scales.

Note: Users should carefully consider their purpose as this dataset may not be suitable.

Operational Absolute Relative Screening/scoping
Block/farm No No No No
Multi-farms(5+) No No No No
Catchment No No No Maybe
National/regional Maybe Maybe Yes Yes
Caveat(s) Rainfall data used for developing dairy types is limited to three categories, which is too coarse for determining losses at scales equivalent or smaller than catchment. The modelled output relies on the accuracy of the Overseer model for dairy systems, while the dairy management data is based on DairyBase data for the 2019-2020 production year. No data exists for dairy type 'Irrigated + Easy + Poorly Drained' (number 20) due to the absence of Dairybase data for this combination of attributes. Dairy types Irrigated + Easy + Well Drained (number 22) and Irrigated + Easy + Light (number 24) were modelled as a single type due to the relatively small areas of each; type was modelled using Well drained soil. GHG losses do not include emissions from raising youngstock.

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