ANZLIC Metadata Profile: An Australian/New Zealand Profile of AS/NZS ISO 19115:2005, Geographic information - Metadata
Metadata Standard Version
1.1
Identification Info
Data Identification
Citation
Citation
Title
Nitrate Nitrogen leaching from livestock 2017
Date
Date
Abstract
Raster layer with 100m * 100m pixels, Each pixel represents the estimated nitrate-N leached in kg/ha/yr. This layer contains all nitrate leaching estimated from dairy cows.
Purpose
To understand the pressure on water quality from nitrate N leaching from selected land-based activities
• The map should not be used to infer leaching rates for individual farms as average farming practices are assumed and actual stock numbers per farm were not available. • The spatial extent of nitrate leaching should be considered as an update from EA 2015 and Our freshwater 2017, and should not be used for comparing time differences between this one and previous versions.
Use Constraints
Restriction Code
otherRestrictions
Other Constraints
• The map should not be used to infer leaching rates for individual farms as average farming practices are assumed and actual stock numbers per farm were not available. • The spatial extent of nitrate leaching should be considered as an update from EA 2015 and Our freshwater 2017, and should not be used for comparing time differences between this one and previous versions.
Spatial Representation Type Code
grid
Representative Fraction
Denominator
Integer
50000
Language
eng
Character Set
Character Set Code
utf8
Topic Category Code
farming
Topic Category Code
inlandWaters
Topic Category Code
environment
Extent
EX _ Extent
Geographic Element
EX _ Geographic Bounding Box
167.376964179.625229-47.328567-33.949210
Data Quality Info
DQ _ Data Quality
Scope
DQ _ Scope
Level
Scope Code
series
Level Description
Scope Description
Other
series
Lineage
LI _ Lineage
Statement
The map of nitrate-N leaching was produced by combining a map of animal numbers and estimates of nitrate leaching rates per animal type.
Animal numbers were estimated by distributing region-level totals (Statistics New Zealand, 2017a) according to land use and stock-carrying capacity (Landcare Research 1992). We utilized the latest available AgriBaseTM (AsureQuality 2018) land use data from May 2018 and LCDB version 4.1 (Landcare Research 2015) land cover data from 2012 for our spatial modelling. In-house scripts and routines were implemented across the AgriBaseTM to remove errors and defects. Stocking rate normalization to national stock numbers was based on the Agricultural Production Census 2017 at the regional authority level (Statistics New Zealand 2017a). The census data were mapped to 2017 regional boundaries (Statistics New Zealand 2017b). Nitrate-N leaching rates per animal type were estimated for 100 unique soil and climate combinations in New Zealand (i.e. LENZ level II: Leathwick et al. 2003) using OVERSEER® (AgResearch 2011). We took into account two modifiers: • Shallow soils that have twice as much nitrate leached than deep soils. • Irrigated land that will have different nitrate leaching rates for dairy cows. To identify irrigated areas in our analysis, we rasterized the spatial data set prepared by Dark et al. (2017). In the absence of a more robust method, nitrate leaching on horticultural and arable land was set to one and two times that estimated for sheep at stock-carrying capacity respectively (Lilburne et al. 2010).
AgResearch 2011. OVERSEER®. Available from www.overseer.org.nz. AssureQuality New Zealand Ltd, 2018. AgriBaseTM. Dark A, Birendra KC, Kashima A 2017. National Irrigated Land Spatial Dataset: Summary of methodology, assumptions and results. Ministry for the Environment, C17042-1. Christchurch, Aqualinc Research Limited. Landcare Research 1992. New Zealand Land Resource Inventory. Landcare Research 2015. LCDB v4.1 – Land Cover Database version 4.1, Mainland New Zealand. https://lris.scinfo.org.nz/layer/48423-lcdb-v41-land-cover-database-version-41-mainland-new-zealand (accessed 06/11/2017) Lilburne L, Webb T, Ford R, Bidwell V 2010. Estimating nitrate-nitrogen leaching rates under rural land uses in Canterbury. Report No R10/127. Christchurch, Environment Canterbury. 37 p. Statistics New Zealand 2017a. Agricultural production statistics: June 2017 (final). https://www.stats.govt.nz/assets/Uploads/Agricultural-production-statistics/Agricultural-production-statistics-June-2017-final/Download-data/agricultural-production-statistics-jun17-final-tables-v2.xlsx (accessed 21/05/2018) Statistics New Zealand, 2017b. Geographic boudary files. http://archive.stats.govt.nz/browse_for_stats/Maps_and_geography/Geographic-areas/digital-boundary-files.aspx (accessed 06/11/2017)
The models were run using in-house scripts implemented within the ERDAS Imagine GIS software suite. The results for the individual land-use types considered were added to derive the map of total nitrate-N leached at national scale.
