Stock density

Waikato Regional Council obtains information on the number and type of stock on each farm in the Waikato region from the AgriBase® database. AsureQuality Limited developed, and now maintains, AgriBase®.

We estimate the area of pastoral land on each farm from the Land Cover Database version 5.0 (LCDB v5.0).

Waikato Regional Council measures stock density across the Waikato region.

AsureQuality Limited maintains AgriBase® records through:

• routine contact with farmers
• monthly updates of property changes from Quotable Value New Zealand.

Waikato Regional Council purchases AgriBase® with data updates every six months.

The LCDB is generally updated every 5 years by Landcare Research New Zealand Ltd. LCDB v5.0 was funded by a consortium of central government agencies, including the Ministry for the Environment, the Ministry for Primary Industries, and the Department of Conservation. Waikato Regional Council’s monitoring of pastoral area is dependent on the release of updated LCDB datasets.

Development of the AgriBase® system began in late 1988. National data capture began in 1993. Waikato Regional Council purchased a snapshot of the AgriBase® database every six months since 2008.

The LCDB v5.0 data used in the derivation of this indicator update was primarily derived from satellite imagery acquired during the summer of 2018/19. More information on the Land Cover Database is available here.

Waikato Regional Council uses:

• AgriBase® data on stock numbers to calculate the number of stock units on each farm and the land area of the farm.
• LCDB v5.0 to calculate the area of pastoral land on each farm.

Waikato Regional Council calculates stock density for each farm by dividing the total stock units on the farm by the total area of pastoral land. Following this process for the whole region requires a series of steps, outlined below.

1. 1. Due to the way in which the AgriBase® dataset is constructed, we first pre-process the data using GIS tools to avoid overestimating stocking rates. A 'flattening' process is used to area proportion AgriBase® recorded stock numbers to the available LCDB v5.0 pastoral extent. This is necessary because AgriBase® records the total area of each farm, which may include non-pastoral land.

   2. We work out the total stock units for each farm by converting the animals into common stock units (or ewe equivalents) and calculating a farm total. We use the AgriBase® stock data and the AsureQuality stock unit conversion factors for this task (which you can view below). We also use information from AsureQuality about the typical distribution of stock classes expected on a ‘standard’ farm. This allows us to estimate stock density in more detail for each farm type.

   3. We classify stock density on each farm into one of the five classes shown below.

      
      Stock density classes

      Stock density class (stock units/ha)	Farm type where stock density class typically observed	Cows per hectare equivalent
      Less than 10.5	Sheep farms	Less than 1.5
      10.5 to 17.5	Beef farms and lower stocked dairy farms	1.5 to 2.5
      17.5 to 24.5	Mid-range of dairy farms	2.5 to 3.5
      Greater than 24.5	Higher stocked dairy farms	Greater than 3.5
      Stock density not calculated	Reliable data not available

   4. We identify which of the eight major water catchment zones in the Waikato region each farm occurs within. This helps us determine how stock density might be affecting water quality in different parts of the region. For example, river water quality monitoring shows that water quality for ecological health is poorer in the Waihou/Piako and Waipā water catchment zones, where stock density is highest.

   5. We calculate the number of farms in each stock density class for each water catchment zone.
      
      
   6. We create a map showing the distribution of stock density in the Region. We map each farm in one of the five stock density classes listed in Table 1.

Stock unit conversion factors and typical distribution of stock classes

For example, the total stock units for dairy stock were calculated using the following formula:

Dairy Stock Units = (0.731 x Dairy numbers x 7) + (0.245 x Dairy numbers x 4.25) + (0.024 x Dairy numbers x 5.5).

To calculate stock density from AgriBase® data, Waikato Regional Council uses the AsureQuality stock unit conversion factors. These factors are used to work out feed budgets in the agricultural industry.

For information on data quality (lineage, positional accuracy, attribute accuracy, logical consistency and completeness) see the updated metadata for the LCDB.

A number of sophisticated quality assurance procedures (including statistical, SQL query, visual/spatial inspection) have been developed by AsureQuality Limited to verify the incoming data for AgriBase®.

Footnotes
1. The LCDB v5.0 dataset is a “public good” data set created by Landcare Research New Zealand Ltd and available under Creative Commons Attribution V4.0 International Licensing.
2. AgriBase® data is a product of AsureQuality.

AgriBase® data cannot be used to calculate farm-based stock densities for all farms in the Waikato Region. This is because not all land parcels in the database are linked to a specific farm.

The AgriBase® data purchased by Waikato Regional Council does not discriminate between the age classes of the animals. The equation used to calculate total stock units is a generalised one that uses typical stock classes on farms.

• The data in this graph were collected by AsureQuality Limited, as at June 2018.
• View our map of stock density [JPG, 747 KB] in the Waikato region.