Greater Wellington (GW) monitors soil quality as part of its State of the Environment programme, to meet the requirements of section 35 of the Resource Management Act (1991) and to provide information to measure Regional Plan policy effectiveness.

The soil quality monitoring programme consists of approximately 100 monitoring sites on a range of soils across the region under different land uses. The frequency of sampling is dependent on the intensity of the land use; dairying, cropping and market garden sites are sampled every 3-4 years, dry stock, horticulture and exotic forestry sites are sampled every 5-7 years, while indigenous vegetation sites are sampled every 10 years. This years’ report summarises monitoring results for native vegetation sites.

Monitoring objectives

  1. Provide information on the physical, chemical and biological properties of soils;
  2. Provide an early-warning system to identify the effects of primary land uses on long-term soil productivity and the environment;
  3. Track specific, identified issues relating to the effects of land use on long- term soil productivity;
  4. Assist in the detection of spatial and temporal changes in soil quality; and
  5. Provide information required to determine the effectiveness of regional policies and plans.

Monitoring indicators and benchmarking

Monitoring indicators are used to assess soil chemistry and fertility, and to understand soil physical condition. The indicators used are as follows:

Measured indicator values at each monitoring site are benchmarked against relevant guidelines for monitoring soil health. See the methods page for more information.

Note: No guidelines are currently established for soil on native vegetation sites. So, their indicator values are assessed against forestry land use ratings to get a general idea of soil quality. Note also that some 2022 sites are located in small remnants of native vegetation, and their soil quality may be influenced by adjacent land uses (e.g. spray drift from neighbouring properties). These notes will be addressed in the next round of sampling for native vegetation monitoring sites.

Monitoring sites and indicator breaches

Each monitoring site is shown by the map circles below, with the total number of indicators breached during the 2022 monitoring season displayed by colour of the circle – hover over the circle for more information. Drag and scroll on the map to move and zoom in on areas of interest, hover over each outlined area to see Whaitua (main river catchments), and use the top right checkbox to show/hide “LUCAS 16 landcover” classifications.