National Soils Database

More about the National Soils Database

The NSD is a 'point' database containing descriptions of about 1500 New Zealand soil profiles, together with their chemical, physical, and mineralogical characteristics

Testing the texture of the soil at the Puhoi soil pit. Image - Dave Palmer

Testing the texture of the soil at the Puhoi soil pit, Northland. Image - Dave Palmer

The information is obtained from excavated pits usually up to 1.5 m deep but sometimes deeper, from which the soil scientists collect samples for chemical and physical analyses. Sometimes drilling down to 15 m or so is needed for sampling deep layers of volcanic ash.

Each soil profile pit (the data or sampling point) can take up to a day to describe. More than 200 individual pieces of data are either collected in the field or from the laboratory analyses. It has taken many years to build up the database, and the New Zealand component alone now represents about $15 million of information.

The full NSD contains information on the following aspects:

  • The site
  • Soil horizons
  • Soil chemistry
  • Soil physical analyses
  • Mineralogical (XRF) analyses
  • Soil/void relationships
  • Water retention measurements

Data availability varies from site to site, and not all sites have the full set of data.

The data are invaluable for understanding sustainable land management options:

  • Soil acidity, organic matter content, clay or silt content, toxicity, and phosphate retention may affect nutrient levels and their availability to plants.
  • Soil drainage, depth to water table, depth to an impermeable layer, gravel content, water-holding capacity, acidity, and mineralogy can indicate whether a soil is suitable for the intended use, e.g. particular crops, septic tank disposal fields, cemeteries, or sports fields.

To be profitable, primary production needs to incorporate information relevant to land use planning. Soil type has important implications for making management decisions, e.g. the type and extent of drainage systems required to grow particular crops, suitable irrigation regimes (amount, rate, and frequency of water), and fertiliser regimes.