Waikato Regional Council monitors soil quality to provide information about how particular land uses are affecting soils in the long-term. Some land uses and land management practices may affect soil properties and reduce soil quality over time.
Some reductions in soil quality, such as lost organic matter, can take many decades to remedy. This can mean that future landowners are unable to grow crops or pasture of the same quality or need to use greater amounts of fertiliser to achieve the same result as previously.
The better the measured soil characteristic matches the guideline value for its current land use, the better the soil quality. Scores for individual soil quality characteristics are grouped together for each land use to give the percentage of the Region’s land area that meets (or fails) soil quality guidelines. This is expressed as satisfactory soil quality and soil quality that is ‘of concern’.
We can get an idea of what the soil quality issues are for certain land uses by looking at which key soil quality characteristics don’t meet guideline values for that land use. For example, fertility imbalance and soil compaction are currently the main concerns identified for pastoral farming soils.
Good quality soils are those where key soil characteristics are in good condition for the current land use. Waikato Regional Council measures soil quality for four main land use types in the Waikato region:
About 10 per cent of the region's productive soils had satisfactory soil quality for their current land use in 2014. This compares with 13 per cent being satisfactory in 2008 and 10 per cent in 2003.
Nearly 95 per cent of the land under dairy farming has soil quality that is of concern, with excessively high fertility and soil compaction affecting about four-fiftths of the sites.
Similarly, more than 95 per cent of the land under drystock farming has soil quality that is of concern. Over half the sites have excessive fertility, while about a sixth of the sites have low fertility. Over three quarters of sites have soil compaction.
More than 80 per cent of the land under cropping and horticulture has soil quality that is of concern. Nearly three quarters of the sites have excessively high fertility. About two-fifths of the sites under cropping have loss of soil organic matter and low stability of aggregates.
About half of the land under forestry has soil quality measurements outside targets. About a third of sites are loose. Loose is the opposite of compaction and many of the region's soils are naturally loose. Loose soils can have a high erosion risk and foresters have to take special precautions when harvesting trees.
More detail on this indicator, including how and where Waikato Regional Council collects this information, is available in the Technical Information page.
The indicator will be updated every year to include any new sites, and re-measured baseline sites. Updates may also include any further development of the indicator.
Soil Scientist - Science and Strategy Directorate