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Soil glossary

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This glossary explains some of the technical words about soil and the land used by Waikato Regional Council.

Aggregate

An aggregate is a lump of soil particles stuck together. How easily a soil breaks up into aggregates and the structure, size and shape of aggregates are defining characteristics of the soil.

Compaction

The destruction of soil structure by machinery (such as tractors or haulers) or by livestock.

Cultivation

Turning over or tilling the soil. Soil may be cultivated for pasture renewal, cropping or intensive cropping.

Erosion

A natural process caused by gravity, wind and water wearing away the soil surface and moving the soil from where it was formed. Erosion can be greatly accelerated by vegetation removal and unsuitable land use.

Microbial activity

The activity in the soil carried out by the tiny bacteria and fungi (microbes) that live in the soil. These microbes break down harmful chemicals (such as pesticides) and can increase the amount of nitrogen in the soil.

Mineral soil

A soil made up of mainly mineral material (compare with organic soil).

Organic matter

Organic matter is all the decayed/partially decayed plant and animal material in the soil.

Organic soil

A soil made up of mainly organic matter. Peat is an organic soil.

Pasture renewal

Replacing old pastures for increased productivity. This can be done by oversowing or undersowing new species, cropping and seeding or reseeding.

Plough pan

A compacted layer of soil that builds up below the soil surface as a result of ploughing or cultivation activities. The plough pan lets less water through than the soil above or below it.

Pugging

The destruction of soil structure by animal trampling of wet soil.

Subsoil

The soil underneath the topsoil.

Topsoil

The upper part of the soil, where most of the organic matter is found.

Versatile soils

Soil versatility is a measure of what uses a soil is best suited to. Very versatile soils are suited to a wide range of uses – including cultivation and cropping which are very demanding on soil.

Soil versatility considers:

  • the potential rooting depth of plants
  • how well the soil can withstand traffic (both vehicles and animals)
  • the potential loss of nutrients from the soil
  • the potential risk of erosion
  • the water deficit – whether there is enough water in the soil for plants
  • soil drainage.