101 Questions Answered
Identifying calcareous soil
Calcareous soils contain lime (calcium carbonate).
You will be able to seesmall pieces of lime (<2 mm) on the surface or in the topsoil.
They are sometimes called Mallee loams or calcareous earths. Most calcareous soils are ‘mild’, meaning they have about 2 – 15% lime in thesurface layers. Parts of South Australia have highly calcareous soils whichcontain 50% or more lime. You can have the amount of lime tested at a laboratory with a test forinorganic carbon, which measures carbonates such as calcium carbonate(lime) and bicarbonates. In South Australia, a significant proportion of thetotal inorganic carbon will be lime. You can also test the soil yourself to see if lime is present, which requiresdilute hydrochloric acid. This won’t tell you how much, but roughly, the moreit fizzes, the more lime there is.
The GRDC has made a video with instructions:
Calcareous soils have an alkaline pH and are often saline and sodic at depth.Soil test results showing a high pH and/or salinity, or a high phosphorusbuffering index (>80) are clues you have calcareous soil.
