How Gypsum works

Gypsum is used to improve the structure of sodic, hardsetting and surface crusting soils. The high levels of Sodium (Na) in these soils cause the clay particles to disperse, thereby degrading the soil structure, causing soil instability.

Soils with dispersive clays can be ameliorated by adding gypsum to flocculate (stabilise) the clay particles.  This works in the following way:

  • Calcium from gypsum replaces Sodium on clay particles, stabilising soil structure.
  • Clay particles flocculate and remain flocculated when wet.
  • Flocculated clays allow more water to infiltrate the soil profile, reducing runoff and erosion.

Which soils are responsive to Gypsum?

  • Soils that are hard when dry or have a surface crust.
  • Soils which seal after rainfall and have a low water
    infiltration and high run-off.
  • Soils that are difficult to cultivate because they are too hard or too wet.
  • Soils that produce patchy crop emergence and patchy early growth, particularly in poor seasons.
  • Soils that become sticky or non-trafficable after
    light rainfall.

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