Cookes Plains Gypsum

Gypsum (calcium sulphate) when applied to soil dissolves in rain and or irrigation water and interacts with the fine clay particles.

This interaction improves soil structure making the clay more stable when wet and reducing the tendency of soil surfaces to set hard when dry.
Sloppy mud from the untreated area (above) contrasts with well-structured friable soil after a gypsum application.

Water will seldom pond on treated areas because of much improved water infiltration.
Makes soil more friable making cultivation easier, and cost effective. With the improved germination, run-off is minimal, reduces erosion.
Gypsum will maintain soil structure by inhibiting dispersion. It is the calcium in gypsum which replaces sodium in the soil, consequently crusting is reduced.
Supplies a cheap and effective source of sulphur without affecting soil pH.
Cooke Plains Gypsum passes through a 2mm screen and has a very low sodium content.

The deposit borders the Eastern reaches of Lake Alexandrina, a former tidal lake at the mouth of the River Murray. Swamps extending eastwards from the present lake beyond Cooke Plains were flooded during the last period of high sea level, and subsequent evaporation deposited Crystalline Gypsum which was then blown by prevailing winds into a series of Dune Ridges 150-500m wide and up to 12 metres high over a length of 3 kms along the North Eastern extremity. The dunes are made up of white flower Gypsum (Gypsite) covering seed Gypsum (Gypsarenite), which is the main type distributed. There are substantial shallow layers below swamp level and the water table. Workable area was estimated by the Mines Department to be in excess of 3 Million Tonnes.