Grains Research and Development

Clay delving

Clay delving is a technique used in sand-over-clay soil types where the clay is within the top 60cm. The delving implement penetrates the soil and breaks into the clay pan bringing clods of clay to the surface. The clay rich subsoil is then incorporated back into the water repellent surface sand.

Clay particles are less than two micron in size and therefore have a greater ‘wettable’ surface area than sand particles. Clay does not increase the water holding capacity of the soil by changing the matric potential, but allows more of the soil to wet-up. See also clay spreading.

The increased ‘wettable’ surface area in the topsoil by clay delving therefore has implications for seed germination and plant establishment coupled with a deep ripping effect, the combination of which can greatly benefit yield.

Clay delving can be expensive (about $150-200 a hectare) but it is a one-off amelioration technique and the benefits of clay delving and clay spreading has been shown to last for more than 10 years.

A tractor pulling a clay delving frame. A close up of the soil surface after clay delving, showing a mixed and broken surface.
Source: Julianne Hill, DAFWA and RAIN

A close up of clay delving tines.
Source: Julianne Hill, DAFWA and RAIN