Soils Overview

Much of the Research Farm consists of basaltic soils developed from underlying basalt. These usually have about 10-15 cm of clay loam at the surface, below which there is a sharp change to a red-brown to grey clay subsoil, which is in turn underlain by a yellow-grey calcareous clay containing weathered basalt at lower depths. Basalt ‘floaters’ are common at various depths in the soil profile and parent basalt is often within a metre of the surface. In some area the surface soil may also be clay and cracks will open up during dry periods. Subsoils in basalt areas are typically vertic – exhibiting significant shrinking and swelling during wetting and drying cycles. These soils are typically classified as Vertic Brown & Grey Sodosols using the Australian Soil Classification. In lower-lying areas and depressions, cracking clay soils (Vertosols) can occur.

In the western and southern parts of the Research Farm, soils are derived from deltaic deposits of alluvium that filled an ancient valley of the Werribee River. These sediments are weathered products derived from basalt as well as more sandy materials (e.g. from Tertiary sediments). Commonly these soils have about 15 – 25 cm of brown fine sandy clay loam surface soil, abruptly overlying a red to reddish-brown clay subsoil. From about 50 cm depth, various brown, pale brown or yellow light clays to fine sandy loams with varying amounts of carbonate segregations. At depths of between 1 – 2 metres (and occasionally deeper) these horizons are in turn underlain by mottled brown and yellow-grey heavy clay which may extend to depths of over 5 metres. These soils have previously been referred to as red-brown earths and are similar to soils in the Shepparton irrigation region. They are mainly classified as Red Sodosols using the Australian Soil Classification.

Information taken from groundwater bores around the Research Farm show that basalt is usually encountered at between 5-13 metres below the surface. On one bore site near the Research farm entrance, coarse sand and gravels were encountered at depths of between 8.5 to 10.5 metres (overlying basalt), and at a nearby bore, river pebbles were encountered from 9-10 metres depth overlying basalt.

References

Maher, J.M. and Martin, J.J. (1979). Soil and Land Survey of the State Research Farm Werribee. Project Series No. 42. Department of Agriculture.

Sargeant, I.J. (1998). Geomorphology of Wyndham. Unpublished Report for Wyndham City Council.

Skene, J.K.M. (1954). Irrigated Soils of Werribee Research Farm and District. Unpublished Report. Department of Agriculture.