Soil types of the McLaren Vale Wine Region
Sand (11% of the McLaren Vale Wine Region - mainly located in Blewitt Springs and McLaren Flat)
Topsoil: sandy with a gravelly and bleached horizon.
Subsoil: yellow and red sandy clay loam to clay.
Drainage: well drained but seepage can occur in the gravel layer above the clay, creating a subsoil waterlogging problem.
Natural fertility: Low. Cation capacity is low. Organic carbon is often very low.
Salinity and sodicity issues: generally not an issue but localised salinity can be introduced by seepage water.
Black Heavy Clay - "Bay of Biscay" (7% of the McLaren Vale Wine Region)
Topsoil: black cracking clay (sometimes self-mulching) with increasing amounts of soft carbonate.
Subsoil: black clay grading to grey-green heavy clay.
Drainage: imperfect and leaching of salts can be an issue.
Natural fertility: deep and inherently fertile but difficult to work, especially when wet.
Salinity and sodicity issues: are possible in these soils with some naturally saline and/or sodic. Irrigating with marginal water can make these problems worse.
Other: boron toxicity problems are possible in these soils.
Loam over red clay - "Urrbrae Loam" (26% of the McLaren Vale Wine Region)
Topsoil: silty loam to silty clay loam.
Subsoil: red clay with increasing soft carbonate at depth.
Drainage: moderately well drained.
Natural fertility: deep and inherently fertile.
Salinity and sodicity issues: soils are generally not naturally saline or sodic but problems can occur due to the accumulation of salt from irrigation water. Often vineyards with these soils are irrigated with bore water.
Other: Main limitations are related to poor structure due to the high silt content of the surface soils and susceptibility of the upper part of the profile to compaction. These soils compact with repeated tractor driving.
“Terra Rossa” like soil (20% of the McLaren Vale Wine Region)
Topsoil: clay loam increasing clay content.
Subsoil: highly calcareous clay loam to clay.
Drainage: well drained.
Natural fertility: moderate to high fertility.
Salinity and sodicity issues: SImilar to Urrbrae soil, salinity or sodicity problems can occur due to the accumulation of salt from irrigation water.
Sandy loam over brown clay - "Gilgai" (24% of the McLaren Vale Wine Region)
Topsoil: grey massive sandy loam grading to bleached loamy sand.
Subsoil: brown mottled poorly structured clay with soft carbonate at depth.
Drainage: imperfectly drained.
Natural fertility: shallow with moderate fertility.
Salinity and sodicity issues: soils are not naturally saline but due to the poor drainage and sodic nature of the clay, salts can accumulate in the top clay layers and cause salinity issues.
Other: Water can perch on the poorly structured subsoil clay saturating the upper profile for up to several weeks after prolonged rain.
NOTES BY JAMES HOOK - DJ's