Rosemount Estate, Gulgong. II "Cumbandry"

SITE EVALUATION AND VARIETAL MATCHING IN THE GULGONG AREA, NEW SOUTH WALES

II. THE "CUMBANDRY" AREA

In a follow-up to the "Woolloomooloo" project, viticulturalists from Rosemount Estate (by this time part of Southcorp Wines Limited) commissioned Terroir Australia to assess the viticultural suitability of a large area of land that it had acquired, close to its first-established Gulgong area vineyards at "Cumbandry", southeast of Gulgong, NSW.

The land had previously been used mostly for cattle grazing, with some mixed crop production. Most of the soils appeared to be suitable for wine-grape production, although some of the lower-lying areas appeared to suffer from relatively poor drainage. Average elevation is about 480 metres AMSL, and slopes generally face northeast to east.

As in the "Woolloomooloo" example, extensive use was made of high-resolution airborne radiometric data (see explanation in Petaluma page), as shown in the image below. Again, this approach revealed a complex interplay between soils formed on various substrates, including granitic, volcanic and two contrasting types of sedimentary bedrock, colluvial material derived from these rocks, and broad areas of mixed alluvium.

	FALSE-COLOUR RADIOMETRIC IMAGE OF THE "CUMBANDRY" AREA, GULGONG, NSW

	EXPLANATION Solid bright red - 'granite' (monzodiorite), and thin soils on monzodiorite; Solid dark red - basaltic to andesitic volcanic rocks; thin soils on volcanic rocks; Bright greenish blue - shaly/slaty sedimentary rocks; thin soils on these rocks. Mixed/mottled red-and-blue tones correspond to: soils on mainly sedimentary rocks (2) adjacent to solid red (hilltop) areas; soils on colluvium, alluvium derived from monzodiorite (centre) & mixed sources. Mottled and/or dark blue/greenish-blue tones, and green to dark blue tones in the right-hand side of the image (derived from low-resolution Geoscience Australia data) correspond to soils on alluvium & colluvium derived mainly from sedimentary rocks. Very dark, rounded areas in the centre-left and lower parts of the image are where the aircraft gained altitude to clear clumps of trees and the gamma-ray signal was attenuated. Areas under consideration for vineyard establishment are bounded by thin black (portion boundary)and/or yellow (fence) lines.

These 'categories' of radiometric signature are much more objectively identified and easily visualised by means of supervised classification* of the primary data, as illustrated in the image below.

CLASSIFICATION OF RADIOMETRIC DATA, "CUMBANDRY" AREA, GULGONG, NSW

EXPLANATION

Red - exposed "granite" (high-potassium monzodiorite) and high-K andesite; very thin soils on high-K monzodiorite and high-K andesite;

Orange - thicker soils rich in material derived from high-K monzodiorite and high-K andesite (trachyandesite);

Yellow - well-drained, thick soils formed from material of mixed monzodiorite + trachyandesite ą sedimentary-rock origin;

Lime green - well-drained, thick soils formed from material of mixed monzodiorite-trachyandesite origin;

Bluish green - less well-drained soils of mixed monzodiorite-trachyandesite and monzodiorite-sedimentary rock origin;

Deep blue - clay-rich soils on alluvium derived mainly from sedimentary rocks;

Grey - damp/wet clays mainly on alluvium/colluvium derived from sedimentary rocks, monzodiorite and trachyandesite;

White - no high-resolution data.

Green lines circumscribe areas of native trees.

SCALE: EACH DIVISION ON THE SCALE BAR IS 100 METRES.

Information from the two images above was used to produce a preliminary soil interpretation which was then used as a guide for targeting ground observations. These observations - mostly from hand-auger holes drilled to an average of 1 metre - were then used to compile the final soil map, reproduced below.

SOIL MAP SUPERIMPOSED ON AERIAL PHOTOGRAPH, "CUMBANDRY" AREA, GULGONG NSW

	EXPLANATION [Scale bar ticks are 100 m apart]	Straight black lines - Fences/fence lines Solid brown lines - gravel roads Dashed brown lines - tracks, driveways Grey line - Railway line Blue areas - dams, ponds Numbered dots - Soil sample points White stippled areas - soils with relatively low pH Green stippled areas - tree planting recommended
	Red curved lines - Soil-type and/or rock-type boundary Black curved lines - Soil-type boundary Blue curved lines - Soil-type and/or water- content boundary Dashed black line - Fault or inferred fault line

Dark areas outlined in blue are areas of periodically waterlogged black, clay-rich soils. In these areas, the water table is frequently very high, and a calcrete layer is forming at depths of between 50 and 70 cm.

Areas where tree planting was recommended are graded as first priority (dense green stipple) and second priority (less-dense stipple). Planting of native tree species (in particular, E. camaldulensis) was recommended as a measure to reduce groundwater accumulation in lower parts of the landscape (the "black soil" areas) by intercepting potential runoff and using groundwater in the principal recharge areas through vegetative growth and transpiration of a deep-rooted species.

The soil map, and an accompanying report describing the soils in detail and making recommendations as to grape varieties suited to each soil 'type', were used by Southcorp Wines viticulturalists to lay out new vineyards and decide their varietal makeup. Planting has been completed, but none of the new vineyards is yet in commercial production.

* Radiometric signatures from areas of known geology and/or soil type are used to construct a complex formula, or algorithm, which classifies each data pixel and assigns it a colour. [ back ]

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