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Melbourne Soils | LC0081 |
Robert van de Graaff and Chris Wootton, Melbourne
June, 1996 |  |
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The soils of Melbourne are closely related to the underlying geological material on which they have formed.
This Landcare Note uses this relationship to divide Melbourne soils into 9 types
Please note:
- The soil types given are relatively broad groups which will vary somewhat across the geographic and climatic range.
- The boundaries between the soil types will generally not be at all distinct. Please expect quite complex intergrading in the vicinity of marked boundaries.
- Soil disturbance, and massive exporting and importing of soil materials have been common in many parts of the “built up” area of Melbourne.
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The nine soil types are as follows:
1. Red loams
These occur in the rolling to hilly country between Silvan and Monbulk, the upper parts of the Dandenong Ranges and the hill crests at Chirnside Park. They are probably the best soils in Melbourne being deep, friable and well structured. They are poor in plant nutrients and mildly acidic and hence will benefit from incorporation of organic matter, regular use of fertilizer and the occassional use of lime. Other features include:
- excellent drainage;
- low to moderate water holding capacity;
- soil digging very easy whether dry, moist or wet; non-sticky;
- soil structure allows extensive root development;
- shrinking and swelling is minimal;
- erodibility is low;
- suits wide range of plants.
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Example: Mooroolbark - Tertiary basalt
(Melways Map 37. K5)
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Dark brown friable loam, grading into
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Dark reddish brown friable clay loam, over
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Reddish brown or brown strongly weathered soft basalt.
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2. Brown loams over clay
These are highly regarded soils which have developed on the Older Basalts of the lower Mornington Peninsula. Grey brown friable loam topsoil materials overlies well-structured yellow red mottled clay subsoils. Fertilizers or manures should be used, and organic matter dug into the topsoil. Lime may be necessary to counteract acidity.
Other features include:
- good drainage
- good water holding capacity
- easily worked when moist, non-sticky, but soft when wet;
- soil structure allows good root development.
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Example Baldry's Crossing - Tertiary Older Basalt (Melways Map 256. L10)
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Grey brown friable loam, abruptly overlying;
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Yellow-red heavy textured clay, over;
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rock or decomposed basalt.
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3. Dark grey sand over clay
These soils are located in the gently undulating to f lat land between Kew and Mt. Waverley, and in a large triangular area bounded by Toorak, Cheltenham and Dandenong. The topsoil is a black to dark grey sand with a lot of organic matter, grading into light grey sand. It overlies a brown, red and gray mottled clay. They are also found in the Frankston - Mornington - Balnarring - Tyabb area but the topsoils are loamier and deeper. These soils are poor in plant nutrients and require the addition of organic matter and fertilizers or manures when producing crops. Lime may be necessary to counteract acidity.
Other features include:
- clay subsoil can impede drainage;
- suited to a large range of plants;
- topsoil easily worked whether dry, moist or wet
- non-sticky;
- in winter a perched watertable may occur above the clay, affecting drainage.
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Example: Kew - Tertiary sands
(Melways Map 45. J7)
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Black to dark grey sand; grading into
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Light grey sand, with slight yellow-brown mottling and a concentration of 'buckshot' (small iron stones) at depth; abruptly overlying
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Brown, red and grey, mottled compact clay; strongly weathered.
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4. Light grey loams over clay
Found in the north-eastern areas of Melbourne, which include: Kew to Croydon and from Bundoora to Rowville, the topsoil consists of a light grey loam with some stones or gravel. The topsoil overlies a compact yellow brown mottled clay subsoil with small and large angular stones often found at the junction. These soils are poor in plant nutrients and humus. Fertilizers or manures should be applied regularly and organic matter dug into the topsoil. Soil acidity may be corrected by the addition of lime. The addition of gypsum will usually improve soil structure.
Other features include:
- moderately well drained;
- moderate to low in water holding capacity;
- topsoil tends to set quite hard when dry and needs to be worked when moist; too soft when wet;
- good for a wide range of plants, however summer watering is essential for introduced, or non-native plants as the root zone holds restricted quantities of water;
- scattered rock fragments in the subsoil can cause problems for digging;
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Example: Bundoora - Silurian sandstones and sandstones (Melways Map 10. A9)
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Light grey loam, with some stones and gravel, abruptly overlying;
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Yellow brown mottled clay
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5. Gritty light grey loam over clay
These soils are formed on granite parent material occurring between Lysterfield and Hallam, Arthur’s Seat, Mt Martha and elsewhere. They consist of light grey gritty sandy loam, or loamy sand, over mottled yellow brown and grey clay. They are poor in nutrients and thus require the additions of organic matter and fertilizers. They are mildly acidic.
Other feature include:
- moderately well drained;
- low water holding capacity in topsoil, hence watering in summer is essential for many introduced plants;
- topsoil sets hard when dry and is moderately easy to dig when moist;
- non-sticky;
- waterlogging is common on lower slopes in winter and spring;
- prone to erosion by water;
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Example: Mt Martha - Granite
(Melways Map 150. G7)
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Light grey sandy loam; an abrupt transition to
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Yellow brown sandy clay with a blocky structure
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6. Dark loams, clays, local sands
These soils have developed on the flood plains and swampy areas of Melbourne. They consist of dark loams, clays and sands. They can be very good for a wide range of plants if they are adequately drained (ie watertable kept more than 1metre below the soil surface). Being low in plant nutrients, they benefit from additions of organic matter and fertilisers or manures.
Other features include:
- drainage rates vary across the soil type;
- if topsoil shows rusty mottling along old root channels it indicates very poor drainage;
- ranges from mildly acidic to neutral;
- sand and clay contents will vary depending upon position and level on the floodplain (ie youngest terrace or an old levee)
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Example: Banksia Park, Bulleen - Alluvial soil on Yarra floodplain (Melways Map 32. D5)
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Very dark grey brown silt loam to clay loam; grading into
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Grey brown silty clay loam to silty clay.
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7. Deep sands free of lime
These are deep grey brown sands over yellow grey, frequently with a layer of dark brown hard cemented sand ("coffee rock"). They occur in the sand-dune areas from Black Rock to Brighton, and along the coast of Port Phillip Bay, as far as Rye. They are extremely poor in nutrients. Addition of fertilisers or manures and especially organic matter will help increase the humus content and raise fertility. Lime also needs to be added to counter the mild to strong acidity. These soils are highly regarded for vegetable cropping in the Cranbourne region.
Other features include;
- rapid drainage
- very low water holding capacity, hence frequent but short waterings are required to avoid “washing out” nutrients;
- very easily worked, when wet, moist or dry;
- non-sticky;
- prone to erosion by wind;
- high water tables in some areas;
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Example Frankston East - Sand
(Melways Map 103. K8)
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Coffee coloured sand; extending into
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Yellowish brown to brown sand.
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8. Deep sands with lime
These soils occur between Cape Schanck and Sorrento, in rolling sand dune areas. They are deep and consist of grey to whitish sand that occasionally sit on top of a lime-cemented hard pan. The sandy topsoil contains a varying amount of lime and is lightly acid to alkaline. The subsoils are alkaline. Addition of organic matter and fertilisers or manure is highly beneficial.
Other features include:
- excellent drainage;
- very low water holding capacity, so frequent light-moderate watering is required;
- very easily worked when wet, moist or dry;
- non-sticky
- prone to erosion by wind
- limited range of lime tolerant and salt wind tolerant plants;
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Example: Sorrento - Aeolian, calcareous and siliceous dune sand (Melways Map 156. J9)
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Uniform dark grey medium sand;
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Yellow grey uniform sand.Over sand and calcarenite.
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9. Heavy clay on younger basalts
These soils occur extensively in the north-west of Melbourne, stretching from Altona to Thomastown and from Richmond to Broadmeadows. They are generally shallow dark and reddish brown heavy clays with a thin loamy topsoil. Outcrops of basalt rock are common and basalt floaters occur extensively. They benefit from the addition of organic matter. Gypsum can be used to improve soil structure.
Other features include:
- drainage very poor and causes waterlogging in wet weather;
- soils are very hard when dry and very sticky when wet, making them difficult to cultivate;
- slightly alkaline to slightly acidic;
- clayey soil and low rainfall limits the range of plants which can be effectively grown in it;
- clay dries very quickly in hot weather and can develop deep cracks. Large shrink-swell capacity which can cause cracks in walls and pavements.
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Example Darebin Park, Fairfield - Quaternary basalt
(Melways Map 31. D8)
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Very dark grey brown clay, fissured and hard when dry but sticky and plastic when wet; grading into
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Dark grey brown to brown heavy clay, coarsely angular blocky structure.
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Notes on soil descriptions used
Acidity:
Acidity is a measure of the reaction of the soil chemical environment. Soils are said to be neutral if they have a pH of 7, acidic if the pH is less than 7 and alkaline if they have a pH greater than 7. If a soil is excessively acid or excessively alkaline then plant roots have difficulty in obtaining nutrients and water.
Floaters:
Rocks and stones which occur irregularly within the soil profile.
Friable:
A friable soil is one which can be easily crumbled or broken up. A friable soil allows easy cultivation.
Hardpan:
The term hardpan refers to any compacted or cemented layer within a soil profile.
Humus:
That part of soil organic matter which has decomposed into soft dark coloured material without showing any of the original form of the original plant tissue.
Mottled:
Patches of different colours or shades of colour interspaced with the dominant colour.
Organic matter:
This arises from recycling of materials from living matter. It includes dead remains of plants and microfauna, both fresh and decomposed.
Plant nutrients:
Describes elements utilized by micro-organisms and gathered by plant roots for biological growth. When a soil is described as "poor" in plant nutrient status it means that the nutrient levels are usually enough to permit growth of many native plants and many exotics, but growth will be better and faster if nutrients are added in suitable amounts. The following materials can be used to help build up soil nutrient levels if used in appropriate circumstances:
- organic material will increase the humus content of the soil. This has an excellent effect on the soil structure in loams and clays while increasing water holding capacity and nutrient storage ability of all soils;
- fertilisers or animal manures will increase the nutrient level of the soil;
- lime or dolomite will neutralise acidity;
- sulphur will neutralise or acidify an alkaline soil;
- gypsum can improve and stabilise soil structure if the soil has a significant quantity of exchangeable sodium.
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Soil profile:
A vertical section of a soil through all its layers and extending into the bedrock. A profile can seen when the soil is exposed in a road or railway cutting.
Structure:
Structure refers to the way soil particles group together to form the soil environment of aggregates and pores. The particles in most soils consolidate into crumbs of various sizes. Some soils, such as beach sand, have particles which do not cling together and therefore are structureless. Some clay soils bind together in one solid mass are also considered structureless. Soils which do not readily break into crumbs are poorly structured. The best soils break-up easily into crumbs with definite shapes and sizes. These soils are said to be “well structured". These crumbs, being irregular in size and shape do not completely fill the soil volume and result in a network of open spaces and passages which are filled by air, water or plant roots. In fact, an average soil may contain forty to sixty percent of these open spaces. The structure of the soil is very important to farmers and gardeners. A well-structured soil will easily take in water through the spaces between the lumps. Excess water will drain away through the spaces and be replaced with air. Most plants need both air and water near their roots to grow well. When surface soils lose their structure they are more easily eroded.
Texture:
Texture is the feel of moist soil when worked between the fingers. It is related to the relative amounts of gravel sand, silt, clay and organic matter. The texture has an important bearing on
- how much water the soil can retain for plant use;
- how easy it is to dig or plough,
- likely fertility level.
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Acknowledgments
This document was developed from material initially supplied by R. van de Graaff of this Department to the Readers Digest publication Illustrated Guide to Gardening 648pp., 1979.
This note replaces note number SC0024.
The advice provided in this publication is intended as a source of information only. Always read the label before using any of the products mentioned. The State of Victoria and its employees do not guarantee that the publication is without flaw of any kind or is wholly appropriate for your particular purposes and therefore disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in this publication.
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