Dominant soil orders in Tasmania: distribution and selected properties.
Abstract: Dermosols (24%) and Organosols (14.8%) are the dominant soil orders in Tasmania, with the mapped occurrence of >985 000 ha of Organosols in Tasmania being the greatest in any Australian State. Tenosols and Rudosols are well represented in all 3 natural resource management (NRM) regions and Kurosols are more prevalent in the NRM North and South Regions. Tasmania has a greater proportion of Ferrosols (8.4%) than the whole of Australia (0.8%) and these soils are some of the most productive in Tasmania with >25 000 ha used for cropping. Hydrosols (3.7%) are probably underestimated. Chromosols (5.3%) and Sodosols (1.6%) are relatively minor soils in Tasmania, occurring predominantly in lower rainfall areas with <800 mm average annual rainfall. Parent material is a strong determinant of soil distribution in Tasmania but many Soil Orders occur on a wide range of parent materials. Brown suborders are predominant in several Soil Orders. A large part of Tasmania (2 658 000 ha) is mapped as being used for conservation, with one-third of this area being mapped as Organosols. The mean surface horizon soil carbon content (4.3%) is relatively high, likely due to Tasmania's relatively high annual rainfall and cool temperatures. Most Soil Orders have moderately acid surface horizons but soils on calcareous parent materials are neutral to strongly alkaline (Tenosols and Calcarosols). The dataset covers the mainland extent of Tasmania, as well as all large islands around Tasmania's coastline including King, Flinders, Hunter, Three Hummock, Robbins, Cape Barren, Clarke, and Maria Islands.

Additional keywords: classification, mapping, landuse, land systems.
Subject: Soils (Distribution)
Soils (Chemical properties)
Authors: Cotching, W.E.
Lynch, S.
Kidd, D.B.
Pub Date: 08/01/2009
Publication: Name: Australian Journal of Soil Research Publisher: CSIRO Publishing Audience: Academic Format: Magazine/Journal Subject: Agricultural industry; Earth sciences Copyright: COPYRIGHT 2009 CSIRO Publishing ISSN: 0004-9573
Issue: Date: August, 2009 Source Volume: 47 Source Issue: 5
Topic: Event Code: 690 Goods & services distribution Advertising Code: 59 Channels of Distribution Computer Subject: Company distribution practices
Geographic: Geographic Scope: Tasmania Geographic Name: Tasmania Geographic Code: 8AUTA Tasmania
Accession Number: 208746645
Full Text: Introduction

Soil mapping and classification are necessary for rational resource evaluation and planning as well as the good management and conservation of the soil resource. Classification is a basic requirement of all science and needs to be revised periodically as knowledge increases (Isbell 2002). The soil resource is one of the components on which Australian agriculture is dependent but it is a finite resource. The use of soil classification is essential for organising our knowledge so that the properties of soils can be remembered, the relationships between soils can be understood, the properties and behaviour of soils can be predicted, and to provide a uniform basis for correlating soil map units between different areas (Avery 1973). Soil correlation has been defined as the process of maintaining consistency in naming, classifying, and interpreting kinds of soils and of the units delineated on maps (Soil Survey Staff 1983).

The first State-wide soil map of Tasmania was published as sheet 2 of the Atlas of Australian Soils (Northcote et al. 1960-68), which was compiled by CSIRO in the 1960s to provide a consistent national description of Australia's soils. The maps were published at a scale of 1:2000 000, with mapped units in the Atlas being soil landscapes, usually comprising several soil types. The explanatory notes included descriptions of soil landscapes and component soils with soil classification based on the Principal Profile Form (Northcote 1979). A generalised soil map of Tasmania (Nicolls and Dimmock 1965) mapped 12 mapping units based on the Great Soil Group classification of Stephens (1962). The map was at a scale of 1:1 800 000 and was complimentary to Northcote et al. (1960-68) with many of the soil boundaries coinciding. The Atlas of Australian Resources (Division of National Mapping 1980) mapped the nation at a scale of 1:5 000 000 based on the properties that affect land management such as depth and water-holding capacity.

Over the period 1940-67, the CSIRO Division of Soils, Adelaide, undertook a series of reconnaissance soil surveys and some more detailed soil surveys of parts of the agricultural land in Tasmania. These surveys form the basis of current knowledge and understanding of the distribution and types of soils within Tasmania. In 1997, the Department of Primary Industries, Water and Environment (DPIWE), with funding from the Natural Heritage Trust, correlated, standardised, and enhanced this existing information to produce a consistent legend and terminology and accessible soil resource information. The reconnaissance series was expanded to include the soil maps at scales of 1 inch to 1 mile (1:63 360) and 1 inch to 2 miles (1 : 126 000). These maps were reformatted and reprinted by the DPIWE at a scale of 1:100 000 (e.g. Nicolls 1959; Spanswick and Kidd 2000) to be consistent with more recent soil mapping scales, the land capability mapping series, and the current Tasmanian Land Tenure map series. The soil terminology used within the reports was updated to be consistent with the Australian Soil and Land Survey Field Handbook (McDonald et al. 1990). Forestry Tasmania has carried out several land and soil studies aimed at defining land suitability classes and erosion problems (Ellis et al. 1975; Davies and Neilsen 1987). Many of these studies provided detailed information on specific areas to assist management planning (Wilkinson and Neilsen 1985). in order to acquire more detailed information on the properties and distribution of Tasmanian forest soils, mapping was carried out in some areas of State forest between 1990 and 1995 (Grant et al. 1995a; Hill et al. 1995; Laffan et al. 1995).

The Australian Natural Resources Atlas (2007) uses the same line work as the Atlas of Australian Soils but classifies the soils according to Isbell (2002). The dominant soil orders for Tasmania in decreasing area are listed as Tenosols, Dermosols, Sodosols, Kurosols, and Organosols. One of the few State-wide coverages of land information is land systems information in which areas of land with a recognisable and repeating pattern of rainfall, topography, geology, soils, and vegetation is mapped. Map units are also described in terms of their land use, with each land system described with up to 6 individual components. Map information was captured and is available on request at 1 : 100 000 scale but was published at 1:200 000 scale. Seven volumes cover the State (Richley 1978, 1984; Pinkard 1980; Pinkard and Richley 1982; Pemberton 1986, 1989; Davies 1988). Original line work for the Land Systems of Tasmania is now used for the State-wide soil coverage of Tasmania in the Australian Soil Resource Information System (ASRIS) (McKenzie et al. 2005). For ASRIS, an additional lookup table was compiled by Leahy (1993), which lists all soil types identified in each map-unit, and their relative proportions within the unit. McKenzie et al. (2000) compiled tables estimating typical ranges for soil properties associated with each Principal Profile Form of the Factual Key. Interpretations for each soil type were based on the range observed in -7000 soil profiles held within the CSIRO National Soil Database, with ancillary data from Northcote et al. (1975). The following properties were estimated for both the A and B horizon: horizon thickness, texture, clay content, bulk density, grade of pedality, and saturated hydraulic conductivity. The Department of Primary Industries and Water (DPIW) is the custodian of, or has access to, much of the available soil information for the State, including that undertaken by CSIRO, Forestry Tasmania, the University of Tasmania, and private groups.

Research on specific Soil Orders in Tasmania has been undertaken and published over recent years. Doyle and Habraken (1993) estimated that sodic soils occupy at least 23% of Tasmania's land area, with strongly sodic soils covering 4% of the land area. Sodic soils occur in lower rainfall areas (<800mm/year) of eastern Tasmania, primarily in the Launceston Tertiary Basin, the Derwent, Coal, Jordan, and Huon River Valleys, and on Flinders Island. They state that in Tasmania, sodic soils have formed predominantly from Triassic and Permian mudstones and sandstones, Tertiary clays, and unconsolidated Quaternary deposits and reported surface horizon pH values of 5.0-5.5.

The impacts of agricultural management on different Soil Orders in Tasmania have been assessed using field and laboratory techniques. This includes Dermosols (Cotching et al. 2002a), Ferrosols (Sparrow et al. 1999), Sodosols (Cotching et al. 2001), Tenosols (Cotching et al. 2002b), and Vertosols (Cotching et al. 2002c). This series of health monitoring studies based on Soil Order gives the first comprehensive review of the effects of agriculture on soil properties in Tasmania and is one of the most comprehensive and useful in Australia (McKenzie et al. 2002).

Recognition that parent material is a strong determinant of soil distribution in Tasmania is a recurring theme. Nicolls and Dimmock (1965) describe how the complexity of the soil map in the Derwent Valley and northern Midlands is in part due to the complex pattern of basic igneous rocks (basalt and dolerite) and more siliceous parent materials (sedimentary rocks and alluvium). The land systems survey delineates map units on the basis of geology and soils. The Forest Soils of Tasmania (Grant et al. 1995b) describes a range of forest soils commonly found in Tasmania with underlying geology used as the primary division in the listing of soils. Within geological types, soils are separated by profile characteristics and the nature of the native vegetation that they support. Laffan et al. (1998) describe distinctly different soils formed on sandstone, granite, and dolerite in relation to dry and wet eucalypt forest types in northern Tasmania. Osok and Doyle (2004) describe the soil stratigraphic and pedological relationships of soils formed on dolerite to help understand their distribution and improve understanding of soil formation history.

Regional management of natural resource initiatives has been agreed to by State and Australian Governments (Natural Heritage Trust 2003). A key requirement for the 3 NRM regions in Tasmania (Fig. 1) has been the development of NRM Strategies which are required to establish and address a range of environmental targets set out under the National Standards and Targets Framework (Natural Resource Management Ministerial Council 2002). In order to address the 'soil matters for target', the 3 NRM regions have undertaken a State-wide soil condition evaluation and monitoring program that is based on Soil Orders and land uses (Moreton et al. 2006). Interim soil condition targets have been set for many of the Soil Orders and land uses in Tasmania (Cotching 2006).

The aims of this research are to classify the dominant Soil Orders in Tasmania according to the Australian Soil Classification (Isbell 2002) using the best available Statewide soil map and to describe the distribution and selected properties of the dominant Soil Orders using information contained in Tasmania's largest soil database.

Methodology

The polygon boundaries on the dominant Soil Orders of Tasmania map (DPIW 2004) were sourced from original line work for the Land Systems of Tasmania, which was published at 1 : 200 000 scale, and have not been modified from this dataset; only soil attributes have been added. This line work was selected because it is the most recent State-wide line work of land information that used a consistent methodology across map sheets. The use of more detailed soil survey line work produced by a variety of organisations was avoided because of problems with matching at sheet boundaries and differences in scale between surveys which might result in differences in polygon definition. The subsequent map of soil information is published at 1:500000 scale. The Soil Order dataset was classified using all digital soil information available at the time of the classification (in 2003). This included soil profile descriptions and data from the Department of Primary Industries Water and Environment (DPIWE) database, detailed and reconnaissance soil maps, the Forestry Tasmania soils database, and land system soil component descriptions. Each land system polygon was viewed in a geographic information system (GIS) with all available soil information in the background. Each component within the polygon was classified using the key in the Australian Soil Classification (ASC) (Isbell 2002) to Suborder level because associated soils in the mapped units can be as important as the dominant soil, or more so, depending on the application. No correlations between the Australian and other soil classifications are presented because differentiating criteria often differ between the classification systems, giving rise to multiple correlatives (Isbell 2002). The percentages for each Soil Order were sourced from component percentages in the land system conceptual diagrams. Other polygons with the same land system number (in another area of the State) received the same soil classification. The final classifications were confirmed or altered where necessary following meetings of a representative expert panel plus review by individual experts with extensive local knowledge of soils of Tasmania. As the soil in each land system component was classified, a confidence level was ascribed to that classification based on the availability of existing soil information. The dataset covers the mainland extent of Tasmania, as well as all large islands around Tasmania's coastline. This includes King, Flinders, Hunter, Three Hummock, Robbins, Cape Barren, Clarke, and Mafia Islands. The boundaries and attributes of the Soil Orders have not been verified in the field for this study. Thumbnail representations of the distribution of where each Soil Order is dominant were produced in Arcmap (ESRI 2007) by selecting the most dominant soil order within each landsystem and exporting this as an image (Figs 2 and 3).

[FIGURE 1 OMITTED]

The mapped polygons represent the dominant Soil Order identified within each land system. The map is available as digital data, A4 or A 1 size printed map, and the land component soil information is held as a data file by the DPIW. Map users should be aware that an observed soil in the field might not match the characteristics of the dominant Soil Order indicated by the map. This may be because the observed soil is not the dominant soil in the land system, or because of a variable percentage of land system components between similarly mapped polygons, or because of errors due to the scale of the map. Map users should also be aware that a Soil Order is the highest level of classification within the ASC and that a wide range of soils and soil properties can occur within a single Soil Order. If more detail is required, the area of interest must be mapped at a scale appropriate for the end use, rather than enlarging the map.

A Statewide coverage of land use in Tasmania, created as part of the Land and Water Resources Audit (Bureau of Rural Sciences 2003), was overlaid on the soil map database and summaries were created of the landuse x Soil Order areas (see Table 4). The BRS land use classification is a hierarchical classification of landuses in the State (attribution scale 1:25 000-1:100 000). The grouping contains up to 100 different landuses. This grouping was simplified to 9 groups.

The DPIW soil database on ORACLE was interrogated using a combination of ORACLE Query Builder, ESRI ArcGIS, and Microsoft Access and Excel to produce the selected properties data for individual Soil Orders. Queries were on Soil Orders and subdivisions within each order on the basis of parent material. Due to incomplete parent material attribution for many profiles in the database, parent material was assigned by spatially overlaying each profile point data over a Statewide 1:250 000 geology coverage, and grouping similar parent material into known categories for individual Soil Orders. The following assumptions and techniques were used during the data interrogation to produce the data (see Table 5):

* The dominant parent material designations in the database were used for each Soil Order, with an overall mean also derived for the entire Soil Order which included all parent materials and profiles with no parent material designation.

* The most common soil texture for the A1 horizon is provided, with 2 or 3 textures listed if there was no clearly dominant texture. Textures follow codes from McDonald et al. (1990).

* All A1 horizon subdivisions were combined to produce the depth of the A1 horizons used for the mean values (see Table 5). For example, for profiles with horizon designations such as All, A12, and A13, the horizon lower depth of the A13 profile was used as the entire A1 depth.

* The depth to the top of the first B2 horizon (including B21 horizons) was used as 'depth to B2', which is the upper zone of maximum soil development.

* Total exchangeable bases (TEB) data, calculated as the sum of Ca, Mg, Na, and K cations, is presented as the database displayed a more complete dataset than for cation exchange capacity (CEC).

* B2 horizons are not present in many of the Soil Orders, e.g. Rudosols and Organosols, and were therefore not applicable. These orders were also generally limited in available soil chemical data and full Australian Soil Classification.

* Chemical data ([pH.sub.water] (1 : 5), TEB, OC) are presented from the surface horizon of soils. The surface horizon was either the A1 horizon or the All horizon when the AI horizon was subdivided. All carbon in soil profiles was not accounted for as the database does not contain OC data for all subsurface horizons and selecting only surface horizons avoids accounting for buried topsoils or eluviation of carbon and re-deposition in subsoil horizons.

* Organic carbon (OC) data for surface horizons were obtained by Walkley and Black analysis (Rayment and Higginson 1992).

[FIGURE 2 OMITTED]

The data (see Table 5) do not necessarily reflect representative mean values for typical Tasmanian soil attributes, but for the profiles recorded in the DPIW soil database. The majority of sites were described using a 'free survey approach' (McDonald et al. 1990), with many sites chosen as the best intact representative site depending on the scale of mapping used at time of survey. This could skew results in several instances, such as an over-estimate of topsoil depth and OC if sites were chosen away from disturbance from landuse. The majority of sites fall within Tasmanian agricultural areas, over-emphasising the State's 'better soils', and excluding many of the areas not chosen as agriculturally productive.

Results and discussion

Detailed soil maps and/or soil profile descriptions with all necessary analytical data (9.9%; Table 1) were concentrated in the more intensively used agricultural areas in the northern Midlands and the north-west coast. Reconnaissance soil maps and profile descriptions with incomplete analytical data (17.5%) were available in the agricultural areas of the central north and south-east as well as on Flinders and King Islands. Reconnaissance soil maps and/or knowledge of similar soils in similar environments (29%) were available in native and plantation forestry areas and agricultural areas with low intensity use in most areas of Tasmania. Land system component soil descriptions (43.6%) were relied on for the west coast, south, central highlands, and much of a narrow strip of the east coast.

[FIGURE 3 OMITTED]

Calcarosols are characterised by having pedogenic carbonate, usually throughout the profile or at least directly below the A1 horizon. They are shallow soils with a gradual increase in clay content with depth (Isbell et al. 1997). They have low water-holding capacity, often have nutrient disorders, and can be subject to wind erosion. Calcarosols are the least abundant (0.3%) Soil Order in Tasmania (Table 2) but our scale of mapping identifies their presence rather than them being 'virtually absent' as described by Isbell et al. (1997). Calcarosols occur predominantly on Flinders Island in the NRM North Region with a small area on the coast in the south (data not shown). The calcic suborder dominates (Table 3) and grazing natural vegetation and modified pastures are the dominant land uses (Table 4). Soils are sandy textured with relatively low OC content and they are strongly alkaline (Table 5).

Chromosols have a strong texture contrast between A and B horizons, which are not strongly acid or sodic. They can have a perched seasonal water table (Isbell et al. 1997). Chromosols are a relatively minor soil in Tasmania (5.3%; Table 2) occurring in eastern and south-eastern areas (Fig. 2a), predominantly in the NRM South Region. These areas are in the lower rainfall zone receiving <800mm average annual rainfall (Bureau of Meteorology 2008), which gives rise to less leaching than higher rainfall and so higher pH values, which are required for soils to classify as Chromosols. The brown suborder is completely dominant in Tasmania (Table 3) in contrast to the frequency of records (31%) in the Australian Classification database (Isbell et al 1997). Grazing is the predominant land use (241 000 ha), but considerable areas of Chromosols are mapped as being used for native and plantation forestry, conservation, and cropping (Table 4). Surface textures are dominated by fine sandy loams and a large proportion of the described Chromosols occur on Tertiary sediments. Surface horizons are moderately to slightly acid and organic carbon contents (Table 5) are greater than those published for similar Australian soils (Baldock and Skjemstad 1999).

Dermosols have a moderately to strongly structured B horizon (Isbell et al. 1997), and in Tasmania clay content generally increases with depth. They have few persistent limitations to plant growth. Dermosols are the dominant Soil Order in Tasmania (24%), with a wide geographic occurrence except in the south-west of the State (Fig. 2b). This dominance is in contrast to the whole of Australia where Dermosols cover only 1.6% of the land surface (The Australian Natural Resources Atlas). The brown suborder is dominant and red is subdominant, which is the reverse of the frequency of records in the Australian Classification database (Isbell et al. 1997). Native vegetation covers most of these soils (1 300 000 ha) with large areas used for conservation or production native forestry and they are the most widely used Soil Order for grazing natural vegetation, grazing dryland pasture, and horticulture (Table 4), which is likely due to these soils having few persistent limitations to plant growth. Dermosols occur on a wide range of parent materials including sedimentary and volcanic rocks and sediments, which indicates that parent material is not the dominant soil forming factor for this Soil Order but rather the Tasmanian climate, which is cool temperate with relatively high rainfall. Surface textures are predominantly clay loams and A1 horizons have mean thicknesses of 0.16-0.20m. Surface horizons are moderately to slightly acid and mean organic carbon contents range considerably on different parent materials from 3.7% on Tertiary sediments to 6.5% on dolerite (Table 5). A wide range of soil OC contents have also been found on Dermosols in Tasmania's Northern Midlands (4.2-7.0% in the upper 75 mm) by Cotching et al. (2002a). TEB range from 10 cmol(+)/kg on sedimentary parent rocks to 24 cmol(+)/kg on dolerite and the mean for the order is the third highest for Tasmanian Soil Orders (Table 5) and is associated with high clay contents.

Ferrosols are characterised by high free iron oxide content and are typically strongly structured (Isbell et al. 1997). The iron oxides, together with smaller amounts of free aluminium oxides (Moody 1994) and relatively high organic matter contents (Oades 1995), give Ferrosols their strongly developed structure. Ferrosols are a significant Soil Order (8.4%) occurring throughout Tasmania (Fig. 2c), with just over half of the area occurring in the Cradle Coast NRM Region (Table 2). Tasmania has a greater proportion of Ferrosols than the whole of Australia, where they cover 0.8% of the land surface (The Australian Natural Resources Atlas). Red (dominant) and brown (sub-dominant) suborders are described (Table 3), with red soils occurring at lower altitudes (wanner) and under less rainfall than brown soils. Pasture grazing and forestry are the predominant land uses but these soils are some of the most productive in Tasmania with >26000ha used for cropping (Table 4). The more intensive land uses practiced on Ferrosols are characterised by a considerable degree of soil disturbance and they are subject to stresses resulting from farm operations and being left without a protective vegetative cover for prolonged periods. The resulting soil loss by accelerated erosion, structural deterioration, and declining organic matter levels associated with intensive management represent the major challenges for long-term management of Ferrosols (Cotching 1995). Most of the described profiles occur on basalt with a mean topsoil depth of 0.21 m and surface horizons are moderately acid (Table 5) but subsoils can be strongly acid (Grant et al. 1995a). Ferrosols contain considerable amounts of topsoil OC (6.5%) with soils on dolerite having a mean of 9.0% carbon in surface horizons, which is likely to be due to their occurrence at higher altitudes and annual rainfall in excess of 1400 mm. Organic carbon contents are also dependent on management with Ferrosols under perennial pasture in Tasmania having an average of 5.9% carbon in surface horizons but as little as 2.3% carbon after 25 years of continuous cropping (Sparrow et al. 1999). The mean TEB for the order is the second highest for Tasmanian Soil Orders (Table 5) and is associated with these soils having high clay and OC contents.

Hydrosols are seasonally or permanently wet with the greater part of the profile being saturated for 2-3 months or more in most years (Isbell et al. 1997). Wetness can be caused by being in a low part of the landscape such as on a flat swampland, or by low soil permeability. Hydrosols are mapped as occupying 3.7% of Tasmania and they are relatively evenly spread across the 3 NRM Regions (Table 2 and Fig. 2d). However, many Hydrosol occurrences are small in area and hence are not mappable, e.g. wet drainage depressions, low lying coastal plains, and seepage areas on lower slopes (McKenzie et al. 2004). Consequently, the total area is probably an under estimate and previously they have been under-reported in Tasmania (The Australian Natural Resources Atlas). Mottled Hydrosols (redoxic) are dominant but whole-coloured soils (oxyaquic) are also strongly represented. Grazing dryland pasture is the predominant landuse with significant areas used for native and plantation forestry or under conservation (Table 4). Artificial drainage has been installed in many areas of these soils to overcome the limitation of waterlogging and this has made these areas more agriculturally productive, but in some instances can lead to significant loss of applied nutrients to waterways (Holz 2007). Surface textures are predominantly clay loams to medium clays and A 1 horizons have mean thicknesses of 0.21 m but variability is high. Surface horizons are moderately to strongly acid but variability is high, particularly in profiles developed on Quaternary alluvium (Table 5). Mean OC contents in surface horizons range from 2.4% on Tertiary sediments to 5.0% on Quaternary alluvium (Table 5). Mean TEB in surface horizons ranges from 6.6 cmol(+)/kg on Tertiary sediments to 17.7 cmol(+)/kg on Quaternary alluvium (Table 5).

Kandosols lack a clear or abrupt textural B horizon, are not calcareous throughout, and the clay content of the weakly structured or massive B2 horizon exceeds 15% (Isbell et al. 1997). Kandosols are mapped as occupying 3.9% of Tasmania and they are relatively evenly spread across the 3 NRM Regions (Table 2 and Fig. 2e). Kandosols are not as widespread in Tasmania as in the rest of Australia where they occupy 17% of the continent (McKenzie et al. 2004). Grey and brown suborders are dominant. Conservation and production native forestry are the predominant landuses (104 000 and 76 000 ha, respectively) with 67 000 ha used for grazing (Table 4). Surface textures are predominantly clay loams and A1 horizons have mean thicknesses of 0.20 m. Surface horizons are moderately acid and mean OC contents in surface horizons range from a low 1.0% on Quaternary alluvium to 4.2% on Tertiary sediments (Table 5). Mean TEB in surface horizons is 10.3 cmol(+)/kg.

Kurosols have a clear or abrupt textural B horizon, the upper part of which is strongly acid (Isbell et al. 1997). Many of these soils have a strongly bleached A2 horizon and the B2 horizon is commonly mottled. Kurosols are a significant Soil Order (9.8%) occurring mainly in the east of Tasmania (Fig. 2f) with over one-third of them occurring in the NRM South and half in the NRM North Regions (Table 2). Brown Kurosols are the dominant suborder (Table 3). Grazing is the predominant landuse, both on modified pastures and natural vegetation, but there are significant areas used for conservation and forestry. Kurosols are the second most extensively used soil order for cropping in Tasmania (15000 ha) behind Ferrosols but several studies have found soil degradation associated with cropping on texture-contrast soils in Australia (Packer et al. 1992; Macks et al. 1996) and in Tasmania (Cotching et al. 2001). Surface textures are predominantly sandy loams and clay loams with A1 horizons having mean thicknesses of 0.19-0.20m. Surface horizons are strongly acid and mean OC contents in surface horizons are 4.6% for the profiles described. Mean TEB in surface horizons is 9.2 cmol(+)/kg but this ranges considerably (Table 5).

Organosols are dominated by organic material and have long been known as peats (Isbell et al. 1997). They characteristically occur in wet landscapes under high rainfall and so are subject to waterlogging. Many of the Organosols in Tasmania are shallow, ranging from 0.2 to 0.4 m in thickness, and overlie a range of substrates from massive quartzite to gravels (Pemberton 1989). Organosols cover large parts of western Tasmania (Fig. 3a), occurring in alpine areas and with mean annual rainfall in excess of 2400 mm (Bureau of Meteorology 2008). They are the second most dominant Soil Order in Tasmania (14.8%), in contrast to the whole of Australia where they cover only 0.1% of the land surface (The Australian Natural Resources Atlas). Tasmania has the largest area of Organosols of any Australian state and this study has identified over 985 000 ha, which is more than the Natural Resource Atlas identified for the whole of Australia, and is 28 times the area occurring in Victoria, the second greatest occurrence by State. They occur mostly in the NRM South and Cradle Coast NRM Regions (Table 2). The dominant land use is conservation (88%; Table 4), much of which is protected in the World Heritage Area and reserves. Production native forestry and grazing are minor uses. The factors that promote peat formation in the west and south-west of Tasmania include high rainfall, low evaporation, and high relative humidity. These conditions provide the anaerobic, acidic environment in which peat develops through the accumulation of organic matter. The fibric and heroic suborders are co-dominant (Table 3). Organosols in the south-west and central highlands of Tasmania are subject to degradation by sheet erosion and fire (Pemberton 1989). Erosion is usually initiated in areas of poor land management with areas corresponding to regions that have been burnt. Fires arise from lightning strikes, hazard reduction bums, or arson and they remove the vegetation allowing the high rainfall and strong winds to intensify the erosion. The degradation of Organosols by fire and erosion is serious because the rate of formation is so slow. Organosols are under-represented on the DPIW database with very few profiles described with analytical data (20 profiles). Individual soil surveys have described and analysed Organosols on quartzite or dolomite (Grant et al. 1995b) which are extremely acid, or peat bogs which range from extremely acid to neutral (Hubble and Bastick 1995). Analysed profiles have 25-56% carbon in surface horizons and 26-94 cmol(+)/kg of TEB. The occurrence of sulfidic material within 0.5 m of the soil surface has been recorded in the Mowbray swamp near Smithton with pH as low as 1.9 following oxidation during air drying of samples (Hubble and Bastick 1995). A reconnaissance survey has found that coastal, estuarine, and back swamp sediments deposited since the Holocene period are potential sites for the development of acid sulfate soils which typically occur along the northern Tasmanian coastline and on King Island and Flinders Island (Gurung 2001).

Podosols have B horizons dominated by the accumulation of compounds of organic matter and aluminum with or without iron (Isbell et al. 1997). They are usually sand-textured and have a bleached A2 horizon, often of considerable thickness, with a colour B horizon or hard pan beneath. Podosols cover 4% of Tasmania and they occur predominantly in the Cradle Coast and North NRM Regions (Table 2 and Fig. 3b). Many Podosols occur in the coastal zone on Quaternary deposits of quartz sand, both dunes and low lying sand plains, but Tasmania has many profiles described as being formed on acid rocks such as sandstone, quartzite, and conglomerate (Table 2) (Grant et al. 1995b). Podosols on low-lying sand plains are seasonally wet with the semi-aquic and aquic suborders prevalent (Table 3). The predominant landuse on Podosols is grazing, particularly modified pastures (dryland and irrigated), for which drainage is required, but there are also considerable areas (64000 ha) under conservation (Table 4). A horizons are relatively thick with Podosols having the greatest mean depth (0.48m) to the B2 horizon of any order. Surface horizons are moderately to strongly acid and have relatively high OC contents for sand-textured materials, probably because of long periods of saturation which result in accumulation rather than oxidation of organic matter (Table 5).

Rudosols have not been greatly affected by pedological processes and so have little or no pedologic organisation, apart from minimal development of an A1 horizon (Isbell et al. 1997). Rudosols are a significant Soil Order (10.2%) occurring throughout Tasmania (Fig. 3c) with nearly half of them occurring in the NRM South Region (Table 2). Many of the mapped Rudosols are in coastal areas where these young soils are formed on sand dunes. Upland areas such as the Central Plateau and Ben Lomond, with rock to the surface and only minor soil development between boulders and in crevices (Pemberton 1989), result in most of the Rudosols being gravelly or stoney with Clastic and Leptic suborders dominating (Table 3). Much of the land use for Rudosols is conservation or production native forestry (405 000 ha combined; Table 4). Many of these areas are relatively remote and the data collected are limited, as reflected in the few profile descriptions (28) and no analytical data on the DPIW database (Table 5). However, considerable areas of Rudosols are also mapped as used for pasture grazing (113 000 ha), which is similar to Podosols and suggests that either Rudosols are over represented in our mapping or they are under represented on the DPIW database.

Sodosols have a clear or abrupt textural B horizon, the upper 0.2 m of which has an equivalent sodium percentage (ESP) of 6 or greater and is not strongly acid (Isbell et al. 1997). A seasonal perched water table, with a bleached A2 horizon, is common due to clay-textured B horizons with low permeability. Sodosols are a minor Soil Order (1.6%) occurring mainly in the south-east of Tasmania (Fig. 3d) with almost equal occurrence in the NRM North and NRM South Regions (Table 2). These areas are in the lower rainfall zone receiving <800 mm average annual rainfall (Bureau of Meteorology 2008) which gives rise to long-term accession of salt from rainfall. Tasmania is known as having a wet climate and in general this applies, but there are areas in the south-east that have <500 mm mean annual rainfall, which results in net soil water deficits and the build-up of salt in the soil. The area of Tasmania mapped as Sodosols in this exercise (1.6%) is much less than the 23% of sodic soils by Doyle and Habraken (1993) but is closer to their 4% of strongly sodic soils. We attribute the difference between the 2 studies to their analysis being based largely on re-interpretations of the Northcote (1962) map at 1:2 000 000 scale. Our methodology utilised the land system survey polygons at 1 : 100 000 scale plus further subdivision into land components and profile data rather than allocation of complete polygons to one particular soil order. Many areas mapped as Chromosols and Kurosols in our study (Fig. 2a, f) correspond with the 28% of Tasmania mapped by Doyle and Habraken (1993) as soils with a bleached A2 horizon and duplex profile form. These 2 Soil Orders are duplex but not Sodosols, although many profiles may classify in sodic subgroups thus increasing the area included as sodic (23%) by Doyle and Habraken (1993). The ESP data and the general absence of sodic A horizons suggest that many sodic soils are only weakly sodic (Doyle and Habraken 1993). Brown Sodosols are the dominant suborder (Table 3). Grazing is the predominant landuse, both on modified pastures and natural vegetation, and significant areas are used for cropping (1600 ha, Table 4) but soil degradation associated with cropping on Sodosols has been reported (Cotching et al. 2001). Traditionally, agricultural use of Sodosols in Tasmania has been for pasture production but they are being used increasingly for cropping. Associated with increasing cropping intensity has been the use of irrigation, which is now normal practice for many of the crops grown. The major challenges for farmers who crop Sodosols in Tasmania's Midlands are to maintain organic matter levels, minimise the amount of tillage, avoid mixing of the less stable A2 horizon with the AI horizon, and to promote surface drainage (Chilvers 1996). Cultivation for crop-sowing and harvesting, particularly potato harvesting, is often carried out when soil moisture content is greater than ideal, which results in soil structure problems such as compaction and hard setting. Cropping on these inherently fragile, texture-contrast soils, particularly including potatoes in the rotation, is associated with poorer physical attributes of aggregate size, aggregate stability, infiltration rate, and drainage at field capacity as well as lower soil OC concentrations (Cotching et al. 2001). Sodosols occur on a wide variety of parent materials with Tertiary sediments being the most common for the profiles in the DPIW database. Surface horizons are generally moderately acid with OC contents being the lowest (mean 2.9%) for any of the duplex Soil Orders and the mean TEB of surface horizons (7.1 cmol(+)/kg) being the lowest of all orders (Table 5).

Tenosols have only weak soil development with weakly expressed B horizons but strongly developed A horizons are included (Isbell et al. 1997). Tenosols cover large parts of western and north-west Tasmania (Fig. 3e), often occurring in association with Organosols and Rudosols at higher elevations. They are the third most dominant Soil Order in Tasmania (12.1%), and occur mostly in the Cradle Coast and South NRM Regions (Table 2). Suborders that are shallow and overlie hard rock (leptic) or are rich in organic matter (chemic, chernic-leptic) are dominant (Table 3) and the dominant land use is conservation (481 000 ha), with production native forestry and grazing being lesser uses (Table 4). Profile descriptions on the DPIW database are weighted towards those on dunes with loamy sand textures and near neutral pH dominant in surface horizons. Mean OC contents (3.8%) and associated TEB (11.3cmol(+)/kg) are relatively high for such sandy textures (Table 5).

Vertosols are shrink--swell soils with 35% or more clay by field texture throughout the profile (Isbell et al. 1997). They are known to crack to considerable depth in summer and have self-mulching A horizons. Vertosols are a minor soil order in Tasmania (1.8%) occurring in the South and North NRM Regions (Fig. 3f and Table 2). They occur much less frequently than on mainland Australia where they cover 11.5% of the total land surface (The Australian Natural Resources Atlas). The black suborder predominates (Table 3). The dominant landuse is grazing modified pasture (57000 ha) and grazing natural vegetation (34000 ha), with considerable areas used for cropping (8500ha), which has been found to degrade soil physical properties and result in reduced soil carbon contents (Cotching et al. 2002c). Vertosols occur on a wide range of parent materials with surface horizons being moderately to slightly acid and having the highest mean TEB (34.4 cmol(+)/kg) of any Soil Order in Tasmania (Table 5).

Summary

Tasmania contains a diverse range of soils due to variations in climate, landscape, and geology, with all of the 13 Soil Orders represented. Rainfall ranges from > 2400 mm per annum on the west coast to <500 mm per annum in the south-cast, topography from alluvial flats to mountain ranges, and geology from soft unconsolidated recent sediments to very old (pre-Cambrian) and hard metamorphic and volcanic rocks. The soils that have developed in such a diverse landscape include Organosols developed on peat, Ferrosols formed on basalt, Tenosols formed on wind blown sands, and easily degraded Sodosols and Kurosols on sediments and sedimentary rocks. The soil types of the State are intimately linked with the State's ecosystem diversity, the visible signs of which are expressed in the complex pattern of both native and exotic vegetation types and the influence of soils on landuse. The uniqueness of this ecosystem diversity is recognised with 40% of the State being protected in the World Heritage Area, national parks, and reserves. Clearing for agriculture has occurred mostly on the more versatile soils and gentler slopes and improved access to water has enabled the diversification of land use with cropping in some areas. The soils with the least versatility of use through poor fertility, poor drainage, or climatic restrictions are well reserved, e.g. Organosols, Rudosols, and Tenosols, due to little competition from other production-based land uses.

Dermosols are the dominant Soil Order in Tasmania (24%) with a wide geographic occurrence except in the south-west of the State. Organosols are the second most dominant Soil Order (14.8%) covering large parts of western Tasmania in alpine areas and with mean annual rainfall in excess of 2400 mm. The mapped occurrence of >985 000 ha of Organosols in Tasmania makes the State the undisputed home of this Soil Order. This dominance is in contrast to the whole of Australia where Dermosols cover only 1.6% and Organosols only 0.1% of the land surface. Tenosols and Rudosols are well represented in all 3 NRM Regions and Kurosols are more prevalent in the NRM North and NRM South Regions. Tasmania has a greater proportion of Ferrosols (8.4%) than the whole of Australia (0.8%) and these soils are some of the most productive in Tasmania with >25 000 ha used for cropping. The Cradle Coast NRM Region contains over half of Tasmania's Ferrosols and the combination of good soils and a temperate moist climate makes the Cradle Coast NRM region the most agriculturally productive in Tasmania. The highly productive Ferrosols, developed on basaltic parent material, are a critical asset for sustainable agriculture and forestry, both in the Cradle Coast Region, and in the State. The NRM South and Cradle Coast NRM Regions are dominated by Dermosols, Organosols, Tenosols, and Rudosols and have a more even spread of Soil Orders than the NRM North Region. NRM South has the greatest proportion of Chromosols and NRM North is dominated by Dermosols and Kurosols. Hydrosols (3.7%) are relatively evenly spread across the 3 NRM Regions but this is probably an underestimate as many Hydrosol occurrences are small in area and hence are not mappable. Chromosols (5.3%) and Sodosols (1.6%) are relatively minor soils in Tasmania and they occur predominantly in lower rainfall areas with <800 mm average annual rainfall. Brown suborders are predominant in the Chromosols, Dermosols, Kurosols and Sodosols of Tasmania. The mean surface horizon soil carbon content (4.3%) for all profiles on the DPIW database is relatively high which is likely to be due to Tasmania's relatively high annual rainfall (Verheijen et al. 2005). Most Soil Orders have moderately acid surface horizons but soils on calcareous parent materials are neutral to strongly alkaline (Tenosols and Calcarosols).

All Soil Orders are mapped as having a proportion under conservation use but the majority of soils described, and for which analytical data are available, fall within agricultural areas, over-emphasising the State's 'better soils', and excluding many of the areas not chosen as agriculturally productive. Organosols and Rudosols are under represented on the DPIW database with very few profiles described and little analytical data available. The economic interest in land has been the driver for the collection of soils information in the past but it is important to study the soils in conservation areas if they and their dependent ecosystems are to be properly understood and conserved. Collection of data on the under-represented soils is an area for future work.

Acknowledgements

We thank our colleagues who rigorously scrutinised and commented on the soil map in areas of Tasmania where they had knowledge and experience of local soils. We acknowledge the many pedologists and landscape scientists who described and mapped parts of Tasmania to build the collective knowledge on which this work is based. We thank Greg Pinkard who reviewed an early draft of this manuscript.

Manuscript received 24 October 2008, accepted 24 April 2009

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W. E. Cotching (A,D), S. Lynch (B), and D. B. Kidd (C)

(A) Tasmanian Institute of Agricultural Research, University of Tasmania, PO Box 3523, Burnie, Tas. 7320, Australia.

(B) Department of Infrastructure, Energy and Resources, GPO Box 936, Hobart, Tas. 7001, Australia.

(C) Department of Primary Industries and Water, PO Box 46, Kings Meadows, Tas. 7249, Australia.

(D) Corresponding author. Email: Bill.Cotching@utas.edu.au
Table 1. Confidence level of soil component classification within
mapped polygons

Confidence   Description of information used       Proportion of
level                                              Tasmania (%)

1            Detailed soil maps and/or profile          9.9
             descriptions with all necessary
             analytical data

2            Reconnaissance soil maps and              17.5
             profile descriptions but analytical
             data incomplete

3            Reconnaissance soil maps and/or           29.0
             knowledge of similar soils in
             similar environments

4            Land system component descriptions        43.6
             of soils only

Table 2. Occurrence of Soil Orders by Tasmanian NRM Region
derived from classification of land system components

               Area (ha) in NRM Region              Total area

                                    Cradle
             NRM        NRM         Coast         (ha)        (%)
Soil Order   South      North       NRM

Calcarosol        800      25 419                18 126       0.3
Chromosol     250 985      78 461     11 202     348 741      5.3
Dermosol      480 623     721 123    410 814   1 612 560     24.3
Ferrosol      116 061     135 661    302 024     553 746      8.4
Hydrosol       76 155      59 440    109 739     245 334      3.7
Kandosol       78 879      80 771    100 145     259 795      3.9
Kurosol       253 086     352 953     62 831     668 870      9.6
Organosol     450 275      33 350    502 239     985 865     14.8
Podosol        14 572     123 683    130 206     268 461      4.0
Rudosol       303 381     189 794    180 848     674 023     10.2
Sodosol        46 422      61 868                108 290      1.6
Tenosol       288 284      92 813    420 716     801 813     12.1
Vertosol       68 974      48 882                118 164      1.8

Total                                          6 628 821     100

Table 3. Soil suborders mapped in Tasmania
derived from classification of land system
components

Soil Order     Suborder      Proportion
                               of soil
                                order

Calcarosol   Calcic             0.53
             Hypocalcic         0.08
             Lithocalcic        0.21
             Shelly             0.13
             Supracalcic        0.05
Chromosol    Brown              0.95
             Red                0.03
             Yellow             0.02
Dermosol     Black              0.03
             Brown              0.66
             Grey               0.05
             Red                0.19
             Yellow             0.07
Ferrosol     Brown              0.45
             Red                0.55
Hydrosol     Extratidal        <0.01
             Intertidal        <0.01
             Oxyaquic           0.42
             Redoxic            0.53
             Salic              0.05
             Sapric            <0.01
             Supratidal        <0.01
Kandosol     Black              0.12
             Brown              0.33
             Grey               0.41
             Red                0.03
             Yellow             0.11
Kurosol      Black             <0.01
             Brown              0.66
             Grey               0.15
             Red                0.05
             Yellow             0.14
Organosol    Fibric             0.42
             Hemic              0.42
             Sapric             0.16
Podosol      Aeric              0.24
             Aquic              0.30
             Oxyaquic           0.01
             Semiaquic          0.45
Rudosol      Arenic             0.05
             Clastic            0.73
             Leptic             0.14
             Shelly             0.08
Sodosol      Black              0.03
             Brown              0.80
             Grey               0.09
             Yellow             0.08
Tenosol      Black-orthic      <0.01
             Brown-orthic       0.21
             Chemic             0.19
             Chernic-lept       0.14
             Clastic           <0.01
             Grey-orthic        0.13
             Leptic             0.28
             Orthic             0.02
             Red-orthic        <0.01
             Yellow-orthic      0.03
Vertosol     Black              0.93
             Brown              0.02
             Grey               0.05

Table 4. Areas (ha) of Soil Orders within major landuse
categories in Tasmania, derived from Bureau of Rural
Sciences landuse classification (2003)

Soil Order   Conservation    Production    Plantation
                                 native     forestry
                               forestry

Calcarosol          359             0            42
Chromosol         32553         55799         8262
Dermosol         516941        518197        54220
Ferrosol          83406        148890        93621
Hydrosol          55053         42793        11141
Kandosol         104012         75764         9050
Kurosol          159044        107311        19242
Organosol        872180         70944          988
Podosol           63680         15206         4818
Rudosol          277167        127538        10704
Sodosol            4957          3640          639
Tenosol          480918        110461         2514
Vertosol           7528          7693          555
Total          2 657798      1 284235       215798

                         Grazing modified pasture
Soil Order       Grazing
                 natural        Dryland    Irrigated
              vegetation

Calcarosol         6424         10907           181
Chromosol        131365        110017           390
Dermosol         264497        219801          8830
Ferrosol          55866        125935         12240
Hydrosol          39098         79635          6969
Kandosol          25032         39774          2031
Kurosol          129122        183610          4321
Organosol         28999         10536            25
Podosol           65089        104497          6632
Rudosol          128956        112453           592
Sodosol           20070         73136            11
Tenosol          108181         88571          1358
Vertosol          33972         57337           136
Total           1036672       1216210         43715

Soil Order      Cropping      Perennial       Urban/
               Irrigated    horticulture   disturbed

Calcarosol          146            19           47
Chromosol          2527           487         7340
Dermosol           9131          1700        19243
Ferrosol          25711           349         7728
Hydrosol           3168          1099         6377
Kandosol           1273           256         2603
Kurosol           14943          1571        14741
Organosol            39             0         2152
Podosol            1542          1167         5830
Rudosol            2578           897        13139
Sodosol            4115           327         1395
Tenosol            3401           712         5696
Vertosol           8504           388         2050
Total             77080          8972        88342

Table 5. Selected properties of soil orders in
Tasmanian DPIW database

Values are mean (standard deviation), with number
of profiles used for statistic in italic

Soil Order   Parent material           No. of     Dominant
                                      described   surface
                                      profiles    texture
                                                    (A)

Calcarosol   Total/mean for order         4        S/FSL

Chromosol    Dolerite                    47         FSL
             Mudstones/sandstones        91         FSL
             Tertiary Sediments          175        FSL
             Mean for order              460        FSL

Dermosol     Dolerite                    51          CL
             Mudstones/sandstones        180       FSL/L
             Granite                     60         SCL
             Tertiary sediments          281         CL
             Mean for order              870         CL

Ferrosol     Basalt                      770         CL
             Dolerite                    18          CL
             Mean for order              928         CL

Hydrosol     Tertiary sediments          178       LC/MC
             Quaternary alluvium         58        CL/SCL
             Mean for order              331       CL/LC

Kandosol     Tertiary sediments          85          CL
             Sandstone/mudstone          73          CL
             Quaternary alluvium         32         FSL
             Mean for order              257         CL

Kurosol      Mudstones/sandstones        81        SL/FSL
             Tertiary sediments          52          CL
             Mean for order              211       SL/CL

Organosol    Hard rock                    4          L
             Basin peat                   4         L/SL
             Mean for order              20         L/SL

Podosol      Sandstone/mudstone          60        CL/LS
             Coastal sands               73          LS
             Quaternary alluvium         37        FSL/LS
             Mean for order              224         LS

Rudosol      Sandstone/mudstone           6       L/SL/LS
             Quaternary deposits         12        LS/LC
             Mean for order              28          SL

Sodosol      Mudstones/sandstones        51          SL
             Dolerite                    18       FSCL/LC
             Quaternary alluvium         80         FSL
             Tertiary sediments          128        FSL
             Mean for order              300        FSL

Tenosol      Coastal dunes               12          LS
             Inland dunes                56          LS
             Hard rocks, dolerite         8        CL/SCL
             Hard rocks, sandstone/      20          LS
             mudstone
             Mean for order              162         LS

Vertosol     Basalt                      14          CL
             Dolerite                     9       FSMC/MHC
             Tertiary sediments          69          MC
             Quaternary alluvium         60          MC
             Mean for order              186         MC

Total                                   3982         CL

(A) Surface horizon.

Soil Order   Parent material           Depth of A1      Depth to B2
                                           (cm)             (cm)

Calcarosol   Total/mean for order     24 (15.7) 4#     45 (27.0) 3#

Chromosol    Dolerite                 15 (9.7) 47#     28 (13.7) 39#
             Mudstones/sandstones     19 (11.8) 91#    32 (12.4) 73#
             Tertiary Sediments       16 (7.7) 175#    38 (12.4) 157#
             Mean for order           18 (11.0) 460#   35 (16.9) 395#

Dermosol     Dolerite                 20 (10.4) 51#    30 (16.4) 27#
             Mudstones/sandstones     17 (14.9) 180#   32 (18.9) 133#
             Granite                  20 (21.8) 60#    46 (23.3) 31#
             Tertiary sediments       16 (8.9) 281#    34 (13.0) 268#
             Mean for order           18 (13.9) 870#   34 (16.1) 707#

Ferrosol     Basalt                   21 (12.9) 770#   33 (19.6) 712#
             Dolerite                 24 (25.0) 18#    28 (10.8) 12#
             Mean for order           21 (13.4) 928#   33 (14.9) 707#

Hydrosol     Tertiary sediments       16 (8.0) 178#    34 (12.3) 160#
             Quaternary alluvium      29 (20.9) 58#    31 09.0) 45#
             Mean for order           21 (14.7) 331#   33 (15.0) 285#

Kandosol     Tertiary sediments       19 (14.7) 85#    39 (15.3) 74#
             Sandstone/mudstone       21 (17.3) 73#    31 (17.3) 51#
             Quaternary alluvium      19 (11.7) 32#    30 (12.9) 25#
             Mean for order           20 (14.6) 257#   35 (17.8) 197#

Kurosol      Mudstones/sandstones     19 (14.5) 81#    35 (19.2) 54#
             Tertiary sediments       19 (14.6) 52#    40 (17.5) 45#
             Mean for order           20 (14.6) 211#   37 (19.7) 158#

Organosol    Hard rock                20 (23.0) 4#     Not Applicable
             Basin peat               41 (40.0) 4#     Not Applicable
             Mean for order           30 (30.7) 20#    Not Applicable

Podosol      Sandstone/mudstone       25 (15.1) 60#    45 (23.4) 38#
             Coastal sands            30 (17.4) 73#    47 (36.7) 57#
             Quaternary alluvium      27 (16.4) 37#    51 (26.6) 25#
             Mean for order           28 (16.8) 224#   48 (29.8) 157#

Rudosol      Sandstone/mudstone       22 (12.9) 6#     24 (15.6) 2#
             Quaternary deposits      33 (23.3) 12#    44 (7.8) 5#
             Mean for order           29 (18.9) 28#    37 (14.0) 13#

Sodosol      Mudstones/sandstones     20 (12.8) 51#    35 (21.5) 35#
             Dolerite                 23 (11.7) 18#    29 (16.8) 7#
             Quaternary alluvium      17 (8.6) 80#     36 (12.5) 69#
             Tertiary sediments       18 (11.3) 128#   35 (14.7) 110#
             Mean for order           18 (10.8) 300#   35 (15.1) 238#

Tenosol      Coastal dunes            26 (13.0) 12#    33 (17.0) 4#
             Inland dunes             22 (12.0) 56#    28 (12.8) 32#
             Hard rocks, dolerite     34 (20.5) 8#     48 (25.7) 5#
             Hard rocks, sandstone/   27 (17.5) 20#    36 (13.4) 11#
             mudstone
             Mean for order           23 (14.7) 162#   36 (19.1) 82#

Vertosol     Basalt                   37 (23.1) 14#    47 (26.8) l#
             Dolerite                 35 (17.7) 9#     37 (28.9) 3#
             Tertiary sediments       25 (20.6) 69#    32 (16.2) 62#
             Quaternary alluvium      32 (23.4) 60#    36 (20.3) 41#
             Mean for order           28 (21.0) 186#   33 (18.6) 143#

Total                                 20 (14.5) 3982   35 (17.4) 3229

Soil Order   Parent material               [Ph.sub.water] (A)

Calcarosol   Total/mean for order            8.98 (0.25) 2#

Chromosol    Dolerite                        5.96 (0.55) 8#
             Mudstones/sandstones            5.64 (0.46) 12#
             Tertiary Sediments              5.61 (0.33) 14#
             Mean for order                  5.74 (0.42) 48#

Dermosol     Dolerite                        5.98 (0.60) 8#
             Mudstones/sandstones            5.38 (0.52) 14#
             Granite                         5.71 (0.70) 4#
             Tertiary sediments              6.30 (0.79) 7#
             Mean for order                  5.77 (0.65) 43#

Ferrosol     Basalt                          5.73 (0.33) 17#
             Dolerite                        6.15 (0.25) 4#
             Mean for order                  5.81 (0.35) 29#

Hydrosol     Tertiary sediments              5.19 (0.70) 3#
             Quaternary alluvium             5.78 (0.94) 6#
             Mean for order                  5.65 (0.67) 17#

Kandosol     Tertiary sediments              Not Available
             Sandstone/mudstone              5.70 (0.57) 10#
             Quaternary alluvium             6.30 (0.45) 3#
             Mean for order                  5.80 (0.61) 23#

Kurosol      Mudstones/sandstones            5.70 (0.82) 3#
             Tertiary sediments              5.25 (0.21) 2#
             Mean for order                  5.25 (0.51) 18#

Organosol    Hard rock                       Not Available
             Basin peat                      Not Available
             Mean for order                  Not Available

Podosol      Sandstone/mudstone              5.27 (0.65) 8#
             Coastal sands                   5.78 (1.22) 6#
             Quaternary alluvium             Not Available
             Mean for order                  5.32 (0.95) 23#

Rudosol      Sandstone/mudstone              Not Available
             Quaternary deposits             Not Available
             Mean for order                  Not Available

Sodosol      Mudstones/sandstones            5.80 (0.45) 7#
             Dolerite                        5.57 (0.38) 3#
             Quaternary alluvium             5.54 (0.32) 5#
             Tertiary sediments              5.47 (0.54) 13#
             Mean for order                  5.64 (0.62) 32#

Tenosol      Coastal dunes                   Not Available
             Inland dunes                    6.89 (1.34) 17#
             Hard rocks, dolerite            Not Available
             Hard rocks, sandstone/          5.49 (0.64) 5#
             mudstone
             Mean for order                  6.44 (1.35) 34#

Vertosol     Basalt                          Not Available
             Dolerite                        Not Available
             Tertiary sediments              Not Available
             Quaternary alluvium             6.25 (0.13) 4#
             Mean for order                  5.86 (0.57) 7#

Total                                        5.79 (0.84) 279#

Soil Order   Parent material            Organic             TEB
                                      carbon (%)       (cmol(+)/kg)
                                         (A)                (A)

Calcarosol   Total/mean for order    1.6 (0.72) 2#      Not Available

Chromosol    Dolerite                4.9 (3.99) 7#      11.5 (5.60) 7#
             Mudstones/sandstones    3.3 (1.42) 8#      8.0 (3.62) 6#
             Tertiary Sediments      3.0 (1.05) 13#     7.2 (4.54) 13#
             Mean for order          3.6 (2.07) 39#    10.2 (6.97) 36#

Dermosol     Dolerite                6.5 (2.42) 4#     24.2 (8.22) 4#
             Mudstones/sandstones    3.8 (1.81) 11#    10.5 (8.55) 11#
             Granite                 Not Available     Not Available
             Tertiary sediments      3.7 (2.04) 5#     20.3 (8.52) 5#
             Mean for order          4.9 (3.53) 28#    16.3 (10.27) 36#

Ferrosol     Basalt                  5.7 (2.43) 17#    14.6 (10.95) 12#
             Dolerite                9.0 (1.55) 4#     24.3 (8.31) 3#
             Mean for order          6.5 (3.25) 27#    17.4 (11.13) 21#

Hydrosol     Tertiary sediments      2.4 (0.18) 2#      6.6 (5.61) 2#
             Quaternary alluvium     5.0 (1.90) 4#     17.7 (0.62) 2#
             Mean for order          4.0 (2.38) 12#     9.0 (6.29) 8#

Kandosol     Tertiary sediments      Not Available     Not Available
             Sandstone/mudstone      4.2 (3.03) 6#      8.1 (5.60) 6#
             Quaternary alluvium     1.0 (1.27) 2#     10.3 (6.27) 2#
             Mean for order          3.7 (2.21) 15#    10.3 (6.25) 14#

Kurosol      Mudstones/sandstones    5.1 (1.07) 2#     12.9 (10.37) 2#
             Tertiary sediments      3.6 (1.07) 2#      4.9 (1.14) 2#
             Mean for order          4.6 (2.02) 18#     9.2 (6.35) 14#

Organosol    Hard rock               Not Available     Not Available
             Basin peat              Not Available     Not Available
             Mean for order          Not Available     Not Available

Podosol      Sandstone/mudstone      4.6 (1.61) 7#     11.1 (7.67) 6#
             Coastal sands           4.1 (2.25) 4#      7.3 (5.16) 4#
             Quaternary alluvium     Not Available     Not Available
             Mean for order          4.3 (2.07) 18#     7.9 (6.12) 15#

Rudosol      Sandstone/mudstone      Not Available     Not Available
             Quaternary deposits     Not Available     Not Available
             Mean for order          Not Available     Not Available

Sodosol      Mudstones/sandstones    2.6 (0.87) 5#      9.3 (5.73) 6#
             Dolerite                Not Available     Not Available
             Quaternary alluvium     3.7 (1.59) 3#      7.6 (6.91) 3#
             Tertiary sediments      3.2 (2.51) 12#     5.6 (2.71) 11#
             Mean for order          2.9 (1.92) 26#     7.1 (4.83) 24#

Tenosol      Coastal dunes           Not Available     Not Available
             Inland dunes            3.9 (2.98) 15#    11.2 (5.22) 9#
             Hard rocks, dolerite    Not Available     Not Available
             Hard rocks, sandstone/  2.5 (3.35) 2#     10.9 (4.35) 2#
             mudstone
             Mean for order          3.8 (2.46) 26#    11.3 (5.47) 15#

Vertosol     Basalt                  Not Available     Not Available
             Dolerite                Not Available     Not Available
             Tertiary sediments      Not Available     Not Available
             Quaternary alluvium     4.8 (3.14) 3#     31.5 (14.73) 3#
             Mean for order          4.6 (2.60) 5#     34.4
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