Dominant soil orders in Tasmania: distribution and selected properties.
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
Additional keywords: classification, mapping, landuse, land systems.
Soils (Chemical properties)
|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|
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.
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).
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.
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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