Ag Heartlands Tour Guide

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Itinerary for Agricultural Heartlands fieldtrip

Monday, 26th July Sydney to Scone

Time Location Activity

0730 Depart The University of Sydney –

en route Sydney Basin geology Brief rest stop on F3

1030 Oakey Creek Rd, Pokolbin SBP1 – Brown Sodosol1

1300 Pokolbin Community Hall Lunch, presentations

1430 Marrowbone Rd, Pokolbin Limestone/Marl cutting

1430 Marrowbone Rd, Pokolbin SBP2 – Shelly Calcarosol

1600 Drayton’s Family Wines Wine tasting

1900 Scone Motel & Dining

Tuesday 27th July Scone to Gunnedah


0730 Depart Scone –

en route Dairy & horse farming

0930 Nowley Farm, Spring Ridge Welcome/ morning tea

1015 Nowley Farm SBP3 – Red Chromosol

1230 Nowley Farm Lunch

1400 Nowley Farm SBP4 – Brown Sodosol

1830 Gunnedah Motel

1900 Wild Orchid Dinner

1 Will also include and refer to these in WRB and Soil Taxonomy in final documentation.

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Wednesday 28th July Gunnedah to Narrabri


0730 Depart Motel Gunnedah –

0900 Pilliga Pottery Morning tea

1000 Pilliga Scrub, Newell Highway 23 km north of Coonabarabran

SBP5 – Orthic Tenosol

en route Edgeroi soil mapping

1330 ‘I.A Watson’, Narrabri Lunch‐ Wheat breeding, conservation tillage and carbon measurement and management

1430 ‘I.A Watson’, Narrabri SBP6 – Grey Vertosol

1600 ‘I.A Watson’, Narrabri SBP7– Brown Dermosol ‐ stratigraphy

1800 Narrabri Motel

1900 Crossing Theatre “Riverside Room” Dinner

Thursday 29th July Narrabri to Goondiwindi


0730 Depart Motel Narrabri –

en route Sawn Rocks

1000 ‘Romaka’ Tery Hie Hie Morning tea Precision Ag. Research

1030 ‘Romaka’ Tery Hie Hie SBP8 – Red Dermosol WASHED OUT

1300 Moree Lunch

1515 ‘South Callandoon’, Goondiwindi SBP9 – Grey Vertosol Alluvia, Gilgai, Cotton growing

1700 ‘South Callandoon’, Goondiwindi Demonstration of Vis‐NIR probe

1800 Goondiwindi Motel

1900 Queensland Hotel Dinner

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Friday 30th July Goondiwindi to Toowoomba


0745 Depart Goondiwindi –

en route Geological history

0820 Wondalli SBP10 –Gilgaied Grey Vertosol

0935 Yelarbon SBP11 – alkaline soil with unique vegetation, cultural heritage site

1130 Gore SBP12 – gravelly soil

1315 Karara SBP13 – Bulloak Sodosol

1450 Pampas SBP14 – Black Vertosol, lysimeters, geophysics

1700 Toowoomba SBP15 – Red Ferrosol

1800 Toowoomba Motel

1900 Fitzy Magees “Gaelic Room” Dinner

Saturday 31st July Toowoomba to Brisbane


0745 Depart Motel Toowoomba –

en route Enjoy scenery

0915 Esk Morning Tea

1015 Toogoolawah SBP16 – Orthic Tenosol

1200 Kilcoy Lunch

1300 Wamuran SBP17 – Yellow Chromosol

1530 Drop off at hotels

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Tour participants

Name Email address

Tour Leaders

Stephen CATTLE [email protected] FIELD [email protected]. McBRATNEY [email protected] SHORT [email protected] SINGH [email protected]

Delegates

Sonya AHAMED [email protected] BAO [email protected] BURGHARDT [email protected]; [email protected]

Xiaoqin CHEN [email protected] COLINET [email protected] (Seppe) DECKERS [email protected] DEMPSTER [email protected] EBERHARDT [email protected] FOX [email protected] FUJITAKE [email protected] GARCIA‐CALDERON [email protected]; [email protected]

Ute HAMER [email protected] HARTIKAINEN Jon HEMPEL [email protected] HENRIQUEZ [email protected] KATO [email protected] LEVIN [email protected]; [email protected] Bill McFEE [email protected] MICHELI [email protected] POTTER [email protected] REINSCH [email protected] REINSCH [email protected] ROYER Peter SCHAD [email protected] SCHOLTEN [email protected] TANI [email protected] VACCA [email protected] Van HUYSSTEEN [email protected] VanCAMPENHOUT [email protected] VENALAINEN [email protected]‐Yan WANG [email protected];[email protected] Larry WEST [email protected] WEST [email protected] YIN [email protected] ZHOU [email protected]

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Agricultural Heartland tourists at “Nowley”, July 27th, 2010

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Figure 2: Tour Route

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Figure 3: Day 1, July 26th


Day 1

Day 2

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Day 3

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Day 4

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Day 5

Day 6

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Figure 9: Profiles within and catchment features of the Liverpool Plains area.

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Figure 10: Hunter Valley profiles

Figure 11: Nowley profiles

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Figure 12: Pilliga profile

Figure 13: IA Watson profiles

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Figure 14: Terry Hie Hie profile

Figure 15: Goondiwindi Profile

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Figure 16: Wondalli profile

Figure 17: Yelarbon profile

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Figure 18: Gore (Traprock) profile

Figure 19: Karara profile

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Figure 20: Pampas profile

Figure 21: Profile 15‐ Toowoomba

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Figure 22: Toogoolawah profile

Figure 23: Wamuran profile

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Overview of the Geology of the Sydney‐Gunnedah Basins in NSW

New South Wales which lies in the east of the Australian Plate is bordered to the east by the adjacent oceanic lithosphere of the Tasman Sea. The nearest active margin passes through New Zealand, where the region between the coast and oceanic crust comprises a narrow continental shelf consisting mainly of continental sedimentary rocks. The coast and the inland region are dissected by the Eastern Highlands with the Great Dividing Range at the crest. These highlands are believed to have been uplifted due to the addition of igneous rocks from below (underplating). The lower part of the Sydney Basin is adjacent to the coast and forms the southern part of the Sydney‐Gunnedah‐Bowen Basins (Figure 1) which are bound by the New England and Lachlan Fold Orogen (Belts) as detailed below.

Figure 1. Map of the Tectonic units comprising New South Wales. The region west of the Eastern Highlands have subsided creating the Murray‐Darling Basin (Figure 2) resulting in river systems that commence in Queensland and flow to the west and south west meeting the ocean near Adelaide in South Australia. The eastern tectonic units that comprise the Murray‐Darling Basin include the; Bowen Basin, Clarence‐Morton Basin, Lachlan Fold Belt, New England Fold Belt, Gunnedah Basin, Upper Sydney Basin, and Surat Basin. Details of all tectonic units are given in (Figure 1) and the surface geology in (Figure 4).

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Figure 2: Map of the tectonic units housed by the Murray Darling Basin

The Sydney Basin

This is a major structural basin comprising a Permian to Triassic sedimentary sequence (290 Ma – 200 Ma) that has a maximum total thickness in the range of 5000 m. This forms the southern part of the Sydney‐Gunnedah‐Bowen basin system. The basin is surrounded to the south and west by the older, largely low‐grade metamorphic and granitic rocks of the Ordovician to Devonian Lachlan Fold Belt. The eastern part of the basin continues offshore to the edge of the continental shelf, while to the north, the basin is bound by the Devonian to Carboniferous New England Fold Belt and transitions into the contemporaneously developed Gunnedah basin to the north west.

The basin was initiated by crustal rifting in the Early Permian where the earliest depositions consisted of volcanogenic sands and silts deposited in a marine shelf. Along with basaltic island volcanoes in the lower Hunter this region forms the Dalwood and Lower Shoalhaven Groups (Table 1). Sediment shed from compression of the New England Fold belt was responsible for the deposition of the Greta Coal Measures in the north of the basin near Muswellbrook and Cessnock. Basement sagging led to increased marine conditions toward the top of the Greta Coal Measures, where in the west of the basin, sourced volcanogenics derived New England and quartz rich sand and silt derived from the Lachlan, forming the Maitland and upper Shoalhaven Groups. Faulting and folding of the New England Fold Belt resulted in the Hunter‐Bowen Orogeny which resulted in the delta plain and fluvial conditions forming the late Permian Tomago and Whittingham Coal Measures in the in the Muswellbrook‐Denman‐Singleton of the northern Hunter area, and the deposition of the lower Illawarra Coal Measures in the south of the basin (Table 1).

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Table 1: Simplified stratigraphic sequence of the Permo‐Triassic Sydney Basin. The lithology of the basin differs from north to south and is detailed in Figure 2.

Years (Ma)

Period Formation Lithology

WIANAMATTA GROUP Consists of three main formations called the Ashfield Shale (shale, siltstone, claystone), Minchinbury Sandstone (sandstone) and Bringelly Shale (shale, sandstone)

MITTAGONG FORMATION

Thin sandstone beds

HAWKESBURY SANDSTONE

Quartz rich sandstone with abundant cross‐bedding and inter‐bedded shale

205

TRIASSIC

NARRABEEN GROUP Lithic and quartz rich sandstones, siltstones

ILLAWARRA, TOMAGO & NEWCASTLE COAL

MEASURES

Abundant thick coal seams, sandstone, shale, conglomerate (with abundant fossils)

MAITLAND & SHOALHAVEN GROUPS

Siltstone, sandstone, shale, conglomerate; including the Gerringong Volcanics

GRETA COAL MEASURES Sandstone, shale, conglomerate , coal seams

251

298

PERMIAN

DALWOOD and LOWER SHOALHAVEN GROUPS

Calcareous sandstone, conglomerate, shale, limestone, lava flows and tuff

Coal measure development was terminated by a marine incursion forming the Dempsey and Denman formation in the north and Bargo claystone and Baal Bone formation in the south. The regression continued forming a meandering stream which dominated the alluvial plain, and in the north was responsible for the formation of the Newcastle and the Wollombi Coal Measures (completing the Singleton Supergroup). In the south it formed the upper Illawarra Coal Measures, effectively filling the basin.

Renewed uplift of the New England Fold belt in the early Triassic resulted in the deposition of the Narrabeen Group in an alluvial flood plain and estuarine environments, which can be found in the western regions of the Hunter Valley. During this period, sedimentation varied between the New England derived mixed load and quartz rich Lachlan. Uplift of the Lachlan Fold Belt or subsidence of the New England Fold Belt resulted in the deposition of the quartz rich Hawkesbury Sandstone, which is overlain by the Wianamatta Group (Table 1).

Jurassic age igneous activity resulted in the formation of the Prospect dolerite and diatremes over the eastern basin, while late Mesozoic activity resulted in the formation of numerous coastal dykes on the central coast and basaltic caps on Mount Banks, Wilson, and Tomah in the Blue Mountains. Only minor folding has occurred resulting in the Lapstone monocline in the east foothills, and further west, the Tomah Monocline in the Blue Mountains. Most of the unconsolidated material is Cainozoic or Quaternary in age, with significant thicknesses of up to 80 m being deposited in coastal depressions such as Botany Bay. The humid conditions of the Cainozoic resulted in the formation of well developed lateritic soils on the Hawkesbury Sandstone, Narrabeen and Wianamatta Groups.

Greater Sydney is developed on the Cumberland Plain, which is drained by the meandering creeks of the Hawkesbury and Parramatta Rivers. Much of the plain is covered by texture contrast or duplex acidic soils and uniformed textured alluvial derived soils of the river terraces. These soils are characteristic of much of the east coast of Australia and extend into the Great Dividing Range. The plateaus, such as the Blue Mountains and Hornsby that rise abruptly from the Cumberland Plain have coarse textured soils derived from the Hawkesbury sandstone, along with iron rich uniform clay soils derived from the isolated basalt occurrences. In this area, Hanging Swamps with organic rich soils can also be found. To the north in the Hunter Valley, the Broken Back Range is comprised of the

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Narrabeen capped by the Hawkesbury sandstone resulting in thin uniformly coarse textured soils. The areas around Cessnock and Singleton are underlain by the Dalwood and Maitland Group resulting in texture contrast acid soils. The presence of limestone in the area has resulted in the occurrence of uniform clays. Alluvial soils are common skirting the Hunter River and its tributaries.

The Gunnedah Basin (& Surat Basin)

This forms the central part of the Sydney‐Gunnedah‐Bowen Basin system and is unconformably overlain by the Surat Basin (Jurassic and Cretaceous Strata). The basin covers an area of over 15, 000 square kilometres and is comprised of rocks of Permian and Triassic in age. This basin is bound by the New England Fold Belt in the east and as with the Sydney basin, the west is bound by the Lachlan Fold Belt. The northern boundary with the Bowen Basin is believed to be marked by the highly eroded early Permian sediments north of Narrabri. The southern boundary with the Sydney basin is suspected to be either the Mount Coricudgy Anticline or Liverpool Range.

Deposition in the basin is marked by colluvial and alluvial material followed by an influx of vocanolithic sediments from the Boggabri Ridge. This forms the early Permian Bellata Group which is comprised of the Leard Formation and Maules Creek Formation, and is equivalent to the Greta Coal Measures of the Sydney Basin (Figure 3). They gave way to progressively marine conditions and the development of a marine shelf, the resulting deposition of the Porcupine and Watermark Formations outcropping on the eastern perimeter between Quirindi to Narrabri, and which are of similar age to the Maitland and lower Shoalhaven Groups of the Sydney Basin. The development of deltas in the late Permian resulted in the sediments of the Black Jack Group outcropping near Boggabri and Gunnedah (Table 2). The shallow marine facies of the Arkarula Formation gave way to delta environments resulting in widespread peat development forming the Hoskisson Coal. This was followed by increased alluvial development marking the upper part of the Black Jack Group and the end of the Permian sedimentation.

Techtonism of the New England Fold belt in the early Triassic resulted in the deposition of coarse clastic sediments forming the Digby Formation (Table 2), which is considered equivalent to the Narrabeen Group in the Sydney Basin. Outcrops can be found on the eastern perimeter between Quirindi to Narrabri. Howevver, the large deltas that were forming the Hawkesbury Sandstone in the Sydney basin did not occur further north but gave way to more moderate lacustrine and delta conditions and were responsible for the formation of the Napperby Formation in the Gunnedah Basin (Figure 3).

The Jurassic and Cretaceous sediments of the Surat Basin uncomfortably overlay the Gunnedah Basin in the north and west and form thick sequences in the northwest (Table 2). The course textured quartz sandstone of the Pilliga Sandstone outcropping between Baradine and Baan Ban , result in what is termed the Pilliga Scrub, and forms the main basement rocks for the region around and north of Narrabri. This is underlain by the clayey sands and mudstones of the Purlawaugh Formation and Garrawilla Volcanics (Table 2). The Pilliga Sandstone is overlain by the Orallo Group and Rolling Downs Group. The calcareous clays and marls of the Rolling Downs are found north of Narrabri, as are the Nandewar Volcanics. Much of the basin in the vicinity and north of Narrabri and west of Coonabarabran and Gilgandra are covered with undifferentiated post Jurassic sediments.

The Liverpool Plains forms an extensive physiographic unit covering the Lower Gunnedah Basin. The plain includes deep Quaternary alluvium of the Mooki River floodplain and is occasionally influenced by the Naomi river floodplain. The deep alluvium of the Goran Basin Plains can be found, and is associated with the lunettes and beaches forming the margins of Lake Goran.

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Table 2: Simplified stratigraphic sequence of the Permo‐Triassic Gunnedah Basin and the Jurassic Section of the Surat Basin.

Years (Ma)

Period Formation Lithology

LATE ORALLO FORMATION Clayey to quartzose sandstone, subordinate siltstone and conglomerate

PILLIGA SANDSTONE Fluvial, medium to coarse‐grained quartzose sandstones

MIDDLE PURLAWAUGH FORMATION

Carbonaceous claystone, siltstone, sandstone and subordinate coal.

141

159

184

205

JURASSIC

EARLY GARAWILLA VOLCANICS Alkali basalt, trachytes, hawaiite, pyroclastic and subordinate sediments

DERIAH FORMATION Green lithic sandstone rich in volcanic fragments and mud clasts

MIDDLE NAPPERBY FORMATION

Thinly bedded claystone, siltstones and sandstones, common bioturbation and burrows

230

241

TRIASSIC

EARLY DIGBY FORMATION Lithic and quartz conglomerates, sandstones and minor finer gained sediments

BLACK JACK GROUP

Dominantly fluvial and lacustrine sediments; lithic and quartz sandstones and conglomerates, siltstone and clay tuff and coal.

WATERMARK FORMATION

Regressive marine sediments; sandy siltstone, sandstone, common bioturbation sporadic erratics and secondary calcite “cone‐in‐cone” replacements

LATE

PORCUPINE FORMATION Marine shelf sediments; lithic sandstone and conglomerate and bioturbated mudstone

MAULES CREEK FORMATION

Fluvial; dominantly lithic and subordinate quartz‐rich sandstones and conglomerate

GOONBRI and LEARD FORMATIONS

Colluvial and lacustrine sediments; pelletoidal claystone and upward coarsening sequences of organic‐rich claystone to sandstones

251

270

298

PERMIAN

EARLY

BOGGABRI VOLCANICS Mainly Rhyolite flows and pyroclastics

PRE‐PERMIAN

LACHLAN FOLD BELT Metavolcanics and Metasediments

Texture contrast soils are found between Curlewis and Lake Goran and are related to the Permian and early Triassic sediments. The texture contrast and sometimes sodic soils of Trinkey forest are derived from the Jurassic Purlewaugh Formation and Pilliga Sandstone. In and around Mullaley the Garawilla Volcanics provide material for the uniform cracking clay soils found. Some of the local mountains are capped with Tertiary basalts forming uniform clay soils in their footslopes. Further north the outcrop of the Pilliga Sandstone has provided uniform coarse profiles. In the areas north and west of Narrabri extensive alluvial plains representing the Quaternary history of the Darling River Basin are developed by meandering river systems, such as the Namoi River. The use of thermoluminescence has placed these sediments as between 5.6 ka to 56 ka. The weathering products of the basic volcanics capping the Nandewar Range and surrounding areas may have contributed to the clay sediments in the area. Selected outcrops of the Gunnedah and Surat rock formations at the base of the mountain ranges to the east of Narrabri have resulted in the development of texture contrast soils.

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Figure 3: Correlation of the lithostratigraphic units of the Gunnedah and Sydney Basin.

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Figure 4: Surface Geology of New South Wales

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Day 1 Sydney to Scone

Presenters:

Marcelo Stabile

PhD candidate, Faculty of Agriculture Food and Natural Resources,

The University of Sydney

Email: [email protected]

Brendan Malone

PhD candidate, Faculty of Agriculture Food and Natural Resources,



Ken Bray

Hunter Wine Country Private Irrigation District

also

Braemore Wines

820 Hermitage Road,

Pokolbin 2320


John Drayton

Drayton’s Family Wines

555 Oakey Creek Road, Pokolbin 2320


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A brief history of the lower Hunter and our research

Marcelo Stabile, Inakwu Odeh, Alex McBratney


The Hunter Valley is now well known for its wine and for its attractiveness to domestic

and international visitors; this is closely related to the area’s development which has

happened in recent decades. Undoubtedly the success of the Hunter relies on the wine and

tourism. In fact, the first plantations of wine grapes were established in the 1800s, but

declined towards the end of that century due to the depression (O'Neill 2000).

The early 1980s were characterised by removal of grape vines with government subsidies,

however in the 1990s smaller plots were planted along with the establishment of the tourism

industry. McManus (2008) pointed out that even though the climate and soils of the Hunter

were not optimal for wine making, the chief reason for the region’s success was related to its

proximity to major urban centres, such as Sydney and Newcastle. Moreover, ease of access,

with expansion of roads in the 1990s, also contributed to the area’s development.

In order to understand how this shift has transformed the Hunter, characterisation of the

area was necessary and has been done previously (Stabile et al. 2008). Land‐use and ‐cover

maps of the area were made at selected time intervals, following the broadest level of the

Australian standards (ACLUMP, Bureau of Rural Sciences 2006).

Table 1 summarises the composition of the Hunter’s landscape, where it could be seen

that from the mid 1990s there was significant increase in the area of irrigated agriculture,

dominated by wine grapes, as well as significant expansion of intensive uses, characterised by

the construction of parks, golf courses and hotels.

As a form of comparison, in the 1970s the combined area of intensive uses and irrigated

agriculture corresponded to roughly 12% of the landscape, while in 2005 they represented

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over 17.5% of the area. Since then the number of visitors in the region has increased steadily

(Figure 1), as has the population (Figure 2).

Table 1: Proportions of land‐use and land‐cover

% of Area 1972 1985 1995 2000 2005

Woodland 37.08 31.79 35.98 34.47 36.78 Dryland Agriculture 50.27 55.96 50.81 50.80 44.96 Irrigated Agriculture 10.69 9.53 10.25 10.15 13.52

Intensive uses 1.75 2.13 2.49 3.77 4.10 Water 0.21 0.60 0.47 0.81 0.63

1000000

2000000

3000000

4000000

5000000

6000000

7000000

2001-2002 2002-2003 2003-2004 2004-2005 2005-2006 2006-2007 2007-2008

Vis

itor

s

Period

Day

Overnight

Figure 1: Annual number of visitors (Tourism New South Wales 2009)

0

10000

20000

30000

40000

50000

60000

1976 1981 1986 1991 1996 2001 2006 2011 2016 2021 2026

Reg

iona

l Pop

ulat

ion

Year

Cessnock

Singleton

Cessnock Proj

Singleton Proj

Figure 2: Population and projections (Australian Bureau of Statistics 2009, Hunter Valley Research

Foundation 2009)

Our research aims at understanding the causes of this change and predicting the

landscape’s configuration in the future. For this, we have built a hybrid, Markov‐Cellular

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Automata model which utilises the neighbourhood configuration to dynamically change

transition probabilities for each pixel.

Currently the model can handle 4 or 8 neighbours and the user can specify the weight of

the CA component (1‐WTM), thus allowing the model to run exclusively on Markov mode

(solely on transition probabilities), on CA mode (transition only related to neighbourhood) or

any combination of both. The model was implemented in R, and thus complexity such as

areas of exclusion and suitability layers could easily be added.

An illustration of the model’s outcomes can be seen in Figure 3. Panel A illustrates the

landscape conditions in 2005 (Cessnock on the lower right). Panel B illustrates the simulated

landscape for 2020, when transition probabilities were driven from predicted climatic

patterns and the model run on CA mode (WTM 0). Panel C shows the outcome of empirically

derived transition probabilities and the model run with WTM=0.5. Panel D, finally, refers to

when the model was run with transition probabilities derived from projections of population

and in Markov mode (WTM=1).

Empirically derived transition probabilities suggested significant increase in the areas of

irrigated Agriculture and of intensive uses. Other transition probabilities, however, such as

the ones derived from population and climate, did not significantly alter the landscape’s

composition.

Further enhancement of the model would include: utilising more than 8 neighbours for

the CA component, implementation of other layers of information for modifying transition

probabilities and utilising a combination of spatial ancillary variables for modifying the

transition probabilities as well.

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Figure 3: Initial conditions and simulated outcomes form the Hybrid model

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Cited References:

AUSTRALIAN BUREAU OF STATISTICS, 2009, Census of population and housing (Canberra: ABS).

BUREAU OF RURAL SCIENCES, 2006, Guidelines for land use mapping in Australia: principles, procedures and definitions. 3rd edition, Bureau of Rural Sciences.

HUNTER VALLEY RESEARCH FOUNDATION, 2009, Newcastle and the Hunter region 2008‐2009, edited by R. McDonald, and M. Jonita (Maryville, NSW: HVRF).

MCMANUS, P., 2008, Mines, Wines and Thoroughbreds: Towards Regional Sustainability in the Upper Hunter, Australia. Regional Studies, 42, 1275 ‐ 1290.

O'NEILL, P., 2000, The gastronomic landscape. In Journeys: the making of the Hunter Region, edited by P. McManus, P. O'Neill, R. J. Loughran, and O. R. Lescure (St. Leonards, NSW: Allen & Unwin), pp. 158‐185.

STABILE, M. C. C., ODEH, I. O. A., and MCBRATNEY, A. B., 2008, Application of object‐oriented and knowledge‐based approach to multi‐temporal land use classification using Landsat images: 14ARSPC: Proceedings of the 14th Australasian Remote Sensing and Photogrammetry Conference.

TOURISM NEW SOUTH WALES, 2009, Hunter Valley tourism statistics, HVRF.

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An additional criterion for assessing the quality of digital soil attribute maps: The areal proportion of the map within a specified prediction interval.

Brendan P. Malone*A, Jaap J de GruijterB, Alex B. McBratneyA, Budiman MinasnyA

AFaculty of Agriculture Food & Natural Resources, The University of Sydney, NSW 2006, Australia. BWageningen University and Research Centre, Wageningen, The Netherlands. [email protected], [email protected], [email protected],

[email protected]

Summary

In this paper we present a new criterion in which to assess the quality of digital

soil property maps. Where soil map quality is estimated on the basis of validating

both the accuracy of the predictions and their associated uncertainties

simultaneously. At the core is a stratified simple random sample design, where the

stratifying variables are the mapped predictions and their uncertainties.

A soil pH map was validated using 100 sampling units, further sub-sampled at 5

depth increments. The indicator of map quality is the total proportion of the area in

the map that fit within a prescribed prediction interval (PI). At a 95% confidence level,

based on this indicator, the pH map is of high quality where 84% of the area is

adequately mapped. Further analysis revealed that map quality was strongest at the

surface (96%) but decreased with depth to 1m (81%). Suggestions for further

investigations are presented.

Introduction

The soil map is regarded as an efficient medium in which to convey information

about the variability of soils across a defined area. In recent times, soil mapping has

become popularised because of the dual drivers of demand and advances in

technology. Ensuring the highest standard of map quality possible must and should

remain a fundamental element of soil mapping.

Generally, soil map quality has been related to measures of uncertainty (Finke

2006). For example, traditional polygon-based maps used two measures of

stochastic uncertainty, namely the purity of mapping units and the variance of

individual properties within mapping units (Burrough et al. 1997). For digital soil maps

however, prediction outputs are naturally accompanied by some corresponding

measure of uncertainty. Uncertainties are conventionally based on measures of

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variance between observed and predicted values such as the co-efficient of

determination (R2), root mean square error (RMSE) and mean error (ME) and

accompany maps which display the magnitude of the predicted soil property or class

only (Bishop et al. 2001; Lagacherie 2008). Occasionally the map producer will

derive a separate map of the prediction uncertainties to indicate where predictions

are most and least reliable (Bishop et al. 2001).

Because we can dually generate predictions and uncertainties, we believe that the

indicator of map quality should simultaneously assess the quality of the prediction

outputs and their uncertainties. In this paper we demonstrate a robust quality

measure of soil maps using independent sampling units where we test the quality of

the predictions and their uncertainties. It is such that the indicator of map quality is

the proportion of the total map area correctly predicted within a specified prediction

interval. We discuss the methodology for obtaining the sampling units and the

subsequent results in terms of map quality.

Material and Methods

Study area

The study area selected for this study is an approximately 220 km2 area just north

of the town of Cessnock (32.83°S 151.35°E) in the Lower Hunter Valley,

approximately 140 km north of Sydney, NSW, Australia. This area is part of the

Sydney Basin where parent materials are composed mostly of Mesozoic sandstones

and shales. Topographically, this area consists mostly of undulating hills that ascend

to low mountains to the south-west. In terms of landuse, dryland agricultural grazing

systems are predominant, followed by an expansive viticultural industry. While most

of the land has been dedicated for these uses, tracts of remnant natural vegetation

(dry forest) are apparent, particularly towards the south-western (Brokenback

Mountains), eastern (Werakata National Park) and northern margins of the study

area.

Soil map to be validated

The map to be validated in this study is a soil pH map with grid spaced point

estimates, 25m apart. This map depicts the vertical and lateral distribution of soil pH

across the study area to 1m and was generated following the procedure of Malone et

al. (2009) which uses an amalgam of soil depth spline functions and DSM

techniques. The map was generated using a regression kriging approach where the

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predictions were based on a calibration dataset of 994 legacy soil profile descriptions

distributed across the area.

Corresponding with the DSM predictions of soil pH were estimates of uncertainty

associated with each prediction. Uncertainty was calculated empirically following the

procedure of Malone et al. (2010), an extension of the Shrestha and Solomatine

(2006) method, where uncertainty is expressed in the form of a prediction interval

(PI) of the underlying distribution of prediction errors. The PI represents a 95%

confidence level. What is generated from this method are upper and lower prediction

limits associated with each point. These were also mapped and are shown in Figure

4 (0-10cm shown only).

Figure 4: Mapped soil pH across the PID study area at 0-10cm.

Because we have accounted for the perceived uncertainties associated with the DSM

predictions. The validation technique attempts to determine the proportion of

additional observations that fit within the range of the upper and lower prediction

limits at fixed depths.

Determination of sampling sites

A stratified simple random sampling scheme (de Gruijter et al. 2006) was used to

determine the locations of the sample sites for which soil pH was to be laboratory

analysed at specified depth increments. We used two stratifying variables: the

averaged whole-profile prediction of pH and an uncertainty measure; the average

whole-profile difference between the upper and lower prediction limits.

The averaged prediction and the uncertainty measure for each point were

arranged in a table, where four equal-area area strata were created. These were

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ultimately characterised as being either low or high pH and either low or high

uncertainty where the thresholds were determined empirically from the data (Table

2).

Table 2: Characteristics (thresholds) of each stratum based on the two stratifying variables.

Stratum pH prediction Uncertainty (95% PI)

A Low (≤ 5.88) Low (≤ 2.58)

B High (>5.88) Low (≤ 2.58)

C Low (≤ 5.88) High (>2.58)

D High (>5.88) High (>2.58)

Soil sampling

Forty (40) potential sampling units (PSUs) were randomly selected from each

stratum. In the order in which they were selected, the first 25 were designated as

actual sampling units (SUs). The SUs could be sampled in no particular order. In the

event that an SU could not be sampled through such circumstances as permission

denied from a landholder to access property or difficult terrain and inaccessibility etc,

the first of the remaining 15 PSUs was selected on so on until the number of SUs for

each stratum totalled 25.

The SUs were soil cores of between 100-120 cm in length and a diameter of 5

cm. These were taken using a hydraulic geoprobe soil corer mounted on the back of

a truck/all terrain vehicle (ATV).

Laboratory analyses

Each SU was sub-sampled corresponding to the depth intervals of: 0–5cm, 5–

15cm, 15–30cm, 30–60cm, 60–100cm. Once mixed a small aliquot from each sub-

sample was taken to be laboratory analysed using the 1:5 soil:water suspension

method to determine soil pH (Rayment and Higginson, 1992).

Results and discussion

The PI represents a 95% confidence level. Ideally results would indicate that 95%

of observed results (aliquots) would fit within their prescribed PI. Results of the

proportion of correct PI at each depth increment and within each stratum are shown

in Table 3. Irrespective of depth increment we found that 84% of all aliquots fitted

16

within their PI. This is an encouraging result, but immediately indicates an

underestimation of uncertainty because it is below the ideal 95% mark.

Table 3: Proportion of aliquots that fitted within their prescribed prediction intervals at each

depth increment and within each stratum.

Depth (cm) Stratum A Stratum B Stratum C Stratum D Total

0–5 96% 96% 92% 100% 96%

5–15 76% 92% 88% 96% 88%

15–30 84% 84% 80% 76% 81%

30–60 76% 68% 76% 76% 74%

60–100 84% 68% 80% 92% 81%

Average 83% 81% 83% 88% 84%

Stratifying the results by the depth increments revealed that at 0–5 cm PIs were

ideal if a little overestimated where 96% of aliquots were correctly accounted for

(within their prescribed PI). At 5-15cm there was a slight reduction where 88% were

accounted for. This downward trend continued to 15-30cm and 30-60cm were the

proportion of aliquots correctly predicted decreased from 81% to 74% respectively.

There was a slight improvement at 60-100 cm where 81% of aliquots fitted within

their prescribed PIs. The interpretation from these results is that the pH map is of

highest quality at the soil surface but decreases marginally with soil depth.

What can be observed when comparing the results at each depth interval within

each stratum are slight to moderate fluctuations around the mean value at a

prescribe depth. For example the proportion of aliquots accounted for within Stratum

A at 5-15cm was 76 % and 12% lower than then next lowest at stratum C. Similarly at

60-100 cm, the prediction intervals for Stratum B are not nearly as accurate as found

for the other three strata. Generally however, the differences between the strata are

slight where the proportion of correctly assigned PIs ranges between 81–88%.

Because no one stratum is vastly different form the other, assigning a spatial element

to the measure of map quality is difficult at this time. Nevertheless, we will need to

investigate methods for doing this in future studies.

To address the issue of the underestimation of uncertainty we need to look at the

quality of the predictions that accompany the uncertainties. To assess the observed

vs. fitted estimates of all aliquots (500) we firstly queried the corresponding DSM

spline predictions to determine the average pH at the aforementioned depth

17

increments. These were then plotted against the laboratory observed values for each

depth increment (Fig. 5a-e).

Figure 5: Plots of the laboratory measured soil pH vs. the corresponding predicted value at

0-5cm (a), 5-15cm (b), 15-30cm (c), 30-60cm (d), 60-100cm (e).

Overall these results show a moderate agreement between the observed and

fitted values where Lin’s Concordance Correlation Coefficient (CCC) ranged between

0.44 and 0.30, with the strongest predictions at the soil surface (0–5 cm). Similarly

the RMSE at 0–5 cm was 0.62 and gradually increased with depth to 0.7 (5–15 cm),

0.76 (15–30 cm), 1.01 (30–60 cm) and 1.14 (60–100 cm). It can be observed from

the plots that at higher pHs (>7) there is a systematic under prediction, particular at

15–30 cm, 30–60 cm and 60–100 cm (Fig. 5c-e). As a whole, by observing the

RMSEs found for each strata at each depth interval, predicted pHs deviate from their

corresponding observed measurements by between 0.5 and 1.2 pH units.

A further analysis performed was to gauge the level of bias and precision of

predictions within each stratum. Bias was calculated as the mean error (ME) between

observed and predicted values. Precision was assessed as the square root of the

difference between the mean square error (MSE) and ME2. These results are

summarised for each strata at the defined depth increments in Table 4.

18

For all strata there was an observed decrease in the precision of prediction with

depth, with the worst observed for stratum D. The bias estimates were more varied

where for strata A, C and D there was a systematic under prediction (+bias) of pH.

This was particularly pronounced for stratum C where bias was consistently above

0.5 at all depth increments. For stratum B (high pH) bias estimates indicate a

predominant over prediction of pH particularly at the bottom two depth increments.

Table 4: Bias and precision estimates between observed and predicted values of pH at each

depth increment within each strata

Stratum A B C D A B C D

Depth

(cm)

Bias Precision

0–5 0.18 -0.19 0.54 0.04 0.47 0.50 0.57 0.62

5–15 0.46 0.05 0.57 0.22 0.50 0.51 0.72 0.57

15–30 0.26 -0.03 0.45 0.26 0.58 0.71 0.73 0.79

30–60 0.22 -0.41 0.54 0.12 0.88 0.90 0.90 1.13

60–100 0.09 -0.78 0.54 0.03 1.00 0.96 1.00 1.18

Conclusions

The prediction results indicate that bias exists between the observed aliquots and

their corresponding predictions. We have also identified an increasing level of

imprecision of pH predictions with depth. Rather than the method used to calculate

the prediction uncertainties, it is believed that a predominant factor for the lower than

ideal (95%) of correctly prescribed PIs is due to the quality of the predictions.

Nevertheless, we have presented a new criterion for which additional data are

used to determine the quality of a soil map which entailed some measure of the

known uncertainties attached to the predictions. The indicator of map quality in this

study is that 84% of the prediction area is correctly mapped based on a 95%

confidence level. Akin to mapping purities which are used to assess the quality of

polygon-based maps, our results are encouraging and indicate that the pH map used

in this study is of high quality. In such polygon-based maps, mapping purities of

between 70-80% are acceptable but can often be found as being much less than

70% (e.g. Burrough et al. 1971).

We recognise that this criterion is only one indicator of map quality and should be

used as we have done as a compliment to more conventional indicators.

19

Nevertheless, the indicator of map quality we have presented simultaneously derives

measures of map quality based on both the predictions and their associated

uncertainties, for which conventional indicators are unable to do.

We also recognise that there are unknown sources of uncertainty which can not

be accounted for at this point in time. We are also mindful that these results reflect no

spatial component of quality for which further work will be needed to investigate. We

will also need to investigate the efficacy of transference of the same sample units to

validate maps of different soil properties in the same area. Nevertheless, we

envisage that in the future, such quality-based information as we have presented in

this study will accompany digital soil maps in the form of attached metadata.

References

Bishop, T.F.A., McBratney, A.B. and Whelan, B.M., 2001. Measuring the quality of digital soil

maps using information criteria. Geoderma, 103(1-2): 95-111.

Burrough, P.A., Beckett, P.H.T. and Jarvis, M.G., 1971. Relation between cost and utility in

soil survey. Journal of Soil Science, 22(3): 359–394.

Burrough, P.A., vanGaans, P.F.M. and Hootsmans, R., 1997. Continuous classification in soil

survey: Spatial correlation, confusion and boundaries. Geoderma, 77(2-4): 115-135.

de Gruijter, J.J., Brus, D.J., Bierkens, M.F.P. and Knotters, M., 2006. Sampling for Natural

Resource Monitoring. Springer-Verlag Berlin Heidelberg, The Netherlands.

Finke, P.A., 2006. Quality assessment of digital soil maps: producers and users

perspectives. In: P. Lagacherie, A.B. McBratney and M. Voltz (Editors), Digital soil

mapping: an introductory perspective. Elsevier, Amsterdam, pp. 523–541.

Lagacherie, P., 2008. Digital soil mapping: a state of the art. In: A.E. Hartemink, A.B.

McBratney and M.L. Mendonca-Santos (Editors), Digital Soil Mapping with Limited

Data. Springer Science, Australia, pp. 3–14.

Malone, B.P., McBratney, A.B., Minasny B. (in preparation) Empirical estimates of

uncertainty for mapping continuous depth functions of soil attributes.

Malone, B.P., McBratney, A.B., Minasny, B. and Laslett, G.M., 2009. Mapping continuous

depth functions of soil carbon storage and available water capacity. Geoderma,

154(1-2): 138-152.

Rayment, GE & Higginson, FR 1992, Australian Laboratory Handbook of Soil and Water

Chemical Methods. Inkata Press, Melbourne. (Australian Soil and Land Survey

Handbook, vol 3)

Shrestha, D.L. and Solomatine, D.P., 2006. Machine learning approaches for estimation of

prediction interval for the model output. Neural Networks, 19(2): 225-235.

20

Hunter Valley Focus Maps

Figure 6: Sydney University Hunter Valley soil survey efforts

21

Figure 7: Hunter Valley elevation (25m res)

22

Figure 8: Hunter Valley Slope (25m res)

23

Figure 9: Hunter Valley TWI (25m res)

24

Figure 10: Hunter Valley soil classes (to ASC suborder)

25

Figure 11: Soil classes to ASC sub‐order – zoomed

26

1. Location and landscape

Landform This profile is situated mid‐slope on a low hill. In the Hunter Valley, undulating hills with slopes between 6‐12% are dominant.

Parent material or substrate

The most common soil parent materials within the region are shales and mudstones, but smaller amounts of sandstone and limestone are also present. Colluvium and alluvium are significant soil parent materials at lower elevations.

Drainage class Slowly drained, with a moderate run‐on rate and medium run‐off rate.

Surface condition

Soft surface which is currently stable. There is low soil erodibility around the site, which has a low erosion hazard. There is no salinity evident on the surface.

Site disturbance

Extensive clearing of the native vegetation occurred in the late 1800s to early 1900s to make way for pastures and viticulture. The region is now very well known for boutique wine production, with Semillon and Shiraz being the best performed grape varieties in the region. This site has been used for pasture production.

Native vegetation

The dominant vegetation consists of dry schlerophyll forests, with tall woodland stands and shrub/grass understory being most dominant. Two dominant Eucalyptus species present within the region are Eucalyptus fracta and Eucalyptus pumila (Pokolbin Mallee).

Climate The annual average rainfall for the district is 699 mm. The average minimum temperature in July is 3.8oC and the average maximum temperature in January is 30.0oC.

SB Profile 1: Oakey Creek Rd, Pokolbin, NSW

27

0 1 km

New South Wales

Queensland

28

2. Description of soil profile A slow draining Sodosol, derived from shale and mudstone.

Soil morphology

RFP= Red, pale, faint; YPF= Yellow, pale, faint; GPD= Grey, pale, distinct; RDD= Red, dark, distinct; FSCL= Fine sandy clay

loam; SCL= Sandy clay loam; HC= Heavy clay

Australian Soil Classification: Brown Sodosol (SO AB)

World Reference Base: Stagnic Vertic Solonetz (Abruptic, Ruptic, Magnesic, Humic, Clayic)

Soil Taxonomy: Aquertic Natrudalf (Fine, Mixed, Active, Thermic)

Boundary Colour Structure Horizon

Depth (m)

Distinctness Shape Moist Mottles

Texture grade

Grade Shape Size (mm)

Coarse fragments

A₁ A 0‐0.18 Clear Even 10YR 3/2

Very dark greyish brown‐ FSCL Weak Polyhedral 10‐20

<10% stones

A₂ E 0.18‐0.3 Clear Wavy 10YR 4/3 Brown

‐ SCL Massive ‐ ‐ <10% stones

B₂₁ Bt 0.3‐0.5 Abrupt Even 10YR 4/4

Dark yellowish brown ~3% RFP ~2% YPF

HC Strong ‐ ‐ <10% stones

B₂₂ Btn1 0.5‐0.9 Gradual Even 2.5YR 3/6 Dark red

~20% GPD HC Strong ‐ ‐ 10‐50% stones

B/C Btn2 0.9‐1.1 ‐ ‐ 7.5YR 4/2 Brown

~35% RDD HC Moderate ‐ ‐ ‐

A₁

B₂₁

B/C

B₂₂

A₂

A

E

Bt

Btn1

Btn2

29

3. Soil mineralogy

X‐ray diffraction patterns of basally oriented clays show the presence of kaolinite, illite and

an interstratified swelling mineral. The proportion of the interstratified swelling mineral

increased with depth. In addition to the phyllosilicates, the random powder diffraction

patterns identified quartz, anatase, feldspar (plagioclase), lepidocrocite, goethite and

hematite in the soil clay fractions.

X‐ray diffraction patterns of the oriented clay fraction of B21 horizon soil after various pre‐

treatments; Mg saturated and air‐dried (‐‐‐‐‐‐), Mg saturated and ethylene glycolated (‐‐‐‐‐‐), K

saturated and air‐dried (‐‐‐‐‐‐) and K saturated and heated at 550°C (‐‐‐‐‐‐). I/S = interstratified

swelling mineral.

Thin sections

The left image (PPL) shows many small ferromanganiferous inclusions in the clayey matrix of the B21 horizon, while the right image (XPL) shows quite pronounced orientation of clay around grain edges and along pores, suggesting that illuviation has been an important process in this soil.

30

4. Profile chemical characteristics

The pH values for this soil profile are strongly‐slightly acidic (5.29‐6.20) and the soil pH decreases with depth.

EC values range from very low to very high in this profile, with higher EC values towards the bottom of the profile.

Soil organic carbon content is high in the surface soil and declines down the profile.

CECs are very low to moderate for the profile, with the A₂ horizon exhibiting a particularly low value.

Nitrogen levels range from medium‐low and decline down the profile.

C/N ratio ranges from medium ‐ very low.

Chemical properties of soil profile

Cation exchange properties, available micronutrients and DCB and oxalate Fe and Al of soil profile

Horizon pH

(1:5 H2O) EC

(dS/m) Organic C (%)

Total N (%)

C:N ratio

NO₃‐N (mg/kg)

Colwell P (mg/kg)

PBI‐Colwell

SO4 (mg/kg)

Avail. K (mg/kg)

Cl (mg/kg)

A₁ 6.20 0.13 3.56 0.24 14.8 5.2 26 160 12 230 19

A₂ 6.18 0.10 1.75 0.11 15.9 1 5 ‐ ‐ 120 36

B₂₁ 5.65 0.29 1.16 0.11 10.6 1 5 ‐ ‐ 210 130

B₂₂ 5.35 0.69 0.46 0.09 5.1 1 5 ‐ ‐ 120 540

B/C 5.29 0.62 0.21 0.08 2.6 1 5 ‐ ‐ 98 590

Cation exchange properties (mmolc/kg) DTPA extractable (mg/kg) DCB (%) Oxalate (%) Horizon

CEC Ca Mg K Na Al Zn Cu Fe Mn Fe Al Fe Al

A₁ 112 28 44 23 33 1 5.1 0.3 610 24 3.05 0.19 0.4 0.1

A₂ 49 20 23 10 27 3 ‐ ‐ ‐ ‐ 2.79 0.16 0.3 <0.1

B₂₁ 161 9 103 23 57 9 ‐ ‐ ‐ ‐ 3.31 0.29 0.5 0.2

B₂₂ 186 6 117 35 155 8 ‐ ‐ ‐ ‐ 2.71 0.11 0.3 <0.1

B/C 128 6 92 23 127 8 ‐ ‐ ‐ ‐ 1.74 0.05 <0.1 <0.1

A1 A1 A1

A2 A2 A2 A2

B21 B21 B21 B21

B22

B22 B22 B22

B/C B/C B/C B/C

A1

CEC (mmolc/kg)

31

5. Profile physical characteristics

The particle size distribution for this profile shows a very high sand content in the topsoil and very high clay content in the B horizons.

Values of bulk density are moderate to very high and increase with depth. Penetration resistance decreases down the profile, being dense at the top of the profile

and very dense in the underlying horizons.

The water content at permanent wilting point is low in the top 2 horizons but increases in the subsoil horizons.

Soil physical characteristics

Particle size analysis (%) Moisture ()

Horizon Clay

(<2 µm) Silt

(2‐20 µm) Fine sand (20‐200 µm)

Coarse sand (200‐ 2000 µm)

Bulk density (g/cm

3) 10 kPa

1500 kPa (PWP)

0 kPa (FC)

Penetration resistance (MPa)

A₁ 20.1 8.2 63.6 8.1 1.43 0.21 0.06 0.39 1.7

A₂ 22.5 3.3 64.3 9.9 1.53 0.17 0.05 0.34 2.4

B₂₁ 54.8 3.2 28.3 12.0 1.69 0.31 0.24 0.34 2.3

B₂₂ 71.3 3.4 21.3 4 1.92 0.25 0.19 0.27 2.4

B/C 58.3 3.4 33.1 5.2 1.98 0.24 0.19 0.27 ‐

Estimated USDA PSA (%)

Horizon Silt

(2‐50 µm) Sand (50‐2000 µm)

A₁ 21 58.9

A₂ 11.4 66.1

B₂₁ 7.3 37.8

B₂₂ 2.5 26.2

B/C 7.2 34.5

A1 A1 A1 A1

A2 A2 A2

A2

B22

B21 B21 B21

B22

B22 B22

B21

B/C B/C B/C

A1

A2

B21

B22

32


Landform This profile is situated on the upper slope of a steeply sloping hill in the Hunter Valley. A north‐south running ridgeline extends from the mid‐slope of this hill.


The soil parent material at this site is limestone, with many fossilised shells present. The north‐south running ridgeline extending from this site is also comprised of limestone parent material.

Drainage class Well drained, with a low run‐on rate and low‐medium run‐off rate.

Surface condition

Soft surface which is currently stable. Despite the moderately steep slope of this site, the soil erodibility is low and the erosion hazard is low, due to the vegetative cover.

Site disturbance

Like the Oakey Creek site, this site would have been cleared of native vegetation in the 1800s or 1900s, and has been used as grazing land.

Native vegetation

Similar to the Oakey Creek site (Profile 1).

Climate Similar to the Oakey Creek site (Profile 1).

Profile 2: Marrowbone Rd, Pokolbin, NSW

33

0 1 km

New South Wales

Queensland

54

2. Description of soil profile A well drained Shelly Calcarosol, located on an extensively cleared hillslope.

Soil morphology

R/B, D= Red/black, dark; YD= Yellow, dark; CL= clay loam; LC= Light clay; MC= Medium clay

Australian Soil Classification: Shelly Calcarosol (CA EL)

World Reference Base: Calcic Kastanozem (Ruptic) OR Haplic Calcisol (Ruptic)

Soil Taxonomy: Typic Calciudoll OR Typic Calciudept


Depth (m)

Distinctness Shape Moist

MottlesTexturegrade


Segregations

A A 0‐0.10 Clear Even 7.5YR 3/3 Dark brown

‐ CL Strong Polyhedral 10‐20 Carbonate

AB AB 0.10‐0.28 Gradual Even 7.5YR 3/3 Dark brown

~15% R/B, D

LC Strong Sub‐angular

blocky 20‐50 Carbonate

B Bkc 0.28‐0.64 Abrupt Wavy 10YR 6/6

Brownish yellow ~10% Y,

D LC Moderate

Sub‐angular blocky

50‐100 Carbonate

C C 0.64‐1.12 ‐ ‐ 2.5YR 8/2

Pinkish white ‐ MC ‐ ‐ ‐ Carbonate

A

AB

C

B

A

AB

Bkc

C

55

3. Soil mineralogy

X‐ray diffraction patterns of basally oriented clays showed the presence of smectite and

kaolinite throughout the profile. Small amounts of illite are present in the top two horizons.

Smectite content increases with depth and the clay fraction of the C horizon is composed of

predominantly smectite with small amounts of kaolinite. In addition to the phyllosilicates,

the random powder diffraction patterns also showed the presence of calcite in the bottom

two horizons.

X‐ray diffraction patterns of the oriented clay fraction of C horizon after various pre‐treatments;

Mg saturated and air‐dried (‐‐‐‐‐‐), Mg saturated and ethylene glycolated (‐‐‐‐‐‐), K saturated and

air‐dried (‐‐‐‐‐‐) and K saturated and heated at 550°C (‐‐‐‐‐‐).

Thin sections

The left image (PPL) shows the strong microaggregation and organic richness of the A horizon, while

the right image (XPL) of the B horizon shows a spectacular calcitic pedofeature. Here, secondary

calcite appears to have completely coated an ovoid shell fragment.

56


The pH values for this soil profile are strongly alkaline‐very strongly alkaline (8.72‐9.43).

Very low‐low EC values are present throughout the profile.

Organic carbon content is relatively high in the top two horizons of the profile.

There is a significant amount of CaCO3 in the B and C horizons.

The cation exchange capacity (CEC) is high throughout the entire profile.

Available potassium is very high in the A horizon and decreases dramatically in the lower horizons.


Cation exchange properties of soil profile

Horizon pH

(1:5 H2O) EC

(dS/m) Inorganic C (%)

Organic C (%)

Total N (%)

C:N ratio

NO₃‐N (mg/kg)

Colwell P (mg/kg)

PBI‐Colwell

SO4 (mg/kg)

Avail. K (mg/kg)

Cl (mg/kg)

A 8.72 0.12 0.8 4.4 0.4 11.0 14 7 150 7.2 380 10

AB 8.78 0.13 2.6 3.1 0.2 15.5 1 5 ‐ ‐ 140 12

B 8.96 0.13 5.9 1.4 0.06 23.3 1 5 ‐ ‐ 48 17

C 9.43 0.08 7.1 0.1 0.04 2.5 1 5 ‐ ‐ 36 10

Cation exchange properties (mmolc/kg) DTPA extractable (mg/kg) DCB (%) Horizon

CEC Ca Mg K Na Zn Cu Fe Mn Fe Al

A 389 370 9.1 9.7 0.6 3.4 0.36 16 17 2.4 0.2

AB 373 360 8.2 3.7 0.7 ‐ ‐ ‐ ‐ ‐ ‐

B 288 280 6.0 1.2 0.7 ‐ ‐ ‐ ‐ 1.6 0.2

C 310 300 8.0 0.9 1.3 ‐ ‐ ‐ ‐ 1.4 0.2

A A A1

AB AB AB AB

B B B B

C C C

A

CEC (mmolc/kg)

C

57


Clay and silt are present in moderate amounts within this profile. Both fine and coarse sand are present in low amounts.

The bulk density is very low‐low, which not much variation within the profile.

The water content at permanent wilting point is about the same throughout the profile

Penetration resistance increases down the profile (1.3‐2.5 MPa), indicating a medium‐dense degree of soil consolidation.


Particle Size Analysis (%) Moisture ()

Horizon Clay

(<2 µm) Silt

(2‐20 µm) Fine sand (20‐200 µm)


Bulk density (g/cm

3) 10 kPa

1500 kPa (PWP)

0 kPa (FC)


A 46.1 24.4 20.3 9.2 0.88 0.47 0.25 0.56 1.3

AB 38.7 25.8 26.2 9.3 1.25 0.42 0.25 0.49 2.9

B 39.5 30.2 23.2 7.1 1.25 0.43 0.26 0.50 2.5

C 35.2 35.2 24.1 5.5 1.24 0.43 0.25 0.50 2.5


Horizon Silt

(2‐50 µm) Sand (50‐2000 µm)

A 39.9 14.0

AB 44.0 17.3

B 47.9 12.6

C 53.4 11.4

A A A A

ABAB ABAB

C

B B B

C C

B

C

A

AB

B

C

58

Day 2

Scone to Gunnedah

Presenters:

Noel Ticehurst

Manager

E J Holtsbaum Agricultural Research Institute (Nowley Farm), Spring Ridge

59

Nowley Focus Maps

Figure 12: Nowley elevation (100 m resolution)

Figure 13: Nowley slope (10 m resolution)

60

Figure 14: Nowley RGB ternary radiometric image (100 m resolution)

Figure 15: Nowley radiometrics‐ K (%) (100 m resolution)

61

Figure 16: Nowley radiometrics‐ eTh (ppm) (100 m resolution)

Figure 17: Nowley soil classifications

62


Landform This site is situated on the Liverpool Plains. The region consists of alluvial channels and extensive floodplains, with some undulating hills and sloping plains. Profile 3 is located on a sloping plain.


The bioregion comprises mainly of horizontally‐bedded Jurassic and Triassic quartz sandstones and shales with limited areas of conglomerate and basalts. Nowley itself comprises mainly of Quaternary alluvial plains and outwash fans derived from Tertiary basalts.

Drainage class Moderately drained, with a moderate low‐on rate and slow run‐off rate.

Surface condition

Hard surface which is currently stable. The topsoil is moderately erodible, leading to a moderate wind and water erosion hazard when the vegetative cover is poor.

Site disturbance Extensive clearing of native vegetation for agricultural practices has occurred over the last 150 years. Landuses include sheep and cattle grazing, along with dryland cropping of winter cereals and various summer crops.

Native vegetation

Plains grass, windmill grass and blue grass can be found as well as white box (Eucalyptus albens), yellow box (Eucalyptus melliodora), rough‐barked apple (Angophora floribunda) and hill red gums (Eucalyptus camaldulensis).

Climate This area falls into a summer dominant rainfall system, and has an average annual rainfall of 686 mm. The mean maximum temperature in January is 32.2oC, whilst the mean minimum temperature in July is 1.6oC.

Profile 3: Nowley Farm 1, Spring Ridge, NSW

63

0 1 km

Queensland

New South Wales

64

2. Description of soil profile A non‐sodic, red, texture‐contrast soil with a hypercalcic horizon (>20% of soft, finely divided

carbonate) occurring in the transition from lower B to C horizons. These soils are commonly found in

the wheat‐sheep belt of south‐eastern Australia and are valued as a good cropping soil.

Soil morphology

CL= clay loam; LMC= Light medium clay; MC= Medium clay

Australian Soil Classification: Red Chromosol (CH AA)

World Reference Base: Luvic Vertic Calcisol (Ruptic, Clayic, Rhodic)

Soil Taxonomy: Udic Rhodudalf (Fine, Smectitic, Thermic)

Boundary Colour Structure Horizon Depth (m)

Distinctness Shape Moist Dry

Texturegrade


Coarse fragments

A A 0‐0.11 Sharp Even 7.5YR 2.5/3

Very dark brown7.5YR 3/3

Very dark brown CL Weak Polyhedral 10‐20

<10% stones

B21 Bt 0.11‐0.23 Sharp Irregular ‐ 5YR 3/4

Dark Reddish brownLMC Moderate


10‐20<10% stones

B22 Btw 0.23‐0.65 Abrupt Wavy ‐ 2.5YR 3/6 Dark red

LMC Strong Angular blocky 20‐50<10% stones

B23 Btk 0.65‐1.00 ‐ ‐ ‐ 5YR 4/6

Yellowish red MC Moderate Angular blocky 5‐10

<10% stones

A

B₂₁

B₂₃

B₂₂

A

Bt

Btw

Btk

65

3. Soil mineralogy

X‐ray diffraction patterns of the basally oriented clays show the presence of smectite,

kaolinite and illite. Smectite content in the clays increase with the depth and are the highest

in the B23 horizon. Random powder diffraction patterns also identify hematite, quartz, anatase

and traces of goethite in the soil clay fractions of the profile. Calcite is observed only in the

clay fraction of the B23 horizon. Hematite content in the clay fraction is higher in the B21 and

B22 horizons than the amounts in the clay fractions of the A1 and B23 horizons.



saturated and air‐dried (‐‐‐‐‐‐) and K saturated and heated at 550°C (‐‐‐‐‐‐).

Thin sections

The left image (PPL) shows much oriented clay around pore margins, some large quartz grains

embedded in the clayey matrix and a well‐defined pore network in the B22 horizon, while the right

image (PPL) shows some calcitic nodules and infillings in the clayey matrix of the B23 horizon.

66


The pH values for this soil profile increase with depth and range from being slightly acidic to strongly alkaline (6.1‐8.9).

The EC values are low throughout the soil profile.

Organic carbon content is reasonably high in the upper two horizons.

Nitrate content is high in the A horizon.

The CEC is considered to be moderate in the upper 2 horizons and high in the bottom 2 horizons.

Available K is very high in the two top horizons and declines in the subsoil.


Cation exchange properties, available micronutrients and DCB and oxalate Fe and Al of soil profile.

Horizon pH

(1:5 H2O) EC

(dS/m) Inorganic C

(%) Organic C (%)

Total N (%)

C:N rato

NO₃‐N (mg/kg)

Colwell P (mg/kg)

PBI‐Colwell

SO4 (mg/kg)

Avail. K (mg/kg)

Cl (mg/kg)

A 6.1 0.18 ‐ 3.88 ‐ ‐ 42 17 79 19 630 49

B21 7.0 0.12 0.15 3.40 0.12 28.3 7.9 8 ‐ ‐ 410 30

B22 8.7 0.16 0.20 0.82 0.04 20.5 1.1 5 ‐ ‐ 160 10

B23 8.9 0.18 3.43 0.65 0.04 16.2 1.4 5 ‐ ‐ 150 10


CEC Ca Mg K Na Zn Cu Fe Mn Fe Al Al Fe

A 193 110 66 16 0.6 0.5 1.6 41 52 1.75 0.13 0.1 0.2

B21 179 110 58 10 0.7 ‐ ‐ ‐ ‐ 2.32 0.13 0.1 0.2

B22 328 190 130 4 3.8 ‐ ‐ ‐ ‐ 3.00 0.16 0.2 0.2

B23 390 220 160 4 6.5 ‐ ‐ ‐ ‐ 2.03 0.13 0.1 0.1

A1 A1

B21 B21 B21

B22 B22 B22

B23B23 B23

A1

CEC (mmolc/kg)

A1

B21

B22

B23

67

B21


The particle size data show that the moderate‐high clay content increases with depth, sand content shows an opposite trend to clay content, while silt content does not vary much throughout the profile.

Bulk density increases down the profile, and ranges from low to moderate.

Penetration resistance increases down the profile and suggests an extreme degree of soil consolidation in the B21 horizon (11.2 MPa).



Horizon Clay

(<2 µm) Silt

(2‐20 µm) Fine sand (20‐200 µm)


Bulk density (g/cm

3) 10 kPa

1500 kPa (PWP)

0 kPa (FC)


A 33.2 22.5 36.9 7.4 1.04 0.43 0.21 0.53 3.3

B21 46.7 24.4 23.7 5.2 1.16 0.45 0.28 0.52 8.9

B22 49.2 23.5 23.2 4.1 1.58 0.37 0.29 0.40 11.2

B23 63.5 12.1 19.8 4.6 1.6 0.35 0.28 0.38 ‐


Horizon Silt

(2‐50 µm) Sand (50‐2000 µm)

A 41.8 25.0

B21 39.7 13.6

B22 37.8 13.0

B23 18.4 18.0

A A A A

B21B21 B21

B23

B22 B22 B22

B23

B23 B23

B22

A1

B21

B22

B21

68


Landform Similar to that of Profile 3, but located further downslope on the sloping plain.


Similar regional parent materials to those of Profile 3. Profile 4 is derived from Quaternary alluvium sourced from Jurassic sandstones.

Drainage class Rapidly draining topsoil and slowly draining subsoil. Slow run‐on and run‐off rate.

Surface condition

Sandy and loose. Erodibility and erosion hazard are relatively low due to the coarse sandy texture of the topsoil and the small slope of the land.

Site disturbance Similar to Profile 3, although this site has generally been used for grazing rather than cropping.

Native vegetation

Similar to that of Profile 3.

Climate Similar to that of Profile 3.

Profile 4: Nowley Farm 2, Spring Ridge, NSW

69

0 1 km

Queensland

New South Wales

70

2. Description of soil profile A strongly duplex profile with a sodic upper B horizon. This soil has been used for improved

pasture production and dryland cropping.

Soil morphology

S= sand; LC= Light clay; MC= Medium clay

Australian Soil Classification: Eutrophic, Mottled‐Mesonatric, Brown Sodosol

World Reference Base: Stagnic Solonetz (Abruptic, Ruptic, Magnesic, Humic, Epiarenic, Clayey)

Soil Taxonomy: Aquic‐Arenic Natrustalf (Very Fine, Kaolinitic, Thermic)



Mottles Texture grade


A1 A 0‐0.15 Clear Even 10YR3/4

Dark yellowish brown ‐ S

Single grained

‐ ‐

A2 E 0.15‐0.46 Clear Wavy 10YR 6/4

Light yellowish brown ‐ S

Single grained

‐ ‐

B21 Btqn 0.46‐0.52 Clear Wavy 2.5YR 7/2 Pale red

‐ LC Massive ‐ ‐

B22 Btn1 0.52‐0.6 Diffuse Wavy 7.5YR 5/8

Strong brown ~15% grey MC Strong Columnar 50‐150

B23 Btn2 0.6‐1.02 ‐ ‐ 7.5YR 5/6

Strong brown ~15% grey MC Strong Columnar 50‐150

A1

B21

B23

B22

A2

A

E

Btqn

Btn1

Btn2

71

3. Soil mineralogy

X‐ray diffraction patterns of basally oriented clays show the presence of kaolinite, illite and

traces of an interstratified mineral. Illite content in the clay fraction increases slightly with

the depth in the profile. In addition to the phyllosilicates, the random powder diffraction

patterns also identify quartz (increases with depth), anatase and goethite in the soil clay

fractions.




mineral.

Thin section

The left image (PPL) shows a very thin veneer of organic matter and/or iron oxides around most of

the quartz grains in the A2 horizon, with just an occasional bridge of clay between grains. The right

image (PPL) shows prodigious argillans in the B23 horizon, with some notable organic staining in some

of these.

I/S

72


The pH values for this soil profile are moderately acidic and do not change much with profile depth.

The profile yields very low EC values, indicating negligible soluble salts throughout.

Organic carbon and nitrogen contents are very high in the top horizon and then low‐very low for the underlying horizons.

The cation exchange capacity (CEC) increases markedly from the A horizons to the B horizons, and ranges from very low to moderate.


Cation exchange properties, available micronutrients and DCB Fe and Al of soil profile

Horizon pH

(1:5 H2O) EC

(dS/m) Organic C

(%) Total N (%)

C:N ratio

NO₃‐N (mg/kg)

Colwell P (mg/kg)

PBI‐Colwell

SO4 (mg/kg)

Avail. K (mg/kg)

Cl (mg/kg)

A1 5.80 0.05 4.46 0.36 12.4 15 14 24 3.4 76 10

A2 5.71 0.01 0.69 0.06 11.5 2.2 5 ‐ ‐ 18 10

B21 5.65 0.07 0.64 0.06 10.7 1 5 ‐ ‐ 66 17

B22 5.70 0.08 0.42 0.05 8.4 1 5 ‐ ‐ 77 12

B23 5.86 0.10 0.15 0.03 5.0 1 5 75 66


CEC Ca Mg K Na Al Zn Cu Fe Mn Fe Al

A1 34 16 4 11 0.7 1 0.51 0.14 120 8.1 0.47 0.05

A2 21 16 3 3 0.4 1 ‐ ‐ ‐ ‐ 0.25 0.02

B21 114 26 78 11 18 1 ‐ ‐ ‐ ‐ 2.68 0.26

B22 130 24 91 13 22 1 ‐ ‐ ‐ ‐ 3.41 0.38

B23 119 12 82 13 24 1 ‐ ‐ ‐ ‐ 2.59 0.37

A1 A1 A1

A2 A2 A2 A2

B21 B21 B21 B21

B22 B22 B22 B22

B23 B23 B23 B23

A1

CEC (mmolc/kg)

73


Sand content decreases down the profile, ranging from very high to low, whilst clay content shows an opposite trend, ranging from very low to very high.

Moderate to high bulk densities are observed throughout the entire profile. Penetration resistance increases down the profile, suggesting a dense to extremely dense

degree of soil consolidation.



Horizon Clay

(<2 µm) Silt

(2‐20 µm) Fine sand (20‐200 µm)


Bulk density (g/cm

3) 10 kPa

1500 kPa (PWP)

0 kPa (FC)


A1 7.6 7.6 65 19.8 1.53 0.35 0.21 0.06 1.7

A2 9.2 3.1 65 22.7 1.61 0.32 0.18 0.06 3.0

B21 59.4 3.1 26.8 10.7 1.47 0.43 0.39 0.29 5.5

B22 71.2 3.1 17.7 8.0 1.82 0.29 0.27 0.21 7.5

B23 61.3 3.2 22.7 12.8 1.73 0.33 0.30 0.23 ‐


Horizon Silt

(2‐50 µm) Sand (50‐2000 µm)

A1 18.7 73.7

A2 9.4 81.4

B21 6.3 34.3

B22 2.0 26.8

B23 5.9 32.8

A1 A1 A1 A1

A2 A2 A2 A2

B22

B21 B21 B21

B22 B22 B22

B21

B23 B23 B23 B23

A1

A2

B21

B22

74

Day 3 Gunnedah to Narrabri

Presenters:

Mr Bill Wall

Farm Manager, I.A. Watson Grain Research Centre


75

Digital Soil Class mapping in the Namoi Catchment

Michael Nelson, & Inakwu Odeh, The University of Sydney

In Australia, a move towards catchment‐based management, under the auspices of various

Catchment Management Authorities (CMAs), has led to increased demand for catchment‐

scale information. To meet this demand, some CMAs have initiated projects to integrate

disparate soil data into soil spatial information systems, or, more broadly, land resource

information systems useful for natural resource management.

We collated soils data for the Namoi catchment from various sources and used the soil

profile information to create catcment‐scale digital soil class maps of the Namoi catchment

(Nelson & Odeh, 2009).

The Namoi Catchment is an area of ~42 000 km2, in north‐western NSW. The geology of the eastern section of the catchment is dominated by Tertiary volcanics, with basalt rocks forming the south, south‐western, and north‐eastern boundaries (Donaldson and Heath 1997). The central section of the catchment is dominated by sedimentary geology, including shales, sandstones, and conglomerate rocks, with the alluvial plains consisting of Quaternary sedments (Zhang et al. 1999). A large alluvial plain stretching from Narrabri west to Walgett is dominated by Quaternary sediments (Zhang et al. 1999). The soils on the alluvial plains, especially where sediment is predominately sourced from the basaltic ranges, are generally moderately fertile, deep cracking clays (Donaldson and Heath 1997; Young et al. 2002) or Vertosol (Isbell 1996). In some places, these Vertosols are found in association with duplex soils termed as Chromosols, Sodosols, and Kurosols, and Dermosols and Ferrosols (Isbell 1996; Donaldson and Heath 1997). In the eastern part, which is characterised by rough or steep terrain, the soil associations are predominantly made up of duplex soils as well as Kandosols, Tenosols, and Dermosols (Isbell 1996; Donaldson and Heath 1997) Soils formed on Pilliga sandstone, which are located in the southern central section of the catchment, are coarse‐textured Kandosols, Tenosols, and some Sodosols (Donaldson and Heath 1997) Below are maps created for the Namoi catchment using Classification Trees (Figure 18) .

76

Figure 18: Digital soil class map of the Namoi catchment developed using a classification tree algorithm

Enlarged sections of the whole catchment maps around Nowley (Figure 19) and the I. A. Watson

Research Station (Figure 20) are shown below.

Figure 19: Section of the Namoi Catchment soil class map for the area around Nowley

Figure 20: Section of Namoi catchment soil class map for the area surrounding the IA Watson research station

Data mining algorithms such as Classification trees are useful in producing maps of soil

classes, but do not quantify the uncertainty surrounding any predictions. Model—based

77

approaches provide an alternative whereby predictions and prediction error variances can

be quantified.

Digital soil mapping using generalized linear spatial models

Michael Nelson, Inakwu Odeh, Thomas Bishop & Neville Weber


Our research examines the use of model—based geostatistics (Diggle & Ribiero, 2007) to

produce digital soil class maps. We have developed a generalized linear spatial model for

digital soil class mapping (Nelson et al 2009) and are now considering the quantifying the

various sources of error and effects on the error in the final map.

Below is a simple example using binomial data, a digital soil map predicting the presence or

absence of Vertosols for a section of the Upper Namoi catchment. A map of the study area

is presented in Figure 21, with the predicted probability in Figure 22 and prediction error

variance in Figure 23. The use of the generalized linear spatial model avoids the problems

associated with indicator kriging (Papritz, 2009) , providing a theoretically sound approach

for mapping Bernoulli data.

Figure 21: Location of the Upper Namoi study area and soil survey locations

78

Figure 22: Predicted probability of Vertosol occurrence for the Upper Namoi using a generalized linear spatial model for binomial data

Figure 23: Prediction error variance for predicted probability of Vertosol occurrence for the Upper Namoi

References

Diggle PJ, Ribiero Jr PJ (2007) Model—based geostatistics. Springer Series in Statistics, New York.

Donaldson S, Heath T (1997) Namoi river catchment report on land degradation and Proposals for

integrated management for its treatment and prevention' NSW Department of Land and Water

Conservation.

Nelson, MA, Odeh IOA (2009) Digital soil class mapping using legacy soil profile data: a comparison of a genetic algorithm and classification tree approach. Australian Journal of Soil Research, 47, 1—18.

79

Nelson MA, Bishop TFA, Odeh IOA, Weber, N (2009) A generalized linear spatial model for digital soil

class mapping [Digital soil class mapping using model‐based geostatistics] in Proceedings of

Pedometrics 2009 conference, Beijing.

Papritz, A (2009) Why indicator kriging should be abandoned. Pedometron 26

Zhang L, Beavis SG, Gray SD (1999) Development of a spatial database for large‐scale catchment

management: geology, soils and landuse in the Namo Basin, Australia. Environment International 25,

853‐860.

80

High resolution soil carbon mapping

Budiman Minasny, The University of Sydney

A new methodology was developed and applied to make an assessment of the distribution

of total, organic and inorganic carbon at a grains research and grazing property compared

with an adjacent permanent pasture stock‐route, in the IA Watson farm. The I.A. Watson

Grains Research Institute (30°16´12.35˝S, 149°48´13.14˝E) is a 460 hectare (320 ha of

cropping and 120 ha of pastoral land) property in Narrabri, north‐west New South Wales.

The property has been breeding cereals (wheat, rye and triticale) under traditionally

managed irrigated cropping operations for half a century. Repeated cultivation of the soil

with limited SOM inputs has caused a decline of carbon levels. An adjacent strip of crown

land used as a travelling stock route was incorporated into the survey area, to allow for

comparisons of soil carbon content between these two different land use regimes. There

was also variation in the soil types between Vertosols and Dermosols of the cropping area

compared with the Calcarosols of the pasture area

A baseline survey was carried out to identify map areas of soil variation across the farm with

data from a Multi‐ Sensor Platform (M‐SP). The M‐SP consisted of 3 proximal soil sensors

including a Geonics Electromagnetic Induction (EM) 38 and EM 31 ECa sensors (Geonics Ltd,

Mississauga, Ontario, Canada) and a GR320 Gamma radiometric spectrometer (Exploranium

Radiation Detection Systems, Acworth, Georgia, USA). The vehicle was driven across the field

at a speed of approximately 10km/h and the sensor measurements were logged at a rate of

1 Hz and georeferenced with an OmniSTAR HP, single frequency, Differential Global

Positioning System (D‐GPS) (OmniSTAR Inc, Houston, Texas, USA) which simultaneously

acquired elevation data. The swath width across the field ranged in distance from 20‐30

metres. All geo‐referenced continuous data layers were interpolated with Vesper software

using block kriging onto a standard 5m grid for analysis.

81

Figure 24: Electromagnetic induction (EM) 38

ECa data interpolated onto a 5 metre grid

Figure 25: Electromagnetic induction (EM) 31 ECa

data interpolated onto a 5 metre grid

82

Figure 26: Gamma spectrometer data inPotassium (K) region of interest

Figure 27: Gamma spectrometer data in Thorium (Th) region of interest

83

Figure 28: Digital elevation model in metres above sea level (ASL)

Coupled with a digital elevation model and secondary terrain attributes all of the data layers

were combined by k‐means clustering to develop a stratified random soil sampling scheme

for the survey area. Soil samples were scanned at 15cm increments to a depth of 1m with a

mid‐infrared (MIR) diffuse reflectance spectrometer, which was calibrated using a

proportion of the samples that were analysed in a laboratory for total carbon and inorganic

carbon content.

The values from the observed soil profiles were then interpolated throughout the farm at a

resolution of 5 m x 5 m grid using regression model based on the covariate/ ancillary

information derived from the soil survey. A regression rule program CUBIST was used to

derive models that could estimate carbon across the entire property and stock‐route.

The combination of new methodologies and technologies have the potential to provide large

volumes of reliable, fine resolution and timely data required to make baseline assessments,

mapping, monitoring and verification possible.

84

References

Miklos, M., Short, M.G., McBratney, A.B., Minasny, B., 2010. Mapping and comparing the distribution

of soil carbon under cropping and grazing management practices in Narrabri, NW NSW. Australian

Journal of Soil Research 48, 248–257.

Table 5: Mean soil total, organic and inorganic carbon stock, based on landuse

Land use No. of

Samples

Total Carbon

(kg/m2)

Organic Carbon

(kg/m2)

Inorganic Carbon

(kg/m2)

Cropping 30 12.41 5.04 7.37

Pasture 18 16.25 6.79 9.46

Stock‐route 11 13.89 8.21 5.68

Figure 29: Organic carbon stock to one metre Figure 30. Inorganic carbon stock to one metre

85

EDGEROI FOCUS MAPS

Figure 31: The Edgeroi study area

86

Figure 32: The Edgeroi Data set (McGarry et al. 1989) point locations (yellow triangles)

87

Figure 33: Maps of organic carbon and available water capacity to 1m in the Edgeroi area.

88


Landform

Pilliga Scrub is part of the Pilliga Nature Reserve, which covers a total area of 80,000 ha. It consists of low, undulating, sandy country with occasional outcrops of rocky sandstone and low cliffs. Landforms in the southern area tend to be more steep and rugged with the presence of small gorges.


The bedrock of the area consists of the Jurassic‐aged Pilliga Sandstone, underlain by silty sandstones, claystones and shales. The Pilliga Sandstone dips in a north‐west direction with an angle of 5‐10° when not disrupted by igneous intrusions. In the north, extensive sediments were deposited by dendritic streams

Drainage class Irregular drainage, with a moderate low‐on rate and a very slow run‐off rate.

Surface condition

Loose and sandy. The soil erodibility is low, as is the erosion hazard.

Site disturbance Very low site disturbance as it is classed as a nature reserve, although there is a main road situated about 50 m away from the profile. Land surrounding the reserve is used for timber production.

Native vegetation

The dominant canopy species of vegetation are Eucalyptus spp and Callitris endlicheri. The shrub and groundcover includes species such as Acacia spp, Allocasuarina spp, Brachycome spp, Styphelia triflora and Swainsona spp.

Climate The area has a warm, sub‐humid climate, with an annual average rainfall of approximately 625 mm. The mean maximum temperature in January is 33.5oC, whilst the mean minimum temperature in July is 2.2oC.

Profile 5: Pilliga Scrub, Pilliga, NSW

89

Queensland

New South Wales

0 1 km

90

2. Description of soil profile This is an apedal sandy soil, with an extremely low CEC throughout the entire profile. Krotovinas are

present in the upper B horizon.

Soil morphology

LS= Loamy sand; CS= Clayey sand

Australian Soil Classification: Orthic Tenosol (TE DS)

World Reference Base: Cutanic Lixisol (Humic, Chromic)

Soil Taxonomy: Kanhaplic Haplustalf (Coarse Loamic, Siliceous, Thermic)

Boundary Colour Structure

Horizon Depth (m)


Texture grade

Grade

A A 0‐0.15 Gradual Even 7.5YR 3/2 Dark brown

7.5YR 5/3 Brown

LS Apedal

B1 Bw1 0.15‐0.45 Diffuse Even 5YR 4/6

Yellowish red 5YR 5/3

Reddish brown LS Apedal

B21 Bw2 0.45‐0.75 Diffuse Even 5YR 5/8

Yellowish red 7.5YR 6/6

Reddish yellow CS Apedal

B22 Bw3 0.75‐1.00 ‐ ‐ 7.5YR 6/8

Reddish yellow 7.5YR 6/8

Reddish yellow CS Apedal

B₁

B₂2

B₂1

A A

Bw1 or Bt?

Bw2

Bw3

91

3. Soil mineralogy

X‐ray diffraction patterns of basally oriented clays show the presence of kaolinite and

interstratified vermiculite. In addition to the phyllosilicates, the random powder diffraction

patterns identify quartz, anatase, goethite and hematite in the soil clay fractions.




Thin sections

The left image (PPL) shows a veneer of organic‐stained iron oxides and clay coating most of the large

quartz grains in the B1 horizon, while the right image (PPL) shows the very limited extent of clay

coating grains in the B22 horizon.

92


The pH values for this soil profile range from strongly acidic to slightly acidic, and pH values increase with depth.

Very low EC values are apparent in each of the horizons within the soil profile.

High N in the top horizon followed by very low N in the lower horizons.

Very high organic carbon content in the top horizon and then low to very low for the underlying horizons.

The cation exchange capacity (CEC) is very low throughout the entire profile.



Horizon pH

(1:5 H2O) EC


Total N (%)

C:N ratio

NO₃‐N (mg/kg)

Colwell P (mg/kg)

PBI‐Colwell

SO4 (mg/kg)

Avail. K (mg/kg)

Cl (mg/kg)

A 5.31 0.06 7.63 0.35 21.8 22 12 98 2 120 18

B1 6.05 0.01 0.85 0.05 17.0 1 5 ‐ ‐ 69 10

B21 6.08 0.01 0.69 0.04 17.3 1 5 ‐ ‐ 63 10

B22 6.23 0.01 0.49 0.04 12.3 1 5 ‐ ‐ 57 10



A 33.8 10 12 2.9 0.2 8.7 0.28 0.13 190 26 0.63 0.14

B1 18.6 1 13 1.8 0.2 2.6 ‐ ‐ ‐ ‐ 0.67 0.10

B21 16.9 1 12 1.6 0.2 2.1 ‐ ‐ ‐ ‐ 0.60 0.09

B22 18.2 1 12 1.5 0.3 3.4 ‐ ‐ ‐ ‐ 0.86 0.12

A A A

B1 B1 B1 B1

B21 B21 B21 B21

B22 B22 B22 B22

A

CEC (mmolc/kg)

93


Very high sand content throughout the entire profile ranging from 68‐71%.

Low to moderate bulk density for all horizons in the profile.

The water content at permanent wilting point is low and does not vary much within the profile.

Hydraulic conductivity increases down the profile.

The penetration resistance ranges from medium to dense. Soil physical characteristics


Horizon Clay

(<2 µm) Silt

(2‐20 µm) Fine sand (20‐200 µm)


Bulk density (g/cm

3) 10 kPa

1500 kPa (PWP)

0 kPa (FC)


A 10.8 7.5 10.4 71.3 1.46 0.23 0.07 0.38 0.9

B1 14.3 5.1 12.3 68.3 1.46 0.23 0.08 0.37 1.6

B21 13.2 5.1 11.8 70.0 1.28 0.24 0.09 0.43 1.2

B22 13.5 5.2 11.7 69.6 1.39 0.23 0.08 0.40 ‐


Horizon Silt

(2‐50 µm) Sand (50‐2000 µm)

A 19.0 70.2

B1 14.4 71.2

B21 14.2 72.6

B22 14.5 72.0

A A A A

B1 B1 B1 B1

B22

B21 B21 B21

B22 B22 B22

B21

A1

B1

B21

94


Landform This site is located on an alluvial fan of the Namoi River.


Basaltic alluvium. The basalt shield volcano to the east has been extensively eroded, leaving its highest peak, Mt Kaputar, at 1508 m. The basalt flows overlie Tertiary alluvial sandstone and conglomerate. Calcareous clays and marls of the Rolling Downs Group form gentle slopes on the properties such as IA Watson.

Drainage class Slow drainage, with a low run‐on and run‐off rate.

Surface condition

Epipedal and cracked when dry. The soil has a low erodibility and is regarded as being a low erosion hazard. There is no salinity evident on the surface.

Site disturbance The surround region land has been extensively cleared for agricultural production including the growth of cotton, wheat, barley and oilseeds. Livestock production includes cattle and pigs.

Native vegetation

Native vegetation is sparse on the floodplain, but where it occurs it consists of open grasslands (mainly Austrostipa aristiglumis and Dichanthium sericeum) with scattered trees (e.g. Eucalyptus spp. and Angophora floribunda) and shrubs (e.g. Acacia pendula and Rumex spp.)

Climate The area has a warm, sub‐humid climate, with an annual average rainfall of 643 mm. The mean maximum temperature in January is 35.3oC, whilst the mean minimum temperature in July is 3.4oC.

Profile 6: I.A. Watson Research Institute, Narrabri, NSW

95

0 1 km

Queensland

New South Wales

96

2. Description of soil profile A grey Vertosol used for dryland wheat production and/or irrigated cotton and wheat production. Mechanical compaction has degraded the subsurface structure of this profile.

Soil morphology

GPD= Grey, pale, distinct; LC= Light clay; LMC= Light medium clay; MC= Medium clay

Australian Soil Classification: Grey Vertosol

World Reference Base: Calcic‐Mollic Vertisol (Pallic) OR Calcic Vertisol

Soil Taxonomy: Sodic Calciustert



MottlesTexture grade


Coarse fragments

Ap1 Ap1 0‐0.08 Clear Even 7.5YR 3/2 Dark brown

‐ ‐ LC Weak ‐ ‐ ‐

Ap2 Ap2 0.08‐0.30 Clear Even 5YR 4/1 Dark grey

10YR 4/2 Dark greyish

brown ‐ LC Massive ‐ ‐ ‐

B1 Bw 0.30‐0.45 Gradual Wavy 5YR 2.5/1 Black

7.5YR 4/1 ‐ LMC Moderate Angular‐blocky

50‐100 ‐

B21 Bssk1 0.45‐0.90 Diffuse Even 10YR 4/2

Dark greyish brown

10YR 5/2 Greyish brown

‐ LMC Strong Lenticular 50‐100<10 % stones

B22 Bssk2 0.90‐1.65 ‐ ‐ 10YR 5/2

Greyish brown10YR 5/2

Greyish brown~30% G, P, D

MC Strong Angular‐ blocky

50‐100

A1

B1

B22

B21

A₂

Ap1

Ap2

Bw

Bssk1

Bssk2

97

3. Soil mineralogy

X‐ray diffraction patterns of basally oriented clays show the presence of smectite, kaolinite

and minor amounts of illite. Smectite content is very high in B21 and B22 horizons. Quartz,

anatase and feldspar (microcline) are also identified in the random powder diffraction

patterns of the soil clay fractions.




98


The pH values for this soil profile range from slightly acidic in the topsoil to very strongly alkaline in the subsoil (6.48‐9.53).

Very low EC values are found in the A horizons and upper B horizon, while medium EC values are found in the lower B horizons.

The organic carbon levels are considered to be moderate in the surface horizon and vary from low‐very low in the underlying horizons.

The cation exchange capacity (CEC) is low to moderate for the profile.

Exchangeable sodium percentage (up to 20%) is very high in the subsoil.



Horizon pH

(1:5 H2O) EC


Total N (%)

C:N ratio

NO₃‐N (mg/kg)

Colwell P (mg/kg)

PBI‐Colwell

SO4 (mg/kg)

Avail. K (mg/kg)

Cl (mg/kg)

Ap1 6.82 0.04 1.33 0.12 11.1 1.1 33 53 5 240 10

Ap2 6.48 0.04 0.95 0.07 13.6 5.9 8 ‐ ‐ 52 10

B1 7.21 0.04 0.92 0.06 15.3 4.5 5 ‐ ‐ 55 16

B21 9.11 0.17 0.50 0.03 16.7 3.1 5 ‐ ‐ 84 10

B22 9.53 0.29 0.27 0.02 13.5 6.1 5 85 19

Cation exchange properties mmolc/kg DTPA extractable (mg/kg) DCB (%) Horizon


Ap1 82 41 33 6.2 1.7 0.94 1.5 56 170 0.25 0.05

Ap2 71 39 27 1.3 2.5 ‐ ‐ ‐ ‐ 0.35 0.07

B1 91 49 35 1.4 5.7 ‐ ‐ ‐ ‐ 0.32 0.06

B21 251 160 74 2.1 15 ‐ ‐ ‐ ‐ 0.28 0.06

B22 185 70 76 2.2 37 ‐ ‐ ‐ ‐ 0.31 0.06

Ap1 Ap1 Ap1

Ap2 A p2 A p2 A p2

B1 B1 B1 B1

B21 B21 B21

B22 B22 B22

Ap1

CEC concentration (mmolc/kg)

B21

B22

99


High to very high clay contents are found in this profile, with the B22 horizon having the highest clay content.

The profile has a moderate to high bulk density throughout. The penetration resistance ranges from 0.9 to 2.9 MPa, indicating a medium to very dense degree

of consolidation.


s


Horizon Clay

(<2 µm) Silt

(2‐20 µm) Fine sand (20‐200 µm)


Bulk density (g/cm

3) 10 kPa

1500 kPa (PWP)

0 kPa (FC)


Ap1 41.9 23.7 28.5 5.9 1.64 0.35 0.26 0.38 0.9

Ap2 46.4 22.1 27.8 3.7 1.59 0.37 0.28 0.40 1.9

B1 44.7 19.6 31.2 4.5 1.65 0.35 0.26 0.38 1.7

B21 42.3 24.6 26.2 6.9 1.73 0.32 0.25 0.35 2.9

B22 67.6 16.1 15.1 1.2 ‐ ‐ ‐ ‐ ‐

International system PSA (%)

Horizon Silt

(2‐50 µm) Sand (50‐2000 µm)

Ap1 40.7 17.4

Ap2 37.3 16.2

B1 35.0 20.2

B21 41.5 16.2

B22 21.3 11.0

Ap1 Ap1

Ap1 Ap1

Ap2 Ap2 Ap2 Ap2

B21

B1 B1 B1

B21 B21 B21

B1

B22

Ap1

Ap2

B1

B21

100


Landform It is located in a low energy environment as a result of the site being positioned on a flat, upper alluvial floodplain.


The profile overlies a basalt shield volcano which has eroded leaving its highest peak at Mt Kaputar at 1508 m. This shield overlies tertiary alluvial sandstone and conglomerate. At the site mudstone and basalt are recognised as the dominate parent material.

Drainage class Slow drainage, with a low‐on rate and a ponded run‐off rate.

Surface condition

Firm surface which is very stable. There is low soil erodibility around the site, which is also regarded as having a low erosion hazard. There is no salinity evident on the surface.

Site disturbance Similar to that of Profile 6.

Native vegetation

Similar to that of Profile 6.

Climate Similar to that of Profile 6.

Profile 7: Cooyong, Narrabri, NSW

102

2. Description of soil profile A polygenetic profile with a strongly structured Red Chromosol overlying a calcic Brown Vertosol. A stone line separates the two profiles.

Soil morphology

GPD= Grey, pale, distinct; LC= Light clay; LMC= Light medium clay; MC= Medium clay

Australian Soil Classification: Red Chromosol over a Brown Vertosol

World Reference Base: Calcic Stagnic Vertisol (Chromic, Mollinovic)

Soil Taxonomy: Vertic Calciudoll OR Oxyaquic Vertic Hapludalf (Fine Siltic, Mixed, Superactive, Thermic)



Mottles Texture grade


Coarse fragments

1A 1A 0‐0.26 Gradual Irregular 2.5YR 2.5/2

Very dusky red ‐ CL Moderate Polyhedral 10‐20 ‐

1B1 1Bt 0.26‐0.60 Clear Wavy 2.5YR 3/6 Dark red

~25 % G,P,D

LMC Strong Lenticular 50‐100 ‐

2B21 2Btk1 0.60‐0.91 Gradual Even 5YR 3/3

Dark reddish brown ‐ MC Strong

Angular‐blocky

20‐50 ‐

2B22 2Btk2 0.91‐1.40 ‐ ‐ 7.5YR 4/6

Strong brown ‐ LMC Strong Lenticular 50‐100

<10 % stones

1A

1B₂

2B22

2B21

1A

1Bt

2Btk1

2Btk2

103

3. Soil mineralogy

X‐ray diffraction patterns of basally oriented clays show the presence of smectite, kaolinite

and traces of illite. In addition to the phyllosilicates, the random powder diffraction patterns

identify quartz and small amounts of feldspar in the soil clay fractions.

X‐ray diffraction patterns of the oriented clay fraction of 1B2 horizon soil after various pre‐



Thin sections

The thin section image on the left (PPL) shows the well‐developed porosity and aggregation of the

1B2 horizon, while the right image (XPL) shows a high degree of clay orientation around large sand

grains and pore margins in the same horizon.

104


The pH values for this soil profile range from slightly acidic to strongly alkaline, increasing down the profile.

EC values ranged from medium to extreme and increased down the profile.

The organic carbon and total nitrogen levels were low and declined down the profile.

The cation exchange capacity (CEC) is moderate to high throughout the profile.



Horizon pH

(1:5 H2O) EC


Total N (%)

C:N ratio

NO₃‐N (mg/kg)

Colwell P (mg/kg)

PBI‐Colwell

SO4 (mg/kg)

Avail. K (mg/kg)

Cl (mg/kg)

1A 6.86 0.62 1.85 0.13 14.2 4.4 5 36 3.4 160 10

1B1 8.00 0.48 0.83 0.06 13.8 1 5 ‐ ‐ 85 10

2B21 8.84 1.34 0.50 0.04 12.5 1 5 ‐ ‐ 70 13

2B22 9.13 2.55 0.51 0.03 17 1 5 ‐ ‐ 94 28



1A 137 49 63 17 8 0.73 0.58 22 22 0.39 0.05

1B1 220 118 79 13 10 ‐ ‐ ‐ ‐ 0.78 0.10

2B21 217 98 92 13 14 ‐ ‐ ‐ ‐ 0.67 0.08

2B22 232 102 96 13 21 ‐ ‐ ‐ ‐ 0.53 0.06

1A1 1A1 1A1

1B1 1B1 1B1 1B1

2B21 2B21 2B21 2B21

2B22 2B22 2B22 2B22

1A1

CEC (mmolc/kg)

105


This profile has a high clay content throughout.

The bulk density is considered to be moderate in the top horizon, increasing to be high in the lower horizons.

The water content at permanent wilting point increases down the profile.

Penetration resistance increases down the profile causing the soil to have a dense to extremely dense degree of soil consolidation.


s


Horizon Clay

(<2 µm) Silt

(2‐20 µm) Fine sand (20‐200 µm)


Bulk density (g/cm

3) 10 kPa

1500 kPa (PWP)

0 kPa (FC)


1A 14 10 65 11 1.51 0.25 0.09 0.37 1.5

1B1 35 7 52 5 1.68 0.30 0.21 0.35 2.9

2B21 32 11 49 8 1.75 0.29 0.20 0.33 4.9

2B22 38 13 48 1 1.80 0.29 0.22 0.32 ‐


Horizon Silt

(2‐50 µm) Sand (50‐2000 µm)

1A1 40.7 17.4

1B1 37.3 16.2

2B21 35.0 20.2

2B22 41.5 16.2

1A1 1A1 1A1 1A1

1B1 1B1 1B1 1B1

2B22

2B21 2B21 2B21

2B22 2B22 2B22

2B21

1A1

1B1

2B21

106

Day 4

Narrabri to Goondiwindi

Presenters:

Dr. Brett Whelan

Senior Research Fellow

Faculty of Agriculture, Food and Natural Resources



Broughton Boydell

“Remaka”

James Duddy

“South Callandoon”

107

Australian Production Systems Research Unit (APSRU)

See maps for location of the APSRU reference sites

Summary

In 1990, the Queensland State Government and CSIRO established the joint research team,

the Agricultural Production Systems Research Unit (APSRU), based in Toowoomba,

Queensland, Australia. The formation of APSRU brought together expertise in the computer

simulation of farming systems and was intended to facilitate research that would impact on

how agricultural production systems are managed. After two successive five‐year terms and

a successful external review in 2000, another five‐year term was agreed by the participating

organizations – CSIRO Divisions of Sustainable Ecosystems and Land & Water, the

Queensland Departments of Primary Industries and Fisheries and Natural Resources, Mines

& Energy and The University of Queensland. APSRU has created a centre of excellence in the

field of agricultural production systems research with the capability of pursuing related

world class research and training.

Mission

To benefit rural industries and the environment through innovative systems approaches to

research and development.

Core functions

Facilitate research collaborations. Co‐develop and manage research tools, methods and

resources.

Influence systems research design.

Examples of impacts

Operationalised use of seasonal climate forecasting for crop management

Assisted farmers and agribusiness to better understand and measure their soil resource

Decision tools and processes used by agricultural consultants in advising farm clients

Use by plant breeding companies of gene to phenotype modelling

Quantified drainage & salinity risk in the Murray‐Darling Basin

Provided policy relevant information for drought exceptional circumstances assessment

Scientific publications cited extensively

Scientists invited as keynote speakers at national and international symposia

Further information and links

http://www.asris.csiro.au/themes/model.html#Model_Sites

108

Figure 52: Locations of APSRU reference sites across Australian continent

Figure 53: APSRU reference site plant available water data (WA wheatbelt)

109

Figure 54: APSRU reference site plant available water data (SE Australia)

Figure 55: APSRU reference site plant available water data (Liverpool Plains)

110

Figure 53: APSRU reference sites within the Liverpool plains area with reference to tour profile locations.

111


Landform Romaka is situated in the Gwydir River valley, which is located in the Murray Darling Basin. It lies between the Masterman Range to the north, and the Nandewar Ranges to the south. The site is located on a slight rise in a broad floodplain.


The parent material at the profile site is likely to be quartz sandstone and alluvium from Jurassic and Carboniferous sediments in the surrounding ranges. The field also includes soil derived from Tertiary basaltic alluvium.

Drainage class Moderate drainage and low run on and run off rate due to the flat terrain.

Surface condition:

The profile has a weakly pedal and friable topsoil. Due to the flatness of the surrounding terrain and lack of frequent flood events, the site has a low erosion hazard.

Site disturbance

The site has been under cultivation for an extended period of time. Cereal and sorghum crops have been the most recent crops used in rotation on the property. Sorghum roots can still be seen in the profile.

Native vegetation

Closed grasslands with scattered woodlands dominate. Main tree species are Eucalyptus albens (white box), Eucalyptus melliodora (yellow box), Acacia Pendula (myall), Heterodendron oleifolium (rosewood) and Casurina cristata (belah). The main grass species are Stipa aristiglumis (plains grass) with many Aristida spp.(wire grass), Stipa spp. (spear grass) and Danthonia spp. (wallaby grasses).

Climate Nearby Moree is situated in a semi‐arid climate with hot summers and frosty winters. Annual rainfall is approximately 580 mm. Average maximum temperature is 27.6°C and average minimum temperature is 11.7°C.

Profile 8: Romaka, Terry Hie Hie, NSW

112

0 1 km

Queensland

New South Wales

113

2. Description of soil profile A red, clayey soil formed on very old alluvium. This reddish soil occurs on slightly elevated

areas of land, whilst the surrounding soils consist mainly of greyish Vertosols.

Soil morphology

RDD= Red, dark, distinct; SCL= Sandy clay loam; LMC= Light medium clay; MC= Medium clay

Australian Soil Classification: Red Dermosol (DE AA)

World Reference Base: Calcic Cutanic Luvisol (Endo‐clayic, Chromic)

Soil Taxonomy: Calcic Haplustalf (Fine, Mixed, Superactive, Thermic) OR Typic Paleustalf


Horizon Depth (m)


MottlesTexturegrade


Coarse fragments

Segregations

Ap1 Ap1 0‐0.03 Abrupt Even 10YR 3/3

Dark brown

2.5Y 3/1Dark

reddish gray

‐ SCL

Weak Sub

Angular Blocky

10‐20 < 10% stones

Ap2 Ap2 0.03‐0.11 Sharp Irregular 10YR 3/3

Dark brown

2.5Y 2.5/1Reddish black

‐ SCL

Weak Angular Blocky

10‐20 < 10% stones

B₂₁ Bt1 0.11‐0.38 Gradual Even 5YR 4/6 Reddish brown

10YR 4/1Dark gray

‐ LMC

Strong Angular Blocky

20‐50 < 10% stonesHard

Carbonate nodules

B₂₂ Bt2 0.38‐0.65 Gradual Even 7.5YR 4/6 Strong brown

10YR 4/1Dark gray

‐ LMC

Strong Angular Blocky

20‐50 < 10% stones

Hard Carbonate nodules, charcol

B₂₃ Btk 0.65‐1.10 ‐ ‐ 7.5YR 4/6 Strong brown

2.5Y 5/2Weak red

15% R, D, D

MC Strong


20‐50 < 10% stones

Soft Carbonate nodules, Charcoal

Ap1

B21

B23

B22

Ap2

Ap1

Ap2

Bt1

Bt2

Btk

114


The pH of soil ranges from neutral to strongly alkaline.

EC levels are classified as being low to very low throughout the top 3 horizons of the soil profile.

Nitrogen levels are low in the topsoil and then decline slightly making them very low in the underlying horizons.

C:N ratio is very low throughout the profile.

Carbon levels are low in the soil profile.

CEC of the topsoil is considered extremely low. The middle depth is considered of moderate CEC whilst the subsoil has a high CEC.



Horizon pH

(1:5 H2O) EC (dS/m) Organic C (%) Total N (%) C:N ratio

NO‐3‐N

(mg/kg) Colwell P (mg/kg)

Ap1 6.0 0.06 0.6 0.06 10 7.9 44

Ap2 6.9 0.02 0.6 0.05 12 8.6 4

B21 8.7 0.12 0.4 0.05 8 3.6 1

B22 ‐ ‐ ‐ ‐ ‐ ‐ ‐

B23 ‐ ‐ ‐ ‐ ‐ ‐ ‐

Cation exchange properties (mmolc/kg) DTPA extractable micronutrient status (mg/kg) Horizon

CEC Ca Mg K Na Zn Cu Fe Mn

Ap1 91 63 22 5.1 0.7 1.1 0.02 85 1.5

Ap2 138 96 36 4.9 1.0 0.4 1 22 47

B21 329 239 81 4.2 3.9 0.1 0.8 11 3

B22 ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐

B23 ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐

CEC (mmolc/kg)

Ap1 Ap1 Ap1 Ap1

Ap2 Ap2 Ap2 Ap2

B21 B21 B21 B21

115


Sand ranges from being very high at the top of the profile and declines to being moderate. Clay content ranges from low to high, whilst silt is low.

Bulk density is low at the top of the profile and increases slightly to moderate levels.

Field capacity moisture content of this soil is low, particularly for the sandy topsoil.

Conductivity declines down the soil profile.


Key physical soil properties

Particle Size Analysis (%) Moisture () Horizon

Clay (<2 µm)

Silt (2‐20 µm)

Fine sand (20‐200 µm)


Bulk density (g/cm

3) 10 kPa

1500 kPa (PWP)

0 kPa (FC)

Ap1 18.3 13.8 7.7 60.2 1.19 0.32 0.12 0.48

Ap2 26.2 19.5 6.4 47.9 1.28 0.37 0.17 0.47

B21 37.3 16.8 7.0 38.9 1.35 0.38 0.22 0.46

B22 40.6 17.2 5.7 36.5 1.41 0.39 0.251 0.45

B23 46.2 15.6 9.1 29.1 1.43 0.40 0.28 0.45


Horizon Silt

(2‐50 µm) Sand (50‐2000 µm)

Ap1 31.0 50.7

Ap2 39.2 34.6

B21 33.4 29.3

B22 33.2 26.2

B23 29.4 24.4

Ap2

B21 B21 B21 B21

B22

B23

Ap1

B22 B22 B22

B23 B23 B23

Ap1 Ap1 Ap1

Ap2 Ap2 Ap2

116

Moree within‐field spatial variability

Figure 1. Fine‐scale maps of spatial variation in: (a) topsoil colour, (b) soil ECa 0‐0.9m, (c) soil ECa 0‐

0.3m, (d) soil ECa 0.3‐0.9m, (e) crop yield.

117


Landform Wide, alluvial plains of the lower Macintyre River. Local relief is <9 m and most slopes are <1% conferring a complex drainage system in the area.


Quaternary alluvium. Clay alluvia have been deposited on the back plains of major streams.

Drainage class Imperfectly drained, with a low run‐on rate and a ponded run‐off rate. Very slow internal drainage.

Surface condition:

Periodic cracking, with loose fragments. The soil has low erodibility and the site a low erosion hazard.

Site disturbance

Very minor disturbance by grazing animals, as the site is a stock route. The dominant landuse in the region is broadacre cropping; the stockroute is bordered by irrigated and dryland cropping paddocks.

Native vegetation

Open woodland of coolabah (Eucalyptus coolabah), belah (Casuarina cristata) and myall (Acacia melvillei), with tussock grassland of curly Mitchell grass (Astrebla lappacea) and Queensland bluegrass (Dichanthium sericeum).

Microrelief Normal gilgai with 0.15 m vertical intervals and approximately 6 m horizontal intervals.

Climate This area has unreliable, summer dominant rainfall, causing periods of drought and flood events. The average annual rainfall is 592 mm. The mean January maximum temperature is 34.1°C, while the mean July minimum temperature is 4.5°C.

Profile 9: South Callandoon, Goondiwindi, Queensland

118

0 1 km

Queensland

New South Wales

119

2. Description of soil profile A black, shrink‐swell, cracking clay soil that formed as a result of different alluvial events on the flood

plain of the lower Macintyre River.

Soil morphology

MC= medium clay

Australian Soil Classification: Black Vertosol (VE AE)

World Reference Base: Grumic Sodic Mollic Gypsic Calcic Vertisol (Humic, Pallic)

Soil Taxonomy: Sodic Haplustert (Very Fine, Smectitic, Thermic)


Horizon Depth (m)


Texture grade


Segregations

1A 1A 0.0‐0.1 Clear Even 2.5Y 3/2 Dusky red

2.5Y 3/1 Very dark gray

MC ModerateSub‐angular

blocky 20‐50

1B1 1Bt1 0.1‐0.5 Gradual Even 2.5Y 2.5/1

Reddish black 5Y 2.5/1 Black

MC Strong Angular blocky

20‐50

<2% Mn hard nodules (5‐15mm)

1B2 1Btss 0.5‐0.7 Gradual Even 5Y 3/1

Very dark gray 10YR 4/1 Dark gray

MC Strong Lenticular 20‐50 <2% carbonate soft nodules (5‐15mm)

2B21 2Bt1 0.7‐1.1 Diffuse Even 5Y 4/1

Dark gray 10YR 4/1 Dark gray


20‐50

2B22 2Bt2 1.1‐1.6 Diffuse Even 5Y 5/2

Olive gray 5Y 5/2

Olive gray MC Strong

Angular blocky

20‐50

<2% Mn hard nodules (5‐15mm)

2B23 2Bt3 1.6‐2.0 ‐ ‐ 5Y 6/2

Light olive gray2.5Y 6/2

Light olive grayMC Moderate

Angular blocky

20‐50 ‐

1A

1B1

1B2

2B21

2B22

2B23

1A

1Bt1

1Btss

2Bt1

2Bt2

2Bt3

120

3. Soil mineralogy

X‐ray diffraction patterns of basally oriented clays shows the presence of smectite, kaolinite

and illite. Smectite is highest in horizons 1B1. In addition to the phyllosilicates, the random

powder diffraction patterns identified quartz and small amounts of feldspars.

X‐ray diffraction patterns of the oriented clay fraction of 1A horizon soil after various pre‐



Thin sections

The left image (PPL) shows an accumulation of ellipsoidal faunal excrement in the pore spaces of the

1B1 horizon. The right image (PPL) shows the strong angular blocky microstructure of the clayey 2B22

horizon.

121


The pH values for this profile are neutral to moderately alkaline (7.39‐8.26).

The EC values for this profile range from very low to extreme.

The carbon contents are considered to be extremely low to moderate, ranging from 0.08% in the bottom horizon to 1.54% in the top horizon.

The total nitrogen in all horizons is considered as very low (<0.05%) to low (0.05‐0.15%).

The cation exchange capacity (CEC) is high throughout the entire profile. Chemical properties of soil profile


Horizon pH

(1:5 H2O) EC


Total N (%)

C:N ratio

NO‐3‐N


PBI‐Colwell

SO4 (mg/kg)

Avail. K (mg/kg)

Cl (mg/kg)

1A 8.26 0.07 1.54 0.12 12.8 8.5 56 98 5.4 420 22

1B1 7.93 0.63 0.98 0.07 14.0 1 5 ‐ ‐ 160 ‐

1B2 8.08 0.96 0.93 0.05 18.6 1 5 ‐ ‐ 150 ‐

2B21 8.14 1.77 0.32 0.03 10.7 1 5 ‐ ‐ 210 ‐

2B22 8.01 0.88 0.11 0.02 16.0 1 5 ‐ ‐ 290 ‐

2B23 7.39 0.87 0.08 0.02 4.0 1 7 ‐ ‐ 280 ‐

Cation exchange properties (mmolc/kg) DTPA extractable micronutrient status (mg/kg) DCB (%) Horizon

CEC Ca Mg K Na Al Zn Cu Fe Mn Al Fe

1A 270 160 91 11 8.3 ‐ 0.92 1.3 31 30 0.5 0.1

1B1 311 160 99 4 48 ‐ ‐ ‐ ‐ ‐ 0.4 0.1

1B2 335 160 110 3.9 61 ‐ ‐ ‐ ‐ ‐ 0.3 0.1

2B21 376 210 99 5.5 61 ‐ ‐ ‐ ‐ ‐ 0.2 0.1

2B22 374 110 91 7.5 65 ‐ ‐ ‐ ‐ ‐ 0.2 0.1

2B23 248 95 81 7.3 65 3.5 ‐ ‐ ‐ ‐ 0.2 0.1

CEC (mmolc/kg)

1A 1A 1A 1A

1B1 1B1 1B1 1B1

1B2 1B2 1B2 1B2

2B22 2B22 2B22 2B22

2B21 2B21 2B21 2B21

2B23 2B23 2B23 2B23

122

Profile physical characteristics

The particle size analysis reflects a low coarse sand content, low silt content and high to very high clay content throughout all the horizons to a depth of 2.2 m.

The bulk density of the soil profile increases going down the profile for the first three horizons, ranging from 1.31 to 1.53 g/cm3. All horizons have moderate bulk density levels.

Penetration resistance reflects a medium to very dense degree of soil consolidation. Soil physical characteristics


Clay (<2 µm)

Silt (2‐20 µm)

Fine sand (20‐200 µm)


Bulk density (g/ cm

3) 10 kPa

1500 kPa (PWP)

0 kPa (FC)


1A 46 32 14 8 1.31 0.43 0.29 0.48 1.03

1B1 61 24 9 6 1.42 0.41 0.29 0.45 2.49

1B2 67 18 9 6 1.53 0.38 0.28 0.42 2.9

2B21 81 4 11 5 1.47 0.4 0.29 0.44 ‐

2B22 69 15 11 4 1.41 0.41 0.29 0.46 ‐

2B23 68 15 13 4 1.60 0.36 0.27 0.39 ‐


Horizon Silt

(2‐5 µm) Sand (50‐2000 µm)

1A 47 7

1B1 33 6

1B2 24 9

2B21 4 15

2B22 19 12

2B23 20 12

1B1

1B1 1B1 1B1 1B1

1B2 1B1 1B1

1A

1B1

1B2

1A 1A 1A 1A

2B22 2B22 2B22 2B22

2B21 2B21 2B21

2B21

2B23 2B23 2B23

123

Day 5

Goondiwindi to Toowoomba

Presenters:

Andrew Biggs

QLD Department of Environment and Resource Management


Des McGarry



Jenny Foley



The tour organisers and the Congress Committee would like to acknowledge the Traditional Owners

and Custodians of this land (the Bigambul people) and pay respect to the Elders both past and

present, for they hold the memories, the traditions, the culture and hopes of Aboriginal Australia.

125

Itinerary 8:00 Depart Goondiwindi 8:20 Site 1 Wondalli Gilgaied Grey Vertosol 9:35 Site 2a Yelarbon Extremely alkaline soils with unique vegetation 10:00 Site 2b Yelarbon Cultural heritage site (eat smoko) 10:25 Depart Yelarbon site Have option of going back thru town if people need to use toilet Gore (Site 3) Brief toilet stop, gravelly soils 1:15 Site 4 Bulloak Sodosol 2:45 Site 5 Pampas Black Vertosol, lysimeters, geophysics 5:00 Site 6 Toowoomba Red Ferrosol pit (drinks & nibblies)

Regional geology From Goondiwindi to Toowoomba, we will be transiting two major geological provinces – the Great

Artesian Basin (GAB) and the New England Fold Belt. The GAB is an intra‐cratonic basin that extends

from far north Queensland to South Australia. It is the largest artesian basin in the world. In

southern inland Queensland, it is comprised primarily of Cretaceous argillaceous sediments overlying

(and capping) quartzose sandstones. Water quality in the capping sequences is generally poor, while

that in the sandstones is generally good. In some areas, e.g the Carnarvon Ranges, the quartzose

elements outcrop in an inclined manner, leading to “GAB recharge zones”. In general however,

recharge rates are very slow (thousands of years). In discharge zones e.g where the sandstones lap

up onto hard rock outcrop or faults occur, GAB springs may be present.

Overprinting the Cretaceous landscape are extensive areas of deep weathering (mostly during the

Tertiary), and extensive fluvial systems, some of which also date back to the Tertiary. Weathering

zones are often lateritic and may be more than 30 m thick. Residuals often possess ferricrete and

other forms of induration/silicification, particularly in the west. Tertiary rounded gravels were

126

deposited in some areas, and are present as both outcrop and subcrop. The fluvial systems vary in

age, but most of the larger rivers have occupied their valleys since pre‐Holocene, and maximum

alluvial thickness is generally 100‐110 m. In the Balonne River floodplain to the west, current

exposures of Tertiary gravels are more than 100 m above the bottom of the alluvial fill. The palaeo‐

valley is about 200 m below current land surface in one area, and there is some evidence to suggest

the oldest alluvia may be Miocene (the oldest dated alluvia is Early Pliocene). Some folding and

faulting has occurred in the region post Tertiary.

Figure 4 Basins within the eastern GAB

In the east, the GAB laps onto the hard rocks of the Texas Block (the Traprock and the Granite Belt) –

part of the New England Fold Belt (Figure 2). The Texas Block is comprised primarily of Carboniferous

metasediments (the Traprock), with some limestone, volcanics and re‐worked Permian sediments.

The various granitoids of the Granite Belt are primarily Triassic to late Permian. Both landscapes are

steep, with shallow soils, and incised drainage lines, although in parts of the Granite Belt there are

areas of gently undulating, more weathered landscapes.

The Kumbarilla Ridge represents the boundary between two sub‐basins within the GAB – the Surat to

the west and the Clarence‐Moreton to the east. The latter wraps around, and laps onto the Texas

Block and Granite Belt rocks on the western and northern sides i.e in both the Border Rivers and

Condamine catchments (Figure 3). Jurassic sandstones are uppermost in the Clarence‐Moreton sub‐

basin, primarily coal measures and labile feldspathic sandstones.

127

Figure 5 Schematic cross-section of geological units

Abutting the northern end of the Granite Belt and the Texas Block are the olivine basalts of the Main

Range Volcanics. These extend northwards, and form the eastern edge of the Condamine

catchment. At this point, they also form the Great Escarpment. The volcanics both intrude through,

and overly the Jurassic sandstones of the area. In areas such as Toowoomba, there is a deeply

weathered surface (The Toowoomba Plateau). The Condamine valley is comprised of erosional

landscapes of basalt and Jurassic sandstones in the uplands, with an extensive valley floor of

colluvial/fluvial material.

Figure 6 Regional geology

Geomorphology Sites 1 and 2

Goondiwindi lies on the Macintyre River floodplain. This is comprised of Quaternary alluvia,

overlying labile Jurassic to Cretaceous sediments, which slope into NSW. Running north‐south

through the town is the Goondiwindi Fault. The floodplain has been fed by Macintyre Brook and the

Dumaresq River in Queensland, and the Macintyre River from NSW. These rivers all have different

source materials, which combined with the lengthy evolution of the floodplain, has led to a wide

128

variety of alluvial soils. To the north and east, the lower uplands are comprised of fresh argillaceous

sediments, giving rise to clay soils that are extensively cropped. The higher uplands are more

quartzose, and in parts lateritised. Soils are sandier, and used for grazing and forestry.

Driving from Goondiwindi to Site 1, we quickly leave the younger alluvia, and cross onto contrasting

relict flow paths of the Macintyre‐Dumaresq system (Figure 4). The better soils, which are

extensively cultivated, are typically Grey Vertosols with varying amounts of microrelief (gilgai),

originally covered in brigalow/belah (Acacia harpophylla/Casuarina cristata) communities. At the

other end of the spectrum are strongly alkaline, sodic, texture contrast soils (Sodosols), generally

vegetated with poplar box/pilliga box (Eucalyptus populnea/E. pilligaiensis) communities.

Figure 7 Tour route from Goondiwindi to Inglewood

129

Site 10a Wondalli This site lies on the older alluvia of the Macintyre River Floodplain. The site is a gilgaied Grey

Vertosol, typical of landscapes known locally as “brigalow claysheet”. These are generally

older/relict alluvia, and the soils have accumulated salt and developed gilgai. It is common for

brigalow (Acacia harpophylla) to only grow on the mounds, and in this case, belah (Casuarina

cristata) which is more tolerant of waterlogging,

is growing in the depressions. These soils are

used extensively for grain cropping, unless the

gilgai are too large. Laser levelling of paddocks is

common. Mounds of gilgai are typically crusting,

have less ground cover, are slightly lighter

textured and more sodic than the depressions,

which are often (but not always) heavier textured,

darker, more fertile and exhibit a more

cracking/self‐mulching surface. No one knows

how the gilgai form.

This site displays many of the typical features,

although it lacks the gypsum frequently found in

similar soils to the west. Gypseous horizons

invariably occur below the carbonate horizon, and

mark the EC and Cl bulge i.e they are present at

the long‐term wetting front. Manganese laminae

are also a common feature in the mid to lower profile. Large slickensides are common, as is large

prismatic structure in the subsoil. Deep coring of these soils indicates that below the wetting front,

both general morphology and chemistry remain constant unless there is a substantial change in

texture. Zones of weak structure are not uncommon, although the reasons for this are not clear.

While brigalow/belah clays are extensively cropped, the presence of high Cl, high EC and low pH

leads to “subsoil constraints” to production of more sensitive crops such as chickpea. These subsoil

constraints have been studied extensively in recent years by agronomists (although pedologists have

known about them for decades!).

Deep drainage in Grey Vertosols has been studied in recent years using the chloride balance method.

It has revealed that under native vegetation, long‐term annual average deep drainage is <1 mm/yr.

When cleared it can increase to as much as 2 mm/yr and when cropped (long‐fallow wheat), it can be

as much as 15 mm/yr. While these are average figures, deep drainage is in fact very episodic.

Neither of these things are surprising, given evaporation is >> rainfall, and rainfall is highly variable.

Key features of the soil:

High clay content

High salinity, sodicity

High fertility, moderately high PAWC

A1

B21

B22

B23

B24

B25

130

0

30

60

90

120

1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

Year

An

nu

al d

rain

age

(mm

)

(b) sorghum

Figure 10 Modelled annual deep drainage, Dalby

Figure 8 Chloride loss under a gilgaied Grey Vertosol

Figure 9 Modelled annual average deep drainage, Grey Vertosol at Goondiwindi

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

0 500 1000 1500 2000 2500 3000

Chloride (mg/kg)

Dep

th (

m) Trees mound mean

Trees dep mean

Crop mound mean

Crop dep mean0

10

20

30

40

50

60

Wood

land

Pastu

res

Buffel

Oppo

Sorghu

m

Whea

t

Irriga

ted

Dra

inag

e (m

m)

131

Site 10b Wondalli depression General description: Gilgaied uniform cracking grey clay with pH inversion and subsoil salt

accumulation, formed on relict alluvia

Distribution: Typical of soils found extensively throughout floodplains of southern inland Queensland

Parent material: Alluvium from Jurassic and Cretaceous sedimentary rocks

Location: -28.49016° 150.51339°

Landform: Alluvial plain Vegetation: Belah (Casuarina cristata) tall closed forest Microrelief: Normal gilgai Surface condition: Periodic cracking, weak surface crusting Permeability: Slowly permeable Drainage: Imperfect to poor ASC: Episodic, Epipedal, Grey Vertosol PPF: Ug5.24

WRB: Calcic Stagnic Sodic Grumic Vertisol (Bathy, Manganiferric)

Soil Taxonomy: Sodic Epiaquert (Very Fine, Smectitic, Thermic) OR Sodic Haplustert

Profile description - depression

Horizon Depth Colour Texture Structure Segregations Boundary (m) (moist) Grade Size Type distinctness A1 0 - 0.03 grey (10YR5/1) light medium clay moderate <2 granular - clear

B21 0.03 - 0.2 grey (10YR5/1) heavy clay strong <2 lenticular <2%, <2mm calcareous concretions

gradual

B22 0.2 - 0.5 grey (10YR5/1) heavy clay strong 2-5 lenticular <2%, <2mm calcareous concretions; 2-10%, <2mm manganiferous laminae

gradual

B23 0.5 - 0.8 greyish brown (10YR5/2)

heavy clay moderate moderate

5-10 (parting to) 2-5

lenticular lenticular

<2%, <2mm calcareous concretions

gradual

B24 0.8 - 1.1 light brownish grey (10YR6/2)

heavy clay moderate strong


prismatic lenticular

10-20%, <2mm manganiferous laminae

gradual

B25 1.1 - 1.7 light brownish grey (2.5Y6/2)

heavy clay strong strong



-

Laboratory analysis - depression

pH EC Cl NO3

(1:5 soil/water solution) Org.C (W/B)

TN C:N ratio

Extr. P (Colw.)

Extr P (H2SO4)

Exch. K(HCl)

Extr. S (ICP)

Extr. B (CaCl2)

DTPA extr. trace elements (mg/kg)

dS/m mg/kg mg/kg % % mg/kg mg/kg meq/100g mg/kg mg/kg Cu Zn Mn Fe

0 - 0.1 7.2 0.1 58 2 0.97 0.08 12.1 24 21 0.8 6 0.7 1.3 0.4 72.2 29.1

Depth pH EC Cl NO3

(1:5 soil/water solution) Org.C (W/B) TN

Exchangeable cations – alcoholic (pH8.5) (cmolc/kg)

Extractable cations - NH4Cl (pH7) (cmolc/kg)

(m) dS/m mg/kg mg/kg % % Ca Mg Na K CEC Ca Mg Na K

0 - 0.1 7.2 0.10 58 2 0.97 0.08 17.1 9.3 2.1 0.9 27 17.5 9.7 2.3 0.8

0.2 - 0.3 8.5 0.86 896 1 0.67 0.06 17.0 11.4 6.5 0.4 33 18.7 11.3 7.7 0.3

0.5 - 0.6 8.7 0.95 895 1 0.78 0.03 15.6 12.1 8.0 0.2 31 23.4 12.2 9.3 0.2

0.8 - 0.9 8.0 0.79 847 1 0.35 0.02 14.7 10.3 7.3 0.3 31 12.7 10.5 8.9 0.3

1.1 - 1.2 6.7 0.76 922 1 0.19 0.02 12.7 10.0 7.2 0.3 27 10.8 9.5 8.2 0.3

1.4 - 1.5 5.3 0.77 853 1 0.20 0.02 11.9 9.1 6.4 0.3 30 10.1 9.0 8.0 0.3

Depth Na corr Extr. S (ICP) Base Status ESP Particle size Total element XRF

Moistures ADMC 15B

(m) meq/100g mg/kg % CS FS SI CL P K S % % R1

0 - 0.1 2.10 6 41 8 3 19 19 63 0.027 0.474 0.02 3.3 19.9 0.70

0.2 - 0.3 5.00 112 51 20 3 21 17 63 0.020 0.406 0.04 3.4 20.7 0.84

0.5 - 0.6 6.46 157 49 26 4 18 19 61 0.018 0.426 0.04 4.0 20.4 0.92

0.8 - 0.9 6.13 127 48 24 3 23 17 63 0.018 0.568 0.02 3.2 20.8 0.96

1.1 - 1.2 5.40 110 43 27 4 23 17 61 0.017 0.668 0.03 3.1 20.2 0.95

1.4 - 1.5 5.13 129 48 21 2 22 17 61 0.016 0.821 0.03 3.4 20.4 0.93

PAWC ~ 150 mm

132

Site 10c Wondalli mound Landform: Alluvial plain Vegetation: Brigalow (Acacia harpophylla) tall closed forest Microrelief: Normal gilgai Surface condition: Periodic cracking, surface crusting Permeability: Slowly permeable Drainage: Imperfect to poor ASC: Episodic, Crusty, Grey Vertosol WRB: Calcic? Sodic Vertisol PPF: Ug5.24

Profile description - mound Horizon Depth Colour Texture Structure Segregations Boundary

(m) (moist) Grade Size Type distinctness A1 0 - 0.03 dark grey

(10YR4/1) light clay (silty)

moderate 10-20mm platy - clear

B1 0.03 - 0.4 very dark greyish brown (10YR3/2)

medium heavy clay

moderate strong

10-20mm (parting to) 5-10mm

prismatic angular blocky

- gradual

B21 0.4 - 0.9 dark greyish brown (10YR4/2)

heavy clay moderate moderate



<2%, 2-6mm calcareous concretions

gradual

B22 0.9 - 1.2 light brownish grey (10YR6/2)

heavy clay moderate strong



10-20%, 2-6mm manganiferous laminae

gradual

B23 1.2 - 1.6 light brownish grey (2.5Y6/2)

medium heavy clay

strong strong



<2%, 2-6mm manganiferous laminae

Laboratory analysis - mound

pH EC Cl NO3


TN C:N Ratio

Extr. P(Colw.)

Extr. P(H2SO4)

Exch. K(HCl)

Extr. S (ICP)

Extr. B (CaCL2)


dS/m mg/kg mg/kg % % mg/kg mg/kg meq/100g mg/kg mg/kg Cu Zn Mn Fe

0 - 0.1 6.5 0.1 86 2 1.33 0.11 12.1 19 17 0.6 11 0.7 1.1 0.4 115 45.7

Depth pH EC Cl NO3

(1:5 soil/water solution) Org.C (W/B) TN

Exchangeable cations - alcoholic (cmolc/kg)

Extractable cations - NH4Cl (cmolc/kg)

(m) dS/m mg/kg mg/kg % % Ca Mg Na K CEC Ca Mg Na K

0 - 0.1 6.5 0.10 86 2 1.33 0.11 14.5 6.9 1.7 0.7 28 13.0 7.0 1.6 0.7

0.2 - 0.3 6.6 0.66 764 1 0.87 0.07 15.2 9.5 4.8 0.3 30 13.6 9.1 6.0 0.3

0.5 - 0.6 8.5 0.92 926 1 0.60 0.04 16.3 11.1 6.8 0.2 29 9.4 8.9 8.1 0.3

0.8 - 0.9 8.1 0.85 929 1 0.28 0.02 14.0 10.6 7.8 0.2 28 13.1 11.1 9.2 0.3

1.1 - 1.2 7.1 0.77 937 1 0.21 0.02 11.1 9.2 7.8 0.2 28 12.9 11.1 9.0 0.3

1.4 - 1.5 5.5 0.77 870 1 0.24 0.01 10.8 8.0 6.7 0.2 26 10.7 10.1 8.9 0.3

Depth Na corr Extr. S (ICP)

Base Status ESP Particle size Total element XRF

Moistures ADMC 15B

(m) meq/100g mg/kg % CS FS SI CL P K S % % R1

0 - 0.1 1.37 11 53 6 5 29 20 51 0.034 0.461 0.02 2.8 19.9 0.61

0.2 - 0.3 3.64 113 49 16 3 22 19 59 0.027 0.395 0.04 2.8 20.7 0.77

0.5 - 0.6 5.29 132 44 24 3 22 17 63 0.026 0.428 0.04 2.9 20.4 0.79

0.8 - 0.9 6.29 110 43 28 3 19 16 63 0.017 0.537 0.02 3.2 20.8 0.96

1.1 - 1.2 6.08 97 46 28 5 21 18 59 0.017 0.619 0.03 3.1 20.2 0.96

1.4 - 1.5 5.99 112 45 26 5 24 16 56 0.018 0.705 0.03 3.4 20.4 0.98

133

Mineralogy Depth

(m)

Amorph/

Unknown

Qtz Calcite Plag. Musc. ML Illite/

smectite

Kaol Montm. Kaol. Smect.

Depr. 0‐0.1 37.7 37.1 2.9 19.5 2.8 min. maj.

0.2‐0.3 min. maj.

0.5‐0.6 33.4 34.9 1.1 6 21.7 2.9 min. maj.

0.8‐0.9 min. maj.

1.1‐1.2 34.9 35.6 8.1 21.3 min. maj.

1.4‐1.5 19 40.9 8.5 2.6 2.6 23.7 2.7 min. maj.

Mnd 0‐0.1 27.4 41.2 7.5 0 0 21.1 2.8 min. maj.

0.2‐0.3 40.8 39.2 1.1 2.1 14.1 2.7 min. maj.

0.8‐0.9 min. maj.

1.1‐1.2 min. maj.

1.1‐1.2 38.1 39.8 4.9 15.4 1.8 min. maj.

1.4‐1.5 37 40.9 5.4 14.7 2 min. maj.

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0 500 1000

Cl (%)

Dep

th (

m)

Depression

Mound

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0 0.5 1

EC 1:5 (dS/m)

Dep

th (

m)

Depression

Mound

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

5 6 7 8 9

pH

Dep

th (

m)

Depression

Mound

Depression

0% 20% 40% 60% 80% 100%

0

0.25

0.55

0.85

1.15

1.45

Dep

th (

m)

CS FS SI CL Mound

0% 20% 40% 60% 80% 100%

0

0.25

0.55

0.85

1.15

1.45

Dep

th (

m)

CS FS SI CL

134

Site 11a Yelarbon Lying at the junction of Macintyre Brook and the Dumaresq River, just north of the Queensland‐New

South Wales border (Figure 11), the area around Yelarbon consists of landscapes unique in southern

Queensland. Because of its barren appearance, the area is commonly referred to as the Yelarbon

‘desert’. The slightly to severely degraded landscapes have also been referred to as the Yelarbon

‘salinity scald’ (Knight et al. 1989). Until recently, detailed laboratory analysis existed for only one

soil profile in the ~70 km2 area.

Yelarbon soil

Figure 11 Yelarbon area The Yelarbon area. Results for Sites A, B & C are illustrated in Figures 3 & 4. Site D was described by Thwaites & Macnish (1991)

The Yelarbon ‘desert’ is mapped as spinifex grassland with scattered low trees and shrubs (DERM

2009). It is home to some locally unique species, in particular the spinifex (Triodia scariosa) and tea

tree (Melaleuca densispicata). It is the most easterly occurrence of spinifex in southern Queensland,

while the Melaleuca is limited to small isolated communities scattered across southern inland

Queensland. Bull oak (Allocasuarina luehmannii), also present on the scalded areas, has a more

widespread distribution. The vegetation of the area is highly disturbed and degraded, with weeds

such as mother of millions (Bryophyllum spp.)

common. Fensham et al. (2007) recently

surveyed the floristics of the scalded and non‐

scalded areas, and investigated relationships to

factors such as drainage lines and soil pH. They

refined the mapping of the ‘desert’ area and

found gradients in floristic patterns were

related primarily to drainage lines, and

secondarily to soil pH. In areas marginal to the

‘desert’, emergent species such as Pilliga box

(Eucalyptus pilligaensis), poplar box (Eucalyptus

populnea) and belah (Casurina cristata) are

common, while spinifex is absent. Figure 12 Degraded land at Yelarbon

A1

A21

A22e

B2k

135

Site 11b - Yelarbon General description: Groundwater influenced extremely sodic, alkaline texture contrast soils

Distribution: Unique to the Yelarbon area

Parent material: Altered alluvia from Jurassic sediments and Devonian/Carboniferous

metasediments

Landform: Alluvial plain Location: -28.58481° 150.74743°° Vegetation: Melaleuca densispicata dwarf woodland, Triodia spp. Microrelief: Sheet erosion Surface condition: Hardsetting to crusting Permeability: Slowly permeable Drainage: Poor ASC: Calcic, Hypernatric, Brown Sodosol PPF: Db3.43

WRB: Stagnic Solonetz (Glossalbic, Abruptic, Ruptic?, Magnesic, Epiarenic)

Soil Taxonomy: Glossic Natraqualf (Fine Loamy, Mixed, Active, Thermic)

Profile Description Horizon Depth Colour Texture Structure Segregations Boundary

(m) (moist) Grade Size (mm) Type distinctness

A1 0 - 0.04 brown (7,5YR4/4)

sandy loam

weak 10-20 platy - sharp

A2e 0.04 - 0.08

light yellowish brown (10YR6/4) 2.5Y 7/2 dry

sandy loam

weak 10-20 platy - sharp wavy

B21 0.08 - 0.2 strong brown (7.5YR4/5)

medium clay

strong moderate

20-50 (parting to) 5-10

columnar angular blocky

- clear

B22k 0.2 - 0.3 light yellowish brown (10YR6/4)

sandy light clay

moderate strong

20-50 (parting to) 5-10


10-20%, 2-6mm calcareous soft segregations

gradual

B23k 0.3 - 0.6 yellowish brown (10YR5/5)

sandy light clay

moderate strong

20-50 (parting to) 5-10



gradual

B24k 0.6 - 1.3 light yellowish brown (10YR6/4)

sandy light clay

moderate strong

20-50 (parting to) 5-10



gradual

B25 1.3 - 1.6 yellowish brown (10YR5/4)

sandy light clay

moderate strong

20-50 (parting to) 5-10


<2%, 2-6mm manganiferous laminae

Laboratory Analysis pH EC Cl NO3

(1:5 soil/water solution)

ANC bt

Org.C (W/B)

TC (Dum.)

TN (Dum.)

C:N ratio

Exch. K (HCl)


dS/m mg/kg mg/kg % CaCO3 % % % meq/100g Cu Zn Mn Fe

0-0.04 9 0.32 101 1 <0.5 1.08 0.74 0.05 21 0.3 0.2 2.7 15.8 12.8

0.04-.0 8 9.1 0.05 21 <1 <0.5 0.25 0.22 <0.03 17 0.1 <0.1 0.4 5.2 3.1

Depth pH EC Cl NO3

(1:5 soil/water solution) Org C (W/B)

TC (Dum)

TN (Dum)

C:N Ratio

Base Status

Exchangeable cations -‘alcoholic’ (m.eq/100g) ESP

Extr. B (CaCl2) Particle size ADMC

(cm) dS/m mg/kg mg/kg % % % (calc) Ca Mg Na K CEC % mg/kg CS FS SI CL % R1

0-0.04 9.0 0.32 101 1 1.08 0.74 0.05 21 113 3.1 1.0 3.6 0.2 9 40 0.1 34 53 7 8 <1.5 0.81

0.04-0.08 9.1 0.05 21 <1 0.25 0.22 <0.03 17 67 2.1 0.8 1.9 0.1 4 47 0.2 37 56 5 6 <1.5 0.80

0.08-0.20 10.4 0.76 24 1 0.49 0.4 0.07 7 100 1.8 0.5 29.6 0.1 35 84 1.3 11 33 25 35 <1.5 0.76

0.20-0.30 10.5 0.84 34 2 0.20 0.18 <0.03 13 110 1.5 0.5 29.0 0.3 33 87 1.2 7 40 28 30 <1.5 0.97

0.30-0.40 10.5 0.53 44 2 - - - - 129 1.1 0.4 24.9 0.3 27 91 0.7 11 45 28 21 <1.5 0.89

0.40-0.50 10.5 0.58 57 1 - - - - 145 1.7 0.4 25.3 0.3 29 86 0.7 13 31 35 20 1.6 0.83

0.50-0.60 10.5 0.55 71 2 0.15 0.1 <0.03 10 153 1.4 0.3 26.7 0.3 30 90 0.6 18 37 32 19 2.2 0.75

0.60-0.70 10.5 0.52 87 2 - - - - 171 1.2 <0.3 24.8 0.2 29 85 0.5 21 26 36 17 <1.5 0.64

0.70-0.80 10.4 0.55 108 2 - - - - 153 1.2 0.3 27.4 0.3 29 94 0.5 15 36 35 19 <1.5 0.65

0.80-0.90 10.4 0.61 123 2 0.18 0.17 <0.03 12 150 1.3 0.3 26.7 0.3 30 88 0.6 13 37 34 20 1.6 0.67

0.90-1.0 10.5 0.59 120 2 - - - - 85 1.0 <0.3 11.1 0.5 17 65 0.6 13 31 37 20 <1.5 0.76

136

1.00-1.10 10.5 0.64 124 2 - - - - 85 1.7 <0.3 11.1 0.2 17 65 0.7 16 36 32 20 <1.5 0.79

1.10-1.20 10.5 0.62 124 2 0.13 0.14 <0.03 9 64 1.1 <0.3 11.1 0.2 14 79 0.7 14 39 29 22 <1.5 0.85

1.20-1.30 10.5 0.58 110 1 - - - - 100 1.2 <0.3 20.2 0.3 22 91 0.7 16 39 27 22 <1.5 0.83

1.30-1.40 10.5 0.55 100 1 - - - - 95 1.2 <0.3 18.8 0.2 21 89 0.9 19 32 29 22 <1.5 0.91

1.40-1.50 10.4 0.6 94 1 0.20 0.14 <0.03 13 88 1.2 <0.3 19.3 0.3 21 91 1.1 23 34 22 24 <1.5 0.96

1.50-1.60 10.4 0.79 83 1 - - - - 67 1.3 <0.3 19.2 0.3 23 83 0.1 30 34 17 21 <1.5 1.00

Mineralogy Depth

(m)

Amorph./

Unknown

Qtz Calcite Analcite Plag. Musc. ML Illite/

smectite

Kaol. Montm. Kaol. Illite/

Mica

Smect.

0‐0.04 6 75.9 8.8 0.6 5.8 2.9 min. min.

0.08‐0.2 14 50.5 9.4 10.9 4.5 5.1 5.7 min. min. min.

0.2‐0.3 34.5 43.2 5.3 10.1 4.6 2.2 min. maj. maj.

0.4‐0.5 24.5 50.4 9.5 3.8 4.6 7.3 min. min. maj.

0.8‐0.9 21.8 49.2 10.9 2.6 7.1 8.4 min. min. maj.

1.1‐1.2 15.5 52 13.6 2.5 9.3 7 min. maj. min.

1.4‐1.5 7.6 61.6 1.4 12.9 1.3 8.2 6.9 min. maj. min.

0% 20% 40% 60% 80% 100%

0

0.14

0.35

0.55

0.75

0.95

1.15

1.35

1.55

Dep

th (

m)

CS FS SI CL

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

8 9 10 11

pH

Dep

th (

m)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

0 0.25 0.5 0.75 1

EC 1:5 (dS/m)

Dep

th (

m)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

0 50 100 150

Cl (mg/kg)

Dep

th (

m)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

0 10 20 30 40

Clay (%)

Dep

th (

m)

137

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

5 6 7 8 9 10 11

pH (1:5 soil-water) D

epth

(m

)

Outside FringeDegraded

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0 0.2 0.4 0.6 0.8 1 1.2

EC 1:5 (dS/m)


0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0 300 600 900 1200

Cl (mg/kg)


0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0 20 40 60 80 100

ESP (%)


138

1948

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

4 5 6 7 8 9 10 11

pH (1:5soil:water)

Dep

th (

m)

Outside Desert

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

0 0.5 1 1.5 2 2.5

EC 1:5 (dS/m)

Dep

th (

m)

Outside Desert

Outside 6.64*Cl Desert 6.64*Cl

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

0 1000 2000 3000 4000

Chloride (mg/kg)

Dep

th (

m)

Outside Desert

139

Sheet and gull erosion at Yelarbon

Water ponding at Yelarbon

Coolmunda Dam & Macintyre Brook

Coolmunda Dam was built in 1963 to service the tobacco industry established on the Macintyre

Brook alluvia. It has a capacity of 69 000ML. Ironically, the tobacco industry collapsed at about the

same time the dam was commissioned. Since then, the main industry has been the production of

forage crops (e.g lucerne hay), with minor grain production and horticulture. Forage crops are grown

rather than cotton or grain because of the poor quality alluvial soils. Hardsetting and crusting

behaviour is a common problem.

The dam is fed by primarily by Macintyre Brook, but also by creeks such as Bracker Creek. Some of

these carry elevated salinity levels, due to dryland salinity in the Traprock. High chloride in the

irrigation water was one of the contributing reasons to the collapse of the local tobacco industry.

140

Site 12a Gore (Traprock) The Texas Block extends from Inglewood to the east, and continues into NSW. Within Qld, it is

comprised of two main elements – the Texas Beds (a complex of sediments and metasediments) and

east of these, the higher altitude igneous rocks of the

Granite Belt. The Texas Beds are Permian in age, and

highly folded, faulted and modified. Within the unit

lie small elements of limestone, and re‐worked

Permian sediments. The terrain varies from

undulating plains and rises on the western fringe

(where they are overlapped by the sedimentary rocks

of the GAB) to steep hills and ranges in the central

and eastern parts. A number of metalliferous (silver,

gold, arsenic) mines are found in the vicinity of the

Permian sediments within the broader unit. The

Traprock (as the Texas Beds are locally known)

contains gravelly, low fertility soils, but is a highly

valued wool production area. It produces the finest,

most valuable wool in Queensland. The Granite Belt

is a mix of horticultural production (vineyards),

grazing land and national park. Terrain varies from

undulating plains to steep mountains with bare rock

outcrop.

Karangi soil

Soils in the Traprock vary substantially, but are generally always very gravelly, and of moderate to

low fertility. They range from uniform texture profiles to texture contrast. The Permian sediments

tend to produce a more clayey soil on a subdued landform, while the limestones produce Red

Chromosols (Terra Rossa). Sheet and gully erosion are a common feature in overgrazed areas.

Thinning and clearing first commenced in the late 1800s, and regrowth management remains a

significant issue. Dryland salinity is a feature of some local catchments.

Gammie (Tenosol) Glentanna (Dermosol)

A1

A2e

B21

BC

141

Site 12b Traprock (Gore) General description: Gravelly to stoney sodic soils formed on various metamorphics

Distribution: Restricted to the Traprock

Parent material: Permian metasediments Location: 28.09647° S 151.67168° E Landform: Rises to hills Vegetation: Fuzzy Box (Eucalyptus conica) woodland Microrelief: None Surface condition: Soft to hardsetting Permeability: Slowly permeable Drainage: Imperfect PPF: Dy3.42ASC: Mesotrophic, Subnatric, Brown Sodosol WRB: Haplic Solonetz (Abruptic, Magnesic,

Epiclayic) Profile description Horizon Depth Colour Mottles Texture Structure Coarse Boundary

(m) Grade Type Size fragments distinctnes

s A1 0-0.2 brown

(10YR4/3) - clay loam - - - very abundant >90%

gravel large pebbles 20-60mm

gradual

A2e 0.2-0.35 yellowish brown (10YR5/4 moist) (10YR7/2 dry)

- sandy clay loam

- - - very abundant >90% gravel large pebbles 20-60mm

clear

B21 0.35-0.55

yellowish brown (10YR5/8)

few 2-10% fine <5mm faint yellow mottles

medium heavy clay

moderate

angular blocky

10-20mm

common 10-20% angular gravel medium pebbles 6-20mm

gradual

B22 0.55-0.7 brownish yellow (10YR6/6)

few 2-10% fine <5mm faint red mottles

medium clay

massive

- - common 10-20% angular large pebbles 20-60mm

gradual

C 0.7 + weathered rock

Laboratory analysis

pH EC Cl


TN

C:N Ratio

Acid-extract P Extr. K

dS/m mg/kg % % mg/kg meq/100g

0 - 0.10 6.0 0.01 10 2.1 0.11 19.1 <5 0.35

Depth pH EC Cl (1:5 soil/water solution)

Exchangeable cations - aqueous (meq/100g)

Particle size Base

Status Total element XRF

Moistures ADMC 15B

(m) dS/m mg/kg Ca Mg Na K ECEC CS FS SI CL P K S % % R1

0 - 0.10 6.0 0.01 10 2.2 1.4 0.1 0.3 4 27 42 15 14 29 0.040 1.20 0.015 0.8 4.7 0.77

0.20 - 0.30 6.0 0.03 10 0.7 2.9 0.3 0.2 4 21 34 2 41 10 0.019 1.19 0.009 0.9 6.4 0.87

0.30 - 0.40 6.0 0.08 59 0.9 7.4 1.0 0.2 10 - - - - - - - - - - -

0.50 - 0.60 6.3 0.54 725 0.4 11.2 4.5 0.1 16 10 29 18 40 41 0.011 1.84 0.012 2.0 13.0 0.96

0.80 - 0.90 7.4 0.60 772 0.2 8.4 6.3 0.1 15 28 32 2 38 39 0.012 2.43 0.008 1.4 8.0 0.77

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

0 10 20

ECEC (meq/100g)

Dep

th (

cm)

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

0 500 1000

Cl (mg/kg)

Dep

th (

m)

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

5 6 7 8

pH

Dep

th (

m)

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

0 0.5 1

EC (dS/m)

Dep

th (

m)

142


Texture contrast

High gravel/stone content

Bleached A2

Low fertility, PAWC

Salt bulge at depth

0% 20% 40% 60% 80% 100%

0

0.25

0.55

0.85

1.15

Dep

th (

m)

CS FS SI CL

143

Site 13a Karara The sandstones of the Kumbarilla Beds and Marburg Subgroup are common in the Condamine

catchment. Both units vary in lithology

from labile quartzose and feldspathic

sandstones to argillaceous materials. The

Marburg Subgroup will be encountered in

the Lockyer Valley on Saturday. Soils

formed on both geologies are typically

texture contrast and sodic (Sodosols and

Kurosols). Pale sands (Tenosols) are

common as local fluvial deposits. The

vegetation at this site (ironbark & bulloak –

Eucalyptus crebra & Allocasuarina

leuhmanii) are very indicative of sodic

texture contrast soils on the Darling Downs.

The bulloak is also home to a rare and threatened species – the bulloak Jewel Butterfly

(Hypochrysops piceatus).

These landscapes are of very low value for agricultural production due to a range of limitations,

including: low fertility, low PAWC, high sodicity, high bulk density, erodibility and hardsetting soil

surface. Management of regrowth and thickening are significant problems. When cleared and

managed appropriately, they can support improved pastures, but productivity remains low

compared to other grazing areas in the region. Ironbark and cypress pine are often harvested for

fence posts and mill timber.

C

A1

A2e

B21

B22


Texture contrast, high sand content

Bleached A2 horizon

Moderate to high salinity, sodicity in the subsoil

Low fertility, low PAWC

144

Site 13b Karara General description: Texture contrast soil formed on sandstone

Distribution: Mostly on the Kumbarilla Ridge

Parent material: Jurassic sedimentary rocks Location: 28.07836° S 150.56708° E Landform: Undulating plains to rises Vegetation: Bull oak (Allocasuarina luehmannii) forest Microrelief: None Surface condition: Soft to firm Permeability: Slowly permeable Drainage: Poor PPF: Dy2.43 ASC: Eutrophic, Mesonatric, Grey Sodosol WRB: Haplic Solonetz (Albic, Abruptic, Epiarenic,

Endoclayic)

Profile description Horizon Depth Colour Mottles Texture Structure Boundary

(m) (moist) Grade Type Size distinctnessA1 0 - 0.15 brown (10YR4/3)

light brownish grey (10YR6/2)

- loamy sand very weak - massive clear

A2e 0.15 - 0.3 pinkish white (7.5YR8/2) strong brown (7.5YR4/6)

- loamy sand weak - massive abrupt

B21 0.3 - 0.8 greyish brown (10YR5/2)

few 2-10% fine <5mm distinct orange mottles

sandy medium clay strong moderate


columnar angular blocky

gradual

BC 0.8 - 1.3 yellowish brown (10YR5/6)

few 2-10% fine <5mm distinct orange mottles common 10-20% fine <5mm distinct grey mottles

coarse sandy light clay

- - massive

Laboratory analysis

pH EC Cl NO3

(1:5 soil/water solution) pH

(CaCl2)Org.C(W/B)

TN

C:N Ratio

Bicarb P Acid-

extract PExch. K

(HCl) Extr. S (ICP)


(dS/m) (mg/kg) (mg/kg) % % (mg/kg) (mg/kg) (meq/100g) (mg/kg) Cu Zn Mn Fe

0-0.1 6.5 0.034 43 1 5.3 0.79 0.05 16 14 13 0.18 3 0.09 0.42 15 36

Depth pH EC Cl NO3

(1:5 soil/water solution) pH

(CaCl2) Base status

Exchangeable cations - alcoholic (meq/100g)

Particle size Total element XRFMoistures

ADMC 15B

(cm) dS/m mg/kg mg/kg Ca Mg Na K CEC CS FS SI CL P K S % % R1

0-0.1 6.1 0.07 56 4 5.3 71 3.6 1.1 - 0.3 5 57 31 6 7 0.024 0.200 0.023 0.6 3.4 0.63

0.2-0.3 6.5 0.01 21 1 5.0 16 0.1 0.2 - 0.1 2 55 36 6 3 0.005 0.148 0.006 0.1 0.6 0.97

0.5-0.6 8.5 0.16 146 1 6.8 33 3.1 6.1 2.6 0.3 14 34 24 4 37 0.009 0.304 0.007 1.7 13.1 0.98

0.8-0.9 9.1 0.27 280 1 7.6 41 2.6 6.1 3.1 0.3 13 52 16 - 30 0.010 0.290 0.014 1.3 11.1 1.00

1.1-1.2 9.1 0.39 487 1 7.9 69 5.3 4.0 1.9 0.2 12 47 28 7 17 0.006 0.340 0.008 0.8 - -

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 200 400 600

Cl (mg/kg)

Dep

th (

m)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 0.2 0.4 0.6

EC (dS/m)

Dep

th (

m)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

5 7 9

pH

Dep

th (

m)

145

The Condamine Valley The Condamine Valley is one of the headwater catchments of the Murray‐Darling Basin. Its eastern

edge is comprised of the Tertiary basalts and trachytes of the Main Range Volcanics. This also forms

the Great Escarpment and the Great Dividing Range. The basalt overlies the Jurassic sandstones of

the Clarence‐Moreton Basin. Small areas of the Granite Belt, Traprock and miscellaneous volcanics

occur in the southern end of the catchment.

The Condamine is comprised of five main landscapes

The steep ranges

The basaltic uplands

The sandstone landscapes

The granitic and metamorphic hills

The floodplain

Of these, the floodplain is the most important from an agricultural perspective, followed by the

basaltic uplands. The Condamine Floodplain is one of the most productive cropping areas in

Australia (and the world!). Irrigated and dryland cropping occurs on more than 80% of the floodplain

proper, where the soil type is almost exclusively heavy textured (clay >50%) Vertosols. Both surface

water and groundwater are used for irrigation. There are many natural resource management issues

associated with the agricultural development in particular surface and groundwater quality (pesticide

contamination), water quantity (over‐extraction), flow coordination (erosion), biodiversity loss and

land use conflict (with mining/gas and urban development). An obvious feature when driving across

the floodplain is strip‐cropping, which was first trialled in the area in the late 1960s by Hector Tod.

You will also notice that roads are not built up. This is an important design feature to allow flood

events to spread rather than concentrate.

0% 20% 40% 60% 80% 100%

0

0.25

0.55

0.85

1.15

Dep

th (

m)

CS FS SI CL

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 1 2 3 4

Ca/MgD

epth

(m

)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 10 20 30

ESP (%)

Dep

th (

m)

146

Site 14a Pampas Stuart Leadbetters has been the site of considerable research for more than a decade, starting with

compaction and permanent bed farming trials in the 1990s.

Currently it is one of a number of irrigation farms in

Queensland involved in studies of deep drainage. Associated

with this are investigations into groundwater recharge of the

Condamine alluvia.

The farm lies between the main branch and the “north

branch” of the Condamine River. It is on the lower level of

the floodplain, subject to over‐bank flooding. To the east, the

next terrace up is only subject to overland flow flooding

(water exiting the uplands to the east). The main Condamine

alluvia and the outwash fans are nearly exclusively Vertosols –

varying in colour, but generally black or grey – the latter

colour generally indicates less basaltic influence. They are

nearly all high in fertility, but subsoil salinity varies from low

levels in the basaltic Vertosols, to high levels in the sandstone

dominant alluvia. Subsoil colours are invariably browner,

redder or yellower than the upper profile. Subtle differences in aggregate size are recognised by

farmers, as they influence the capacity to grow certain crops e.g millet.

Anchorfield soil

Figure 13 Central Condamine valley land resources

A1

B24

B21

B22

B23

147

Site 14b Pampas General description: Deep cracking dark clays on alluvial plains

Distribution: Condamine alluvia

Parent material: Mixed (basalt dominant) Location: Landform: Level plains Vegetation: Bluegrass grasslands Microrelief: None Surface condition: Self-mulching, cracking Permeability: Slowly permeable Drainage: Slowly drained PPF: Ug5.17ASC: Endohypersodic, Self‐mulching Black Vertosol

WRB: Calcic Mollic Sodic Grumic Vertisol (Humic?, Pallic)

Soil Taxonomy: Sodic Haplustert (Very Fine, Smectitic, Thermic)

Profile description Horizon Depth Colour Texture Structure Segregations Boundary

(m) (moist) Grade Size (mm) Type distinctness A1 0 - 0.05 black (10YR2/1) heavy clay moderate 2-5 granular few, medium 6-20mm

angular chert pebbles clear

B21 0.05 - 0.30 black (10YR2/1) heavy clay moderate 10-20 sub-angular blocky

gradual

B22k 0.3 - 0.8 brownish black (10YR3/1)

heavy clay strong 10-20 lenticular few, medium 2-6mm calcareous concretions

diffuse

B23k 0.80 - 1.10 brownish black (10YR3/1)

heavy clay moderate 10-20 lenticular few, coarse 6-20mm soft calcareous segregations few, medium 2-6mm calcareous concretions

Laboratory analysis pH EC Cl


TN C:Nratio

Acid-extract P

Bicarb-P Exch. K (HCl)

Extr. S (SO4)


(dS/m) (mg/kg) % % (mg/kg) (mg/kg) (mg/kg) (mg/kg) Cu Zn Mn Fe

0-10 8.3 0.17 70 2.5 0.16 16 591 137 2.12 19 1.2 0.2 4.0 16.0

Depth pH EC Cl (1:5 soil/water

solution)

Exchangeable cations - aqueous

(cmolc/kg) ESP Ca:Mg

Base Status

Particle size Total element XRF Moist 15B

(cm) dS/m mg/kg Ca Mg Na K ECEC % CS FS SI CL P K S % R1

0 - 0.1 8.3 0.17 70 27.5 21.2 2.5 2.12 62.5 4 1.30 89 8 11 16 60 0.140 1.100 0.038 29 0.63

0.1 - 0.2 8.7 0.17 40 29.7 24.4 3.2 1.91 66.8 5 1.22 94 7 12 16 63 0.130 1.030 0.022 27 0.64

0.2 - 0.3 9.0 0.23 70 32.2 29 4.3 1.03 68.8 6 1.11 111 6 10 24 60 0.120 0.950 0.016 29 0.59

0.5 - 0.6 9.2 0.41 190 22.7 36.7 9.4 1.03 70.2 13 0.62 103 5 9 16 68 0.120 0.983 0.015 31 0.79

0.8 - 0.9 9.2 0.68 460 17.1 38.4 12.8 1.07 65.1 20 0.45 101 5 9 15 69 0.130 1.020 0.019 33 0.93

1.1 - 1.2 9.3 0.71 510 13.9 36.2 13.8 1.07 66.1 21 0.38 97 4 9 17 67 0.134 1.070 0.017 32 0.98

0% 20% 40% 60% 80% 100%

0

0.05

0.25

0.55

0.85

1.15

De

pth

(m

)

CS FS SI CL

0

0.2

0.4

0.6

0.8

1

1.2

1.4

8 8.5 9 9.5

pH

Dep

th (

m)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 0.5 1

EC (dS/m)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 200 400 600

Cl (mg/kg)

148

Burton soil formed on tephra in the Basaltic uplands

PAWC >200 mm

Site 15 Toowoomba Toowoomba sits on a plateau of deeply weathered Tertiary olivine basalts, part of the Main Range

Volcanics – the sequence that makes up this part of the Great Dividing Range. The basalt evolved

about 19‐23 mya, and underwent varying amounts of weathering during its evolution. The original

hypothesis proposed flood flow events, and there is certainly some evidence of these in the form of

valley infills perpendicular to the range. These are now present as flat‐topped ridges – the result of

topographic inversion. The basaltic uplands (which cover about 200 km on the western flank of the

GDR) are clearly comprised of many vents, and there is a great variation in flow thickness and

weathering. Pyroclastic materials are found on both the eastern and western side of the range.

Some basalt outliers are present to the east e.g Tabletop mountain, but most agree that the main

basalt thickness only extended a few kilometres east of Toowoomba. To both the north and south

the lithology varies slightly, and leucocratic trachyte is present.

The nature of the Toowoomba plateau (and the Highfields/Cabarlah surface to the north) have long

been the subject of debate, in particular whether they are lateritic, and if so, when the laterisation

occurred. Throughout Queensland (and Australia), the Tertiary was a major period of deep

weathering, and many lateritic Tertiary residuals remain in western arid landscapes. Early authors

suggested the Toowoomba plateau was laterite, but little evidence of a true lateritic profile (with

mottled and pallid zones) exists. There is no doubt it is comprised of deeply weathered basaltic

material. No stones are found anywhere in either the Toowoomba or Highfields surfaces, and the

plateaus experience about 300 mm more rainfall than areas to the east and west of the range. In

most parts of the plateaus, the weathered material is tens of metres thick. In one area (western

flank of Gowrie Creek, on the northern side of Toowoomba) there is however basaltic outcrop on a

steep slope. The weathered material thins to the western side of town, where the Red Ferrosols are

< 2m deep.

In the basaltic uplands, two main types of Red Ferrosols occur – those associated with very hard,

weathered residual basalt outcrop, and those associated with exposures of inter‐basaltic tephra and

other pyroclastic materials. Macnish et al. (1987) analysed

the nature of these “red materials” in detail. They were

originally postulated to be bole, but those authors found

they were in fact pyroclastic, and in particular, oxidised dust.

Thus the two possibilities are that the plateaus are mantled

in a deposited material (red material) which may have been

subsequently further weathered or they are deeply

weathered basalt in situ (or perhaps both).

Recent drilling by DERM, and the construction of a pilot road

tunnel through the range have provided a considerable

amount of new geological data. Clearly the deeply

weathered zone is thicker on the eastern side of

Toowoomba. At both the road tunnel, and a bore drilled at

Mt Lofty, it is evident there were two major periods of basalt

149

evolution, possibly separated by a long time period. At Mt Lofty, a 25 m thick weathered zone

overlies 24 m of weathered basalt, which in turn overlies nearly 60 m of mostly unweathered basalt

with some thin inter‐basaltic sediments. At 101 m depth, this changes back to a thick deeply

weathered red zone, that extends to 132 m. This sequence is not found across all parts of the

plateau. At Tor St, the deeply weathered basalt extends to 21 m, below which is alternating zones of

fresh and weathered basalt to at least 226 m below ground level. In the middle of the city, in the

creek valley bottom, the basalt is only about 100 m thick.

The chemistry of the different Red Ferrosols of the

eastern Downs varies substantially. All possess the

typical characteristics of Ferrosols (low fertility, low

salinity, low CEC etc), but their Ca/Mg status and

base saturation varies. On the Toowoomba

Plateau, those formed on the eastern, more deeply

weathered part of town tend to be more acidic,

and Mg dominant. Those formed on basalt in the

western side of town are neutral, grading to slightly

alkaline in the subsoil, less red and Ca dominant.

Those formed on weathered resistant basalt in the

basaltic uplands possess similar chemistry. Those

formed on inter‐basaltic tephras (the Burton soil),

while also neutral, tend to have the lowest base

saturation and are Mg dominant. The Ca dominant

Ferrosols have a higher clay activity ratio

throughout than the Mg dominant Ferrosols.

Ruthven soil, Tor St

A1

B21

B22

B23

B1

150

Site 15 Toowoomba General description: Weathered red clays formed on basaltic plateaus

Distribution: Restricted to Main Range volcanics

Parent material: Tertiary olivine basalt Location: 27.53471° S 151.92826° E Landform: Rises Vegetation: Eucalypt forest Microrelief: None Surface condition: Soft Permeability: Highly permeable Drainage: Well drained PPF: Uf6.31ASC: Haplic, Mesotrophic, Red, Ferrosol WRB: Ferralic Nitisol (Endoeutric)

Profile Description Horizon Depth Colour Texture Structure Segregations Boundary

(m) Grad

e Type Size distinctness A1 0-0.05 dusky red

(2.5YR3/2) light clay stron

g strong

granular granular

2-5mm (parting to) <2mm

- clear

B1 0.05-0.3 dark reddish brown (2.5YR3/4)

light medium clay

strong

angular blocky 2-5mm - clear

B21 0.3-0.6 reddish brown (2.5YR4/4)

light medium clay

strong strong

angular blocky angular blocky


few 2-10% fine <2mm ferromanganiferous nodules

gradual

B22 0.6-0.9 dark reddish brown (2.5YR3/4)

light medium clay

strong strong



few 2-10% medium 2-6mm ferromanganiferous nodules

gradual

B23 0.9-1.5 dusky red (10R3/4) light medium clay

strong strong



Laboratory analysis pH EC Cl NO3

(1:5 soil/water solution) TC

(Dum.) TN

(Dum.) C:N ratio

Extr. P (H2SO4)

Exch. K(HCl)

Extr. S (ICP)

Extr. B (ICP)


dS/m mg/kg mg/kg % % mg/kg meq/100g mg/kg mg/kg Cu Zn Mn Fe

0 - 0.10 5.9 0.19 33 43 6.39 0.55 11.6 24 3.2 38 1.1 4.3 9.6 262 36.2

Depth pH EC Cl NO3

(1:5 soil/water solution) TC

(Dumas)TN

(Dumas)Exchangeable cations - alcoholic

(meq/100g) Extractable cations - NH4Cl

(meq/100g) (m) dS/m mg/kg mg/kg % % Ca Mg Na K CEC Ca Mg Na K

0 - 0.10 5.9 0.19 33 43 6.39 0.55 12.0 3.8 0.4 3.0 18 16.1 4.2 0.04 2.7

0.20 - 0.30 6.3 0.08 26 23 2.21 0.16 8.5 1.9 0.4 1.2 18 9.7 2.1 0.1 1.0

0.50 - 0.60 6.2 0.08 60 14 0.83 0.07 6.1 1.5 0.4 0.4 11 6.7 1.9 0.2 0.4

0.80 - 0.90 6.3 0.05 42 7 0.40 0.04 5.8 1.8 0.4 0.3 11 5.8 2.4 0.1 0.3

1.10 - 1.20 6.3 0.06 35 21 0.29 0.03 5.8 2.3 0.4 0.3 13 5.6 2.9 0.1 0.3

1.40 - 1.50 6.1 0.21 69 85 0.30 0.04 5.8 2.1 0.5 0.7 11 6.3 3.3 0.4 0.8

Depth Base Sat ESP

Fe - citrate

sol (ICP)

Fe - oxalate (ICP)

Al - citrate

sol (ICP)

Al - oxalate (ICP)

A/F Fe ratio

Particle size Total element XRF Moistures

ADMC 15B

(m) % % % % % CS FS SI CL P K S % % R1

0 - 0.10 42 2.2 9.4 0.73 0.4 0.83 0.08 10 21 22 44 0.122 0.368 0.081 3.8 24.9 0.33

0.20 - 0.30 20 2.2 11.0 0.82 0.5 1.03 0.07 8 21 19 58 0.088 0.273 0.029 3.0 22.1 0.39

0.50 - 0.60 11 3.8 10.9 0.82 0.6 1.03 0.08 5 14 15 72 0.067 0.217 0.018 2.9 23.8 0.17

0.80 - 0.90 11 3.5 10.5 0.82 0.5 1.13 0.08 5 11 12 77 0.067 0.18 0.011 3.0 26.3 -

1.10 - 1.20 12 3 9.7 0.72 0.5 0.82 0.07 4 13 14 73 0.067 0.16 0.01 3.0 27.5 -

1.40 - 1.50 16 4.6 8.2 0.62 0.5 0.93 0.08 10 22 17 55 0.064 0.217 0.01 3.5 26.8 -

151

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

5.8 6 6.2 6.4

pH

Dep

th (

m)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0 0.1 0.2 0.3

EC (dS/m)

Dep

th (

m)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0 50 100

Cl (mg/kg)

Dep

th (

m)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0 50 100

NO3 (mg/kg)

Dep

th (

m)

0% 20% 40% 60% 80% 100%

0

0.25

0.55

0.85

1.15

1.45

Dep

th (

m)

CS FS SI CL

Basaltic Vertosols

0% 20% 40% 60% 80% 100%

0.1

0.3

0.6

0.9

1.2

Dep

th (

m)

Ca M g Na K

Red ferrosols - Ca dominant

0% 20% 40% 60% 80% 100%

0.1

0.3

0.6

0.9

1.2

De

pth

(m

)

Ca M g Na K Red ferrosols - Mg dominant

0% 20% 40% 60% 80% 100%

0.1

0.3

0.6

0.9

1.2

De

pth

(m

)

Ca M g Na K

152

References

Fensham RJ, Silcock J, Biggs AJW (2007) Vegetation‐soil relations in a highly sodic landscape,

Yelarbon, southern Queensland. Cunninghamia 10/2, 273‐284.

Harris, P. S., A. J. W. Biggs, et al., Eds. (1999). Central Darling Downs Land Management Manual,

Department of Natural Resources, Queensland.

Knight MJ, Saunders BJ, Williams RM, Hillier J (1989) Geologically induced salinity at Yelarbon,

Border Rivers area, New South Wales, Queensland. Journal of Australian Geology and Geophysics 11,

355‐361.

Maher, J. M., Ed. (1996). Understanding and managing soils in the Stanthorpe‐Rosenthal Region.

Brisbane, Queensland Department of Natural Resources.

Macnish, S.E., Koppi, A.J., Little, I.P and Schafer, B.M. (1987). The distribution, nature and origin of

some red sesquioxidic materials in south‐eastern Queensland, Australia. Geoderma 41, 1–27

Ross, D. J. and A. J. Crane (1994). Land resource assessment of the Goodar area, Queensland.,

Department of Primary Industries, Queensland.

Thwaites, R. N. and S. E. Macnish, Eds. (1991). Land management manual, Waggamba

Shire. Brisbane, Queensland Department of Primary Industries.

153

Resistivity imaging across native vegetation and irrigated Vertosols of the Condamine catchment—a snapshot of changing regolith water storage

Jenny FoleyA, Mark SilburnB and Anna GreveC

ADepartment of Environment and Resource Management, Toowoomba, QLD, Australia, Email [email protected] BDepartment of Environment and Resource Management, Toowoomba, QLD, Australia, Email [email protected] CWater Research Laboratory, UNSW, Manly Vale, NSW, Australia, Email anna‐[email protected]

Abstract Over use of one of Queensland’s most productive groundwater systems, the Condamine River

alluvium, has led to substantial depletion in groundwater levels. Most use is for irrigation (mainly

furrow), which is known to increase deep drainage below the root zone. Thus irrigation should

create greater groundwater recharge, but this is not generally detected in groundwater levels. The

enhanced deep drainage may be filling a moisture deficit in the unsaturated zone and is therefore

not yet causing greater recharge. Geophysical 2D resistivity imaging and soil coring was used to look

at changes in stored regolith water in the alluvium. Transects were imaged across naturally

vegetated landscapes (as a reference) into irrigated paddocks. All soils under native vegetation were

found to be very dry (low conductivity) even when only sparsely populated by trees. In contrast,

significant long‐term migration of water has occurred to deep within the regolith (up to 15 m) in

most irrigated paddocks. A wet (close to saturated) zone was found in the upper 6 m of soil in the

irrigated paddocks. Deeper regolith (20‐60 m) was resistive, both above and below the water table,

due to low salinities in the groundwater and coarser textures.

Key words Deep drainage, groundwater, geophysical survey, recharge, unsaturated zone

Introduction The Condamine River Alluvium and its tributaries is one of the most productive and utilized

groundwater resources in Queensland. The main system is over 150 km long, up to 30 km wide, and

over 120 m deep in places, with multiple sand and gravel aquifers in a matrix of clayey sediments. An

estimated 95 000 ML/yr are used for agriculture (90%) on Vertosols, and some urban purposes.

Groundwater levels have fallen substantially because of over use, particularly in the Central

Condamine where ~70% of all usage occurs (Murphy 2008). This decline has been particularly

evident over the last decade as the system has been in a virtual ‘recharge drought’. There is also

increasing evidence of water quality deterioration, both in shallow groundwater as a result of

increased salt leaching, and in deep systems as a result of the migration of poor quality groundwater

from adjacent areas and from bedrocks (Murphy 2008).

Irrigation alters the surface water balance. Water not used for plant growth or lost to evaporation,

drains below the root zone (deep drainage). Deep drainage of 100‐200 mm/yr has typically been

measured under furrow irrigation in a large number of sites on Vertosols and Sodosols in Australia

(Silburn and Montgomery 2004; Smith et al. 2005; Gunawardena et al. 2008). There is some

evidence, from bore monitoring, of rises in groundwater level in shallower aquifers in the alluvium

(DERM groundwater database), likely due to recharge from deep drainage, but many shallower bores

have been dry for many years. Diffuse recharge (i.e. through the soil) in the alluvium is considered to

154

be small, with the aquifers mainly recharged by river leakage (Lane 1979). Thus there is a disparity—

deep drainage below the root zone is seen to be high but recharge from this source is thought to be

low. This would be explained, in part, if deep drainage was being stored in an unsaturated zone left

dry by the previous native vegetation, creating a time lag between deep drainage and recharge.

Little is known about the moisture capacity and status of the regolith (unsaturated zone) or how this

has changed as a result of changes in the soil water balance. To examine the moisture status of the

regolith, electrical resistivity tomography and soil coring was applied to transects in the central

alluvium. Soil resistivity is related to soil water content, salinity and clay (content and type). Data

can be interpreted qualitatively with the aid of lithology from bore logs and measures of salt and clay

content. Contrasts in regolith under native vegetation and under irrigated agriculture were

examined, to assess the impacts from land use changes.

Methods Two dimensional resistivity images were taken using an ABEM SAS4000 Terrameter and LUND ES464,

across transects (200–600 m long and 60 or 21.5 m deep) in the Central Condamine alluvia, in SE

Queensland. Where possible, transects running through native vegetation and adjoining irrigated

paddocks were imaged to look at differences in water and salt due to the irrigation. Sites imaged

were:

1. Dalby, Black Vertosol—a) 400 m transect down an irrigation furrow with 2.5 m wide spacing of electrodes, measuring to 60 m depth, b) 600 m transect through native vegetation (Acacia harpophylla, A. homalophylla, Casuarina cristata, Eucalyptus populnea) into irrigated sorghum (stubble present) to 60 m

2. Pampas, Black Vertosol—480 m transect running down a furrow in irrigated paddock to 21.5 m depth

3. Brookstead, Black Vertosol—400 m transect from one irrigated field (sorghum stubble) through native vegetation (Eucalyptus camaldulensis) and into another irrigated paddock (fallow) to 60 m depth.

Soil volumetric water content was sampled with a soil coring rig. Soil samples were collected and

analysed for electrical conductivity (EC), chloride (Cl) and dispersed particle sizes, along the transects

to assess the influence of salt and clay content on resistivity. Two dimensional resistivity images were

inverted using the RES2DINV software. Data was converted to conductivity (reciprocal of resistivity)

with high conductivity generally indicating high water contents.

Results and discussion All the images are deeper than—or close to, in the case of Pampas—groundwater levels. The

saturated zone and the deeper unsaturated zone are generally resistive, due to the low salinity of the

groundwater (Pampas and Brookstead 400, Dalby 1200 μS/cm) and sands and sometimes gravels

interbedded in the clays. Thus the less resistive deeper material at the Dalby site (Fig. 1) is consistent

with the higher groundwater salinity.

155

Figure 1. Dalby transect L to R, furrow irrigated paddock, head ditch (L) to past mid point in paddock.

Figure 2. Pampas transect: L to R, furrow irrigated paddock, head ditch (L) to past mid point in paddock.

The first two transects were measured down typical irrigation furrows at Dalby and Pampas. Images

show highly conductive zones of soil (very wet, with medium salinity typical of soils in the region),

along the entire length of the transects in the upper 6 m of the profile (Figures 1, 2). Soil volumetric

water sampling revealed, on average, these areas had >550 mm of water above that stored under

native vegetation and up to 250 mm above drained upper limit in the top 6 m of soil. This is ‘new’

water added by irrigation.

Water in this near‐saturated layer is not static. It is draining into the deeper regolith at a rate

proportional to the hydraulic conductivity of the deeper clay and sand layers. The soil profile changes

at around 5–6 m, with increasing sandy, sandy clay and occasionally gravel layers. These often create

confining zones. Once saturated clay layers become interspersed with sand layers, the soil will

remain saturated in the clay but not in the sand, due to hydraulic relationships. Water will continue

to move deeper in the regolith, but these zones will not show up on the image as having a high

conductivity due to the increasing presence of unsaturated sand. Also, salinity will be a mixture of

that in the leachate (i.e. higher, due to salt from the soil) and the lower salinity in groundwater

discussed above. Groundwater levels were at 10–20 m before 1965, so some of the current

unsaturated zone once held groundwater of low salinity.

156

Native veg Sorghum stubble Fallow - irrigated

Figure 3. Dalby transect: L to R, native vegetation into sorghum stubble (irrigated).

0

1

2

3

4

5

6

0.20 0.40 0.60 0.8Soil moisture (v/v)

Dep

th (

m)

Native veIrr-130mIrr-260mIrr-550mTP

a)

0

1

2

3

4

5

6

0.0 0.4 0.8 1.2EC dS/m

Dep

th (

m)

Native vegIrr-130mIrr-260mIrr-550m

b)

0

1

2

3

4

5

6

20 40 60 80Clay %

Dep

th (

m)

Native vegIrr-130mIrr-260m Irr-260m

c)

Figure 4. Dalby transect a) soil volumetric water contents, b) EC and c) clay contents, taken in native

vegetation and at 130, 260 and 550 m (refers to distances along transect in Figure 3).

The image at Dalby (Figure 3) shows a clear increase in conductivity in the upper layers at 120 m,

where native vegetation ends and the irrigated paddock starts. Soil under native vegetation had

lower conductivity, half that in the irrigated paddock, and was dry (Figure 4a). Soil was extremely wet

under irrigation to the depth measured (Figure 4a). Water contents were close to total porosity (TP);

the soil was near‐saturated and had little air content. EC profiles show a salt bulge higher in the

irrigated paddock, consistent with salt added in irrigation water (Figure 4b). However by 3 m depth,

EC was reasonably uniform along the entire transect. Similarly, % clay was consistent along the

transect to 4 m (Figure 4c). Deeper that this, some sandy layers begin to emerge, creating variability

in particle size analysis. Overall, these results indicate changes in conductivity in the upper profile are

predominately due to differences in soil water. The depth of the highly conductive zone is shallower

at the tail drain (near the native vegetation) than towards the head ditch, consistent with less

drainage occurring along furrow irrigated fields (Gunawardena et al. 2008).

As with the Dalby transect, a clear delineation is seen when moving from irrigation to native

vegetation at Brookstead (Figure 5). The wet zone extends considerably further down (to 15 m),

under irrigation. Soil EC and clay contents are very uniform along the transect (Figures 6b, 6c), and so

it can be assumed that conductivity changes along the transect (at shallow depths) are due to

changes in soil water.

Conclusion 2‐D resistivity imaging and soil coring showed that irrigated fields in the Condamine alluvium were

consistently near‐saturated in the upper regolith to depths of about 10 m, whereas under native

157

vegetation the regolith was dry. Thus considerable deep drainage from irrigation has been stored in

regolith previously kept dry by native vegetation, preventing it from contributing to recharge. It is

not possible to determine from resistivity imaging whether deeper layers (e.g. >15m) are also wet

because they are resistive in the unsaturated zone and below the water table, due to low salinity of

the groundwater. Deeper coring is required to determine the moisture status and confirm the

salinity of these deeper materials.

Native veg

Sorghum stubble - irrigated Fallow - irrigated

Figure 5. Brookstead transect: L to R, sorghum stubble (irrigated) into native vegetation, into fallow irrigated.

0

1

2

3

4

0.20 0.40 0.60 0.8Soil moisture (v/v)

Dep

th (

m)

Nat veg206 m223 m243 mTPDUL

a)

0

1

2

3

4

0 0.2 0.4 0.6 0.8 1EC dS/m

Dep

th (

m)

Native vegGrassFurrows

b)

0

1

2

3

4

20 40 60 80Clay %

Dep

th (

m)

Native vegGrassFurrows

c)

Figure 6. Brookstead transect a) soil volumetric water contents, b) EC and c) clay contents taken at 196 m (native veg), 203 m (grassed) 206 m (furrow start), and 223 and 243 m (refers to distances along transect in Figure 5).

Acknowledgments Water Research Laboratory (UNSW) for use of resistivity imaging equipment, technical expertise and

image analysis. Funds were provided by Cotton Catchment Communities CRC Project 2.1.02 and

Condamine Alliance. Kind thanks to Denis Orange, Maria Harris, Ralph de Voil and Tony King for field

and laboratory assistance; and to farm owners and managers for access to farm sites.

References Lane WB (1979) Progress report on Condamine underground investigation to December 1978. QWRC

Groundwater Branch Report, June 1979. (Queensland Water Resources Commission). Gunawardena TA, McGarry D, Gardner EA, Stirzaker R (2008) Managing Deep Drainage for Improved

WUE: Solute Monitoring and Ground Water Response in the Irrigated Landscape. In “Proceedings of the 14th Australian Cotton Conference.” 12 – 14 August 2008, Broadbeach, Australia.

Murphy G (2008) Management of Groundwater – Condamine River and tributary alluvium: Information paper for groundwater licensees and users (Central Condamine River Alluvium). (Department of Natural Resources and Water: Brisbane).

158

Silburn DM, Montgomery J (2004) Deep drainage under irrigated cotton in Australia – A review. WATERpak a guide for irrigation management in cotton. Section 2.4. pp. 29–40. (Cotton Research and Development Corporation/Australian Cotton Cooperative Research Centre: Narrabri).

Smith RJ, Raine SR, Minkevich J (2005) Irrigation application efficiency and deep drainage potential under surface irrigated cotton. Agricultural Water Management 71, 117–130.

Extract from a report by T. Gunawardena and D. McGarry (2007).

The Pampas site is part of the “Deep Drainage under Furrow Irrigation – Surface and Groundwater

Implications” project (Project: 1.02.04 of the CCC‐CRC and CRDC).

‐ Three drainage lysimeters were installed (13‐15 July, 2004) and an automated weather station in

October 2004. The lysimeters were spaced equidistant along the length of the field and 50 metres

into the field (perpendicular to the edge).

‐ One irrigated crop (cotton 2004‐5) and one rainfed crop (sorghum 2005‐6) have been grown on this site with bare fallow between.

A maximum deep drainage (DD) of just under 1 ML/ha was measured with the lysimeters during the 2004‐5 cotton season at the head ditch end of the field, 0.5 ML/ha of DD at the mid, and almost zero DD at the tail.

Zero DD was measured at all other times, i.e. during the dryland sorghum crop and the bare fallow periods, despite up to 400 mm of rain during those times.

Water balance analysis (the SIRMOD/ET model) indicated the same trend in DD at the site; that DD was greatest at the head location and decreased almost 25% at the mid and was zero at the tail. The SIRMOD ET analysis predicted approximately x2 the amount of DD at both the head and mid locations, relative to the lysimeter data. (2.1 ML vs 1 ML at the head, and 1.6 ML vs 0.4 ML at the mid, for SIRMOD / ET vs lysimeter, respectively).

SaLF analysis (based on inherent soil properties, rainfall and irrigation amounts) also predicted more DD at the head ditch location, and equal amounts at both mid and tail. However, the values were more than 10‐fold the value of the lysimeter data. SaLF analysis predicts these soils are prone to DD, particularly at the head ditch end where there is less clay, more sand and lower CEC levels. SaLF takes no account of ET and temperatures during season, or crop growth (or type); all of which will have marked impact on DD amounts and in‐field variability.

The very low soil EC values at the site may show historic, large flushing episodes (through‐water movement). This seems to correspond well with the SaLF results but not the lysimeter data collected to date.

The EC and chloride values of the DD leachate waters are not regarded as “of concern”. The EC values are marginal in terms of what is considered “optimum” for cotton growth and are far lower than many of the other lysimeter sites.

159

The lysimeters should be maintained to measure DD in future irrigated irrigation seasons, with more “typical” (non drought) during season weather patterns and irrigation events / volumes.

Figure 14 Lysimeter installation design

The lysimeters are buried at 150 cm from the soil surface, 50 metres rectangularly into the field from

the lysimeter trap, at each the head, mid and tail locations.

09/0

4

0/0

4

1/0

4

2/0

4

01/0

5

02/0

5

03/0

5

04/0

5

05/0

5

06/0

5

Dee

p dr

aina

ge (

mm

)

0

20

40

60

80

100

120

140

160R

ainf

all (

mm

)

0

100

200

300

400

500

600HeadMidTailCum RF

Figure 15 Cumulative deep drainage recorded (electronic tips) from the Pampas site during the 2004‐5 cotton season. The actual volumes of water collected for each of the head, mid and tail locations were 71, 106 and 62 mm, respectively. Arrows show irrigations. The cumulative rainfall is plotted as a dashed line.

160


Landform Toowoomba is located on the escarpment of the Great Dividing Range. The slope of the landscape is about 5°.


The geology of the area is dominated by basalt flows and associated rocks from the late Tertiary. Subsequent denudation in the Quaternary resulted in westward migration of the Great Dividing Range and the development of an east-facing escarpment.

Drainage class Well drained, with a low run‐on rate and run‐off rate.

Surface condition:

A stable, granular, organic‐rich surface. The soil has low erodibility and is regarded as a slight erosion hazard.

Site disturbance

Completely cleared and currently under pasture, though has been cultivated in the past. Surrounding areas are sealed and urbanised.

Native vegetation

Eucalyptus spp.

Climate The area has a temperate climate with no dry season. The annual average rainfall is 954 mm. Toowoomba experiences distinctly cool winters with warm, wet summers. The mean January maximum temperature is 27.6°C and the mean July minimum temperature is 5.3°C.

SB Profile 15: Toowoomba, Queensland

161

Queensland

New South Wales

162

2. Description of soil profile A red clay soil that has formed as a result of the weathering of basalt from the Main Range Volcanics. Although it is not texturally evident, due to the mid‐slope position of the site it is likely that upslope colluvium has contributed to the development of the soil.

Soil morphology

LC= light clay, LMC= light medium clay, MC= medium clay

Australian Soil Classification: Red Ferrosol (FE AA)

World Reference Base: Lixic Nitisol (Manganiferric, Humic, Rhodic) OR Ferrallic Lixic Nitisol (Manganiferric, Humic, Rhodic)

Soil Taxonomy: Typic Rhodudalf (Very Fine, Kaolinitic, Thermic)


Depth (m)


Texturegrade


Coarse fragments

Segregations

A A 0‐0.1 Clear Even 2.5YR 2.5/3

Dark reddish brown2.5YR 3/3

Dark reddish brownLC Weak Granular 2‐5 ‐ ‐

B1 Bw1 0.1‐0.25 Gradual Even 2.5YR 3/2 Dusky red

2.5YR 3/2 Dusky red

LMC Strong Angular blocky

2‐5 ‐

B21 Bw2 0.25‐0.6 Gradual Even 2.5YR 2.5/4

Dark reddish brown2.5YR ¾

Dark reddish brownLMC Strong

Angular blocky

5‐10 ‐

B22 Bt 0.6‐0.8 Diffuse Even 2.5YR 3/6 Dark red

2.5YR 3/6 Dark red


2‐5 ‐

B23 Bw3 0.8‐1.15 Diffuse Even 2.5YR 3/6 Dark red

2.5YR 3/6 Dark red

LMC MediumAngular blocky

2‐5, 10‐20

Weathered basalt

<2% medium

(2‐6 mm) Fe

nodules

A1

B22

B23

B1

A1

Bw2

Bt

Bw3

B21

Bw1

163

3. Soil mineralogy

Kaolinite and traces of illite are observed in the oriented diffraction patterns of the clay fractions of

the profile. In addition to the phyllosilicates, the random powder diffraction patterns identify the

presence of hematite and traces of quartz in the clay fraction of the profile.

X‐ray diffraction patterns of the oriented clay fraction of A horizon soil after various pre‐

treatments; Mg saturated and air‐dried (‐‐‐‐‐‐), Mg saturated and ethylene glycolated (‐‐‐‐‐‐), and K

saturated and heated at 550°C (‐‐‐‐‐‐).

Thin section

This PPL image of the A1 horizon shows a

very strong granular microstructure and

the coating of all grains/aggregates with

iron oxides.

164


The pH values for this profile are moderately acidic to neutral.

The EC values range from low to medium within the profile.

The organic carbon and total nitrogen contents are high, especially in the top 50‐60 cm of the profile.

The cation exchange capacity (CEC) values for the profile are low to moderate.

The profile has a very high free Fe content (8.7‐10.8%) in all horizons.



Horizon pH

(1:5 H2O) EC

(dS/m) Total C (%)

Total N (%)

C:N ratio

NO‐3‐N


PBI‐Colwell

SO4 (mg/kg)

Avail. K (mg/kg)

Cl (mg/kg)

A 5.87 0.42 6.24 0.56 11 220 40 140 30 1100 32

B1 6.26 0.21 5.24 0.40 13 68 10 ‐ ‐ 840 32

B21 6.44 0.12 2.14 0.17 15 38 5 ‐ ‐ 530 28

B22 6.78 0.44 0.50 0.05 10 8 6 ‐ ‐ 78 26

B23 6.48 0.45 0.27 0.03 9 7 6 ‐ ‐ 71 22


CEC Ca Mg K Na Zn Cu Fe Mn Fe Al Fe Al

A 198 130 40 28 0.4 11 3 66 260 8.68 0.43 0.3 0.4

B1 174 120 32 21 0.5 ‐ ‐ ‐ ‐ 10.80 0.55 0.4 0.5

B21 105 75 16 14 0.4 ‐ ‐ ‐ ‐ 9.74 0.55 0.4 0.5

B22 78 55 20 2 1.1 ‐ ‐ ‐ ‐ 9.94 0.66 0.4 0.5

B23 76 51 23 2 0.9 ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐

A1 A1 A1 A1

B21 B21 B21 B21

B22 B22 B22 B22

B23 B23 B23 B23

B1 B1 B1 B1


165

5. Soil physical characteristics

The particle size analysis for this soil reflects a high to very high clay percentage throughout the profile.

The bulk density is considered to be very low‐ to low.

The water content at permanent wilting point slightly increases down the profile.

The conductivity declines down within the profile.

The penetration resistance indicates medium to very dense consolidation.



Clay (< 2 μm)

Silt (2‐20 μm)

Fine sand (20‐200 μm)

Coarse sand (200‐2000 μm)

Bulk density (g/cm

3) 10 kPa

1500 kPa (PWP)

0 kPa (FC)


A 47 20 24 9 0.62 0.43 0.20 0.58 0.50

B1 43 28 19 10 0.91 0.47 0.25 0.56 3.57

B21 50 28 16 6 1.18 0.47 0.31 0.53 9.12

B22 73 12 11 4 ‐ ‐ ‐ ‐ ‐

B23 47 19 25 9 ‐ ‐ ‐ ‐ ‐

International system PSA (%)

Horizon Silt

(2‐50 µm) Sand

(50‐2000 µm)

A 34 19

B1 45 11

B21 42 8

B22 14 13

B23 34 19

B1 B1 B1 B1

A

B21

B21

B22

B23

A A A

A

B1

B21 B21

B21

166

Day 6

Toowoomba to Brisbane

Presenters:

Ben Harms



Bernie Powell



167


Landform Situated in the Upper Brisbane River catchment. Parts of the region lay in the foothills of the Great Dividing Range and the Conondale Range. Undulating hills are the dominant landscape form within the region, exhibiting slopes of 4‐15%.


Located on the Esk formation, which is derived from sediments formed by uplifting Palaeozoic mountainous areas. Granite is the most dominant parent material in the region, causing soils to be generally nutrient poor.

Drainage class Rapidly drained, with a high run‐on rate and medium run‐off rate.

Surface condition

Sandy and gritty. The soil is moderately erodible, and there is a significant erosion hazard at the site due to past quarrying activities.

Site disturbance

The region is dominated by livestock grazing, intensive agriculture and native bushland. Rural residential use and other activities such as quarrying also take place within the region. This profile has been highly disturbed by quarrying activities.

Native vegetation

The dominant vegetation consists of mostly native woodland with grass understorey. The woodland is comprised of mid‐high to tall Eucalyptus tereticornis, Eucalyptus crebra, Corymbia tesselaris, Angophora floribunda and Angophora leiocarpa.

Climate

Sub‐tropical climate with intense storms mostly during the summer. The annual average rainfall is 860 mm. Hot summer days and warm summer nights are characteristic of the area, with an average daily maximum temperature (in summer) of 30.4°C. Winter days are warm with cold nights. The average daily maximum temperature in winter is 19.3°C.

Profile 16: Toogoolawah, Queensland

168

0 1 km

Queensland

New South Wales

169

2. Description of soil profile A free‐draining Tenosol of coarse sandy nature that is derived from granite parent material.

Soil morphology

CS= Clayey sand, LS= Loamy sand

Australian Soil Classification: Paralithic Orthic Tenosol (TE DS)

World Reference Base: Cutanic Lixisol (Manganiferric?, Hypereutric?, Arenic, Chromic)

Soil Taxonomy: Cemented Paleudalf (Sandy, Mixed, Semi‐active, Thermic)



Texture grade


Segregations

A₁ A1 0‐0.1 Clear Even 10YR 3/4

Dark yellowish brown CS Massive ‐ ‐ ‐

A3 A2 0.1‐0.3 Gradual Even 10YR 4/6

Dark yellowish brown LS Massive ‐ ‐ ‐

B₂₁ Bw1 0.3‐0.7 Gradual Even 7.5YR 5/6

Strong brown LS Massive ‐ ‐

<2% Mn soft nodules (<5mm)

B₂₂ Bw2 0.7‐1.05 Gradual Even 7.5YR 6/6

Reddish yellow LS Massive ‐ ‐ ‐

B₂₃ Bw3 1.05‐1.35 ‐ ‐ 7.5YR 6/4 Light brown

CS Weak Sub‐angular

blocky 10‐20 ‐

A₁

B₂₁

B₂₃

B₂₂

A3

A1

A2

Bw1

Bw2

Bw3

170

3. Soil mineralogy

X‐ray diffraction patterns of basally oriented clays show the presence of kaolinite, small

amounts of illite and an interstratified swelling mineral. The proportion of the interstratified

swelling mineral increases with depth. In addition to the phyllosilicates, the random powder

diffraction patterns identified quartz and feldspar (plagioclase) in the soil clay fractions.




swelling mineral.

Thin sections

The left image (PPL) shows a degree of clay bridging between sand‐sized grains of the B23 horizon,

along with some fine‐grained iron oxide. The right image, showing the same view in XPL, reinforces

the patchiness of the clay bridging.

171


The pH values for this soil profile range from neutral to mildly alkaline (6.9‐7.7).

There are low EC values in all horizons of the profile.

Nitrogen levels are high in the A1 horizon and then decline dramatically in the underlying horizons, which are classed as very low for N.

The organic carbon contents are considered low to moderate in the surface horizon and extremely low in all other horizons.

The cation exchange capacity (CEC) is very low throughout the entire profile. Chemical properties of soil profile


Horizon pH

(1:5 H2O) EC


Total N (%)

C:N ratio

NO₃‐N (mg/kg)

Colwell P (mg/kg)

PBI‐Colwell

SO4 (mg/kg)

Avail. K (mg/kg)

Cl (mg/kg)

A₁ 6.88 0.09 1.10 0.31 3.54 49 10 23 4.10 130 10

A3 7.67 0.02 0.32 0.07 4.57 2 6 ‐ ‐ 35 10

B₂₁ 7.26 0.02 0.15 0.04 3.75 1 5 ‐ ‐ 46 10

B₂₂ 6.71 0.06 0.15 0.02 7.50 1 5 ‐ ‐ 50 50

B₂₃ 7.08 0.03 0.15 0.02 7.50 1 10 ‐ ‐ 43 22

Cation exchange properties mmolc/kg DTPA extractable micronutrient status

(mg/kg) DCB (%)

Horizon


A₁ 34 24 6 1 4 1 0.63 0.24 20 39 0.4 0.03

A3 24 14 5 2 2 1 ‐ ‐ ‐ ‐ 0.3 0.02

B₂₁ 22 7 6 2 3 1 ‐ ‐ ‐ ‐ 0.4 0.03

B₂₂ 22 5 7 3 3 2 ‐ ‐ ‐ ‐ 0.4 0.02

B₂₃ 23 8 9 2 3 ‐ ‐ ‐ ‐ ‐ 0.4 0.02

A1 A1 A1

A3 A3 A3 A3

B21 B21 B21 B21

B22 B22 B22 B22

B23 B23 B23 B23

A1

CEC (mmolc/kg)

172


The PSA for the profile reflects a very high sand content and low silt and clay content. There is not much variation throughout the profile.

The bulk density slightly increases down the profile, being rated as low to moderate. The penetration resistance is very low in the upper 2 horizons, whilst it is considered to be

moderate in horizon B21 and high in the bottom 2 horizons.



Horizon Clay

(<2 µm) Silt

(2‐50 µm) Fine sand (50‐200 µm)


Bulk density (g/cm

3) 10 kPa

1500 kPa (PWP)

0 kPa (FC)


A₁ 7.9 18.3 13.8 60.1 1.20 0.33 0.11 0.40 0.08

A3 6.8 14.8 12.8 65.6 1.27 0.29 0.09 0.42 0.07

B₂₁ 9.9 17.3 16.6 56.3 1.28 0.32 0.11 0.40 1.6

B₂₂ 7.3 16.7 15.7 60.3 1.32 ‐ ‐ ‐ 1.5

B₂₃ 9.1 15.9 13.4 61.6 1.37 ‐ ‐ ‐ 1.5


Horizon Silt

(2‐50 µm) Sand (50‐2000 µm)

A₁ 38.3 53.8

A3 32.3 61.0

B₂₁ 36.7 53.4

B₂₂ 35.6 57.1

B₂₃ 34.3 56.6

A1 A1 A1 A1

A3 A3 A3 A3

B22

B21 B21 B21

B22 B22 B22

B21

B23 B23 B23 B23

A1 A1

A3 A3

B21 B21

B22 B22

B23 B23

173


Landform The landform of the immediate area is gently undulating hills to plains (0-5% slope), with

imperfectly or moderately drained soils.


Wamuran is situated on Jurassic Landsborough Sandstone, on the North D'Aguilar Block. Sand and clay sediments, with some basaltic lava flows of the coastline have been folded and crumpled into the North D'Aguilar Block. The North D'Aguilar Block has also been intruded by granite-type rocks in the late Permian to mid-Triassic.

Drainage class Moderately drained, with a low run‐on rate and medium run‐off rate.

Surface condition:

Soft and friable. The soil has low erodibility and as the area has only a slight erosion hazard.

Site disturbance

After the First World War, returned soldiers were permitted to settle this land for agricultural use, although it was not understood that the soils were of low fertility. Today, the Wamuran area specialises in dryland horticulture, predominantly growing strawberries, pineapples, and bananas.

Native vegetation

Land has been cleared, although there are some native dry sclerophyll forests present in the surrounding areas. Vegetation species include Scribbly Gum, Spotted Gum, Ironbark (Eucalyptus spp.), Bloodwood (Corymbia spp.) and Paperbarks (Melaleuca spp.)

Climate This area has a subtropical climate with cool winters and warm wet summers. Annual average rainfall is approximately 1380 mm. Summer temperatures have an average maximum of 30.5°C, while the average winter maximum temperature is 20.2°C.

Profile 17: Wamuran, Queensland

174

Queensland

New South Wales

0 1 km

175

2. Description of soil profile A moderately drained Yellow Chromosol, with slightly acidic pH levels.

Soil morphology

RF= red, faint; RD= Red, dark; YD= Yellow, dark; CS= clayey sand, SL= sandy loam, LS= loamy sand, MC= medium clay

Australian Soil Classification: Yellow Chromosol (CH AC)

World Reference Base: Stagnic Cutanic Lixisol (Albic, Ferric, Abruptic, Ruptic, Humic, Clayic)

Soil Taxonomy: Oxyaquic Kanhapludalf (Fine, Kaolinitic, Thermic)



Mottles Texturegrade


A₁ A1 0‐0.2 abrupt wavy 10YR 4/2

Dark grayish brown10YR 3/2

Very dark grayish brown‐ CS Moderate Crumb 2‐5

A₂ E 0.2‐0.35 gradual wavy 10YR 6/2

Light grayish brown10YR 3/2

Very dark greyish brown‐ SL Massive ‐ ‐

A3 Bt1 0.35‐0.47 diffuse even 10YR 6/6

Brownish yellow 10YR 6/6

Brownish yellow ~20% R, F LS Massive ‐ ‐

B21 Bt2 0.47‐0.6 diffuse even 10YR 6/8

Brownish yellow 10YR 5/8

Yellowish brown ~30% R, D MC Weak Blocky 20‐50

B22 Bt3 0.6‐0.85 ‐ ‐ 10YR 7/8 Yellow

10YR 5/8 Yellowish brown

~50% Y, D MC Weak Blocky 20‐50

A

A3

B22

A2

A

E

Bt1

Bt2 B21

Bt3

176

3. Soil mineralogy

X‐ray diffraction patterns of basally oriented clays show the presence of kaolinite, inhibited

vermiculite and traces of illite in the clay fraction of the soil. In addition to the phyllosilicates,

the random powder diffraction patterns show quartz (trace amounts in B22 horizon),

anatase, goethite and hematite in the soil clay fractions.

X‐ray diffraction patterns of the oriented clay fraction of A1 horizon soil after various pre‐



Thin sections

The left image (PPL) shows some very prominent argillans in the B22 horizon, while the right image

(XPL) shows oriented clay coating grains and occupying long, continuous pores in the B22 horizon.

These features attest to the importance of illuviation in this profile.

177


The pH values for this profile are strongly acidic to slightly acidic (5.38‐6.24) and there is no consistent pattern in the soil pH values within the profile.

Very low EC values throughout the soil profile.

Organic carbon and total nitrogen contents are high in the top two horizons and low in rest of the horizons.

The cation exchange capacity (CEC) ranges from very low to low through the profile. There is a significant amount of free iron in the B horizons.



Horizon pH (1:5 H2O)

EC (dS/m)

Organic C (%)

Total N (%)

C:N ratio

NO₃‐N (mg/kg)

Colwell P (mg/kg)

PBI‐Colwell

SO4 (mg/kg)

Avail. K (mg/kg)

Cl (mg/kg)

A₁ 5.89 0.02 4.99 0.29 17.2 4.9 6 87 2.9 46 10

A2 6.04 0.03 3.81 0.17 22.4 1 5 ‐ ‐ 20 10

A3 5.38 0.01 0.49 0.02 24.5 1 5 ‐ ‐ 21 10

B21 6.26 0.02 0.40 0.03 13.3 1 5 ‐ ‐ 55 10

B22 6.00 0.02 0.23 0.02 11.5 1 5 ‐ ‐ 75 15


CEC Ca Mg K Na Al Zn Cu Fe Mn Fe Al Fe Al

A₁ 82.5 66.5 6.3 1.2 0.4 8.1 4 1.4 0.12 81 0.75 0.15 0.1 0.1

A2 17.3 10.0 2.6 0.5 0.2 4.0 2 ‐ ‐ ‐ 0.46 0.12 0.1 0.1

A3 14.8 1.0 12.0 0.5 0.3 1.0 3 ‐ ‐ ‐ 1.15 0.14 <0.1 <0.1

B21 45.0 1.5 40.0 1.4 1.1 1.0 1 ‐ ‐ ‐ 3.10 0.45 <0.1 0.1

B22 75.6 4.7 66.0 1.9 2.0 1.0 1 ‐ ‐ ‐ 5.20 0.60 0.1 0.1


A1 A1 A1 A1

A2 A2 A2 A2

A3 A3 A3 A3

B21 B21 B21 B21

B22 B22 B22

B22

178


The PSA reflects a very high sand percentage in the A horizons, while clay content increases significantly in the B horizons.

There is a significant increase in the soil bulk density in the A3 horizon of the profile.

Hydraulic conductivity and field capacity water content declines down the profile. The penetration resistance is loose (topsoil) to dense (subsoil).



Horizon Clay

(<2 µm) Silt

(2‐20 µm) Fine sand (20‐200 µm)


Bulk density (g/cm

3) 10 kPa

1500 kPa (PWP)

0 kPa (FC)


A₁ 10.4 5.2 27.5 56.9 1.24 0.33 0.11 0.40 0.08

A2 9.9 11.5 26.8 51.8 1.13 0.29 0.09 0.42 0.07

A3 16.7 6.7 27.0 49.7 1.75 0.32 0.11 0.40 1.6

B21 44.0 6.8 13.6 35.6 ‐ ‐ ‐ ‐ 1.5

B22 65.9 6.6 8.8 18.7 ‐ ‐ ‐ ‐ 1.5

Estimates USDA PSA (%)

Horizon Silt

(2‐50 µm) Sand (50‐2000 µm)

A₁ 14.1 75.5

A2 26.6 63.6

A3 17.8 65.5

B21 16.4 39.6

B22 9.6 24.5

A1

A2

A3

B21

B22

A1 A1 A1

A2 A2 A2

A3 A3 A3

A3

A1

A2

B21

179

Appendix

180

Laboratory Methods and interpretations

All laboratory analysis was done < 2 mm soil fraction and values are expressed on an oven dry soil weight basis.

(i) Soil pH and electrical conductivity (EC): Soil pH and EC were measured in 1:5 soil /water extract after one

hour end‐over‐end shaking and left for 20 min for the soil to settle.

General interpretation of soil pH in water (1:5) (Bruce and Rayment, 1982).

pH Ratings

>9.0 Very strongly alkaline 9.0‐8.5 Strongly alkaline 8.4‐7.9 Moderately alkaline 7.8‐7.4 Mildly alkaline 7.3‐6.6 Neutral 6.5‐6.1 Slightly acid 6.0‐5.6 Moderately acid 5.5‐5.1 Strongly acid 5.0‐4.5 Very strongly acid <4.5 Extremely acid

US Salinity Laboratory soil salinity criteria for the interpretation of ECe† (Hazelton and Murphy, 2007).

Status ECe (dS/m) Comment

Non‐saline <2 Salinity effects negligible Slightly saline 2‐4 Yields of sensitive crops reduced

Moderately saline 4‐8 Yields of many crops reduced Very saline 8‐16 Only tolerant crops yield satisfactorily Highly saline >16

Very few crops give satisfactory yields

† ECe = electrical conductivity of saturation extract.

(ii) Total carbon and nitrogen were determined using an Elementar Vario MAX CNS analyzer. The procedure

involved combustion of a small mass (~500 mg) of finely ground (<50 μm) soil sample at 900°C. The combustion

process converts soil carbon and nitrogen into N2 and CO2 gases, respectively. The evolved gases are analysed

sequentially using a thermal detector. A series of reference compounds or soil standards are analysed to

calibrate the instrument prior to the analysis of soil analysis. Soil samples containing calcium carbonate were

treated by equilibrating with 1 M HCl overnight to remove carbonates, and carbonated free sample should be

analysed to determine the organic carbon in such soils.

General rating of total nitrogen content of soil (Bruce and Rayment, 1982).

Total nitrogen (%) Rating

<0.05 Very small 0.05‐0.15 Small 0.15‐0.25 Medium 0.25‐0.50 Large >0.50 Very large

181

General rating of the soil carbon/nitrogen (C:N) ratio (Metson, 1961)

C:N ratio Rating

<8 Very small 8‐10 Small 10‐15 Medium 15‐25 Large >25 Very large

A C:N ratio of 10‐12 is normal for an arable soil.

Nitrate nitrogen: Nitrate extracted by 1:5 soil/water solution, shaking for one hour, centrifuged, filtered and

measured by automated colorimetric analysis.

General rating of nitrate nitrogen

Nitrate (mg/kg) Rating

<5 Very low 5‐10 Low 10‐15 Moderate 15‐25 Satisfactory 25‐100 >100

High Very high

Colwell phosphorus: Phosphorus extraction by 1:100 soil/0.5 M sodium bicarbonate (pH 8.5) solution, end‐

over‐end shaking for 16 hours, centrifuged, filtered and measured by automated colorimetric analysis.

General rating of Colwell phosphorus

Colwell P (mg/kg) Rating

<5 Very low 5‐10 Low 10‐15 Moderate 15‐40 Satisfactory 40‐100 >100

High Very high

Phosphorus Buffer Index (PBI): Phosphorus adsorption is determined by equilibrating 1:10 soil/ 0.01 M CaCl2

solution and 100 mg/L phosphorus, for 17 hours, centrifuged, filtered and measured by ICP‐AES or colorimetric

method.

PBI (ColP) is calculated as: PBI+ColP = [Ps + Colwell‐P ] / c0.41

where Ps is the amount of freshly sorbed P in the soil (mg P/kg), c is the equilibrium solution P concentration

(mg/L) and Colwell is the Colwell‐extractable P in the soil (mg P/kg).

General rating of Colwell phosphorus

PBI Rating

<35 Very low 35‐70 Low 70‐140 Moderate 140‐280 High >280 Very high

182

Phosphorus Buffer Index (PBI): Phosphorus adsorption is determined by equilibrating 1:10 soil/ 0.01 M CaCl2

solution and 100 mg/L phosphorus, for 17 hours, centrifuged, filtered and measured by ICP‐AES or colorimetric

method.

Available potassium (Colwell K): Potassium extraction by 1:100 soil/0.5M sodium bicarbonate (pH 8.5)

solution, end‐over‐end shaking for 16 hours, centrifuged, filtered and measured by AAS.

General rating of available potassium

K (mg/kg) Rating

<35 Very low 35‐70 Low 70‐140 Moderate 140‐280 High >280 Very high

Chloride: Chloride extracted by 1:5 soil/water solution, shaking for one hour, centrifuged, filtered and

measured by automated colorimetric analysis.

General rating of chloride

Cl (mg/kg) Rating

<250 Low 250‐450 Moderate 450‐600 High >600 Very high

Exchangeable cations: Exchangeable cations (Ca, Mg, Na, and K) extracted by 1:10 soil/ammonium acetate (pH

7.0) solution, end‐over‐end for half hour, centrifuged, filtered and measured by ICP‐AES.

Exchangeable aluminium: Aluminium extraction by 1:10 soil/1M KCl solution, shaking for one hour,

centrifuged, filtered and measured by AAS.

Cation exchange capacity (CEC): For variable charge acidic soil by silver thiourea method, for alkaline soil with

permanent charge by summing up the exchangeable base cations.

Cation exchange capacity ratings for Australian soils (Metson, 1961).

Rating CEC (mmolc kg‐1)

Very low <60

Low 60‐120

Moderate 120‐250

High 250‐400

Very high >400

Trace Elements (DTPA): Zinc, copper, iron, manganese trace element extraction by 1:2 soil/DTPA solution

triethanolamine/CaCl2 two‐hour shaking, centrifuged, filtered and measured by ICP‐AES.

183

Critical ranges for DTPA extractable micronutrients in soils (Sims and Johnson, 1991)

Element Critical range (mg/kg)

Cu 0.3‐0.6

Fe 4.5‐5.0

Mn 1‐5

Zn 0.3‐1.4

Citrate/dithionite extractable iron and aluminium: Iron and Al extracted by shaking 1 g soil with 50 ml 22%

sodium citrate and 1 g dithionite on an end‐over‐end shaker for 16 h, centrifuged, filtered and measured by

ICP‐AES.

Oxalate extractable iron and aluminium: Iron and Al extracted by shaking 1 g soil with 100 ml acid oxalate

solution in the dark on an end‐over‐end shaker for 4 h, centrifuged, filtered and measured by ICP‐AES.

References

Bruce, R.C. and Rayment, G.E. (1982). Analytical Methods and Interpretation Used by the Agricultural

Chemistry Branch for Soil and Land Use Surveys. Bulletin QB82004. Queensland Department of

Primary Industries.

Hazelton, Pam and Murphy, Brian (2007). Interpreting Soil test Results: What do all the numbers mean? CSIRO

Publishing, Collingwood, Vic.

Metson, A.J. (1961). Methods of Chemical Analysis for Soil Survey Samples. Soil Bureau Bulletin No 12, New

Zealand Department of Scientific and Industrial Research.

Sims, J.T. and Johnson, G.V. (1991). Micronutrient soil tests. In: Micronutrients in Agriculture (eds Mortvedt,

J.J., Cox, F.R., Shuman, L.M. and Welch, R.M.). pp. 427‐472. Soil Sci. Soc. Am. Book Series no 4. Soil Sci

Soc Am Inc, Madison, USA.

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