Soils and landforms of the Bairnsdale and Dargo Region

1. Introduction | 2. How to use this guide | 3. Climate | 4. Geology and Geomorphology | 5. Rocks and sediments in East Gippsland | 6. Land Use | 7. Soil issues | Soil - landform units | Plant nutrients and interpretation of soil analytical data | Acknowledgements| References

1 Introduction This manual covers an area that stretches from Stratford in the west to Lakes Entrance in the east and north to the boundaries between freehold and the Mitchell River National Park and State Forest, covering an area of around 200,000 hectares. Dargo has also been included mostly using the work covered in the publication ‘A Study of the Land in the Catchment of the Gippsland Lakes’ by Aldrick et al. (1992). The manual presents information about the geology and geomorphology of the study area and includes soil descriptions, management issues and chemical and physical analyses for most but not all of the soil/landform map units. Soils are classified according to the Australian Soil Classification (Isbell 1996). Terminology is consistent with that used in the Australian Soil and Land Survey Handbook (McDonald et al 1990). The information in this manual has been presented as ‘map units’ which describes areas in terms of geology, landforms and dominant soils. The name of the map units have generally been derived from the original name given by authors of previous studies in the area. During this study a number of soil pits were described, and some are included from a previous tunnel erosion survey (DPI 2010). Seventeen sites were from the report ‘A Study of the Land in the Catchment of the Gippsland Lakes’ by Aldrick et al. (1992) and nineteen sites from Ward and Little (unpublished, CSIRO survey 1977) are also included. The information from this manual will be made available on the Victorian Resources Online website (http://vro.agriculture.vic.gov.au/dpi/vro/vrosite.nsf/pages/vrohome).

2 How to use this guide
Within a given locality soils which share common characteristics can be grouped together and distinctions can be made between other ‘groups’ of soils. For example, the soils and topography of Red Gum Plains west of Bairnsdale are quite different from soils and topography of the granite hills around Dargo.

This guide is based on ‘soil landform map units’. Map units have similar geology, topography and the range of soil types. Each map unit may have two or three separate ‘types’ of soil, called ‘components’ which would be difficult to separate without making the map too complicated. Thus within a given ‘soil landform map unit’ there may be one component typical of the hill crest, another on the slope and another on the more gently sloping land.

Many of the map units have distinguished between land which has slopes generally less than 15% and land with slopes generally exceeding 15%. This was done to separate land which is regarded here as too steep for normal cultivation.

We have decided to give the same soil landform map unit name to all areas with a similar set of soils formed on a similar type of parent material, similar topography and similar climate. These soils will also usually have similar natural vegetation. For example, the soil landform map unit ‘Talbotville’ was named after an area around Talbotville (about 25 km north-west of Dargo) which had mostly shallow soils on steep topography developed on Palaeozoic (Ordovician, Silurian and Devonian) sedimentary rock. Similar soils and landforms occur elsewhere in Gippsland so the same name has been given to all other similar soil landform map units.

Following the soil landform map unit descriptions is a section titled ‘Plant nutrients and interpretation of soil analytical data’ and a glossary of soil terms. These sections will assist some readers to better interpret the soil information provided within each map unit.
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Table 1. Soil landform map units based on the underlying rock/sediment, elevation, rainfall and landform pattern

Name	Symbol	Rock/sediment	Elevation (m)	Terrain Slope	Relief (m)	Landform Pattern
Briagolong	Br	Pleistocene alluvium (Qp4)	20 - 50	<3%*	<9	Gently undulating plain
Calulu	Cu	Pleistocene alluvium and Miocene limestone	20 – 50	Up to 32%	9 - 30	Valley sides
Coastal dunes	cd	Recent aeolian sands	0 - 20	<32%	<30	Rolling rises
Dargo#	Do	Palaeozoic granite	160 - 750	<32%	80 - 180	Rolling hills
Deadhorse#	Dh	Palaeozoic granite	60 - 280	<32%	60 - 180	Rolling hills
Drainage line	dr	Recent alluvium (Qra)	any	<5%	<9	Alluvial plain
Fernbank*	Fe	Pleistocene alluvium (Qp2)	20 - 125	<10% *	9 - 30	Undulating rises
Gormandale#	Go	Pleistocene to recent aeolian sediments	0 – 30	<32%	<30	Dune
Glenmaggie#	Gm	Late Devonian freshwater sediments	150 - 520	<32%	80 - 360	Rolling to steep hills
Lindenow	Li	Recent alluvium (Qra)	0 - 20	<3%	<9	Alluvial plain
Munro	Mu	Pleistocene sands	50 - 200	Typically <10%	<90	Undulating to rolling rises
Nindoo*	Nn	Pleistocene alluvium (Qp1)	120 - 160	Typically <10%*	<30	Undulating rises
Perry	Py	Pleistocene aeolian sands	20 -160	<10%	<30	Undulating plain to undulating rises
Recent marine	rm	Recent marine sediments	Mostly <5%	<3%	<9	Level plain
Roseneath	Rn	Recent marine sediments	< 5	<3%	<9	Gently undulating plain
Seacombe	Sm	Recent aeolian sands	5 - 20	<10%	<30	Undulating rises
Stratford*	Sf	Pleistocene alluvium (Qp5)	20 – 50	<3%*	<9	Gently undulating plain
Stockdale	Sd	Neogene (Tertiary) alluvial sediments	50 - 200	Typically <10%	<90	Undulating low hills
Swamp	sw	Recent alluvium and water	any	<3%	<9	Level plain
Talbotville	Te	Palaeozoic marine sediments	100 - 1000	<56%	>300	Steep mountains
Tambo#	Tb	Palaeozoic marine sediments	50 - 500	<32%	<300	Rolling hills
Timbarra	Ta	Palaeozoic granites and gneisses	60 - 700	<56%	<300	Rolling to steep hills
Tinamba	Ti	Recent alluvium (Qra)	10 - 60	<3%	<9	Alluvial plain
Turton	Tn	Late Devonian freshwater sediments	200 - 500	<56%	<300	Steep hills

Map units in bold are extensive whereas those in italics are minor.

* Units comprising Pleistocene alluvial sediment are dissected adjoining drainage lines and slopes may be steeper than indicated here.
^# Slopes within these map units are generally less than 15 %.
Slopes within these map units are generally greater than 15 %.

Soil - landform map units of the Dargo region

Soil - landform map units of the Bairnsdale region

Soil - landform map units of the Bruthen Lakes Entrance region

3 Climate
The data presented here is from the Bureau of Meteorology. Records for the Bairnsdale Post Office have not been kept since 1970.

3.1 Temperature
There is little appreciative difference in the temperature data between the two stations over most of the year. Whether or not the slight increase in temperature from January to April compared to the earlier record is significant has not been determined.

Table 2: Mean maximum and monthly temperatures for Bairnsdale

	Jan	Feb	Mar	Apr	May	Jun	July	Aug	Sept	Oct	Nov	Dec
Bairnsdale Airport 1943-2010
Mean maximum temp.	25.8	25.4	23.8	20.7	17.5	15.1	14.5	15.7	17.6	19.7	21.6	23.5
Mean minimum temp.	12.7	12.8	11.0	8.5	6.7	4.8	3.9	4.5	5.8	7.4	9.5	11.1
Bairnsdale Post Office 1896-1970
Mean maximum temp.	24.6	24.7	23.1	20.3	17.0	14.3	13.8	15.3	17.4	19.6	21.7	23.4
Mean minimum temp.	12.3	12.7	11.2	8.5	6.0	4.2	3.4	4.1	5.9	7.7	9.4	11.2

Source: Bureau of Meteorology, Australian Government. Data are in degrees centigrade.

3.2 Rainfall
Rainfall data for both stations indicate a weak late spring – early summer maximum (Table 3). The mean rainfall over the 1943 – 2010 period is lower than for the 1986 – 1970 period, but the median rainfall is only marginally lower (Table 3).

Table 3: Mean annual rainfall for Bairnsdale (mm)

	Jan	Feb	Mar	Apr	May	June	July	Aug	Sept	Oct	Nov	Dec	Tot.
Bairnsdale Airport (1943-2010)
Mean rainfall (mm) (external link)	49.9	49.7	40.3	56.3	46.8	58.4	51.0	35.6	54.7	59.1	82.0	59.1	643.6
Decile 5 (median) rainfall (mm) (external link)	42.4	39.5	40.8	42.0	36.1	31.1	38.6	35.4	49.8	47.8	63.0	54.6	660.9
Bairnsdale Post Office (1896-1970)
Mean rainfall (mm) (external link)	60.2	50.2	67.0	50.2	54.4	58.4	50.2	48.9	56.8	70.2	64.4	67.7	698.8
Decile 5 (median) rainfall (mm) (external link)	45.5	37.3	44.3	40.4	39.2	43.5	42.4	39.8	52.8	66.7	50.9	54.6	681.2

Source: Bureau of Meteorology, Australian Government

Mean and median rainfall at Bairnsdale is relatively uniformly distributed throughout the year (Table 3), but there appears to be a slight depression in rainfall since 1970.

Table 3 does not give any indication of the variability of the rainfall. From year to year the monthly rainfall is highly variable, which makes it difficult to predict the beginning and end of the growing season.
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4 Geology and geomorphology

The account given below of the geological history of East Gippsland has been simplified.

Table 4. Geological time scale showing approximate age of significant events in the Bairnsdale area

Era	Period	Epoch	Millions of years	Significant event
	Quaternary	Recent	Last 10,000 yrs	Modern rivers incise into older flood plains
		Pleistocene	1.6	Formation of the terraced eastern plains formed by stream deposition from Toongabbie to Lakes Entrance. Several periods of ice age conditions followed by warming
		Pliocene	5	Deposition of sands and sandy clays following the uplift of the Eastern Highlands. Plains extend along the southern footslopes of the Highlands from Traralgon to Orbost
		Miocene	23	Major uplift of the Eastern Highlands
	Tertiary	Oligocene	36	Volcanic flows near Gelantipy and the Fraser Tableland
		Eocene	53	Brown coal deposits in Latrobe Valley
		Palaeocene	65	Australia drifts clear of Antarctica
	Cretaceous		145	Extinction of dinosaurs Age of upper Otway and Strzelecki rocks
	Jurassic		205	Development of rift between Australia and Antarctica
	Triassic		250	Granitic rocks and Volcanic flows near Benambra
	Permian		290	Ice covered most of Victoria, causing considerable denudation of the highlands
	Carboniferous		360	Minor tectonic event causing faulting
	Devonian		405	Major uplift, faulting and folding. Mountains formed in Eastern Victoria. Granitic and volcanic rocks in Central Victoria Buchan basin formed Major uplift, folding and faulting.
	Silurian		436	Granitic and volcanic rocks in Eastern Victoria Shallow sea in a trough from Bairnsdale to Corryong Major uplift, faulting and folding of much of East Gippsland. Much of Victoria became dry land
	Ordovician		510	Most of Victoria under a deep sea. Sediment from mountains in South Australia and far western Victoria accumulated on sea floor
	Cambrian		560
Pre-Cambrian			4600

Time scale derived from Introducing Victorian Geology. Geological Society of Aust. (Victorian Division) Melbourne 1991

Palaeozoic Era

The oldest sediments in this area are those deposited under deep marine conditions during the Ordovician (510 to 435 million years ago) when all except the far west of Victoria was under a deep sea. A major period of orogeny, which is the term given to periods of mountain building, occurred during the Late Ordovician – Early Silurian (440 – 420 million years ago). This orogeny is called the Benambran Orogeny. It was very intense and resulted in folding shearing and faulting at the end of which substantial areas of Victoria became dry land.

About 5 km north of Bairnsdale the parent rock mostly comprises Ordovician sediments, mostly fine-grained sandstone, siltstone and claystone. The Tambo and Nicholson Rivers and Clifton Creek derive most of their sediments from these rocks, so one would expect the river sediment would be sand to clay with few cobbles, rather than gravelly and many cobbles like the beds of the Mitchell and Avon Rivers (see later). The sediments in the alluvial terraces would also reflect differences in parent material.

However West Gippsland remained under a deep ocean throughout the Silurian (435 to 405 million years ago) into the Middle Devonian (about 380 million years ago.), over which time a very thick sequence of sediments were deposited. To the east a deep rift was also under sea. This extended from south of Bairnsdale north towards Corryong and during the Silurian it became filled with volcanic material and marine sediments.

The Late Silurian and Early Devonian (about 400 million years ago) was marked by a less intense period of mountain building, the Bowning Orogeny. Many of the granitic intrusions into the Silurian and Ordovician sediments in eastern Victoria, for example around Dargo, were also formed during this period. These mostly occur east of Dargo. The sediments around these granitic intrusions are often hardened due to contact metamorphism.

A dramatic major period of mountain building and deformation, known as the Tabberabberan Orogeny, affected most of Victoria during the Early to Mid Devonian (395 – 385 million years ago). This produced a major mountain range, called the Tabberabberan Highlands, in Eastern Victoria. Uplift associated with this event caused the sea to retreat to the east, so all marine sedimentation then ceased in Victoria. The granites occurring in Far-East Gippsland are associated with this orogeny. Both intrusive (granitic rocks) and extrusive (acid volcanic rocks) were forced into and through the earlier Ordovician and Silurian sediments throughout Central Victoria later in the Devonian. The granitic rocks of Mount Taylor immediately north of Bairnsdale belong to this period.

A large sedimentary basin then developed west of the Tabberabberan Highlands. This basin, named the Avon Synclinorium, was first partly in-filled by rhyolites and rhyodacites, which are volcanic rocks, and later towards the Late Devonian by a thick body of fresh water sediments. These sediments are mainly conglomerate, pebbly sandstone, sandstone and siltstone and are known as the ‘red beds’ as they are commonly red and purple in colour.
Much of the Macalister, Avon and the lower part of the Mitchell River catchments are based on the hard rock, mainly conglomerate, pebbly sandstone, sandstone and siltstone of the Late Devonian Period. The beds of these streams contain coarse gravels and stones because the parent rocks are hard and the material has not travelled a great distance.

Towards the end of the Devonian there was a widespread but not very intense deformation known as the Kanimblan Orogeny which resulted in, for example, the Barkly Thrust which thrust the Cambrian to Lower Silurian rocks over the late Devonian sediments. This was the last orogeny to affect Victoria.
During the Late Carboniferous and Permian, about 290 million years ago, Victoria was positioned closer to the South Pole and largely covered by glaciers. Erosion over this period as the glaciers moved northwards changed the Victorian landscape greatly. No glacial sediments occur in this area.

Mesozoic Era

In the Late Jurassic and Early Cretaceous (160 – 96 million years ago) Australia and Antarctica began to split apart. As they moved apart, a long rift valley was formed in southern Victoria which was slowly filled up by up to 3,000 metres of fresh water sediments, largely volcanic material, probably from volcanoes of the Gippsland coast and in Bass Strait as well as sediments from the mainland (See Chapter 9: Mesozoic in ‘Geology of Victoria’ Ed. W Birch 2003). Included in these sediments are coal deposits (Wonthaggi) and plant and animal fossils, including dinosaurs. The climate at the time was probably similar to the climate in the Tasmanian rainforest today. The Otway and Strzelecki Ranges are comprised of these sediments, which were uplifted during the Middle to Late Cretaceous when Australia and Antarctica split apart. Outcrops of these sediments occur between Yallourn and Tyers, just east of the area. The end of the Cretaceous (65 million years ago) was marked by a mass extinction of many animal groups, including the dinosaurs. There are none of these sediments in the area covered by this report.

South of the foothills of the Dividing Range the sedimentary basin developed in the Early Cretaceous continued to widen and deepen, forming the Gippsland Basin in the Late Cretaceous to Early Palaeocene (about 70 –60 million years ago).

Cainozoic Era

Palaeogene
Following uplift of the Eastern Highlands the basin began to fill with a complex sequence of sediments.

The foothills immediately north of Sale and extending to east of Orbost are based on sediments deposited during this period. Early deposits are marine, generally limestone, but the later deposits are alluvial. Some creeks, for example Prospect Creek, have cut into the limestone on which ‘terra rossa’ (red friable soils with lime-rich subsoil) soils have developed.

Neogene
This was marked by a period of further uplift of the eastern highlands, resulting in erosion and the formation of gravelly alluvial fans and extensive flood plains sloping towards the south-east of the area. The dissected undulating rises which extend along the southern footslopes of the Highlands from Traralgon to Orbost are underlain by early Neogene (Tertiary) sediments. On the Gippsland plains, these have been covered by later (Quaternary) sediments.

Quaternary
The Quaternary Period extends from about 1.8 million years ago to the present and is subdivided into Pleistocene and Recent (12,000 years ago to the present). There were several ice ages during the Quaternary which caused considerable rises and falls in sea level. This was because as the ice caps grew in size, the water levels in the oceans dropped.

The last ice age was about 17,000 to 20,000 years ago and resulted in a sea level fall of about 150 metres and a land bridge between Australia and Tasmania. As well as being cold, the climate was dry and windy.

The Mitchell River, as well as those rivers further west in East Gippsland, cut deep valleys into their earlier flood plains, which then became partly in-filled as the sea level rose to its present level. This has resulted in a well-defined break between the old flood plain (upper terrace), and the present flood plain (lower terrace). Less extensive terraces formed on the Nicholson and Tambo River flood plains.

A number of sets of terraces were formed during the Pleistocene period in Gippsland, but whether they were formed as a result of sea level change associated with ice ages or uplift or a combination of both has been debated. Ward (1977) postulated the terrace boundaries were former coastlines and the sand dunes were coastal features and recognised about ten former shorelines dating from 1.66 million years ago to the present.

This view was also held by Jenkin (1968) but later, in his contribution to ‘A Study of the Land ion the Catchment of the Gippsland Lakes’ by Aldrick et al. (1988), he decided there was no evidence for stranded beach-lines or old marine terraces. The present view is there is a succession of Pleistocene terraces (Vandenberg, 1981) and he identified five alluvial terraces with Qp1 being the oldest and Qp5 the youngest. An additional terrace, Qp6, has been recognised during this study.

Qp1
Minor occurrences of this terrace occur in the upper reaches of the Mitchell River and Perry River valleys.

Qp2
This terrace is the most extensive terrace, stretching, almost without interruption, from Stratford to Paynesville. It is very flat with an even SSE slope of about 1 in 200, with a maximum elevation of about 160 metres near Briagolong and 125 metres at The Fingerboards, and a minimum elevation of 20–25 metres at its southern margin. However, some geologists believe more than one terrace may be present.

Sand hills and dunes form a discontinuous mantle over the plain east of Blackall Creek, and these become more extensive east of Perry River. The sand dunes in these areas were most likely formed from sands blown from these streams by the prevailing westerly winds, particularly during periods of aridity associated with past glacial periods.

Qp3
This is the least extensive terrace, and is represented by three isolated terraces near Stratford, Wuk Wuk, and Lindenow South. Its elevation is 20-30 metres lower than Qp2.

Qp4
This occurs as wide, flat terraces in the Avon, Mitchell, Thomson and Macalister river valleys. This has a much gentler southward gradient of between 1 in 300 and 1 in 450. Thus, the difference between Qp2 and Qp4 is about 60m at Briagolong, but decreases steadily to 15m near Stratford.

Qp5
This terrace has a similar distribution to Qp4 and is about 20 to 30 metres lower. An extensive area between Toongabbie and Nambrok West is regarded as Qp5. Minor areas of Qp5 terraces occur on the alluvial plains associated with the Mitchell, Nicholson and the Tambo Rivers.

Qp6
This is included under Qra on the geological maps. The soils generally have a deep surface soil overlying a reddish sub-soil and are regarded as excellent irrigation soils. They mostly occur around Sale and Nambrok. Small areas also occur east of Bairnsdale.

Qra
This includes all modern flood plain deposits of the various rivers. The soils on these flood plains mainly comprise fine sand, silt and clays.

Inland dunes

Qpd
The inland sand hills and dunes cover many of the terraces between Qp2 to Qp5. They form a discontinuous mantle over the alluvial plains east of Blackall Creek, and become more extensive east of Perry River. The dunes in these areas were most likely formed from sands blown from these streams by the prevailing westerly winds, particularly during periods of aridity associated with past glacial periods.

Coastal dunes and plains
These dunes and plains were mostly formed during the last 10,000 years when sea levels were about 2 m higher than they are today.

Qrd
This geological unit includes the dunes which adjoin the present coastline.

Qrm
This includes the estuarine plains which were deposited during the last 10,000 years.

Table 5. Subdivisions of the East Gippsland alluvial terraces, coastal plains and coastal dunes and corresponding soil/landform Map units

Geological Subdivision 1	Landform	Map Unit	Example
Tertiary	Foothills (dissected former plain)	Stockdale	Extensive foothills at the base of the Highlands
Qp1	Dissected high level terraces	Nindoo*	Minor occurrences in the upper Mitchell and Perry River valleys
Qp2	Undulating plain, minor dissection	Fernbank*	Stratford to near Bairnsdale
Qp3	Undulating plain	Moormurng*	Minor occurrences
Qp4	Near level plain, slightly dissected around Bairnsdale	Briagolong*	Heyfield, Briagolong, west of Bairnsdale
Qp5	Terrace plain	Stratford*	Stratford, Toongabbie, Lucknow
Qp6	Terrace plain	Tinamba#	Clydebank, Sale, Nambrock
Qrd	Inland dunes	Munro	Dunes in the level foothills, Stockdale
		Perry##	Dunes, mostly east of the Perry river
Qra	Present flood plains	Mitchell	Present flood plains, Mitchell and Tambo River flats
Qrd	Coastal dunes	Seacombe	Coastal dunefields, Raymond Island, Sperm Whale Head
		coastal dunes	Barrier dunes fronting the coastline
Qrm	Marine plain	Roseneath*	Recent marine deposits, mostly clays, west of Roseneath Point
	Tidal areas and low dunes	recent marine	Mostly low dunes and tidal flats, Holland’s Landing
	Swamps	swamp	Miscellaneous permanent and semi-permanent swamps

# From Skene and Walbran (1943 1949)
## From Aldrick et al. (1992)
*From Ward (1977)
¹ VandenBerg (1977, updated 1997)
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5 Rocks and sediments in East Gippsland

5.1 General classification of rocks
In East Gippsland the soils have been formed both on hard rock and loose material transported by water or wind, or collecting from higher up a slope. This is known as the ‘parent material’ of the soil. Hard rocks in the area include:

Igneous rocks: Rocks formed from molten rock – either deep below the earth’s surface (plutonic, such as granites) or at the earth’s surface (volcanic, such as the basalts around Gelantipy). Granitic rocks are normally coarse grained – meaning one can see the different coloured mineral grains in the rock with the naked eye, whereas the mineral grains in volcanic rock are fine and normally can only be seen under magnification.

Sedimentary rock: Rocks formed from the erosion products of other rocks or sediments, from shells and corals (eg limestone) or plant remains (eg coal). They may also be subdivided into hard sediments or soft sediments, including unconsolidated sediments that have not yet formed the hard material we would usually think of as ‘rock’. Depending on the particle sizes in the sediments, hard sediments may be subdivided into conglomerates that are mostly of stony material, sandstone, siltstones and mudstones.

In Gippsland, most of the hard sedimentary rocks formed from ancient sediments deposited in the Palaeozoic era. These rocks vary in hardness depending on the degree of metamorphosis they have experienced; for example, those formed from finer sediments range from mudstones, shales, schists to gneisses, with mudstones being softest and gneisses hardest. The gneisses here are similar to granite in grain size and like granite, weather to produce sandy soils. Sandstone may become metamorphosed into quartzite.

Soft sediments in East Gippsland are generally less ancient, from the Cainozoic era or later, eg the brown coal deposits in the La Trobe Valley. Perhaps the most extensive areas of soft sediments in East Gippsland are the undulating plains immediately south of the Eastern Highlands, extending from Stratford to Cann River. These were mostly deposited during and after a major uplift of the Eastern Highlands about 5 million years ago. Periods of wind, aridity and cold during the last ice age, about 20,000 years ago, have resulted in some of this area becoming partially mantled in sand. The youngest sediments are those in the present river valleys and flood plains.

Metamorphic rock: Any rock which has been changed substantially by heat, pressure or deformation. In Gippsland these include schist, gneiss and quartzite. The rocks may be changed by heat and shearing during periods of mountain building, eg the rocks around Ensay North, or by heat due to contact with granites as they cooled deep underground, eg steep hills around the granites near Dargo.

5.2 Rocks to soils
The longevity of stone, whether it is in a building, gravestone or bridge shows us the transformation of rock to soil is an extremely slow process. Even when a depth of soil has accumulated, the development of a soil profile such as a texture contrast soil similar to those seen in road cuttings south of Omeo is believed to take tens of thousands of years.

Soils form from rock as a result of a process termed weathering, and includes both physical and chemical processes. Chemical processes are more active at the surface of the rock fragments, the smaller the rock fragment the more rapidly it will decompose. Thus the physical processes that break rocks down into smaller fragments greatly speed up the chemical processes converting rock to soil.

Physical weathering is the breakdown of rock by entirely mechanical methods. Sometimes the forces leading to the breakdown of rock originate within the rock; at other times forces are applied externally. Cracks often develop in rocks close to the surface and frost can crack rocks when water confined in these cracks freezes and expands. Temperature changes cause expansion or shrinkage in rocks, and repeated changes in temperature cause the rock to crack or break up, particularly when soil particles fall into the crack and prevent it from closing. Wetting and drying of mudstones can also result in physical weathering as water molecules orient themselves around the clay particles and force them apart. Other methods of physical weathering include mechanical abrasion and collapse under gravity, causing the rock to break down into smaller fragments.

Plants, including mosses and lichens, are a major factor in soil formation. Roots break open small cracks in the rock, help keep the soil in place and retain water necessary for continued weathering.

Chemical weathering is the change in the mineral composition of the rocks and rock fragments. These changes are brought about by oxygen, water and dissolved carbon dioxide in water. The rate of soil formation increases with increasing temperature and rainfall. After prolonged weathering, the major weathering products of rocks are clays of various types and quartz, which is most resistant of the common minerals to chemical attack. Most silt, sand and gravel particles in a soil are quartz. Soils formed from granite generally have a high coarse sand component because of the quartz crystals present in granite.

Climate has a major bearing on soil formation. The effects of climate on soil formation are further complicated as it affects both plant production and biological activity, which in turn further influences the soil profile. As the rainfall and temperature increases, biological activity also increases often resulting in deep disturbance of the soil profile and the consequent absence of a marked clay horizon deeper in the soil profile. Organic matter content in surface strata can be higher than of soils formed under lower rainfall. Examples of these types of soils are found under the damp mountain ash forests of Gippsland.

Position within the landscape is a major determinant of the rate at which soil material accumulates. The soil in mountainous and very steep hilly land is generally rapidly eroded away, leaving only a shallow soil cover. Here there are comparatively young soils on geologically old rock. On the other hand, soil tends to be deeper on flatter land as erosion rates are slower. Lower slopes and valleys tend to collect soil washed from elsewhere as colluvium (material moving under gravity down slope) and alluvium (material moved by water) and can have deeper soils.

A defined soil profile slowly develops once a sufficient depth of soil has accumulated. Over time, clay may gradually move down the soil profile: the end stage of this process is the formation of a texture-contrast soil with well defined clay subsoil. Many soil profiles in East Gippsland show this feature. Organic matter tends to accumulate in the topsoil, resulting in darker colours. Iron oxide also moves downwards resulting in stronger, brighter colours in the clay horizon. Often iron oxide nodules or concretions accumulate above clay, but whether these are remnants of earlier soil profiles is open to conjecture.

In the strongly structured soils developed over basalt, eg around Gelantipy, the high amount of free iron oxide converts the clay particles into stable clay aggregates. Clay particles are not easily moved down the soil profile and texture contrast soils do not occur. In river valleys and low lying areas, soil accumulates so rapidly that a well defined soil profile has little chance to form, other than an accumulation of organic matter in the topsoil. Soils on the Benambra flats are such an example. In these situations soil texture is uniform throughout the profile or changes only gradually with depth.

Soil classification
In describing a soil the major properties looked at by soil scientists include:

• The position in landscape and the degree of slope (eg eastern mid-slope 15%)
• The sand, silt and clay content – as determined by its soil texture (or feel between the fingers when moist)
• Degree of contrast in texture of successive horizons and the sharpness of the transition
• Colour of each horizon
• Size, shape and consistence of the natural aggregates (peds) and the pattern of cracks between them
• Presence or absence of free lime, either as white streaks or as large round concretions
• Presence or absence of ironstone gravel
• Degree of acidity or alkalinity
• Depth to parent rock or unconsolidated parent material.

So soil scientists can better develop a mental picture of a particular type of soil, a soil classification scheme has been devised which suits Australian soils. The latest attempt to classify our soils is the Australian Soil Classification. Australian soils have been subdivided into 14 Orders. These are described in the table below. Soil Orders are further subdivided into sub-orders, then great groups, followed by sub-groups. In this report a simplified scheme will be used, for example a red Sodosol is a common soil on the more undulating area on granite around Swifts Creek. One characteristic of the Sodosols is the tendency of the subsoils to disperse, which on slopes, can cause tunnel and gully erosion.

Australian Soil Classification

Soil order		Example
Human made soils Dominated by organic materials Negligible pedological organisation Weak pedological organisation Bs, Bh, or Bhs horizons* Clay ≥ 35% in all horizons, cracks, slickensides Prolonged seasonal saturation Strong texture contrast between A and B horizons pH < 5.5 in upper B horizon Sodic in upper B horizon with pH ≥ 5.5 Non-sodic in upper B horizon with pH ≥ 5.5 Lacking strong texture contrast between A and B horizons Calcareous throughout profile or below A1 High free iron B2 horizon Structured B2 horizon Massive B2 horizon	ANTHROPOSOLS ORGANOSOLS RUDOSOLS TENOSOLS PODOSOLS VERTOSOLS HYDROSOLS KUROSOLS SODOSOLS CHROMOSOLS CALCAROSOLS FERROSOLS DERMOSOLS KANDOSOLS	Highly disturbed building sites Dark peaty soil on the High Plains Shallow soils on steep hilly uncleared forest land north of Tambo Crossing As above, but slightly deeper soils Deep sand soils just east of Providence Ponds (Perry River) Cracking clay soils on the flats near Lake Omeo Swamp soils Typical soils exposed on road cuttings between Lakes Entrance and Cann River Typical soils on the Munro Plains Common around Swifts Creek Many soils on undulating land around Omeo Soils on limestone around Buchan Dark red and brown heavy loam soils around Gelantipy and Fraser Tableland Many soils on undulating land around Cobungra Not common in Gippsland

* Bh (organic or humus enriched B horizon)
Bs (iron or aluminium oxide enriched B horizon)

Organosols with their peaty top-soil are common on the High Plains. Rudosols and Tenosols are generally shallow soils in Gippsland and common on steep slopes with little soil cover. Podosols are mainly sandy soils with ‘coffee rock’ at depth in the soil profile and frequently occur in the foothills. Vertosols are high clay content soils and are found on the Benambra flats. Kurosols, Chromosols and particularly Sodosols are common on undulating land comprising a variety of rock types. Kurosols are acidic and may benefit from lime applications, whereas Sodosols are sodic and prone to gully and tunnel erosion. Calcareous soils are found around Buchan on the limestone country, where they are generally strongly structured. Ferrosols, which are dark brown to red well-structured loam soils on basalt, occur around Gelantipy and the Fraser Tableland and are well suited to intensive agriculture. Dermosols and the weakly structured or massive Kandosols are common in higher elevations and, like Sodosols, occur on undulating to hilly country. Excepting Anthroposols and Organosols, examples of all of these soil orders are described in East Gippsland.
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6 Land use

6.1 Land use
Agriculture, forestry, nature conservation, recreation and residential use are the main present land uses. Cattle and sheep grazing is the most widespread form of agriculture although there are areas of horticulture on the Mitchell and Tambo River flats. Some cropping and irrigated horticulture using groundwater is carried out on the Red Gum Plains.

6.2 Nature conservation and recreation
This manual’s study area adjoins a small part of the Alpine National Park. At 646,000 ha, it is the State's largest park, which, with adjoining national parks in NSW and the ACT, forms a protected area over most of Australia's high country. Extensive snowfields are the primary winter attraction; while the warmer months bring stunning wildflower displays and opportunities for bushwalks and four wheel driving. The 650 km Australian Alps Walking Track traverses the Alps from Walhalla to Canberra.

7 Soil issues
Soil under agricultural use must be physically, nutritionally and biologically balanced to be productive and stable. Soil structure decline, soil acidification and soil erosion are common soil health issues with the potential to severely restrict agricultural productivity on susceptible soil types, while erosion may also contribute to downstream sedimentation and turbidity within water storages (Hollier 2003).

In order to protect the soil, it is important to maintain groundcover in the form of living plant material, failed crops, and crop stubbles or pasture residues. The Drought Preparation and Survival Guide (NRE 2002) points out the amount of groundcover will depend upon the region, soil type and seasonal weather expectations and it is important to remember pasture and stubble will deteriorate over time due to trampling, wind and rain damage.

7.1 Soil structure decline
Soil structure, or pedality, refers to the arrangements of soil particles and the spaces (pores) between them. Natural aggregates are called peds, therefore a soil may be pedal or apedal depending on the presence or absence of peds. The structure of a soil governs infiltration and the volume of air and water available for plant growth. Structural deterioration leads to surface crusts and compaction which inhibit plant growth and reduce soil biological activity. Soil structure can be maintained by paying attention to stocking rates, removing livestock from wet areas and maintaining vegetation cover (Hollier 2003).

7.2 Soil erosion
The steeper slopes in the study area are highly prone to water erosion, particularly sheet and gully erosion. Sheet erosion is caused by heavy rain falling on unprotected slopes and is characterised by a more or less uniform wasting away of the surface soil. It rapidly reduces the productivity of land by carrying off the rich organic matter and readily available plant food, and may continue for lengthy periods undetected. If unchecked it is rapidly followed by rill and gully erosion (SEC 1938). Gullies are defined as open erosion channels at least 30 cm deep that conduct ephemeral runoff and are frequently characterised by steep side walls and a lack of vegetation, whereas rills are narrower and shallower than gullies (Boucher 2006).

Topsoil dislodged and carried away by wind or water removes nutrients such as nitrogen, phosphorus and organic carbon, which are integral components for the health of the soil and production. With every millimetre of topsoil eroded, it is estimated about 13 t/ha of topsoil, 130 kg/ha of organic carbon (based on a soil carbon level of 1%), 20 kg/ha of nitrogen equivalent to 40 kg of urea and 8 kg/ha of phosphorus equivalent to 100 kg of super phosphate are lost. It is possible to replace phosphorus and some nitrogen through fertiliser application, however organic carbon and nitrogen take years of careful management to restore. Hence soil erosion will decrease the productivity of the land for many years to come (NRE 2002).

Climate in relation to erosion
Rowe (1967) observed high intensity rainfall is responsible for starting most of the serious erosion in the region and therefore the condition of the land upon which high intensity rainfall occurs is critical. The remedy is to maintain as dense a ground cover as practicable and careful grazing management of the pastures in summer is necessary, particularly on slopes, so overgrazing does not reduce cover below suitable limits.

In dry periods, soils become more susceptible to wind erosion. When groundcover is lost, strong winds are able to erode soil particles depositing them either as drifts along fence lines or transporting them up to thousands of kilometres away (NRE 2002).

7.3 Soil acidity
Australia's soils are old and highly weathered and some of them will be naturally more acidic than others (COA, 2001). In the high rainfall (>600mm/year) zones of Victoria soil acidification is becoming a priority issue for many farmers (Hughes 2001). Most are moderately acid at the surface, with a pH of between 5.5 and 6, with areas of strongly acid soils (pH 5-5.5). Landcare Victoria (1992) estimates strongly acid soils, i.e. pH of less than 5.5 in water, affects 1.2 million ha of Victoria's agricultural land, costing $15 million in lost production annually.

Extremes in acidity also present problems for the production of many agriculturally important clover species and their symbiotic rhizobia. Soil chemistry is complex and it can be difficult to identify the precise cause of poor plant growth or nodulation. However, aluminium and manganese toxicities, as well as molybdenum and phosphorus deficiencies, are probable causes of poor production in many strongly acid soils (DPI 2004).

In a report titled ‘The impact of acid soils in Victoria’ Slattery (2002) suggests the causes of soil acidity are:

• Removal of product from the farm or paddock
• Leaching of nitrogen as nitrate below the plant root zone
• Build up of organic matter
• Inappropriate use of nitrogenous fertiliser
• Erosion of top soil, sub-soil becoming surface soil.

Nitrate leaching and build-up of soil organic matter are the major causes of soil acidity under grazing systems. Lime is usually used to increase soil pH in strongly acid soils. The quantity of lime needed will vary between soils. Generally, coarse textured soils (eg sands) need less lime than finer textured soils. Also, low organic matter soils need less lime than peaty soils. A lime requirement test will incorporate these effects when used to determine the amount of lime needed to raise soil pH. Other factors needed to determine an appropriate lime rate include target pH of the specific plant, lime quality, application method and economics (DPI 2004).

The use of acid tolerant plants is widespread in the higher rainfall grazing areas. Many producers rely on moderate to highly tolerant pasture species (eg subterranean clover, perennial ryegrass and cocksfoot). Since the mid 1990s there has been a revival in the establishment of perennial systems (phalaris). This trend is reflected in increased lime usage. There is growing interest in low input native pastures for light textured, rocky or steep areas where it is difficult to apply lime (Hughes 2001).

Soil ameliorants
Many of the surface soils are moderately to strongly acid. To overcome soil acidity, lime is often added at rates which are determined by the degree of acidity and the surface texture. Before lime is added it is usual to have test strips to see whether lime is going to provide an economic benefit. When the pH’s of the surface soils are higher than 5.5 (moderately acid) it is most unlikely adding lime will be economic. At pH’s between 5.3 and 5.5, adding lime is also unlikely to be economic. Below pH’s of 5.3, adding lime may be beneficial. A pH test sampled from across the paddock would be most appropriate to determine whether lime is needed to raise soil pH. Other factors need to be considered before lime is recommended (e.g. pasture species grown, method of application, local trial responses, soil surface structure and likely cost/benefit).

Liming of soils is a common practice and this, together with the naturally low boron levels in some soils could lead to deficiency symptoms. As for all trace elements, the application of Boron fertiliser should be guided by plant tissue analyses. Refer to trace element section in the chapter titled ‘Plant nutrients and interpretation of soil analytical data’.

Fertilisers
It is not possible for this report to comment specifically on fertiliser requirements for the various map units. The main ones used are phosphatic fertilisers, generally with added molybdenum, and potassium fertilisers. Specialist advice on soil tests should be sought prior to fertiliser applications.

Removal of phosphorus and potassium
The main agricultural uses in the area are grazing for meat and wool production. These activities remove a certain amount of these plant nutrients which, in the long term, deplete the phosphorus and potassium reserves in the soil. Approximate guides to the amounts removed are given in Table 5.

Table 5: Potassium and phosphorus removed by product, approximate values onlyTop

Soil - landform units

Briagolong (Symbol: Br)	Calulu (Symbol: Cu)	Coastal dunes (Symbol: cd)	Dargo (Symbol: Do)	Deadhorse (Symbol: Dh)
Drainage line (Symbol: dr)	Fernbank (Symbol: Fe)	Glenmaggie (Symbol: Gm)	Gormandale (Symbol: Go)	Lindenow (Symbol: Li)
Munro (Symbol: Mu)	Nindoo (Symbol: Nn)	Perry (Symbol: Py)	Recent marine: (Symbol: rm)	Roseneath (Symbol: Rn)
Seacombe (Symbol: Sm)	Stockdale (Symbol: Sd)	Stratford (Symbol: Sf)	Talbotville (Symbol: Te)	Tambo (Symbol: Tb)
Timbarra (Symbol: Ta)	Tinamba (Symbol: Ti)	Turton (Symbol: Tn)

Plant nutrients and interpretation of soil analytical data

1. Soil horizons | 2 Field texture | 3. Plant available water | 4. pH | 5. Soil salinity | 6. Nutrients needs by plants | 7. Cation Exchange Capacity (CEC) and Effective Cation Exchange Capacity (ECEC) | 8. Soil constituents | 9. Exchangeable Sodium Persentage (ESP) | 10. Calcium : Magnesium Ratio (Ca:Mg) | 11 Trace elements

Much of the information in this section comes from publications ‘A manual on the soil testing service provided by the Division of Agricultural Chemistry’ by A.J. Brown, K.K.H. Fung and K.I. Peverill (1982), ‘The analytical and interpretive service provided by Ag-Plus’ by K.I. Peverill, S.W. Margetts, A.J. Brown, N.B. Grennhill and G.R. Monro (1987) and a manual by P Hazelton and B Murphy (2007) titled ‘Interpreting soil test results: what do all the numbers mean?’ The definitions of soil horizons are from ‘Australian Soil and Land Survey’ (McDonald et al. 1990).

Much of the information in the section on trace elements comes from ‘Trace Elements for Pastures and Animals in Victoria’ prepared by W. J. Hosking, I. W. Caple, C. G. Haplin, A. J. Brown, D. I. Paynter, D. N. Conley and P. L. North-Coombes (1986) published by the Department of Agriculture and Rural Affairs, (available at http://vro.agriculture.vic.gov.au/dpi/vro/vrosite.nsf/pages/trace_elements_pastures).

Siegfried Engleitner, Future Farming Systems Research, of the former Department of Primary Industries, also assisted in review and provided helpful comment.

1 Soil horizons
A soil profile may be sub-divided into a number of soil horizons, which are layers of soil approximately parallel to the surface. The O and P horizons are dominated by organic material in varying stages of decomposition that have accumulated on the mineral soil surface, whereas the A, B, C , D and R are dominated by soil minerals. Information about the A, B and C horizons are included here.

A Horizons
These are horizons consisting of one or more surface mineral horizons with some organic accumulation and usually darker in colour than the underlying horizons, or consisting of surface and subsurface horizons that are lighter in colour but have a lower content of silicate clay and/or sesquioxides than the underlying horizons.

A1 horizon mineral horizon at or near the soil surface with some accumulation of humified organic matter, usually darker in colour than underlying horizons and with maximum biologic activity for any given soil profile
A2 horizon mineral horizon having, either alone or in combination, less organic matter, sesquioxides, silicate clay than immediately adjacent horizons. Usually paler in colour than the A1 horizons
A3 horizon transitional horizon between A and B which is dominated by properties characteristic of an overlying
A1 or A2.

B Horizons
These horizons consist of one or more mineral soil layers characterised by one or more of the following: a concentration of silicate clay, iron, aluminium, organic material or several of these; a structure and/or consistence unlike the A horizons above or of any horizons immediately below; stronger colours, usually expressed as higher chroma and/or redder hue, than those of the A horizons above or those of the horizons below.

B1 horizon transitional horizons between A and B, which is dominated by properties characteristic of underlying B2
B2 horizon horizon in which the dominant feature is one or more of the following:

• an illuvial, residual or other concentration of silicate clay, or iron, aluminium, or humus either alone or in combination;
• maximum development of pedologic organisation (i.e. all changes in soil material resulting from the effect of physical, chemical and biologic processes) as evidenced by a different structure and/or consistence, and/or stronger colours than the A horizons above or any horizon immediately below.

C Horizons
These are layers below the AB profile of consolidated and unconsolidated material, usually partially weathered, little affected by pedogenic (soil forming) processes and either like or unlike the material from which the solum presumably formed. It lacks properties characteristic of all other horizons and is recognised by its lack of pedological development and/or presence of geologic organisation frequently expressed as sedimentary laminae or as ghost rock structure as in saprolite.

D Horizons
These are considered to be any soil material below the soil solum in that it is unlike the solum in its general character and cannot be given reliable horizon designation.

R Horizons
These horizons consist of continuous masses of moderately strong to very strong rock.

2 Field texture
Field texture is determined by measuring the behaviour of a small handful of soil when moistened with water and kneaded (1-2 minutes) until it is quite moist but does not stick to the hand. This ‘ball’ is called a ‘bolus’. It provides an estimate of the relative amounts of coarse sand, fine sand, silt and clay sized particles. Field texture influences many soil physical properties such as water holding capacity and hydraulic conductivity. Numerous soil properties affect the determination of texture such as type of clay minerals, organic matter, carbonates, etc. Texture is determined by the behaviour of the moist bolus and the length of the ribbon when sheared between the thumb and forefinger.

Field texture symbol	Field texture grade	Behaviour of moist bolus	Approx clay content (%)
S	Sand	Coherence slight to nil, cannot be moulded: sand grains of medium size, single grains will stick to the fingers.	less than 5%
LS	Loamy sand	Slight coherence; sand grains of medium size; can be sheared between the thumb and forefinger to give a minimal ribbon of about 5 mm.	approx 5%
CS	Clayey sand	Sight coherence; sand grains of medium size; sticky when wet; many sand grains will stick to the fingers; will form a minimal ribbon of 5-15 mm; discolours fingers with clay stain.	5%-10%
SL	Sandy loam	Bolus coherent but very sandy to touch; will form a ribbon of 15-25 mm; dominant sand grains are of medium size and are readily visible.	10%-20%
FSL	Fine sandy loam	Bolus coherent; fine sand can be felt and heard when manipulated; will form a ribbon of 13-25 mm; sand grains are evident under a hand lens.	10%-20%
SCL-	Light sandy clay loam	Bolus strongly coherent but sandy to touch; sand grains dominantly medium sized and easily visible; will form a ribbon of 20-25 mm.	15%-20%
L	Loam	Bolus coherent and rather spongy; smooth feel when manipulated but with no obvious sandiness or ‘silkiness’; may be somewhat greasy to the touch if much organic matter present; will form a ribbon of about 25 mm.	approx 25%
Lfsy	Loam, fine sandy	Bolus coherent and slightly spongy; fine sand can be felt and heard when manipulated; will form a ribbon of approx 25 mm.	approx 25%
ZL	Silty loam	Coherent bolus; very smooth to often silky when manipulated; will form a ribbon of approx 25 mm.	clay approx 25%; more than 25% silt
SCL	Sandy clay loam	Strongly coherent bolus; sandy to the touch; medium sized grains visible in the finer matrix; will form a ribbon of 25-40 mm	20%-30%
CL	Clay loam	Coherent plastic bolus; smooth to manipulate; will form a ribbon of 40-50 mm.	30%-35%
CLS	Clay loam, sandy	Coherent plastic bolus; medium sized sand grains in the finer matrix; will form a ribbon of 40-50 mm.	30%-35%
ZCL	Silty clay loam	Coherent smooth bolus; plastic and often silky to touch; will form a ribbon of 40-50 mm.	clay 30%-35%; more than 25% silt
FSCL	Fine sandy clay loam	Coherent bolus; fine sand can be felt and heard when manipulated; will form a ribbon of 38-50 mm.	30%-35%
SC	Sandy clay	Plastic bolus; fine to medium sands can be seen, felt or heard in the clayey matrix; will form a ribbon of 50-70 mm.	35%-40%
ZC	Silty clay	Plastic bolus; smooth and silky to manipulate; will form a ribbon of 50-70 mm.	clay 35%-40%; more than 25% silt
LC	Light clay	Plastic bolus; smooth to touch; slight resistance to shearing; will form a ribbon of 50-75 mm.	clay 35%-40%; more than 25% silt
LMC	Light medium clay	Plastic bolus; smooth to touch; slight to moderate resistance to forming a ribbon; will form a ribbon of 75 mm.	40%-45%
MC	Medium clay	Smooth plastic bolus; can be moulded into a rod without fracturing; has a moderate resistance to forming a ribbon; will form a ribbon of 75 mm or more.	45%-55%
MC	Heavy clay	Smooth plastic bolus; strong resistance to manipulation and forming a ribbon; will form a ribbon of 75 mm or more.	More than 50%

Source: After McDonald et al. (1990)

3 Plant Available Water

After a soil has been subject to heavy rain for a prolonged period, most of the soil pores are filled with water. This soil is now saturated. Under the action of gravity, a certain amount of water drains into the subsoil (gravitational water). After this water has drained away, generally after two or three days under non-waterlogged or free draining conditions, the remaining water is called water held at field capacity. The plants grow, removing water. After exploiting all the water they can, the plants wilt to the point beyond which they cannot be revived (wilting point). At this stage the soil still holds water but the plant cannot overcome the strong forces of surface tension associated with the water held in the small soil pores and the thin water layer surrounding the clay particles. However the remaining water can be removed by heating the soil to 105 degrees C (oven dry). The plant available water content of a soil is considered to be the difference between the water content of a soil between field capacity and wilting point, and the values of these water contents vary from soil to soil. To determine these values in a soil in the paddock situation would be extremely difficult, so laboratory tests have been devised to simulate these conditions. This method involves sieving the soil to pass a 2 mm sieve and subjecting the wetted soil to a predetermined pressure to simulate free draining soil under gravity (field capacity) and the maximum suction roots can exert on the soil when they extract water (wilting point). The water content of the soil is then determined by weighing the soil before and after drying at 1050C. Hygroscopic water is the water absorbed from the air and varies according to temperature, humidity and the nature of the soil. These relationships are shown in the following diagram.

The main problem with the laboratory method is the soil is not intact as the soil aggregates are destroyed in passing through the sieve. Nevertheless these determinations are considered to be a useful guide to how much water can be stored in the various soil horizons. Plant Available Water (PAW) is the amount of soil water that can be extracted by the plant and is influenced by: Soil texture (eg up to 230 mm of water per metre of soil can be held in clay-rich alluvial soils, whereas only 50 mm per metre of soil may be held by sandy soils). Soil structure; roots tend to follow the cracks in a soil rather than penetrate the soil peds. Organic matter, soils of similar texture but with more organic matter will hold more water. Rooting depth (PAW is reduced in shallow soils over bedrock or in soils with dense sodic subsoils). soil structural damage, for example PAW is reduced when plough pans restrict root and water movement.

Roots follow the cracks in a soil rather than penetrate the soil peds. (Photos courtesy of Richard MacEwan)

In this report the PAW is calculated for the pit sites using a model developed by Littleboy (1995). This model uses a computer program to estimate PAW from soil survey data (i.e. % clay, % silt, % fine sand, % coarse sand, % rocks, wilting point and horizon depth). The effective rooting depth has been estimated based largely in soil profile morphology and an assessment of roots in soil pits. Generally, it is assumed effective rooting depth will be restricted by dense and coarsely structured subsoil horizons (particularly if these are sodic and dispersive); hardpans and high levels of soluble salts. Other factors can include extremes of pH and occurrence of frequent waterlogging.

Comparing the values for PAW using the difference between field capacity and wilting point, it is likely the computer program underestimates the plant available water. A possible reason could be the field capacity determination is on a disturbed sample rather than an intact field sample. In addition, the computer model does not take into account the organic matter content of the soil.

Another problem is related to root behaviour in soils. Plant roots need to respire, and research has shown if less than about 10% of the total pore space is occupied by air, the plant root looses function. This is when soils are at the wetter end of the scale. Some plants, such as rice, may be able to cope with lower values of air filled porosity than 10%. At the drier end, if the resistance of the soil is more than about 2.5 MPa, plant roots have a mechanical difficulty in exploring the soil and can only exploit the soil near cracks in the soil. However the soil must still be wetter than wilting point for plant growth.

In summary:

• The roots can’t penetrate if the soil is too hard and therefore can’t get the water out.
• If there is not enough soil air, the roots can’t function properly.

Values used for Plant Available Water
In this report the following values used for PAW are: extremely low <25 mm, very low 25-50 mm, low 50 -75 mm, moderate 75 -125 mm, high >125 mm. This is the maximum amount of water considered available to the plant roots. The effective root depth is stated for each soil profile.

4 pH
The pH of a soil is a measure of soil acidity and soil alkalinity on a scale of 0 (extremely acidic) to 14 (extremely alkaline), with a pH of 7 being neutral. Soils with pHs (in water) below 4.5 and above 9.5 rarely exist and do not provide a good growth medium. Plant growth is generally favoured by a soil pH between 5.5 and 8.0. With increasing low pHs, particularly below pH 5.5, exchangeable aluminium and sometimes manganese increases to toxic levels and molybdenum becomes increasingly unavailable.

Soil pH is carried out using two methods:

• pH(H₂O): the pH of the soil (in water) using a soil:solution ratio of 1:5 (10 grams soil to 50 mL water),
• pH(CaCl₂): the pH of the soil (in dilute calcium chloride) using a soil solution ratio of 1:5 (10 grams soil to 50 mL of 0.01M CaCl₂)

The pH of a soil using calcium chloride is usually lower than the pH using water by about 0.7 to 1.0 pH unit. (However, as soil salinity increases the difference between pH(H₂O) and pH(CaCl₂) will be reduced.) One of the reasons for using calcium chloride is to give a pH believed to be more closely related to the root environment, where the soil solution has soluble salts present, rather than pure water.

Some of the effects of increasing pH by liming are to:

• increase microbial activity, hence turnover (mineralisation) of organic matter,
• increase the availability of phosphorus and molybdenum, and
• decrease the availability of manganese and especially, aluminium

Descriptive terms for pH (H₂0) ranges

Descriptive term	pH	Descriptive term	pH
Extremely acid	less than 4.5	Slightly alkaline	7.1-7.9
Very strongly acid	4.5-5.0	Moderately alkaline	8.0-8.5
Strongly acid	5.1-5.5	Strongly alkaline	8.6-9.0
Moderately acid	5.6-6.0	Very strongly alkaline	9.1-9.5
Slightly acid	6.1-7.0	Extremely alkaline	more than 9.5
Neutral	7.0

Source: Brown et al. (1982)

5 Soil salinity
Soil salinity relates to the presence of water soluble salts in the soil, mainly of sodium, calcium and magnesium, which may be chlorides, sulphates and carbonates. Pure water is a poor conductor of electricity, but as more and more salt is dissolved, the conductivity increases. So measuring the electrical conductivity of the soil in water gives us an indirect measure of the salt content.

Salinity levels are usually determined by measuring the electrical conductivity of soil/water suspensions. Traditionally the electrical conductivity of saturated extracts (ECe) were used but this method is time consuming and difficult. Electrical conductivity is now determined more rapidly and easily on a 1:5 soil/water suspension (EC 1:5) and conversion tables between the soil texture and an appropriate multiplier factor have been derived. The units for electrical conductivity are in decisiemens per metre (dS/m) (Hazelton and Murphy 2007).

Depending on the soil testing laboratory, one of two methods is used to access soil salinity.

• Interpretation of electrical conductivity using the saturation extract (ECe (dS/m))
• Interpretation of electrical conductivity using a 1:5 soil/water suspension (EC 1:5 (dS/m))

5.1 Interpretation of soil salinity using the saturation extract (ECe (dS/m))
Conventionally, saline soils are defined as those having ECe value greater than 4 dS/m. Ranges have been set as per the table below.

Rating	ECe (dS/m)	Effect on plants
Non-saline	<2	Salinity effects mostly negligible
Slightly saline	2 – 4	Yields of sensitive crops affected
Moderately saline	4 – 8	Yields of crops may be affected
Highly saline	8 – 16	Only salt tolerant crops yield satisfactorily
Extremely saline	>16	Only very salt tolerant crops yield satisfactorily

Source: Cited in Hazelton and Murphy, 2007

There is a lot of information about the interpretation of ECe in regard to plant growth as shown in the above table. To convert the EC(dS/m) 1:5 soil/water electrical conductivity to an approximate value of ECe the following multiplier factors are used.

Soil Texture	Multiplier factor
Loamy sand, clayey sand, sand	17
Sandy loam, fine sandy loam, light sandy clay loam	12
Loam, loam fine sandy, silt loam, sandy clay loam	10
Clay loam, silty clay loam, fine sandy clay loam, sandy clay, light clay	9
Light medium clay	8
Medium clay	7
Heavy clay	6

Source: Cited in Hazelton and Murphy, 2007

Thus an electrical conductivity (1:5 soil/water) of (say) 0.35 dS/m of a loamy sand soil would give an ECe of 5.95 dS/m
and would be detrimental to sensitive crops, whereas the same electrical conductivity (1:5 soil/water) on a heavy clay soil would not.

Approximate yield reduction for some agricultural crops grown in the area in relation to ECe values

Plant sensitivity	Agricultural crop	No yield reduction1	25% yield reduction2	50% yield reduction2	75% yield reduction2
Very sensitive	Field and vegetable crops: Beans, Carrots, Celery, Peas, Strawberries	0 – 1 dS/m	About 3 dS/m	About 4 dS/m	About 6 dS/m
Sensitive	Field and vegetable crops: Cabbage, Cauliflower, Lettuce, Maize, Onion, Potato Forage crops: Bent grass, most Clovers Fruit crops: Most (except Figs, Olives)	1.2 – 1.9 dS/m	About 4 dS/m	About 6 dS/m	About 10 dS/m
Moderately tolerant	Vegetable crops: Broccoli, Cantaloupe, Cucumber, Spinach, Tomato, Watermelon Forage crops: Lucerne, Trefoil Fruit crops: Figs, Olives	2.0 – 3.9 dS/m	About 8 dS/m	About 10 dS/m	About 15 dS/m
Tolerant	Field and vegetable crops: Barley, Beets, Safflower, Sorghum, Soybean, Wheat Forage crops: Barley (hay), Perennial ryegrass, Trefoil, Wheat grass	3.9 – 8 dS/m	About 10 dS/m	About 15 dS/m	About 22 dS/m
Halophyte species	Includes: Saltbush and Saltmarsh species. Generally unsuitable for crop plants.	Above 8 dS/m

Note: These values are only approximate as there is variation in salt tolerance between varieties within species.
Sources: ¹Hazelton and Murphy (2007), and using generalised data cited in Brady and Weil (1999²)

Interpretation of soil salinity using a 1:5 soil/water suspension
Total soluble salts in a soil has been a popular way of expressing soil salinity and is measured by multiplying the electrical conductivity (EC 1:5) of a 1:5 soil/water suspension at 20°C which has been shaken for one hour by 0.33. Although TSS (total soluble salts) is considered an outdated unit you may wish to convert the EC 1:5 (dS/m) figures in this manual to TSS. However there is no exact relationship between electrical conductivity (1:5 soil/water) and total soluble salts as this depends on the different ionic conductivities of the various salts and the influence of the soil particles, but a very approximate value for the percentage total soluble salts is obtained by multiplying the electrical conductivity at 25°C (dS/m) by 0.33.

Soils with EC values less than 0.15 dS/m (TSS approximately 500 ppm or 0.05 %) are regarded as sufficiently low to have harmless salinity.

EC (1:5 dS/m)	Approx TSS %	Approx. TSS ppm	Interpretation
less than 0.15	less than 0.050	less than 500	low and harmless
0.15-0.2	0.050-0.067	500-670	slightly higher than normal
0.2-0.5	0.067-0.165	670-1650	higher than normal
0.5-0.75	0.165-0.248	1650-2480	considerably higher than normal (unfavourable)
0.75-1.00	0.248-0.330	2480-3300	high and harmful
1.00-1.50	0.330-0.495	3300-4950	very high and harmful
more than 1.50	more than 0.495	more than 4950	excessively high

Source: Adapted from Peverill et al. (1987)

These are broad interpretations and it should be realised plants vary considerably in their ability to tolerate soluble salts. Salt tolerance within a plant species varies markedly at different stages of growth, with germination and seedling stages generally being less tolerant. As many fertilisers are highly soluble, they also raise the salt content of soil, and can lead to salt damage to the roots. This applies particularly to young seedlings of salt sensitive species.

Note this table does not take into account soil texture and applies mainly to medium textured soils such as loams. Given the same EC (dS/m) reading, plants growing on light textured soils are up to three times more as affected by soluble salts as those growing on heavy textured soils.

6 Nutrients needed by plants

MACRONUTRIENTS	Form taken up by plants		MICRONUTRIENTS	Form taken up by plants
Nitrogen (N) 1	NO3-, NH4+		Copper (Cu) 2	Cu++
Phosphorus (P) 1	H2PO4-, HPO4--		Molybdenum (Mo) 1	MoO4--
Potassium (K) 1	K+		Zinc (Zn) 2	Zn++
Calcium (Ca) 1	Ca++		Manganese (Mn)	Mn++
Magnesium (Mg)	Mg++		Iron (Fe)	Fe++
Sulfur (S) 1	SO4--		Sodium (Na)	Na+
Carbon (C)	CO2		Chloride (Cl)	Cl-
Hydrogen (H)	H2O		Boron (B) 2	B4O7--
Oxygen (O)	O2		Cobalt (Co) 2	Co++

¹ Normally added as a fertiliser ² Sometimes added as a fertiliser

Nutrients needed by animals compared to nutrients needed by plants
Since animals eat plants, it is not surprising that much the same elements are needed by both. Exceptions are: sodium, which is an essential macronutrient for animal health, but not plant health. Similarly, the micronutrients selenium (Se), iodine (I) and fluorine (F) are essential for animal, but not plant health. Conversely, the micronutrient molybdenum (Mo) is essential for plant health (specifically, legumes), but not animal health.

6.1 Nitrogen (N)
Nitrogen (N) is a constituent of all proteins and is found in every living cell. Protein contains 6.25% nitrogen and in plants it is also a key component of chlorophyll. Although the atmosphere contains 79% nitrogen or about 300,000 tonnes above each hectare of land, plants cannot directly access this source and frequently show symptoms of nitrogen deficiency, such as poor growth and yellowing of leaves. The quantities removed by crops vary according to both yield and their protein content. Plants mainly take up nitrogen as nitrate (NO₃^-), but ammonium (NH₄⁺) can also be taken up.

Nitrogen sources
In nature the ultimate source of nitrogen is lightning in the atmosphere. A small amount of gas is converted to NO₃^- by electrical discharge and falls with the rain. But most nitrogen in the soil is ‘fixed’ by bacteria. The bacteria may exist freely in the soil (Azobacter) or be associated with leguminous plants such as peas, clover or lucerne (Rhizobium). The process of moving the nitrogen in the air to nitrogen compounds in the soil is called ‘nitrogen fixation’.

Nitrogen is also made available to the plant following the decomposition of dead plants and animals, and the addition of plant wastes such as straw or compost animal wastes such as urine and manure. However if the organic wastes are high in carbon and low in nitrogen (high carbon /nitrogen ratio) soil microbes compete with the plants for nitrogen. Examples of material with a high C:N ratio include straw, sawdusts and some composts.

Fertiliser sources of nitrogen include urea, potassium nitrate, ammonium nitrate, mixed fertilisers, ammonium sulphate, blood and bone and liquid ammonia. In Australia, apart from intensive cropping, relatively little nitrogen fertilisers are used on dryland pasture. Instead, the nitrogen requirement is generally met by the nitrogen fixing bacteria associated with leguminous plants.

Deficiency
Nitrogen deficiency is a potential for all crops excluding legumes, so signs of poor growth and leaf yellowing must be looked for. In pastures, the extreme contrast between growth on urine patches and the surrounding area often indicate nitrogen deficiency. In wheat lands, clover is grown in a rotation between crops and this is used to provide nitrogen for crop growth.

6.2 Carbon (C)
Organic matter is material in a soil which is directly derived from plants and animals, and supports most important microfauna and microflora in the soil. Through its breakdown and interaction with other soil constituents it is largely responsible for much of the physical and chemical fertility of a soil (Charman and Roper, 1991). Organic matter has a high surface area per unit weight compared to most other soil particles and is thus important for the water holding and nutrient retaining properties of the soil.

Organic matter and organic carbon are usually expressed as a percentage of the soil by weight. Care should be taken when presenting and interpreting results as to whether organic matter or organic carbon levels are indicated. In this manual organic carbon levels are used. Organic matter can be calculated from organic carbon. The most commonly used conversion factors vary from 1.72 to 1.9. However, for most practical purposes, simply doubling the organic carbon value provides a reasonable approximation of soil organic matter content.

As the following table shows, typical soil organic carbon levels vary with rainfall as well as intensity of cultivation: the higher the rainfall, the faster the turnover rate (by soil microbes). Cultivating the soil accelerates microbial activity which causes some of the carbon to be lost as carbon dioxide (CO₂). One of the main benefits of minimum tillage is it minimises loss of organic carbon as CO₂.

Soil organic carbon levels (% )

Interpretation	Low rainfall	(<500 mm)	High rainfall	(>500 mm)
	Crops	Pasture	Crops	Pasture
Low	0.09	1.7	1.45	<2.9
Normal	0.09 – 1.4	1.7 – 2.6	1.45 – 2.9	2.9 – 5.8
High	>1.45	>2.6	>2.9	>5.8

Source: Hall R and Hollier C (1995) Soil Sense Field Day Notes for the Chiltern Valley Landcare Group. March 16, 1995, Rutherglen Research Institute.

6.3 Calcium (Ca)
Calcium is required for cell walls and is necessary for normal cell division and is associated with proteins, nucleic acids and enzymes. As a result, calcium deficiency results in the disintegration of roots and the terminal portion of shoots.

Calcium is also part of the genetic coding material of the nucleus. As calcium is abundant in most soils, deficiency symptoms are rarely seen in the field, although it can be induced through excessive use of nitrogenous fertilisers, particularly in summer (nitrogen-induced tip-burn). High calcium is also beneficial to soil structure, which is why gypsum (calcium sulphate) is applied to (sodic) soil.

Soil test result	Symptoms
Less than 0.5 cmol(+)/kg	Very deficient. Stubby, weakly branched and discoloured roots and fresh shoots dying at the growing point
Between 0.5 and 0.7 cmol(+)/kg	As above but less severe
Between 0.7 and 1.0 cmol(+)/kg	Symptoms indicate Ca deficiency occurs furthest from the main flow of water
Above 1.0 cmol(+)/kg	Above deficiency level

Source: NSW Agriculture, Leaflet No 7

6.4 Magnesium (Mg)
Magnesium along with nitrogen is found in chlorophyll, the green colouring in plants. Chlorophyll is necessary for the conversion of carbon dioxide in the air to carbohydrates. It also forms soluble organic salts, which help maintain cell rigidity. Although plant deficiencies are rare, sheep and cattle may be unable to get enough magnesium from pasture resulting in an often fatal disorder called ‘grass tetany’ or hypomagnesemia. High potassium in pastures also increases the risk of hypomagnesemia.

Grass tetany has been the main cause of deaths of adult beef cows on farms in south-eastern Australia over the past 40 years (DPI-Vic Agnote AG 0579, June 2007).
It is generally adequate in soils as clays typically contain about 0.05 to 1% magnesium. As these clays weather, the magnesium is released and is held on exchange positions (see section on cation exchange capacity). Plants can normally access this supply of magnesium as its roots extend into the subsoil. Magnesium may be added to the soil as dolomite (CaMgCO₃). Some compound fertilisers also contain Mg.

6.5 Potassium (K)
Potassium is an essential constituent of all living cells and is the major nutrient in plants. Potassium plays an important part in many physiological processes in the plant such as respiration, transpiration and the synthesis of carbohydrates and sugars. It is also the major constituent in cell fluid and maintains cell rigidity. Plants take up potassium, as they do all nutrients, from soil solution. Under intensive agriculture (vegetable production and dairying), potassium fertiliser is applied routinely to maintain an adequate supply for plants.

Sources
In general, the clay minerals, mica and illite, contain good reserves of potassium. Some young soils derived from basalt and granite may also contain unweathered potassium, as feldspar.

In high-rainfall regions (more than 700 mm), artificial fertilisers such as potassium chloride (muriate of potash) and potassium sulphate are commonly used to maintain soil reserves, particularly after heavy cropping or fodder removal.

Deficiency
Deficiency symptoms are poor growth, leaf scorch and leaf spotting, particularly in older leaves. Dry vegetative growth contains 1-4% potassium so leafy crops remove quite large amounts.

South of the dividing range, particularly where rainfall is above 700 mm, Victorian soils generally contain low amounts of potassium containing minerals. These soils, when cropped (vegetables or hay cutting) become potassium deficient.

In Northern Victoria, the total potassium content of a soil may be over 1.5% whereas most southern Victorian soils, (Otways and Strzeleckis excluded), total potassium is generally less than 0.5%. However most of this potassium is held rigidly by the clay minerals and is relatively unavailable to growing plants.

Available Potassium
The deficiency levels quoted below for soil samples taken at 0-10 cm are a useful guide for pastures in most circumstances. If exchangeable cation data are given (see Section 1.7), the potassium value (cmol(+)/kg ) may be multiplied by 390 to give the potassium level in the soil in parts per million.

Interpretation	Sand	Sandy loam	Clay loam	Clay
Low	less than 50	less than 80	less than 110	less than 120
Deficiency level	50-100	80-120	110-160	120-180
Moderate	100-150	120-200	160-250	180-300
High	greater than 150	greater than 200	greater than 250	greater than 300

Source: Brown et al. (1982)

6.6 Aluminium (Al)
Aluminium (Al) comprises about 8% of the earth’s crust compared with <1% for phosphorus and 4% for calcium. Most of the soil clay minerals contain aluminium, but it is usually not until soil pH(CaCl₂) falls below 4.8 [pH(H₂O) <5.5] that aluminium is ‘readily measurable’ in the soil solution and on exchange sites, and can become toxic to plant growth. Aluminium affects plant roots by causing lateral and tip root thickening, greatly reducing the development of fine branching roots and root hairs and reducing, or excluding, the uptake of other cations. Plants vary in their tolerance to concentrations of aluminium.

7 Cation Exchange Capacity (CEC) and Effective Cation Exchange Capacity (ECEC)
The cation exchange capacity (CEC) is a measure of the soil’s ability to absorb and to hold cations (positively charged ions). The four most abundant cations are calcium (Ca²⁺), magnesium (Mg²⁺), potassium (K⁺) and sodium (Na⁺), and if the soil is acid, hydrogen (H⁺). The cations manganese (Mn²⁺), iron (Fe²⁺), copper (Cu²⁺) and zinc (Zn²⁺) are usually present in amounts that do not contribute significantly to the cation compliment. If the soils are strongly acid, the exchangeable aluminium and manganese are added to the cation exchange capacity and this is called ‘Effective Cation Exchange Capacity’ (ECEC). This latter figure is used when calculating the exchangeable sodium percentage of acid soils.

The cations have a positive electrical charge and are held on the negatively charged surfaces of clay minerals and organic matter. These cations can be exchanged for other cations, for example one Ca²⁺ cation can be exchanged for two Na⁺ cations, and are therefore said to be ‘exchangeable’ cations. Some clays, eg montmorillonite, have a greater negative charge than others, eg kaolinite, but the types of clay in the soils described in this manual have not been determined. Little can be done to improve the soil clay content. However organic matter has a high ability to hold cations and additions of manure, crop waste and other organic materials will improve the cation exchange capacity, albeit temporarily.

A high cation exchange capacity means a soil has good nutrient cation retention. Soils high in clay and organic matter have a high cation exchange capacity and can retain fertiliser cations. In contrast, sandy soils, which are low in clay and/or organic matter, have a low cation exchange capacity so fertiliser is more easily leached.
The cation exchange capacity of a soil is a major controlling agent of stability of soil structure, nutrient availability for plant growth, soil pH and the soil’s responsiveness to fertilisers and other ameliorants (eg lime, gypsum and dolomite).

Anions are also present in a soil, being held on positively charged surfaces of oxides, iron and aluminium. An example of an anion is H₂PO₄^-, which denotes the usual form of phosphorus in a soil when superphosphate is added.

Nutrient status
The exchangeable cation capacity may be used as a guide to the nutrient status of the soil. This is calculated as the sum of exchangeable calcium, magnesium and potassium (in cmol(+)/kg) and can be used as a rough guide to availability of nutrients in general. The categories used are given in the table below.

8 Soil constituents
This table sets out the components of soil, their surface area per gram and their negative charge, i.e. ability to hold cations, eg calcium (Ca), magnesium (Mg), potassium (K) and sodium (Na).

Component	Size (mm)	Surface area (m2 /g)	Cation exchange capacity (cmol (+)/kg)
Gravel	more than 2.0		nil
Coarse sand	2.0 - 0.2	0.01	nil
Fine sand	0.2 - 0.02	0.1	nil to very slight if mica present
Silt	0.02 - 0.002	1.0	nil to very slight if mica present
Clay	less than 0.002 *	5 - 750 *	varies according to clay type - kaolinite (a non-swelling clay): about 8 illite: about 30 montmorillonite (a swelling clay): about 100 vermiculite: about 150
Iron, aluminium and manganese oxides and hydroxides		100 - 200	varies according to pH about +5 at low pH (i.e. anion adsorbing) to about -5 at pH 7 (i.e. cation adsorbing)
Other oxides (very little) (titanium and zircon)
Water *
Air*
Dissolved salts
Undissolved salts
Colloidal organic matter		very high surface area	varies according to organic matter type and pH, up to 300 (i.e. strongly cation adsorbing)

Source: I. J. Sargeant, unpublished lecture notes, Monash University.

The components in italics are the most reactive and hold most of the nutrients and water. The high surface area largely contributes to the water retaining ability of the soil.

* Soil air and soil water combined make up about 40 - 50% of the volume of surface soil. Even apparently dense clay subsoil will contain about 35 - 40% pore space which is occupied by either soil air or soil water.

9 Exchangeable Sodium Percentage (ESP)
This is calculated as the proportion of the cation exchange capacity occupied by sodium ions and is expressed as a percentage.

If the ESP is less than 6%, the soil is non-sodic, from 6-15 the soil is sodic and greater than 15 the soil is strongly sodic. These sodium dominated clays have a tendency to swell on wetting. They are also likely to be dispersive which means the soils are structurally unstable and disperse in water into their basic particles i.e. sand, silt and clay. The fine clay particles that have dispersed clog up the small pores in the soil, degrading soil structure and restricting root growth and water movement.

10 Calcium: Magnesium Ratio (Ca:Mg)
Ca:Mg ratios were thought to be important for optimal plant growth but it is now known this ratio is not as important as first claimed, with research results showing a variation between 1 and 20 in Ca:Mg ratios of little consequence in agricultural production. However, a low Ca:Mg ratio in association with high levels of exchangeable sodium may enhance soil dispersion. (NSW Agriculture, Leaflet No 7).

Soils with a Ca:Mg ratio of less than 0.1 are classified in the Australian Soil Classification as being magnesic.

11 Trace elements
The relationship between chemical tests for trace elements and plant response is generally poor. Nevertheless many soil testing laboratories do tests for trace elements and make fertiliser recommendations on the basis of these tests. The usual method of determining whether a micronutrient is deficient is to undertake plant tissue analyses. The selection of plant parts to be analysed and the stage of growth is critical to correct interpretation of the results.

11.1 Copper (Cu)
Copper (Cu) is a component of many enzymes involved in complex reactions in plants. Cu deficiency is more likely in high rainfall areas, particularly on both calcareous and acid sands and gravels, although it can occur in heavier clay loams. Copper deficiency has been reported in the sandy soils of the ‘Red Gum Plains’ in Gippsland.

In animals, copper is required for body, bone and wool growth, pigmentation, myelination of nerve fibres and blood cells.

As far as animal health is concerned, there is a well known interaction between the levels of Mo and Cu in the pasture with high levels of Mo requiring supplementary Cu.

Only about 2 kg of copper as copper sulphate per ha every 5 - 7 years is required to overcome the deficiency.

WARNING: Do not apply copper if the weeds Paterson’s Curse or Heliotrope are present.

11.2 Zinc (Zn)
Zinc (Zn) is required for the production of the plant hormone auxin, which promotes stem elongation and leaf expansion. Cu and Zn deficiency in soils often go hand in hand, and can be overcome using 2 kg of zinc sulphate every 7 or so years. Zinc deficiency does not appear to be a major problem in East Gippsland, and there have been some negative growth responses in pasture experiments. Therefore, this trace element should only be applied if plant tissue analysis has indicated a deficiency.

11.3 Molybdenum (Mo)
Mo is required by plants to convert nitrates to proteins. As well the fixation of atmospheric nitrogen by Rhizobium bacteria in legumes (eg clover, lucerne) depends on the presence of Mo. Mo deficiency often occurs in the sandy soils around Bairnsdale, particularly those on the ‘Red Gum Plains’. To overcome the deficiency, sodium molybdate is generally applied with the superphosphate. Liming acidic soils generally increases the availability of Mo and growth responses attributed to liming are often due to increases in Mo availability.

Molybdenum availability in soils is related to the soils acidity, the stronger the acidity the lower the availability.

In sheep and cattle Mo combines with sulphur in the rumen to form compounds which reduce the availability of copper. Thus where copper deficiency has occurred in livestock, or could be induced by molybdenum fertilisers, it may be advisable to include some copper with the application of molybdenum.
Molybdenum should be applied with fertiliser on responsive soils (where soil pH is less than 5.7) every 5-6 years at the rate of 50-60 g/ha. Copper is normally applied at the same time, at the rate of 1-2 kg/ha since molybdenum can interfere with copper metabolism in stock.

WARNING: Excessive molybdenum can be harmful to stock. Do not apply fertiliser containing molybdenum on more than 25% of farm annually. Do not graze for four weeks after application.

Warning: Do not apply copper if the weeds Paterson’s Curse or Heliotrope are present.

11.4 Manganese (Mn)
The role of Mn is poorly understood but it appears to have a major role in photosynthesis and respiration. It is also essential for nitrogen transformations in both microorganisms and plants.

The chemistry of manganese in the soil is exceedingly complex. The manganese supply for plant growth is normally adequate on acid soils. Thus in south eastern Australia manganese deficiencies are rare and have generally only appeared where naturally acidic soils have been made alkaline by liming. Manganese toxicity is more common, and has been recorded in north-eastern Victoria and in stock grazing on lupins. Manganese toxicity has not been recorded as a problem in Gippsland.

11.5 Iron (Fe)
Fe is also a constituent of chlorophyll and when plants are deficient the leaves become much paler than usual. Although Fe is abundant in most soils, the presence of free lime in a soil may restrict its uptake, and a plant disorder called lime induced chlorosis results. Iron chelates can be applied to the soil to overcome the deficiency. Foliar sprays are particularly effective. There is no evidence Fe deficiency occurs in pastures or in livestock in Victoria.

11.6 Boron (B)
Boron is one of the most commonly deficient of all the micronutrients. Its availability is greatly influenced by soil pH and is most available in acid soils. At higher pH values, boron is less easily utilised by plants and over liming can result in a boron deficiency. This element plays an important role in the uptake and use of calcium within the plant and death of the growing points of the plant occurs as a result of its deficiency. Boron is also important in protein synthesis and associated nitrogen metabolism.

Carbohydrate metabolism is also concerned with this element. Boron deficiency has been recognised all over the world. Seawater contains a relatively high concentration of boron and soils derived from the marine sediments, unless subjected to prolonged and extensive leaching, commonly contain a good reserve of the element. In Victoria often the problem is not a boron deficiency but excess. Although boron plays a vital role in plant nutrition, the range between deficient and toxic levels is so small great care must be taken with any recommendations for treatment of boron deficiency.

Acidic sandy surface soils cover most of the Red Gum Plains and boron levels were probably initially low in these soils. Unfortunately it is easily leached from acid sandy soils and boron deficiency can be a matter of a low supply rather than low availability. As the soils were initially acidic the boron levels were generally adequate and of the ten field trials conducted in East Gippsland before the early 1980s, only one showed deficiency symptoms. Since then, the liming of soils has been a common practice and this, together with the naturally low boron levels in the soil, could have lead to deficiency symptoms. As for other trace elements, the application of boron fertiliser should be guided by plant tissue analyses.

11.7 Cobalt (Co)
Co is required by the Rhizobium bacteria found in the nodules on the roots of legumes where it is required for vitamin B12. When Co is insufficient legumes show the typical symptoms of N deficiency, including the yellowing of leaves and poor growth.

Sheep and cattle can synthesise this vitamin from dietary Co and in Co deficient areas they may suffer from a disorder called ‘wasting disease’, even though the pasture is growing vigorously. Wool production is also seriously affected. Cobalt deficiency has been reported on the soils of the ‘Red Gum Plains’ but rather than adding Co fertilisers, it is best supplied orally in pellet form or as drenches or licks.

11.8 Sodium and chlorine (Na and Cl)
Sodium chloride is common salt. In Australia deficiencies of Na and Cl are unknown as far as the plant is concerned. However, plants can take up both Na and Cl in quite large quantities and the Na concentration in pasture is frequently over 0.5 percent. Some species take up little Na and when this occurs, or when the soil itself is low in Na, grazing animals may show a craving for salt, particularly after giving birth or when lactating.

11.9 Selenium and Iodine (Se and I)
Selenium deficiency has been reported in the sandy soils of East Gippsland as well as rare instances of iodine deficiency. These elements are not needed by plants, and are best supplied as animal supplements. However, selenium may be incorporated into fertiliser and applied as a broadcast application. In some cases, this is a more practical alternative to animal supplements.

Warning: Selenium toxicity can be induced in stock through excessive application of Se in fertiliser. It should only be applied to pasture where there is a demonstrated history of Se deficiency in stock.

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Acknowledgements/thanks

This document is a revision of Ian Sargeant and Julianne Sargant (2005) Sustainable Soil Management: A reference manual to the major agricultural soil of the Bairnsdale and Dargo Regions. Department of Primary Industries, Bairnsdale, Victoria.

The Department of Primary Industries would like to acknowledge the significant contribution of Ian Sargeant (Soil Consultant) in undertaking the interpretative analysis required to develop the soil landform maps within this manual.

The following people also contributed:

Project Management: Wayne Burton Department of Primary Industries, Heather Adams¹
Field Survey: Ian Sargeant², Soil Consultant, 5 Railway Parade North, Glen Waverley
Soil Pit Descriptions: Ian Sargeant, David Rees¹, Doug Crawford¹
Text: Ian Sargeant
Map Products: Brett Mitchard¹
Photographs: Ian Sargeant
Glossary of Terms: Mark Imhof¹
Editing Advice: Trish Lothian¹
Booklet formatting: Griffin Graphics

¹ Department of Primary Industries
² Ian Sargeant, Soil Consultant, 5 Railway Parade North, Glen Waverley

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