and Geology-University of Ballarat

Bulart Land Management Group and

Geology- University of Ballarat

Bulart Landcare Research 1997- 1998 Peter Dahlhaus, Tony Davidson, Richard MacEwan, Vince Morand,

Erica Nathan, Nathan Robinson and Brendan Cassens

Bu/art Landcare Research 1997 - 1998

Acknowledgments

Our sincere thanks to the members of the Bulart Land Management Group for their continued support of the Landcare research . Over the past six years, the group members have shown trust and openness in allowing students to roam their properties. Their generosity in providing hospitality and research assistance is greatly appreciated .

In particular, we acknowledge the efforts of Liz and Leo Cummins in keeping the connection between the Bulart Land Management Group members and the University researchers.

Thanks also to the staff of the Cavendish Tele-Education Centre . They have taken on a strategic role in making the results of the research available on-site. We believe that they are leading the way in bringing information technology to the bush .

About the authors

• Peter Dahlhaus is Senior Lecturer in Geology at the University of Ballarat. He has been involved in the research program at Bulart from the very beginning.

• Tony Davidson created the Bulart GIS while he was employed by the University of Ballarat. Although Tony now works with the Tasmanian Department of Primary Industries, Water and Environment, he is still active in the Dundas GIS developments.

• Richard MacEwan is Senior Lecturer in Land Rehabilitation at the University of Ballarat, and has been involved with the Bulart Landcare research from the start. Richard has run soil courses for the Combined Dundas Land care as well as Hamilton WRIST.

• Dr. Vince Morand, a geologist with the Geological Survey of Victoria , has been involved in the mapping around Bulart. Vince is a former Lecturer in Structural Geology and an Academic Associate at the University of Ballarat.

• Erica Nathan completed her research on an investigation of the historical evidence of landscape changes and dryland salinity. Erica's Master of Applied Science thesis, titled "Dundas landscapes and dryland salinity", is available through the BLMG and the Combined Dundas Landcare.

• Nathan Robinson completed an extensive research project on the soils of the Bulart area for his Bachelor of Applied Science (Honours) in 1998. This work followed his project on groundwater around Bulart in 1997. Nathan's work was carried out under the supervision of Richard MacEwan and Peter Dahlhaus

• Brendan Cossens is currently completing his Bachelor of Applied Science (Honours) on the groundwater system of the eastern Dundas Tableland. His work is being supervised by Peter Dahlhaus and Dr Kim Dowling.

Bu/art Land Management Group & University of Ballarat - Geology

Bulart Landcare Research 1997 - 1998

1.0 Introduction

1.1 About the Landcare research program

The Bulart Land Management Group (BLMG) and the University of Ballarat (Geology) have been involved in collaborative research into Land Degradation issues since 1993. Initially, the research was focused on salinity, but has since expanded to include other related aspects of the environment. Over the past three years, most of the research has been directed to soils and hydrology.

Funding for the projects has been raised through Salinity and Land care Grants. Most of the research has been done by geology students at the University who have used the work for their major research thesis in their Bachelor of Applied Science (Honours) degrees. In addition , some independent research has been done by university academic staff using funds obtained through university research grants, the Department of Agriculture, and Landcare Grants through the Combined Dundas Tablelands Landcare.

The output of all the work is documented in various reports , theses and conference papers listed at the back of this report.

1.2 About this report

This report, the fourth in this series, is intended to bring the Bulart Land Management Group (BLMG) members up to date on the key findings of the research. The report has six sections:

• Historical evidence for salinity in the Bulart area .

• Landscape evolution of the eastern Dundas Tablelands.

• Groundwater.

• The soils of the Bulart area.

• The Bulart GIS .

• Conclusion.

The information has been summarised from many research projects. Not all aspects of the research have been presented in this report. If readers wish to scrutinise the details of the research , they should refer to the original theses or scientific papers (listed at the back of this report) . Copies of most of the research documents should be locally available through the BLMG or the Combined Dundas Landcare. All of the original research data and reports are also held by the University of Ballarat.

Bulart Land Management Group & University of Ballarat - Geology


2.0 Historical evidence for salinity in the Bulart area

The salinity on the Dundas Tableland has long been considered to be related to European settlement. This assumption seems to derive from squatter John Robertson 's observations, of the saline springs killing the native grasses in the Dundas area only nineteen years after settlement. However, the work by Erica Nathan shows this assumption is false , mainly because:

• The first maps indicate that some streams were salty at the time of European settlement. The area of the Koroite Rivulet map (Historical Plans, Glenelg , 1843) shown in Figure 1 is the Young Creek and Hawkins Creek area. It was not held under a squatting license at the time of survey, or if so. was an unoccupied part of the Whytes' Konongwootong run . Similarly, a survey in early Spring of 1842 of the Wannon River, downstream from Riley's Kenilworth Station , adjacent to present day Cavendish, recorded it to be brackish in some holes. Surveys of the Glenelg River and its tributaries from the late 1840s (Historical Plans, Glenelg , 1848-1852) clearly specify fresh water, which by implication , indicates the presence of poor quality water.

• Casual references to the saline quality of the summer water supply (Glenelg and Wannon Rivers) and to saline groundwater, are noted in the letters and diaries of the first European settlers.

• To some extent, the 'problem' of salinity is related to the size of the property . The historical record tells us that salinity was not seen as a problem until land subdivision significantly reduced the size of properties. During the 1920s, and again in the 1950s, the number of holdings on the Dundas Tableland increased. There is some historical evidence that the actual extent of salt-affected land had not increased significantly from the 1870s to the 1950s, but that the existing sites became a bigger problem on the smaller properties.

Although tree-clearing has been blamed for salinity, it had never been put into the framework of historical time. Erica's work has now shown :

• Banksia (Banksia marginata) was the most widespread tree on the tablelands, sharing numbers with Red Gum (Eucalyptus camaldanensis) . Swamp Gum (E. ovata) , Manna Gum (E. viminalis) , Stringybark (E. baxten) , Casuarina (AIIocasuarina verticillata) and possibly Cherry (Exocarpos cupressiformis) . Blackwood (Acacia melanoxylon) , Black Wattle (Acacia mearnsil) and Box (Bursaria spinosa) also get a mention.

• This diversity of tree species and grasses was characteristic of the Aboriginal and earliest European settlement landscapes. However, only a few species were left by the end of the century.

• The average number of Red Gums per acre increased during the decades of earliest settlement (1840 - 1870) relative to previous and later time periods (Figure 2) .

• Du ring the 1920 - 1950 period , there was a massive decrease in the average number of Red Gums per acre , mostly due to milling contracts.

• Since the 1890s, the variety and density of pasture species has declined , with the gradual transition from the predominantly native pastures pre-1950 to more exotic pasture species.


Bulart Landcare Research 1997- 1998

GUM? (error on the original map)

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Figure 1. Detail from "Survey of Koroite Rivulet part of the River Wan non or Karrawal/a and some of the tributary" 1843, showing salt springs. (Historical Plans, Glenelg 1843. Surveyor unknown).

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Figure 2. Estimated changes to the number of Red Gums per hectare.


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All units except the Pliocene basalt and the Grampians Group in the Grampians, Black and Dundas Ranges are covered by ferruginised regolith, with the older rocks exposed mainly in stream valleys.

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Figure 3. Geology of the eastern Dundas Tableland (drawn by Dr. Vince Morand, 1999)

Bu/art Landcare Research 1997- 1998

3.0 Landscape evolution of the eastern Dundas Tablelands

The combined efforts of mineral exploration companies, government surveys, and university research has now re-written the geology and landscape evolution of the Dundas Tableland. The major portion of the work has been carried out over the past two years, under the Victorian Initiative for Minerals and Petroleum (VIMP). This work is still on-going, and is currently being conducted in the Bulart region .

Geology is based on observation and deduction . Geologists try to match what they see in the landscape with what they understand of the past and present. It's understandable that theories change , but hopefully, they will always move closer to the correct explanation.

2.1 Current theory

It appears that elements of the present landscape were already in place in the Devonian period (about 400 million years ago). The Rocklands Rhyolite (dated as 410 million years old) occurs at a lower topographic level than most of the Grampians Group sandstone, even though it is younger than the Grampians Group. As there has been no significant folding or faulting of the Rocklands Rhyolite since it was deposited, this suggests the surprising conclusion that the Grampians, Black and Dundas ranges existed 410 million years ago when the rhyolites were erupted . The Dundas Range appears to have blocked the lava flow to the southwest, as there are no outcrops of rhyolite immediately southwest of the range, but rhyolite outcrop extends west around the northern and southern ends of the range. There is no evidence that the Rocklands Rhyolite was ever covered by a significant thickness of younger rocks.

From the Middle Devonian (about 380 million years ago) to the Cretaceous (about 140 million years ago) the eastern Dundas Tableland was apparently above sea level, with little deposition or erosion. During the Cretaceous the Dundas Tableland may have been covered by the sandstone and mudstone rocks of the Merino Group, most of which was stripped off before the Miocene (about 15 million years ago) . Alternatively the tableland came into existence at this time and received no sediments except around its northwest and southern boundaries.

However, a rise in sea-level about 30 to 15 million years ago led to deposition of the Heytesbury Group limestone over at least the northwest and southern fringes of the tableland. In addition , marine fossils of similar age have been found in ironstone at Englefield , near the centre of the Dundas Tableland , and in the ironstone at the Boral Quarry on the southern boundary. This raises the possibility that the whole tableland may have been submerged beneath the sea during this time interval.

The sea then retreated for a few million years, and later returned , presumably during the Pliocene Uust 2 or 3 million years ago). The last retreat of the sea left behind a series of sandy beach deposits, known as strand lines (shown in Figure 3) . As these do not reach the centre of the tableland , it appears that the tableland was a topographic feature at the time. On current evidence, the southern and western part of the BLMG area was covered by the sea during the last incursion. Bulart may have been at the shoreline of a peninsula that was formed from the Black Ranges to the Dundas Range.

A series of sea level drops during the ice ages of the past million years or so would have exposed most of western Victoria to erosional conditions and created the present-day valleys of the Glenelg and Wan non river systems. However, uplift of the Dundas Tableland , including parts covered by strand lines, to 200-250 m above sea level must have occurred after the strand lines were deposited, so this uplift must be less than 3 million years old . This youngest uplift has probably created most of the valleys of the streams seen in the western Dundas Tableland. Headward erosion



4.0 Groundwater

Since groundwater levels rise and fall in response to the wet and dry seasons, it may take decades of monitoring before any underlying trends become obvious. The groundwater levels around the Bulart area have been monitored for the past six years (1993- 1999). Over this time frame, there has been no obvious trend , such as steadily rising or falling groundwater levels. This means that, over the past few years at least, recharge and discharge have generally been balanced .

Research on the groundwater system has now moved to a wider field . Brendan Cassens, a Geology Honours student, is currently investigating the groundwater system of the eastern Dundas Tableland . A 'snapshot' survey of groundwater levels was conducted , with the assistance of Landcare Group members, during one week of July, 1998. The preliminary results of this survey show that the groundwater in the Bulart area generally flows towards the Wannon River in the south.

The groundwater chemistry was investigated from eight bores scattered over the eastern Dundas Tableland. Generally, the chemistry of the groundwater is the same in all the bores tested to date, including the Bulart bores tested in 1994. The diagram shown in Figure 4, called a Piper plot, shows the chemistry of the groundwater of the Bulart area compared to the rest of the eastern Dundas Tableland and seawater. A Piper plot is used by hydro-geologists to characterise groundwater using its chemical composition. The plot shows that the groundwater is dominated by sodium chloride, with a similar composition to seawater. This usually indicates that the groundwater has spent a long time moving through the system (or has recently been in contact with seawater) . The similar chemistry of all the water tested to date also indicates that the groundwater from different depths is connected through the fractures in the rock.

Another interesting question about the groundwater has emerged from Erica Nathan's research. An unusually long and continual record exists for a gauging station on the Glenelg River near Balmoral (S .I No 238201). Dr. Rory Nathan, a Principal Hydrologist at Sinclair Knight Mertz, analysed this record using a parametric method, the Generalised Additive Model, to estimate time trends. Its interpretation is complicated by the Moora diversion scheme in the 1920s and the construction of Rocklands Reservoir in 1950, so the pre-dam record was treated differently to the post-dam record. In Figure 5, the trend line represents the change in streamflow over a period of 60 years, with the influence of the climate (rainfall, etc.) having been removed (R. Nathan , pers. comm.). The time component of trend (y-axis) is measured as the volume of stream flow divided by the area of the catchment, expressed as mm/yr

An interpretation of the streamflow analysis requires an understanding of the landuse history. Surprisingly, streamflow steadily decreases during the period of most active tree clearance and most depleted pasture, from the 1920s. The trend line shows the streamflow (ie. runoff and groundwater baseflow) beginning to decrease in the early 1900s and remaining in sharp decline for fifty years. If the accuracy of the trend analysis is assumed, it does not support the theory that tree clearing has increased the groundwater recharge, since there is a decline in discharge to the river. The decrease in runoff is also mystifying, and may be due to increased storage, due to the construction of farm dams, or an increased evaporation direct from the soil.

A model based on increased soil waterlogging and lateral movement of water through the upper regolith (ie. throughflow and interflow) can better account for the observed increase in saline affected areas (Figure 6). This process is better supported by the land-use history than the groundwater recharge model. In fact,



has not yet reached the eastern part of the tableland, to the upper reaches of the Glenelg and Wan non rivers. The southern part of the eastern Dundas Tableland has been covered by basalt flows that covered the ancestral Wan non River and caused it to reorient itself along the northern edge of the flow.

2.2 Significance of the new interpretation

The impact of this new interpretation of the evolution of the landscape has not yet been completely thought through . The age of the landscape and the deep weathering of the rhyolite provide millions of years and plenty of storage for accumulation of salt. It's possible that some of the salt stored in the deeply weathered regolith is sea-salt, given that the sea was close to , if not covering , Bulart.

The new information about the geology also provides a new interpretation for groundwater flow. It now seems likely that the sandstone only underlies the rhyolite immediately east of the Dundas Range, rather than all the way to the Grampians. If this is true , then groundwater flow through the sandstone may hit a barrier under the rhyolite , forcing upward pressures. No doubt, further research will clarify the interpretation.


Legend

• Bulart bore information on government database

• Bulart bore sampled by University

• Eastern Dundas bore sampled by University

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Figure 5. Time series trend for the Glenelg River at Balmoral1890- 1950 (Generalised Additive Model by Dr. Rory Nathan, 1997)


because of the influence of waterlogging in depressing agricultural productivity and the significance that waterlogging has in increasing lateral throughflow processes and subsequent area of salt affected land, it must be seen that regional soil management is an issue of greater immediate importance than salinity. Efforts should be directed to improvement of soil structure and to increasing root growth and soil water use as well as to decreasing waterlogging . The latter may be achieved either through direct soil improvements or through the installation of agricultural drainage.

Thick regolith development on the plateau provides large water holding capacity with preferential paths for water movement to C horizon. Perched water in the A2 (E) horizon of the sol um. Saturation provides head for lateral water movement down slope.

Thinner regolith on erosiona I slopes. Break of slope seepage. High volume of lateral flow.

Thicker alluvial soils, waterlogged by combined interflow, surface runoff and saline groundwater discharge

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Figure 6. A conceptual model for waterlogging and salinity at Bulart. (from: Dahlhaus & MacEwan, 1997; Fawcett & Dahlhaus, 1998)



5.0 Soils of the Bulart Area and their properties

In 1998, an extensive soil-sampling program was conducted to provide an indication of the variation in soil fertility across the BLMG area. The program, carried out by Nathan Robinson, involved sampling the topsoil (top 10 em of the soil profile) and conducting chemical and physical tests on samples. The soil sampling was conducted in May and early September. Over 380 samples were collected from sites randomly chosen that were representative of the soi l-landscape units.

Throughout the sampling program, geographic coordinates of samples collected were recorded , so that the data could be entered on the Bulart GIS. Topographic maps of 1 :25 ,000 scale were used as base maps upon which soil sample sites were marked . The maps would have errors (±50 metres) smaller than that of an uncorrected Global Positioning System (GPS).

The soil samples were tested for their phosphorus availability (Olsen P), potassium availability (Skene K) , salinity (Electrical Conductivity - EC), acidity (pH in water (H20) and calcium chloride (CaCb)) , organic carbon content (Loss on Ignition - LOI) and their soil texture.

5.1 Phosphorus

The levels of available phosphorus for the Bulart region range from 3.5 to 57 .3 mg/kg. The mean value of 11.4 mg/kg indicates a marginal range for plant availability (Table 1 ).

Dryland Pastures and Irrigated Pastures and Horticultural Crops

Crops Crops

Low <8 < 12 < 15

Marginal 8-12 12-18 15-20

Moderate 13-18 19-25 21-40

High > 18 > 25 > 40

Table 1. The AG-PLUS laboratories classification scheme for Olsen P.

There are a number of factors that control phosphorus availability, such as:

1. Soil type

2. Soil acidity (pH)

3. Soluble iron

4. Presence of iron, aluminium and manganese minerals

5. Available calcium and calcium minerals

6. Amount and decomposition of organic matter

7. Activities of micro-organisms

The low availability levels for phosphorus is most likely related to the highly acidic soils of the region , although waterlogging also reduces phosphorus availability. Commonly , phosphorus levels are higher in summer to early autumn with decreased concentrations in winter and spring , which corresponds to the sampling time.

The contour map of Olsen P (Figure 7) shows the distribution of plant available phosphorus. Although not proven, it appears that the distribution of phosphorus most likely corresponds to landforms, position in landscape, the degree of leaching and thickness of the weathered rock.


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Figure 7. Bulart soils- Available Phosphorus (Olsen P values)

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5.2 Potassium

Potassium (K) , an essential element for plant growth, occurs in different forms in the soil. It can be non-exchangeable (slowly released) , exchangeable and solution (free K+) potassium. Only the exchangeable K and solution K occurs as 'available' K that can be taken up by plants. Based on Table 2, the available Kin the soils of the Bulart region is low for sandy and clay loams, with a mean value of 69.

Sands Sandy loams Clay loams Clays

Low <50 < 80 < 110 < 120

Marginal 50-100 80-120 110-160 120-180

Moderate 101-150 121-200 161-250 181-300

High > 150 > 200 > 250 > 300

Table 2. The AG-PLUS available K classification for different soil textures.

The excessively low potassium levels for the BLMG area are shown by the contour map of Skene K (Figure 8) .

Plants absorb large quantities of potassium, and the harvesting of crops and production of hay is probably significant in depleting potassium from soils of the Bu lart region . Potassium is more easily leached than phosphorus, and is a major contributing factor in removing potassium from topsoils , especially where waterlogging occurs.

The available potassium concentrations are generally highest in summer and autumn, and decrease with the onset of plant growth in winter and spring . As sampling was conducted during May and September, available potassium levels are likely to have been highest during late autumn. With the 1998 autumn break late in the season, the May samples should represent the highest available potassium levels. September sampling occurred when plant growth is nearly at its peak, lowering potassium levels.

The levels of available potassium are cause for concern . Not only are the levels below the optimal required for adequate plant growth , but the levels measured in the Bulart soils are all considered to have 'low' quantities of available potassium

5.2.2 Comparison to Airborne geophysics

The Australian Geological Survey Organisation (AGSO) and the Geological Survey of Victoria (GSV) conducted aerial geophysical surveys of the Bulart area during 1989 and 1999 to investigate the geology and explore for minerals. One component of these surveys measures the natural gamma radiation that is emitted by the decay of a radioactive isotope of potassium, which occurs in soil minerals.

To investigate the usefulness of airborne geophysical surveys for soil mapping , Dr Geoff Dickson , lecturer in Geophysics at the University, manipulated the data sets collected from both the 1989 airborne (potassium channel) and ground (Skene K) data . A reasonable correlation could be achieved (Figure 9), which may be improved with further research .

5.3 Soil salinity

The most complete survey of salinity at Bulart is presented in Fiona Jerinic's 1993 research , which is based on vegetation mapping . However, soil salinity, as measured by the Electrical Conductivity (EC) readings of the Bulart soils, was carried out as a part of the 1998 survey.


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Figure 9a. An image of the intensity of potassium as measured by an airborne radiometric survey over Bulart in 1989. The colour scale relates to the measured intensities (in counts per second) calibrated to the sites where soils were sampled .

Figure 9b. An image of the Skene K values as measured by the soil sample survey over Bulart in 1998. The data has been manipulated to attempt a correlation with the airborne measurement.

Both images created by Dr. Geoff Dickson, 1998.

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Figure 10. Bulart soils -Salinity (EC(1 :S) values)

1.8 dS/m

1.6 dS/m

1.4 dS/m

1.2 dS/m

1.0 dS/m


The results range from 0.04 to 2.16 deciSemiens per metre (dS m-1). The average EC value for samples was 0.22 dS m-1. When converted into ECe (Electrical Conductivity of the saturation extract) equivalent units, the value (assuming the topsoil to be a sandy loam) was 2.24 dS m-1. The crop response according to this ECe measurement would restrict yields of very sensitive crops. Using the Matters and Bozon (1989) classification of soil EC, and the US Department of Agriculture (USDA) soil ECe scheme (Table 3) , a low salinity hazard is projected from the average EC1:5 results.

Soil salinity varies with the seasons. Drying of the soil during summer and autumn concentrates salts in the soil , and they are dissolved again during the wetter months. As the first soil samples were collected during a dry autumn, EC values were at their highest (average 0.24 dS m-1). Whereas the September samples have lower EC values (average 0.16 dS m-1). Typically , topsoils in the BLMG reg ion are low in salts , except for discharge areas.

Salinity Hazard Soil EC1s J..LS cm·1 Soil ECe dS m-1

Matters & Bozon _{_1989) USDA (1954)

None 0-2

Low < 600 2-4

Moderate 600-1400 4-8

High 1400-3500+ 8-16

Ve~High -- > 16

Table 3. Classification schemes of soil salinity hazard .

There are several possible sources for the salt:

1. Cyclic salt. The salinity of rainfall in south eastern Australia has been measured in numerous studies, and is related to the distance from the ocean . Cyclic salt is being added through rainfall , although presumably in much lesser quantities than during the Miocene and Pliocene, when the area was coastal.

2. Depositional salt. Salts may be deposited with marine sediments (connate salt) , or be accumulated by wind blown salts from salt lakes, coastal flats , etc. In the recent geological past, there have been many opportunities for salts to be deposited. During the sea incursions of the Miocene and Pliocene, salts could have been deposited from the seawater or blown in from the nearby coastal area . In the recent arid period , during the last ice-age (about 18,000 years ago), salts may have been blown in from South Australia with dust storms.

3 . Mineral dissolution. The dissolution of minerals by groundwater and their alteration during weathering can add to the source of salts. The continued and intensive weathering of the ignimbrite and granite have been shown elsewhere to be correlated to salt accumulation.

4 . Anthropogenic. Salts can be added to a landscape through the application of fertilisers , stock manure and urine, irrigation waters , pollution , etc.

5. Salts left by the evaporation of saline groundwater. At Bulart, the salts accumulate over time by the evaporation of saline groundwater discharge.

The soil salt distribution shown in Figure 10 is not very representative of the saline areas, but shows the low-salt areas rather well. The "bulls-eye" contours are mostly based on one or two high readings from saline discharge zones along the creeks. The contour plot is more useful to show how many samples there were with a very low salt content.



5.4 Soil acidity

The pH of a soil solution is measured by the concentration of hydrogen ions [H+]. In pure water, the pH= 7, which is said to be neutral. Either side of this is either basic (pH = greater than 7) or acidic (pH = less than 7) . Higher concentration of H+ ions causes the solution to be acidic. A classification system developed for Victorian soils is shown below.

Soil acidity ratinQ Soil pH Vegetational effects

Slightly acid or > 6.0 No obvious signs of salinity; full and healthy cover alkaline of pasture, crop or native veQetation

Moderately acid 5.6-6.0 Some intolerance in specific crops, eg. annual medics, safflower, barley, canola or peas

Strongly or very acid 5.0-5.5 Evidence of crop or pasture intolerance, eg. subclover or wheat and demonstrating poor persistence of phalaris

Extremely acid < 5.0 Serious pasture intolerance or crop intolerance, eg . lupins, triticale, oats and ryecorn , with a reduction in vegetation cover including bare ground

Table 4. Soil acidity classification for Victorian soils (OCE, 1991 ).

The pH affects the nutrient availability for plant growth. The common effect of low pH is that elements required in significant quantities (phosphorus, potassium, sulphur, etc.) become unavailable to plants, and those associated with poor plant productivity (eg . aluminium, manganese, iron) , become available . Soils with a pH 6 or below are likely to experience some form of nutrient deficiency .

Soil pH is measured as in 1:5 soil:water solution , with and without the addition of Calcium Chloride (CaCb) . With water added to soil for pH measurements, the soil salt solution is diluted causing an increase in the pH (called the Salt Effect). To overcome the salt effect, 0.01 M CaCb is added to minimise the effects of dilution. Since there were variations between the 1996 pH values (Rexy Perry's) and the 1998 values (Nathan Robinson's), a repeat test of most of the samples was conducted , using new equipment and more reliable buffers. Additional independent testing was also carried out by the Rutherglen Research Laboratory. Such thorough testing provides more confidence in the pH values.

The soils of the Bulart region have moderately acidic surface horizons as shown in the contour maps produced for pH (Figures 11 & 12). Topsoils of the study area have pH (H20) values varying from 4.0 to 8.0. All soils are acidic apart from those in saline discharge zones occurring along the break of slope lining the Western margin of the Wan non River. In those locations, pH (H20) measurements are typically greater than 7.0 and alkaline, probably due in part, to the nearby limestone. The similarity of results from autumn and spring show that the pH remained almost identical between May and September sample periods.

The soils of the BLMG are described by the Victorian soil pH classification as being extremely acidic. The results would suggest that it is probably the greatest factor limiting plant growth and is a greater limitation to primary productivity than soil salinity.


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E 0 0 0 "f-('") co 0.0

E 0 0 0 C\1 ('") co 0.0

(

578000m 580000 m 582000m 584000 m

All data from Robinson, 1998. Contours become less reliable away from soil sample sites.

586000m 588000m 590000m

AMG Easting

Figure 11. Bulart soils -Acidity

(pH(H zO) values)

• Sample site

592000 m

E 0 0 0 0 I.C) Q) I.C)

E 0 0 0 Q) '<t" Q) I.C)

E r. <.:> 0 <0 '<t" n:> li)

E 0 0 0 '<t"

"'" Q) I.C)

E 0 0 0 C\1 '<t"

0> Q) I.C) .s:

:e E (")

> r.

~ 0

~ 8 <:( '<t"

Q) I.C)

E 0 0 0 Q) (Y) Q) I.C)

E 0 0 0 <0 (Y) Q) I.C)

E 0 0 0 '<t" (Y) Q) I.C)

E 0 0 0 C\1 (Y) Q) I.C)

(

578000 m 580000 m

All data from Robinson , 1998. Contours become less reliable away from soil sample sites.

582000 m 584000 m 586000 m 588000 m 590000 m

AMG Easting

Figure 12. Bulart soils- Acidity (pH (CaCI

2) values)

7.5

7.0

6.5

6.0

5.5

5.0

4.0

3.5

• Sample site

592000 m


5.5 Organic matter

The Loss on ignition (LOI) procedure was used to determine the amount of organic matter in soil samples. In this procedure , the soil was heated to 550°C to burn the majority of organic matter. The measure is only approximate, as some organics do not ignite until temperatures of up to 1 000°C. While LOI is a relatively simple surrogate for total organic matter, higher LOI may be due to the loss of the water bound to clay minerals, as well as the combustion of organic matter.

The organic matter (LOI) levels for Bulart soils vary from 0.59 to 18.76%, averaging 8.13% (Figure 13). From the sample periods, the September samples have a slightly higher value (9.76%) than May samples (7 .76%) for organic matter. This variation is most likely due to the different locations of the samples, since the proportions of dead grass or organisms change over short distances. Organic carbon, a fraction of organic matter, is reported for laboratory analyses of soil. Using the calculation suggested by AG-PLUS (Pivot) laboratories in Victoria , soils at Bulart average 4.73% organic carbon , placing them in the normal to high range .

High organic carbon can be quite common in Australian soils due to the presence of charcoal, especially in surface soils. Research by CSIRO is attempting to unravel this complicating factor so that more reliable estimates of organic carbon levels in our agricultural soils may be achieved.

Soil organic matter enhances the cation exchange capacity , clay aggregation , nutrient availability and water-holding capacity of soils. Organic matter has the positive effect of increasing permeability , soil aeration and soil structure, while low organic matter levels have been associated with loss of elements through leaching.

5.6 Comparisons to background levels.

Seven soil samples were collected from roadsides, parkland reserves and a former school playground to provide comparative values with 'unimproved' soil fertility . The mean values of these reference samples is compared to the mean values of the total sample set (May and September samples) in the following Table.

Attribute Total samples Reference samples

Olsen P 11 .1 mg/kg "' 2.2 mg/kg

Skene K 69 mg/kg ~ 76.8 mg/kg

pH (H20) 4.97 ~ 5.28

pH (CaCb) 4.36 ~ 4.71

EC1:s 0.22 dS m-1 - 0.22 dS m-1

LOI 8.13% n.a.

Table 5. Mean values for total samples versus reference samples.

The sharp contrast of Olsen P levels suggests that cultivation and pasture improvement, including the application of fertilisers, have increased available phosphorus levels for farmland of the study area. The lower levels of Skene K on the farmland compared to the reference sites is probably due to the improved pasture growth, combined with the export of K through harvesting of grain , hay and agricultural produce.


588000m

AMG Easting

Figure 13. Bulart soils- Organic matter (% Loss on Ignition)

• Sample site

m


5.7 Soil sampling and caution

Probably the most influential factor on the results of soil tests is the soil sampling method. The strategy chosen for collection of samples was based upon a point sampling principle . Composite samples were composed of cores collected from an area approximately 1Om in radius of the base point. The main reason for implementing this strategy was to choose soil sample sites that represented a particular landform and soil type.

Since the samples are collected from point localities, they are not representative of the overall fertility of soils from paddocks. The number of samples collected from paddocks would not qualify as the classification of paddock fertility. While point samples act as a guide to the soil fertil ity , there is always a higher risk of contamination due to stock movement, stock camps, fertiliser dumps, urine patches, etc.

The vast number of samples collected over a wide distribution of the study area is considered to reasonably represent the general fertility of the region . However, the data is still sparse, and errors, from sampling through to testing may include:

• using a small sample to represent a large area

• volatility and chemical alterations to samples between sampling and drying

• drying and sieving procedure and contamination

• adequate and accurate laboratory testing

The work has been conducted to the best standard possible , using due care and professional expertise. While it is hoped that these possible errors are negligible, there is always the possibility that one or more factors have influenced results .

5.8 Soil Map

The seven units on the original soil map were delineated on the basis of a detailed classification of soil profiles using soil pits, intact cores and some hand augering . The soil units were related to the landform relationships. Soil-landform observations in the field were used to verify boundaries visible on air photos and to extend the existing mapped units. This work was detailed in Rexy Perry's thesis and the report on 1995 - 1996 Landcare Research, distributed to members of the BLMG.

The BLMG soil map has been extended to cater for the expansion of the Land care group, and a new unit has been added -the Newer Volcanics Basaltic Soils. The extension of Rexy Perry's (1996) soil map by Nathan Robinson , used the same mapping process to extend previously identified soil landscape units, and add a new soil unit on the eastern boundary of the study area (Figure 14). This unit is based upon the change in geology and soil profile from surrounding units. The results of the recent soil tests supplement the detailed soil descriptions given in the previous report.

Bulart Land Management Group & University of Ballarat- Geology

Bulart Soils Series Robinson, 1998 (based on Perry, 1996)

• Newer Volcanic basalt soils 0 Kurrambee alluvial soils • Tara soils • Upper Wannon alluvium 0 Swamp soils - Lunettes D Eloora sandy clay loam • Mayfield soils 0 Swamp soils

Figure 14. Bulart Soil Series 1998 version


5.8. 1 Eloora Sandy Clay Loam

The Eloora Sandy Clay Loam is the most common soil , making up about 36% (51.7 km2) of the BLMG area. This unit had the most samples tested , and the results show the greatest variations for Olsen P and Skene K. The mean values of both the phosphorus and potassium levels are proportionally higher than the mean total values, but the standard deviations are too large to consider the results significant. However, based upon the value of these two attributes, this soil type has the highest fertility of the soil units.

Attribute Mean value St. Deviation No. of samples

Olsen P 12.9 mg/kg 8.0 135

Skene K 89 mg/kg 65 135

EC 0.18dSm-1 0.13 135

pH (H20) 4.81 0.36 135

pH (CaCb) 4.06 0.34 135

Loss On Ignition 9.39% 3.32 43

Table 6. Eloora Sandy Clay Loam - results of 1998 topsoil sampling program.

5.8.2 Kurrambee Alluvial Soils

The Kurrambee Alluvial Soils make up about 24% (34.9 km2) of the area and have lower than expected phosphorus and potassium levels and higher EC and pH (H20) levels. This may be explained by the association of this unit with drainage lines that are noted for waterlogging and salinity.


Olsen P 9.6 mg/kg 4.9 105


EC 0.37 dS m-1 0.50 104

pH (H20) 5.26 0.78 104

pH (CaCb) 4.36 0.78 104

Loss on Ignition 6.77% 3.63 32

Table 7. Kurrambee Alluvial Soil -results of 1998 topsoil sampling program.



5.8.3 Mayfield Soils

Mayfield Soils, which make up about 25% (35.2 km2) of the area , have a lower pH (CaCb) level (3.93) showing the more acidic topsoils of this unit. Also marginally lower are Skene K (61 mg/kg) and organic matter (6 .67 %).


Olsen P 11 .5 mg/kg 5.8 77


EC 0.16dSm-1 0.11 76

pH (H20) 4.74 0.58 76

pH (CaCb) 3.93 0.30 76


Table 8. Mayfield Soils attributes from the 1998 topsoil-sampling program.

5.8.4 Tara Soils

Tara Soils, which make up about 10% (14.8 km2) of the BLMG area , have lower levels of phosphorus (8 .36 mg/kg) and the higher organic matter levels (9 .63 %) than the regional average.




EC 0.18 dS m-1 0.26 47

pH (H20) 4.78 0.29 47

pH (CaCI2) 4.09 0.32 47


Table 9. Tara Soils attributes from the 1998 topsoil-sampling program.

While all attributes for soil units described above have sample numbers of greater than twenty, the remaining soil units (Swamp Soils, Newer Volcanics Basaltic Soils, Upper Wan non Alluvium and Swamp Soils (Lunette)) have a smaller statistical base , and comparisons are not as valid .



5.8.5 Swamp Soils

In the four samples tested , Swamp Soils (- 3% or 3.7 km2 of the area) display an irregular available potassium level value.

Attribute Mean St. Deviation No. of samples



EC 0.22 dS m-1 0.21 12

pH (HzO) 5.06 0.38 12

pH (CaCiz) 4.12 0.45 12


Table 10. Swamp Soils attributes from the 1998 topsoil-sampling program.

5.8.6 Newer Volcanics Basaltic Soils

The Newer Volcanics Basaltic Soils ( - 1% or 2 km2 of the area) indicated a slightly higher potassium level then the regional , but results were only based upon six topsoil samples. Higher K is normal for the volcanic soils in the region.




EC 0.15dSm-1 0.05 6

pH (HzO) 4.89 0.32 6

pH (CaCiz) 4.01 0.27 6

Loss on Ignition - - 1

Table 11. Newer Volcanics Basaltic Soils - 1998 topsoil-sampling program.



5.8. 7 Upper Wan non Alluvium

Only four were tested for the Upper Wannon Alluvium (- 0.5 km2 of the area). Further sampling is required to check if the very low Skene K (19.5 mg/kg) and pH (CaCb) value (3 . 71 ), and high Olsen P (16.23 mg/kg), and organic matter content (2.77 %) is consistent within the unit.


Olsen P 16.23 mg/kg 2.85 4

Skene K 19.50 mg/kg 5.45 4

EC 0.10dsm-1 0.03 3

pH (H20) 4.997 0.359 3

pH (CaCb) 3.713 0.349 3

Loss on Ignition - - 1

Table 12. Upper Wannon Alluvium attributes from the 1998 topsoil-sampling

program.

5.8.8 Swamp Soils (Lunette)

Only one sample of the Swamp Soils (Lunette) (- 0.2 km2 of the area) was tested during the program.

Attribute Value

Olsen P 16.03 mg/kg

Skene K 20 mg/kg

EC 0.12 dS m-1

pH (H20) 4.47

pH (CaCb) 3.7

Loss on Ignition -

Table 13. Single sample of Swamp Soils (Lunette) tested in the 1998 sampling

program.


Figure 15. A.erial perspective view of the BLMG area, looking nort1 . The image combines a digital terrain model , 3erial photos, roads, streams and the BLI>.~G boundary (created by Tony Davidson, 1999)

Bu/art Landcare Research 1997 - 1998

6.0 The Bulart GIS

The Geographic Information System (GIS) which has been set up for the BLMG should become the most useful result from the past six years of collaborative research . The GIS should serve a number of purposes:

1. Continue to be the repository of data collected by the collaborative research projects (since 1993), some government projects, and some individual farm projects.

2. Establish the baseline data for future monitoring to check on changes in the spread of salinity , acidification of soils, groundwater levels, soil fertility, etc.

3. Provide all the Bulart data to future research projects, which should prevent going back to repeat what had been done before (ie. stop data getting 'lost in the system') .

4. Clarify the future research direction , as gaps in the database become evident.

5. Provide the best possible knowledge-bank for making land-management decisions.

6. Improve individual Whole Farm Plans by adding new layers to the existing plans.

Currently there are approximately 60 significant data files for the GIS. Files have been divided into three classes (geographical, research and attribute data). It is hoped that members of the group actively use the GIS in the aim of achieving their Landcare goals of increasing land quality, environmental awareness and productivity.

The ultimate benefits of a GIS for a Landcare group will be determined by how the members make use of it. As the University has only just handed over the data to operate in the system, the potential of the system is unknown. This GIS provides an uncommon opportunity for landowners at Bulart to use new technology in farm management. As more data are added, the usefulness of the system should become obvious. Ultimately, it has the potential to become one of the most important tools in maintaining , monitoring and improving farm productivity.



7.0 Continuing the research

• The State Government geologists are currently researching the Bulart area. Although the work is primarily aimed at encouraging mineral exploration , it is useful in providing valuable information for soils and groundwater research . The Victorian Geological Survey has just completed another airborne geophysics survey, which may be of immense importance in refining the soil maps and extents of soil salinity.

• The collaboration between the University and the Cavendish Tele-Education Centre places the BLMG members in the best position to take advantage of advances in information technology. It is unusual for a Landcare group to be so advanced in GIS technology, and the Bulart landholders now have the advantage of knowing more about their farms and regional environment. As the system develops, it is possible that the GIS information could be made available to individual members through the Internet.

• Waterlogging is shaping up as the most severe limitation to agricultural productivity at Bulart. It is directly implicated in the spread of salinity, the acidification of soils, the loss of nutrients and the decline of soil structure. With the GIS to back up hydrological research, models can be derived to show why certain areas are more prone to waterlogging and suggest how best to minimise the damage.

• The groundwater bores should continue to be monitored. Long term trends may take decades to emerge. Similarly, the soil also needs to be regularly monitored. With the baseline values now established, trends in soil fertility , acidity, and salinity can be tracked .

• More work is being carried out on the regional groundwater (by the University) to answer questions (or at least, try to!) about movement trends, origins and age.

• Erica's research has shown the benefits of a multi-disciplinary approach to environmental research . By encouraging researchers from other disciplines to become involved , we may learn of the interrelation between what we have already researched and pastures, insects, trees, sheep, etc.



Selected Bibliography of Dundas Tableland projects

Landcare Research Projects 1993 to 1998- Bulart Land Management Group and University of Ballarat

Reports.

1. Fiona Jerinic & Peter Dahlhaus 1994. Bulart Salinity Study. University of Ballarat.

2. Peter Dahlhaus & Chris Woof 1995. Bulart Salinity Study II - Groundwater and Soils. University of Ballarat, April 1995.

3. Peter Dahlhaus, Richard MacEwan, Rexine Perry, Jonathon Fawcett, Mark Paine, Erica Nathan and Vince Morand 1997. Landcare research projects 1995 & 1996 University of Ballarat, February 1997.

4. Peter Dahlhaus, Tony Davidson, Richard MacEwan, Vince Morand, Erica Nathan, Nathan Robinson and Brendan Cassens 1999. Bulart Landcare Research 1997- 1998. University of Ballarat, May 1999.

Honours Theses.

1. Fiona Jerinic 1993. A Hydrogeological Study of Drvland Salinity in the Bulart Region. Western Victoria . B.App.Sci .(Hons) thesis. Ballarat University College

2. Christopher Woof 1994 Geological and Hydrogeological Mechanisms of Salinisation at Bulart. B.App.Sci.(Hons) thesis. University of Ballarat.

3. Mark Paine 1995 Regolith Development on the Southeastern Dundas Tableland . B.App.Sci.(Hons) thesis. University of Ballarat.

4. Rexine Perry 1996 A Soil Survey of the Bulart Region. South-Eastern Dundas Tablelands. B.App.Sci.(Hons) thesis. University of Ballarat.

5. Jonathon Fawcett 1996 A Hydrological Investigation of Soil Water Logging in the Bulart Region. Southeastern Dundas Tablelands. B.App.Sci.(Hons) thesis. University of Ballarat.

6. Nathan Robinson 1998 Soils of the Bulart Land Management Group, Eastern Dundas Tablelands. Western Victoria . B.App.Sci.(Hons) thesis. University of Ballarat.

Other Dundas Tableland projects- University of Ballarat

Published scientific papers.

• Dahlhaus P.G. , MacEwan R.J ., Nathan E.L. and Morand V.J . (submitted) Salinity on the southeastern Dundas Tableland. Aust. Jour. Earth Sciences. Vo1.47/1

• Nathan E.L. (accepted for publication) Dryland salinity on the Dundas Tableland : an historical appraisal. Australian Geographer

• Nathan E.L. (submitted) Giving salt some history and history some salt. Journal of Australian Historical Studies.

• Fawcett J. & Dahlhaus P.G. 1998. Regolith Hydrology of the Dundas Tablelands- an Investigation of Soil-Water Logging and Salinity. Abstracts 49, Geol. Soc. Au st. 14th Au st. Geol. Conv., Townsville 6- 10 July 1998. p.138



• Dahlhaus P.G. & MacEwan R.J . 1997. Dryland Salinity in South West Victoria Challenging The Myth . in (G .McNally, ed .) Collected Case Studies in Engineering Geology, Environmental Geology, Hydrogeology, Third Series , Geological Society of Australia Inc. pp. 165-181

• Dahlhaus P.G. & MacEwan R.J . 1996. Dryland Salinity in South West Victoria Questioning The Myth. Abstracts, Aust. & N.Z. Nat. Soils Conf , 1-4 July 1996, Uni. of Melbourne, Vol.2 , pp. 57-58.

• Dahlhaus P.G. & MacEwan R.J . 1996. Dryland Salinity in the Eastern Dundas Tablelands- A New Conceptual Model. Abstracts, Aust. & N.Z. Nat. Soils Conf , 1-4 July 1996, Uni. of Melbourne, Vol.3 , pp. 53-54.

• Dahlhaus P.G . & MacEwan R.J . 1996. A new conceptual model for salinity processes on the eastern Dundas Tablelands, Victoria - implications for the land manager. Abstracts 41 , Geol. Soc. Aust. 13th Aust. Geol. Conv., Canberra 19-23 Feb. 1996, pp.1 04

• MacEwan R.J . & Dahlhaus P.G. 1996. Raising the Profile with Western District Farmers- Soils Training for the Landholder. Abstracts, Aust. & N.Z. Nat. Soils Conf , 1-4 July 1996, Uni. of Melbourne, Vol.2 , pp. 157-158.

Unpublished reports and theses

• Dave Whitworth 1991 A Salinity Study of the Dundas River Catchment. Western Victoria . B.App.Sci. 3rd year project. Ballarat University College.

• Mark Major 1994 Landslides and Risk Assessment in the Casterton-MerinoColeraine Region . Western Victoria . B.App.Sci. 3rd year project. University of Ballarat.

• Paul Merriner 1994 Presence of Aeolian Stratification in the Black Ranges . B.App.Sci. 3rd year project. University of Ballarat.

• Erica Nathan 1995 An Historical Guide to the Dundas Tablelands with an Environmental Focus. University of Ballarat

• Kelli Fankhauser 1996 Structural Geology of the Yarramyljup Creek Region , Victoria. B.App.Sci. 3rd year project. University of Ballarat.

• Kerry Pappin 1997 The Structure and Petrology of the Black Range, Victoria. B.App.Sci. 3rd year project. University of Ballarat.

• Nathan Robinson 1997 Bulart Groundwater Hydrogeology. B.App.Sci . 3rd year project. University of Ballarat.

• Erica Nathan 1998 Dundas Landscapes and Drvland Salinity. M.App.Sci. thesis , University of Ballarat.


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