The Black Range Project
This page will be progressively developed and updated in the near future as time permits and as more results become available.
The project commenced last year when RENEW realised an opportunity to work in a partnership with the Mullins/Wiseman families on their Dunluce property below the Black Range west of Maryborough. The family had contacted the Northern United Forestry Group seeking advice and support in their ongoing efforts to improve the health of their land.
The granitic terrain immediately below the Black Range has a long history of soil erosion and dryland salinity, With a strongly supportive community it is proving ideal as one of our first RENEW ventures.
The Mullins and Wiseman families participate in the Timor West Landcare group and this community group has warmly welcomed RENEW.
Ken and Helen Calder have leased the farm from the Mullins/Wiseman families since 2007. They also have land at Murphy's Creek and overall they farm 3,000 acres. They run up to 5,000 sheep and crop around 750 acres. Both the Murphy's Creek and Dunluce properties comprise land that is difficult to farm and much care is needed when striving to preserve and increase productivity. Ken and Helen won the Victorian Landcare Award for Sustainable Farming in 2007.
Earlier this year (2014) RENEW formally commenced investigations of the Dunluce property. We called in Ian Rankin (previously Chair of the NUFG) and his excavator. We dug five soil pits in a transect extending from the foot of the range through to the mid slopes of the property. We described the soil profile in great detail and collected soils samples for chemical analyses.
SWEP Soil Laboratories in Melbourne completed the chemical assessment of the soil free of charge and we are extremely grateful for their support in this community-based program. The results are presented below:
Site 1: 0 - 0.1 m 0.1 - 0.2 m 0.25 - 0.5 m
Site 2: 0 - 0.1 m 0.1 - 0.2 m 0.3 - 0.5 m 0.7 - 1.2
Site 3: 0 - 0.1 m 0.1 - 0.2 m 0.3 - 0 0.5 m 1.0 m
Site 4: 0 - 0.1 m 0.1 - 0.2 m 0.5 - 0.6 m 1.1 - 1.2 m
Site 5: 0 - 0.1 m 0.1- 0.2 m 0.5 - 0.6 m 1 - 1.2 m
The story thus far.....
Excavation of the soil pits in this granitic terrain at Dunluce revealed a number of interesting things. The most obvious and fascinating physical characteristic proved to be a thick cemented bleached pallid surface horizon some 50cm thick. Examination of this under the microscope reveals it is comprised almost entirely of very fine grained angular quartz fragments. In summer this layer packs down so hard it has the consistency of concrete, and it winter it becomes wet and waterlogged and the unconsolidated mass is almost impossible to drive over without getting bogged. This condition is common within the granitic terrains of northern Victoria.
Agriculture is difficult in land with this character since sowing must coincide with optimum soil water conditions. Plants experience great difficulty surviving in an environment that is waterlogged in the winter and hard and almost impenetrable over the dry summer.
Beneath the bleached siliceous surface horizon we found a well developed red-grown silty clay up to half a metre thick. obviously formed through eluviation of the horizon above. At depth this gave way to a mix of clay and intensely weathered granite. Both the clay B horizon and the underlying clay/weathered rock contained residual soil water despite the near surface cemented layer being very hard and dry. It was very evident plant growth and use of deeper water were inhibited by the hard setting surface layer.
To our great surprise the subsurface clays and weathered rock were strongly alkaline. pH values (water) exceeded 8.5 to 9.0. This suggests equilibration with free calcite (limestone). Carbonate nodules were not observed during pit excavation, but we can be almost certain they exist as finely divided particles within the clay/decayed rock matrix. This alkaline condition affords greater opportunity than might otherwise be available in deeply decayed low pH granitic terrain.
The alkaline subsoils are most likely the result of wind blown carbonates delivered during the last glacial maximum some 22,000 years ago. Sea level along the southern coast of Australia is known to have fallen by at least 120 metres during these times as ocean water was turned to ice. Exposed limestone along the South Australian coast was deflated by wind erosion which ultimately delivered large amounts of carbonate rich loess to south-eastern states.
In strong contrast in the near surface cemented layer has a pH that in places is acidic. Some sites have pH (water) below 5.5 indicating the potential for phytotoxic aluminium.
Most samples, irrespective of texture and depth, have a low cation exchange capacity. This is consistent with soils and subsoils that comprise kaolinite clays formed from the weathering of granite together with generally low amounts of soil organic matter. The fertility of the soil is mitigated by these conditions since the potential reservoir of cations required for optimum plant growth is much reduced.
Soil organic carbon levels were found to be very low. The highest value in the uppermost 10 centimetres was about 2 percent, but in most instances the average was 1 percent. Below the immediate topsoil organic carbon fell very rapidly to values to about 0.25 percent or less. Organic carbon was almost absent at greater depth.
Although localised salinity problems are common throughout the Dunluce farm the soils we sampled did not exhibit salinity issues. Electrical conductance of 1:5 soil water extracts seldom exceeded 500 uS/cm.
The difficulty we have in these soils is a general lack of structure caused by poor soil development in the near surface horizon. This uppermost cemented bleached layer is a hostile environment for plant growth, and without adequate plant growth there are limited opportunities to boost soil carbon needed to improve hydrological function and fertility.
The quest is to identify a farming systems that will facilitate increase soil carbon sufficiently to improve soil conditions for plant growth. If we can solve this riddle we have considerable opportunity to improve water entry and optimise plant growth and productivity.
The soil structure issues present at Dunluce are not unique to the region. Around 75 percent of the soils of North Central Victoria are sodic and prone to soil structure problems. The issues vary in process and manifestation in accordance with geological, geomorphic conditions and faming practices.
Are you able to help us?
If you have experience in re-building soils that suffer from these issues we would like to hear from you. Please write to us at nufg(at)nufg.org.au. Note: Please replace the work 'at' with the usual @ symbol.
Maps depicting the location of the sites and soil profile descriptions will be posted shortly