Kangaroo Island Page 9

  At Stranraer the limestone bedrock provides a lot of natural calcium which results in good soil structure. The sulphate component of gypsum is utilised by plants which can be deficient. Calcium, as opposed to sodium, provides strength to the soil and also aids in animal health. Soils are managed through consistent soil tests every 3-4 years, to determine nutrient deficiencies.

  The soil test in 1927 shows the high calcium levels present in the soil at Stranraer due to the limestone bedrock.

  Dung beetles are also residents of Stranraer. Australia has about 350 species of native dung beetles and 23 species of dung beetles introduced from Hawaii, Africa and southern Europe. The introduced species are very useful in Australian agriculture especially in cattle dominated areas. They are able to bury large amounts of cattle dung. By having this process there are extensive advantages to the soil including soil structure, better water filtration and soil biology is increased e.g. worms and plants are able to access nutrients more efficiently.

  Most of the native dung beetle species eat marsupial dung such as kangaroo, wallaby and possum, which are plentiful at Stranraer however, these species are not efficient at digesting domestic farm animal manure.

  The Bubas bison species of dung beetle found at Stranraer is a winter-active dung beetle from southern Europe. This species can be found in Western Australia, South Australia, Victoria, New South Wales and Tasmania. It buries dung beneath the pad in long tunnels that may extend into the soil profile some 50-60cm. Adult females lay eggs within these tunnels. Once the young hatch they remain in the tunnels until they turn into adults and emerge from the soil in the autumn (March to May). Stranraer has no cattle today however, there is still a large number of Bubas bison on the property. The MacGillivray district has a large number of cattle that support this large population of Bubas bison and other introduced species.

  The process that the dung beetles perform is of vital importance to soil management. And the removal of the dung material to lower areas in the soil profile removes the risk of erosion through water and wind and the loss of this valuable soil building resource. Bubas bison dung beetles have a life cycle of 1-2 years and for every kg of dung processed and tunnelled into the soil, 1kg of sub soil is bought to the surface.

  Drenches used for the control of stomach worms in both sheep and cattle, which have a chemical base, need to be monitored as these can have a devastating impact on dung beetle populations.

  The naturally infertile soils of Kangaroo Island had responded to adequate dressings of phosphatic fertilisers and trace elements, but in time it was becoming apparent that the former was causing a soil acidity problem. This was documented in the council minutes in 1986. The suggested remedy at this point was the application of lime in some form. Since there was a large deposit of suitable wind-blown lime sand known locally as the Little Sahara near the south coast, pressure for its use as a soil corrective began. The council requested an environmental impact study to be completed to determine the merits of mining this resource. Locals were asked to write letters stating their views. Thirty two letters were received and presented to council on 11th February, 1987. Consent was given only for a certain area to be mined.

  The management of soil has changed over the years with the cropping program in particular. In the clydesdale and early tractor years most paddocks were ploughed to manage weeds and also prepare the soil for seeding. Today, with the use of seeding technology and no tillage farming in particular, soil disturbance is very minimal, thus weed control has become reliant on the use of chemicals. Stranraer today is livestock focused more than cropping, so soil management is strongly related to the stocking rate to reduce soil erosion and to ensure soil is protected by using perennial grasses such as fescue and phalaris, and legume based perennials such as lucerne.

  Soil acidity has a severe impact on the earth and its production capabilities. The soil alkalinity or acidity is measured on a scale like the pH scale. pH is a measure of the concentration of hydrogen ions in the soil. The higher the concentration of hydrogen ions, the more acidic the soil. This process is a result of chemical reactions in the soil, so if a soil is pH 7 then this soil is regarded as neutral. If a soil has a pH less than 7 then the soil is acidic, if greater than 7 then the soil is alkaline. This reading is of great significance to agricultural production. If we consider the plants that we use in Australian agriculture, most are suited to a neutral or alkaline soil. Wheat, which is one of the main cereal crops grown in Australia, is best grown in soil which is neutral or slightly alkaline.

  In the country that my family have farmed for some time the pH ranges from 6.5-9.0, this allows for a wide range of plants to be grown for both grain and livestock production. This soil pH as well as soil nutrient status is monitored through continuous soil testing which involves taking a 10-15cm soil core and sending it to a soil lab for analysis. Plant testing of crops and pastures also allows for the nutrients to be monitored that are available to the plant. Some soils with high pH have the ability to reduce the availability of nutrients to the plant, primarily to do with the calcium. This also occurs in low pH or acidic soils where aluminium becomes soluble and readily available to plants. Aluminium is toxic to a high percentage of plants and this highlights the importance of understanding soil pH.

  There are processes of farming activity that impact on soil pH. Nitrogen and phosphorous based fertilisers are acidic in nature and are used to assist crop and pasture production. Therefore, continuous cropping properties have the potential to increase soil acidity over time thus reducing yields and quality of grain grown. Grazing systems also have the ability to increase acidity with fertilisers and the constant pressure from grazing animals over time will increase soil acidity if not managed correctly. In grazing systems in southern Australia, legume plants are used as they are high in protein and energy, this allows for rapid animal growth. These plants fix nitrogen from the atmosphere. By this I mean that the plant has the ability to draw in nitrogen from the air and be able to convert it to usable nitrogen by the plant. With this process the excess nitrogen is released into the soil. This nitrogen also has the ability to increase soil acidity.

  Understanding crops and their management was as vital in the 1950s as it is today.

  Paddock names on Stranraer relate to some event, person or feature that the area represents. Nelson for example is a paddock named after a workman called Nelson who cleared the whole area with an axe.. The hummocks were named to describe the lunette system of ‘small hills’ that line the eastern edge of Rush Lagoon. The Redhill was named after the terra rossa soil that is present there. Quail paddock, reflects the low lying areas that are suited to quails nesting in the region. Wattle Grove continues as this was the name of the school that existed years ago.

  The Still paddock in years gone by used to operate a still for the manufacture of eucalyptus oil.

  All of these paddocks have different soil types and thus are farmed and managed differently. The areas along the hummocks reflect a heavier clay soil type that is suited to cropping and lucerne production due to the high pH of the soil. Areas around Rush Lagoon are suited to grazing as these areas become quite wet during the winter and Wattle Grove is a relatively sandy soil type, best suited to grazing and lucerne production.

  All areas have their allocated areas represented as hectares, which assists with stocking rate decisions and seed required if cropped. Crop yields and hay production can also be measured by knowing the hectares. By allocating the proper paddocks to their production potential and soil limitations the whole farm plan can be put together.

  The areas of the farm with sandy soil types need to be managed differently to a soil type with a clay base for erosion reasons.

  The property is divided into paddocks represented in the map above. This allows for easier stock and pasture management and segregation of breeds and ages of livestock.

  Since the mid 90s Stranraer has undergone an extensive program to revitalise and protect the natural resource base
of the property. Over 495 hectares of the property has been protected, this includes Rush & White Lagoons, Wattle Grove, Quail Paddock and Helyars.

  Conservation at Stranraer has involved over 20km’s of fencing, 23 hectares of re-vegetation and the planting of 250 hectares of perennial pasture to support the livestock system.

  Stranraer is a member of the Trees for Life program, which is a volunteer program of growing seedling trees that are native to particular regions around South Australia. Over this time period, since 1995, 1000 trees have been planted annually. The process involved uses a ripper through the soil and planting the trees in the prepared soil.

  The main species grown are sugar gum, cup or swamp gum, KI narrow leaf mallee, southern blue gum, pink gum and a variety of melaleucas.

  Narrow leaf or Kangaroo Island mallee (Eucalyptus cneorifolia) grows in the 400-650mm rainfall area which represents a majority of Kangaroo Island. This species is ideal for wind protection and shelter for livestock. The timber is used in the Stranraer fireplaces and in the early days was used for eucalyptus oil production. These trees can reach 12 metres in height and have thick walled leaves and a small white flower.

  I remember planting 500 trees below the workmen’s cottage in 1995, ripping the area into approximately 20 rows. In sitting down to lunch that day, dad informed me that the phone was disconnected or not working. With a little investigation I realised that I had severed the underground phone line 20 times.

  These plantings have been carried out to assist stock shelter through wind breaks and grown in areas that are unproductive for agriculture and for attracting birds around the homestead. Seeds are collected through the program and propagated by volunteers then moved to landholders as seedlings for planting.

  The grey and white areas on the previous aerial photograph show areas of scald and surface salinity. Scald being where vegetation does not grow due to poor soil structure and the presence of soluble salts in the upper areas of the soil profile.

  The Wattle Grove vegetation area located in the northern region of the property has numerous bottlebrush species, which in October and November have extensive flowering. Apiarists in the region place bee boxes in this area to produce honey from the working bees. Within this area of 22.3 ha is a small lagoon called Lee Lagoon. This is a lagoon of medium water quality and attracts various bird species and is home to a kangaroo population.

  Salt water, which weighs more than fresh water, sits below the fresh water layer in the aquifer where it then gravitates to the sea. Farming in some situations has resulted in the movement of this saline water and having it exposed at the surface, similar to what happened with Rush Lagoon.

  Salinity, which by definition is ‘salts in solution,’ affects over 2 million hectares in Australia. Of this, 800,000 hectares is unable to be used for agricultural production.

  Salt has been accumulating in the landscape for centuries. Salt arrives in the soil through rainfall. Salt water, due to its weight, filters through the soil profile and accumulates at depth. A freshwater layer sits above this salt layer preventing it from impacting on plant growth. Agricultural practices over time have disturbed this system resulting in the movement of this salt through the soil profile and exposure at the surface where no vegetation will grow. I have seen this personally at our property Stranraer. Soil affected by salinity is very difficult to return to a productive state. The area below on ‘Stranraer’ was impacted in 1956 by flooding. The management of this area has changed considerably over the years.

  The management of these saline areas in Australia has taken many forms including the use of crops, pastures and fodder plants with salt tolerance, tree plantations, earth works and fencing. The main cause of salinity, as seen on Stranraer over the years, has been the removal of plants. Plants utilise water in the A horizon of the soil; without these plants water moves through the soil profile at speed, causing the salt to move laterally in the soil. Salt water sits below the freshwater layer in the aquifer system. In the drilling of new bores, as was done in 2006, it is important to manage the depth of the bore drill to ensure that the quality water is not contaminated by the salt water that sits below it.

  Stranraer has seen this occur in a number of areas on the property and the remedy in most of the cases has been to destock the areas and allow salt tolerant grasses to grow. Grasses and other plants have the ability to reduce and minimize the impact of salinity, by utilising water from rainfall and preventing it from moving through the soil profile thereby displacing salt and moving it laterally.

  The grasses used in the regeneration of these areas are Puccinellia (Puccinellia ciliata), Tall Wheat Grass (Thinopyrum ponticum)and the planting of melaleuca trees. Puccinellia grows in alkaline soil (but not acidic) and saline soils. Puccinellia is a perennial grass that forms tussocks up to 40cm high and wide. The plants hay-off in the December and remain dormant over summer. The nutritive value of puccinellia varies over the season; early in the season the plant is 60-70% digestible. As the plants flower, digestibility reduces to 10%.

  Tall wheat grass is widely grown in summer-moist areas and on soils of low to moderate salinity. Soil salinity is measured through a soil analysis. Tall wheat grass is summer active with most growth occurring from late spring onwards. The quality of tall wheat grass declines in late summer, so it is important to graze the plant before the stems are fully mature. Heavy grazing encourages tillering and maintains the quality of feed. Often, both tall wheat grass and puccinellia can be planted together to provide stability to waterlogged and saline soils.

  Legumes also have the ability to regenerate areas of waterlogging however, most species have a low tolerance to salinity. Balansa clover is able to tolerate waterlogging, but is not highly tolerant of saline soils. Legumes provide highly digestible feed with high protein for livestock growth.

  The Australian salinity issue is already very significant and having a tremendous impact on agricultural production. The National Land and Water Resources Audit estimates that 5.7 million hectares have a high potential for the development of dryland salinity, and predicts this will rise to 17 million hectares by 2050.

  The White Lagoon Wetland System (750 ha) comprises Rush Lagoon to the north, White Lagoon to the south and the mud flat which lies in between. The system is 22km south of Kingscote and boundary nominations are defined by a 25 metre depression contour (hummocks) on the east and south sides.

  The water quality on Rush Lagoon is of a better quality than White Lagoon. White Lagoon has a saline level that is higher than sea water, which is around 36,000 ppm salt, while Rush Lagoon is 10,000 ppm.

  The topography for White Lagoon suggests that water movement over the whole MacGillivray district results in an accumulation of salt water in White Lagoon. It is from here that this heavy saline water moves through the lower part of the aquifer to the sea in a southerly direction. This is a natural process that has been occurring for many years.

  The White Lagoon Wetland System is a valuable wetland habitat especially for waterbirds. It is an important feeding, resting and breeding refuge for many species of waterbird, particularly in summer. A large variety of fauna and flora including 45 waterbirds use the wetland system. This is a significant number of waterbirds compared to numbers recorded on wetlands elsewhere. It has an abundance of invertebrate fauna, including salt lake louse (Haleniscus Scarlei) and the mollusc (Coxiella striata) which provides an important source of food for waterbirds. The system also provides a suitable habitat for waterbird species to breed, (20) of which two are threatened species. As waterbird breeding colonies are not well documented or protected in Australia, the presence of the Sacred Ibis (Threskiornis aethiopica) breeding colony at Rush Lagoon is significant. Kangaroo Island has recorded 267 bird species along with 890 species of native plants.

  Of the many species of waterbirds found in the White Lagoon Wetland System five are scheduled in the South Australian National Parks and Wildlife Act (1972) as amended in 1988. The Cape Barren Goose (Cereopsis nov
aehollandiae), Musk Duck (Biziura lobata), Latham’s Snipe (Gallinago hardwickii) and Hooded Plover (Charadrius cucullatus) are considered vulnerable, whilst the Australian Shoveler (Anas rhynchotis) is considered rare. The Hooded Plover and the Freckled Duck (Stictonetta naevosa) are also considered rare at an international level.

  The Bush Thick-Knee (Burhinus grallarius) (non waterbird) is endangered and also lives in the system and the only mistletoe on Kangaroo Island (Amyema melaleuca) occurs at this site.

  In addition, the lunette formation at White Lagoon is the largest and the best illustrative remnant on Kangaroo Island, of a recent geomorphic process involving the contraction and migration of ancestral lagoon systems.

  The White Lagoon System is located in a depression on a relatively flat, poorly drained plain, which lies east of the Timber Creek catchment and south-west of the Bugga Bugga Creek. Rush Lagoon is a shallow, seasonally intermittent fresh water lake. It receives inflow from an unnamed creek originating 3-4 km to the north. White Lagoon is a shallow, permanent, brackish-saline lake surrounded by large areas of mudflats. It receives inflow from an un-named creek originating up to 9 km to the north and from Rush Lagoon via the mud flats. The system also has a high local watertable associated with it.

  Both lagoons contain the aquatic plants Widgeon Grass (Ruppia Spiralis) and Mush Grass (Chara). Rush Lagoon supports Myriophyllum and Crassula and White Lagoon contains Dunaliella Salina – a single cell alga which gives salt lakes their pink colouration. White Lagoon has a marginal band of scrubland comprising Swamp Paperbark (Eucalyptus cneorifolia) and Acacia with an understory of Samolus Repens.