Demo Day - Soil: linking biodiversity, resilience & production
Pioneer pasture species from natural seed banks in the soil flourish after management activities and high rainfall provides the opportunity for germination on Gilgunnia Station.
Recent rainfall and flourishing vegetation made Gilgunnia Station the perfect backdrop for our second Western Division Resilient Landscape Project field day on the property, a day which focused on the relationship between biodiversity, resilience and production.
The field day illustrated that through managing grazing pressure and plant succession, you can develop healthy soils by maximising groundcover and maintaining diverse vegetation, which in turn support greater biodiversity - key to resilience in your landscape and production.
Hosted by Soils for Life and Local Land Services Western (supported by our generous partners from the Rotary Clubs of Sydney and Sydney Cove), our own John Leggett and Russell Grant and Gemma Turnbull from LLS opened the day, outlining our joint project and introducing the day’s speakers.
ASHLEY McMURTRIE- PROPERTY OWNER
Ashley braved the gathered crowd of around 40 to share his experience of building a more drought resilient and productive enterprise on Gilgunnia Station.
- In developing the management approach for Gilgunnia, the McMurtries “cherry picked” ideas from the various approaches that they considered. They built a system that met the unique requirements of their land and set practical, achievable goals.
- They adopted a business-driven model, so that any business profits were re-invested into the property. This was strengthened by ensuring that natural ecological function contributed directly to productivity.
- Work to improve performance began on the property’s most productive areas and higher elevations. This enabled faster development of more diverse pasture plants and supported seed dispersal by enabling wind and water to transport seed further.
- Establishing a test paddock was a key part of developing innovative solutions. This provided a site to test ideas and see what works and what doesn’t.
- Pasture regeneration is reliant on native seeds already in the soil and broader landscape.
- The recent period of heavier rainfall has brought a one in 15 year opportunity to increase seed beds and, due to a broader diversity of plants in pastures, an environment that encourages succession.
- Ashley analysed the water flow across the property to help understand how water could be channelled using water spreading banks toward more valuable pastures and aid in dispersal of seed.
- Data and mapping tools that can help are available on the NRM spatial hub
- Ashley typically starts pasture renovation with removal of Invasive Native Shrub (INS), sometimes followed up with ploughing. Whilst this temporarily exposes the soil to erosion and may impact soil structure, it can aid in removal of clay pans, increase water infiltration and ultimately reduces competition from INS. In conjunction with water spreading banks, this approach enables a more rapid succession of pasture plants from emergent species like spear grass (Austrostipa spp.) through increasing biodiversity and ultimately to higher value fodder like wallaby grass (Austrodanthonia spp.).
- Ashley is aiming to achieve 100% ground cover. Maximising rest periods for pastures is a key management focus and vital for ensuring optimum productivity.
Total Grazing Pressure (TGP) Management
- Managing total grazing pressure is critical to the system on Gilgunnia. To keep goats and kangaroos out of the best paddocks, Ashley uses 1200mm high hingejoint and barbed wire fencing.
- Trap yards use one-way gates to capture feral goats at water points. This helps control feral goats as well as providing an additional source of income.
- Additional information on building trap yards is available on the MLA website.
- Grazing pressure is managed by monitoring the most common and palatable pasture plants at the time sheep are moved into the paddock. Depending on the time of the year and other seasonal factors, the plant being monitored changes so for one grazing period it might be Digitaria and another redleg grass (Bothriochloa macra) as each becomes more dominant at different times.
Property owner, Ashley McMurtrie (left) explains the
techniques he is applying to improve his landscape health.
On Gilgunnia Station, pasture renovation combined with effective grazing management that emphasises pasture rest periods has enabled some areas to be capable of supporting stocking rates nine times higher than previously achieved.
It was clear that even with the successes, the McMurtries believe that they have still not reached their maximum potential and are continuing to renovate pastures and develop ways to continue to build the productivity and resilience of their property. Read the Gilgunnia Station case study for more detail about the approach, challenges and successes of Ashley and Carolyn McMurtrie.
SUSAN ORGILL – SOIL SCIENTIST
Susan Orgill, a soil scientist from NSW DPI, led us through an overview of the critical role played by biological activity in the soil and how the maintenance of pasture cover is important in maintaining soil health and fertility.
- Soil fertility is linked to soil’s ability to hold on to the important nutrients needed by plants and is related to the proportion of clay and soil organic matter. If erosion is managed, the volume of clay is largely fixed. However, soil organic matter, which can hold nutrients in the soil, can be changed by management practices.
- “Perennial grasses provide a more stable environment for microbes to survive”.
- Maintaining maximum pasture cover reduces soil disturbance and also acts as an ongoing source of organic matter that is able to support the microbes over the longer term.
- Microbes work to convert the soil organic matter into humus which helps to bind soil particles together, improving soil structure and enabling more storage of nutrients in the soil (cation exchange capacity).
- The combined action of plants, microbes and movement of water into the soil builds a more stable soil structure and increases the infiltration and storage of water, aeration of the soil and the ability for the soil to hold onto and recycle nutrients.
Susan discussed a study that was looking at the effects of perennial cover on soil organic carbon. The study compared soils between TGP-fenced and unfenced sites on individual properties. On Gilgunnia, the TGP fenced areas showed a significant increase in soil carbon, suggesting that the management strategies adopted were contributing to this change, reinforcing evidence of the link between litter/perennial cover and soil organic carbon.
Susan noted that soil organic carbon is one indicator of soil health, but that it may not increase even in a system that is functioning well. For example, if the system is low in nitrogen, this may limit the soil’s ability to sequester carbon, requiring different tests and management techniques to ensure soil carbon can continue to increase.
Susan Orgill discusses soil cores.
Using soil cores taken earlier in the day from different paddocks across Gilgunnia , ranging from shallow, more skeletal soils to deeper and well-formed soil, Susan showed us a couple of ways to better understand your soils and monitor changes over time.
Susan performed an initial inspection of the soil cores, showing how roots penetrate to different depths across different soil types. Root depth is linked to both the plant type and soil characteristics. The deeper the roots travelled, in general, the better the soil structure.
Susan wetted up some of the soil and for those not afraid to get their hands dirty it was passed around so that people could ‘work’ the soil and get an understanding of the soil texture. Sandy soils will not hold much water and tend to fall apart. Soils with more silt or loam will feel more spongy and form a ball, whilst those with more clay will feel more like plasticine and be harder to work.
Emerson dispersion test
Different results are visible in the Emerson dispersion test.
Susan then gave a demonstration of how to understand how the soil copes with the effects of water using the ‘Emerson dispersion test’. The test can be done out in the field and can help identify how well your soil is able to manage the effects of water. A small clump of soil is gently placed into distilled or rain water and then watched to see what happens over the first 10 minutes and again at two hours.
Soils that have a weak structure will usually show ‘slaking’. This is where the soil clump visibly collapses. This means that in the field, the soil is less able to accommodate rapid entry of water because it doesn’t retain its structure and will have fewer spaces and opportunities for the soil to store the water.
Some soils will show a milky ring just around the soil or even end up with a milky solution with only sand remaining where the soil clump once was. These characteristics indicate that the soil is ‘dispersive’ and how severe it is. In the field, a dispersive soil is likely to result in crusting at the surface preventing the entry of water into the soil and often result in areas with substantial erosion. Dispersive soils are often very hard when they are dry and can prevent plants from growing. It may also be an indicator of sodicity and other problems that are worth getting some help to manage effectively.
Soil clumps that hold their shape over the duration without milkiness or separation of the particles have stronger structure and are able to cope better with higher rainfall intensity and other disturbance as well as having better water storage properties. They also provide a growing environment for plants that is easier for roots to move through and to access the nutrients and water they need.
- For a more detailed description of this field test, along with pictures of what to look for can be found, look at this resource from NSW DPI.
Carrying out pH testing at different soil depths.
Susan also conducted a soil pH test using a field pH test kit which is readily available from most hardware stores, agricultural equipment suppliers and on-line for around $20. Soil pH can affect the availability of nutrients for plants or even lead to toxicity and other factors that inhibit plant growth. This test showed that in one of the soil cores from Gilgunnia the pH in the top portion of the soil was slightly acidic whilst further in the profile the pH increased to be alkaline. This, she indicated, is common in the region and is related to calcrete deposits (a calcium rich layer) lower in the soil. This reinforced the need to test soil from varying depths for all of these tests as there can be significant differences at depth that affect the performance of the soil.
Susan highlighted that changes to soil structure tend to occur over longer periods of time. Management practices that seek to work from the top down by maintaining plant cover are the key to building soil structure. The incorporation of more perennial plants helps carbon accumulation in the soil because of the shedding and regeneration of roots following grazing.
ANNE KERLE - ECOLOGIST
Anne had also been working with Susan on investigating system health between TGP fenced and unfenced locations but rather than working below the soil, Anne was looking at the diversity of animals above the soil (invertebrates and vertebrates). Anne’s presentation clearly showed how rainfall and the type of vegetation affect the level of diversity seen in different habitat regions. Importantly, the level of diversity in each system provided a clear indicator of broader ecosystem health.
Factors that contributed to biodiversity above the soil included:
- The degree of ‘patchiness’ or variation across the landscape. The more that the landscape includes a healthy mosaic of different types of habitats the more opportunities there are for a wider range of animals to live. Some animals like magpies are considered to be ‘generalists’ where they are able to feed and live in a broader range of areas. Other animals are ‘specialists’ such as smaller insect eating birds like wrens who prefer shrubby habitats.
- With better conditions such as increased rainfall, animal populations increase and they tend to move out from optimal locations or refuges to sub-optimal spaces, returning when conditions deteriorate. This movement is affected when connectivity between habitat areas is lost.
The increasingly diverse pastures on Gilgunnia Station.
Anne discussed some historical perspectives of drought in arid and semi-arid Australia. This reinforced the need to recognise that, even with less severe droughts, the impact of drought and lost productivity is typically much worse in degraded environments. Environments that are healthy and functioning well are more resilient to drought and much more able to recover from drought.
Healthier systems have more biodiversity in general and a wider range in the species that occur. Above ground biodiversity, particularly birds, can be relatively easy to see. Diverse systems that are in balance are also more able to manage pests.
GREG CURRAN - PASTURE PRODUCTION SPECIALIST/VETERINARIAN
Greg spoke broadly about managing pasture and soil productivity in the region, including:
- How he felt that the environmental condition of the Western Division was in better condition now than the 1890s, which he attributed to a reduction in rabbits and much better management of the land. The opportunity to use this year’s higher rainfall to lock in better pastures with higher diversity.
- The competing needs of stock and other grazing animals (kangaroos and goats) and the need to manage predators including wild dogs.
- The need to manage increased temperatures due to the effects on water in the landscape, on pastures and stock. With ground temperatures often far higher than air temperatures, exposed soil surfaces in particular can climb quite high, drawing out even more moisture and reinforcing the need to sustain maximum ground cover.
- The importance of getting the right mix of plants for productive pastures, but considering many regional challenges, that any growth is better than none.
Greg’s presentation led to a wide-ranging discussion about the challenges faced in the region in managing total grazing pressure. It was reported that there is an estimated 15 million kangaroos in Western Division alone. It was considered that the broader policy space is dominated by a low willingness to consider active population regulation such as culling, reflecting a difference in perspective of urban and rural populations. Views were also expressed that with the growth in kangaroo numbers, the situation had reached a point where even culling, if it were politically palatable, would be insufficient to manage the environmental degradation from large kangaroo populations under current conditions. Concerns were also raised that the impact would be far greater once rainfall and biomass returned to more frequent lower annual volumes which would result in animal suffering and even greater environmental degradation.
IN THE PADDOCK
LLS Western put on a great spread for lunch and in the afternoon, the group headed out to take a closer look at the renovated pastures on Gilgunnia. First stop was Ashley’s test paddock. The first targeted for renovation, it is one of the most diverse pastures on the station and able to achieve stocking rates substantially higher than un-renovated areas.
The second stop was a pasture that had had INS removed in late 2015, but had not yet been ploughed. There was visibly less diversity in the pasture than the test paddock, with extensive prevalence of speargrass. Ashley reported that this is typically seen as a dominant species in the earlier days of pasture renovation, reflecting its role as an emergent or early succession plant. There were smaller quantities of other plants such as wallaby grass, which over time would increase in prominence.
Ashley was still monitoring the pasture to determine whether ploughing was required to control any re-emergence of INS and to break up any hard layers. He was also seeking more advice about the best timing for ploughing to prevent soil loss from erosion, reduce the adverse effects of soil disturbance on soil organic matter and soil microbes as well as best support pasture regeneration.
Ashley is a perfect example of someone who has an openness to continuing learning, testing and adjusting management techniques to obtain the best outcomes for his landscape and production, with the generosity to then share his knowledge. It was a valuable field day for all.
The active management on Gilgunnia Station is generating increasingly diverse pastures, delivering increasing resilience and production capacity.
To view more photos from the day, visit our Facebook gallery.
Article by Kirsty Yeates
Read the Gilgunnia Station case study - Building landscape resilience you can bank on.
Read more about the joint Soils for Life / Rotary Club of Sydney / Local Land Services Western, Western Division Resilient Landscapes Project aimed at helping farmers to learn how to manage their properties to minimise the impact of drought on production and landscape health.