Bert and Liz have been steadily putting up the tree guards sincelate 2023. Overall, it has been ‘a very opportune time’ to be doing this work because abundant rainfall throughout the season has  encouraged the germination of many self-seeded trees.

‘We shouldn’t waste the opportunity … if we hadn’t gone around and started to guard these trees then the stock would have taken them. In the next dry time we wouldn’t even know they were ever there.’ – Bert Matthews

The Matthews often identify new seedlings when they are busy with other things on the property, like mustering. Responding to what they see emerging naturally in the landscape is an exciting process because most of the trees at Bedarbidgal are aged trees. As Bert recalls, ‘we have had very little germination of young trees in my lifetime on the land.’ Bert believes the emergence of young seedlings ‘has got quite a bit to do with the fact that we don’t have stock in the paddock all the time. We don’t set stock any longer.’ Through the installation of tree guards, the Matthews are actively restoring and revegetating the landscape in new ways, giving these young trees a head start and the opportunity to ‘get up before being eaten off by stock.’

The Matthews still have some way to go with the installation. By April 2024 they had completed 20% of the approximately 150 tree guards, for mostly black box (Eucalyptus largiflorens) and boree (A. pendula) seedlings (see tree guards in Images 5, 6 and 7). The couple are using best-practice guidelines from Riverina LLS in order to protect their young paddock trees, with the following specifications for size and materials:

The funding they received for the project has gone a good way toward covering materials and reducing the total project cost. Riverina LLS provided useful advice on where to source new materials to supplement the ‘old steel pegs from old fence lines’ they are recycling onsite, and the Matthews now have all materials and plan to finish the project at a steady pace. Making the guards is quite a lengthy process because, as Bert describes, the ‘mesh is quite heavy, and you have to bend it and secure it, and then put in the iron pegs. As the ground has gotten harder, that’s become more and more difficult.’ 

An unexpected issue they have faced during the installation has been the appearance of bag moths, which have been stripping the boree trees of leaves, ‘you look over thousands of acres and all the trees have been stripped. These moths obviously have a larvae form and the caterpillars go and chew all the leaves off.’ Bert notes that this has been a bit ‘disheartening’ while they undertake work to propagate new trees, but he also sees that ‘it’s part of nature’ and ‘that the strong survive.’

Choosing a site at Bedarbidgal

The Matthews’ main monitoring site was in ‘Kyeema’ paddock where they have been collecting soil data for 20 years. The Soil Conservation Service (SCS) regularly visited the property as part of an assessment program, and ‘would come in autumn of every year, take a photopoint monitor, do 100 m transects and identify what was in a metre square in terms of species.’ Bert originally chose the monitoring site because it was adjacent to ‘a severe rabbit infestation’, and at one point cryptogam plants (e.g. spore plants, such as mosses, ferns and lichen) were the only groundcover and water would shed off the surface. Bert was curious about whether the presence of cryptogams was ‘a sign of first life or last life.’ Bert was also interested to see ‘what would happen if we put vegetation on there.’ The Matthews have been taking steps to improve soil health in that general area of the farm for a number of years. They have incorporated swales to hold the water, which has made a big difference, with the area now covered in vegetation. With the SCS data on hand, Bert has been able to go back and see periods of ‘boom and bust’ with groundcover, which he attributes to previous set stocking practices. 

Making monitoring simple

Establishing new monitoring routines meant overcoming a few challenges. ‘Putting aside the time to do it’ was one of the major hurdles ‘because we’re all very busy.’ Bert and Liz got better at this with time, recognising the benefits of the process and finding ways to make it work within existing practices. For example, the simple step of keeping the monitoring equipment easily accessible made it efficient to get out into the paddock for monitoring.

‘I’ve now got a box where we’ve got the ring and the infiltration gear … I have a single spot and I know where everything is and I just pick up the tub and it is all together ready to go.’ – Bert Matthews

In-field assessments

The Matthews did their field assessments in August 2023, November 2023, February 2024 and May 2024. Each time, they applied the following monitoring techniques: photopoints, groundcover, soil infiltration, aggregate stability, soil organisms and soil pH assessment using guides provided by Soils for Life.

The in-field assessments are described below and have been developed into a ‘Soil Health Challenge’, see the Soil Health Assessment Guide at the bottom of this page (with the exception of the pH assessment). Insights from the monitoring are summarised in the next section. 

Photopoints: This assessment involves setting up permanent locations where photos are taken repeatedly to capture changes over time. 

Taking photopoints was the first activity Bert did each time he visited the ‘Kyeema’ site before putting a shovel into the soil. He considers photopoints very advantageous because ‘as much as we think we know how it looked three months ago, it changes so slowly and you just adapt to the change because you see it every day.’ 

Groundcover: A simple way to measure groundcover is by visually estimating the percent of the soil surface within a confined area that is covered and not bare. 

Groundcover assessments are a central part of monitoring at Bedarbidgal. Bert regularly uses a hula hoop to estimate the percentage of cover, taking photos as a visual record each time. He pays close attention to what is growing month-to-month and how different species are responding to rain events.

Image 8. Assessing groundcover at Bedarbidgal in February 2024. Source: The Matthews.

Soil infiltration: Soil infiltration is the downward entry of water into the soil. The rate at which water can infiltrate can be estimated in the field by recording the time it takes for a volume of water to enter and move through the soil. 

Bert is interested in the water holding capacity of his soils, and while this is different to infiltration capacity, the two are related. By maximising soil water infiltration, any rain that falls can be held in the soil and not lost to surface run-off or evaporation. For Bert, regularly assessing soil water infiltration at different times throughout the year was a big ‘eye opener’. Watching how slowly or quickly water infiltrated his soils helped him understand how wet his soils could get under different management. He believes that assessing ‘infiltration rates at different times of the year is key, and observing how hard our soils get when they dry’.

Aggregate stability: Soil structure regulates the movement and storage of air, water and organisms, and therefore nutrients, in the soil. Soils with stable aggregates are more likely to retain their structure and are better able to withstand the forces imposed by wetting and drying, raindrop impact, stock trampling, cultivation and other disturbance.

Soil organisms: Soil organisms are responsible for many soil processes, including contributing to the development of soil structure, the breakdown of organic matter and the cycling of nutrients. One of the simplest methods for assessing the soil organisms that are visible with the naked eye (e.g. worms, beetles, spiders, ants, etc.), is to record the number that can be seen in a sample of soil within a defined period of time.

For Bert, just ‘being out digging your soil’ and observing the diversity of the living soil is valuable, and he notes ‘how exciting it actually is when we identify the critters in the soil over a period of time.’ 

Soil pH assessment: Soil pH is the acidity or alkalinity of the soil. Soils may be naturally acidic or alkaline, depending on the parent material on which they formed. Agricultural practices also influence soil pH, often removing alkalinity from the farming system, which results in an increase in soil acidity over time. A number of methods for estimating soil pH in the field are available. The Matthews used the soil pH kit provided as part of the project, which is readily available from hardware stores².

 ²The kit is called a Manutec Soil pH Test Kit and comes with easy to follow instructions. The kit is based on Raupach and Tucker’s field method for assessing soil pH. See Raupach, M and Tucker, B (1959) The field determination of soil reaction. Journal of the Australian Institute of Agriculture Science 25:129−133. To see a soil pH demonstration, visit: https://www.youtube.com/watch?v=HZz3-cv_GGc&t=123s.

Sampling for lab tests

To supplement the in-field assessments, the Matthews collected soil samples from one location at ‘Kyeema’ for laboratory analysis. The samples were collected from four different depths in the soil (see Image 12) and submitted to the laboratory for a range of soil physical, chemical, and biological tests. The purpose of sampling at a single location was to provide the Matthews with a more in-depth account of the soil at their monitoring site so they can track changes in these soil over time. With additional investment, soil monitoring and sampling at multiple locations across Bedarbidgal  would provide the Matthews with a broader understanding of their soils.

The soil at the ‘Kyeema’ site is moderately well-drained, with a gradual increase in texture from a sandy clay loam to a medium clay and a neutral to alkaline pH trend. The most notable properties are the low cation exchange capacity (CEC, one indicator of the potential fertility of a soil) in the topsoils where many of the plant roots will be seeking nutrients, the low calcium to magnesium and carbon to nitrogen ratios, and the increase in exchangeable sodium from about 50 cm depth in the soil.

Groundcover, organic matter and fertility

Maintaining groundcover has been central to the Matthews’ stock management and grazing regimes since 2018. They understand the value of groundcover in relation to building above and below-ground biomass and increasing soil organic matter, and will remove stock if that is what is required to maintain groundcover. 

In February 2024, Bert observed ‘virtually 100% groundcover with some bare ground through the canopy but mostly litter covering the surface.’ Paying attention to how groundcover responds to weather events, Bert noted that they received 160 mm of rain between December 2023 and January 2024, which led to a ‘huge flush of summer grasses and forbs,’ including curly windmill grass (Enteropogon acicularis), saltbush (Atriplex spp.), sida (Sida sp.), turnip copperburr (Sclerolaena napiformis), and woolly button (Leiocarpa panaetioides). They had a good germination of medics in the January rain, but they ‘burnt off’ in the February heat, with temperatures reaching 41°C.

Groundcover is necessary for building above and below-ground biomass and increasing soil organic matter. And organic matter plays an important role in the development and maintenance of soil structure, increasing the soil’s water holding capacity and storing nutrients in organic forms. The lab test results suggest that the soil organic matter at the ‘Kyeema’ site is low to moderate for the soil type and region, and these results are comparable to previous soil testing of a similar soil at Bedarbidgal³. The Matthews’ commitment to maintaining groundcover will help to build organic matter in their soils.

Soil CEC is a measure of the soil’s capacity to exchange and retain cations (and therefore nutrient availability for plants). It is also an indicator of soil fertility and is influenced by the soil clay content, organic matter levels and soil pH, with organic matter having the potential to substantially increase soil CEC. The ‘Kyeema’ site subsoil showed a four-fold increase in CEC at 30+ cm depth, reflecting the increase in soil texture from the clay loam topsoil to the medium clay subsoil. After discussing these relationships with the Soils for Life soil scientist, Bert reaffirmed that building organic matter will be an effective way to increase the CEC of the soils at Bedarbidgal.

In addition to the CEC, a number of cation ratios offer insights into the processes happening in the soil. One such ratio is calcium to magnesium, which influences the exchange of oxygen in soils, effectively allowing soil to breathe. Clay soils with a low calcium to magnesium ratio, such as the soil at the ‘Kyeema’ site, can become ‘tight’ and low in oxygen, which is essential to the survival of the soil organisms and the plants. In these soils, and in soils high in sodium, increasing calcium can improve the soil structure. 

³It is important to note that for all soil tests, results may vary depending on the method of test used and the laboratory at which the tests were conducted.

Soil organisms

By monitoring the soil organisms, Bert could see how they respond to the conditions, sharing that ‘when it’s dried off you can understand that they’ve either gone deeper or they’re dormant somewhere in their life cycle.’ In February 2024 Bert observed that cicada nymphs were the only critters in his sample (see Image 13). He also observed a lot of cavities in the top 10 cm (see Image 14) of the soil, which is evidence of soil organism activity. 

In relation to soil microorganisms, the lab results identified that bacteria is more dominant than fungi in the monitoring site topsoil, and this is common in many Australian agricultural soils. Bacteria abundance and activity were within the expected range, indicating that they are performing their role of decomposing organic matter and mineralising nutrients. Similarly, the protozoa which feed on bacteria are actively cycling the nutrients and making them available to plants. However, the lack of fungi means that the mycorrhizal (fungus to roots) relationships responsible for microbe-root-plant interactions, such as water and nutrient uptake and exchange, are limited.

Soil structure and infiltration

Soil structure is the natural arrangement of soil particles into aggregates or ‘peds’ (the structural building blocks of the soil), separated by voids. It governs soil permeability, infiltration, aeration, drainage and stability. While also providing organisms with a safe habitat, soil structure can be created and improved by the activities of soil organisms. The results are a more stable soil where the soil aggregates are held together either by organic matter (including soil organism secretions and root exudates⁴) or clay. 

At the ‘Kyeema’ site, the soil organic matter levels are low, but the sandy clay loam texture suggests that there is enough clay present to contribute to soil aggregation. However, the low aggregate stability reported by the lab results is a reasonable indication that another factor is contributing to the lack of stability in this soil, which in this case could be a result of excess sodium (see below).

Soil sodicity and stability

One of the many benefits of soil testing is that the results can reveal what the in-field observations cannot. At the ‘Kyeema’ site, the soil tests revealed that the low aggregate stability is magnified by the presence of sodium, which is often a result of the natural weathering of the parent materials from which the soil has formed. 

Soils with excess sodium (sodic soils) are highly susceptible to soil instability and soil structure decline, particularly if exposed to any form of disturbance. This loss of soil structure limits key soil processes such as soil water infiltration and aeration, resulting in a less than ideal habitat for soil organisms and plant roots. Minimal disturbance of these soils and a focus on maintaining groundcover can help increase soil stability and reduce the loss of soil structure.

⁴Root exudates are organic carbon compounds (e.g. simple sugars, organic acids and amino acids) secreted from living plant roots into the soil.

Bert wishes he had known about the simple in-field methods for monitoring soil earlier in his farming career. The Matthews appreciate the simplicity of these methods and they are clear about how they will integrate them into their monitoring in the future. The project emphasised to farmers the importance of taking a long-term view on soil monitoring and the Matthews are in it for the long game. Their intention is to have a quarterly monitoring routine, which will be marked in the calendar to remind them to undertake the process at the beginning of each new season at Bedarbidgal.