The Nicholls see a future benefit in having carefully selected parts of the property that are set up to hold, feed and water core farm-livestock during adverse weather periods of drought, which they experienced in 2018–2019. As a purpose built piece of infrastructure, SMAs make feeding, watering and monitoring stock health more efficient. By providing a fast way to get stock off pasture, they can support the preservation and faster recovery of pastures and landscapes across the farm. The Nicholls want to avoid long-term damage and the SMA will help to protect their pasture and better manage ground cover recovery. Anthony sees the value in acting early and having multiple options when going into dry periods. He intends to slowly reduce the pressure on his pastures by destocking where possible, getting weaners off early and gradually locking up stock. This will help to ensure a swift recovery after dry conditions pass.

Anthony finished building the SMA in December 2023. With advice from Riverina LLS staff, he positioned it close to a 25-year-old shelterbelt on the lower slopes of a steep hill to maximise shade for livestock and drainage and to minimise flood risk. Anthony designed the SMA himself and worked through many versions to get the measurements correct based on stock numbers and other considerations like water flow and feed access. The SMA has five pens (35 x 65 m) and can hold 400 ewes, providing roughly 4–5 m2 per ewe.

Images 3 & 4. The SMA at Tumulla was installed in Spring 2023 next to a mature shelterbelt, providing valuable shade and shelter for livestock. Source: Anthony Nicholls.

The build involved several weeks of work spread over a few months. Anthony built the fences himself and got some help to put in the water infrastructure.

He completed most of the SMA just before a field day on his property and was able to show it to some of the other farmers involved in the project (see Image 5).  

During a dry patch in Autumn 2024, the SMA was used for weaned calves and lambs, which were fed every other day. This has allowed the pastures at Tumulla to rest and recover and Anthony is noticing the difference in groundcover compared to previous years when his pastures would have been continuously grazed. Using the SMA, for the first time ever, Anthony has completely destocked the main production area of the farm to let all paddocks fully rest and recover ahead of next season. Anthony shared these updates on the WhatsApp thread noting,

‘G’day everyone. SMA into action. Weaner cattle that came in on Sunday after a week being yard weaned. Working well so far. Have been letting them come into the laneway for shade, they were chasing it this week.’ – Anthony Nicholls

Choosing a site at Tumulla

Soils for Life worked with the Anthony to identify a location on their farm where they could do their in-field soil assessments, and that was also suitable for any future monitoring of their soils, vegetation and biodiversity. Anthony chose to monitor at one site in the ‘Old Fescue’ paddock, located close to the recently built SMA (see Image 7). The paddock was historically cleared of vegetation and more recently sown to a pasture of chicory, lucerne, phalaris, prairie grass and subterranean clover. 

Image 7. The main soil monitoring site is adjacent to the new SMA. Source: Soils for Life.

In-field assessments

Anthony did two independent rounds of in-field assessments in August 2023 and April 2024. Each time, he 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 the 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. 

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. See Images 8 and 9 for Anthony’s groundcover assessment in August 2023.

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. See Images 10 and 11 for Anthony’s infiltration assessment in August 2023.

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. See Image 12 for Anthony’s aggregate stability assessment in August 2023.

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. Anthony used a soil pH kit provided as part of the project, which is readily available from hardware stores². See Image 13 for Anthony’s pH assessment in August 2023.

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

Images 8 & 9. Assessing groundcover at the ‘Old Fescue’ site on day of soil sampling in August 2023. Source: Soils for Life.

Images 10 & 11. Assessing water infiltration at the ‘Old Fescue’ site at Tumulla in August 2023 (left). Assessing water infiltration at the ‘Old Fescue’ site at Tumulla in August 2023 (right). Source: Anthony Nicholls.

Images 12 & 13. Assessing soil stability at the ‘Old Fescue’ site at Tumulla in August 2023 (left). Assessing soil pH at the ‘Old Fescue’ site at Tumulla in August 2023 (right). Source: Anthony Nicholls.

Sampling for lab tests

To supplement in-field monitoring, Anthony collected soil samples from one location at the ‘Old Fescue’ site for laboratory analysis. The samples were collected from four different depths in the soil (see Image 14) 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 Nicholls with a more in-depth account of the soil at their monitoring site so they can track changes in these soil properties over time. With additional investment, soil monitoring and sampling at multiple locations across Tumulla would provide the Nicholls with a broader understanding of their soils.

The soil at the monitoring site is moderately well-drained, with a texture ranging from a loam to a medium clay and a slightly alkaline pH trend. The cation exchange capacity (CEC) is moderate and the organic matter percent is also moderate. The most notable properties that may be limiting to productivity are the low calcium to magnesium ratio, the low levels of some of the micronutrients tested and the low quantity and activity of the soil organisms. 

Organic matter and fertility

Due to its location in the landscape, the monitoring site receives surface and groundwater (and therefore minerals and nutrients) from upslope. The natural fertility of the soil type due to the influence of the volcanic geologies in the region, as well as Anthony’s management of groundcover, also contribute to the moderate to high soil organic matter value of 4.9% in the 0–8 cm sample. 

Anthony has become more aware of the value of groundcover in relation to building both above and below-ground biomass and increasing soil organic matter. While the levels of soil organic matter are adequate at the ‘Old Fescue’ site, he has come to recognise the value in continuing to build soil organic matter at Tumulla. He would like to include more deep-rooting plant species and monitor whether this helps to build soil organic matter. Anthony’s current soil monitoring will give him an understanding of the baseline levels of organic matter in his soils, and this will allow him to track changes in soil organic matter in response to any management changes.

Soil cation exchange capacity is a measure of the soil’s capacity to exchange and retain basic 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. Anthony now knows that while the CEC at the monitoring site is considered moderate to high compared to other soil types in the region, increasing soil organic matter has the potential to substantially increase CEC, particularly in the top 50 cm of the soil. 

Anthony was interested to learn to what extent aluminium levels reduce and/or inhibit the capacity of plants to receive nutrients. Typically, aluminium levels in the range of 2-5 mg/kg (2-5 ppm) will be toxic to plants that are sensitive to aluminium toxicity, and above 5 mg/kg (5 ppm) will be limiting to plants that are tolerant of aluminum toxicity. In relation to nutrient uptake, phosphorus, calcium, magnesium and sulfur are all affected by high levels of aluminium.

At the monitoring site, the exchangeable aluminium in the 0 – 8 cm sample was 5 mg/kg (5 ppm), but substantially decreased deeper in the soil. The low levels of aluminium below 8 cm in the soil, and the fact that the soil is not acidic, suggest that while  aluminium is high in the 0-8 cm sample, it is unlikely to inhibit plant growth.

Soil microorganisms

Anthony was curious about the lab results for the 0–8 cm topsoil sample that was submitted for soil biological analyses. Like many Australian agricultural landscapes, the soil at the monitoring site was dominant in bacteria compared to fungi. The loss of fungi in farming soils has come about due to several factors, including the clearing of trees and shrubs, soil disturbance (tillage destroys fungal hyphae and mycelium) and the use of fungicides. 

The lack of fungi in the monitoring site soil suggests that the mycorrhizal (fungus to roots) relationships responsible for microbe-root-plant interactions, such as water and nutrient uptake and exchange, are limited, indicating that the nutrient cycling at the site is also limited. One option Anthony is interested in exploring to improve nutrient cycling is increasing numbers of beneficial nematodes. Like protozoa, nematodes survive in the soil water and feed mostly on bacteria and fungi. In healthy soils these worm-like creatures are one of the smallest, but most abundant, multicellular animals. Another strategy that Anthony could consider is to focus on improving the ratio of bacteria to fungi in his soil as this is a primary indicator of soil health.

Soil structure and stability

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 exudates)³ or clay.

Anthony was pleased to learn from the lab results for aggregate stability that the soil at the ‘Old Fescue’ site was moderately-stable to stable. This confirmed his interpretation of his in-field assessments, which also suggested the soil was stable (see Image 12). 

Soils with low stability, including sodic soils, are susceptible to soil structure decline. 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. Although soil structure was not assessed as part of the project, observations of the soil profile at the monitoring site suggest that the soil had moderate to good structure. This supports the infiltration rates of about 40 mm/hr that Anthony observed while undertaking his in-field assessments at the site. Not only will a well-structured soil tend to be more stable, it will also allow water to infiltrate the soil at a reasonable rate leading to water-use efficiency and increased drought resilience. 

Anthony’s attention to maintaining groundcover and building organic matter will also benefit soil water infiltration and retention. A diversity of plants with different growing habits and rooting depths will intercept and distribute rainfall across the soil surface, and when the plant roots die, will provide a food source for the soil organisms and leave cavities in the soil which become pathways for water to flow through the soil. 

³Root exudates are organic carbon compounds (e.g. simple sugars, organic acids and amino acids) secreted from living plant roots into the soil.

Reflecting on the insights of the recent soil monitoring, Anthony is looking to build on what he has learned from participating in the project and is considering a series of monitoring sites across the farm that would represent his different soil types.

Anthony is particularly interested in how soil type is influenced by the position in the landscape and underlying geology. A better understanding of these relationships will help him recognise soil-landscape patterns and monitor his soils more efficiently. This approach will also reveal whether the soil properties he chooses to monitor are features of the natural soil or a result of management practices, and how this information might inform his future management decisions.