This multi-faceted project has run for three years (2022-2025) and demonstrates management of input costs and risk by zoning in different soil types, understanding input requirements in different zones, and fertilising accordingly. This is particularly relevant following dry or drought years, when nutrients may be left behind and less will need to be replaced, and also in years with good soil moisture and rainfall to maximise the opportunity for higher yields.

The project builds on farmer activities delivered over the last three seasons (2022-2024), continuing to work with grower groups and individuals to implement Variable Rate Technology (VRT), but in addition, will also develop and implement an online VRT decision support tool for soil nutrient management. The tool will be built in two phases: Easy VRT and Expert VRT.

Access the project fact sheet here.

Project description: 

Demonstrating soil zone mapping for variable rate nutrition management

Mallee Soils are highly variable, and this variability provides significant challenges in optimising fertiliser inputs across paddocks but where implementation of Variable Rate Technology could prove beneficial. This project aimed to build on work produced in 2022 across three farmer groups in the SA mallee region. This work set the first stage of the importance of soil type variability and impacts on residual nutrient banks which drive current return on investments of fertiliser input.

The current project set out to guide growers further down the VRT track by helping them create zones and demonstrate variability of crop responses to changing fertiliser management. Growers were asked to select a paddock of interest and create different soil and therefore management zones through publicly available satellite and NDVI data. Growers were then encouraged to implement fertiliser strip trials by adjusting fertiliser rates (50% down, 50% up compared to grower practice) across these zones. Assessments of crop behaviour to different fertiliser programs across zones will assist growers to start the journey of implementing VRT.

Results from two focus farms in addition to multiple other paddocks with zoned information outlined the power of 1) creating zones for informed soil sampling and analysis, 2) soil analysis for outlining residual nutrient levels, constraints and fertiliser recommendations and 3) adjusting fertiliser rates based off the processes 1 and 2 to maximise partial gross margins compared to flat fertiliser rates.

Easy VRT- decision support taking growers from entry level to expert

Farmers in the low-rainfall Mallee region can manage their input costs and risk by zoning their soil types, determining what inputs are required in different zones, and fertilising accordingly. This is beneficial following both challenging and good years: in dry or drought years, nutrients may be left behind, meaning a reduced need for replacement; in years with good soil moisture and rainfall, zoning can boost opportunities for higher yields.

This project builds on farmer activities delivered over 2022 and 2023, continuing to work with grower groups and individuals to implement VRT, and in addition, will develop and implement an online Variable Rate Technology (VRT) decision support tool for soil nutrient management. The tool will be built in two phases: Easy VRT and Expert VRT.

Easy VRT, considered entry level VRT, will cover 80% of the process through simple zoning techniques and online decision support tool largely working on rules of thumb and widely available data. Expert VRT will address the remaining 20%, incorporating advanced targeting and analysis for a more personalised plan using in-depth testing. Both will be delivered as online decision support tools in the form of decision trees.

Grower interest in zoning and variable rate technology (VRT) has seen the project grow from small plot trials in three Mallee regions in 2022. In 2023, six focus farms – two each in the Murray Plains, Pinnaroo and Lowbank areas – sowed paddock-scale fertiliser strips across different soil types. These demonstration sites show other growers how to manage their own investigation of nutrition requirements when setting up variable rate technology for soil zones and fertiliser recommendations. Several other growers have zoned their paddocks, with the MSF led project supporting basic strip trials and soil sampling to help

In 2024, on-farm VRT trial strips were implemented across various paddock zones as part of the project. There were 8 trial strips across the Murray Plains region, 5 at Lowbank, and 3 at Lameroo, with 15 separate farmers participants involved in trialling their own VRT trial strips.

Growers from farmer groups at Coomandook and Bowhill, were encouraged to participate in the project by testing the decision support tool over the past 12 months, as part of the introduction to the project. Once refined through this process, the tool will be available in 2025, and applicable to farmers across all regions. The existing groups, Murray Plains, Waikerie and Lameroo/ Pinnaroo will also be introduced to the new tool to enable them to continue their journey through the process of broader adoption of VRT. The on-ground activities will still take place with growers from Murray Plains, Waikerie and Lameroo/ Pinnaroo to ensure the project can support growers to overcome the challenges.

Key achievements and results: 

2023 Outcomes

Fertiliser inputs are one of the highest input costs farmers encounter and in a low rainfall environment, it is important to manage input costs to manage risk. The Mallee environment is also characterised by highly variable soil types, which vary in nutrient availability and productivity and, therefore also vary in nutrient inputs required. Farmers in the low rainfall Mallee region can manage their input costs and risk by zoning their soil types, working out what inputs are required in different zones and fertilising accordingly. This is particularly relevant following dry or drought years where nutrients may be left behind and less will need to be replaced and in years with good soil moisture and rainfall to maximise the opportunity for higher yield potential.

Despite this knowledge, uptake of variable rate fertiliser technology was low prior to starting this project and therefore, the continuation of this project is a significant step in building confidence that variable rate fertiliser (VRT) through paddock zoning increases profitability. After several years of this project building on the adoption of VRT it has demonstrated significant variability in crop responses to applied fertiliser across varied paddock zones.  Project outcomes have been extensively presented to the participants and grower groups which has increased the knowledge and understanding that each paddock has variable soil zones and that each zone should be fed to its potential.

Three low-rainfall Mallee regions were selected from the first year of this project and participants involved in the first year were keen to keep these areas as they represented different soil types and constraints: Murray Plains, Lowbank and Lameroo farmer groups. (Pinnaroo moved across to Lameroo)

Across three key locations—Murray Plains, Lowbank, and Lameroo—focus farms were established over varying paddocks for the second year of the Variable Rate Technology (VRT) project. The goal was to assist farmers in implementing their own trial strips. Each location had two focus farms, resulting in a total of six sites across the state. Farmers managed their trial strips by varying nitrogen (N) and phosphorus (P) inputs or adjusting in-season N top-up rates. These were established across the six sites, each representing specific management zones determined through Google Earth imagery or previous EM38 mapping. Site characterization was conducted via soil sampling and testing, which helped predict the N and P requirements. Additionally, crop rotation data spanning 2-3 years was used to ascertain the paddock’s suitability for trials. This data was crucial in determining the best approach for VRT implementation, as it provided valuable insights into soil and crop conditions that could have affected outcomes.

The six on-farm paddock demo sites enabled each location to demonstrate the potential of VRT application at the farmer paddock level. This setup allowed local and neighbouring farms to closely observe the implementation, monitor the growing season, and harvest benefits of using variable rates of fertilizer in their own regions. This fostered a sense of trust and credibility within the farming community, as they observed tangible results in their local areas. Consequently, interest and adoption of Variable Rate Technology (VRT) have significantly increased in the project’s target areas.

Farmers stand to benefit significantly from these trials, as they provide a practical foundation for making data-driven decisions on nutrient management. By implementing VRT, farmers can optimize the application of fertilizers, which leads to more efficient use of resources and cost savings. Additionally, the tailored approach to nutrient application ensures that crops receive the right amount of nutrients at the right time, promoting healthier plant growth and potentially increasing yields.

Moreover, these trials can greatly benefit agronomists and researchers by providing valuable on farm practical data. This data can be used to refine Variable Rate Fertiliser inputs and enhance future recommendations, furthering our commitment to sustainable and profitable farming practices in the regions. The insights gained can help in understanding the variability within and between paddocks, leading to more precise and effective farming practices.

In a summary of current project outcomes extensive soil sampling program on the back of generating zones through Google Earth and NDVI can significantly tighten soil characteristics that drive nutrient availability which should maximise the effort and cost associated with soil sampling and costs at the laboratory. The benefit of this zonal approach compared to traditional transect sampling has been outlined by differences in N supply > 100 kg N/ha resulting in an equivalent N application of > 200 kg Urea/ha. Phosphorus recommendations based on zonal approaches can range from > 20 kg P/ha down to replacement of 5-6 kg P/ha depending on the growing area. These recommendations will maximise grain yields across the paddock but not significantly change overall expenditure of P inputs, just refining applications to zones which need it.

Grower demonstration strip trials outlined profitable increases in cereal grain yields were obtained in certain paddock zones through increasing P rates through MAP and addition of small amounts of urea. These were accurately identified by narrowing zones down to soil type by NDVI signatures. Both data layers are free and easily accessible to growers.

In most cases by developing a VRT program we could demonstrate increases in PGM between $20-$50/ha by either increasing yields through increased P or N inputs in deficient areas or by cutting back starter inputs in zones where significant N x P banks are present.

Growers and advisors are encouraged to use zonal paddock approaches to identify different performing areas and investigate poor performing parts of the paddock before starting replacement fertiliser programs. As outlined in this project, reducing starter fertiliser inputs on poor performing zones without identification of the cause of poor production can reduce grain yields and PGM.

This project has expanded on recent work through the Mid-North and YP which has outlined that poor NDVI areas can be often associated with poor P reserves and can return a bounce in yield with increasing P inputs compared to the strategy of decreasing P inputs with overly simplified replacement P programs.

Zone allocation for informed soil sampling programs and analysis can provide significant benefits to refining fertiliser strategies and implementation of VRT programs. Zonal soil sampling and taking representative samples allows for more freedom in the budget that allows extensive analysis to depth and incrementation compared to grid samples which is based on 0-10 cm samples and down to a couple of soil tests at the laboratory. While not a focus of this project sampling to depth has identified potential constraints at depth which would explain poor crop performance, build-up of nutrients in particular Nitrogen and Sulphur which provides additional supporting evidence towards effective nutrient applications.

Both industry experts have been invaluable assets to this project, aiding our farmers in adopting VRT in their farming systems. Farms have significantly benefited from the expertise and technical support of these specialists, while continuous communication and support from MSF have effectively bridged the gap in the industry’s shortage of VRT specialists. As we move into the third year of this project, we aim to have a readily available contact list for farmers and industry professionals seeking assistance with VRT adoption.

2024 Outcomes

The continuation of the Variable Rate Technology (VRT) project throughout 2024 has significantly enhanced farmers’ knowledge and decision-making capabilities. By conducting trial strips across across various zones in paddocks, workshops, resources and collaborations throughout the SA Mallee, new and old participating farmers have gained valuable insights into their land management practices which has been enhanced by adoption or continuing with VRT on farm.

Efforts in 2024 have built on the foundation established with the three farmer groups from 2023—Murray Plains, Waikerie, and Lameroo. The continuation of the project has enabled these groups to deepen their understanding of their unique seasonal conditions and manage them more effectively. By focusing on diverse soil types, constraints, weather challenges, and fertiliser requirements, the project has provided farmers with the tools and knowledge needed to make informed decisions and adapt their practices to achieve the best possible outcomes, even in a challenging season. Despite the challenges posed by the season, including dry conditions, farmers from the three groups remained committed to maintaining their trial strips. This dedication underscores their determination to adapt and refine their approaches to VRT, even under less-than-ideal circumstances.

Importantly, farmers are beginning to recognise the potential long-term benefits of VRT. By persisting with these practices over multiple years, they are uncovering valuable, cumulative learnings about how zoning impacts soil types, constraints and fertiliser inputs. This ongoing work demonstrates their resilience and commitment to sustainable farming practices, paving the way for improved outcomes in the future.

The project participant’s, Agronomy Solutions (Sean Mason), Peter Treloar and Insight for Extension (Chris McDonough), are making significant strides in enhancing farmer confidence and decision-making. Farmers are increasingly comfortable working with the team to prepare paddock zones and implement VRT strategies on their farms. A major highlight of the project has been the soil analysis conducted by Sean Mason, which has provided trial strip participants with valuable insights into their soil nutrient profiles. These results allow farmers to better understand the nutrient status of their soils across different zones, helping them make more informed agronomic decisions. By identifying nutrient deficiencies or surpluses, farmers can tailor their fertiliser applications to meet the specific needs of their soils, improving efficiency and crop performance. Another key area of growth has been in defining specific zones within paddocks and strategically placing fertiliser trial strips. This process involves distinguishing between zones and applying different fertiliser rates to optimise inputs and outcomes. Farmers are gaining confidence in tailoring their approaches, leading to better management of soil variability and long-term sustainability. Despite the challenges posed by this season, several new farmers-initiated trial strips, expressing strong interest in continuing the trials next year. The project’s Easy VRT crop walks, held across three locations, brought together both new and returning participants. These events provided an opportunity for farmers to observe in-field results, share their insights, and discuss the season’s impact. Many farmers demonstrated a solid understanding of the relationships between fertiliser rates applied in the 2023 trial strips and their 2024 outcomes. These discussions sparked meaningful conversations about fertiliser strategies across varying zones and soil types, underscoring the tangible value of the trials.

Even in a challenging season, farmers are already planning for 2025. They are exploring how to align agronomic decisions with seasonal conditions, with some focusing on feeding crops to their potential across zones and adapting as the season progresses. The trial strips, combined with soil test results, have become a practical tool for decision-making, empowering farmers to see firsthand how fertiliser use, timing, and nutrient availability impact crop performance.

With the technical support of Peter Treloar and his work on tailored EM38 maps, the project has addressed challenges with unpredictable technology, providing farmers with a customised approach to managing soil variability. Combined with Sean Mason’s expertise in soil nutrient analysis and agronomic guidance, the collaboration has created a highly supportive and impactful team. These efforts, alongside the support of MSF, have built farmers’ confidence in VRT practices, equipping them with the tools and insights needed to make precise, effective decisions tailored to their paddocks, soil types, and conditions. The project’s impact continues to grow, with Sean, Pete, and Chris expanding its findings to new farmer participants in surrounding areas such as Coomandook, Cambrai, and Wunkar. This expansion has encouraged new participants to adopt trial strips and implement the Easy VRT concept, even as the tool itself is still being refined. Their engagement has been instrumental in further developing the decision support-tool, ensuring the project builds a strong foundation for the future.

The ongoing work—including soil testing, zone mapping of numerous paddocks, and technical guidance on the use of various VRT machinery—has supported the development of the Easy to Expert VRT platform. While still evolving, this platform has the potential to become a practical and valuable resource for farmers across South Australia (even farming environments close to Mallee characteristics like WA). By combining emerging insights with tailored soil analysis across various soil types, the project is equipping farmers with the tools and knowledge needed to navigate the complexities of VRT, ensuring the supportive tools will benefit for many years to come.

Further information:

Further information and resources are available on the Mallee Sustainable Farming website.