Exploring Novel Soil Amendments in the Future Carbon Project
By Kate Parker & Simon Kruger
Introduction
In the West Midlands region farmers face significant soil challenges, including water repellence, nutrient leaching, and low nutrient levels. These challenges are largely due to soils with low clay content and organic carbon, which contribute to poor nutrient and moisture retention, impacting both soil structure and fertility. To address these issues, local farmers are adopting next-generation soil amelioration tools and organic amendments to enhance soil fertility, increase soil carbon levels, and improve overall resilience—particularly in sandy soils.
The Future Carbon Project, funded by the Department of Primary Industries and Regional Development (DPIRD) and the Soil CRC, has been a pivotal project running for over four years. This long-term study and Wathingarra Road trial site evaluates the effectiveness of various organic amendments in improving soil organic matter and explores combinations of amendments and amelioration techniques to identify potential synergies. The goal is to achieve long-term benefits for soil health, carbon levels, and crop yields.
In August, a group of 20 local farmers and agricultural industry representatives visited the Future Carbon Project trial site at Jeremy Roberts’ property in Badgingarra as part of a West Midlands Group (WMG) crop walk. Attendees reviewed key results from the trial and discussed practical applications of soil amendments and amelioration methods. Questions were raised about the specific amendments used and their mechanisms. This article provides an overview of the amendments trialled, including Ironman Gypsum, Compost – Humicarb, Biochar, and Frass.
What are soil amendments?
Soil amendments refer to organic or inorganic substances incorporated into soil to enhance its quality and support plant health. Their primary purpose is to modify the soil’s chemical, physical, or biological properties, thereby mitigating limitations or improving its overall functionality. Various amendments are tailored to address the unique requirements of specific soil types and plant species. For instance, materials like gypsum and lime alter soil characteristics, whereas compost and worm castings function as soil conditioners by enhancing its physical structure.
Ironman Gypsum
Ironman Gypsum is a secondary product derived from titanium ore processing, specifically a pelletised by-product of mineral sands processing. The material is a neutralised acid effluent stream from the leaching of iron-rich ore with sulfuric acid, which precipitates to form gypsum containing iron and manganese. This amendment offers a high sulfur content, high phosphorus absorption, and water retention capacity, and acts as a soil pH adjuster. Ironman Gypsum also enhances soil structure, boosts microbial activity, and contributes to nutrient retention. It has proven to be particularly effective in improving soil fertility and preventing phosphorus leaching, with implications for long-term soil health.
Compost – Humicarb
Humicarb compost is made from organic materials such as green waste, food waste, and animal manures, undergoing controlled aerobic composting to become a valuable source of carbon. This product plays a vital role in improving soil structure by stimulating aggregate formation, which enhances nutrient, water, and oxygen availability to plants. Additionally, it boasts high cation exchange capacity (CEC), helping soils store and release nutrients efficiently. Humicarb compost buffers pH and salt fluctuations, optimising soil chemistry for better nutrient efficiency. It is particularly beneficial for boosting microbial activity and promoting plant growth, as well as improving soil resilience to abiotic stresses and pathogens.
Biochar
Biochar is a stable, carbon-rich material created by heating organic material, such as crop residues, wood, or manure, in a low-oxygen environment. This process, known as pyrolysis, results in a product that enhances soil fertility by improving water retention, soil structure, and microbial activity. Biochar has several benefits, including increasing nutrient availability, raising soil pH, and mitigating climate change by sequestering carbon. It is also effective in remediating soil pollution, including organic pollutants and heavy metals. However, the effectiveness of biochar depends on the specific production methods, and different types of biochar may be selected based on soil and crop needs. While biochar’s long-term benefits are clear, there is a need for further research on its impact over extended periods in the field.
Frass
Frass is an organic fertiliser produced by the larvae of the Black Soldier Fly (Hermetia illucens), which feed on organic waste. This nutrient-rich by-product is gaining popularity for its ability to improve soil health and contribute to the circular economy by recycling organic waste. Frass provides essential nutrients, particularly nitrogen, which are readily available to plants. Additionally, it introduces beneficial biomolecules and microorganisms that promote plant growth, increase resistance to pests and pathogens, and enhance tolerance to abiotic stresses. Its application can support sustainable agriculture by improving soil fertility and reducing the environmental footprint of waste disposal. Since it has diverse biochemical properties influenced by various production and environmental factors, further research is needed to evaluate its potential for extensive use in crop production and agriculture.
Future Carbon Project site soil amendment properties
| Properties | Ironman Gypsum | Compost | Biochar | Frass |
| pH (CaCl2) | 8.0 | 7.0 | 7.1 | 7.7 |
| Electrical conductivity (dS/m) | 3.09 | 7.6 | 0.53 | 2.19 |
| Organic carbon (g/kg) | 5.5 | 51.6 | >99.5 | 93.7? |
| NH4-N (mg/kg) | <1 | 167 | 3 | 5488.33 |
| NO3-N (mg/kg) | 10 | 37 | 6 | 7.19 |
| Colwell P (mg/kg) | 8 | 952 | 117 | 5616.15 |
| Colwell K (mg/kg) | 61 | 8974 | 359 | 5887.77 |
| S (mg/kg) | 13274 | 6501 | 111 | 3690.84 |
| B (mg/kg) | 0.73 | 6.40 | <0.10 | 0.88 |
| DTPA Cu (mg/kg) | 1.10 | 11.6 | 3.56 | 0.88 |
| DTPA Fe (mg/kg) | 52.0 | 41.4 | 16.6 | 28.76 |
| DTPA Mn (mg/kg) | 20.9 | 117 | 3.72 | 0.40 |
| DTPA Zn (mg/kg) | 0.34 | 151 | 16.5 | 6.07 |
| Ex. Ca (cmol(+)/kg)* | 77.1 | 73.9 | 7.23 | 1.2 |
| Ex. Mg (cmol(+)/kg)* | 8.74 | 17.0 | 1.41 | 2.9 |
| Ex. K (cmol(+)/kg)* | 0.10 | 21.4 | 0.78 | 15.1 |
| Ex. Na (cmol(+)/kg)* | 0.85 | 12.0 | 0.56 | 6.5 |
| Phosphorus buffer index (PBI) | 6650 | 137 | 59.4 | – |
*Exchangeable cations (not pre-washed). Note: Frass PBI not recorded.
Conclusion
Soil amendments play a critical role in improving soil health and boosting agricultural productivity, particularly in regions like the West Midlands where soils face unique challenges. The amendments trialled in the Future Carbon Project – Ironman Gypsum, Humicarb Compost, Biochar, and Frass – each look to provide valuable benefits, including enhanced soil structure, increased nutrient availability, improved water retention, and greater plant resilience.
By exploring these innovative tools and understanding their unique properties, farmers can make informed decisions about the most effective solutions for their soils. Continued adoption of soil amendments may contribute to healthier, more resilient soils and sustainable agricultural systems across the West Midlands region.
Through the insights already gained and ongoing research, the Future Carbon Project is helping expand our understandings and knowledge of novel amendments to address soil challenges and build sustainable agricultural systems for the future. Find out more about the project on the project page, or join a farmer discussion group to get involved.
This project is supported by the Western Australian Carbon Farming and Land Restoration Program, The CRC for High Performance Soils (Soil CRC), and Future Green Solutions.
