- Carbon is present in the soil in many different forms.
- Including a pasture phase and pulses/legumes in the cropping rotation is essential to improve soil organic matter and nitrogen levels, promote microbial activity and ultimately increase soil organic carbon.
- Evaluating management practices to increase soil carbon is necessary to ensure they are economically viable for a farming business.
- Several environmental factors (rainfall, evaporation, solar radiation, and temperature), as well as soil type, nutrient availability and land management influence maximum soil organic carbon storage capacity
What Is Soil Carbon?
Soil carbon can occur in organic and inorganic forms.
Organic = decaying plant material, soil organisms and microbes, and carbon compounds such as sugars, starches, proteins, carbohydrates etc.
Soil organic carbon makes up 58% of total soil organic matter and is measured by a laboratory test.
Inorganic = mineral-based, most commonly calcium carbonate.
Environmental factors determine the balance of organic and inorganic carbon in the soil. Soil organic carbon content is generally higher in cool, wet environments, whereas inorganic carbon is higher in semi-arid environments.
Soil organic carbon is roughly three times larger than the amount of carbon stored in vegetation and double the amount stored in the atmosphere.
Carbon Neutral Farming – Increasing Soil Organic Carbon
Organic carbon stocks in Australian soils are much lower than the global average and have been identified as a critical area for improvement in Australian agriculture.
With the Australian red meat sector aiming to be carbon neutral by 2030, Is carbon neutrality becoming the new minimum standard? How can we manage and improve our soil carbon levels?
Capacity is a crucial element of successful change. There is a capacity for change in cropping and livestock systems across our region.
Reducing grazing pressure on pastures and preventing soil degradation through erosion, salinity, soil acidity, or alkalinity plays a significant part in soil carbon management. Management options that may increase soil organic carbon:
- Stubble retention, eliminating burning and grazing
- Replacing fallow with cover crops – losses of carbon during fallow are mitigated
- Inclusion of pasture in the rotation - pastures generally return more organic carbon to soil than crops
- Addition of organic matter (e.g., manure)
Soil carbon is closely related to various biological, chemical, and physical soil processes. Therefore, soil organic carbon is a ‘headline’ indicator for detecting a change in soil condition. Regular testing from the same positions provides a means to track changes in carbon storage and an opportunity for trading excess carbon credits.
Note: Trading carbon credits can be risky as soil carbon levels can fall significantly during drought. Your business may require those credits to maintain carbon-neutral certification.
Soil Carbon Projects by Riverine Plains Inc.
Riverine Plains Inc. carried out the soil carbon project from 2012 to 2016. The project aimed to understand key drivers in managing carbon in farming systems through the publication of research and farmer case studies. Key findings from this project were that:
- Post-harvest fertiliser application does not have a measurable impact on soil organic carbon in the first year of application. A positive impact may be seen after 5-10 years of application, but the monetary value of soil carbon would have to be significant to receive a return on investment.
- There are benefits in continuing to focus on maintaining soil cover and soil organic matter; even if soil organic carbon levels do not increase, maintaining high microbial activity is beneficial for physical, biological, and chemical soil properties.
In 2018, Riverine Plains and Central West Farming Systems partnered with Mars Petcare to develop an industry program, to quantify greenhouse gas (GHG) emissions from wheat production, and identify avenues to support farmers in reducing emissions, with a focus on soil health.
The project has gained support from Kellogg’s, the Manildra Group, Charles Sturt University, Food Agility Cooperative Research Centre and Allied Pinnacle and is now known as the Cool Soils Initiative (CSI). The key aim of CSI is to support grain farmers in reducing GHG emissions, leading to increased long-term sustainability and yield stability through adopting innovative agronomic strategies to improve soil health. The latest GHG emission results are available in the September Riverine Plains Newsletter. Increasing soil carbon levels will help neutralise the impact of greenhouse gases released into the atmosphere.