Soil carbon: what we’ve learned so far
NRM
Agriculture
The Earth’s soil contains about 2,500 gigatons of carbon. The good news is that equates to more than 3 times the amount in the atmosphere, and 4 times the amount stored in living plants and animals.
The bad news is that soils only remove about 25% of the planet’s carbon emissions from fossil fuels annually by sequestering it. Significant carbon loss is also happening around the world. Soils have lost 50-70% of the carbon they used to have because over half of the land that can sustain plant life has been converted to croplands, pastures, and rangelands.
We need to take action now. Thankfully, agriculture is in a unique position to help. While it’s a source of carbon, it’s also a huge carbon sink, meaning we can sequester more than we can produce if we adopt sustainable farming practices. Benchmarking and increasing soil carbon levels is also beneficial for improving farm productivity and profitability. Read on to learn more about soil carbon, what analysis has told us so far, and how levels can be raised.
What is soil carbon and why should farmers measure it?
Organic and inorganic carbon is vital to the soil ecosystem. Organic carbon is particularly important. It gives greater physical stability in the soil, increases oxygen levels, improves water drainage and retention, and reduces the risk of erosion and nutrient leaching.
Monitoring and benchmarking soil health for year-on-year improvement is made easy with soil carbon analysis. Regular testing also enables growers to assess the impact of sustainable farming practices, as well as crop nutrition plans, and to adjust where needed. There are plenty of benefits of building organic carbon levels, such as increased microbial activity, enhanced nutrient supply, and greater yields.
Soils with a higher carbon content represent profitable and productive sinks for carbon stocks—read our section on what analysis has told us so far to see if your types of soils have potential. Accurate measuring and monitoring of soil carbon are also vital for any income relying on carbon sequestration. This means that increased carbon levels provide an exciting new opportunity for farmers, so get a head start now to take advantage.
The environmental impact of carbon sequestration
The pressures of climate change and global warming have led to governments and bodies all over the world seeking innovative solutions. Soil carbon has been found to be at the centre of regenerative agriculture. As soil can hold three times more carbon than the atmosphere, the land acts as a huge carbon sink. Increasing soil carbon levels is therefore seen as a key opportunity to reverse atmospheric carbon dioxide pollution.
Ultimately, carbon capture and storage can help us reduce the amount of carbon dioxide in the atmosphere over the next few decades, giving us breathing space until we can effectively implement sustainable practices and a low carbon economy.
What has analysis told us so far?
NRM launched our CarbonCheck service in 2021. Since then, we received 4,000 samples from a variety of different agricultural sectors, analysing organic matter, C:N ratio, total carbon, active carbon, and more.
Our results so far have found:
- Land which is completely undisturbed, with permanent cover managed for conservation (such as nature reserves and other natural habitats), will generate the highest carbon content. These soils represent profitable and productive sinks for carbon stocks. As there is permanent biomass cover with lots of natural vegetation above and below ground, carbon is continuously being added to the system. Carbon loss is also minimised.
- Cultivated land generally contains lower carbon stocks and less organic matter. This is a result of the movement of soil in crop production. As air is introduced, organic matter breaks down more quickly and reduces biological activity. It is therefore unsurprising that the arable sector shows the lowest levels of carbon and organic matter, although we expect this to improve as more growers embrace regenerative agriculture.
- Land used for livestock falls somewhere in the middle. It benefits from the readily available manure, which naturally adds to carbon stocks year-on-year. It is also cultivated less than other soils.
NFU President undertakes soil carbon analysis with NRM
Minette Batters, NFU president, has already started on her soil carbon journey. Last year, she had her fields tested with CarbonCheck, and was delighted with her soil carbon levels, which came back higher than NRM’s dataset average of over 4,000 samples. The farm’s average adjusted organic carbon stock (in tonnes per hectare) was 129 t/ha whilst NRM’s dataset average comes out at 98 t/ha, and their Soil Organic Carbon (SOC) level was 1.7% higher than the dataset average.
By comparing the results for her different fields, Minette could determine what that meant for her future crop nutrition plans.
How can we raise carbon levels in our soils?
Our results show that disturbing the soil limits the amount of organic carbon being built in the soil, resulting in lower carbon stocks and less soil organic matter. However, not all is lost—arable farmers should work with advisors to adjust their management practices. This will lead to significant carbon gains over time.
You should also consider adding organic material within your crop rotation. These products are used effectively to build soil organic matter and ultimately soil carbon stocks, improving soil structure and stability. For further advice, speak to your agronomist or contact us.
NRM is helping to forge a standard for the new soil carbon code. This will help set an industry standard to be adopted nationwide for the accurate sampling, measurement, and assessment of soil carbon, allowing for benchmarking and comparisons between farms.
Our CarbonCheck measures organic carbon as part of a comprehensive analysis suite, enabling farmers to benchmark their soil health. To book in your samples today, talk to your agronomist or feel free to get in touch.
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