Land surface plays a key role in mediating the release of greenhouse gasses (GHG) into Earth’s atmosphere and, as such, plays a role in driving climate change. Understanding and improving land health and use plays a crucial role in reducing emissions, together with addressing years of over cultivation and resultant soil depletion.
The main GHGs are carbon dioxide (CO2) and, at smaller concentrations but with greater global warming potential, methane (CH4) and nitrous oxide (N20). From 1978 to 2003 an assessment of soils and their carbon content across England and Wales in the National Soil Inventory showed soils were losing carbon in many areas. This was mainly due to land use and management changes but also, in part, due to warming. Since this survey, further research has revealed that in most areas there has been a continuous decline in the carbon content of our soil and it is highly likely that other temperature regions, along with the UK, would show a similar trend.
Today, agriculture covers 74% of the UK’s land and is responsible for 10% of all GHG emissions (Agricultural Statistics and Climate Change’ DEFRA, 2020). The over cultivation of our farmed land and change of use, resulting in peat bog depletion and deforestation, is driving up GHG emissions, carbon loss and soil depletion. The inefficient use of fertilisers results in nitrous oxide emissions, not only into the atmosphere but also into our waterways. The storage and use of manure and slurry also contributes, alongside rumination in livestock. The impact of livestock rumination, however, is less of a concern for the UK. Much of the UK’s grazed land is unsuitable for crops and can be identified as potential carbon sinks: land that absorbs and locks in atmospheric carbon.
A key player in the Earth’s carbon cycle, soil contains around three times more carbon than our atmosphere. In soil, the creation of solid organic carbon includes decomposing plants and animals. Gradually, the decomposition of this organic matter releases carbon into the atmosphere as CO2. Gas released from the soil into the lower atmosphere is called positive flux. Gas that is absorbed into the soil is called negative flux.
The balance between the two determines whether soils are a net source, or a net sink of GHG. How much carbon is held in our soil impacts its fertility, water quality, plant growth and microbial activity. Our ability, therefore, to monitor and measure carbon gases or flux, allows us an important insight into the health, not just our soil, but also our wider ecosystem and impact on climate change. As temperatures increase, so too does microbial activity, plant decomposition and CO2 emissions. There is, therefore, a need for more soil flux data and modelling.
The 2020 paper, ‘A field system for measuring plant and soil carbon fluxes using stable isotope methods’ by Christopher S. McCloskey, Wilfred Otten, Eric Paterson, Ben Ingram and Guy J.G. Kirk focussed on the lack of soil flux data and the trial use of a custom-made onsite system of dynamic automated soil flux chambers, using Soil Flux 360 instrumentation supplied by Agri-EPI.
“There is a lack of field methods for measuring plant and soil processes controlling soil organic matter (SOM) turnover over diurnal, seasonal and longer timescales with which to develop datasets for modelling. We describe an automated field system for measuring plant and soil carbon fluxes over such timescales using stable isotope methods, and we assess its performance.”
The team’s work confirms the suitability of the isotope methodology for partitioning net ecosystem respiration fluxes between plant and soil sources in such a system. It also clearly identifies differing diurnal and seasonal patterns in both plant and soil respiration and variation over the growing season, as Christopher McCloskey explains:
“The methods tested in this study have subsequently been used to generate data on plant and soil fluxes and their drivers over two growing seasons, such as air and soil temperature and moisture. This is being used to test how plants may affect the rate of soil organic matter turnover. These datasets may also allow the testing and improvement of models of soil carbon turnover, supporting our ability to predict how soil carbon stocks will respond to environmental change and factors which may contribute to the increase or loss of soil carbon.”
Our ability to understand the variations in soil and plant respiration and sequestration of carbon at different times of day, month or season together with different weather and environmental factors, will allow growers, producers and researchers to better understand the emissions triggered during the drilling of seed, fertiliser application and harvest, where in the geography of the UK are the best carbon sinks and research into what organic materials can be added to improve soil organic matter. Offering tangible, practical data and advice for farmers to deliver greater productivity with reduced emissions, sustainability and soil health, this type of data can help us answer key questions, such as:
The time saving achieved by the automated soil flux chambers’ accurate measurement and data processing means data is available in a fraction of the time taken by static chamber equipment. This was also demonstrated at Pamona College, California where monitoring soil flux in a commercial strawberry crop reduced the processing time from 68 days down to one day.
Research in other parts of the world is also contributing to our knowledge of soil flux. A group of researchers from the National Institute for Environmental Studies led by Naishen Liang focussed on forest locations. Aiming to produce long-term data about the effects of warming on microbial activity and CO2 flux, their results show soil temperatures have a considerable impact in forests and it’s hoped this work will support our better understanding of how climate change is affecting global forest ecosystems and their carbon cycles.
As outlined in UK Government’s Agricultural Policy, supported by the Environmental Land Management Scheme (ELM), there is an urgent need for long-held agricultural methods to change. The measurement and monitoring of soil flux is set to become an integral part of that shift; science supporting the drive to ensure we adjust our behaviour and practice to better balance food production and the health of our soil and natural world.
Meeting climate change challenges, Agri-EPI’s automated dynamic soil flux 360 chambers monitors and measure positive and negative soil flux. Read more about this solution.
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