Soil presentation francesca baylis final web
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Soil contains 3 times as much carbon as the atmosphere, stored as organic matter. The largest carbon stores are in permafrost, peatlands, and wetlands. Threats to soil degradation cost the UK economy in 2010. Management practices like no-till farming, cover crops, and reducing chemicals can increase soil organic matter. Government initiatives in the UK aim to protect soil carbon stores through agricultural policies and reporting on soil health.
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Soil presentation francesca baylis final web
- 1. Click to edit Master title style The significance of soil for carbon Dr. Francesca Baylis
- 3. What carbon is in the soil? • 3x as much carbon in soil as in the atmosphere • Carbon is deposited in soil as organic matter • Soil degradation cost the UK £1.2 billion in 2010 • Most of stored soil carbon is in the permafrost, peat, and regions with more rainfall (especially wetlands!)
- 4. What are the threats to soil?
- 5. How can soil be managed for carbon? • Organic matter increases – Planting crops with deeper root lengths – Prevent disturbance: No till – Encourage soil microbes – Cover crops and green manure – Reduce use of chemicals and synthetic fertiliser • Biochar and enhanced weathering
- 6. Soil policy and initiatives • DEFRA 25 year plan • Agriculture Bill • ELMS • EA state of the environment for soil report • CCC Land Use: Policies for a Net Zero UK • 4 per 1000 movement
Editor's Notes
- Describe soil structure and components. (Mineral are sand silt and clay) Rhizosphere is the best part of the soil due to increased nutrient cycling and microbes. 10-1000x more bacteria in rhizosphere than other parts of the soil. Soil is a non-renewable resource, takes 100 years to generate 1cm of topsoil so needs to be managed well. Quarter of earths biodiversity is held in the soil. Talk briefly on soil health, (defined by EA as the continued capacity of soil to function as a vital living ecosystem that sustains plants, animals and humans). Soil health is a combination of physical, chemical and biological factors, and includes nutrients and acidity, organic matter content, structure, water capacity, biological activity, pollution . Therefore difficult to really quantify but all aspects needed for soil to function effectively. It also varies depending on the type of soil being considered, with heathland looking very different to arable soil and having different parameters to health.
- Some of you may be familiar with the carbon cycle shown on the right here. (Talk through the cycle) As you can see there is only one arrow bringing carbon back down from the atmosphere and that is photosynthesis. From there the carbon goes through the cycle and enters the soil through dead organics and waste products. However the cycle is overly simplified and really doesn’t emphasise how important the soil is in this cycle. The EA state of environment for soil report states that soil holds three times as much carbon as the atmosphere, and UK soil alone is thought to hold 10 billion tonnes of carbon. Organic matter is the key part of soil that stores carbon (the bit that makes it look dark and rich). Three types, the living matter stored in plants and microbes which will remain in place until they die. The active organic matter is recently dead organisms, root exudates, manure and crop residues, this is the part most microbes eat and so release back into the atmosphere through respiration. Then there is the stable organic matter, often called humus, which is what the fresh organic matter becomes once it’s been decomposed. This is the carbon which stays in the soil a long time. However science is showing that soils are losing their stored carbon through current management techniques. In particular intensive agriculture in arable soils has been responsible for a loss of 40-60% of organic matter in these soils. Currently 4million ha at risk of compaction and 2million ha at risk of soil erosion. DEFRA research by Cranfield University calculated that quantifiable soil degradation cost the UK £1.2 billion in 2010, of which 47% was associated with the loss of organic carbon in the soil.
- Focus on the loss of organic carbon but all factors are important and can contribute to carbon. For loss of organic carbon, it’s a serious concern. Lots of different reasons for organic carbon being lost: Ploughing, over half of soil carbon in the top 30cm of soil so ploughing of established grassland or temporary crops reduces soil organic matter by allowing this to be released to the atmosphere Planting monocultures Loss of crop residues, naturally these would rot down and put carbon back into the soil but by removing these we lose the carbon already there Deforestation and loss of permafrost Compaction reduces pore size and thus the air content of the soil. This prevents soil organisms from moving through the soil, reduced the air content of the soil and so limits the microbes that can live there, and also stops the roots of the plants and so stops living carbon from building up deeper in the soil. Erosion can affect soil organic carbon as carbon can be carried off in runoff, however even more significant effects are seen for agri-production and flooding. Sealing and loss of soil biota are also really important but currently we don’t have any data to show the impacts they can have. However we must remember them and that they are likely to become more prominent in coming years.
- Already mentioned microbes as carbon stores but there has also been attention of how microbes aid the formation of something called microaggregates, these help clump soil and further trap carbon dioxide in the soil. Deeper root lengths: Most carbon stored in the top 20% of soil, deeper roots help to increase carbon deeper in the soil both through living organic matter of root and microbe and also eventually increasing the active and stable. A similar thing can be achieved through deep ploughing (not regularly) to help move carbon from the surface of the soil to further down. However you will want a diverse range of different plants for maximum benefit. Prevent disturbance: no till. As this reduces/breaks up the aggregates which releases carbon and also makes the soil structure more prone to losing it’s structure. Encourage soil microbes: microbes secrete the compounds for soil aggregation and aid nutrient cycling, This helps store carbon but can also enhance other factors such as reducing the use of synthetic fertilisers. AMF are particularly important as they can transfer 15% more carbon to the soil than other microbes. Cover crops: prevents soil erosion but also if no plants producing exudates for microbes to eat they’ll eat what's in the soil, so reduce carbon content. Green manure: a form of cover crop, fast growing plants used to cover bare soil. This prevents erosion and so loss of carbon this way, but can then also be turned over while still alive and turned into a form of fertiliser as they rot and break down. Reduce chemicals and synthetics: Synthetic fertilisers reduce root exudates and therefore don’t support the microbes. High P environments reduce AMF and so can reduce carbon sequestration. Reducing use of pesticides can also help to encourage your microbial community. You won’t ever kill of all the microbes by using pesticides but you will affect the diversity of what is present and can have effects on non-target species. A little bit more out there and less biology based. Currently lots of work looking at biochar and enhanced weathering. Biochar: Plant matter heated without air. Can take centuries for the charcoal to break down and can help with trapping nutrients and water. Alternatively enhanced weathering is where rocks that react with CO2 are broken down to smaller pieces and spreading them on farmland. This increases the surface area of the rocks and so allows them to more quickly absorb CO2. However takes a lot of energy to grind up the rocks so we will have to see if this ends up being possible. Important to say that farmers are already doing a lot of these things because better soil tends to give better yields. However more can be done to help them or to follow their example on other land types.
- DEFRA 25 year plan calling for soils to be managed sustainably by 2030 and to give soils a greater focus and attention equivalent to air and water. Agriculture Bill: soils have been included and it outlined the beginnings of ELMS. ELMS: currently consulting on shaping this to replace CAP, discussion is open but will look to pay for the public goods land provides to incentivise land owners. EA report gives a comprehensive summary of the UK’s soils and the further need for action CCC policy called for an increase in low-carbon farming practises for soils and livestock, in fact NFU have also set a target to be carbon neutral by 2050. 4 per 1000 movement, Government signed up at COP21 in 2015 but haven’t so far done much with this though the polici9es that could help are starting to emerge.