Research & References
Although we depend on soils, across the world soils are being damaged by human activity.
It has been estimated that
- Around one-third of the world’s arable land has been lost since 1960 as a result of soil degradation .
- Approximately 25% of the world’s soils are severely degraded .
- We lose the equivalent of 30 football fields of soil every minute to degradation .
To halt the damage being done to our soils and restore them to health, we have committed to a goal of increasing soil organic matter (SOM) by 20% over the next 20 years. Increasing SOM has numerous benefits.
Water storage, floods and droughts
Healthy soil reduces the risk of floods, storing as much as 3,750 tonnes of water per hectare—that’s one and a half Olympic swimming pools . For degrading UK arable soils, which can contain as little as 1-2% soil organic matter in total, meeting our target would increase the water holding capacity by 40-100 thousand litres per hectare .
This means farmers can play a huge part in reducing the risk of localised flooding, at the same time as making their own farms more climate resilient – not only to floods, but also to droughts. Healthy soil also protects underground water supplies by neutralising or filtering out potential pollutants .
Soil erosion by water has recently been highlighted as a major problem in Europe, with the UK contributing 5% to Europe’s total  despite occupying only 1% of Europe’s land area. Increasing SOM levels reduces the amount of sediment and nutrients washed into rivers.
The International Panel on Climate Change states that 89% of all agricultural emissions can be mitigated by improving soil carbon levels . An increase of 20% based on the UK average soil carbon density would suggest nearly 10 tonnes more soil carbon per hectare could be stored by 2035 – around 0.47 tonnes per hectare every year .
Organic farms in North-West Europe have on average around 20% more SOM than non-organic, and demonstrate that meeting our target would result in major carbon gains. Recent meta-analysis found that organic farms store on average 0.27 to 0.45 tonnes more carbon in topsoil per hectare per year . Even at the low estimate of 0.27 tonnes, extrapolating this across the UK suggests that around 1.3Mt more carbon can be stored in UK soils every year . This is equivalent to the carbon sequestered annually by an area of forest three-quarters of the size of Wales, or to the emissions saved by taking nearly 1 million cars off the road .
To achieve our goal, we’ve outlined seven ways to increase the organic matter in our soils:
- Increase the amount of plant and animal matter going back onto fields. Soil organic matter is an essential element to healthy soils – achieving high levels is the key to soil health. Levels are low or declining on many UK farms - we urgently need to work together to reverse this trend by ensuring farms are recycling more plant and animal matter back into soils.
- Improve soil health monitoring across the UK. Analysing soils is an essential first step to support effective decision making on soil health, but some farmers neglect to do this routinely.
- Encourage soil organisms – both those that build up soil and those that release nutrients. The current focus on chemical inputs began at a time when we didn’t yet understand the importance of soil life. We are now realising how important soil biology is to farming. We need to learn how best to support this life in order to improve our ability to cope with floods and droughts and improve crop productivity.
- Cover up bare soil with continuous plant cover. You can’t see healthy soil – it is covered by plants. Plant roots hold soils together, reducing erosion, and allowing air to penetrate in spaces around roots. Roots also encourage healthier soil communities through plant-fungal interactions. But benefits spread beyond the farm – huge gains can be seen in terms of biodiversity, carbon storage, flood and drought control, and water quality.
- Bring more trees onto farmland. Trees provide shelter for livestock in inclement weather and act as a windbreak for crops. They also can decrease runoff and soil erosion, and can increase soil organic matter and overall soil nutrition.
- Reduce soil compaction from machinery and livestock. Soil compaction is a major problem in the UK – it can lead to increased surface run-off as well as drought stress, fewer grazing days, poor root growth and reduced yields overall.
- Design crop rotations to improve soil health. The current fashion in farming for simple arable crop rotations, financial pressures and the increasing trend for short-term tenancies all put pressure on farmers to make short-term decisions. The result is a drop in UK food diversity, weeds which we can no longer control and soils which are being stripped of their nutrients and organic matter. To reverse this we need to ensure farmers are able to design diverse, long-term crop rotations that our soils need.
-  WRI (1994) – World Resources Institute, New York, Oxford University Press
-  FAO (2011) State of the world’s land and water resources for food and agriculture
-  http://www.ifoam.bio/en/news/2015/04/21/press-release-ifoam-organics-internationalcalls-stop-soil-destroying-international
- [4,6] European Commission Joint Research Centre European Soil Portal – ‘key facts about soil’
51% SOM = an additional 20,000 to 25,000 gallons per acre, or at least 225,000 litres per hectare. 0.2-0.4% increase (20% increase on 1-2%) = 45000 to 90000 litres. Based on Byrant L. (2015) Organic Matter Can Improve Your Soil’s Water Holding Capacity
-  Panagos et al (2015) ‘The new assessment of soil loss by water erosion in Europe’, Environmental Science & Policy, 54: 438 – 447
-  An estimated 89% of the global potential for agricultural greenhouse gas mitigation would be through carbon sequestration. Smith P et al, (2008) ‘Greenhouse gas mitigation in agriculture’. Philosophical Transactions of the Royal Society of London, Series B Biological Sciences (2008) 363: 789-813
-  The Countryside Survey 2007 found the average soil carbon density in Great Britain’s arable and horticultural soils in 2007 to be 47.3t C/ha.
-  Note this is based on global figures. Based on the average difference in carbon sequestration rates between organic and non-organic farms, found in the Gattinger et al (2012) global meta-analysis of comparative studies
-  Taking the total croppable area of the UK as 4.8m ha, (https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/355868/structure-jun2014final-eng-18sep14.pdf)
– an increase of 0.27 megatonnes of carbon per hectare would mean an increase of around 1.3 million (1296000) tonnes of carbon.
- Based on the USA’s Environmental Protection Agencies Greenhouse Gas Equivalencies Calculator