Soil and soil conservation in the South West

Soil is the zone where plants take root and the foundation for terrestrial life. It varies in depth from a few centimetres to several metres and can be structured in terms of topsoil (the upper, more organically-rich layer) and subsoil (the underlying layer).

Most soils contain sand, silt, clay and organic matter, water and air. The make up of the soil determines the use and activities that it can support. There are nine major soil types in England and Wales that have developed over the last 10,000 years, as mapped below by the National Soil Resources Institute. The South West Region contains a wide variety of soils associated with its diverse range of landscapes.

Major soil groups in England and Wales

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Source: National Soil Resources Institute

Enlarged map showing major soil groups in the South West

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Soil types where you are

You can now find out what soil types are where you live, or at a place that you are interested in. The National Soil Resources Institute's Interactive Soilscapes Viewer is a free online resource that enables you to learn more about the soils in your region, and across England & Wales.

You can input your postcode into this facility and discover more about the soil resource under your feet.

Soil structure and condition

Soils support crops as well as help to regulate water flow, water quality and flooding, protect buries archaeological remains and support wildlife. According to the Guide to Better Soil Structure published by the National Soil Resources in 2001, soil structure is important because:

It is the plumbing system for the soil, which controls water and air flow;
It provides space, and a protected home, for roots, germinating seeds and soil fauna;
It affects farming operations including the ease of cultivation and the response to the soil to tillage and stocking;
It affects the impact of land use on the environment including the amount of run-off and erosion, the amount of nutrients lost in drainage, run off and / or erosion and the amount of pollutants lost from farms in erosion / runoff and / or drainage.

More information about what affects soil condition and structure is available here.

The sustainable use of soils in the South West

Healthy soil is vital to a sustainable environment and an essential resource for life. However, human activity have had a significant impact on soil condition as a result of agriculture, drainage, extraction, waste and development. These pressures can lead to the loss of soil structure, soil erosion, contamination, acidification and the loss of biodiversity

The region’s high rainfall, steep slopes and vulnerable soils result in increasing problems with water pollution and run off. Furthermore poor soil structure leads to an inability of crops and soil to make best use of manure and fertilisers.

Soil types at highest risk are sands, loamy sands, sandy silt loams and silt loams. Areas of the SW of greatest concern include (see also map below):

The Devon Redlands
Sandy soils in the South Hams
Sandy silt soils in West Cornwall
Sandy soils in the Vale of Taunton
The Yeovil sands
The Vale of Pewsey

Preliminary research suggests that 81% of cultivated land on silt and find sandstone landscapes in the South West has severely or highly degraded soil structure (Palmer, 2003).

Erosion

It is stimated that 2.3 million tonnes of agricultural soils was lost (nationally) between 1995 and 1998 (Policy Commission on the Future of Farming & Food, 2001). Around half of all land in the South West is thought to be at risk and about 6 % of agricultural soils already suffer from erosion.

Land that is at high risk and very high risk to soil erosion includes the sandy soils in south and east Devon, and north and south Somerset.

Much of the rest of the Region's grassland farms are on heavy soils, which poach readily when wet, notably in autumn and spring. Poaching encourages the type of runoff from the land that may contribute substantially to fine sediment polluting rivers and streams. The most susceptible are the heavy grassland soils in north Cornwall and mid Devon and the clay vales of the east of the Region.

Whilst erosion is part of a natural cycle, the influence of human activities can speed up the process and cause problems. Examples of this include the erosion of fertile top soils from worked fields and its deposition with associated pollutants in watercourses, or the erosion of sand from a beach which is then not replaced because the natural source has been blocked by coastal defences elsewhere.

Erosion may increase as a result of climate change

Distribution of vulnerable soils in the South West

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Source: Commissioned by the Environment Agency from the National Soil Resources Institute (2003)

These areas of the Southwest soils have an inherent vulnerability to structural problems and are easily sealed by heavy rain causing local flooding, mud on roads and damage to property.

This also causes water pollution as sediment and pollutants enters rivers affecting river habitats and spawning grounds for salmon, trout and other aquatic wildlife. Incidents associated with soil structure problems increased in recent years, and this would also be made worse through the predicted changing weather patterns associated with climate change with climate change.

See climate change for more information.

What affects soils structure and condition

The quality, extent and diversity of soil is mainly affected by erosion, extraction and development.

Soils can break down because of the loss of organic matter and topsoil stability (because of over-cultivation), and soil compaction due to ill-timed traffic, working or stocking. Compaction alone can reduce yields by 30% (wheat on heavy soils) to almost 70% (peas on light soils) (National Soil Resources Institute, 2001).

While farming is the biggest user of land, any activity on wet ground, whether for agriculture, forestry or leisure, risks damaging the soil. Important consequences are losses of permeability and water storage capacity. This accelerates runoff, and adds to erosion and flooding. This in turn carries soil and pollutants from the land as mud and sediment. (see also 'erosion', 'flooding' and 'diffuse pollution')

The Environment Agency's web pages on soil contain useful information on the threats to soil type and quantity, legislation and useful links.

These threats include:

Acidification
Erosion
Agriculture
Compaction from machinery
Peat extraction
Tourism

Influence of different soil types

Different soils degrade differently, and both physically and chemically. Sandy and silty soils can form a hard cap or slump easily when frequently cultivated, making them susceptible to overland flow (water flowing over the surface instead of soaking into the ground) and erosion.

On the other hand, clay soils with slow natural drainage can be made wetter by ploughing or by grazing and trafficking at wet times.

Other soils, notably those with naturally good drainage and free calcium carbonate, are more resilient, degrade less easily and recover more readily following physical damage.

Upland soils are inherently acidic and are at risk from further acidification from fallen leaves and acid rain. This is not such a problem in the east of the Region on chalk, limestones and calcareous clays because the soils are alkaline and so resist acidification.

The State of soils in England and Wales & Soil Action Plan 2004 - 2006

A report summarising the State of Soils in England and Wales has been published by the Environment Agency. This report gives an indepth review of:

The importance of soil
The interdependence of soil, water and air - erosion, nutrient loss, climate change and air pollution
Soil wildlife and biodiversity - soil organisms and habitat protection, including agri-environment schemes
Producing food and fibre - arable crops, livestock and forestry; manure, slurry and waste; and the quality of agricultural soils
Providing raw materials - the impacts of mineral and peat extraction; water resources
The built environment - the loss of soil to development; flood risk; and soil contamination
Cultural heritage - damage to archaeological remains in the soil

The principal conclusion of the report is that there is not enough good quality information on the soils of England and Wales, making it difficult to develop effective policies for its protection.

Working in conjunction with the State of Soils in England and Wales is the first ever Soil Action Plan 2004 - 2006, launched by Defra in 2004. This plan is aimed at policy makers, industry leaders and influencers across the wise spectrum of activities impinging on soils. It sets out the actions which Defra and partners are committed to take to help protect our soils.

The vision behind this action plan is "to ensure that England’s soils will be protected and managed to optimise the varied functions that soils perform for society (e.g. supporting agriculture and forestry, protecting cultural heritage, supporting biodiversity, as a platform for construction), in keeping with the principles of sustainable development and on the basis of sound evidence."

The Action Plan addresses issues under eight key headings:

Protecting Soils in the Planning System
Minimising Contamination of Soils
Predicting and Adapting to the Impacts of Climate Change on Soils
Soils for Agriculture and Forestry
Interactions between Soils, Air and Water
Soils and Biodiversity
Soils, the Landscape and Cultural Heritage
Soils in Minerals Extraction, Construction and the Built Environment

New UK-wide survey of pollutants in soils and plants

The Environment Agency have carried out the first ever survey of soils and plants throughout the UK.

The UK Soil and Herbage Survey analysed soil and vegetation from 122 rural, 28 urban and 50 industrial sites. The survey tested for concentrations of dioxins, polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs) and a range of metals across the UK.

For many contaminants, the survey provides the first coherent picture of their concentrations across the UK. The results provide a reliable baseline against which intensive local surveys and future national surveys can be assessed, and will help the Environment Agency and others to monitor and remedy pollution events more efficiently.

Key findings:

For all the metals studied (and arsenic), concentrations in industrial soils are significantly higher than in rural areas. Concentrations of copper, lead, mercury, nickel, tin and zinc are higher in urban soils compared with rural soils, probably reflecting the presence of significant industrial activity in urban areas in recent times. Herbage concentrations of chromium, copper, lead, nickel, titanium and zinc are higher in urban and industrial areas compared with rural areas.
Significantly, the survey found that concentrations of dioxins, one of the most toxic and persistent group of contaminants, have fallen by about 70% since the late 1980s when restrictions on emissions from major industries were introduced.
Urban and industrial areas are still sources of polychlorinated biphenyls (PCBs), with concentrations about double those in rural areas. Although PCB production was banned in many countries in the 1970s and their use closely regulated, PCBs are still a major environmental problem worldwide. They can cause serious environmental damage because they are toxic, don't easily break down and can accumulate in the tissues of fish, birds and mammals.
Polycyclic aromatic hydrocarbons (PAHs - a persistent organic pollutant) show the largest urban and industrial footprint of all the chemicals studied, with concentrations up to seven times higher than in rural areas. Road traffic and domestic fuel combustion may now be the main sources of PAHs in urban and industrial areas
Differences between England, Scotland, Wales and Northern Ireland. Some reflect the complex geology of the British Isles. For example, high levels of titanium in soils from Scotland and Northern Ireland reflect the occurrence of titanium-rich basaltic rocks in these areas, rather than man-made pollution.

The survey results will help inform future Government policy on contaminant sources and how they are controlled and regulated, and also provide a baseline for assessing future local surveys and national trends.