Soil Groups

Use the flowchart on pages 10 and 11 of AHDB’s Healthy Grassland Pocketbook to identify what soil type you have on farm.

Soils of this type are characterised by:

• Having a low clay content in the topsoil, and include sand, loamy sand, sandy loam, sandy silt loam and silt loam textures.
• Having a low aggregate stability due to the low clay and organic matter content
• Dispersing readily in water causing slumping and capping at the surface
• Where these soils are free draining and well-structured they have a low risk of run off.
• When drainage is impeded by high water table or slowly permeable subsoil, they are at high risk of structural damage and run off.
• Being at high risk of wind and water erosion.

• Include sandy clay loam, clay loam and silty clay loam
• Tend to have a higher clay content (19-35% topsoil) which allows for better aggregate stability
• Soils in this group that have a high silt / fine sand content are less stable and are prone to capping, especially when there is low organic matter
• Clay content in the subsoil affects drainage.  Where clay content is low in the subsoil the soil can be freely draining with low risks of structural damage.  When the clay content is high, they are prone to water logging and structural damage
• Structural damage or poor drainage can lead to runoff and soil erosion particularly in areas of high rainfall and on slopes

Source: Think Soils, developed by the Environment Agency

Heavy soils are characterised by having a clay content of more than 35%. Common soils textures that are classed as heavy include sandy clay, clay and silty clay.

Heavy soils tend to be naturally slow draining and can lie wet for long periods of time.

Some clay soils are naturally well structured, which lessens the threat of waterlogging. How stable the clay particles are, is dependent on the type of clay and the calcium content. Less stable acidic clays have a lower porosity and a higher risk of run off than calcareous clays.

Heavy soils that drain slowly have a higher risk of structural damage and also of generating runoff, but have a lower risk of losing soil particles by erosion.

These soils are thin, often less than 30cm deep. They are highly calcareous, often with a medium textured topsoil.

These soils tend to have highly stable aggregates and form a strongly developed structure. Topsoil can be lost on these soils which can expose the bedrock, often due to soil moving down slopes.

These soils tend to be naturally well draining and will take winter rainfall with a low risk of runoff.

Peat soils include all soils where the organic matter content of the topsoil is more than 20%. Soil textures characterised as peaty include peaty sand, peaty loam, loamy sand, loamy peat and peat textures.

Peaty soils are widespread in the uplands and also found in lowland bogs and river valleys. They can be very productive agricultural soils.

Peaty and organic soils that lie wet in the uplands have limited capacity to accept winter rainfall, as such they are at high risk of generating runoff and soil erosion. In the lowlands and drier parts of the country, peaty soils are prone to wind erosion because of their low density and loose soil structure.