This classification of soils into different groups allows you to understand the risks associated with erosion and runoff, and the potential mitigation options that are available to you.
Sandy and light soils
- Soils with low clay content in the topsoil, and include sand, loamy sand, sandy loam, sandy silt loam and silt loam textures.
- Low aggregate stability due to the low clay and organic matter content
- Disperse 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.
- They are at high risk of wind and water erosion.
Click here to read about how a grower on the Isles of Scilly manages the sandy soil on his farm.
- Include sandy clay loam, clay loam and silty clay loam
- Higher clay content (19-35% topsoil) allows a 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
- Soils with clay content of more than 35% and include sandy clay, clay and silty clay textures
- Naturally slow draining and lie wet for long periods
- The stability and porosity of clay is dependent on the type of clay and the calcium content. Less stable acidic clay have lower porosity and higher risk of runoff than calcareous clays
- Heavy slow draining soils have a high risk of structural damage and generating runoff, but have a low risk of erosion
Source: Think Soils, developed by the Environment Agency