Slaking
Definition
Slaking is a form of soil structural degradation where soil aggregates break down into individual particles. This process leads to the separation of soil particles and the formation of a compacted surface layer composed mainly of fine particles such as clay and silt.
Formation of slake crust
When slaking occurs, the fine particles settle and create a dense, hard layer known as a slake crust. This crust significantly reduces soil porosity and surface permeability, making it harder for water to infiltrate and for seedlings to emerge.
Impact on crop growth
The presence of a slake crust poses several challenges:
- Poor germination: Seeds struggle to penetrate the hardened surface layer.
- Restricted root development: Limited soil aeration and compaction hinder root growth.
- Reduced water infiltration: Increased runoff and decreased moisture availability for crops.
Factors influencing slaking risk
The likelihood of slaking depends on the soil’s particle composition and organic matter content:
- Clay, silt, and sand ratio: A balanced mix of these particles increases slaking risk.
- High risk zone: Soils with 10–20% clay are most susceptible.
- Low risk zone: Soils dominated by either sand or clay particles pose the least risk.
- Organic matter: Higher organic matter generally reduces slaking by improving soil structure.
Management strategies
To minimise slaking:
- Increase organic matter through compost or cover crops.
- Avoid excessive tillage that disrupts soil aggregates.
- Use soil conditioners or amendments to stabilise structure.
