The "mortar" on top of soil refers to a surface crust, or cap, formed by the binding of soil particles in the top few millimeters. This crust is a critical factor in soil stability and erosion prevention, particularly during crop establishment.
Here's a more detailed breakdown:
- Formation: This "mortar" effect is created when soil particles are bound together at the surface. The binding agents can be various substances, including:
- Clay particles: These act as a natural glue.
- Organic matter: Decomposed plant and animal residues also help bind soil together.
- Microbial byproducts: Substances produced by soil microorganisms contribute to soil aggregation.
- Polysaccharides: These are sugar-based compounds created by microorganisms and plant roots that act as binding agents.
- Function: The primary function of this surface crust is to protect the underlying soil from erosion by wind and water. Specifically, it:
- Prevents wind erosion: It binds soil particles together, preventing them from being blown away, especially during the vulnerable period after planting but before the crop has established a protective canopy.
- Reduces water erosion: The crust provides a more resistant surface to the impact of raindrops, reducing soil splash and runoff.
- Persistence: The effectiveness of this "mortar" layer typically lasts for several weeks (at least 6 to 8 weeks), which is a critical period for crop establishment. After this period, the crust may break down due to weathering, tillage, or other disturbances.
- Importance in Agriculture: Maintaining a stable soil surface is vital for successful crop production. The "mortar" effect helps to ensure that seeds are not blown away, and seedlings are not eroded before they can establish their root systems.
In summary, the "mortar" on top of soil is a naturally occurring or enhanced surface crust that binds soil particles, protecting the soil from erosion and facilitating crop establishment.
