Formation of Soil Structure
- Soil structure refers to the arrangement of soil particles into aggregates, which influences soil’s physical properties.
- The formation of soil structure is affected by various natural and human-induced processes, leading to the development of a soil profile with different aggregate sizes and characteristics.
Key Processes in Soil Structure Formation
- Frost and Heat:
- Effect: Both frost in winter and heat in summer remove water from the soil.
- Result: As the water evaporates, clay particles are pressed closer together, forming mechanically created aggregates.
- Chemical Processes:
- Effect: Organic materials, iron, aluminum oxides, and carbonates act as binding agents, stabilizing soil aggregates.
- Impact of Tillage: Repeated tillage reduces aggregate stability, making the structure more reliant on clay content and biological activity.
- Earthworms:
- Effect: Earthworms mix plant remains into the soil and produce casts that act as adhesives between soil particles, enhancing aggregate stability.
- Impact: They stimulate microorganisms, which further improve soil stability through mucus production.
- Plants:
- Effect: Plant roots dry out the soil by absorbing water, causing clay particles to come closer together, thus strengthening aggregates.
- Additional Impact: Plant roots add organic material to the soil and leave root channels, improving overall soil structure.
- Drainage:
- Effect: Proper drainage removes excess water from the soil, aiding in drying and improving soil structure.
- Benefit: Uniform drying and reduced compaction enhance crop establishment and soil aeration.
- Organic Material and Lime:
- Effect: Addition of organic material (e.g., manure, intercrops, residues) increases biological activity and microbial growth, improving aggregate stability.
- Long-Term Impact: Organic material builds up over time, enhancing soil structure. Regular lime additions improve soil pH and aggregate formation.
- Heavy Machinery:
- Effect: Machinery passes on arable soils can cause soil compaction, reducing large pore spaces, which restricts water and air movement and hinders root growth.
- Impact: Compaction leads to poor drainage and impedes root penetration.