Soil Aggregates

What are soil aggregates?

Soil aggregates are the basic structural unit of soil. These structures include the soil particles (sand, silt and clay) and humus found in the soil. The soil particles bind to each other more strongly than to adjacent particles. The space between the aggregates provides pore space for retention and exchange of air and water. Aggregates stabilize the soil and maintain productivity while preventing erosion and deterioration.

What is aggregate stability?

Aggregate stability refers to the ability of soil aggregates to resist disruption when outside forces (usually associated with water) are applied. Aggregate stability is not the same as dry aggregate stability, which is used for wind erosion prediction. The latter term is a size evaluation.

Why is aggregate stability important?

Aggregation affects erosion, movement of water, and plant root growth. Desirable aggregates are stable against rainfall and water movement. Aggregates that break down in water or fall apart when struck by raindrops release individual soil particles that can seal the soil surface and clog pores. This breakdown creates crusts that close pores and other pathways for water and air entry into a soil and also restrict emergence of seedlings from a soil. Optimum conditions have a large range in pore size distribution. This includes large pores between the aggregates and smaller pores within the aggregates. The pore space between aggregates is essential for water and air entry and exchange. This pore space provides zones of weakness low bulk density or large pore spaces, aggregation is less important. For example, sandy soils have low aggregation, but roots and water can move readily.

What are soil aggregates? Soil aggregates are the basic structural unit of soil. These structures include the soil particles (sand, silt and clay) and humus found in the soil. The soil particles bind to each other more strongly than to adjacent particles. The space between the aggregates provides pore space for retention and exchange of air and water. Aggregates stabilize the soil and maintain productivity while preventing erosion and deterioration. What is aggregate stability? Aggregate stability refers to the ability of soil aggregates to resist disruption when outside forces (usually associated with water) are applied. Aggregate stability is not the same as dry aggregate stability, which is used for wind erosion prediction. The latter term is a size evaluation. Why is aggregate stability important? Aggregation affects erosion, movement of water, and plant root growth. Desirable aggregates are stable against rainfall and water movement. Aggregates that break down in water or fall apart when struck by raindrops release individual soil particles that can seal the soil surface and clog pores. This breakdown creates crusts that close pores and other pathways for water and air entry into a soil and also restrict emergence of seedlings from a soil. Optimum conditions have a large range in pore size distribution. This includes large pores between the aggregates and smaller pores within the aggregates. The pore space between aggregates is essential for water and air entry and exchange. This pore space provides zones of weakness low bulk density or large pore spaces, aggregation is less important. For example, sandy soils have low aggregation, but roots and water can move readily.
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