Mikroaggregater

Mikroaggregater, or microaggregates, are small soil aggregates generally smaller than about 0.25 millimeters in diameter. They form part of the soil’s structural hierarchy and contribute to the stabilization of organic matter, nutrient cycling, and overall soil function.

These microaggregates arise through physical, chemical, and biological processes. The binding of clay minerals and mineral particles by organic matter, microbial exudates, and polysaccharides such as glomalin produces stable aggregates. Microbial activity, root exudates, and plant roots also contribute to their formation and persistence.

Microaggregates play a central role in soil function. They protect organic carbon from rapid mineralization, influence water holding capacity and porosity, and enhance resistance to erosion. Because they reflect long-term inputs and soil biological activity, their abundance and stability are used as indicators of soil health and management history.

Measurement and study of microaggregates usually involve separating aggregates by size and stability. Wet sieving distinguishes microaggregates from macroaggregates, and density fractionation or imaging techniques can be applied for further analysis. Hydration stability tests assess how microaggregates resist dispersion in water.

Management practices influence microaggregates. Reduced tillage, cover crops, and added organic matter tend to promote their formation and stability, while intensive tillage and bare fallow can disrupt them. Microaggregates are widely used in soil carbon models and assessments of soil quality, reflecting both soil biology and long-term soil management.