Makroaggregate

Makroaggregate, in soil science, refers to a soil aggregate large enough to be discerned as a distinct clod or clump, typically defined as greater than about 0.25 millimeters in diameter. It is a component of soil structure that contrasts with microaggregates, which are smaller and more finely textured. Makroaggregates play a central role in organizing pore space and protecting organic matter within the soil.

Formation and characteristics occur through a combination of biological and physicochemical processes. Plant roots, fungal networks (including arbuscular mycorrhizal fungi), microbial exudates, and soil fauna contribute to the binding and stabilization of larger aggregates. Cementing agents such as root mucilage, polysaccharides, and the soil‐gluing protein glomalin help bind mineral particles into stable macroaggregates. Environmental factors, including moisture, temperature, organic matter inputs, and tillage practices, influence their formation, stability, and turnover.

Measurement of macroaggregates is typically done by separating soil samples based on size, often through wet-sieving or dry-sieving methods, with the >0.25 mm fraction commonly used as the operational definition. The proportion of macroaggregates within a soil sample provides an indicator of soil structure quality, aggregation dynamics, and erosion resistance.

Significance lies in the roles macroaggregates play in improving soil porosity, infiltration, aeration, and water storage. They help protect incorporated organic matter from rapid mineralization, contributing to soil carbon sequestration and nutrient cycling. Management practices that promote root growth and microbial activity, such as reduced tillage and organic matter additions, tend to enhance macroaggregate formation and persistence. The term Makroaggregate is widely used in German-language soil literature and is generally synonymous with the English concept of macroaggregate.

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