Formation of soil aggregates via clay flocculation with organic polyelectrolytes

Soil organic matter (SOM) plays a leading role in the formation of the soil structure. However, the mechanisms of that formation are still debatable. We proposed that the combined action of two types of SOM - labile polyelectrolytes released by soil biota (flocculant) and highly transformed polyelectrolytes - humic substances (modifiers of soil mineral particles) has a synergetic effect and may be a key process that leads to the aggregation of mineral particles in soils. Humic substances adsorbing on mineral surfaces play a role of anchors that link clay particles with a flocculant and facilitate the aggregation. Different mechanisms of SOM interaction with minerals are considered. Our hypothesis was confirmed by rheological studies of model clay and sand systems with/without addition of humic acids and chitosan (flocculant). Comparison of model systems with real soils indicated the role of OM as well as other factors (clay content, humidity) in the soil aggregates formation.