How soil structure develops How do aggregates form?
Several biological, physical, and chemical processes interact to form aggregates and then stabilize them. Microbes decomposing organic matter create compounds that cement soil particles together. Synthetic polymers (“soil conditioners”) and sugars excreted from roots can have a similar cementing effect. Humus – the stable organic compounds – also binds soil particles together. Fungal hyphae and fine roots surround and stablize aggregates. This is why surface residue and other organic matter improve soil structure – the residue is food for fungi and bacteria that in turn help form and stabilize soil aggregates. Larger organisms (such as insects and earthworms), enhance soil structure when they burrow through the soil and deposit fecal pellets that become stable soil aggregates. Physical and chemical processes are also important to the formation of soil aggregates – especially smaller aggregates. Particles are physically pushed closer together by freezing and thawing, wetting and drying,
