How does manure & other organic matter improve soil structure?

Question

How does manure & other organic matter improve soil structure? Based on my understanding, soil structure refers to the arrangement of the aggregates within the soil; a good soil structure prevents waterlogging, "nutrient-lockup" (and ultimately the death of the crops). However, I don't understand how manure can improve this structure to the benefit of the plants.

In my textbook, it has been—without any further explanation—written that:

Manure and other organic matter gives the soil a good structure and improves its water-holding properties. Conversely, artificial fertilizers do little to maintain a good soil structure because they contain no organic matter.

Googling led me to the following paragraph, but again, it hardly explains how:

Organic matter causes soil to clump and form soil aggregates (how though?), which improves soil structure. With better soil structure, permeability (infiltration of water through the soil) improves, in turn improving the soil's ability to take up and hold water.

[I have a couple of theories as to how this might be, but I'd rather ask here and not mess up]

Answer 1

Surface area

Organic material in soil is finely divided and provides a large surface area to mass ratio. Clay particles have a similarly large surface area, but most clays stick to each other because of their micro-structure and chemistry, making soils less permeable and prone to over-compaction.

Organic matter, regardless of its ultimate source, is the opposite. Its surface structure keeps the individual particles separated, and its chemistry actively encourages water to infiltrate between, and in fact through, its particles. Well rotted organic matter therefore creates a high reactive surface on which vital soil chemical reactions can take place and opens the structure of the soil column to greater water movement.

The surface area created by soil organic matter also hosts soil bacteria and fungi that help to bind soil particles together into larger aggregates, and facilitates semi-permanent chemical binding by creating zones of interaction between water with dissolved minerals and air in the soil.

Answer 2

Manure is natural fertilizer. Organic material has Carbon in it, also contains proteins, carbs, etc. All the stuff that break down and feed plants over time. Plants don't feed directly but micros and fungi do and break it down to water soluable nutrients.

As a structure organic matter retains water, clay and sand are largely wick away water. The organic material properly mixed also fights compaction.