Aggregate stability

Ability of soil to resist change in soil aggregate is known as aggregate stability or capacity of soil to resist in breakdown of soil aggregates in to individual particles is known as aggregate stability. These are major factors appear to influence aggregate stability.

• Temporary mechanical binding action of microorganism, especially the thread like filaments of fungi. These effects are pronounced when fresh organic matter is added to soil and are at a maximum of few weeks or months after application.
• Cementing action of the intermediate products of microbial synthesis and decay, such as microbially produced gums and certain polysaccharides.
• The cementing action of more resistance stable humus components aided by similar action of certain inorganic compounds such as iron oxides. There materials provide most of the long-term aggregate stability.

It should be emphasized that aggregate stability is not entirely an organic phenomenon. There is continual interaction between organic and inorganic components. Polyvalent inorganic cations that cause flocculation e.g. Ca2+, Mg2+, Fe2+ and Al2+ also are thought to provide mutual attraction between the organic matter and soil clays, encouraging the development of clay organic matter complexes. in addition, films of clay called “clay skin” often surround the soil peds and helps to provide stability. The noted stability of aggregates in red and yellow soil of tropical and subtropical areas is due to the hydrated oxide of iron they contain.