In soil gaseous,liquid and solid phases are included with these phases living organisms are also included that can also be referred as microorganisms.
In soil both organic and inorganic components include.Inorganic components range in size from tiny colloids of 2um to large granules of >2mm size.
Many soil minerals are also included,sand and silt fractions have mostly primary minerals and clay have large amount of secondary minerals.The activity of soil minerals depends upon their size.The larger the size the faster the chemical activity or vice versa.95 to 100% by volume soil consist on soil minerals Organic compounds present in soil are less in amount than inorganic materials .But they can change soil properties . humus is the highly decomposed state of organic material.
Colloidal particles are considered as the basic sites in soil where whole physical,chemicle and biological properties depend and lie.due to this reason we can not complete our knowledge about soil without the comprehension of these whole small particles.
These are some properties of colloids
1 Extremely small can not be seen with human eye size is<1um.
2 there surface area is large we can comprehend it by this that there surface area is 1000times than same mass of coarse sans.
3 They have both externally and internally –ve or +ve charges.
4 cations,anions,hyderated ions and molecules adsorbed on the surface of colloids.
Now this is importance of soil colloids
Colloids are called the heart of the surface activity of soil and exchange complex.Colloids aid soil texturally and structurally. Thus helps plants through water rfetention.They release and retain plant nutrients.they prove helpful in controlling pollution.They are important inmanagement of soil and engineering work.