What is Soil ? Formation of Soil

Soil is a nat­ur­al resource formed by wheather­ing (break­down) of rocks. It has been defined as they matrix (sand slit clay) con­tain­ing liv­ing bio­mass and dead organ­ic mat­ter with some con­cen­tra­tion of air and water. 

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It is a rich source of organ­ic and inor­gan­ic mate­r­i­al that sup­port plant life and micro­scop­ic com­mu­ni­ties. Inor­gan­ic mate­r­i­al include ele­ments derived from weath­er­ing and Frag­men­ta­tion of par­ent rock material. 

organ­ic com­po­nents include organ­ic wastes, dead remi­ans of plant and ani­mals and their decom­po­si­tion products. 

For­ma­tion of soil

The for­ma­tion of soil for­ma­tion begins with the changes in the par­ent mate­r­i­al (rocks)

Accu­mu­la­tion of raw mate­r­i­al fol­lowed by build up of organ­ic mate­r­i­al at the surface.. 

Var­i­ous phys­i­cal ‚chem­i­cal, bio­log­i­cal and anthro­pogenic process are invlovwd in the alter­ation of the par­ent mate­r­i­al to form soil. 

Two main steps invoved in soil for­ma­tion include:

1. Weath­er­ing of rocks : 
2. The break­down of rocks is called weathering.it cna be phys­i­cal and chem­i­cal. Phys­i­cal weath­er­ing occurs by mechan­i­cal forces. Changes in tem­per­a­ture cause con­trac­tion or expan­sion of rocks lead­ing to for­ma­tion of cracks and fis­sures in rocks. 
3. This breaks rocks into sam­ller pieces. Low tem­per­a­ture freezes the water present in the rock crevices caus­ing expan­sion and this force breaks into small pieces besides these, hail, rain­fall, wind also help in break­ing of rocks into small­er par­ti­cles due to fraction. 

Chem­i­cal weathering :

It is brought about by action of water or activ­i­ties of organ­isms present in soil. Water brings chem­i­cal changes in rocks due to dis­so­lu­tion. Oxi­da­tion reduc­tion and organ­ic acids pro­duced by microbes assist in the break­down of rocks and add organ­ic mat­ter to soil. 

2. Min­er­al­iza­tion and Humification:

The small pieces of rocks or par­ti­cles prod­ced by weath­er­ing of rocks get con­vert­ed into a homoge­nous matrix via the process of min­er­l­iza­tion. Plants and ani­mals play an impor­tant role in this process 

The roots of the plants invade the soil par­ti­cles fur­ther break­ing the par­ti­cle into fine mate­ri­als. The microbes asso­ci­at­ed with the roots of plants secrete organ­ic acids and humic acids that fur­ther assist in break­down of rock mate­r­i­al to fine soil particles. 

Microor­gan­isms such as bac­te­ria, fun­gi and actin­o­mycetes assists in the decom­p­is­tion process. 

In the process, organ­ic com­pounds get con­vert­ed into inor­gan­ic nutri­ents. The break­down of organ­ic com­pounds leads to for­ma­tion of sim­ple prod­ucts such as car­bon diox­ide, water and Minerals.this process is called Min­er­l­iza­tion forms the humus which is dark, homoge­nous, amor­phous, col­lo­di­al substances. 

Humus gives lose tex­ture to the soil which pro­vides aer­a­tion and helps in rea­tin­ing water and nutrients. 

Fac­tors affect­ing soil for­ma­tion include :

1. Par­ent material
2. Cimate
3. Topog­ra­phy ( elevation) 
4. Bio­log­i­cal factors 
5. Time

SOIL : Types of Soil, Clas­si­fi­ca­tion of Soil, Soil Bio­ta and Fer­til­i­ty : Click Here