Essay on the Classification and Genesis of Soil

Modern Classification:

1. Red soil

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a. Red loam

b. Red sandy soil (Fe++)

2. Laterite soil

a. Low level (leaching)

b. High level

3. Black soil

a. Shallow black

b. Medium black

c. Deep black soil

4. Alluvial soil

a. Coastal alluvium

b. Coastal sand

c. Deltaic alluvium

5. Desert soil

6. Tarai soil

7. Hill soil (brown)

8. Saline and Alkali soil

9. Peaty soils

1. Red Soil:

Tamil Nadu, a part of A.P, M.P, Orissa, Bihar, U.P., W.B., Rajasthan

a. Fe⁺⁺

b. Porosity is high

c. Leaching (principle)

d. Less in N₂ and P₂0₅

(a) Red loam

a. Derivative form weathering of granites,gneiss

b. Rich in clay mineral and poorer in silicon

c. Texture of the soils loam to silt and clayloam

d. PH is neutral but slightly acidic.

(b) Red sandy soil

a. Derived from granites, gneiss quartzite and sandstone

b. Colour red hematite or yellow

c. CEC 5 to 20 mg

d. pH acidic (4.5 – 6.5)

2. Laterite Soil:

Maharashtra, Kerala, M.P, Orissa and U.P etc

i. They exhibit plasticity, cohesion, shrinkage and expansion.

ii. CEC 2 to 4 mg/l00g of soil, poor water retention High organic matter poor in lime and Mg, deficient in P and K.

p^H 5-6.

3. Black Soil:

Maharashtra, Gujarat, M.P, Rajasthan, U.P, A. P., Tamil Nadu, Karnataka

i. Clay % of 40 – 60 %

ii. Clay – montmorlionite.

iii. PH – 7.5 to 8.5

Shallow black soil: (depth – 30 cm)

i. Texture – silt loam to clay lime is usually present in fine grains

ii. Dark brown to dark yellow

iii. Structure is granular, blocky Medium black soil: (30 to 100cm)

iv. Basaltic traps, Dharwar, Schists, basic granite, gneisses, hornblend.

v. Moderately rich in organic matter and well drained

vi. Gypsum is available in upper surface.

Deep black soil:

i. Derived from basalt

ii. % of clay – 40 to 60 %

iii. Lime is present in irregular nodules

iv. Alkaline

v. Clay minerals

4. Alluvial soil (T ↑ k ↓N α P₂O₅):

Rajasthan, U.P., Bihar, W.B., Gujarat, Assam, Orissa

Mainly formed deposition of silt over ages,

i. High K less in N and P₂O₅

(a) Coastal alluvium:

i. Structure – sand and silt, deep reddish brown to yellowish brown grey

ii. Derived from calcareous materials

iii. It is mainly for agriculture

(b) Coastal sands:

i. Lack of profile development.

ii. Salinity is high.

(c) Delatic Alluvium:

i. It is formed by river deposition.

Soil Process and Formation:

Soil Formation is a process of two distinct phases.

I. Weathering of Rocks and Minerals (Destructive Process)

II. Development of True Soil (Constructive Process)

I. Weathering:

Process & transformation of solid rocks into soil

Five Stage of Soil Development: