Fundamentals of Soil Science (1+1)

Dealkalization

Dealkalization (Solodization):

• The process refers to the removal of Na⁺ from the exchange sites. This process involves dispersion of clay. Dispersion occurs when Na⁺ ions become hydrated.
• The process is effected by intensive leaching and degradation which takes place in older soils.

Calcification

• The process operates in arid and semi-arid regions and refers to precipitation and accumulation of calcium carbonate (CaCO₃) in some part of the profile. The accumulation of CaCO₃ may result in the development of a calcic horizon.
• Calcium is readily soluble in acidic soil water and/or when CO₂ concentration is high in root zone as:

CO₂ + H₂O = H₂CO₃
H₂CO₃ + Ca = Ca (HCO₃)₂ (soluble)
Ca (HCO₃)₂ = CaCO₃ + H₂O + CO₂ (precipitates)

Decalcification

• In regions where some water percolates through the soil profile , decalcification takes place leading to the formation of calcic horizon down below.
• In humid regions, calcium cabonate reacts with water containing dissolved carbon dioxide to form soluble bicarbonate which may be completely leached out of the soil profile.

 

CaCO₃ + CO₂ + H₂O (insoluble) = Ca(HCO₃)₂ (soluble)

Carbonation

• It occurs when carbon dioxide interacts chemically with minerals. When carbon dioxide is dissolved in water, it forms weak carbonic acid.
• When carbonic acid comes in contact with the surface of the earth it dissolves large masses of limestone, creating caves and caverns.

Gleization:

• The term glei is of Russian origin means blue, grey or green clay.
• The gleization is a process of reduction, due to anaerobic condition, of iron in waterlogged soils with the formation of mottles and concretions. Such soils are called as hydromorphic soils.
• The process is not dependent on climate (high rainfall as in humid regions) but often on drainage conditions.

Pedoturbation:

• It is the process of mixing of the soil.

1. Faunal pedoturbation: It is the mixing of soil by animals such as ants, earthworms, moles, rodents, and man himself
2. Floral pedoturbation : It is the mixing of soil by plants as in tree tipping that forms pits and mounds
3. Argillic pedoturbation: It is the mixing of materials in the solum by the churning process caused by swell-shrink clays as observed in deep Black cotton soils.