Soil Problems: their Reclamation and Management

 Soil Problems

There are generally three soil problems:
Soil salinity and sodicity
Soil erosion
Waterlogged soils

Soil Salinity and Sodicity

                Soils affected by salinity and sodicity are called salt-affected soils. These soils adversely affect the growth of most crop plants because of the presence of excess soluble salts or exchangeable sodium or both.
Salt-affected soils are generally divided into three classes i.e. saline, sodic and saline sodic.

1.      Saline Soil

                                A soil having sufficient amount of soluble salts but not excessive exchangeable sodium to adversely affect the growth of most crop plants is saline soil. Saline soils have:
Electrical conductivity of the saturated soil extracts ≥4 dSm1
Exchangeable sodium percentage < 15
pH of saturated soil paste < 8.5

2.      Sodic Soil

                         A soil having sufficient amount of exchangeable sodium but not excessive soluble salts to adversely affect the growth of most crop plants is sodic soil.  Sodic soils have:
Electrical conductivity of the saturated soil extracts ≤4 dSm1
Exchangeable sodium percentage ≥ 15
pH of saturated soil paste ≥ 8.5

3.      Saline-Sodic Soils

                                      A soil having both soluble salts as well as exchangeable sodium in sufficient amount to adversely affect the growth of most crop plants is saline sodic soil. Saline sodic soils have:
Electrical conductivity of the saturated soil extracts ≥4 dSm1
Exchangeable sodium percentage ≥ 15
pH of saturated soil paste ≥ 8.5
In some literature, the term “alkali” is used in place of “sodic” i.e. for soils having excess exchangeable sodium. Hence the term “saline-alkali” in place of “saline-sodic” is used. However, the use of the term “alkali” is being discouraged because of its ambiguity with the term “alkaline” which refers to the soils having pH> 7.0

Reclamation and Management of Salt affected Soils

Reclamation is the process of removal of excessive soluble salts and/or exchangeable sodium from the soil.
An amendment is a material which is added to the soil to make it more suitable for plant growth e.g. gypsum, sulphuric acid etc.
Pre- requisites of soil reclamation
Good internal soil drainage
Land levelling
Availability of sufficient amount of good quality water
Deep ground water
From reclamation point of view, the salt- affected soils are divided into two categories i.e. saline and saline-sodic.

Reclamation of Saline Soils

                                          The reclamation of saline soils is relatively easy to achieve if large amounts of good quality irrigation water is available and surface as well as internal drainage are possible. Embankments are made around the saline field and the field is flooded with water. While moving downward, this water removes the soluble salts out of the root zone and rending the soil fit for crop growth.

Reclamation of Saline-Sodic Soils

                                                                For reclaiming sodic and saline-sodic soils some amendments supplying soluble calcium in the soil either directly (gypsum) or indirectly (sulphuric acid in calcareous soils) are required. After applying amendments heavy irrigation is required to leach the replaced sodium from the soil’s exchange complex and soluble salts out of the root zone.
Saline sodic soil should not be leached without any amendment otherwise these soils will be converted into sodic soils after the leaching of soluble salts. Sodic soils are more difficult to reclaim than the saline-sodic soils.

Management of Salt affected Soils

If it is not possible or practicable to remove all the salts and/or exchangeable sodium from soil due to high cost or shortage of good quality water these soils may still be used profitably with proper management. In such situation, either some salt tolerant plants can be grown or salt damage to help plants can be minimized by controlling water and following suitable techniques of planting e.g. planting on raised beds.

Soil Erosion

                           The detachment and movement of soil surface by running water, ice, wind, gravity or other geological agents is called soil erosion.

Waterlogging/ Water logged Soil

                                                                               Soils saturated with water (due to high or perched water table) for a sufficiently long time annually which is detrimental to most of the field crops are called waterlogged soils. Waterlogging causes oxygen deficiency for plant roots, ultimately leading to death of sensitive crops.
Perched water table means the water table of a saturated layer of soil which is separated from an underlying saturated layer by an unsaturated layer.

















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