1. The document discusses salt-affected soils found in arid and semi-arid regions characterized by low precipitation and high evaporation. These soils can become saline, sodic, or saline-sodic. 2. Saline soils contain appreciable amounts of soluble salts like chlorides and sulfates which do not affect the soil structure. Sodic soils contain exchangeable sodium which disperses clay and degrades the soil structure. Saline-sodic soils have high salinity and sodicity. 3. Reclamation of saline soils involves leaching salts below the root zone. Reclamation of sodic soils requires adding amendments like gypsum to replace exchangeable sodium with calcium and restore soil structure

1. The ‘SALT AFFECTED SOILS” generally found
in Arid and Semi-Arid regions.
 These soils are generally found in “low
precipitation area” where precipitation and
evaporation ratio is less than 10.75.
 Weathering of parent rock also contribute to the
soluble salts to soil.
Saline soils lose their productivity and possibility
of turning them into unproductive once.

2.  Crop varieties differ in their response to various
biotic and abiotic stresses.
 Excessive salt concentrations decrease water
potential and thus result in reduced water
availability to the plant. Under such situations
plants often show wilting due to physiological
drought.
 Poor germination, seedling emergence and
establishments under saline conditions lead to poor
crop productivity.

3. Parameter EC (dS/m) pH ESP (%)
Saline Soil >4 <8.5 <15
Alkali Soil <4 >8.5 >15
Saline-
Alkali
>4 >8.5- 10.0 >15

4. Saline soils/white alkali/solonchak: Soils with high
amount of soluble salts having EC > 4.0 dsm-1 and
white crustations are seen on the surface. Hence it is
called as white alkali. Mostly these soils are dominant
with chloride and sulphate. Saline soils are formed
through a soil forming process called salinization in
semi arid and arid zones.

5. Alkali/Black alkali/ solonetz : These soils have EC <
4.0, PH> 8.5 to 10 and ESP > 15 and with precipitated
CaCO3. Dispersed clay with decomposed organic
mater (humus) give black Colour to these soils and
hence these soils are called as black alkali / solonetz
(Russian term) common salt is Na2CO3 NaHCO3

6. Saline-alkali soils: When soluble sodium salts
accumulate in a soil over a prolong period, form
sodium clay (sodium becomes the predominant cation
in soil solution). If the soluble salts (sodium) are not
leached out due to the insufficiency of rain, they
remain in the soil. They are thus, developed as a result
of the combined process of salinization and
alkalization. Sodium salts keep soils in flocculated
conditions. These soils have EC > 4.0, PH> 8.5 to 10
and ESP > 15 %

7. Degraded sodic / degraded alkali / solodi soils: These
soils have exchangeable sodium percentage > 15. But
the pH of surface horizon acidic in nature and there is
no precipitate CaCO3. However, the sub surface
horizon may have pH>8.5. In the assume of CaCO3 and
soluble salts the sodic clay with water degrades and
Hydrogen clay is formed in the surface. This process is
known as solodization, and the soil is called as solodi
in Russian terminology.

8. There are four major tracts where salt affected soils
are commonly met within India. These are
(i) The Semi-arid Indo-Gangetic alluvial tracts
(mainly in Punjab, Haryana, Uttar Pradesh and a part
of Bihar)
(ii) The arid tracts of Rajasthan and Gujarat.
(iii)The arid and semi arid tracts of southern states,
particularly of the irrigated rigor (Vertisol) soils.
(iv) The coastal alluvium

11. 1. Saline soil
A. Chemical Characteristics:-
 Dominated by neutral soluble salts consisting of
chlorides and sulphates of sodium, calcium and
magnesium.
 pH of saturated soil paste is less than 8.5
 An electrical conductivity of the saturated soil
extract of more than 4 dS/m at 25 °C is the
generally accepted limit above which soils are
classed as ‘saline’.

12.  There is generally no well-defined relationship
between pH of the saturated soil paste and
exchangeable sodium percentage (ESP) of the soil
or the sodium adsorption ratio (SAR) of the
saturation extract.
 Although Na is generally the dominant soluble
cation, the soil solution also contains appreciable
quantities of divalent cations, e.g. Ca and Mg.

13. B. Physical Characteristics
 In the presence of excess neutral soluble salts the
clay fraction is flocculated and the soils have a
stable structure.
 Permeability of soils to water and air and other
physical characteristics are generally comparable
to normal soils.

14. C. Biological Characteristics
Increase in salinity has shown a decrease in soil
respiration rate and soil microbial biomass.
The reason for the reduced size and activity of
the microbial community with increasing salinity is
likely to be osmotic stress which is caused by large
concentrations of salts in soil solutions (Oren,
1999).

15. D. Colour- Usually white
E. Effect on plant growth
 Through the effect of excess salts on the
osmotic pressure of soil solution resulting in
reduced availability of water.
 Through toxicity of specific ions, e.g. Na, Cl,
B, etc.

16. 2. Sodic Soil (Black-alkali soil)
A. Chemical Characteristics
Appreciable quantities of neutral soluble salts
generally absent. Measurable to appreciable
quantities of salts capable of alkaline hydrolysis, e.g.
Na2CO3 present.
Sodium is the dominant soluble cation.

17. B. Physical Characteristics
 Excess exchangeable sodium and high pH
result in the dispersion of clay and the soils
have an unstable structure.
 Permeability of soils to water and air is
restricted. Physical properties of the soils
become worse with increasing levels of
exchangeable sodium/pH.

18. C. Biological Characteristics
The reduction in soil micro-organism (especially
aerobic) as increase in pH and Na ion in soil. The
bio mass of fungi is reported very low in alkaline
soil. The no. of bacteria also reduce at high ph of
the soil.
D. Colour- Usually black (O.M dissolves at high
pH appearing black colour)

19. E. Effect on plant growth:- In sodic soils plant
growth is adversely affected :
Through the dispersive effect of excess
exchangeable sodium resulting in poor physical
properties.
Through the effect of high soil pH on nutritional
imbalances including a deficiency of calcium;
Through toxicity of specific ions, e.g. Na, CO3,
Mo, etc.

20. 3. Saline-Sodic Soil
a) Physico-Chemical Characteristics
 EC of the saturation extract is higher than 4 dsm-1
 pH of the soil is usually between 8.5 -10
 ESP is higher than 15 (>15)
b) Physical Characteristics
 Infiltration rate – good
 Soil Aeration - good
c) Colour- Usually white

21. 1. Parent material
2. Low rainfall
3. High Evaporation
4. Poor drainage
5. Poor quality irrigation waters
6. High water table
7. Sea water intrusion
8. Base forming fertilizers

22. 1. Parent material
Soils formed from rocks having high proportion of
bases are become salinc / sodic in nature.
E.g.: Basalt, Sand stone.
2. Low rainfall
One of the important reason for the development of
saline-sodic soils. Insufficient water to remove bases
from soil horizon leach to accumulation of salts in
soil. This is more common in semi arid and arid
regions where the rainfall is usually low.
3. High Evaporation
High evaporation is a common feature in semi arid and
arid regions. Because of high evaporation more
capillary movement of water from sub surface to

23. surface. on teaching the surface water along
evaporates to atmosphere leaving the salt to
accumulate in the surface of soils.
4. Poor drainage
Water logged salinity / sodicity is a common seen in
low lying area of islands particularly in high clay soils.
Improper drainage leads to accumulation of salts at
surface horizon and becomes reason for entry of
sodium in clay complex.
5. Poor quality irrigation waters
Continuous use of poor quality saline / sodic water for
cultivation accumulates salts / sodium in the soils

24. 6. High water table
High water table at alluvial plains and other areas
leads to improper drainage which leads to
accumulation of salts in soils.
7. Sea water intrusion
In coastal regions sea water intrudes into land and
pollutes the soil as well as ground water of that
locality.
8. Base forming fertilizers
Continuous application of base forming fertilizers for
cultivation is also causes soil salinity / sodicity. Eg.
NaNO3

25. Saline soils in which the soluble salts contain
appreciable amounts of calcium and magnesium do
not develop into alkali soils by the action of leaching
water. The reclamation is comparatively easy in such
soils. The main problem is to leach the salts
downward below the root zone and out of contact
with subsequent irrigation water.

26. Following methods may be used for removal of salts:
(A) Mechanical Methods:
(i) Flooding and leaching down of the soluble salts:
The leaching can be done by first ponding the water on the land and
lowering it to stand there for a week. Most of the soluble salts would
leach down below the root zone. After a week, standing water
(dissolved with soluble salts) is allowed to escape. Such, 2 to 3
treatments are given to reclaim highly saline soils. Sometimes
gypsum is also added to flood water when the soluble salts are low in
calcium to check development of alkalinity.

27. (ii) Scrapping of the surface soil:
When the soluble salts accumulate on the soil surface,
scrapping helps to remove salts. This is a temporary
cure and salinity again develops on such lands.
(B) Cultural Methods (Crop, Soil and Water Management):
(i) Providing proper drainage:
(ii) Use of salt free irrigation water:
(iii) Proper use of irrigation water:

28. (iv) Planting or sowing of seeds in the furrow:
(v) Use of Acidic Fertilizer:
(vi) Use of organic manures:
(vii) Ploughing and leveling of the land:
(viii) Retardation of water evaporation from
soil surface:
(ix) Growing of salt tolerant crops:

29. (i) Providing proper drainage:
If the soil is not free draining, artificial, drains are
opened or tile drains laid underground to help wash
out the salts.
(ii) Use of salt free irrigation water:
Salt free good quality of irrigation water should be
used.
(iii) Proper use of irrigation water:
It is known that as the amount of water in the soil
decreases the concentration of salts in the soil solution
increases, thus, moisture should be kept at optimum
field capacity.

30. (iv) Planting or sowing of seeds in the furrow:
They escape the zone of maximum salt concentrations
and thus, can germinate and develop properly during
their early growth stage.
(v) Use of Acidic Fertilizer:
In saline soil, acidic nature of fertilizers (e.g.,
Ammonium sulphate) should be used.
(vi) Use of organic manures:
When sufficient amount of these manures are added
the water-holding capacity of soil increases and as a
result the conductivity of the soil solution decreases.

31. (vii) Ploughing and leveling of the land:
Ploughing and leveling of the land increases the
infiltration and percolation rate. Therefore, salts leach
down to the lower levels.
(viii) Retardation of water evaporation from soil
surface:
Water may be conserved in the soil retarding the
water evaporation. Thus, salts may remain in the
lower level with the water.

32. ix) Growing of salt tolerant crops:
(a) High salt tolerant crops: Para grass, barley (BL-
2,RS-17, RS-6), sugar beet, etc.
(b) Moderately salt tolerant crops: Wheat ( Raj-
3077, KRL 1-4,Raj2917), rice, sorghum, maize, flax
etc.
(c) Low salt tolerant crops: Beans, radish, white
clover etc.
(d) Sensitive crops: Tomato, potato, onion, carrot etc.

33. II. Reclamation and Management of Alkali (Saline-
alkali and non-saline-alkali) Soils:
Alkali soils cannot be reclaimed by flooding the
land. In the case of saline-alkali soils, flooding is
likely to do more harm. Leaching (flooding) down of
soluble salts make the soil alkaline (only Na-clay
remain in the soil). Soils get dispersed and become
compact (impervious).
In alkali (non-saline-alkali) soils, exchangeable
sodium Na-clay is so great as to make the soil almost
impervious to water. But even if water could move
downward freely in alkali soils, the water alone would
not leach out the excess exchangeable sodium. The

34. 1. Gypsum (CaSO4 .2H2O)
2. Sulphur
3. Organic matter
4. Sulphuric acid
5. Iron pyrite (FeS2)
6. Iron sulphate(FeSO4)
7. Lime sulphur (CaS5)

35. This aims at removal of sodium from exchange
complex by introducing calcium.The amendments
suitable for different soil conditions are indicate
below :
Amendments Soil condition
Gypsum soil having pH range 9
Sulphur
Iron sulphate soil having pH range 8-9
Iron pyrite
Limestone soil having pH range up to <8

36. By cationic exchange, calcium is often used to replace
sodium in alkali soil. If the soil has no reserve of
calcium carbonate, the addition of gypsum (calcium
sulphate) is necessary. When gypsum is used as a
reclaiming agent, calcium replaces the exchangeable
sodium and converts the clay back into calcium-clay
(Ca-clay).Gypsum reacts with both Na2CO3 and
sodium as follows

37. For reasonable crop production on a sodic soil, the
lowering of the ESP to the level of 10 is considered
sufficient. The amount of gypsum required to be added
to a sodic soil to lower the ESP to a desired value is
known as gypsum requirement. It is expressed in
milliequivalent of Ca++ per 100 gm. of soil. Gypsum
requirement can be calculated from the data on CEC
and ESP of the soil.
Gypsum requirement (GR) i.e. me of Ca2+/100 g soil
= ESP (initial)-ESP (final) * CEC/100

38. When sulphur is spread on the soil, it is oxidised to
sulphuric acid, which converts sodium carbonate into
sodium sulphate. If calcium carbonate is not present in
the soil, it should be added artificially when sulphur is
used for reclamation.
Reactions are as follows:

39. The addition of organic matter increases acidity, thus,
helping in lowering the pH. Organic matter is especially
helpful where sulphur is added to correct the alkalinity.
The organic matter supplies food for the bacteria that
stimulates the oxidation of sulphur to the sulphate form.
The combination of sulphur, organic matter and gypsum
has also been used with success.

40. Sulphuric acid changes the sodium carbonate to
the less harmful sulphate and also tends to
reduce the intense alkalinity. It should be used in
the presence of calcium carbonate and use only
small area because its costly..

41. • Pyrite is a mineral containing iron and sulphur and
generally it has a chemical composition of FeS2.
Pyrite is found all over the world in igneous and
metamorphic rocks and at some places as
sedimentary deposits as well.
• Pyrite is pyrophoric in nature, produces sulphuric
acid and iron sulphate on coming in contact with air
and water. The sulphuric acid so produced reacts
with the native CaCO3of these soils to produce
soluble calcium which then replaces sodium from
the exchange complex.

42. Pyrite application in non-calcareous alkali soil is
not affective because they lack free CaCO3 to be
dissolved by H2SO4 to produce Ca needed for the
replacement of Na from exchangeable complex of
sodic soils.
Pyrite should not be applied in the rainy season
or in Paddy field. The activity of microorganism
(Thiobacilli) decreases at very low at anaerobic (water
logged) condition. The activity of microorganism is
high in moist soil with good aeration and moderate
temperature.

43. 2 FeS2 + 2 H2O + 7 O2 2 FeSO4 + 2 H2SO4
H2SO4 + Na[Clay H[Clay + Na2SO4
(leachable)
When Iron sulphate is applied to salt affected soils the
following reaction takes place
FeSO4 + H2O H2SO4 + FeO
H2SO4 + Na[Clay H[Clay + Na2SO4 (leachable)

44. When Lime sulphur is applied to salt affected soils the
following reaction takes place
CaS5 + 8O2 +4H2O CaSO4 + H2SO4
H2SO4 + CaCO3 CaSO4 + CO2 +H2O
CaSO4 + Na[Clay Ca[Clay + Na2SO4 (leachable)