1. The document discusses various types of problem soils including saline soils, saline-alkali soils, sodic soils, and their characteristics. 2. Saline soils contain excess neutral soluble salts like NaCl, CaCl2, MgCl2 which increase the osmotic pressure of the soil solution. Saline-alkali soils have both excess salts and alkalinity due to sodium. 3. Sodic soils have a high percentage of sodium ions that disperse clay particles and destroy the soil structure, reducing permeability and aeration. Reclamation methods include leaching salts, applying gypsum or other amendments, and growing salt-tolerant crops.

1. Lec.
No.
Topic Wieghtage
3-4 Origin and basic concept of problematic
soils
3
5 Factors responsible for the formation of
soils
4
6-7 Morphological features of saline, sodic
and saline sodic soils
4
8-9 Characterization of salt affected soils-
soluble salts, ESP, pH,
4

2. Types of soil degradation
Water
Erosion
Sheet
erosion
Rill erosion
Gully
erosion
Wind
Erosion
Chemical
Degradation
Acid soil
Saline
soil
Saline-
sodic soil
Sodic soil
Acid-
sulphate
soil
Coastal saline
soil
Physical
degradation
Water logging
(Submerged )
Surface ponding
Subsurface water
logging
Vegetation
degradation
Land sliding
Soil
fertility
decline
Other
degradation
Mining
Industria
l waste
appli
Snow
covered
area

3. Causes of
DegradationDeforestation
Overgrazing
Agricultural
Practices
Over-
exploitation of
vegetative cover
Industrial
activity
Land use
conversion
Soil
nutrient
mining
Inappropriate
irrigation

4. Physical processes
Structural
decline
Compaction-
Heavy
implements
Erosion:
Wind/water
High soil
temperature
Leaching
Chemical Processes
Nutrient
imbalance/
Fertility depletion
Salinization/
Calcareous soils
(Pri/Sec)
Sodicity
Acidification
Marshy lands
Submerged soils
Acid sulphate
soils
Land sliding
Biological Processes
Soil biodiversity
decrease
Decrease in OM
Intensive
cultivation
Soil Pollution
Deforestation
Forest fire
Factors and Processes of Soil Degradation

5. NEGATIVE POSITIVE
Soil erosion Conservation tillage
Nutrient runoff loss Crop rotation
Water logging Improved drainage
Desertification Residue management
Acidification Water conservation
Compaction Terracing
Crusting Contour farming
Organic matter loss Efficient nutrient use
Salinization Green manuring
Nutrient depletion by leaching Improved nutrient cycling
Toxicant acculmulation Soil climate
Calcareousness Mulching
Sodicity INM
Acid sulphate soils

6. Classification of problem soils based on properties
Physical characteristics
Eroded soils
Sloping lands
Ravine lands
Highly permeable coarse textured
soils
Crusting soils
Red chalka soils
Peat soils
Submerged soils/Marshy
land
Slowly permeable heavy
textured soils
Chemical
Characteristics
Acid soils
Acid sulphate soils
Calcareous soils
Salt affected soils

7. Classification – Problem Soils
Salt Affected Soil
Saline soils
Saline-sodic soils
Sodic soils
Other problem soils
Acid soils
Acid sulphate soils
Calcareous soils
Submerged soils

8. Saline Soils
The soils have neutral soluble salts hence saturation paste extract
pHe < 8.5.
These soils have neutral soluble salts of Na, Ca and Mg with chlorides
and sulphates hence electrical conductivity of saturation extract ECe
is generally more than 4 d Sm-1 at 250C.
Dominant salts are NaCl, CaCl, MgCl, or NaSO4, CaSO4, MgSO4.
The excess of neutral soluble salts that limits the normal plant growth.
Total soluble salts conce. > 0.1%
Soils remain flocculated condition
pH: Varies 7.5 to 8.5 ECe: > 4 dSm-1 ESP: < 15%
Total soluble salt content is > 0.1 %
White colour due to NaCl and Na2SO4
Brown colour saline soil is due to NaNO3
Characteristics of saline soils

9. Measurement of Salinity
Dissolved ions and
two metal plates
Voltage is applied & ions move
toward oppositely charged plates
Electrical Conductivity (EC) is an measure of the flow of electricity through
a material
Saline soils and salty water conduct more electricity than nonsaline soils or
pure water. It is the ions that pass or conduct electricity from one ion to
the next
As salt concentration increases, EC increases.
Acidic or low pH solutions also exhibit high EC
Expressed in dS/m (SI units) or mmhos/cm (old unit)
dS/m = mmhos/cm
Use an EC ‘bridge’ or meter to measure how well water extracted from soil
can conduct electricity

10. Deionized water: 0.0005 to 0.002 dS m-1
Seawater: 40 to 55 dS m-1
Poor quality irrigation water: > 3 dS m-1
Saturated Paste Extract EC of saline soils: ≥ 4 dS m-1
EC values for common waters (dS/m)

11. TDS – Total dissolved solids
– Cations + anions + anything <2 microns
– Good quality water has <500 mg/L or ppm TDS
– measure using gravimetry or EC
• Evaporate water off and accurately weigh the residue
• Problematic due to hydration and volatilization
– EC (dS/m) x 640 ≈ TDS (mg/L)
• TDS ‘meters’ are really EC meters with conversion factor
Measurement of Salinity – TDS

12. Charecteristcis of Saline Soils
1 Excess soluble salts like NaCl, CaCl, MgCl, or NaSO4, CaSO4, MgSO4.
2 Correspondence to Hilard’s (1906) white alkali soils due to white layer
of soluble salts over the surface
3 In Russian such soils are called “Solonchak,s”
4 Saline soils can be recognized by the presence of white salt crust on
the surface
5 If adequate drainage is available, excess soluble salts may be removed
by leaching and these soils can be normal
6 Saline soils can be determined by the kind and amount of salts
present.

13. Features of Saline Soils
7 Amount of soluble salts present controls the osmotic pressure of the
soil solution
8 Na seldom comprises more than half of the soluble cations and
hence is not adsorbed to any significant extent
9 Chief anions are chlorides, sulphates and sometimes nitrates and
some amount of bicarbonate may occur but carbonates are
invariably absent.
10 Generally deficient in P, Zn, Fe, N
11 Soils are aggregated and highly permeable
12 Soils are flocculated and hence drainage is good.

14. Saline soils

18. Alkali soils/sodic soils
Non-Saline Alkali
Soils
pH= 8.5 to 10
ECe = < 4.0 d Sm-1
ESP = >13%
TSS = < 1%
Saline-Alkali Soils
pH= >8.5
ECe = > 4.0 d Sm-
1
ESP = >15%
TSS = > 1%
Degraded Alkali
soils
pH= > 8.5
(Surface layer acidic)
ECe = < 4.0 d Sm-1
ESP = >15%
TSS = > 1%
Black colour
Prism like
structure
Compact

19. Features of Non-Saline Alkali / Sodic Soils
1 Hilard’s Black Alkali Soil and Russian term Solonetz
2 Occurs in Arid and Semiarid regions in small irregular areas
while are often termed as “slick spots”
3 Except when gypsum is present in the soil or irrigation water,
the drinage and leaching of saline-alkali soils leads to
formation of non-saline alkali soils
4 Removal of excess salts in such soils tends to increase in the
rate of hydrolysis of the exchangeable Na which causes rise in
pH.
Na + H2O= NaOH
5 Dispersed and dissolved OM present in the soil solution of
alkaline soils may be deposited on the soil surface by
evaporation thus causing darkening and giving rise to the term
“Black Alkali”

20. Features of Non-Saline Alkali / Sodic Soils
6 If allowed sufficient time, these soils develop characteristic
morphological feature…Because partially sodium saturated clay
is highly dispersed it may be transported downward through
the soil and accumulates at lower level…..this causes…..
7 Few inches of the surface soil may have relatively coarse texture
and friable; but below, where the clay accumulates, the soil
may develop dense layer of low permeability that have
COLUMNAR OR PRISMATIC structure, thereby difficult to till.
8 Exch. Na has marked effect on physical and chemical properties
of soil. As the proportion of Na increases- dispersion of soil
increases
9 At high pH reading and in the presence of carbonates ions, Ca
and Mg are precipitated; hence the soil solution of this non-
saline alkali soils usually contain only small amount of theses
cations.
10 Deficient in P/Ca/N/Fe/Zn

21. 1 ESP= >15% pHe = > 8.5 EC = > 4.0 dS-1
2 Formed due to salinization and alkalinization…. As long as excess
salts are present, the apperance and properties of theses soils are
generally similar to saline soils
3 If excess soluble salts are leached downward, the properties of
these soils then it shows similar features like non-saline alkali soils
4 As the concentration of salts in the soil solution is lowered, some
of the Exch.Na hydrolyses and forms NaOH.
Na + H2O = NaOH
5 This may change to NaCO3 upon reaction with CO2 absorbed from
the atmosphere..NaOH + CO2 = Na2CO3 (Strongly alkaline)
6 Na causes dispersion of clay and soil becomes unfavorable for
entry and movement of water and even for tillage
Features of Saline Alkali Soils

22. Formation of Saline-Alkali Soils-Reasons
1 Arid and semiarid region
2 Poor drainage
3 High water table
4 Overflow of sea water over land
5 Introduction of irrigation water
6 Salts blown by wind
7 Saline nature of parent rock material
8 Excessive use of basic fertilizers
9 Humid and semi humid region

23. 1) Arid and Semi-arid region
Annual rainfall is less-not
sufficient to leach down the
salts
Evaporation rate is low
Intensity of salinization…
increases with dryness of
climate
2) Poor drainage of soil
During high rainfall-salts are
leached fro upper layer to
lower layer if drainage is
impeded, they will
accumulate in lower layer
When water evaporates
again salts move towards
upward layer causes
secondary salinization

24. 3) High water table
Groundwater in arid-
semiarid region usually
contains considerable
amount of soluble salts
High water table causes
water to move upwards
towards surface by capillary
action causes secondary
salinization
4) Overflow of sea water
Low laying areas near sea
which gets sea water
during high tides thereby
accumulate the salts

25. 5) Introduction of irrigation
water
Clay soil, impeded drainage,
injudicious use of water,
monocropping, faulty
irrigation methods, excess
irrigation
Ground water is the arid
regions is saline in nature.
It has excess soluble salts
6) Salts blown by wind
In arid regions near the sea,
a lots of salts are blown by
wind year after year and
gets deposited on surface.
Due to low rainfall, they are
not washed/leached out
back to sea and added in
soil.Rajasthan

26. Effect of SALINE soil on Soil/Plant/Microbes
1 Neutral soluble salts of chlorides and sulphates are more
2 Excess soluble salts increases OP in soil than cell sap.
3 This prevents the absorption of moisture and nutrients.
4 Excess salts produces toxic effects
5 Specific ion toxicity
6 Germination & root growth affected
7 Secondary salinization affects root growth
8 Less microbial population & activity
9 Less nutrients availability/more dose
10 Deficiency of macro and micronutrients (P, Zn,Fe, Mn)
11 Ca and Mg decreases zeta potential causing reduction in
thickness of DDL-enhances flocculation
12 Soils are aggregated & highly permeable, drainage is good

29. Effect of SODIC soil on Soil/Plant/Microbes
1 Insoluble salts
2 Excess insoluble salts of Na enhances Na2CO3 enhances alkalinity
3 Na causes dispersion of clay and destroys soil structure
4 Na is monovalent adsorbs on clay and enhances the zeta potential
which enhances thickness of DDL
5 Sealing of macro & micro pores that reduces aeration
Reduced aeration cusses..
7 less microbial activity, permeability reduced microbial activity
reduced , gas exchange inhibits, compactness increases, impeded
drainage, stagnation of water, BD increases
8 Availability of P,Ca, N, Fe, Mn and Zn reduces
9 Germination, root growth, microbial activity & population
reduced
10 Root growth, tillering, flowering, fruiting, shelf life of fruits
reduced
.

30. Reclamation of Saline Soils
Mechanical Methods
Flooding and leaching
down of the soluble salts
Scrapping of the surface
soil
Cultural methods
1.Providing proper drainage
2. Use of salt free irrigation water
3. Judicious use of IW
4. Planting/sowing of seed in furrow
5. Use of acidic fertilizers
6. Use of organic manures
7. Ploughing & leveling of land
8. Mulching or retardation of evaporation
of water from soil surface
9. Growing of salt tolerant crops

31. Mechanical method
A combination of flooding after drain is most effective to leach
down the soluble salts which are neutral and high in Ca and Mg and
very little exch.Na.
Scarpping of salts
Leaching requirement (LR)
Defined as the fraction of irrigation water that must be leached
through root zone to control the salinity at any specified levels.
LR is a simply ratio of drainage water to the depth of irrigation
water.
LR = Ddw/Diw X 100
Where
LR = Leaching requirement
Ddw = Depth of drainage water
Diw = Depth of irrigation water
LR = ECiw/Ddw X 100
ECiw = EC of irrigation water
ECdw = Ec of drainage water

32. Example;
For irrigation water with Ex 1, 2, 3 dS m-1 the leaching
requirement will be 13, 25 and 28% respectively value of EC
Taking ECdw is 8 dSm-1
LR= 1/8 X 100 = 12.5%=13%
LR = 2/8X 100 = 25 %

33. Reclamation of Alkali Soils
Chemical Methods
1. Application of Gypsum
and gypsum requirement
2.Use of sulphur/Iron pyrite
3. Addition of sulphuric
acid
4.Additio of organic matter
5. Addition of molasses
Cultural methods/
Management practices
1. Water management and
cropping system are very
important
2. Growing of salt tolerant
crops and crop verities

34. Gypsum requirement:
Amount of gypsum required to be added to sodic soil to lower the
ESP to desired value is called
Expressed as meq Ca2+ per 100 g soil
According to Schoonover one equivalent of gypsum corresponds
to 1.72 t gypsum/acre foot of soil
GR depends on
Exchangeable Na content to be exchanged
Exchange efficiency
Depth of soil to be reclaimed
GR= ESP1 –ESP2/100 X ECE of soil
Where
ESP 1= Actual ESP of sodic soil
ESP2 = Desired ESP of soil
CEC= Cation Exchange capasity

35. Soil amendments
These are substances that influence the plant growth favorably by
producing in the soil one or more of the following beneficial effects.
• Changing the reaction ,that is making the soil less acidic or less
alkaline ;
• Changing the plant nutrients in the soil from unavailable to
available forms;
• Improving the physical conditions of the soil and
• Counteracting the effects of injurious substances
Soil amendments usually contain plant nutrients also .Agricultural liming
materials, for example, supply calcium and, sometimes magnesium as
nutrient el

36. Na2CO3 + CaSO4 = CaSO3 + Na2SO4 (leachable)
Gypsum
Gypsum is chemically CaSO4.2H2O and is a white mineral that occurs
extensively in natural deposits. It must be ground before it is applied
to the soil. Gypsum is soluble in water to the extent of about one-
fourth of 1 percent and is, therefore, a direct source of soluble
calcium. Gypsum reacts with both the Na2CO3, and the adsorbed
sodium as follows:
Calcium chloride
Calcium chloride is chemically CaCl2 2H2O. It is a highly soluble salt
which supplies soluble calcium directly. Its reactions in sodic soil are
similar to those of gypsum:
Na2CO3 + CaCl2= CaCO3 + 2 NaCl (leachable)

37. Sulphuric acid
Sulphuric acid is chemically H2SO4. It is an oily corrosive liquid and is
usually about 95 percent pure. Upon application to soils containing
calcium carbonate it immediately reacts to form calcium sulphate and
thus provides soluble calcium indirectly. Chemical reactions involved
are:
Na2CO3 + H2SO4 = CO2 + H2O + Na2SO4 (leachable)
CaCO3 + H2SO4 = CaSO4 + H2O + CO2

40. Iron sulphate and aluminium sulphate (alum)
Chemically these compounds are FeSO4.7H2O and Al2(SO4)3.18H2O
respectively. Both these solid granular materials usually have a nigh
degree of purity and are soluble in water. When applied to soils,
these compounds dissolve in soil water and hydrolyse to form
sulphuric acid, which in turn supplies soluble calcium through its
reaction with lime present in sodic soils. Chemical reactions
involved are:
FeSO4 + 2H2O = H2SO4 + Fe (OH)2
H2SO4 + CaCO3 = CaSO4 + H2O + CO2
Similar reactions are responsible for the improvement of sodic soils when aluminium sulphate is
used as an amendment.

41. Sulphur (S)
Sulphur is a yellow powder ranging in purity from 50 percent to more
than 99 percent. It is not soluble in water and does not supply
calcium directly for replacement of adsorbed sodium. When applied
for sodic soil reclamation, sulphur has to undergo oxidation to form
sulphuric acid which in turn reacts with lime present in the soil to
form soluble calcium in the form of calcium sulphate:
2 S + 3 O2 = 2 SO3 (microbiological oxidation)
SO3 + H2O = H2SO4
H2SO4 + CaCO3 Û CaSO4 + H2O + CO2

42. Pyrite
Pyrite (FeS2) is another material that has been suggested as
a possible amendment for sodic soil reclamation. Reactions leading
to oxidation of pyrite are complex and appear to consist of chemical
as well as biological processes. The following sequence has been
proposed for the oxidation of pyrite by Temple and Delchamps
(1953). The first step in the oxidation is non biological and iron II
sulphate (ferrous) is formed

43. 2 FeS2 + 2 H2O + 7 O2 = 2 FeSO4 + 2 H2SO4
This reaction is then followed by the bacterial oxidation of iron II
sulphate, a reaction normally carried out by Thiobacillus
ferrooxidans,
4 FeSO4 + O2 +2 H2SO4 = 2 Fe2 (SO4)3 + 2 H2O
Subsequently iron III sulphate (ferric) is reduced and pyrite is oxidized
by what appears to be a strictly chemical reaction.
Fe2 (SO4)3 + FeS2 = 3 FeSO4 +2 S
Elemental sulphur so produced may then be oxidized by T.
thiooxidans and the acidity generated favours the continuation of the
process
2 S + 3 O2 + 2 H2O = 2 H2SO4
Summary: 4 FeS2 + 2 H2O + 15 O2 = 2 Fe2 (SO4)3 + 2 H2SO4

44. Salt Tolerant Crops
High Medium Low
Barely Castor Pea
Sesabania Cotton Sunhemp
Rice Sorghum Gram
Sugarcane Pearl millet Linseed
Oats Maize Sesamum
Berseem Mustard
Lucerne Wheat

45. Salt Tolerance on the Basis of EC
1 No effects on crop 2 - 4 dSm-1
2 Sensitive crop – restricted yield 4 - 8 dSm-1
3 Many crops restricted yield 8 - 16 dSm-1
4 Most crops restricted yield > 16 dSm-1