This document discusses different types of problematic soils, including physical, chemical, and biological problem soils. It focuses on the mineralogy and classification of soils with physical problems like slow permeability, crusting, hard pans, and shallowness. It also examines chemical problem soils that are alkaline, acidic, or saline. Alkaline soils are further classified as non-saline alkali or saline-alkali soils. Key factors that determine alkalinity like carbonate species, pH, sodium adsorption ratio, and residual sodium carbonate are defined. An experiment analyzing the mineral composition of different soils through X-ray diffraction is summarized.

1. MINEROLOGY ANDCLASSIFICATIONOF
DIFFERENT PROBLEMATICSOILS
PRESENTED BY
NIHAR RANJAN DASH
COLLEGE OF AGRICULTURE,OUAT, BBSR

2. • The ‘problem soil’ here in means the soil that has agricultural problems
due to the soil’s unsuitable physical and chemical properties, or less suitable for
cultivation, resulting in that crops are not able to grow and produce yields as
normal.
• These soils always occur naturally, including saline soil, acid sulfate soil, sandy
soil, shallow soil etc.
• Types of problem soils
• Physical problem soils
• Chemical Problem soils
• Biological Problem soils
• Nutritional problem soils as a result of above constraints

3. • Soils with Physical problems
• 1.Slow permeable soil
• mainly due to very high clay content,
• infiltration rate < 6cm/day, so more runoff which eventually leads
to soil erosion and nutrient removal.
• it leads to impeded drainage, poor aeration and reduced
conditions.
2.Soil surface crusting
• It is due to the presence of colloidal oxides of iron and aluminium
in soils which binds the soil particles under wet regimes.
• On drying it forms a hard mass on the surface.
• It is predominant in Alfisols but also occur in other soils too.
• Impact on soil properties
• Prevent germination of seeds and retards root growth
• Results in poor infiltration and accelerates surface runoff
• Creates poor aeration in the rhizosphere
• Affects nodule formation in leguminous crops

4. .Sub soil hard pan
• Sub soil hard pan is commonly found in red soils.
• Though soil is fertile, crops cannot absorb nutrients
• The reasons for the formation of sub surface hard pan in
red soils is due to the illuviation of clay to the sub soil
horizons coupled with cementing action of oxides of iron,
aluminium and calcium carbonate.
• The sub soil hard pan is characterized by high bulk
density(>1.8Mg m-3
• which in turn lowers infiltration, water holding capacity,
available water and movement of air and nutrient

5. • .Highly permeable soils
• Sandy soils containing more than 70 per cent sand fractions
occur
• in coastal areas, river delta and in the desert belts.
• Excessive permeability of the sandy soils results in poor
water retention capacity, very high hydraulic conductivity and
infiltration rates.
• These soils being devoid of finer particles and organic matter,
the aggregates are weakly formed, the non-capillary pores
dominating with
• very poor soil structure.
• So whatever the nutrients and water added to these soils are
not utilized by the crops and subjected to loss of nutrients
and water.

6. Heavy clay soils
• Clay soils are referred as heavy soils. To be classified as clay soil,
• it should be made up of about 40% clay particles, the finest
particles
• found in soil.This is also slowly permeable soils.
• .Shallow soils
• Shallow soils are formed due to the presence of parent rocks
immediately below the soil surface ( 15-20 cm depth).
• Impact
• The shallow soil restricts root elongation and spreading.
• Due to shallowness less volume of soil is available exhaustive
soil nutrients

7. • 2. Chemical Problem soils
•Three major types of problematic soils.
• The types are:
•1. Alkaline Soil
•2. Acidic Soil
•3. Saline Soil.

9. • Alkaline Soil (Sodic Soil):
• (a) Non-saline-alkali soils:
• The characteristic features are the presence of collodial complex that is saturated
with exchangeable sodium, and the absence of appreciable quantities of soluble
salts.
• These soils are often called ‘black alkali’ soils, because they are black, owing to the
effect of the high sodium content which causes the dispersion of the organic
matter. These soils are also called typical usar soils. These soils contain sodium
carbonates (Na2CO3 ) in abundance..
• Colloidal complex is deflocculated and dispersed.
• The clay swells and chokes the soil pores. Hence, permeability to water and air is
poor
• The presence of free sodium carbonate has a toxic effect on plant roots.
• Also, the high pH and poor physical condition of soil adversely affect plant growth.

10. • Alkalinity refers to the concentration of hydroxide (OH-) ions in the soil.
• The hydroxide producing anions in soil are usually carbonate and bicarbonate.
• direct relationship between carbonate/bicarbonate and hydroxide ion
concentration, while proton (H+) concentration is inversely related to
carbonate/bicarbonate concentration.
• The carbonate comes from the dissolution of minerals such as calcite, dolomite
The reactions are:
• Calcite
• CaCO3 + H+ € Ca2+ + HCO3
-
• Dolomite –
• CaMg(CO3)2 + 2H+ HCO3
- + Ca2+ + Mg2+
• Carbonate reacts with these salts to form sodium carbonate or calcium
carbonate which dissociates in water to form carbonic acid e.g.:
• Na2CO3 + 2H+ 2Na+ + 2OH-+ H2CO3

11. • The carbonic acid, is unstable and produces water and carbon
dioxide:
• H2CO3 H2O + CO2
• The net reaction is:
• Na2CO3 + H2O 2Na + + + 2OH- + CO2
• Thus the OH- anions are responsible for the high alkalinity.
• Because sodium carbonates and bicarbonates are more water
soluble than calcium carbonates, more hydroxyl ions are
produced by them and a higher pH results (Brady & Weil 1999).

12. • Whereas calcium carbonate-dominated soils typically
have a pH of around 8.3, association between sodium
and carbonate species can result in a higher pH (10 or
more).
• Alkalinity then is a function of soil carbonate levels;
• specifically: Alkalinity = [HCO3
-] + 2[CO 3
-2] + [OH-] – [H +
] (Sposito 1989)

13. • The presence of abundant Na + + ions in the soil solution and the
precipitation of Ca+ + ions as a solid mineral causes the clay
particles, which have negative electric charges along their
surfaces, to adsorb more Na + in the diffuse adsorption zone)
• in exchange, release previously adsorbed Ca + + , by which their
exchangeable sodium percentage (ESP) is increased Na + is more
mobile and has a smaller electric charge than Ca + + so that the
thickness of the DAZ increases as more sodium is present.
• Clay particles with considerable ESP (> 16), in contact with non-
saline soil moisture have an expanded DAZ zone and the soil
swells (dispersion).

14. • Carbonate species and pH
• At pH 8.3 and higher, the proportion of bicarbonate (HCO3
-) begins to decrease as
it is converted to carbonate:
• HCO3
- + OH- CO3
- - + H2O
• Whereas bicarbonate exists in solution up to and beyond a pH of 12, the relative
proportion in solution decreases as carbonate formation occurs at a rate 10 times
faster than bicarbonate per unit increase in pH (Lindsay 1979).
pH
Figure 2.3 Relative proportions of carbonate
species with changing pH (Lindsay 1979a).

15. • The quality of the irrigation water in relation to
the alkalinity hazard is expressed by the following two
indexes:
• The sodium adsorption ratio (SAR, ) The formula for
calculating sodium adsorption ratio is:
• SAR = [Na+]/√[Ca++/2 + Mg++/2]
• The SAR should not be much higher than 20 and preferably
less than 10; When the soil has been exposed to water with
a certain SAR value for some time, the ESP value tends to
become about equal to the SAR value.
• The residual sodium carbonate (RSC, meq/l): The formula
for calculating residual sodium carbonate is: [HCO3
-+ CO3
- -] −
[Ca+ + + Mg+ + ]
• which must not be much higher than 1 and preferably less
than 0.5.
The above expression recognizes the presence
of bicarbonates (HCO3
–), the form in which most carbonates are
dissolve

16. RSC = [HCO3
– + CO3
=] − [Ca+++ Mg++]
= {HCO3
–/61 + CO3
=/30} − {Ca++/20 + Mg++/12}
• Alkaline soils, in principle, are not saline since the alkalinity
problem is worse as the salinity is less.
• Alkalinity problems are more pronounced in clay soils than in
loamy, silty or sandy soils.
• The clay soils containing montmorillonite or smectite (swelling
clays) are more subject to alkalinity problems
than illite or kaolinite clay soils.
• The reason is that the former types of clay have larger specific
surface areas (i.e. the surface area of the soil particles divided by
their volume) and higher cation exchange capacity (CEC).
• Note:
• Certain clay minerals with almost 100% ESP (i.e. almost fully
sodium saturated) are called bentonite, which is used in civil
engineering to place impermeable curtains in the soil, e.g. below
dams, to prevent seepage of water.

17. Experiment : Mineral composition of soils
• Soil mineralogy was determined quantitatively via X-ray
diffraction (XRD). Samples were lightly ground in an agate
mortar and pestle and back pressed into stainless steel holders for
analysis.
• XRD patterns were recorded.
Soil pH
Carbonat
e (%)
Exchangeable
cations
(Meq/100g)
Ca Mg Na K
ESP
Monarto 8.7 36.0 10.8 8.6 2.6 3.0 12.0
Ardrossan 9.5 39.4 9.4 6.8 1.2 4.6 20.9
Minlaton 8.8 35.5 9.8 8.7 1.6 5.9 22.3
Paskerville 9.6 45.2 8.8 6.9 2.4 5.9 24.6
Keilira 1 9.9 52.0 15.6 10.8 1.8 9.8 25.8
Keilira 2 9.2 53.9 16.8 12.5 2.0 10.7 25.4
Bordertow
n
9.3 6.0 5.6 7.7 1.4 3.3 18.3

18. Soil Quartz Orthoclase/
Microcline
Albite/
Anorthite
Anatase Hematit
e
Calcite/
Mg-Calcite
Dolomite/
Ankerite
Kaolini
te
Smectite Illite
Monarto 42 2 1 0 1 33 3 1 17 0
Ardrossan 29 2 2 0 0 39 0 2 26 0
Paskerville 31 2 2 0 <1 29 16 1 18 0
Minlaton 39 3 3 0 0 33 3 1 18 0
Keilira 1 23 0 <1 0 0 41 11 <1 23 0
Keilira 2 15 <1 <1 0 0 29 25 <1 28 0
Table 5.1 Mineralogy of whole soils as determined by X-ray diffraction % (accuracy
+/- 5%).

19. • RESULT AND DISCUSSION
• Clay component
• X-ray diffraction analysis showed soil mineralogy was dominated
by carbonates, (primarily calcite/Mg-calcite and
dolomite/ankerite).
• Quartz made up between 15- 42 percent of the soils and
smectite featured prominently in all soils (17 – 28%).
• The soils generally showed small amounts of
orthoclase/microcline, kaolin and albite/anorthite
• The clay component of the soils was dominated by smectite .
• Calcite was prominent in Keilira 1 whereas calcite and
dolomite/ankerite were significant for Keilira 2

20. • Saline-alkali soils:
• These soils are both saline and alkali. There can be all stages in transition with
varying degree of dominance of salt content and pH.
• According to movement of soluble salts, formation of saline-alkali and non-
saline alkali soils depends..
• If the soluble sodium salts are not leached out due to the insufficiency of rain
water, they remain in the soil.
• The soil thus contains Na-clay and excess soluble, salts in solution. Such soils
are known as saline-alkali soils.
• They are thus, developed as a result of the combined process of salinization
and alkalization.
• In spite of the presence of sodium clay (Na-clay) the soil remains friable and
possesses aggregate (flocculated).
• This is because the presence of sodium salts does not allow the sodium clay to
get dispersed and keeps it flocculated.
• Thus, this soil behaves more or less like saline soils
• A variable pH, usually above 8.5, depending upon the relative amounts of
exchangeable sodium and soluble salts
• Generally soluble salts content is more than 0.1%.

21. • Degraded Alkali Soils:
• The soil does not contain free calcium carbonate (CaCO3). As a result of
prolong leaching under this condition,Na-clay hydrolyses NaOH which
combines with CO2 or soil air and forms sodium carbonate (Alkaline
condition).
• Sodium carbonate (Na2CO3) dissolves humus. Humus (organic matter) is
deposited in the lower layer. The lower layer thus, acquires a black colour.
• At the same time, a part of exchangeable sodium of the surface layer is
replaced by hydrogen. H-clay (acid soil) formed in this way does not remain
stable.
• The process of break-down of H-clay under alkaline condition is known as
solodization and the soil as formed is called Solod, Soloth or degraded alkali
soil.
• (i) The soil reaction of the surface layer is acidic (pH 6.0).. The lower layer
which constitutes the main soil body has a high pH (more than 8.5).
• (iii) ESP is greater than 15%.
• (iv) EC less than 4 mmhos/cm.
• (v) The lower layer has black colour.

22. Acid soil
• Soil acidity may be defined as the soil system’s proton(H+) donating
capacity during its transition from a given state to a reference state.
• Soil with low pH containing higher amount of Hydrogen(H⁺ ) and
Aluminium ion(Al3+) are considered as acid soils.
Type pH ranges
Ultra acidic 3.3
Extremely acidic 3.5 to 4.5
Very strongly acidic 4.5 to 5.0
Strongly acidic 5.1 to 5.5
Moderately acidic 5.6 to 6.0
Slightly acidic 6.1 to 6.5

23. Occurrence in Odisha
About 70% of the net sown area
of the state is acidic. (4096 th
ha)
About 21.1% of acid soil (13
lakh ha) with pH <5.5 need
immediate liming.
Entire upland and major part of
medium land are acidic in
nature.

24. Sources of Soil Acidity
Rain fall
Climate
Topography
Parent materials
Fertiliser application
Vegetation cover
Plant root activity
Decomposition of organic matter
Human interference

25. Types of acidity
• There are 3 major forms of soil acidity namely
 Active acidity
Exchaneble acidity
Residual acidity
Total acidity= Active acidity+ Exchangableacidity + Residual acidiy

26. 1.Active acidity
• Active acidity may be defined as the acidity developed due to
Hydrogen (H+) and aluminium (Al)3+ ions concentration of the soil
solution.
• Active acidity is extremely important , because it determines the
solubility of many substances & provides the soil solution
environment to which plant roots and microbes are exposed.
• This pool is very small , as compared to the acidity due to
exchangeable and residual pools.

27. Exchangeable or Salt-replaceable acidity
• This is primarily associated with exchangeable Al3+ & H+ ions, that
are present in large quantities in strongly acid soils.
• Exchangable acidity is very high in soils with moderate to strong
acidity, and is very difficult to neutralise.
• The exchangeable H+ & Al3+ replace into the soil solution by cation
exchange with an un-buffered salt, such as KCl as follows-
Clay-(Al3+,H+)+ 4KCl Clay-(K+) +AlCl3 + HCl
Soil solid soil solution Soil solid soil solution

28. Residual acidity
• Residual acidity generally associated with H+ &Al3+ ions , that are
bound in non-exchangeable forms by clay and organic matter in the
soil.
• The residual acidity is commonly far greater than the active or
exchangeable acidity. It may be 1000 times greater than the active
acidity in a sandy soil and 50,000 or even 1,00,000 times greater in a
clay soil high in organic matter.

30. Chemistry of Aluminium in the development of soil
acidity
• It is evident that hydrogen and aluminium both contributes soil acidity.
Hydrogen ion contribute soil acidity directly while aluminium ions do so
indirectly through hydrolysis.
• In aqueous solution Al3+ doesnot remain as free ion , but is sorrounded by
six molecules of water forming hexaquoaluminium compound
[Al(H2O)6
3+].
• As the soil water solution becomes less acidic , one or more aluminium
held water molecules ionizes H+ ions which are less attracted to oxygen of
water molecules held to the aluminium.
• The aluminium ion becomes successively less positively charged by such
ionization. At different pH levels, these are the forms of aluminium in soil.

32. Clay minerals of acid soil

33. Characteristics of acid soils.
• According to USDA soils having pH<5.5 in 1:1 soil soil-water suspension are called
as acid soils.
• Low pH and high proportion of exchangeable H and Al are the main
characteristics of an acid soil.
• Kaolinite and illitic type of clay minerals are dominant in these soils, halloysite
has also been detected in some cases.
• Presence of Al, Mn and Fe can be seen in toxic concentrations.
• The acid soils are generally low in available P and have high Po4 fixation capacity.
• The status of available micronutrient elements ,except Mo is generally adequate
in these soils. However Mg deficiency is common in legumes, cruciferae and
citrus grown in these soils.
• Deficiency of Ca and Mg can be seen.
• It also inhibits biological nitrogen fixation.

34. Problem of acid soil AND ACID SULPHATE SOIL
1. Toxicity of elements (Al, Mn, Fe )
2. Deficiency of bases (Ca+2, Mg+2)
3. Imbalance of P,S and Mo
4. Poor microbial activity
a) Toxic effects of Al :- Al inhibits the root growth of the plants, interferes with the
various physiological process of the plants like cell-division, respiration and DNA
synthesis; restricts the uptake of Ca+2, P and H2O
b) Mn–toxicity: In soils having pH below 5.0, excess Mn accumulates in all the
tissue of the plant, the normal metabolism of the plant is seriously affected.
c)Fe-toxicity: iron concentration in soil increases with the decrease in pH,
increase in O.M. content and the intensity of soil reduction
Under waterlogged condition of rice cultivation the soil undergoes reduction which
reduces Fe+3 iron to Fe+2 iron which is more soluble and sometimes the concentration of
Fe+2 in waterlogged rice soils becomes high and become toxic to rice plants. This
creates what is known as physiological diseases of rice(browning disease).

35. 2. Deficiency of bases:
a) The amount of exchangeable Ca, Mg is lower in acid soils. Percentage base
saturation is also low as the most exchangeable sites are occupied by Al and H. Ca
and Mg are secondary essential elements as far as plant nutrients are concerned.
Plant (Leguminous plant) require high amount of Ca and Mg. Due to lack of Ca and
Mg yield will be hampered. But Rice, wheat do not require Ca, Mg, so not seriously
affected.
b) Ca, Mg improve the structure of the soils and so their deficiency will give rise to
poor structure of the soil and thus they inhibit proper aeration.
c) Microbial activities are also decreased due to the insufficiency of bases. So,
mineralisation will be adversely affected .
3. Imbalance of Nutrient elements:
a) Phosphorus: i) P in soil is precipitated due to formation of AlPO4 and FePO4. In acid
soil Al and Fe concn is high. So availability of P in acid soil is very low.
ii) Plant generally take up P from soil in the form of H2PO4
- and HPO4
-2. Chemical
adsorption on the surface of the colloidal material and soil dominated with kaolinite
clay mineral adsorbs more P. Therefore, P is not released from the surface and P
availability will be low.

36. b) Sulphur: Most of the S in soils present in organic form. These organic S are
mineralised by some soil microbes. But in acid condition, they can’t function well
to mineralise the S. these micro org. can’t grow well in low pH. Unless these S are
changed to inorganic form, plant can’t absorbs S as nutrients.
c) Molybdenum (Mo): generally micro nutrients are more soluble in acid soil but
Mo is the exception. Mo is less soluble in low pH and thus becomes less
available to the plants. In acidic condition it produces insoluble molybdates.
Lack of Mo reduces N-fixation.
4. Poor microbial activity:
most of the microbes prefer neutral pH. So in acid condition their activity will be affected.

37. Nutrient
availability
varies with pH

38. OBSERVATION OF CASE STUDY

39. RESULT AND DISCUSSION

40. SALINE SOIL
WHAT IS SALINE SOIL?
Saline soil is a term used to describe excessive levels of soluble salts in
the soil water (soil solution), high enough to negatively affect plant
growth, resulting in reduced crop yields and even plant death under
severe conditions.
Charateristic of saline soil
• High amount of neutral Soluble salts most commonly present are
the chlorides and sulphates of sodium, calcium and magnesium.
• Electrical conductivity of the saturation soil extract of more than 4
dS/m at 25°C.
• pH value of the saturated soil paste is always less than 8.5 .
• SAR is <13 and ESP <15
• Soil remain floculated
• Surface encrustation of soluble salt

41. Causes of Soil Salinity
• Soluble Salts
• In arid and semiarid climates, there is not enough water to leach soluble
salts
• from the soil. Consequently, the soluble salts accumulate, resulting in salt
affectedsoils.
• The major cations and anions of concern in saline soils and waters are Na+,
Ca2+, Mg2+, and K+, and the primary anions are Cl–, SO4
2–,HCO3
- , CO3
2- , and
NO3
- .
• In hypersaline waters or brines, B, Sr, Li, SiO2 ,Rb, F, Mo, Mn, Ba, and Al
(since the pH is high Al would be in the Al(OH)4
- form) may also be present
(Tanji, 1990b).
• Bicarbonate ions result from the reaction of carbon dioxide in water. The
source of the carbon dioxide is either the atmosphere or respiration from
plant roots or other soil organisms.
• Carbonate ions are normally found only at pH ≥ 9.5. Boron results from
weathering of boron-containing minerals such as tourmaline .

42. • When soluble salts accumulate, Na+ often becomes the dominant counterion
• on the soil exchanger phase, causing the soil to become dispersed. This results
• in a number of physical problems such as poor drainage.
• Evapotranspiration
• An additional factor in causing salt-affected soils is the high potential
evapotranspiration
• in these areas, which increases the concentration of salts in both soils and
surface waters.
• It has been estimated that evaporation losses can range from 50 to 90% in arid
regions, resulting in 2- to 20-fold increases in soluble salts
• Drainage
• Poor drainage can also cause salinity and may be due to a high water table or
• to low soil permeability caused by sodicity (high sodium content) of water.
• Soil permeability is “the ease with which gases, liquids or plant roots
penetraten or pass through a bulk mass of soil or a layer of soil”).

43. • Factor affecting salinity
• Irrigation water quality- The total amount of dissolved salts
in the irrigation water, and their composition, influence the
soil salinity
• Fertilizers applied- Some fertilizers contain high levels of
potentially harmful salts, such as potassium chloride or
ammonium sulphate. Overuse and misuse of fertilizers
leads to salinity buildup
• Irrigation regimen and type of irrigation – drip irrigation
causes more salinity problem .
• Brakish Under ground water table –by evaporation the
underground watr comes to surface and get deposisted on
the surface .
• submerged Coastal area- sea water carries salt with it and
get deposited in the soil

44. Manegement of saline soil
• Deep ploughing and sub soiling
• profile inversion
• Flushing of water
• Scrapping
• Use of organic matter
• Application of lime

45. • Reference
.
www. http://krishikosh.egranth.ac.in/handle.