This presentation is based on a type of problematic soils. There are many types of problematic soils and it is one of them.

1. INTEGRAL UNIVERSITY
(INTEGRAL INSTITUTE OF AGRICULTURAL SCIENCE
AND TECHNOLOGY )
SUBMITTED BY - Deependra Gupta
SEMESTER- iv YEAR – 2nd
SUBMITTED TO - SMRITI RAO MA’AM

2. TOPIC -
ACID SOIL AND ITS
RECLAIMATION

3. CONTENT
• Soil Definitions
• Problem soil
• Acid Soil
• Acid soil groups and its
distribution
• Characteristics of acid soils
• Types of soil acidity
• Reasons for soil acidity
• How acid soil is formed ?
• Amelioration

4. SOIL DEFINITIONS
• Dokuchaev(1900) defined soil as a natural body
composed of mineral and organic constituents,
having a definite genesis and distinct nature of its
own.
• Hilgard (1892) - viewed soil as more or less a loose and
friable material in which plants , by means of their roots
find a foothold for nourishment as well as for other
condition of growth .
• Ruffin (as quoted by Simonson , 1968 ) - considered soil as
a mixture of earth’s uppermost mantle of weathered rocks
and organic matter .
• Joffe (1949) - conceived soil as a natural body of mineral
and organic constituents , differentiated into horizons of
variable depth , which differs from the materials below in
morphology , physical make up , chemical properties and
composition , and biological characteristics .

5. PROBLEM SOIL
• It is defined as the soil which possess characteristics which makes them uneconomical for the cultivation of
crops without adopting proper reclaimation measure .
• The ‘problem soil’ herein 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, organic soil, skeletal soil and shallow soil. Furthermore, it may also include areas with steep slope. If
these lands are used for agricultural purpose, then it may cause some severe effects on the ecology and
environment.
• There are three types of Problem soils ;
1. Physically degraded soils
2. Chemically degraded soils
3. Biologically degraded soils (not found in india)
Also Nutritional degraded soil (not included)

6. ACID SOILS
• Soil with low pH (less than 7) contain relatively high amounts of exchangeable H+ and Al3+ considered as
the acid soil.
• Acidic property measured by the amount of the Hydronium ion present in the solution , more hydronium
ions means more acidic , fewer hydronium ions means less acidic or Alkaline.
• In India 49 mha is covered by acid soils out of which 26 mha is under the pH below 5.6 and 23 mha is
under the pH 5.6-6.5 .
• In the world the acidic area is 800 mha .
• Soil pH should have above 5.5 for the top layer & above 5 for sub layer .
• Kw = [H+] [OH-]
= [10 -7] [10 -7]
=[10 -14]
• Acid soils have Al3+ , H+ , Fe 2+ , Oxides of Al & Fe.
• A soil which is acidic in nature creates problem for the growth and development of crops.

7. ACID SOIL GROUPS AND ITS DISTRIBUTION
Soil Group
1. Laterite (Acidic Light Soil)
2. Laterite soil (Slightly acidic )
3. Mix red and yellow soil
4. Ferruginous red & gravely soil
5. Foothill soil
6. Peat soil
Soil pH
4.8 – 7
5 - 7
5.5 - 6.5
5.2 – 6.7
4.5 – 6.5
3.5 – 4.5
Distribution
Tamil Nadu , Karnataka , M.P , W.B
, Jharkhand , Kerala , Assam.
Northeast States , Assam , W.B ,
Tamil Nadu , Kerala , Orissa ,
Jharkhand .
Karnataka , M.P , U.P , Orissa ,
Chotanagpur region of Jharkhand ,
Goa , Maharashtra .
Andaman , U.P , Orissa , Goa , North
east , W.B and AssaM.
Jammu & Kashmir , Uttar Pradesh ,
West Bengal .
Present in Assam and Keral .

8. ACID SOIL GROUP AND ITS DISTRIBUTION
Soil Group
7. Alluvial soils
8. Coastal Alluvial Soil
9. Degraded soil & Acid saline soil
Soil pH
4.2 – 5.8
3.5 – 5.8
5.2 – 6.6
Distribution
West Bengal , Bihar , Assam , Uttar
Pradesh .
Kerala , West Bengal and Tamil
Nadu.
West Bengal , Orissa , Tamil Nadu &
Kerala.

10. CHARACTERISTICS OF ACID SOILS
Physical
• Light texture soil.
• High permeability
• Poor water holding capacity
• Poor organic matter content.
Chemical
• Base unsaturated soil
• More anions than cations
• Active and potential soil acidity
• Toxic effects of Al concentration
more
• At low pH- Al , Fe , Mn , Zn , Cu
, Co , availability is more
• P , Ca , Mg is less .
Biological
• Fungi population is more than that of
bacteria
• Fungi causes root disease
• Rate of decomposition of biological
material and the rate of
mineralization and nitrification are
reduced when acidity is increased .

11. TYPES OF SOIL ACIDITY
Active Acidity
• It measures hydrogen , aluminium
, Iron & Oxides of aluminium, iron
(H+ , Al3+ , Fe3+ ,oxides of
aluminium and iron ) in the soil
liquid phase or solution.
• It is very small Compared to other
acidity .
Exchangeable Acidity
• Also called as Salt Replaceable
acidity , where H+ ,Al3+, Fe3+ , and
Oxides of Al and Fe are present in
the solid phase.
• It can only be released in soil
solution by an un buffered salt like ,
potassium chloride.
• Exchangeable acidity is high for
Smectite mineral , which is
intermediate for Vermiculite mineral
and it is low for Kaolinite mineral.
Residual Activity
• After the neutralization of active
and exchangeable acidity , some
amount of H+, Al3+, Fe3+ and
oxides of Al & Fe are present in
the soil is termed as Residual
acidity.
• It is thousand times greater than
active acidity in the sandy soil
and fifty thousand to one lac
times greater than active acidity
in clayey soil.

12. REASONS FOR SOIL ACIDITY
• Rainfall
• Parent Materials
• Fertilizer application
• Plant root activity
• Decomposition of Organic matter
• Climate
• Vegetative Cover
• Topography
• Human interference

13. RAINFALL
• Mostly found in the excess rain fall areas
(Hilly areas) .
• Excess rainfall leaches base cation from the
soil.
• Additionally rain water has a slightly acidic
pH is 5 .
• Creates base unsaturation .
• Increase the percentage of Hydrogen and
Aluminium ion in the soil .

14. PARENT MATERIAL
• The development of acid soil on acidic rocks like Granite , Gneiss ,
quartz , silica .
• When these rocks lacks bases , produce acidity in the soil after
decomposition by weathering.
• Silica acid – Orthosilicic acid and trisilicic acid
Reason for development of acid soil from parent material
• Parent rock with simple composition .
• Less absorbed cation .
• Poor buffering capacity .
• Quick percolation of water through them .

15. FERTILIZER USE
• Repeated application of ammoniacal fertilizer
leads to formation of acid soil.
• Ammonium sulphate & Ammonium nitrate
fertilizer reacts in the soil process is called
nitrification to form a nitrate.
• This process releases the Hydronium ions.

17. PLANT ROOT ACTIVITY
• Plant uptake nutrients in the form of both
anion and cation .
• Plant must maintain a neutral charge in their
roots .
• In order to compensate the extra positive
charge they release the H+ ions .
• Some plants root produce the organic acid –
acid soil .

18. DECOMPOSITION OF ORGANIC MATTER
Decomposition process requires the microorganism
Microorganism CO2 – release the CO2
CO2 reacts with soil water and produces the carbonic acid
Acid Soil

19. TOPOGRAPHY
• Sloppy places with good drainage condition are supposed to be
development of acid soil .
• Development of acid soil is very easy in the hilly slopes .
• In plains with good drainage condition enhances the acid soil .
HUMAN INTERFERENCES
• Industrial wastes containing sulphur / sulphur dioxide contribute
acid soils .
• Regular use of nitrogen fertilizers by farmers .
• The improved drainage near submerged lands .

20. HOW ACID SOIL IS FORMED
• H+ and Al3+ both contributes soil acidity .
• H+ contributes soil acidity directly while Al3+ do so indirectly through
hydrolysis .
• In aqueous solution Al3+ do not remain as free ion , it is surrounded by 6 H2O
molecules forming Hexaaquaaluminium compound Al(H2O)6
3+
HOH HOH HOH
Al(H2O)6
3+
HOH HOH HOH

21. DIFFERENT ALUMINIUM FORMS AT DIFFERENT PH
LEVEL
1. Less than pH 4.5 -
Al(H2O)6
3+ + H2O = Al(H2O)6
3+ + Al(H2O)5 (OH)2+ + H3O+
2. Between pH 4.5 – 6.5 –
Al(H2O)5(OH)2+ + H2O = Al(H2O)4 (OH)2
+ + H3O+
3. Between pH 6.5- 8 –
Al(H2O)4(OH)2
+ + H2O = Al(H2O)3 (OH)3
0 + H3O+
4. Between pH 8-11 -
Al(H2O)3(OH)3
0 + H2O = Al(H2O)2 (OH)4
- + H3O+

22. • Under strong acid soil , absorbed Al is equilibrium to Al3+ in soil solution .
Al Al3+ (solution)
Al3+ + H2O Al(OH)2+ + H+
• Moderately acidic condition -
Al(OH)2+ + H2O Al(OH)2
+ + H +
Al(OH)2
+ + H2O Al(OH)3
0 + H+
• Al toxicity affects plant growth in various ways ;
1. Restricts root growth .
2. Affects various plant physiological process .
3. Restricts absorption and translocation of some important nutrient elements like P, Ca ,
Fe , Mn .
4. Causes wilting of plants
5. Inhibits the microbial activity in the soil

23. AMELIORATION
• Use of lime and liming materials .
• Lime is applied in the form of limestone
1. Calcite (CaCO3)
2. Dolomite ( CaMg(CO3)2 )
3. Mixture of both
• With increase in CO2 partial pressure , the limestone solubility also increases .
CaCO3 + CO2 + H2O = Ca (HCO3)2 {Calcium Carbonate }
Ca(HCO3)2 = Ca2+ + 2HCO3
- { Bi-carbonate }
H+ + HCO3
- = H2CO3 H2O + CO2

24. • Three Factors affecting liming
1. Carbon concentration should be low .
2. Moisture should be more .
3. Amount of Exchange acidity .
Agricultural Liming Material -
1. Oxides of lime ( Burned lime or quick lime )
CaCO3 + Heat = CaO + CO2
CaMg(CO3)2 + Heat = CaO + MgO + 2CO2
Produced by heating -
Soil (Al , H) + H2O + 2CaO = Soil (Ca , H ) + Al(OH)3
2. Hydroxides of Lime (Slaked Lime )
Water + Burned Lime
CaO + H2O = Ca(OH)2
Ca(OH)2 + H2O = CaCO3 + H2O
Mg(OH)2 + CO2 = MgCO3 + H2O
Soil (Al , H ) + 2Ca(OH)2 = Soil ( Ca , H) + Al(OH)2 + H2O

25. 3. Carbonates of Lime -
- produced in industries
- CaCO3 & CaMg(CO3)2
• CaCO3 + HCO3 = Ca(HCO3)2
• Soil(H) + Ca(HCO3)2 = Soil(Ca) + 2H2O + 2CO2
• Soil (H) + CaCO3 = Soil (Ca) + 2H2O + CO2
4. Slags –
It is of three types ;
a) Blast Furnace Slag - Pig iron manufacture , Calcium Silicate behaviour , NV = 75-90% .
b) Electric Furnace Slag – Reduction of phosphate rock during preparation of element ‘P’
c) Basic Slag - By product of open hearth method of making steel from pig iron , NV=60-70% .
Soil ( H, Al ) + 2CaSiO3 = Soil( Ca ) + 2H2SiO3 + Al(OH)3

26. EFFICIENCY OF LIMING
MATERIAL
1. NV or Calcium Carbonate equivalent of liming materials
Neutralizing value (N.V) = Molecular Weight of CaCO3 * 100
Molecular weight of liming material whose CCE is to be
determined
2. Purity of liming material = Purity , Effectiveness
3. Degree of fineness = Fine , surface contact with soil
60% mesh sieve = 100% fine
20% mesh sieve = 60% fine
8% mesh sieve = 20% fine
Neutralizing Index = CCE * Fineness factor

27. Why Gypsum is not considered as Liming Material ?
• CaSO4 Ca2+ + SO4
2- (dissociates )
• SO4
2+ + H2O H2SO4 (Strong acid )
• Ca replaces the Al3+ (absorbed) only when applied at band placement .
• Overliming causes Boron Deficiency .