Potassium-forms, equilibrium in soils and its agricultural significance; mechanism of potassium fixation; management of potassium fertilizer under field condition
Potassium- Forms,Equilibrium in soils and its agricultural significance ,mech...Vaishali Sharma
The slide is conserned with the potassium fertilisers apllied in the soils. When the fertiliser applied in higher amount then it is avail in different form for plant uptake and there exist a equilibrium in soils and it has many agricultural significance and the slide also deal with brief on the mechanism of potassium fixation in the soil.
The document discusses a midterm exam for a soil science class and various topics related to clay mineralogy and soil properties. It includes the following key points:
1. A midterm exam will take place on February 22nd in the usual classroom at 11 AM.
2. It discusses the properties and structures of common clay minerals like smectite, kaolinite, vermiculite, mica, and chlorite.
3. Ion exchange is described as an important process where ions are exchanged between soil particles and plant roots, affecting nutrient availability and other soil properties.
The document discusses ion exchange reactions in soil, specifically cation and anion exchange. It defines cation exchange as the phenomenon where cations attached to negatively charged soil colloids can be replaced by other cations in solution. Anion exchange is similar, but involves the exchange of negatively charged anions. Cation exchange capacity refers to the total amount of exchangeable cations a soil can hold. Factors like clay content and organic matter influence CEC. Both cation and anion exchange play important roles in nutrient availability and soil chemistry.
Plants absorb essential nutrients from the soil solution through their roots. As nutrients are absorbed, chemical and biological processes in the soil replenish the soil solution. Nutrients are replenished through ion exchange, desorption from soil particles, dissolution and precipitation, and mineralization of organic nutrients. Nutrients move from the soil to the root surface through diffusion, mass flow of soil water, and ion exchange between roots and soil.
This document discusses potassium (K) in soils. It covers the following key points:
- K exists in soils in various forms including solution, exchangeable, fixed, and structural/mineral forms. Exchangeable K is the most plant-available.
- K is essential for plant growth and plays important roles in processes like photosynthesis and enzyme activation. Deficiency causes burn symptoms on older leaves and reduced yields.
- Common fertilizers containing K include potassium chloride, potassium sulfate, and potassium magnesium sulfate. Fertilizer K can increase various forms of K in soils.
- Factors like clay content, soil pH, wetting/drying, and freezing/thawing can influence K
The document provides an overview of potassium acquisition in plants. It discusses sources of potassium in soil, mechanisms of potassium uptake, and factors affecting potassium availability to plants. Key points include: potassium is released through weathering of minerals like feldspar and micas; plants uptake potassium via mass flow, diffusion, and root interception; and soil properties like pH, moisture, temperature impact potassium uptake by plants. The document also examines potassium storage in soil minerals, exchange between soil reserves, and transportation within plant cells.
Potassium- Forms,Equilibrium in soils and its agricultural significance ,mech...Vaishali Sharma
The slide is conserned with the potassium fertilisers apllied in the soils. When the fertiliser applied in higher amount then it is avail in different form for plant uptake and there exist a equilibrium in soils and it has many agricultural significance and the slide also deal with brief on the mechanism of potassium fixation in the soil.
The document discusses a midterm exam for a soil science class and various topics related to clay mineralogy and soil properties. It includes the following key points:
1. A midterm exam will take place on February 22nd in the usual classroom at 11 AM.
2. It discusses the properties and structures of common clay minerals like smectite, kaolinite, vermiculite, mica, and chlorite.
3. Ion exchange is described as an important process where ions are exchanged between soil particles and plant roots, affecting nutrient availability and other soil properties.
The document discusses ion exchange reactions in soil, specifically cation and anion exchange. It defines cation exchange as the phenomenon where cations attached to negatively charged soil colloids can be replaced by other cations in solution. Anion exchange is similar, but involves the exchange of negatively charged anions. Cation exchange capacity refers to the total amount of exchangeable cations a soil can hold. Factors like clay content and organic matter influence CEC. Both cation and anion exchange play important roles in nutrient availability and soil chemistry.
Plants absorb essential nutrients from the soil solution through their roots. As nutrients are absorbed, chemical and biological processes in the soil replenish the soil solution. Nutrients are replenished through ion exchange, desorption from soil particles, dissolution and precipitation, and mineralization of organic nutrients. Nutrients move from the soil to the root surface through diffusion, mass flow of soil water, and ion exchange between roots and soil.
This document discusses potassium (K) in soils. It covers the following key points:
- K exists in soils in various forms including solution, exchangeable, fixed, and structural/mineral forms. Exchangeable K is the most plant-available.
- K is essential for plant growth and plays important roles in processes like photosynthesis and enzyme activation. Deficiency causes burn symptoms on older leaves and reduced yields.
- Common fertilizers containing K include potassium chloride, potassium sulfate, and potassium magnesium sulfate. Fertilizer K can increase various forms of K in soils.
- Factors like clay content, soil pH, wetting/drying, and freezing/thawing can influence K
The document provides an overview of potassium acquisition in plants. It discusses sources of potassium in soil, mechanisms of potassium uptake, and factors affecting potassium availability to plants. Key points include: potassium is released through weathering of minerals like feldspar and micas; plants uptake potassium via mass flow, diffusion, and root interception; and soil properties like pH, moisture, temperature impact potassium uptake by plants. The document also examines potassium storage in soil minerals, exchange between soil reserves, and transportation within plant cells.
Soil Colloids: Properties, Nature, Types and Significance. sources of chargesDrAnandJadhav
This document discusses properties of soil colloids and their significance. It defines soil colloids as soil particles less than 0.002 mm in size that possess colloidal properties. The key types of soil colloids discussed are layer silicate clays, iron and aluminum oxide clays, allophane, and humus. Sources of charge on colloid particles include pH-dependent charge, isomorphous substitution within the crystal lattice, and broken bonds on particle edges. The document outlines various properties of soil colloids and their importance for soil chemistry, nutrient availability, physical properties, and interactions with soil management and pollutants.
Dynamics of k in soils and their role in management of k nutritionAndrew Hutabarat
This document summarizes the forms and dynamics of potassium (K) in soils. It discusses the four main forms that K exists in soils - solution, exchangeable, nonexchangeable, and mineral. Solution K is directly available to plants while exchangeable K is readily available. Nonexchangeable K is moderately available to plants. Mineral K makes up most of the total K in soils but is only slowly available. The document also discusses factors that affect K availability such as reactions between solution and exchangeable K, soil properties, and plant uptake.
The document discusses key properties and composition of soil. It describes how soil properties are determined by geological material, vegetation, weathering over time, topography, and human activities. It focuses on the chemical properties of soil, especially cation exchange capacity (CEC) which is important for soil fertility. CEC is the ability of soil to retain exchangeable cations like calcium, magnesium, potassium and sodium which are important for plant nutrition. Factors that influence CEC include the type and amount of clay minerals and organic matter in the soil.
Potassium is an essential nutrient for plants that is required in large amounts. It makes up 0.2-2.0% of a plant's dry mass. Most of the potassium in soil exists in unavailable forms within minerals or clay layers. Only 0.1-2% exists as exchangeable or soluble potassium available for plant uptake. Proper potassium nutrition is important for plant growth, photosynthesis, enzyme activation, water regulation, and disease resistance. Deficiency causes chlorosis, stunted growth, and poor crop quality. Factors like soil moisture, pH, temperature affect potassium availability. Common fertilizer sources include potassium chloride, potassium sulfate, and potassium nitrate.
This document summarizes the key characteristics of porphyry copper-molybdenum ore deposits. Porphyry deposits form large, low-grade deposits associated with felsic to intermediate porphyritic intrusions. They are commonly found in orogenic belts and areas of thickened crust. Ore minerals like chalcopyrite and molybdenite occur throughout the host rock in stockworks and disseminations. Grades typically range from 0.2-1% copper. Porphyry deposits form due to boiling of copper-rich magmatic fluids from a cooling intrusion, which then mix with meteoric water to deposit sulfide minerals in stockworks.
Soil colloids are very small organic and inorganic particles present in soil that determine its physical, chemical, and fertility properties. The four major colloid types are: 1) clay minerals like silicates, 2) iron and aluminum oxides, 3) allophane and amorphous clays, and 4) humus. Soil colloids influence soil properties through their large surface area, electric charge, and ability to undergo ion exchange with cations in the soil solution. The cation exchange capacity measures the ability of soil colloids to hold exchangeable cations and influences soil fertility and nutrient retention. Maintaining optimal soil pH through liming is important for nutrient availability and crop growth.
potassium fixation in different clay mineralsBharathM64
This document discusses potassium fixation in different clay minerals. It explains that potassium fixation was first reported in 1887 and involves potassium penetrating between clay layers and becoming tightly held. The degree of potassium fixation varies between clay types, with vermiculite showing the highest fixation due to its high charge density and large interlayer space, followed by illite, montmorillonite, and kaolinite. Factors like charge density, interlayer space size, solution concentration, and presence of other cations can influence how much potassium is fixed within clay minerals. The practical implication is that fixed potassium contributes to long-term potassium availability in soils.
The document discusses different groups of clay minerals, including kaolinites, smectites, illites, and chlorites. Kaolinites have a 1:1 layer structure with no interlayer activity or shrink-swell capability. Smectites have a 2:1 layer structure and can expand as water moves between layers. Illites also have a 2:1 layer structure but do not expand, and are common in shales with potassium balancing their negative charge. Chlorites contain an additional brucite interlayer giving them strong bonding between layers.
Explain Langmuir isotherm model and derive its equationZakir Ullah
The document discusses soil chemistry concepts including:
1) Classification of silicate minerals into 1:1 and 2:1 clays based on their structure.
2) Isomorphic substitution in silicate minerals where ions of similar size but different charge replace one another.
3) Calculation of permanent charge in a trioctahedral 2:1 silicate mineral based on isomorphic substitution.
Residual mineral deposits; Laterites; Laterite Profile; Laterisation system; Laterite/Bauxite Conditions; Laterite-type Bauxite, Constitution of Bauxite, Types of deposits; Origin and Mode of formation; Clay (Kaolinite) Deposits; Nickel Laterite Deposits; Mineralogy and Types of lateritic nickel ore deposits; World Nickel Laterite Deposits; Processing of Ni Laterites; Example: Ni-laterites, Ni in soils in east Albania
The document discusses different types of problem soils including acid soils, salt-affected soils, and calcareous soils. It provides details on the distribution and properties of acid soils in India. The major causes of acid soil formation are laterization, podzolization, and leaching in high rainfall areas. Aluminum and iron ions in the soil solution contribute to acidity through hydrolysis reactions. The document also discusses various descriptive terms used to classify soil pH ranges and their associated buffering mechanisms.
This document discusses calcium and magnesium dynamics in soil. Calcium is an important plant nutrient that affects soil physical and chemical properties. Sources of calcium include rocks, minerals, and fertilizers. Calcium availability is influenced by total supply, soil pH, type, cation exchange capacity, percentage saturation, and ratios with other cations. Magnesium is a component of chlorophyll and promotes fat and oil synthesis. Sources include rocks, clays, and fertilizers. Factors affecting magnesium availability include soil type, exchangeable amounts, liming, and ratios with other cations like calcium and potassium. Both calcium and magnesium can be lost from soil through leaching.
Chemistry and physics of submerged soilAnandhan Ctry
This document summarizes submerged soils. It discusses four main types: waterlogged (gley) soils, marsh soils, paddy soils, and subaquatic soils. It describes the characteristics of submerged soils, including the absence of oxygen, chemical changes that occur like reduction, and transformations of carbon, nitrogen, iron, manganese, sulfur, phosphorus, silicon and trace elements. Key points are that submerged soils become anaerobic, chemical elements shift to their reduced forms, and decomposition of organic matter produces gases like methane and hydrogen sulfide.
SUPERGENE ENRICHMENT; Definition; Zones; Morphology of Zoning; Oxidized zone ; Supergene zone ; Gossans and Cappings; Chemical Changes Involved; Electrowinning; Formation of Copper Oxides
Potassium is an essential nutrient for plant growth. It is involved in many important plant processes like photosynthesis, enzyme activation, and water regulation. While total potassium content in soils is usually high, most of it is unavailable to plants. Only a small portion in the forms of exchangeable and water soluble potassium is readily available. Maintaining adequate available potassium levels through fertilization is important for optimal plant growth, yield, quality and stress resistance. Deficiency can cause various symptoms like chlorosis and stunted growth. Proper soil testing and balanced fertilizer management practices are required to supply potassium needs of crops and minimize losses and environmental impacts.
The document discusses clay minerals and their interaction with water. It describes how clay minerals are formed from the weathering of rocks by water. The basic units of clay minerals are silica tetrahedra and octahedral sheets. Clay minerals can have 1:1, 2:1, or 2:1:1 layer structures. Clay particles have negative charges due to isomorphic substitution and broken bonds. Polar water molecules form hydrogen bonds with clay surfaces, becoming tightly bound in monolayers.
This document summarizes the properties and types of soil colloids. It discusses the general properties of soil colloids including their small size, large surface area, surface charges, adsorption of cations and water, cohesion, adhesion, swelling, dispersion, and brownian movement. It describes the four major types of soil colloids - layer silicate clays, iron and aluminum oxide clays, allophane, and humus. Layer silicate clays are further classified into 1:1, 2:1, and 2:1:1 types depending on their crystal structure, with descriptions of common clay minerals in each type.
Soil Colloids: Properties, Nature, Types and Significance. sources of chargesDrAnandJadhav
This document discusses properties of soil colloids and their significance. It defines soil colloids as soil particles less than 0.002 mm in size that possess colloidal properties. The key types of soil colloids discussed are layer silicate clays, iron and aluminum oxide clays, allophane, and humus. Sources of charge on colloid particles include pH-dependent charge, isomorphous substitution within the crystal lattice, and broken bonds on particle edges. The document outlines various properties of soil colloids and their importance for soil chemistry, nutrient availability, physical properties, and interactions with soil management and pollutants.
Dynamics of k in soils and their role in management of k nutritionAndrew Hutabarat
This document summarizes the forms and dynamics of potassium (K) in soils. It discusses the four main forms that K exists in soils - solution, exchangeable, nonexchangeable, and mineral. Solution K is directly available to plants while exchangeable K is readily available. Nonexchangeable K is moderately available to plants. Mineral K makes up most of the total K in soils but is only slowly available. The document also discusses factors that affect K availability such as reactions between solution and exchangeable K, soil properties, and plant uptake.
The document discusses key properties and composition of soil. It describes how soil properties are determined by geological material, vegetation, weathering over time, topography, and human activities. It focuses on the chemical properties of soil, especially cation exchange capacity (CEC) which is important for soil fertility. CEC is the ability of soil to retain exchangeable cations like calcium, magnesium, potassium and sodium which are important for plant nutrition. Factors that influence CEC include the type and amount of clay minerals and organic matter in the soil.
Potassium is an essential nutrient for plants that is required in large amounts. It makes up 0.2-2.0% of a plant's dry mass. Most of the potassium in soil exists in unavailable forms within minerals or clay layers. Only 0.1-2% exists as exchangeable or soluble potassium available for plant uptake. Proper potassium nutrition is important for plant growth, photosynthesis, enzyme activation, water regulation, and disease resistance. Deficiency causes chlorosis, stunted growth, and poor crop quality. Factors like soil moisture, pH, temperature affect potassium availability. Common fertilizer sources include potassium chloride, potassium sulfate, and potassium nitrate.
This document summarizes the key characteristics of porphyry copper-molybdenum ore deposits. Porphyry deposits form large, low-grade deposits associated with felsic to intermediate porphyritic intrusions. They are commonly found in orogenic belts and areas of thickened crust. Ore minerals like chalcopyrite and molybdenite occur throughout the host rock in stockworks and disseminations. Grades typically range from 0.2-1% copper. Porphyry deposits form due to boiling of copper-rich magmatic fluids from a cooling intrusion, which then mix with meteoric water to deposit sulfide minerals in stockworks.
Soil colloids are very small organic and inorganic particles present in soil that determine its physical, chemical, and fertility properties. The four major colloid types are: 1) clay minerals like silicates, 2) iron and aluminum oxides, 3) allophane and amorphous clays, and 4) humus. Soil colloids influence soil properties through their large surface area, electric charge, and ability to undergo ion exchange with cations in the soil solution. The cation exchange capacity measures the ability of soil colloids to hold exchangeable cations and influences soil fertility and nutrient retention. Maintaining optimal soil pH through liming is important for nutrient availability and crop growth.
potassium fixation in different clay mineralsBharathM64
This document discusses potassium fixation in different clay minerals. It explains that potassium fixation was first reported in 1887 and involves potassium penetrating between clay layers and becoming tightly held. The degree of potassium fixation varies between clay types, with vermiculite showing the highest fixation due to its high charge density and large interlayer space, followed by illite, montmorillonite, and kaolinite. Factors like charge density, interlayer space size, solution concentration, and presence of other cations can influence how much potassium is fixed within clay minerals. The practical implication is that fixed potassium contributes to long-term potassium availability in soils.
The document discusses different groups of clay minerals, including kaolinites, smectites, illites, and chlorites. Kaolinites have a 1:1 layer structure with no interlayer activity or shrink-swell capability. Smectites have a 2:1 layer structure and can expand as water moves between layers. Illites also have a 2:1 layer structure but do not expand, and are common in shales with potassium balancing their negative charge. Chlorites contain an additional brucite interlayer giving them strong bonding between layers.
Explain Langmuir isotherm model and derive its equationZakir Ullah
The document discusses soil chemistry concepts including:
1) Classification of silicate minerals into 1:1 and 2:1 clays based on their structure.
2) Isomorphic substitution in silicate minerals where ions of similar size but different charge replace one another.
3) Calculation of permanent charge in a trioctahedral 2:1 silicate mineral based on isomorphic substitution.
Residual mineral deposits; Laterites; Laterite Profile; Laterisation system; Laterite/Bauxite Conditions; Laterite-type Bauxite, Constitution of Bauxite, Types of deposits; Origin and Mode of formation; Clay (Kaolinite) Deposits; Nickel Laterite Deposits; Mineralogy and Types of lateritic nickel ore deposits; World Nickel Laterite Deposits; Processing of Ni Laterites; Example: Ni-laterites, Ni in soils in east Albania
The document discusses different types of problem soils including acid soils, salt-affected soils, and calcareous soils. It provides details on the distribution and properties of acid soils in India. The major causes of acid soil formation are laterization, podzolization, and leaching in high rainfall areas. Aluminum and iron ions in the soil solution contribute to acidity through hydrolysis reactions. The document also discusses various descriptive terms used to classify soil pH ranges and their associated buffering mechanisms.
This document discusses calcium and magnesium dynamics in soil. Calcium is an important plant nutrient that affects soil physical and chemical properties. Sources of calcium include rocks, minerals, and fertilizers. Calcium availability is influenced by total supply, soil pH, type, cation exchange capacity, percentage saturation, and ratios with other cations. Magnesium is a component of chlorophyll and promotes fat and oil synthesis. Sources include rocks, clays, and fertilizers. Factors affecting magnesium availability include soil type, exchangeable amounts, liming, and ratios with other cations like calcium and potassium. Both calcium and magnesium can be lost from soil through leaching.
Chemistry and physics of submerged soilAnandhan Ctry
This document summarizes submerged soils. It discusses four main types: waterlogged (gley) soils, marsh soils, paddy soils, and subaquatic soils. It describes the characteristics of submerged soils, including the absence of oxygen, chemical changes that occur like reduction, and transformations of carbon, nitrogen, iron, manganese, sulfur, phosphorus, silicon and trace elements. Key points are that submerged soils become anaerobic, chemical elements shift to their reduced forms, and decomposition of organic matter produces gases like methane and hydrogen sulfide.
SUPERGENE ENRICHMENT; Definition; Zones; Morphology of Zoning; Oxidized zone ; Supergene zone ; Gossans and Cappings; Chemical Changes Involved; Electrowinning; Formation of Copper Oxides
Potassium is an essential nutrient for plant growth. It is involved in many important plant processes like photosynthesis, enzyme activation, and water regulation. While total potassium content in soils is usually high, most of it is unavailable to plants. Only a small portion in the forms of exchangeable and water soluble potassium is readily available. Maintaining adequate available potassium levels through fertilization is important for optimal plant growth, yield, quality and stress resistance. Deficiency can cause various symptoms like chlorosis and stunted growth. Proper soil testing and balanced fertilizer management practices are required to supply potassium needs of crops and minimize losses and environmental impacts.
The document discusses clay minerals and their interaction with water. It describes how clay minerals are formed from the weathering of rocks by water. The basic units of clay minerals are silica tetrahedra and octahedral sheets. Clay minerals can have 1:1, 2:1, or 2:1:1 layer structures. Clay particles have negative charges due to isomorphic substitution and broken bonds. Polar water molecules form hydrogen bonds with clay surfaces, becoming tightly bound in monolayers.
This document summarizes the properties and types of soil colloids. It discusses the general properties of soil colloids including their small size, large surface area, surface charges, adsorption of cations and water, cohesion, adhesion, swelling, dispersion, and brownian movement. It describes the four major types of soil colloids - layer silicate clays, iron and aluminum oxide clays, allophane, and humus. Layer silicate clays are further classified into 1:1, 2:1, and 2:1:1 types depending on their crystal structure, with descriptions of common clay minerals in each type.
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1. PRIYA P. GURAV
Scientist
(Soil Science)
ICAR – Central Research Institute for
Dryland Agriculture, Hyderabad
UNIT V
Potassium-forms,equilibriuminsoilsanditsagriculturalsignificance;mechanismof potassiumfixation;
managementof potassiumfertilizerunderfieldcondition
2. POTASSIUM
• It is key plant nutrient in the soil
• It constitutes about 2.5% of the earth crust
Potassiumsources
Common minerals
• Sylvite
• Carnallite
• Kainite
• Langbeinite
• Leonite
• Schoenite
• Polyhalite
Major K- bearing primary minerals
• Feldspars
- Orthoclase
- Sanidine
- Microcline
- Leucite
• Micas
- Muscovite
- Biotite
4. 4
Potassium is known as a yield plus quality nutrient
It is involved in the working of a large number of enzymes
In the production and movement of photosynthesis from leaves to storage organs
Water economy and providing resistance against pests, diseases and stresses
Enhances translocation of sugars and starch
Produces grain rich in starch
Increases protein content of plants
Builds cellulose and reduces lodging
IMPORTANCE OF POTASSIUM
5. • Brown scorching and curling of leaf tips as well as chlorosis
(yellowing) between leaf veins
• Plant growth, root development, and seed and fruit
development are usually reduced in potassium-deficient plants
• Potassium deficiency symptoms first appear on older (lower)
leaves because potassium is a mobile nutrient
• Deficient plants may be more prone to frost damage and
diseases
DEFICIENCY OF POTASSIUM
6.
7.
8. DISTRIBUTION OF K IN SOIL
The readily available K constitutes only 1-2% of total K and exists in soil in
two forms, viz., solution and exchangeable K adsorbed on soil colloidal surface
According to increasing order of plant availability, soil K exists in four forms:
lattice (5000-25000 ppm), non-exchangeable (50-750 ppm), exchangeable (40-
600 ppm) and solution (1-10 ppm).
13. Minerals Minerals Mechanism transformation
Feldspars
Surface reaction and replacement of K + by H3O+
Rupture of Si‐O‐Al bond
Mica
Existence of voids
Change in inter layer spacing
Drying of lattice in presence of CaCO3
Muscovite
(Dioctahedral)
Difficultly rupture of shortened and strengthened
K‐O bond
Biotite
(Trioctahedral) Oxidation of Fe2+ to Fe 3+ during weathering
13
The weathering rate of feldspar is much slower than mica.
Among the micas tri-octahedral mica (biotite) releases sufficient
quantity of K to soil compared to dioctahedral mica (muscovite) even at a low
intensity of weathering. (Fanning and Keramidas, 1977)
MECHANISM OF TRANSFORMATION OF K BEARING
MINERAL
14. Factors affecting availability of potassium
1. Soil texture
2. Clay mineralogy
3. Soil depth
4. Soil pH
5. Liming
6. Freezing and thawing and wetting and
drying
14
16. 16
1. Soil texture(Clay content) & Clay minerals:
- It influences both available and non-exchangeable
potassium
- Fine-textured soils possess large amount of both forms
of K compared t coarse textured soils
- Both the quality and quantity of clay important in K
fixation
- Greater the clay content, greater K fixation
- Clay minerals like illite, weathered mica, vermiculite
and smectite, interstratified minerals fix K, while
kaolinite fixes very little
17. 17
Depth :
- Indian soils show characteristic differences in K content
with depth
- Calcareous alluvial soils show a decrease in both the
available and non-exchangeable forms of K with depth
- Alluvial soils from Indo-Gangetic plains show more
available K in the surface soils while non-exchangeable K
is more in the sub-surface soils
- In shrink-swell (Vertisols/black) soils both available and
reserve K decrease with depth
18. Soil pH (soil reaction)
It has significant role in availability of potassium in
soil
In acid soils, H+ and hydroxy-aluminium ions
compete with K+ ions for the exchange or adsorption
sites and are able to keep more K+ ions in the
solution phase and reduce their susceptibility to
fixation
As the pH increases the H+ and hydroxy-aluminium
ions are neutralized or removed, making it easier for
the K+ ions to move closer to soil colloidal surfaces
where they become susceptible to fixation
19. Liming
Liming of acid soils (with pH-dependent
negative charge) increases the cation
exchange capacity (CEC) of soil which
results in increased K adsorption by the soil
colloids and a decrease in the K level in the
soil solution
The high calcium concentration in the soil
solution phase may reduce K uptake by
plant, especially in soils containing high
amount of CaCO3
20. Freezing and Thawing
Alternate freezing and thawing
may result in increased
exchangeable K in some soils;
however, the reverse may also
happen in illitic soils having high
exchangeable K
21. PotassiumFixation
The phenomenon of K fixation or retention
K availability
21
The important forces involved in interlayer reactions in clays
1. Electrostatic attractions between the negatively charged layers,
2. The positive interlayer ions,
3. Expansive forces due to ion hydration (Kittrick, 1966).
affects
are
and
22. PotassiumFixation
Conversion of freshly applied potassium and / or soil solution potassium to fixed or
non exchangeable forms that can not be extracted with neutral salts is referred to as
K fixation.
It is maximum in 2 : 1 clays particularly with high amounts of illite. The fixation is
nearly absent in soils dominated by kaolinite, chlorite and unweathered micas; slight
in montmorillonite and substantial in illite and high in vermiculite dominated soils.
For the clay minerals like illite, vermiculite and weathered mica three different
adsorption sites can be distinguished. These sites are at the planar surfaces (planar
position), at the edges of layers (e positions) and in interlayer spaces (i positions).
The binding of K+ with organic colloids and kaolinite is at ‘p’ position
which is weak and hence easily replaced by other cations.
22
23. 23
• p – planner surface
• i – interlayer space
• e – edges of layers
24. PotassiumFixation
In smectite rich soils, K+ is held at i position which has the maximum
specificity for K + . When dehydration occurs, the lattice sheets come closer and
the adsorbed cations lose their water molecules
According to ‘Lattice Hole’ theory (Page and Baver, 1940), the exposed surface
and surfaces between sheets of minerals consists of oxygen ions arranged
hexagonally
The opening within the hexagon is equal to the diameter of an oxygen ion
(approximately 2.8 oA)
Ions having a diameter in this magnitude (eg. For K+ it is 2.66 oA) will fit
snugly into the lattice holes and such ions will be held very tightly as they come
in contact with the negative electrical charges within the crystal
However, ions like NH4
+ (dia. 2.86 oA ) has nearly the same ionic radius as the
K+ and is subject to similar fixation by 2 : 1 clays
24
26. 26
PotassiumFixation
The major clay minerals responsible for K fixation
are
Smectite , vermiculite, and weathered micas
Srinivasa Rao et al. 2000
Priya/Ph.D/LRM/Seminar/08-02-13
27. The Potassium fixation
Kaolinite, chlorite and
unweathered mica Vermiculite
Nearly absent Large in
Montmorillonite Illite
Slight substantial
27
Srinivas Rao et al. 2000; Singh et al. 1987; Sharma and Dubey, 1988;
Chakarvorh and Patniak, 1990; Srinivasa Rao and Khera, 1995)
PotassiumFixation in different mineral
Priya/Ph.D/LRM/Seminar/08-02-13
28. The degree of K fixation
Charge
density
Extent of the
interlayer wedge
zone that is
depleted of K
Moisture
content
Solution K
concentration
The nature and
concentration of
competing cations
in the surrounding
medium
(Rich, 1968; Sparks and Huang, 1985,
Brar et al.1986; Subba Rao, A.Sesha Sai,
M.V.R. and Pal, S. K. 1993)
Depends on
28
factors influencingPotassiumFixation
29. K Fixation is high when charge density is high
Vermiculite and illite tend to fix best under relatively wet
conditions while fixation by montmorillonite and the
interstratified clay minerals occur under drier conditions
Ions like H+ can compete with K+ for fixing K or binding
sites
If the wedge zone is confined to the edge of the particle,
then only small amounts of K can be fixed
On the other hand, if the zone penetrates deeply into the
mineral, considerable amount of K can be fixed
Wetting and drying cycles lead to fixation of K in soils rich
in available K
30. Ions like NH4+ and H+ can compete
30
With
K+ for K fixing or binding site
If
The wedge zone is confined
to the edge of the particle
then
only small amounts of K can
be fixed.
The zone penetrates deeply
into the mineral,
considerable amount of K
can be fixed
factors influencing PotassiumFixation
(Brar et al.1986; Subba Rao, A.Sesha Sai, M.V.R. and Pal, S. K. 1993)
31. The fixing power of 2:1 type clay mineral follows
Vermiculite>Illite> Smectite (group in general)
31
The order
factors influencing PotassiumFixation
(Srinivas Rao et al. 2000; Singh et al. 1987; Sharma and Dubey, 1988; Chakarvorh
and Patniak, 1990; Srinivasa Rao and Khera, 1995)
32. The phenomena of both fixation of
exchangeable K and release of non-
exchangeable K play an important role in the
dynamics of soil potassium
The gradual release of K from trapped
positions in the mica lattice to form illite and
eventually vermiculite with concomitant gain
of water and swelling of K lattice is given in
following figure
PotassiumRelease fromSoil Minerals
34. Thereleaseof K frommicasproceedsby
34
The transformation
of K-bearing micas
to expansible 2 : 1
layer silicates by
exchanging the K
With hydrated
cations,
The dissolution of
the micas followed
by the formation
of weathering
products.
(Sparks and Huang, 1985; Sparks, 2000).
Potassium Release from SoilMinerals
35. The low hydration energy of K ion favours its
entrapment
low concentration of K in soil solution due to
leaching or crop removal favours release of K
In the absence of external additions of K, plants are
capable of taking up a very large amount of
potassium without bringing about substantial
decrease in exchangeable K
This means that K which was not initially in
exchangeable form, has changed into exchangeable
form and becomes available to plant.
The 2:1 type of clay minerals are capable of both
fixing and releasing potassium
36. The activity of K+ ions in soil solution around mica particles greatly influences the
release of K from micas by cation exchange.
When the K level is less than the critical value, K is replaced from the interlayer by
other cations from the solution.
On the contrary, when the K level is greater than the critical value, the mica
expansible 2 : 1 mineral takes K from the solution.
The critical K level is highly mineral dependent, being much higher for the
trioctahedral minerals (Scott and Smith, 1967; Newman, 1969; von Reichenbach, 1973;
Henderson et al., 1976).
The critical levels for muscovite are so low that even the K impurities in laboratory
chemicals or dissolved from glassware are often sufficient to prevent any K release
(Scott and Smith,1967).
36
PotassiumRelease fromSoil Minerals
37. Biological activity promotes K release from micas (Mortland et al., 1956; Boyle et al., 1967; Weed et al., 1969;
Sawhney and Voight, 1969).
The organisms deplete the K in the soil solution, and their action may be analogous to that of
tetraphenylboron (TPB) in artificial weathering of micas.
Furthermore, the overall action of organisms is more complex when organic acids are produced
(Boyle et al., 1967; Spyridakis et al., 1967; Sawhney and Voight, 1969).
The importance of organic acids in weathering of rock-forming minerals has been recognized for
a long time (Sprengel, 1826; Bolton, 1882; Huang and Keller, 1970).
The influence of oxalic and citric acids on the dynamics of K release from micas and feldspars
was studied by Song and Huang (1988).
They found that the sequence of K release from K-bearing minerals by oxalic and citric acids is
biotite > microcline > orthoclase > muscovite.
37
PotassiumRelease fromSoil Minerals: biologicalactivity
38. Losses of potassium
1. Luxury Consumption: Some crops tend to absorb K far in
excess of their needs if it is present in sufficiently large quantities
in the soil. This tendency is termed ‘ luxury consumption’ because
the excess K absorbed does not increase crop yields to any
appreciable extent. Wasteful luxury consumption mostly occur in
forage crops
2. Leaching losses of K: leaching losses occur mainly in sandy
soils, organic soils and kaolinite dominant soils.
3. Soil Erosion: it leads to considerable loss of total potassium
from the soil. The erosion losses of K are serious and generally
exceed those of any other major nutrient element.
39. Management of potassium fertilizers under field condition
Determining potassium fertilization need (Soil Test)
Choosing application rates
Types of K fertilizer
Application methods
41. India has no potash-rich soluble minerals and
incrustations (mineral layer)
All K fertilizers is imported
42. Muriate of potash (MOP) is cheaper than sulphate of potash
(SOP) since it is the raw material from which SOP is
manufactured
Crops sensitive to KCL Chloride loving crops
Tobacco, grapes, fruit trees , cotton,
sugarcane, potatoes, tomatoes, straw
berries, cucumber and onions
Oilpalm, and coconuts
Apply SOP as a K fertilizer
Perform well with application
of MOP
• Potassium nitrate is a preferred fertilizer for spraying on fruit
trees and horticultural crops
• Recent studies shown that schoenite (double salt of potassium
and magnesium) is as good source of K as MOP for groundnut,
banaba, rice, wheat and maize
43. Indigenous sources of
potassium
Wood ash
Manure
Crop residue
Distillery and coir industry waste
Cement kiln dust
Etc.
Assignment: Different sources of K and their K content (minerals, fertilizers
Organic and other
44. Methods of potassium application
Broadcasting and mixing with surface soil
Band placement is recommended in soils with low available K
and high K fixing capacity
In some crop situations split application is emerging as an
alternative to basal application
E.g i) rice grown in light textured soils and acid soils in high
rainfall areas in order to reduce leaching losses
Ii) low tillering and late maturing varieties, where the natural
supply of K from soil plus irrigation water decreases in the later
stages of crop growth
Iii) in highly reduced soils where conditions may hinder K
uptake
Iv) during the monsoon season