Chapter 4 Flashcards
Adsorbed cations are also known as ____.
exchangeable cations
What is the charge of agriculturally important soils?
negative charge
The process whereby cations adsorbed on the surface of soil colloids is exchanged for those in the soil solution or in any medium that comes in contact with the soil colloids.
Cation exchange
If nutrients are not absorbed by soil colloids, they are subject to what.
Loss through leaching
Na-rich soils are in what state?
dispersed
The element that is responsible in dispersing soil.
Na
Ca-rich soils make the soil to be?
flocculated
Element responsible in making flocculated soil
Ca
Is dispersion a desirable characteristic of productive soil?
NOT desirable
The CEC of permanent charge clays.
low CEC
The buffering capacity of permanent charge clays?
low buffering capacity
Accompanying ions
complementary ions
What will happen to the ion of interest if the complementary ion is strongly adsorbed?
easily released
The quantitative measure of the ability of soil to adsorb and exchange cations with those in the surrounding solution and with plant roots.
cation exchange capacity
The sum of the negative charges of the soil.
cation exchange capacity
The sum total of the exchangeable cations that a soil can adsorb.
cation exchange capacity
The easily exchangeable cations.
electrostatically retained cations
The cations that are readily available for plant uptake.
electrostatically retained cations
The dissociation of H from OH- groups
deprotonation
What will happen to the charge if there is deprotonation?
additional negative charge
What is the CEC of OM?
100-300 cmolc/kg soil
Tells us the degree to which the exchange sites are occupied by basic cations.
percentage base saturation
Give examples of basic cations.
K
Ca
Mg
Na
Give examples of acidic cations.
Al
H
The atomic weight of Ca.
40 g/mol
The atomic weight of Na.
23g/mol
The atomic weight of K?
39g/mol
The atomic weight of Mg.
24g/mol
What will happen to the cations if there is high percentage cation saturation?
easily and rapidly released
Enumerate the practical applications of CEC.
plant nutrition
liming
amelioration of Na affected soil
environmental quality
Enumerate the soil properties that determine CEC.
soil texture
organic matter content
nature of clay colloid
pH
percentage base saturation
Enumerate the methods of determining CEC.
CEC determination at pH7 ammonium acetate:1N
calculation of effective CEC
CC determination using BaCl2
Enumerate the soil processes that affect cation exchange.
weathering
nutrient retention
dispersion and flocculation
buffering pH change
The characteristics of cation exchange reactions
ER are stoichiometric and take place in equivalent amounts
CE are instantaneous
ER are reversible
Factors affecting the extent of cation exchange.
- Relative adsorbability of the cation on soil colloid or the relative replacing the power of the cation
- Concentration of the solution
- Nature of exchange materials
- Geometric fit of ions into the mineral structure
- Influence of complementary ions
Between Kaolinite and Illite which has a rapid cation exchange?
Kaolinite
Between kaolinite and illite which takes longer time?
illite
High level of Ca is antagonistic to?
inhibit K
High K would lead to
interfere Mg
ESP stands for
Exchangeable Sodium Percentage
Soils with high amounts of soluble sodium
Sodic soils
