DESCRIPTION OF COURSES

Close

SSAC 504 SOIL CHEMISTRY                                                                               (4L+1P) I

Objective
To impart basic knowledge on fundamentals of soil chemistry and chemistry of the soil, clay mineralogy, ionic equilibria, chemical processes and mechanisms of the soil constituents in relation to basic soil functions

Theory

UNIT I
Chemical composition of earth crust, soils, rocks and minerals.

UNIT II
Chemical bonding, chemical equilibria, chemical kinetics and thermodynamics.

UNIT III
Pauling’s rule, silicate structure, crystalline oxides and amorphous materials; XRD analysis, stability and weathering of minerals; clay mineral transformation and synthesis.

UNIT IV
Soil colloids: Inorganic and organic colloids - origin of charge, concept of point of zero-charge (PZC) and its dependence on variable-change soil components, surface charge characteristics of soils; diffuse double layer theories of soil colloids, zeta potential, stability, coagulation/flocculation and peptization of soil colloids; electrometric properties of soil colloids; sorption properties of soil colloids.

UNIT V
Ion exchange processes in soil; cation exchange - theories based on law of mass action (Kerr- Vanselow, Gapon equations, hysteresis, Jenny’s concept), adsorption isotherms, Donnan-membrane equilibrium concept, clay-membrane electrodes and ionic activity measurement; anion and ligand exchange - inner-sphere and outer-sphere surface complex formation, fixation of oxyanions, hysteresis in sorption-desorption of oxy-anions and anions, shift of PZC on ligand exchange, AEC, CEC; soil solution; potassium dynamics, quantity-intensity relationships.

UNIT VI
Soil acidity - formation and properties of acid and acid sulphate soils; salt-affected soils - formation and properties.

UNIT VII
Organic matter – extraction, fractionation and characterization; interaction of organic matter with clay minerals and metals ions.

UNIT VIII
Phosphate chemistry in soil; geochemistry of micronutrients; chemical speciation; chemistry of waterlogged soils; environmental soil chemistry.

Practicals
Preparation of saturation extract; measurement of EC, pH, CO3, HCO3, Ca, Mg, K and Na concentration in saturation extract; calculation of minimum radius ratio of polyhedra and making models of silicate structure; quantity-intensity relationships of potassium in soil; extraction of humic substances; determination of lime potential and phosphate potential, zero-point charge of soil and redox-potential of submerged soils; calcium–potassium exchange equilibria in soil.

Suggested Readings