.- Soil Chemistry
PROF. GIAN PIETRO MOLINARI
COURSE AIMS
Students will acquire the fundamental ideas relating to the genesis and
classification of soils, and to the chemistry of the organic and inorganic soil
components and their interaction in the soil-plant system, and plant nutrients and
the use of fertilisers.
COURSE CONTENT
CFU
Soil and plant System
Principal components of the earth's crust. Rocks: classification, genesis
and disaggregation and decomposition processes. . Profile and its surface
and subsurface diagnostic horizons. Factors influencing profile
differentiation. Pedogenesis: factors of pedogenesis and Jenny equation.
The chemistry of silicon
Thermodynamic considerations relating to the Si-O bond energy and bond
length. Classification of silicates. Primary and secondary phyllosilicates.
Stability of minerals: disaggregation and decomposition processes.
Clays
Structure, types. layer charge and its distribution. Genesis of clays.
Relationship between climate and the type of clay. Chemical properties of
the soil, the colloidal state, electrical charge, specific surface area and
surface charge density..
Soil Classification Systems
The FAO-UNESCO Soil Units; The Soil Taxonomy: Order, Suborders,
Great Group, Subgroup, Family and Series. Dimensional distribution of
the mineral fraction of the soil. Particle size and real texture and apparent
texture. Stock's Law.
Structure of soils. Primary and secondary aggregates. macropores,
micropores and ultramicropores. Bonds between colloidal particles for the
formation of aggregates. Factors influencing the dynamics of the
structure: intrinsic and extrinsic. Morphology of the structure. Agronomic
relevance of the structure and influence of agricultural practices.
Organic matter
Classification and characterisation of organic matter. Humic substances:
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chemical structure, genesis, characterization. and role.
Adsorption and cation exchange
Physical models of adsorption and exchange reactions. Effect of valence,
dilution and concentration on cation adsorption. Asymmetry of cation
exchange equilibrium and selectivity. Organic cations.
Anion adsorption: specific and non-specific. Ligand exchange mechanism
and kinetics of phosphate adsorption. Negative and positive adsorption as
the basis of interactions between soil colloids and organic compounds.
Freundlich isotherms.
Fluid phases of soil
The soil water. Reaction: acid and alkaline soils, pH and its measurement,
base saturation. Effects of acidification and alkalinisation on agricultural
productions. Management and correction of acid and alkaline soils.
Redox potential of soils and composition of the telluric air. Irrigation
water and quality parameters.
Elements of fertility
Principal and secondary elements of fertility and microelements.
Dynamics of phosphorus in soil. Phosphate retrogradation. Variations in
the availability of phosphates with pH.
Dynamics of nitrogen in soil-plant System. Mechanisms of fixation,
nitrification and denitrification. Soil mobility of nitrogen chemical forms.
Dynamics of potassium, sulphur, calcium and carbonates in soil.
Fertilizing
Fertilizers: classification and composition.
Nitrogenous fertilizers: classification, physical properties and selection
criteria. Slow release nitrogenous fertilizers and nitrification inhibitors.
Classification, physical properties and selection criteria of Phosphate and
Potassic fertilizers.
Educational visits and laboratory work
Pedologic excursion and natural profile examination
Descriptions, with help of slides, of: pedosphere, units and soil profiles.
Application of the interpretations of Soil Taxonomy and WRB-World
Reference Base.
Laboratory Measure of: soil pH, total calcium and carbonates. Correction
of acidic and saline soils.
Hand estimation of texture. Soil color: use of Munsell’s table. Particle
size analysis and textural classes.
Analysis of results and fertilization plans..
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READING LIST
Course textbooks
P. SEQUI, Fondamenti di Chimica del suolo, Patron Editore, Bologna, 2005.
P. VIOLANTE, Chimica del Suolo e della Nutrizione delle Piante, Edagricole, Bologna, 2002.
Recommended reading
P. SEQUI, Chimica del suolo, Patron Editore, Bologna, 1989.
M.E. ESSINGTON, Soil and Water Chemistry: An Integrative Approach, CRC Press, Boca Raton,
2004.
M.E. SUMMER, Handbook of Soil Science, CRC Press, Boca Raton, 2000.
P. VIOLANTE, Metodi di Analisi Chimica del Suolo, Franco Angeli Editore, 2000.
F.E. BEAR, Chemistry of the soil, Reinhold Publishing Corporation, New York, 1964.
http://www.agrolinker.com/italiano/argomenti/agronomia/agronomita31.html, Chimica del
terreno e fertilizzazione del suolo agrario.
TEACHING METHOD
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The course consists of:
Lectures.
Tutorial exercises
Guided laboratory work.
Field trips to examine soil profiles.
ASSESSMENT METHOD
There will be an oral examination at the end of the course.
NOTES
The course will include tutorials and practical laboratory work on: pedogenesis and
classification of soils; principal chemical and physical determinations of soils.
Prof. Gian Pietro Molinari is available to meet with students after class at the Institute of
Agricultural and Environmental Chemistry.