Lecturers:
Prof M McGowan
Mr P Nyamugafata
Course Outline
Soil Mechanics
Shear strength of soils
Coulomb's law
Elasticity theory
Critical state soil mechanics
Applications of soil mechanics
slop stability
bearing capacity of soils
Soil compression
soil compaction
soil consolidation
Mechanics of root growth in soils
Soil temperature
thermal properties of soil constituents
mechanisms of heat flow in soils
Fourier's equation
Soil aeration
air capacity of soils
gaseous exchange between soil and atmosphere
movement of gases in soils (diffusion -- Fick's law)
measurement of soil aeration
Advanced topics in soil water movement
groundwater drainage
bypass flow
solute transport
SOIL CHEMISTRY SECTION OUTLINE 1996
[Lecturer: E M Govere, Dept of Soil Science & Agric. Eng.]
TOPIC: METHODS OP EXPRESSING CONCENTRATIONS
Objectives:
1. Express
concentrations on weight per volume basis and on weight per weight basis
2. Calculate equivalent weights, normal and mole concentration of solutions.
3. Convert
concentrations from milliequivalents per 100 g (meq/100g) to centimoles
(charge) per
kilogram (cmol,kg '), from ppm to lbs/A to kg ha '.
Content:
1. Equivalent weight
based on charge of an ion
2. Equivalent weight based on Acid-Base Reactions
3. Equivalent weight based on Oxidation-Reduction Reactions
4. Converting meq/100g to cmolckg-1,mg kg-1, 1bs/A, kg ha-1, ppm.
TOPIC: SOIL WEATHERING
Objectives:
1. Define soil and
soil formation
2. List seven soil forming (environmental) factors
3. Know the meaning of letter and diagnostic horizons
4. Group pedogenic processes into those involved in:
6. Explain the factors affecting parent material mineral weatherability
7. Rank soil minerals based on weatherability.
Content:
1. Soil forming factors
2. Horizonation
3. Physical, biological and chemical weathering
4. Factors affecting parent material mineral weatherability.
TOPIC: SOIL MINERALS
Objectives:
1. Define soil mineral
2. List common soil mineral groups and examples of soil minerals belonging to the groups/classes
3. Classify the minerals into primary, secondary, silicate and non-silicate minerals
4. Classify and illustrate silicate minerals based on arrangement of silica tetrahedra
5. Distinguish between 1:1, 2:1, and 2:1:1 crystal structures and minerals
6. Discuss the effect of layer charge on physical and chemical properties of phyllosilicate minerals
7. Describe methods of mineral identification
Content:
1. Primary minerals
2. Secondary minerals
3. Non-silicate minerals
4. Silicate minerals (phyllosilicates)
5. Classification of silicate minerals
6. Effect of layer charge on physical and chemical properties of silicate minerals
7. Identification of minerals.
TOPIC: SOIL ORGANIC MATTER
Objectives:
1. Define soil organic
matter (OM) and humus
2. Rank the effect of soil forming factors on OM
3. Sketch the Jenkinson's soil organic matter decomposition model
4. List common organic acids in soil
5. Explain decomposition of OM
6. Compare the colloidal properties of O.M. with those of layer silicate minerals
7. Know sources of negative and positive charges on humus
8. Discuss the effect of O.M. on soil productivity and environmental management
9. State some of the negative effects of OM
10. Describe methods of determining O.M.
Content:
1. Effect of soil forming
factors on OM
2. Jenkinson's soil organic matter decomposition model
3. Common organic acids in soil
4. Decomposition of OM
5. Comparison of colloidal properties of O.M. with those of layer silicate minerals
6. Sources of negative and positive charges on humus
7. Effect of O.M. on soil productivity and environmental management
8. Negative effects of OM
9. Methods of determining OM.
TOPIC: SOIL ACIDITY
Objectives:
1. Define pH, Kw
2. Describe types and sources of soil acidity
3. Write soil acid forming reactions
4. Understand the effect of soil acidity on soil productivity and environmental management
5. Measure pH and exchangeable acidity of soils.
Content:
1. Types and sources of
soil acidity
2. Soil acid forming reactions
3. Effect of soil acidity on soil productivity and environmental management
4. Matrix and suspension effects
5. pH and solubilities of chemical species in soil
6. pH measurements methods.
TOPIC: LIME REQUIREMENT
Objectives:
1. Define lime requirement
(LR) and lime potential
2. Know common Agriculture Lime materials
3. Know reasons for liming
4. Write chemical reactions for how given liming materials neutralize an acid soil
5. Know factors affecting effectiveness of lime
6. Compute CaCO,
equivalents (CCE) and Effective CaCO, equivalents (ECCE) given molecular
weights and fineness factor of liming material.
7. Compute amount of a
given liming material (e.g. 80- CCE) required to neutralize acidity formed
by aluminum hydrolysis or nitrification process.
8. Describe methods of determining LR.
Content:
1. Definition of lime
requirement (LR)
2. Common Agriculture Lime
materials
3. Reasons for liming
4. Chemical reactions for how given liming materials neutralize an acid soil
5. Factors affecting effectiveness of lime.
6. CaCO, equivalents (CCE)
and Effective CaCO, equivalents (ECCE) given molecular weights and
fineness factor of liming material
7. LR methods.
TOPIC: CATION EXCHANGE
Objectives:
1. Describe the nature
and sources of charge in soil
2. Explain the factors
that control the attraction and bonding between cations and soil negative
charge sites
3. Relate objectives 1 and 2 to crop production and environmental management
4. Describe methods for measuring exchangeable cations.
Content:
1. Nature and sources
of charge in soil
2. Factors that control the attraction and bonding between cations and soil negative charge sites
3. ECE as related to crop production and environmental management.
4. Methods for cation measurement.
TOPIC: ANION ADSORPTION
Objectives:
1. Know important anions
in the soil solution
2. Differentiate between specific and non-specific anion adsorption
3. List the factors affecting negative adsorption of anions
4. Explain phosphate adsorption in soils
5. Know adsorption mechanisms
for protonating, deprotonating molecules, non protonating and non
deprotonating molecules
6. Explain three adsorption
equations commonly used to describe adsorption data (adsorption
isotherms)
7. Relate anion adsorption mechanisms to soil productivity and environmental management
8. Describe methods for determining anions.
Content:
1. Specific and non-specific
anion adsorption
2. Factors affecting negative adsorption of anions
3. Phosphate adsorption in soils
4. Adsorption mechanisms
for protonating, deprotonating molecules, non-protonating and
non-deprotonating molecules
5. Adsorption equations commonly used to describe adsorption data (adsorption isotherms)
6. Anion adsorption mechanisms to soil productivity and environmental management
7. Methods for anion measurement.
TOPIC: OXIDATION AND REDVCTION
Obiectives:
1. Define
oxidation, reduction, electrode potential, redox potential and pe+pH
2. Know major electron donors and acceptors in soil and their half reactions
3. Given thermodynamic
data redox species such as 5G§, 6H§ and a,s§,
(a) Compute equilibrium constants for given redox reactions.
(b) Compute Eh and Eh§
(c) Compute pe+pH
4. Relate redox reactions
to
(a) weathering and decomposition of OM
(b) Soil acidity (acid sulfate soils)
(c) Nutrient availability and toxicity
5. Know how to measure (Flooded soils) Electrode or redox potentials.
Content:
1. Definitions of oxidation,
reduction, electrode potential, redox potential and pe+pH
2. Major electron donors and acceptors in soil and their half reactions
3. Equilibrium constants for given redox reactions
4. Eh and Eh§
5. pe+pH
6. Redox reactions and
(a) weathering and decomposition of OM
(b) Soil acidity (acid sulfate soils)
(c) Nutrient availability and toxicity
7. Measurement of (Flooded soils) Electrode or redox potentials.
TOPIC: ENVIRONMENTAL CHEMISTRY
Objectives:
1. Describe reactions
and mobility of selected agri-inputs
2. Explain the processes
of environmental degradation
(a) Soil chemical degradation
(b) Soil physical degradation
(c) Soil fertility degradation
(d) Soil biological degradation
3. Detect pollution in soil.
Content:
1. Reactions and mobility
of selected agri-inputs
2. Processes of environmental
degradation
(a) Soil chemical degradation
(b) Soil physical degradation
(c) Soil fertility degradation
(d) Soil biological degradation
3. Methods for determining heavy metals in soil.
AREAS OF EMPHASIS FOR ADVANCED SOIL CHEMISTRY
The main objective of the course is to reinforce some soil chemistry concepts and skills to prepare the student for the world of work. At least, the student should be able to run a soil chemistry lab or run a soil chemistry research program after this course. It is hoped that by the end of the course, the student will be familiar with soil analytical instruments and understand the theory behind selected chemical analyses. The student will be able to relate the soil chemistry concepts in terms of their applicability to real life situations.
UNITS OF CONCENTRATION
Computation of selected units of concentration
CHEMICAL INSTRUMENTATION
Comparison of selected soil chemistry analytical
instruments
CHEMICAL SOIL WEATHERING
Chemical factors and processes that affect weatherability
of minerals in soil
SOIL ACIDITY
Matrix and suspension effects
Effect of pH on Solubilities
SOIL SALINITY AND SODICITY
Selected computations used to classify salt affected
soils
LIME REQUIREMENT
Selected computations to determination
of purity and value of
liming materials
SOIL MINERALOGY
Selected computations related to the theory
of clay mineral
analysis: Bragg's Law and Scherrer's equations
CATION RETENTION
Factors that influence cation retention in soil
ANION ADSORPTION
Selected adsorption equations and their applications
ENVIRONMENTAL CHEMISTRY
Reaction and mobility of selected agricultural
inputs
Other Menus:
Agricultural
Economics
Agriculture
Engineering
Animal
Science
Crop
Sciences