Introduction TO SOIL Science Notes (AGS 211)-2010 PDF

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INTRODUCTION TO SOIL SCIENCE AGS 211

LECTURE NOTES

Revised in January 2014 Department of Agronomy Faculty of Science and Agriculture University of Fort Hare, Alice 5700 South Africa

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LEARNING GUIDE

1. UNIVERSITY OF FORT HARE Faculty of Science and Agriculture

Department of Agronomy AGS 211 – Introduction to Soil Science

LEARNING GUIDE 2015

Lecturers: Mr. H.A. Mupambwa & Dr. J.J. van Tol

Mr. H.A. Mupambwa Office: Agriculture building Room AGS 19. Phone: Email: [email protected]

Dr. J.J. van Tol (Coordinator) Office: Agriculture building Room AGS 10. Phone: 040 602 2290 Email: [email protected]

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Consultation times: Learners are encouraged to make maximum use of practical sessions for general consultations. However, they are welcome to visit me in my office anytime during working hours whenever the lecturer concerned is available.

Teaching Style: A combination of instructor- and student centered approaches are used. The subject content will be presented to the students following the traditional lecture approach using either overhead projectors or power point presentation. The lectures will be supplemented by lecture notes but students are expected to complement the knowledge so provided through independent studies encouraged through regular assignments to be handed in at specified times. The course has a laboratory component that is designed to integrate lecture subject materials and provide the student the opportunity to acquire practical skills in soil and plant analysis as well as diagnosis of plant nutrient deficiency symptoms.

Tutors: Each student will be allocated a Tutorial Group led by a Tutor who will provide extra tuition to students during scheduled times. Tutors will also assist in the Practical Classes.

Academic Honesty: All incidents of academic dishonesty such as plagiarism or cheating in tests and examinations are serious offences which will not be tolerated. Culprits will be reported to the University disciplinary committee.

General: 

Problems:

If you experience problems that affect your well-being and academic

performance you should seek help in good time from the Counseling Unit, The Faculty Manager or me. 

Student with disability: If you have a disability that requires special accommodation, please let me know so we can determine how best to assist you.



Balance: Manage your time such that you can participate in sporting, spiritual, and social activities in addition to your academic work. If you do so, you will enjoy your student life and achieve your academic objectives at the same time.

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MODULE OUTLINE Module Title: Introduction to Soil Science Module Code: AGS 211 NQF Level: 5 Credit Value: 16 Place in Programme: Core module in all curricula of Programme in Integrated Agronomic Sciences Core module in all curricula of Programme in Agricultural Economics, Extension and Rural Development Core module in all curricula of Programme in Science of Free Ranging Animals Date Approved by Faculty Board: Date of Review by Faculty Board: Purpose of the Module: To introduce learners to the subject of Soil Science by giving them a general background to the origins of soils, their formation and classification, their physical, chemical and biological properties, as well as soil fertility and its management.

Learning Outcomes and Associated Assessment Criteria: Learning Outcome 1: 

Demonstrate a general understanding of the subject of Soil Science.

Assessment Criteria: 

Different components of Soil Science are listed and explained.



Their significance and interrelationships in agricultural and environmental sciences are understood and explained.

Learning Outcome 2: 

Demonstrate a comprehensive understanding of the fundamental principles in the various disciplines of the subject.

Assessment Criteria: 

The origins of soils, their formation and classification are explained.



The distinction is made between physical, chemical and biological properties.



The functions of soils in the ecosystem are satisfactorily explained.



The link between soil fertility and plant growth and development is made.



The role of organic and inorganic fertilizers in soil fertility and its management is explained

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Content Outline: 

Introduction (definitions, composition and functions of soil)



Origin of soil



Soil formation and development (factors, processes and profiles)



Soil classification and mapping



Physical properties



Chemical Composition of Soils



Development of charges in soils



Flocculation and Dispersion



Soil Reaction



Liming



Salt Affected Soils



Soil Organisms



Soil Organic Matter



Mineralization, Ammonification and Nitrification



Soil Fertility Indicators



Types and Sources of N P K – Fertilizers



Fertilizer Mixtures



Principles of Fertilizer Recommendations



Fertilizer Placement Methods

Teaching-Learning Methods: 

Lectures – to give learners theoretical concepts and factual knowledge of the subject



Practicals – for experience in analyzing and describing soil properties and/or characteristics



Assignments –development of critical thinking and communication skills



Tutorials-to reinforce interpretive and independent thinking skills

Assessment Methods: 1. Continuous assessment through o

Practical reports

15%

o

Tests (at least two)

35%

2. Final examination (3 h)

50%

Please Note:

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(i) With a semester mark of 40% or less, you will not be allowed to write the final examination (check the rules for 2010). (ii) With less than 80% of attendance of practical exercises, you are not allowed to write the final examination. iii) Late

submissions for practicals won’t be accepted!

iv) The sick test can only be written by students who missed test 1&2

AND

produced valid medical certificate within 48 hours.

Compulsory Readings: The Nature and Properties of Soils by R.R. Weil and N.C. Brady (2002) 13 th Edition, Kluwer Academic Publishers, The Netherlands.

Reference Book: Fertilizer Handbook 2007. Published by the Fertilizer Society of South Africa (FSSA), Lynnwood Ridge, South Africa.

Additional Readings: A list of relevant literature is available in the library.

Lecture schedule and important dates

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Week

Theme

1 2 3 4 5 6 7 8

Introduction, Definition, composition, minerals Soil forming factors Soil forming processes Soil Classification Soil physics Soil physics Introduction to chemistry Soil colloids - nature and significance

Vacation 9 10 11 12 13 14

Charges, CEC and pH Charges, CEC and pH Soil biology Soil organic matter Soil analysis Review

Important dates th

Test 1 Test 2 Sick Test

10 March 21th April 12th May

Practical 1 Practical 2 Practical 3 Practical 4 Practical 5 Practical 6 Practical 7

Due dates for practicals – NB! No late submissions 3rd March 10th March TBA TBA TBA TBA TBA

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1. I nt r oduct i on Soil is the upper layer of the earth’s crust which developed gradually through the combined action of soil-forming processes. The parent material from which a soil developed can either be: (i) the underlying rock, (ii) river or aeolian (wind) depositions, or (iii) volcanic ash. It is a multicomponent open system containing solids, liquids and gases.

In any ecosystem (back yard, farm, forest or regional water shed) soils play five key roles:

1. Soil supports the growth of higher plants mainly by providing a medium for plant roots and supplying nutrient elements that are essential to the entire plant.

2. Soil properties are the principal factor controlling the fate of water in the hydrologic system. Water loss, utilization, contamination and purification are all affected by soil.

3. Soil functions as nature’s recycling system. Within the soil waste products and dead bodies of plants and animals are assimilated and their basic elements are made available for reuse by the next generation of life.

4. Soil provides habitats for a myriad of living organisms (from small mammals and reptiles to tiny insects and microscopic cells).

5. Soil plays a role in human – built ecosystems as an Engineering medium. (Building materials e.g. bricks provides foundation for roads and all types of buildings).

SIGNIFICANCE OF SOIL AND ITS STUDY 1. Basically, all life depends on soil, often synonymous with "dirt," and is perhaps the most undervalued of all natural resources. a. All human food is obtained from crops grown on soil. b. All livestock and herbivores graze on grasses and other plants that grow in soil. c. Most fibers used in clothing, such as flax and cotton, are grown in soil. d. Building materials, such as brick, adobe, aluminum, and glass come from soil materials. e. Timber used for construction and furnishings are grown in soil.

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In 1985, it was estimated that the world's population will require twice as much food by year 2020, and the ability to meet this demand ultimately rests with soils on continental land masses. 2. Soil serves as the intermediary property that links living ecosystems with inanimate materials, i.e. rocks and minerals. This link would therefore suggest that soil must be a "highly organized, physical, chemical and biological complex on which all of us depend." 3. Note the relationship between soil and its central location in the entire biotic complex: a. Climate breaks down rocks, creating soil, and influences physical and chemical properties of soil. b. Humans alter the fertility and quality of soil. c. The type and abundance of plant material greatly affects the type of soil and its physical and chemical properties. d. Animals sometimes control the type and abundance of plants which in turn affect the type of soil and its properties, while soil itself can influence the distribution of animals. 4. The study of soils is called pedology, which investigates the appearance, the mode of formation, the distribution, and classification of soils. It is an integrative science, much like geography. Pedology borrows upon concepts developed from: (1) agriculture, (2) forestry, (3) history, (4) geology, (5) geography, (6) and archaeology. 5. It is important to realize that, like geography, pedology can be either a pure science, which seeks to gain knowledge about soils (processes, formation, distribution, and classification), or an applied science, which then takes this information and is used to further our knowledge in such fields as horticulture, forestry, engineering, agriculture, etc. 6. The overall goal, as in any applied science, is to gain knowledge to better prepare and manage for the future - we are constantly trying to improve our living conditions on our planet. Unfortunately, soil science has lagged behind in its application, mainly because of the complexity of soils, as well as the political, social, financial, and legal problems encountered. 7. Soil as an ecological science: Ecology is the study of interactions between organisms and the environments in which they live. Notice the effects of scale - soil is both an ecosystem unto itself as well as a portion of a larger ecosystem. On a finer scale, soils support organisms within itself, from microbes to invertebrates to small mammals, i.e., soil provides the ecosystem. On a larger scale, soils support organisms onto itself, such as plants to trees to humans, i.e., soil is part of the ecosystem.

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DEFINITIONS OF SOIL

a. A particular three-dimensionally structured, unconsolidated body of mineral and/or organic material occurring naturally within the landscape at the surface of the earth capable of supporting plant growth. b. Natural bodies of animal, mineral, and organic constituents differentiated into horizons of variable depth which differ form the material below in morphology, physical make-up, chemical properties, composition, and biological characteristics. c. Soils are porous natural bodies composed of inorganic and organic matter. They form by interaction of the earth's crust with atmospheric and biological influences. They are dynamic bodies having properties that reflect the integrated effects of climate (atmosphere) and biotic activity (microorganisms, insects, worms, burrowing animals, plants, etc.) on the unconsolidated remnants of rock at the earth's surface (parent material). These effects are modified by the topography of the landscape and of course continue to take place with the passage of time. The latter definition introduces the concept that soil is loosely layered into horizons, layers differentiated based on color, composition, structure, and depth.

COMPOSITION OF SOILS

1.

Soil consists of four main constituents: (1) mineral matter, (2) organic matter, (3) air, and (4) water.

The composition of soil.

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2.

Mineral matter consists of two groups: (1) primary minerals, resistant coarse-grained minerals weathered from rocks, and (2) secondary minerals, formed in the soil by recombination of substances, usually fine-grained.

3.

Organic matter is derived mostly from decaying plant matter, but also consists of decaying animal matter. Organic matter composed of cellulose, starch, and lignin in various states of decomposition.

4.

In soils that have structure, the mineral and organic components are aggregated into discrete structural units called peds, which are surrounded by open spaces.

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Air and water occupy these spaces. In soils that are saturated, most air is removed. In freely drained soils, water adheres to the mineral particles.

MINERAL MATTER The mineral portion comes primarily from in situ weathering of the geological substrate. Occasionally, however, minerals are transported in, as well as blown in from aeolian wind activity. 1.

Particles range in size from very small clay particles measured in microns up to sand-size particles that can be measured in millimeters. This fraction of the soil is called fine earth, and usually consists of particles less than 2 mm in size. It is upon this fraction that soil texture is determined.

2.

The fine earth fraction can be further broken down into three classes: a. sand: diameters between 0.05 to 2.0 mm b. silt: diameters between 0.05 to 0.002 mm c. clay: diameters less than 0.002 mm

Classification of minerals Minerals are naturally occurring inorganic substances, which possess a definite chemical composition and exhibit more or less definite physical properties such as colour, hardness,

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specific gravity, solubility and crystalline shape by which it my be identified.

Minerals are

classified as primary or secondary.

a.

Primary minerals

A primary mineral is one that has not been altered chemically since it was crystallized from molten lava.

Examples of primary minerals (Source: Harry, 1992) Family/Group Silica Feldspars

Mineral Quartz Orthoclase

Formula SiO2 K2O.Al2O3.6SiO2

Plagioclase Albite

Na2O.Al2O3.6SiO2

Micas

Anorthite Muscovite (white mica)

CaO.Al2O3.2SiO2 KAl2(AlSi3O10)(OH) 2

Metasillicates

Biotite (black mica) Horneblende (amphibole

K(Mg, Fe) 3(AlSi3O10)(OH) 2 Variable composition

group)

Variable composition

Apatite

Augite (pyroxene group) Apatite

[Ca3 (PO4) 2] 3.Ca[CO3,Cl2,F2,(OH) 2]

Olivine

Olivine

Variable composition (Mg, Fe)2SiO4 Variable composition

b.

Secondary minerals

A secondary mineral is formed from a primary mineral, by decomposition of the primary mineral or from precipitation of the decomposition products resulting from the decomposition of the primary mineral. Or simply, can be defined as minerals formed from rocks by processes of weathering and re-crystallization. Important rocks forming minerals in this group includes the carbonates and iron ores.

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Examples of secondary minerals (Source: Harry, 1992) Family/Group Carbonates

Mineral Calcite

Formula CaCO3

Sulphates Iron ores

Dolomite Gypsum Hematite

(Ca, Mg)CO3 CaSO4.2H2O Fe2O3

Magnetite

(Fe, Mg)Fe2O3

Aluminium ores

Goethite Gibbsite

FeO(OH) Al(OH)3

Boehmite 1:1 layer silicates

AlO(OH)

Phyllosillicates

Kaolinite

Al2Si2O5(OH)4

Halloysite

Al2Si2O5(OH)4

2:1 layer silicates Montmorillonite Micaceous clay minerals Micas Vermiculite Hydrous magnesium silicates Talc Serpentine

Mg3(Si4O10)(OH)2 Mg6(Si4O10)(OH)8

Identification of minerals The following physical properties of minerals can be used for their identification; a)

Colour: minerals have characteristic colours and are variations due to impurities and this makes difficult to identify minerals from colour alone.

b)

Streak: the colour of a streak left by a coloured mineral on an unglazed white porcelain surface when the mineral is rubbed against it.

c)

Lustre: The luster or reflection of light from the surface of a mineral. Minerals may be metallic or non-metallic.

d)

Hardness: The resistance that a smooth surface of a mineral offers to scratching. Normally classified using the mohs scale (1 – 10). The softest (easy to scratch) mineral is talc (mohs = 1) and diamond is the hardest mineral (mohs = 10).

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e)

Cleavage: is the property of yielding definite plane surfaces when a force is applied on the mineral.

f)

Density/specific gravity: Density relative to the density of water. Minerals have characteristic specific gravities.

g)

Crystal system: Minerals have characteristic crystalline structure (e.g. cubic, hexagonal, etc.)

Important soil minerals (Source: Bullock & Hopkins, 1984) Minerals making up igneous

Importance to soil

rocks Quartz

The most abundant soil mineral but does not contribute significantly

Feldspars

to soil fertility. Form clay minerals Orthoclase feldspars are a source of potassium

Micas

Plagioclase feldspars are source of sodium and calcium Add potassium and magnesium and transform into other clay

Ferro-magnesium minerals

minerals. They occur as amphiboles and pyroxenes. The breakdown of thes...