Module 2 Support pack for Soil science GR 11

Study & Master Support Pack | Grade 11 CAPS Module 2 Units 1 – 10 Agricultural Sciences Soil science This support pack for the Soil science module in the Agricultural Sciences Grade 10 CAPS curriculum provides valuable revision activities. All activities have the answers provided. Learners can work through these individually at home or these could form the basis of a catch-up class or online lesson. You have permission to print or photocopy this document or distribute it electronically via email or WhatsApp. For more information on our Study & Master CAPS-approved  textbooks and valuable resource materials, visit www.cambridge.org Brighter Thinking | Better Learning

Module 2 – Soil science Unit 1 Soil texture Short questions 1. Various possible answers are provided for the following questions. Write only the correct letter (A–D) next to the question number. 1.1 Farmers typically view soil as: A something to be cleared from a site B a valuable resource C something which can be bagged and sold D nothing really special 1.2 Engineers typically view soil as: A something to be cleared from a site B a valuable resource C something which can be bagged and sold D nothing really special 1.3 The parent material of most soils is: A sand B silt C clay D weathered bed rock (3 × 2 = 6) 2. Supply ONE word/term for each of the following descriptions. Write only the word/term next to the question number. 2.1 Smallest soil particle size 2.2 Usually made up of quartz grains 2.3 Has a generally smooth feel when rubbed between the fingers 2.4 Becomes very sticky when wet 2.5 Used in the laboratory to divide a soil sample up into different size fractions, usually by shaking 2.6 Separating soil into size fractions by gravity, in water 2.7 Fragile instrument used to measure the percentage of soil in suspension 2.8 Triangular diagram for representing percentages of different soil size fractions 2.9 Best type of soil (in terms of particle size) for agriculture 2.10 Method used in the field for rough estimate of soil texture (10 × 2 = 20) Longer questions 3. List at least FIVE of the properties of clay. (5) 4. Differentiate between a quantitative and a non-quantitative method of determining the textural classes of soil.  (4) 5. In soil science, what is generally meant by the term experiment? (2) 6. Describe the soil properties that are influenced by the presence of of either sand or clay, or both. (6) 7. Explain why farmers need to know about the texture of soil on their farms. (5) Unit 2 Soil structure Short questions 1. Various possible answers are provided for the following questions. Write only the correct letter (A–D) next to the question number. 1.1 Soil structure refers to: A the size of the soil particles B the way soil particles bind together C the colour of the soil D the amount of clay in the soil 1.2 Clumps of soil formed by tillage or ploughing are called: A aggregates B peds C clods D clumps S T U DY & M A S T E R S U P P O R T PA C K S 1

1.3 Soil structure depends largely on: A the material from which the soil has developed B the amount of air in the soil C the colour of the soil D the amount of humus in the soil  (3 × 2 = 6) 2. Supply ONE word/term for each of the following descriptions. Write only the word/term next to the question number. 2.1 Biscuit crumb soil structure 2.2 Structure describing thin flat plates of soil 2.3 Structure found in very sandy soils 2.4 Practice of reducing or doing away with ploughing 2.5 Used to describe a soil that has lost its fertility through over-use 2.6 The remains of living material in the soil 2.7 Mineral material that makes up part of the soil 2.8 Occurs when clay and silt collect on the surface, get wet, and then dry out 2.9 Provides nourishment for plants and helps maintain soil structure 2.10 Part of a plant that is below the soil surface  (10 × 2 = 20) Longer questions 3. Describe some of the agricultural practices that contribute to the destruction or decline of soil structure. (8) 4. Explain how farmers can improve poor soil structure. (6) 5. Outline the advantages of good soil structure. (6) Unit 3 Soil colour and soil pores Short questions 1. Various possible answers are provided for the following questions. Write only the correct letter (A–D) next to the question number. 1.1 Gaps or spaces within the soil are referred to as: A holes B cavities C pores D caves 1.2 A sign of poor drainage in soil gives a blotchy appearance called: A dappling B speckling C mottling D sparkling 1.3 The standard set of colour charts used to describe soil colour is published by: A Mansel B Mosel C Munsell D Mistral  (3 × 2 = 6) 2. Supply ONE word/term for each of the following descriptions. Write only the word/term next to the question number. 2.1 Meaning the same, or uniform in terms of soil colour 2.2 Term for a comparison between mass (weight) and volume (space) in a soil 2.3 Term for a very light and easily worked soil 2.4 Main colour of soils in tropical regions 2.5 Main colour of soils containing lots of organic material 2.6 Main colour of sandy soils or soils in dry regions 2.7 Coatings of this substance will give soil grains a reddish colour 2.8 Term to describe a soil that is saturated with water 2.9 Very large soil pores 2.10 Very small soil pores (10 × 2 = 20) Longer questions 3. Describe what soil colour can tell us about a particular soil. (5) 4. Explain the difference between porosity and permeability in soil. (4) 2 S T U DY & M A S T E R S U P P O R T PA C K S

5. Explain the importance of soil pores in a soil. (4) 6. Briefly describe what happens to the density of a soil if the pore space increases. (2) 7. Explain what will happen to a soil if heavy vehicles or machinery continually drive over the surface. (3) Unit 4 Soil air Short questions 1. Various possible answers are provided for the following questions. Write only the correct letter (A–D) next to the question number. 1.1 Which ONE of the following does not fit? Air is: A an invisible mixture of gases B supports combustion C has a strong odour or smell D is found in soil 1.2 Soil air occurs in: A clay soils only B sandy soils only C silt soils only D pore spaces in the soil 1.3 With increasing depth in a soil, the volume of air generally: A increases B decreases C stays the same D is exchanged for carbon (3 × 2 = 6) 2. Supply ONE word/term for each of the following descriptions. Write only the word/term next to the question number. 2.1 Refers to the ability of air to circulate in the soil 2.2 Water in a gas, rather than a liquid form 2.3 The main gas making up air 2.4 The gas in air that supports life 2.5 The gas released from the soil by soil respiration 2.6 Plants such as beans and peas which help to fix nitrogen in the soil 2.7 Very small soil organisms 2.8 Breaking down of organic (plant) material in the soil 2.9 Term used for cultivated land that is allowed to rest for a season or two 2.10 The process through which water moves through, and out of the soil  (10 × 2 = 20) Longer questions 3. If you have three soil clods, how would you determine which one is holding the most soil air? (5) 4. Name at least THREE factors that affect and influence storage and movement of soil air. (3) 5. Briefly explain any TWO of the factors influencing the composition of soil air. (4) 6. List the FOUR components of all soils. (4) 7. Explain why soil air and its importance is sometimes overlooked by scientists and farmers. (2) Unit 5 Soil water Short questions 1. Various possible answers are provided for the following questions. Write only the correct letter (A–D) next to the question number. 1.1 The chemical formula for water: A H2SO4 B HO C HO2 D H2O 1.2 Soil water found in micropores in the soil: A gravitational water B free water C capillary water D excess water S T U DY & M A S T E R S U P P O R T PA C K S 3

1.3 Water that flows over the soil surface is called: A runup B rundown C runoff D runaway  (3 × 2 = 6) 2. Supply ONE word/term for each of the following descriptions. Write only the word/term next to the question number. 2.1 Soil water in solid form 2.2 Soil water in liquid form 2.3 Soil water in gas form 2.4 Methods of applying water to crops 2.5 The direction in which gravity will move soil water 2.6 The direction in which capillarity will move soil water 2.7 The term used when the soil cannot hold any more water 2.8 Water turning from a liquid into a gas 2.9 Water falling from clouds in the sky 2.10 Equation to explain gains and losses in soil water  (10 × 2 = 20) Longer questions 3. Name the forces that have an effect on soil water.  (4) 4. Write down the letters A to D and identify what is indicated on the following diagram.  (4) 5. Explain what has happened to this plant and why it looks like it does.  (4) 6. Discuss effective soil water management. (6) 4 S T U DY & M A S T E R S U P P O R T PA C K S

Unit 6 Soil temperature Short questions 1. Various possible answers are provided for the following questions. Write only the correct letter (A–D) next to the question number. 1.1 The ability of heat to move from soil particle to soil particle is an example of: A thermal diffusivity B thermal convection C thermal conductivity D thermal radiation 1.2 The ability of heat to move through the pore spaces in a soil is an example of: A thermal diffusivity B thermal convection C thermal conductivity D thermal radiation 1.3 The instrument used to measure soil temperature is a soil: A barometer B hydrometer C hygrometer D thermometer  (3 × 2 = 6) 2. Supply ONE word/term for each of the following descriptions. Write only the word/term next to the question number. 2.1 The amount of heat needed to raise the temperature of a given amount (unit mass) of soil (or any other substance) by a given amount (usually one degree) 2.2 Organic material spread over the soil surface to help insulate it 2.3 The term used to describe seeds sprouting 2.4 Energy (heat) from the sun 2.5 The usual scale used to measure soil temperature 2.6 The highest temperature reached in a soil 2.7 The lowest temperature reached in a soil 2.8 The effect of heat reflection by light-coloured soil surfaces 2.9 The process of a soil (usually dark soils) taking in a lot of heat 2.10 Permanently frozen soil  (10 × 2 = 20) Longer questions 3. Explain at least FIVE of the factors influencing soil temperature.  (10) 4. Briefly describe the general effect of warmer soil temperatures on biological activity in the soil. (2) 5. Explain why soil temperatures are so important for farmers. (4) 6. Write a paragraph on why it is sometimes necessary to control or manipulate soil temperature, and mention how this can be done. (4) Unit 7 Soil morphology Short questions 1. Various possible answers are provided for the following questions. Write only the correct letter (A–D) next to the question number. 1.1 An exposed, vertical cut through a soil from top to bottom gives us a soil: A layer B horizon C profile D transect 1.2 A hole dug to inspect a soil is known as a soil: A hole B cavity C gap D pit 1.3 The name for the main horizons in a soil: A primary B master C chief D important  (3 × 2 = 6) S T U DY & M A S T E R S U P P O R T PA C K S 5

2. Supply ONE word/term for each of the following descriptions. Write only the word/term next to the question number. 2.1 Soil horizon at the surface with lots of organic material 2.2 Rock that the soil develops from and on 2.3 An old, well-developed soil that will change little 2.4 Soil deposited mainly by the action of running water 2.5 Soil deposited mainly by wind action 2.6 Saturated soil 2.7 The massive removal of soil by wind in the American mid-west in the 1930s 2.8 The zone where organic compounds have been drained away in a soil 2.9 The breakdown of organic material in soils in the presence of oxygen 2.10 Looking after, or caring for the soil (10 × 2 = 20) Longer questions 3. Label the following diagram (using the numbers 1 to 6) and give the diagram a suitable heading: 1 2 3 4 5 6 (8) 4. Explain the meaning of the term ‘eroded soil’ and why such soils are infertile. (4) 5. What is meant by soil morphology? (2) 6. Give your opinion on why different soils have different morphologies. (4) Unit 8 Soil classification Short questions 1. Various possible answers are provided for the following questions. Write only the correct letter (A–D) next to the question number. 1.1 Classification means to: A allocate things to groups or classes B give things specific numbers C give things specific names D give things specific letters 1.2 South Africa uses this type of soil classification system: A monomial B binomial C trinomial D quadnomial 6 S T U DY & M A S T E R S U P P O R T PA C K S

1.3 The number of soil forms in the South African classification system is: A 43 B 53 C 63 D 73 (3 × 2 = 6) 2. Supply ONE word/term for each of the following descriptions. Write only the word/term next to the question number. 2.1 The identification and naming of soils according to an orderly system of defined classes 2.2 The common name given to South Africa’s blue book of soil classification 2.3 Soil forms can be divided into these in the South African classification system 2.4 The instrument used in the field to extract a soil sample 2.5 The name given to characteristics that help us differentiate between different soils 2.6 Nitrogen, potassium and phosphates found in the soil and which support plant growth 2.7 An example of a crop type that should not be planted in acidic soil 2.8 The term used for a mineral or element that is not soluble in, say, water 2.9 The horizon occurring just below the topsoil 2.10 The richness or poorness of a soil in terms of its ability to support crops (10 × 2 = 20) Longer questions 3. Give a reason why, in agricultural science and agriculture, there is a need to classify soils. (6) 4. Outline the SIX steps taken to classify a soil in the field. (6) 5. Name the FIVE diagnostic soil horizons in the South African soil classification system. (6) Unit 9 Soil colloids and acidity Short questions 1. Various possible answers are provided for the following questions. Write only the correct letter (A–D) next to the question number. 1.1 The tiniest of soil particles is a: A sand grain B colloid C silt particle D dust speck 1.2 A study of soil colloids involves mainly: A soil chemistry B digging holes in the soil C interviewing farmers D separating soil samples 1.3 Organic soil colloids are referred to as: A sand B silt C clay D humus  (3 × 2 = 6) 2. Supply ONE word/term for each of the following descriptions. Write only the word/term next to the question number. 2.1 A soil particle that doesn’t have a neutral charge on its surface 2.2 This clay swells the most of all clays in the presence of water 2.3 This clay swells the least of all clays in the presence of water 2.4 This is good for plant growth due its physical, chemical and biological properties, and its nutritional value 2.5 To hold in a thin film on the outside surface of a particle 2.6 This happens to a soil when basic cations are replaced by acidic cations 2.7 That part of a plant where cation exchange occurs 2.8 The most common plant nutrient found in fertilisers 2.9 Soil with a pH of around 5 or 6 2.10 Soil processes that involve living organisms (10 × 2 = 20) S T U DY & M A S T E R S U P P O R T PA C K S 7

Longer questions 3. Explain what this diagram shows. humus root Ca+ K+ H+ H+ root hair Ca+ Mg+ Fe+ H+ Ca+ H+ K+ K+ H+ K+ clay H+  (4) 4. Explain the difference between negatively and positively charged soil ions and why this is important in terms of plant nutrients. (6) 5. Explain the concept of cation exchange capacity.  (4) 6. Briefly mention some of the effects of acidity on crop production. (4) 7. How can nutrient-poor soil be improved? (4) Unit 10 Soil alkalinity and salinity Short questions 1. Various possible answers are provided for the following questions. Write only the correct letter (A–D) next to the question number. 1.1 Soil with a pH of over 7 is: A acidic B sodic C alkaline D brackish 1.2 Water with more salt than fresh water is: A acidic B sodic C alkaline D brackish 1.3 Soil with an exchangeable sodium percentage (ESP) of more than 15 is: A acidic B sodic C alkaline D brackish  (3 × 2 = 6) 2. Supply ONE word/term for each of the following descriptions. Write only the word/term next to the question number. 2.1 Another term for high alkalinity 2.2 Another term for a soil with lots of salt 2.3 The common soil compound with the formula NaCl 2.4 The common soil compound with the formula CaCO3 2.5 The common solvent in which soil minerals will dissolve 2.6 The typical colour of soil surface where lots of salt or carbonates are present 2.7 Condition where tiny soil particles cluster together 2.8 This gas is produced in the soil by respiration from plant roots 2.9 Substances, other than humus, produced by the breakdown of organic matter by bacteria in the soil 2.10 The term for a soil that is neither acidic nor alkaline  (10 × 2 = 20) 8 S T U DY & M A S T E R S U P P O R T PA C K S

Longer questions 3. Give the factors that may lead to an increase in soil brackishness, alkalinity or salinity. (6) 4. Describe the effects that too high an alkalinity or saltiness has on crops. (4) 5. Discuss ways of controlling salinity and alkalinity in soils. (6) 6. Name the TWO colours associated with the litmus paper test for alkalinity. (2) Memorandum Unit 1 Short questions 1.1 B 1.2 A 1.3 D (6) 2.1 clay 2.2 sand 2.3 silt 2.4 clay 2.5 sieve 2.6 settling or settling column 2.7 hydrometer 2.8 ternary or textural diagram 2.9 loam 2.10 feel method  (20) Longer questions 3. Tends to affect the chemical properties of the soil; adsorbs and holds plant nutrients; contains very small pore spaces, but the total pore space is very large; has a high water-holding capacity; warms up slowly; becomes sticky when wet; has a very large surface area; and has a sticky, buttery feel (5) 4. The quantitative method provides accurate data regarding proportions of different size fractions; the non- quantitative method is generally a look and feel procedure which results only in a description (no data).  (4) 5. A procedure, conducted in the field or laboratory following the scientific method, to test a hypothesis or to find out more regarding some aspect of a soil (2) 6. Soil properties that are influenced by the presence of either soil or clay, or both: cohesion (ability of like particles to bond); erodibility (how easily a soil will erode); permeability and porosity (ability of a soil to absorb and hold water); fertility; cation exchange capacity (ability of a soil to hold nutrients and to make these available to plants); workability (the ease with which a soil can be cultivated) (6) 7. Infiltration rates and water-holding capacity, soil fertility and workability are all influenced by soil texture. It helps the farmer know which fertilisers to apply, and how much, and assists in determining which crops should be cultivated. (5) Unit 2 Short questions 1.1 B 1.2 C 1.3 A (6) 2.1 granular 2.2 platy 2.3 single grain 2.4 minimum or no tillage 2.5 infertile or exhausted 2.6 organic matter or humus 2.7 inorganic fraction 2.8 cracking 2.9 organic matter or humus 2.10 roots  (20) Longer questions 3. Agricultural practices impacting soil structure (any eight): • Any disturbance that exposes soil to greater than usual desiccation, raindrop splash, or wind or rill erosion • Any tillage or ploughing or other practice that accelerates the decomposition of organic matter • Burning, removal or grazing of a harvested field that prevents soil organic matter from building up • Overgrazing, which typically leads to weaker plants with poor root systems, less growth and bare soil • The movement of animals or farming equipment over wet soils • Paths or tracks cut by vehicles or livestock exposes and compacts bare soil • Tillage of soil when it is too wet (can result in clods forming) or too dry (soil may become powdery) • Any practice, including irrigation, that may lead to salt or sodium accumulation in the soil (8) S T U DY & M A S T E R S U P P O R T PA C K S 9

4. Increasing organic content; crop rotation; reducing or doing away with ploughing (minimum tillage) in cropping and pasture activities; protecting soil from compaction, or drying out or wetting too much; on irrigated fields, gypsum (calcium sulphate) can be applied to displace sodium cations with calcium and so reduce sodicity; avoiding rapid wetting or disturbing soils when too wet or dry also helps preserve structure (6) 5. Good soil structure helps prevent crusting, cracking, soil erosion, soil compaction and chemical and nutrient imbalances. It helps keep the soil workable and aerated, and helps control soil water.  (6) Unit 3 Short questions 1.1 C 1.2 C 1.3 C (6) 2.1 homogenous 2.2 density 2.3 friable 2.4 red 2.5 brown or black 2.6 yellow or white 2.7 iron oxide 2.8 saturated 2.9 macropores 2.10 micropores  (20) Longer questions 3. When used in combination with other characteristics, soil colour is useful in establishing how that soil was formed or the factors that have influenced it, such as waterlogging. It also helps farmers make decisions regarding suitable land use on a particular soil. Soil colour does not itself greatly affect the soil, but it does give an indication of soil conditions. The main soil colourants are iron oxide and organic matter. (5) 4. Porosity refers to how porous a soil is, that is, how much water it can hold. It is a function of total pore spaces. Permeability refers to how easily water can permeate, or sink into or move through the soil. It is a function of the size of pore spaces.  (4) 5. Pores spaces hold soil air, water and organic matter. They influence drainage, and the ease or otherwise with which a soil can be cultivated and with which plant roots can penetrate the soil.  (4) 6. The density will decrease, because the volume of pores to soil grains has increased.  (2) 7. The soil will become compacted. Pore space decreases, meaning less water and air can be held in the soil. The soil loses its structure; plant roots cannot penetrate easily, and the soil quality is, in general, reduced.  (3) Unit 4 Short questions 1.1 C 1.2 D 1.3 B (6) 2.1 aeration 2.2 water vapour 2.3 nitrogen 2.4 oxygen 2.5 carbon dioxide (CO2) 2.6 legumes 2.7 micro-organisms 2.8 decomposition 2.9 fallow or resting 2.10 percolation or flow  (20) Longer questions 3. By placing each clod in a separate beaker of water at the same time, and timing the release of air bubbles. The last clod to emit air bubbles was the one holding the most air in its pore spaces.  (5) 4. Factors that affect and influence storage and movement of soil air (any three): Volume of pore spaces; size of soil spaces; soil depth; aeration; amount of water and water vapour in the soil  (3) 5. Factors influencing the composition of soil air (any two): nature and condition of soil; type of crop; microbial activity; seasonal variation; temperature (one mark for naming the factor, one for a fact regarding that factor) (4) 6. Minerals; soil air; soil water; organic (biotic) material  (4) 7. Soil air is often overlooked, because, unlike water or soil minerals, it is an invisible component of the soil. (2) 10 S T U DY & M A S T E R S U P P O R T PA C K S

Unit 5 Short questions 1.1 D 1.2 A 1.3 C (6) 2.1 ice 2.2 water 2.3 water vapour 2.4 irrigation 2.5 downwards 2.6 upwards 2.7 saturated or waterlogged 2.8 evaporation 2.9 precipitation or rain 2.10 gravimetric content  (20) Longer questions 3. Adsorption, capillary action, gravity, bonding, cohesion (4) 4. A precipitation or rain B transpiration C evaporation D soil water or soil pores (4) 5. The plant has wilted. More water is being lost through transpiration from the plant leaves than can be drawn up by the plant roots, so the plant is drying out, and the cell structure of the leaves is collapsing, resulting in wilting.  (4) 6. Soil water is effectively managed by monitoring and controlling water inputs and outputs so as not to waste water, but also to ensure the optimum amount of soil water for the crop that is being grown. It is a balance between water inputs and outputs. The soil water equation is: change in soil water = inputs of water – losses of water  (6) Unit 6 Short questions 1.1 C 1.2 B 1.3 D  (6) 2.1 specific heat 2.2 mulch 2.3 germination 2.4 insolation 2.5 Celsius or centigrade 2.6 maximum 2.7 minimum 2.8 albedo 2.9 absorption 2.10 permafrost  (20) Longer questions 3. Factors influencing soil temperature (any five): • The colour of the soil (dark colours absorb heat, light colours reflect it) • The presence of water (which takes longer to heat up than dry soil, making moist soils cooler than dry soils) • Vegetation (which can shade the soil from direct sunlight) • Slope aspect (soils on slopes that face the sun will be warmer than those in shadow) • Seasons (soils will be warmer in summer and cooler in winter) • Distance from the equator (in polar regions, some soils are permanently frozen because it is so cold) • Altitude (in high mountainous regions, soils will be cooler than in low-lying areas) • Wind (warm winds can raise soil temperature, and cold winds can lower it)  (10) 4. The warmer the soil, the greater the amount of biological activity. (2) 5. Seed germination is affected by temperature; root growth depends on soil temperature; sunlight absorbed by the soil raises mineral and soil water temperature; crop management depends on an understanding of soil temperature and how to control it.  (4) 6. Changing or modifying soil temperature can have advantages for agriculture. These include controlling germination and plant growth by increasing or decreasing the soil temperature, or prolonging the growing season. Mulching is the most common method of controlling and managing soil temperature.  (4) S T U DY & M A S T E R S U P P O R T PA C K S 11

Unit 7 Short questions 1.1 C 1.2 D 1.3 B  (6) 2.1 O horizon 2.2 bedrock or R horizon 2.3 mature 2.4 fluvial deposit 2.5 aeolian deposit 2.6 waterlogged or gleying 2.7 Dust Bowl 2.8 leaching 2.9 oxidation 2.10 managing or protecting  (20) Longer questions 3. Heading: Soil profile  (2) 1 O (organic) horizon 2 A horizon or root zone or topsoil 3 E horizon or zone of leaching 4 B horizon or subsoil 5 C horizon or partly weathered bedrock 6 R horizon or bedrock  (6) 4. An eroded soil has had all, or part of its topsoil and (possibly) subsoil removed by an agent of erosion such as running water or wind. Because all the soil nutrients are in the topsoil, these are lost, and the soil becomes infertile. (4) 5. The form of the soil, in terms of its profile and the horizons that are present (2) 6. Different soils develop under different climatic and geological conditions in different landscapes, in different parts of the world. (4) Unit 8 Short questions 1.1 A 1.2 B 1.3 D (6) 2.1 classification 2.2 MacVicar 2.3 series 2.4 auger 2.5 differentiae or properties 2.6 nutrients 2.7 legumes or one of: beans, peas, lucerne, clover 2.8 insoluble 2.9 subsoil or B horizon 2.10 fertility  (20) Longer questions 3. Classification of soils has different uses. Scientists look for new ways to make soil more productive. This research around better productivity and the efforts to manage soils correctly depends on proper classification. Soil classification serves a real purpose in improving, maintaining and managing soils as a resource. For the farmer, soil classification assists in knowing: which crops to cultivate; how to fertilise the crop correctly; and how to manage irrigation of the crop.  (6) 4. 1) Demarcate the master horizons (O, A, E, B, C, R, G) present in the soil profile in the field. 2) Identify diagnostic horizons or materials (horizons or material that are going to assist you in actually classifying the soil) in the profile. 3) Establish the soil form using the key in Chapter 5 of MacVicar’s book. 4) Identify family differentiae, also using the book. 5) Establish the soil family. 6) Determine the texture class of the A horizon and add it to the name or code of the soil family. (6) 5. Organic O (high organic carbon content, often saturated) Humic A (humus rich, containing significant organic carbon) Vertic A (has strongly developed structure) Melanic A (characterised by dark colours) Orthic A (an A horizon that doesn’t qualify as any of the other diagnostic horizons) (6) 12 S T U DY & M A S T E R S U P P O R T PA C K S

Unit 9 Short questions 1.1 B 1.2 A 1.3 D  (6) 2.1 ions or cations or anions or positively charged or negatively charged 2.2 smectite 2.3 kaolinite 2.4 fertiliser 2.5 adsorption 2.6 acidity or acidification 2.7 roots 2.8 nitrogen 2.9 neutral 2.10 organic (20) Longer questions 3. Cation exchange between soil surface ions and plant roots. Nutrient elements on the colloid are exchanged for hydrogen ions from the plant root.  (4) 4. Cation exchange is constantly going on in soils. Without some mechanism to temporarily hold cations in the soil, plants would be unable to obtain sufficient quantities of the essential nutrients to grow. Without cation exchange, the nutrients would simply be leached downward in the soil and lost. Cation exchange plays a role in other soil processes as well. Acidification is the process of exchanging basic cations, such as Ca2+, Mg2+, K+ and Na+, for acidic cations, such as H+ and Al3+. If cationic fertiliser nutrients are not held by the soil colloids, the nutrients would be lost to percolation water. (6) 5. This is the ability, potential or capacity of soil (a quantitative measure of the ability of a soil to exchange cations with the soil solution). (4) 6. In large amounts, aluminium and manganese are toxic. They are a major cause of crop failure in acid soils. Soil pH also has a strong influence on the availability of various nutrients from the soil to the plant. Thus low soil pH (acidic reaction) lowers the availability of such nutrients as phosphorus. On the other hand, too high a soil pH (alkaline) may impair plant growth by rendering certain nutrients such as manganese, potassium, boron, iron and zinc unavailable. (4) 7. Cation exchange capacity (CEC) refers to the ability of soil particles to hold cations on their surfaces. it is a measure of how many cations can be retained on soil particle surfaces in a particular soil. These cations are the nutrients which the soil exchanges with plant roots growing in the soil. Clay soils have a higher CEC than sandy soils, because of the greater extent of surface area in clay particles compared to sand grains.  (4) Unit 10 Short questions 1.1 C 1.2 D 1.3 B (6) 2.1 basic 2.2 saline 2.3 sodium chloride or salt 2.4 calcium carbonate 2.5 water 2.6 white 2.7 flocculate 2.8 carbon dioxide 2.9 acids 2.10 neutral  (20) Longer questions 3. Natural and human factors; over-irrigation of soil (increases salinity); too much fertiliser; certain minerals containing lots of sodium; dry conditions; leaking farm dams, especially in dry areas, can cause soluble salts to be brought to the surface, resulting in brack conditions (6) 4. It will damage the crops; uneven or stunted growth; wilting or even dying of plants; reduce yields, or even make the soil too saline to plant crops.  (4) 5. Scraping is when the salts that have accumulated on the soil surface are removed by mechanical means. Flushing is when the surface accumulated salts are washed away by flushing water over the surface. Leaching is the most effective procedure for removing salts from the root zone of soils – salty drainage water is led away through subsurface drains that carry the leached salts away. In very alkaline soils, the pH can be lowered by using fertilisers containing ammonium. (6) 6. Red (acidic) and blue (alkaline)  (2) S T U DY & M A S T E R S U P P O R T PA C K S 13