GRADE 11

B.G SKOSANA|201005620| October 31, 2016
GRADE 11
LIFE SCIENCES: SOIL BIOLOGY

How to use ………………………………………………………………………………………………………………………
To the learners
Welcome to this material!
Let’s have fun learning about soil. This guide is design to help you to understand one of
the most interesting resources, soil and its function in the biosphere. You can use the
guide alone or as part of a lesson about soil in order to learn in a fun and meaningful way.
Upon completion of this study material you will be able to explain:
 why decomposition is affected by climate conditions
 why different materials have different decomposition rates
 why soil quality is important
 why decomposition differs in different soil orders & in soils of different regions
Show an understanding of:
 the concept of decomposition
 its relevance for soil fertility & our climate
To define:
 soil
 organic matter
Analyze
 concept of nutrient cycling
Show appreciation:
 soil as a non-renewable resource
Draw and label the general soil profile.
TIME PLAN
DURATION OF TOPIC 3 WEEKS
TEST 1H 30
PRACTICAL 2HOURS

Introduction
SOIL BIOLOGY
Soil is full of life. It is often said that a handful of soil has more living organisms than there
are people on planet Earth. Soils are the stomach of the earth, consuming, digesting, and
cycling nutrients and organisms.
On firstobservation, however, soil may appear as a rather inert material onwhich we walk,
build roads, construct buildings, and grow plants. On closer observation, we observe that
soil is teeming with living organisms. Living organisms present in soil include archaea,
bacteria,fungi,algae,protozoa,and a widevarietyof larger soil fauna,including springtails,
mites, nematodes, earthworms, ants, insects that spend all or part of their life
underground, and larger organisms such as burrowing rodents. All of these are important
in making up the environment we call soil and in bringing about numerous transformations
that are vitally important to life.
SOIL
BIOLOGY
SOIL BASICS
FORMATION
BIOLOGY LIFE
IN SOIL
SOIL
FERTILITY

SOIL BASICS
JUST WHAT IS SOIL?
Soil has been a defining component of cultures since the beginning of civilization. Some of
the firstwritten words wererecordedon claytablets and water was carriedinclaypitchers.
It provides the base for all buildings (although some may be able to support a skyscraper
and some others maynot be ableto support your weight),itholds the clues of past cultures
(to be revealed by archeologists or erosion), it supports the web of life (connecting all
ecosystems), provides materials to build houses, is a source of nutraceuticals (definite in
the AmericanHeritageDictionaryasa foodor naturallyoccurring food supplement thought
to havea beneficial effect on human health), and of course, provides the base for our food,
fiber, feed, and even some biofuels.
Therefore soil is defines as:
 The unconsolidated mineral or organic material on the immediate surface of the
earth that serves as a natural medium for the growth of land plants.
 The unconsolidated mineral or organic matter on the surface of the earth that has
been subjected to and shows effects of genetic and environmental factors of:
climate (including water and temperature effects), and macro- and
microorganisms, conditioned by relief, acting on parent material over a period of
time

Figure 1
Then what is dirt?
Dirt is what gets on our clothes or under our fingernails. It is soil that is out of place in our
world– whether tracked inside by shoes or on our clothes. Dirt is also soil that has lost the
characteristics that give it the ability to support life – it is dead. Soil performs many critical
functions in almost any ecosystem (whether a farm, forest, prairie, marsh, or suburban
watershed).
Soil formation
CLORPT- FOR SHORT
Soils differ from one part of the world to another, even from one part of a backyard to
another. They differ because of where and how they formed. Five major factors interact to
create different types of soils:
 CLIMATE
 ORGANISIMS
 RELIEF
 PARENTAL MATERIAL
 TIME

CLIMATE
Climate, Temperature and moisture influence the speed of chemical reactions, which in
turn help control how fast rocks weather and dead organisms decompose. Soils develop
faster in warm, moist climates and slowest in cold or arid ones.
ORGANISMS
Organisms—Plants root, animals burrow, and bacteria eat – these and other organisms
speed up the breakdown of large soil particles into smaller ones. For instance, roots
produce carbon dioxide that mixes with water and forms an acid that wears away rock.
RELIEF
Relief (landscape)—The shape of the land and the direction it faces make a difference in
how much sunlight the soils gets and how much water it keeps. Deeper soils form at the
bottom of a hill because gravity and water move soil particles down the slope.
PARENT MATERIAL
Parent material—Everysoil “inherits” traitsfromtheparent material fromwhichitformed.
For example, soils that form from limestone are rich in calcium and soils that form from
materials at the bottom of lakes are high in clay. Every soil formed from parent material
deposited at the Earth's surface. The material could have been bedrock that weathered in
place or smaller materials carried by flooding rivers, moving glaciers, or blowing winds.
Parentmaterial ischangedthrough biological,chemical andenvironmental processes,such
as weathering and erosion.
TIME
Time—All of these factors work together over time. Older soils differ from younger soils
because they have had longer to develop. As soil ages, it starts to look different from its
parent material. That is because soil is dynamic. Its components—minerals, water, air,
organicmatter,andorganisms—constantly change.Components areadded and lost. Some
move from place to place within the soil. And some components are totally changed, or
transformed.

SOIL PROFILE
There are different types of soil, each with its own set of characteristics. Dig down deep
into any soil, and you’ll see that it is made of layers, or horizons (O, A, E, B, C, R). Put the
horizons together, and they form a soil profile. Like a biography, each profile tells a story
about the life of a soil. Most soils have three major horizons (A, B, C) and some have an
organic horizon (O). The horizons are:
O – (humus or organic) Mostly organic matter such as decomposing leaves. The O horizon
is thin in some soils, thick in others, and not present at all in others.
A - (topsoil) Mostly minerals from parent material with organic matter incorporated. A
good material for plants and other organisms to live.
E – (eluviated) Leached of clay, minerals, and organic matter, leaving a concentration of
sand and silt particles of quartz or other resistant materials – missing in some soils but
often found in older soils and forest soils.
B – (subsoil) Rich in minerals that leached (moved down) from the A or E horizons and
accumulated here.
C – (parent material) The deposit at Earth’s surface from which the soil developed.
R – (bedrock) A mass of rock such as granite, basalt, quartzite, limestone or sandstone that
forms the parent material for some soils – if the bedrock is close enough to the surface to
weather. This is not soil and is located under the C horizon.
FIGURE 2

BILOGY IN SOIL
MICROBIAL AND DECOMPOSERS
Only 5% of what is produced by green plants is consumed by animals, but the 95% is
consumed by microorganisms. One gram of fertile soil can contain up to one billion
bacteria.Therearemany different types of bacteria, and most of them have not even been
discovered yet! Most of these bacteria are aerobic, meaing that they require oxygen from
the soil atmosphere. However, other bacteria need to livewithout oxygen, and other types
can live both with, and without oxygen. The growth of these bacteria is limited by the food
that is available in the soil.
Soil fungi are also large component of the soil that come in various sizes, shapes, and
colors. Mushrooms have underground roots (mycelium) that absorbs nutrients and water
until they are ready to flower in the mushroom form. They tolerate acidity, which makes
them very important to decompose materials in very acidic forests, that microbes cannot
do, they can also decompose lignin, which is the woody tissues for decomposing plants
SOIL ANIMALS
Soil animals are consumers and decomposers because they feed on organic matter and
decomposition occurs in the digestive tract. Some animals feed on roots, and others feed
on each other. There are several types of worms. Earthworms are the easiest to identify.
They eat plant material and organic matter, and excrete worm castings in the soil as food
for other organisms. They also leave channels that they burrow in, which increases
infiltration. Earthworms can weigh between 100-1,000 pounds per acre! There are also
microscopic worms called nematodes, or roundworms. These worms live in the water
around soil particles. There are several different types of nematodes, some of them eat
dead materials, others eat living roots, and some eat other living organisms. Some
nematodes are bad, and can cause severe root damage or deformation.
Aside from worms, another large body of insects are arthoropods that have exoskeletons
and jointed legs. These include mites, millipedes, centipedes, springtails, and grubs.

CARBON AND NUTRIENT CYCLING
Nurtient Cycling is the exchange of nutrients between the living and nonliving parts of the
ecosystem. Soil biologists measure how plants and microbes absorb nutrients, and
incorporate them into organic matter, which is the basis for the carbon cycle. There are
two main processes. Immobilization is when soil organisms take up mineral nutrients from
the soil and transform them into microbial and plant tissues. The opposite process is
mineralization, which is what happens when organism die and release nutrients from their
tissues. This process is rapidly changing, and very important in providing nutrients for
plants to grow. The carbon cycle and nitrogen cycle are both very important to soil
microbiologists.
SOIL MICROBE AND ORGANISM INTERACTION
Plant roots leak a lot of organicsubstances into the soil fromdead materials.Theseprovide
food for the microorganisms, and create zones of activity around the root called the
rhizosphere. In this zone, plant growth or toxic substances can be produced, but most of
these organisms are benefical.
Other scientists study soil diseases of plants and animals found in the soil. Bacteria and
fungi can cause plants to wilt or rot. TheGreat Potato Faminein Irelandin1845 was caused
by a fungus that caused the potato blight! These organisms don't just impact plants.
Humans can get sick if certain types of bacteria, like E-Coli, are present in our waste, and
that waste isn't treated properly.
Some fungi "infect" plant roots, but the relationship is symbiotic, meaning that it is
beneficial to both the plant and the root. These are called mycorrhiza, and they help plants
absorb more water and nutrients, increase drought resistance, and reduce infection by
diseases.
Another symbiotic relationship involves nitrogen. There is a lot of nitrogen in the
atmosphere, but it is not easy for plants to get. There are certain species of bacteria that
absorb nitrogen gas from the atmosphere, and form a nodule. These are called nitrogen
fixing bacteria. When the die, the nitrogen that they used are released for plants.

SOIL FERTILITY
Crops need nutrients just like people do. A fertile soil will contain all the major nutrients
for basic plant nutrition (e.g., nitrogen, phosphorus, and potassium), as well as other
nutrients needed in smaller quantities (e.g., calcium, magnesium, sulfur, iron, zinc, copper,
boron, molybdenum, nickel). Usually a fertile soil will also have some organic matter that
improves soil structure, soil moisture retention, and also nutrient retention, and a pH
between 6 and 7. Unfortunately, many soils do not have adequate levels of all the
necessary plant nutrients, or conditions in the soil are unfavorable for plant uptake of
certain nutrients.
Soil scientists that focus on soil fertility are interested in managing nutrients to improve
crop production. They focus on using commercial fertilizers,manures,wasteproducts, and
composts to add nutrients and organic matter to the soil. Sometime they also add
chemicals that change the pH to a more optimum level for nutrient availability to plants.
Soil fertility experts must also be careful to ensure that practices are environmentally
sustainable. Inappropriate management of nutrients can lead to contamination of lakes,
rivers, streams, and groundwater. In addition, adding amendments to the soil is expensive
and cuts into the profitability of farming operations, not to mention that toxic levels of
nutrients can be as bad as or worse than too little nutrients for the plants.
NUTRIENT MANAGEMENT
The goal of soil nutrient management is to sustainably produce profitable crops. This
means that factors such as cost (amendments, fuel, and equipment) must be evaluated for
their contribution to increased yields. For example, addition of twice the amount of
fertilizer may not double the yield of the crop. So, a farmer must determine if the cost of
additional fertilizer will be repaid by the predicted additional yield. Furthermore, the
farmer mustalwaysbe thinking about how inadequate or excessivemanagementpractices
will affect the soil over time. One of the major causes of erosion or soil loss is due to
destruction of soil structure, which can be attributable to practicessuch as intensive tillage
(soil mixing), excessive vehicular traffic, excessive removal of plant material (fallow fields),
and depletion of soil nutrients, especially nitrogen.

HUMAN AND SOIL INTERACTION
Since soil is so vital to human life,humans haveto moveand manipulateit inorder to utilize
it. This, however, can lead to environmental problems, soil loss, and degradation. Soil
degradation is a human-induced or natural process which impairs the capacity of soil to
function. As an example, in 3000 BC, the Sumerians built large cities in the deserts of
Southern Mesopotamia. Using irrigation, they farmed the desert soils and created large
food surpluses that made their civilization possible. But around 2200 BC, the civilization
collapsed. Scientists debate why, but one reason may be tied to the soil. Irrigating in dry
climates can cause a buildup of salt, a process called salinization. Few crops can tolerate
salt.The soil in this regionstill remainstoo saltyto growcrops. Other activitiesthat degrade
the soil include contamination, desertification, and erosion.
EROSION
Erosion occurs when soil particles are detached, transported, and depositied. Erosion is a
natural geologic process, examples of geologic erosion can be found in this animation by
McDougal and Little; however, humans can accelerate the process by removing cover.
Accelerated erosion occurs at 10-1000 times the natural rate. Erosion can happen in all of
the biomes on earth, and can be caused by removing trees or grasses. Removing the soils
generally leads to other types of degradation and reduced food production. Soil can be
eroded by wind or water.
DESERTIFICATION
Desertification is the extreme degradation of productive land in arid and semi-arid areas.
This is most common in the tropical savannah and prairies. This can create poor quality
vegetation, and the spreading of deserts to areas that weren't deserts before.
ACIDIFICATION
Acidification occurs when the basic cations (like Calcium and Magnesium) leach from the
soil, leaving the acidic cations in the soil (Hydrogen, Aluminum, iron and manganese). The
pH decreases and soil becomes more acidic. This is a natural process in weathering.
However, the use of certain fertilizers to provide food, like anhydrous ammonia, causes
soil to become more acidic much faster. This can occur in all biomes.

SALINIZATION
This build up of salt on the soil surface is called salinization. This is a very big problem in
the desert and prairie biomes. This can cause physical soil damage, and the ability to grow
plants.
MINING
Surface mining can drastically change the landscape. When the materials are gone, soil
science becomes very important to the reclamation process, which aims to restore the
landscape and plants to pre-mining conditions.

GLOSSARY OF TERMS
CLORPT – The five factors that influence what type of soil forms: climate, organisms, relief
(landscape), parent material, and time.
Compost – The remains of plants and animals after they have decomposed. Can be used
to fertilize soil and to improve its structure and ability to hold water.
Compounds – The combination of two or more elements. For example, hydrogen and
oxygen combine to make water.
Decompose (Decomposition) –To breakdown a compound into simpler compounds. Often
accomplished with the help of micro-organisms.
Ecologist – A scientist who studies interactions between organisms and their environment.
Eluviated horizon (E horizon) – A horizon from which minerals, clay, and/or organic matter
have been leached.
Enzyme – A protein that increases the rate of chemical reactions in an organism’s cells.
Erode (Erosion) – To wear away, or remove, rock or soil particles by water, ice, and/or
gravity.
Estuary – A semi-enclosed body of water with a source of fresh water and an outlet to the
ocean.
Fertility – The ability of a soil to supply essential nutrients to plants.
Fertilizer – A substance added to soil that contains plant nutrients such as nitrogen,
phosphorus, and potassium.
Horizon – A layer of soil with properties that differ from the layers above or below it.

Humus – Organic matter such as highly decomposed leaves.
Leaching – The removal of minerals and nutrients from a soil or a horizon as water passes
through it.
Loam – A soil texture with moderate amounts of sand, silt, and clay, sometimes in nearly
equal proportions. Good texture for farming and gardening.
Macronutrients – Nutrients needed by organisms in relatively large quantities.
Microbes – Microscopic organisms, such as bacteria and fungi. Microbes represent the
most abundant soil organisms.
Microbiologist – A scientist who studies microscopic organisms, or microbes.
Minerals – The inorganic particles in soils that weather from rocks.
Nutrients – Elements or compounds that nourish organisms. Essential for growth and
reproduction.
Organic matter – Material derived from the decay of plants and animals. Always contains
compounds of carbon and hydrogen.
Organisms – Living things such as bacteria, fungi, plants, or animals.
Parent material – The material from which a soil formed. Can be bedrock or materials
carried and deposited by wind, water, glaciers, and/or gravity.
Pedologist – A scientist who studies soils.
Photosynthesis – The process by which plants, some bacteria, and some algae use sunlight
to convert carbon dioxide and water into food and oxygen.

Pores – The space between soil particles, which can be filled with water or air. A porous
soil has lots of pores.
Productive – A term used to describe a soil that has the capacity to grow an abundance of
crops.
Relief – The shape of the land surface created by features such as hills and valleys.
Runoff – Water from precipitation or irrigation that does not soak into the soil but flows
off the land and reaches streams and rivers.
Salinization – The build-up of salts in soil. Often occurs in arid environments.
Soil – A mixture of minerals, organic matter, water, and air, which forms on the land
surface. Can support the growth of plants.
Soil profile – A section of the soil that has been cut vertically to expose all its horizons, or
layers.
Soil structure – The arrangement of soil particles into clusters, called peds, of various
shapes that resemble balls, blocks, columns, or plates.
Soil texture – The relative proportions of sand, silt, and clay particles.
Subsoil (B horizon) – The soil horizon richin mineralsthat eluviated,or leacheddown, from
the horizons above it. Not present in all soils.
Topsoil (A horizon) – Mostly weathered minerals from parent material with a little organic
matter added. The horizon that formed at the land surface.

Life Sciences
Practical: Soil Biology
Topic: Decomposition
Grade : 11
Time :2hours
Background information
Decay of organic matter, decomposition, is the breakdown of plant and other organic
material.Decompositionisa critical processfor life on Earth. Through decomposition, food
becomes available for plants and soil organisms that they use in their growth and
maintenance. When plant material decomposes, it loses weight and releases the
greenhouse gas carbon dioxide (CO2) into the atmosphere. In cold environments,
breakdown is slower than in warm environments, meaning more carbon is stored in the
soil and less CO2 is released. The speed of decomposition of plant material is determined
by:
 Environmental conditions (moisture content, acidity, nutrient content).
 The chemical composition of the material that needs to be broken down (wood vs
sugars).
 The presence of decomposers (organisms that are involved in the break down, like
mites, worms, fungy, bacteria.
Different organism groups specialize in different materials and make them available for
others). The amount of CO2 in the air is the balance of what plants take up and what
decomposition releases. As CO2 causes the athmosphere to warm, changes in
decomposition can affect the climate. Especially because the soil contains an enormous
amount of carbon. In order to understand global CO2 emissions from soils, it is important
to know more about decomposition in differentkinds of soils.Such an insight would enable
scientists to improve climate models that calculate current and future CO2 fluxes. Efforts
have already been taken to map global soil and climate conditions; however, an index for
decomposition rate is still missing. Many people have tried to estimate decomposition and
the relation between decomposition and environment, but in order to understand global
decomposition, we need more information on the relation between decomposition and
climate from around the world. As previous methods to measure decomposition required

a lot of work, predictions on the relations between soil and decomposition are often
imprecise. Decompositionis a part of the global carbon cycle and tells us about the
biological activity in the soil.Decomposition is the decay of organic (plant) matter by soil
microorganisms. This process releases nutrients from the organic matter that can be used
by the soil organismsand plants. It also releasesCO2, which is an important geenhouse gas
and that will be emitted to the atmosphere, which in turn may accelerate global warming.
PREPARATION QUESTIONS.
1.1 What is decomposition?
1.2 Who does decomposition?
1.3 What is organic matter?
AIM
1.1 What is the aim of the experiment?
MATERIALS
 Lipton Rooibos tea bags (93% rooibos)
 Lipton Green tea bags (89% green tea)
 Permanent, waterproof marker
 Spade or spoon
 Sticks to indicate the place where the tea is buried
 Scale, which should be accurate on 0.01 grams
 Warm & sunny place for drying the tea bags
 Data form to fill in your report(link on pg.3)
METHOD
Things that are done by the student are marked with an S, teacher activities are marked
with T.

1. T: For each student, or pair of student/student
group, Take an unused Lipton Green tea and Rooibos tea bag. To obtain better estimates
of TBI parameters, bury at least four sets of tea bags per site.
2. T: Print data forms for each group of students and make the calculation sheet available
on the computer.
3. S: Mark/number the tea bags on the white side of the label with a permanent black
marker. The yellow part will most likely disappear. The white part is plastic and writing on
it is safe (if your marker is good).
4. S: Before you bury the tea, measure the weight of each tea bag using scales (minimum
0.01 g accuracy) or the TBI flyer. Fill in the weight in the data form.
5. S: Bury the teabags in 8 cm-deep, separate holes while keeping the labels visible above
the soil
6. S: Mark the burial site with a stick (make sure that the stick is not prone to trampling
or removal by other people strolling around).
7. S: Fill in the data form: Note the initial weight, date of burial, geographical
position, environmental properties and experimental conditions of the site.
8. S: Recover the tea bags after approximately 90 days (for instance over the summer
holiday).
9. S: Remove adhered soil particles and dry at a dry, sunny place for at least 3 days.
10. S: Remove what is left of the label (the yellow/white square) but leave the string and
weigh the bags using scales (minimum 0.01 g accuracy) or the TBI flyer.
11. T: Calculate weight loss as percentage of the start weight. Calculate your TBI by using
the Excel sheet and compare the calculated parameters. Average per location or soil order
and compare.
RESULTS
DISCUSSION
CONCLUSION
Practical Memorandum
Discussion Questions

1.1 What is decomposition?
During plant growth, plants capture and fix the greenhouse gas carbon dioxide (CO2) in
various organic structures. When the plant dies, soil organisms such as fungi, bacteria, and
soil invertebratesbreakdown the dead plant material (litter)andreleasepartof the stored
carbon into the atmosphere as CO2 (Coleman et al., 2004). During this process of
decomposition, the various organic components of the litter are broken down with
different rates and to a different extend.
1.2.Who does decomposition?
There are tens of thousands of organisms that are involved in decomposition in 1 gram of
soil. They are mainly micro-organisms such as bacteria (40%) and fungi (50%). In common
terms we know them as mushrooms (which are only 0.5% of the organisms in the soil),
mold, and slime. Soil organisms such as fungi and bacteria do most of the decomposing
but few soil animals also have the needed enzymes that would allow them to digest plant
litter (Coleman et al., 2004). Worms are one of the exceptions as they are very important
decomposers. One square meter of soil can contain up to 1000 earthworms (Coleman et
al., 2004). However, these larger organisms cannot pass through the mesh of the tea bags,
so that you will only see the influence of micro-organisms.
1.3 What is organic matter ?
Organic matter in the soil originates primarily from dead plant remains (litter) and the
microbial biomass on this litter. It consists of many different compounds with varying
structure, content, and recalcitrance (Kögel-Knabner, 2002). The dead plant material
consists of aboveground (e.g., leaves) as well as belowground (roots) structures and
everything the plant loses or leaks (roots leak a lot of substances). Organic material in the
soil includes the elements carbon (C)(50%), oxygen (O) (40%), nitrogen(N) (3 %), and small
amounts of phosphorous (P), potassium (K), calcium (Ca), magnesium (Mg), and
micronutrients are also present. People generally classify organic material into three
different categories based on rate of decay.
Aim
To measure the effects of decomposition on organic matter and the role the soil
temperature and profile has on the rate of decomposition.

Method and Materials
THIRD PERSON PAST TENSE.
DICSUSSION
MUST INCUDE
 THE RATE OF THE ROOIBOOS BREAKDOWN
 RATE OF DECOMPOSITION
 HOW SOIL QUALITY AFFECTS DECOMPOSITION
 WHAT WOULD BE THE RESULT IF NO DECOMPOSITION OCCURES.
CONCLUSION
THE RATE OF DECOMPOSITION IS AFFECTED BY THE SOIL STRUCTURE
TEMPERATURE
ORGANIC MAKEUP OF THE MATERIAL

Life Sciences Test
GRADE: 11
TIME: 1H30
MARK ALLOCATION: 85
Please read the following instructions carefully
1. Answer all the questions in the question paper
2. Complete all the answers in the provided answer sheet
3. Write neatly and eligebly
4. Read the questions carefully
5. Enjoy the test
QUESTION 1 (6×2=12)
Choose the letter that best describes the answer and only write down the correct letter
next to the appropriate question number.
1.1 Which of the following are essential in the formation of soil?
A. Roots, animal and humans
B. Soil occurs naturally it is not formed?
C. Climate, organisms, landscape, parental material and time
D. Seasons, weather and global warming
E. None of the above.
1.2 Which of the following statement about soil is true?
A. Soils are not characterized by mineral inputs.
B. Soil is the same as dirt.
C. Plants do not form part of the soil.
D. Soil is a non-renewable resource.
1.3 Contamination of soil refers to?

A. The elevated levels of chemicals usually as a result of human activity.
B. The removal of soil from one place to the next.
C. The natural phenomenon that occurs in soil.
D. The pollution of watercourses by sediments.
1.4 Soil microbes are described as?
A. The plants that are sound in the soil.
B. The organisms that are found in the soil.
C. Viruses that live in the soil.
D. The mycorrhiza located in the soil.
1.5. Why is important for terrestrial plants to be placed in the soil?
A. The soil provides a root medium
B. To hide the roots
C. To help the plant grow
D. So that the soil does not become bare.
1.6. What gas is released by decay?
A. hydrogen.
B. oxygen.
C. Nitrogen.
D. carbon dioxide.
Question 2 (10×2=20)
Give the correct definition for the following terms.
2.1. Soil
2.2. Humus.
2.3. Parental material

2.4. Soil profile
2.5. Dirt.
2.6. Microbes
2.7. Nutrient cycling
2.8. Protozoa
2.9. Organic matter.
2.10. Soil biology.
Question 3 (35)
3.1. Nameand distinguish the three ways inwhich similar soil organismsaregrouped. (6)
3.2. State two ways that soil erosion can be prevented. (2)
3.3. Briefly describe what soil nutrients are and give one example. (4)
3.4. What is the difference between soil contamination and soil erosion? (4)
3.5. How do soils become contaminated? (4)
3.6. Fill in the missing words to explain what organic matter is.
(15)
Organic matter in the _________primarily from __________ (litter) and the
______________on this litter. It consists of many different compounds with
varying_______, ________, and _______. The dead plant material consists of
___________ (e.g., leaves) as well as______________ structures and everything the plant

loses or leaks (roots leak a lot of substances). __________in the soil includes the elements
___________, ___________, _______________, and small amounts of phosphorous (P),
potassium (K), calcium (Ca), magnesium (Mg), and micronutrients are also present. People
generally classify organic material into three different categories based on rate of decay
(i) _____________ (decays within 1 to 2 years, e.g., apples and the pulp in between the
veins of the leaf); (ii) _________ (10 to 100 years, e.g., the stalk of the apple, a branch);
and (iii) ________(100 to >1000 years, e.g., banana and orange peels).
QUESTION 4
Draw and label a soil profile and go on to discuss the different layers found in it. (20)
______________________________*Good luck*______________________________
Memorandum
QUESTION 1 (5×2=10)
Choose the letter that best describes the answer and only write down the correct letter
next to the appropriate question number.
1.1 Which of the following are essential in the formation of soil?
A. Roots, animal and humans
B. Soil occurs naturally it is not formed?
C. Climate, organisms, landscape, parental material and time
D. Seasons, weather and global warming
E. None of the above.
1.2 Which of the following statement about soil is true?
A. Soils are not characterized by mineral inputs.
B. Soil is the same as dirt.
C. Plants do not form part of the soil.

D. Soil is a non-renewable resource.
1.3 Contamination of soil refers to?
A. The elevated levels of chemicals usually as a result of human activity.
B. The removal of soil from one place to the next.
C. The natural phenomenon that occurs in soil.
D. The pollution of watercourses by sediments.
1.4 Soil microbes are described as?
A. The plants that are sound in the soil.
B. The organisms that are found in the soil.
C. Viruses that live in the soil.
D. The mycorrhiza located in the soil.
1.5. Why is important for terrestrial plants to be placed in the soil?
A. The soil provides a root medium
B. To hide the roots
C. To help the plants to grow
D. So that the soil does not become bare.
E. Both A and C
1.6. What gas is released by decay?
A. hydrogen.
B. oxygen.
C. Nitrogen.
D. carbon dioxide.
Question 2 (10×2=20)
Give the correct definition for the following terms.
2.1. Soil

 A mixture of minerals, organic matter, water, and air, which forms on the land
surface. Can support the growth of plants
2.2. Humus.
 Organic matter such as highly decomposed leaves.
2.3. Parental material
 The material from which a soil formed. Can be bedrock or materials carried and
deposited by wind, water, glaciers, and/or gravity.
2.4. Soil profile
 A section of the soil that has been cut vertically to expose all its horizons, or layers.
2.5. Dirt.
 It is soil that is out of place in our world– whether tracked inside by shoes or on our
clothes. Dirt is also soil that has lost the characteristics that give it the ability to
support life – it is dead.
2.6. Microbes
 Microscopic organisms, such as bacteria and fungi. Microbes represent the most
abundant soil organisms.
2.7. Nutrient cycling
 The exchange of nutrients between the living and nonliving parts of the ecosystem
2.8. Protozoa
 diverse group of unicellular eukaryotic organisms
2.9. Organic matter.
 Material derivedfromthedecay ofplants and animals.Always contains compounds
of carbon and hydrogen.

2.10. Soil biology.
 Is the study of microbial and faunal activity and ecology in soil.
Question 3 (35)
3.1. Name and distinguish the three ways in which similar soil organisms are grouped. (6)
MICRO-ORGANISMS
These are the smallest organisms (<0.1 mm in diameter) and are extremely abundant and
diverse. They include algae, bacteria, cyanobacteria, fungi, yeasts that are able to
decompose almost any existing natural material. Micro-organisms transform organic
matter into plant nutrients that are assimilated by plants. Two main groups are normally
found in agricultural soils: bacteria and mycorrhizal fungi.
MICROFAUNA
The micro fauna (<0.1 mm in diameter) includes inter alia small mites, nematodes and
protozoa that generallyliveinthesoil water filmsand feedon microflora,plantroots,other
micro fauna and sometimes larger organisms (e.g. entomopathogenic nematodes feed on
insects and other larger invertebrates). They are important to release nutrients
immobilized by soil microorganisms.
MESOFAUNA
Mesofauna (0.1-2 mm in diameter) includes mainly micro arthropods, such as pseudo
scorpions, springtails, mites, and the worm-like enchytraeids. Mesofauna have limited
burrowing ability and generally live within soil pores, feeding on organic materials,
microflora, micro fauna and other invertebrates.
3.2. State two ways that soil erosion can be prevented. (2)
Vegetation
Retaining Walls
Mulch/Fertilizer
3.3. Briefly describe what soil nutrients are and give one example. (4)

Undissolved or granular nutrients, and those that are chemically bound to soil particles,
are not immediately useful, although they have the potential to benefit the plant. Example
phosphorus.
3.4. What is the difference between soil contamination and soil erosion? (4)
Soil contamination means changing the physical, chemical and biological properties of soil,
leading to a reduction in its fertility and ability to conduct normal process of
decomposition, and therefore the circulation of matter in nature.
Soil erosion is a physical removal of soil from the surface layer of the ground.
3.5. How do soils become contaminated? (4)
Soil becomes contaminated due to industrial activity, agricultural chemicals, or improper
disposal of waste. The most common chemicals involved are petroleum hydrocarbons,
polynuclear aromatic hydrocarbons (such as naphthalene and benzo (a) pyrene), solvents,
pesticides, lead, and other heavy metals. Contamination is correlated with the degree of
industrialization and intensity of chemical usage.
3.6. Fill in the missing words to explain what organic matter is. (15)
Organic matter in the soil originates primarily from dead plant remains (litter) and the
microbial biomass on this litter. It consists of many different compounds with varying
structure, content, and resistance. The dead plant material consists of aboveground (e.g.,
leaves) as well as belowground (roots) structures and everything the plant loses or leaks
(roots leak a lot of substances). Organic material in the soil includes the elements carbon
(C) (50%), oxygen (O) (40%), nitrogen (N) (3 %), and small amounts of phosphorous (P),
potassium (K), calcium (Ca), magnesium (Mg), and micronutrients are also present. People
generally classify organic material into three different categories based on rate of decay:
(i)labileor active (decays within 1 to 2 years, e.g., apples and the pulp in between the veins
of the leaf); (ii) intermediate (10 to 100 years, e.g., the stalk of the apple, a branch); and
(iii) slow (100 to >1000 years, e.g., banana and orange peels).

QUESTION 4
Draw and label a general soil profile and go on to discuss the different components found
in it. (20)
O – (humus or organic) Mostly organic matter such as decomposing leaves. The O horizon
is thin in some soils, thick in others, and not present at all in others.
A - (Topsoil) Mostly minerals from parent material with organic matter incorporated. A
good material for plants and other organisms to live.
E – (Eluviated) Leached of clay, minerals, and organic matter, leaving a concentration of
sand and silt particles of quartz or other resistant materials – missing in some soils but
often found in older soils and forest soils.

B – (Subsoil) Rich in minerals that leached (moved down) from the A or E horizons and
accumulated here.
C – (Parent material) the deposit at Earth’s surface from which the soil developed.
R – (Bedrock) A mass of rock such as granite, basalt, quartzite, limestone or sandstone that
forms the parent material for some soils – if the bedrock is close enough to the surface to
weather. This is not soil and is located under the C horizon.

References
Coleman, D.C., D.A. Crossley Jr., and P.F. Gendrix. 2004. Fundamentals of soil ecology, 2nd
ed. Elsevier Academic Press, Burlington, MA.
Karlen,D.L.,Mausbach, M.J.,Doran,J.W., Cline,R.G.,Harris,R.F.,and Schuman, G.E.,1997.
Soil quality: A concept, definition, and framework for evaluation. Soil Sci. Soc. Am. J. 61:4–
10
Keuskamp, J.A., B.J.J. Dingemans, T. Lehtinen, J.M. Sarneel., and M.M. Hefting. 2013. Tea
Bag Index: A novel approach to collecting uniform decomposition data across ecosystems.
Methods in Ecology and Evolution 4(11):1070–1075.
Cleveland, C.C., S.C. Reed, A.B. Keller, D.R. Nemergut, S.P. O'Neill, R. Ostertag, and P.M.
Vitousek. 2014. Litter quality versus soil microbial community controls over
decomposition: A quantitative analysis. Oecologia 174:283–294.
Kögel-Knabner, I. 2002. The macromolecular organic composition of plant and microbial
residues as inputs to soil organic matter. Soil Biol. Biochem. 34:139–162.
Larson, W.E., and F.J. Pierce. 1991. Conservation and enhancement of soil quality. In: J.
Dumanski, editor, Evaluation for Sustainable Land Management in the Developing World.
Proceedings of the International Workshop, Chiang Rai, Thailand, 15–21 Sept. 1991.
Technical papers, vol. 2. Int. Board for Soil Res. and Management, Bangkok, Thailand, p.
175–203.
Decomposition:en.wikipedia.org/wiki/DecompositionSoilfertility:www.soils4teachers.org/
fertility

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