School Science Lessons
Primary Science Lessons, Year 5
2009-02-18
Please send comments to: J.Elfick@uq.edu.au
Suggested answers to the teacher's questions are shown within [square brackets].
5.22 Rain gauge
5.23 Wind speed and direction
5.24 Describe clouds
5.25 Push and pull forces
5.26 Air pressure
5.27 Germinate bean seeds
5.28 Depth of seeds
5.29 Germinate maize grain
5.30 Roots absorb water
5.31 Leaves lose water
5.32 Protect our mangroves
5.33 Collect rocks
5.34 Soil profiles
5.35 Fertilizer trial
5.36 Cover crops
5.37 Rain on slopes
5.38 Mulch garden soil
5.39 Make clay pots
5.40 Make potash from ash
5.41 Keep water clean
5.42 Heated air expands
5.43 Burn to make carbon
5.22 Rain gauge
See diagram: 24.4.5: Rain gauge
Be able to read a rain gauge and record the rainfall each day.
Use a rain gauge, glass jar, rain chart
Table of average rainfall in two places: Honiara and Avu Avu
Month Honiara Avu Avu
January 249 262
February 234 225
Total Rainfall 2195 5787
Number of wet days 195 222
The site selected for a rain gauge should be level ground not near fences or trees. Attach the bracket to a post about 1.5 metres above ground in a vertical position. Rainfall should be measured at 9.00 a.m. daily and the amount entered on the rain chart against the date of the previous day. To read the gauge, remove the plastic gauge from the bracket, take it to the chart, read the scale to the nearest millimetre (mm) record this on the chart, read the scale again and pour out the water. Replace the scale in the bracket. If you do not have a rain gauge, you use a glass jar on a post. Measure the depth of water in mm. This reading in mm will not be the same as a proper rain gauge in mm. Use a rain gauge or glass jar, rain chart on the wall (see over) or special rain recording book, ruled as in rain chart.
Each child must read the rain gauge.
1. Show the rain gauge or jar and ruler. Show how to read the gauge with water in it, hold the top of the gauge between thumb and first finger, hold it vertically, level of water should be opposite their eye, keep their back straight, read level of water to nearest mm.
2. Read the gauge but do not tell the children the reading. Pass it from child to child, read the gauge and write down the reading. When you have finished, ask the children to tell the class their readings.
3. Show the rain chart. Show how to write in it.
4. Go outside to the rain gauge position. Is it near trees or buildings? Show how to read the rain gauge at 9.00 a.m. each day and record it on the rain chart.
5. Draw up a roster of children to read the rain gauge each day, two children each day.
6 . Ask the children if they have heard rainfall measurements announced on the radio. If used properly, the rain gauge method is the same as that used by government officers who measure rain.
Rain chart mm Jan
 mm Feb
 mm Mar
 mm Apr
 mm May
 mm Jun
 mm Jul
 mm Aug
 mm Sep
 mm Oct
 mm Nov
 mm Dec
22 . . . . . . . . . . . .
23 . . . . . . . . . . . .
Totals . . . . . . . . . . . .
No. days . . . . . . . . . . . .
Totals since 1 Jan 2 months 3 months 4 months 5 months 6 months 7 months 8 months 9 months 10 months 11 months 12 months
Extra Activity
Record the readings from the chart on to a bar graph. In this graph below notice the difference in rainfall pattern between the north west coast and the east west coast of Guadalcanal. What results are given by similar activities in your own district?
5.23 Wind speed and direction
Be able to make regular recordings of wind speed and direction, and then summarize the observations.
Use a compass directions, a direction chart. This lesson is designed to give children the experience of making regular observations of the natural environment using inexact measurements. Use to set out the compass directions in the playground and make a wind speed and direction chart for the wall.
Wind speed and direction chart, Place: Honiara, Month: January, Time: 9.00 a.m., Wind speed: calm, light, moderate, strong, very strong, total, Wind direction: N north = 3, NE northeast = 0, E east = 0, SE southeast = 2, S south = 16, 16 SW south-west = 10, W west = 0, NW northwest = 0, Total = 31
Wind speed Calm Light Moderate Strong Very Strong Total
Direction . . . . . .
N 3 . . . . 3
NE . . . . . .
E . . . . . .
SE . 1 1 . . 2
S . 8 7 1 . 16
SW . 5 5 . . 10
W . . . . . .
NW . . . . . .
Total 3 14 13 1 nil 31
Wind speeds Description of what you see and feel
Calm Smoke rises straight up, no wind at all
Light You can feel wind on your face, leaves move on the trees
Moderate Raise dust and paper, small branches move on the trees
Strong Trees sway, whistling sound in telegraph wires
Very Strong Twigs break off the trees, you find it hard to walk against the wind
Each class must estimate wind speed and directions.
1. Explain that it is important to know the pattern of wind speed and direction so people can predict the weather. For example in January at Honiara you can expect light to moderate winds coming from the south or south-west. This information helps us to understand the weather and is useful for aircraft pilots and captains of ships.
2. Direction game: Line the children facing north. Hold your arms horizontally pointing your fingers. Pretend this is the direction of the wind. What is the direction of the wind? [Southerly.] Turn around facing south and hold your arms up. What direction is the wind? [North.] Call out different wind directions. The children have to point their arms in the wind direction. East wind, point west, west wind, point east, south-west wind, point northwest, north west wind, point south east.
3. Wind Speed Game:
4. Describe the present wind speed and direction and record it on the chart. Divide the class into pairs. At 9.00 a.m. each day each pair has to record wind speed and directions.
Extra Activity
1. What happens when a cyclone comes? [Strong wind in one direction, then calm, then strong wind in opposite direction.]
2. Beside the 9.00 a.m. reading observe wind speed and direction at 3.00 p.m. Is there a pattern of difference between the 9.00 a.m. and 3.00 p.m. observations? For example at Honiara in January the afternoon winds are usually lighter than the morning winds and swing from between S and SW to between N and NE. A similar observation and exercise should be carried out in your own area of the country.
3. Trade winds are winds that blow regularly in one direction, sometimes for six months, and are used for trade by sailing vessels. In the Northern hemisphere they blow from the north east and in the Southern hemisphere they blow from the south east, about 30o each side of the equator.
5.24 Describe clouds
See diagram 4.143: Different clouds | See diagram 4.135: Cloud in a bottle
Be able to identify and describe different types of cloud and relate the children to rainfall.
Use a clean dry glass, clouds. There are three main types of clouds, cumulus, stratus and cirrus.
1.1 Cumulus are the separate woolly clouds with sharp outlines. They join to form a big cloud with a flat dark base and bulging upper part, like a cauliflower. It may rise high in the sky and then spread out to form an anvil cloud. This cloud has a dark base and makes lightning, thunder and heavy rain.
1.2 Stratus is a great misty mass of cloud. It has no sharp outline. Therefore, stratus clouds have no shape. Lots of cumulus clouds can join to make a stratus cloud.
1.3 When the wind blows over the sea then up over a mountain, a layer of stratus cloud can form over the mountain. This produces rain, mostly on the windward side of the mountain. This can be called the weather coast.
1.4 Cirrus clouds are very high clouds and look like wisps of cotton wool or hairs. They do not bring rain.
1. Hold a clean dry glass upside down under a running tap to make it cold. Breathe strongly into the glass. Show the thin layer of water drops inside the glass that come from their breath, Explain that water is in the air but you cannot see it.
2. Explain how air picks up water when it passes over the sea. You cannot see the water in the air. However, if the air rises it becomes small drops of water as you saw in the glass. You see white cloud where sunlight bounces off the small water drops. As the water drops grow larger they sink to the bottom of the cloud that then appears dark.
3. Draw the different shapes of cloud. Use the side of the chalk to show the shapeless stratus.
4. Take the children outside. What sort of cloud can they see? Is it raining? Can they see clouds near mountains? Draw the clouds and the land.
Extra Activity
Cloud watch: Record the clouds and rainfall every day for a week. Can they describe the clouds that bring rain? Most thunderstorms occur from December to March in the afternoon over the larger and more mountainous islands.
5.25 Push and pull forces
See diagram: 4.181
Be able to show that a push or pull is a force that can make an object start moving, stop moving or change direction.
Use a big box or pieces of wood with a string or rope attached, a pile of coins, a ruler, a pile of books, a catapult, glass of water, table cloth. This lesson should be based completely on the practical applications of force and movement. Use the suggested instructional materials (and more) to vary demonstrations for push and pull.
1. Explain that a force can move things. What are two ways of moving the big box? [Push the box, pull the box by string.] What is a force? [A push or a pull.] Tell a child to push the box and another child to pull the box. Pushing the box. In which way are the child's feet pushing? [Away from the box.] Pulling the box. In which way are the child's feet pushing? [towards the box.] Explain to the children that when there is a force in one direction there is also a force in the opposite direction. Child pulling the box. What happens if the string breaks? [Child's body moves away from the box and falls over.] What happens if the ground is slippery? [Feet move towards the box and child falls over.]
2. Make a pile of coins, a heap of books and put a glass of water on a cloth. Hit the bottom coin with a ruler. Does it move? [Yes.] Do the other coins move sideways? [No.] Why not? [The force from the ruler was only on the bottom coin.] Pile the books so that you can grip the bottom book. Pull the bottom book out quickly. Do other books move sideways? [No.] Why not? [The pulling force was only on the bottom book.] Put the glass of water on a table cloth. Can you take away the table cloth without touching the glass of water? [Pull the table cloth very quickly. BE CAREFUL! If something is not moving and there is no force on it how does it move? [It cannot move.]
3. Imagine you are paddling a canoe. Which way does the paddle move? [Backwards.] Where can you feel the force on the paddle? [On the back of the paddle.] Which way does the canoe move? [Forwards.] If you stop paddling does the canoe keep moving or does it stop? [It keeps moving.] Is there a force on the canoe? [No.] Hold the paddle upright in the water. What happens to the canoe? [it moves slower then stops.] Where can you feel the force on the paddle? [On the front of the paddle.] Explain that for every force in a direction, there is an equal force in the opposite direction.
4. Link two spring balances then pull them apart. Compare your reading. [They are the same.] Put a scale on the floor, put another scale upside down on it, compare the readings. [They are the same.] Sit in a still canoe or child's cart. Throw out a big stone. What happens? [The canoe or cart moves in the opposite direction to the stone.] Fire a gun. Which way does the bullet go What do you feel on your shoulder? [A force in the opposite direction to the bullet.] Hold a stone in a catapult. Pull back. Let go of the stone. Why does it move? [It is pushed forward by the rubber in the opposite direction to the pull back.] Explain that forces are always in pairs. For every force forward there is an equal force backwards. For every force down there is a force up.
Extra Activity
Use a spring balance, a heavy object that you can attach to the hook and a container of water. Hold up the spring balance. Read the weight. [No weight.] Attach the heavy object. What happened to the spring in the spring balance? [It was pulled down.] Read the weight of the object. Lower the heavy object into the water. What is the weight now? [Less than before.] Why is it less? [The water pushed up on the object. The spring in the spring balance was pushed up.] Stand in a river. Pick up the biggest stone you can from the bottom of the river. Now lift the stone above the water. What happens? [the stone feels much heavier.] Why? [The water is no longer pushing up on the stone.] What are the two kinds of force? [Push or pull.] Give an example of force which: 1. Starts something moving, 2. Makes something go faster, 3. Makes something go slower, 4. Stops something, 5. Changes the direction of movement of something. How does a squid swim it squirts water backwards and so it moves forwards?
5.26 Air pressure
See diagram: 4.272
Be able to show that air presses on us in all directions.
Use coins, water, jar, cardboard, bicycle pump and inner tube of bicycle tyre (optional) large tin can with screw on lid, burner. Demonstrations with the listed instructional materials by the teacher before the real class is essential.
1. Rub together two coins of the same size. You can separate them easily. Now wet the touching surfaces of the coins with water, and rub them together. Can you pull them apart easily? [No.] Press a dry coin on your forehead and on the underside of your arm. It falls off easily. do this again with a wet coin. What happens? [It sticks to you.] Why does this happen? [The water pushes out any air between the coins and your skin. Air is pressing in all directions on the coins.]
2. Fill a jar with water right to the top. Put a card on top of the jar so that there is no air inside and the top is completely covered. Put one hand firmly on the card and carefully turn the jar upside down with the other hand. Now take away the hand from the card. The water should stay inside the jar. What is pressing up on the card to stop the water from falling out? [Air.]
3. Fill a ball pen or plastic bag with air and tie the open end. Squeeze the bag or balloon. If you can feel the air pushing when you squeeze the balloon. [Yes.] When the air pushes this is called air pressure.
4. Put your finger over the hole at the end of a bicycle pump and press the handle in as far as you can. Let the handle go. It will be pushed back out. What pushed the handle out? [Air pressure.] Where you can find air. [All around us.]
Extra Activity
1. Put some hot water in a coffee or milk tin. Put on the lid and heat the tin. What happens? [The lid flies off.] Why? [The hot water heats the air in the tin. The heated air expands and increases the air pressure inside the tin pushing the lid off.] During the observation, do not have your face too close to the tin.
2. Put some water in a large tin can which has straight sides and a screw on cap. Heat the can. When steam comes out screw on the lid and take away the burner. The can will collapse in all directions because of air pressure. What is all around us? [Air.] What does it do to us? [Air presses on us.] In which direction does air press? [All directions.]
3. Heat the can to boiling point, remove the flame and release cold water on it from a tap or bucket. The can similarly collapses.
4. Explain that cyclones occur when the air pressure is very low. This causes air to rush in towards the low pressure area causing strong winds.
5.27 Germinate bean seeds
See diagram 9.113.2d: Germinate bean seed
Be able to describe the stages in the germination of a bean seed.
Use bean seeds, wet paper, jar. The 2 types of germination:
1.1 Epigeal germination. The seed leaves (cotyledons) pop out of the ground, e.g. pea, bean.
2.2 Hypogeal germination. The seed remains in the ground, e.g. broad bean, corn, rice.
1. Soak some bean seeds in water. What changes do you see? [The skin becomes wrinkled and the seed swells.]
2. Put the soaked seeds in a jar with wet paper. tell the students to observe the seeds each day and describe what happens by completing this table: Bean, Day 1 Coat wrinkles, seed swells, Day 2 Root comes out, Day 3 Curved neck stage White finger stage, Day 4 Seed pops out of ground, Day 5 First leaves appear First leaves appear This can be extended to become a crop diary.
5.28 Depth of seeds
See diagram 9.113.2d: Seed levels
Be able to do an experiment to observe what happens when you plant seeds at different depths.
Use maize (corn) and bean seeds and a prepared seed bed. The best planting depth is usually two cm in wet soil and four cm in dry soil.
1. The aim of this experiment is to see what happens when seeds are planted at different depths.
2. Draw a diagram on the chalk board to show the design of the experiment. Also, tell the children to draw the observation table in their books.
3. Show how to plant the seeds and observe results.
4. Which depth is best for this seed Design of the Experiment 6 five four three two one Surface Observation Table Depth of Seed Number of days above ground Comment, Which depth is best Surface 1 finger deep 2 fingers deep 3 fingers deep 4 fingers deep 5 fingers deep more than one hand deep
Extra Activity
The two types of germination:
1. The seed coats come out of the ground (epigeal germination)
2. The seed coats remains under the ground (hypogeal germination)
3. Note the different types of seeds and the germination styles of each. Cut longitudinal and transverse sections of the corn grain. Be Careful Soak it for a day in water before attempting to cut it! Observe the shapes seen and compare with the diagram.
5.29 Germinate maize grain
Be able to describe the germination of a maize grain.
Use maize grain, rice or sorghum, jar, wet paper, knife, magnifying glasses. The seed of corn, rice and sorghum is really a fruit with a hard tight wall. It is called a grain. In Australia and England corn is called maize. Use corn grain soaked in water for a few days, knife and magnifying glasses. About one week before the lesson plant some soaked corn grains. A shoot is the stem and the leaves. Learn to cut soaked grains longitudinally and transversely with a knife. Be Careful!
1. Show the dry corn grains and soaked corn grains. What is the difference? [Soaked corn grains are softer and fatter.]
2. Look at the germinating grain. Can you see the first root? The white shoot cap? The first leaves breaking through the shoot cap?
3. Cut a soaked corn grain in longitudinal half. Can you see its parts? When there is enough water, air and warmth, the new plant will start to grow. This is called germination. When all this stored food has been used up, the plant will make its own food in its leaves.
Extra Activity
Corn germination project. Plant some soaked corn grain. How many days before:
1. germination,
2. shoot cap shows,
3. first leaves break through shoot cap?
5.30 Roots absorb water
See diagram 9.195: Plants absorb water | See diagram 9.73.3: Root hairs
Be able to show that plants take in water.
Use small plants such as Amaranths, glass jars, ink, cooking oil, water. In this lesson you can show that plants take up water in two ways: see whether the ink gets into the plant. Put the plants in the inky
1. Give out plants and inky water. Can the plants take in water How can you show this? [You will put plants in inky water and water. Remove them out after a few hours.]
2. How you can see how much water plants take in? [You will put some oil on water, than it cannot evaporate.] Draw the diagram. How will you know that the water went into the plant and nowhere else? [The inky water will show us where the plant went. You can also set up a control that contains no plant.] Set up the demonstration and put it aside.
3. Give out small plants with well washed roots, and magnifying glasses. Can they see the tiny root hairs? Take the plant out of the inky water. Break open the stem. Can they see the ink inside? What can you learn from this? [Roots take in water.] Look at the water with the oil in top. Is the water level the same? [No, it has gone down.] Why did it go down? [Some water went into the plant.] Look at the control. Did the water level go down? [No.] Why not? [There was no plant to take in the water.]
1. Put some ink in water then put the plant roots in it. After a few hours break open the stem with their thumb nails and they will see the ink in the stem 2. Put the plant in water and add about one cm thick of cooking oil. Mark the level of the water. After about one day the level of the water drops. If you have another jar with oil floating on it, you will notice that the water level in this jar has not dropped. This is called a control. It shows that the water level dropped because the plant absorbed it. If you look at the roots of a small plant, you can see what it uses to take in water. It takes in water through the root hairs.
5.31 Leaves lose water
See diagram 9.194.1: Transpiration in plastic bag
Be able to show that plant leaves give out water.
Use plastic bags, string, small tree with soft green leaves. Plants take water from the soil into their roots through root hairs. From there, water moves up the stem through to the leaves.
1. You will do an experiment to see what happens when a plastic bag is tied over leaves.
2. Show a dry plastic bag, and a tree branch with dry green leaves. Tie the bag over the leaves and return to it later in the day. Show the bag over the leaves and ask them to tell you what they see inside. [Water.] Where did the water come from? [It comes from the leaves.] Draw the bag over the leaves. Explain that all plants lose water through their leaves.
Extra Activity
How can they prove that water comes from the leaves and not the stem? [Tie the plastic bag around the stem with the leaves pulled off. No water will form in the bag.] Draw a plant then draw arrows on it to show how water moves through it. Write labels on the arrows. [Soil water, root hairs, stem, leaves, air.] Sentence completion: Plants take water from the soil into their [roots] through their tiny [root hairs]. The water then goes up the [stem] into the [leaves] then into the [air].
5.32 Protect our mangroves
Be able to explain why you should keep mangroves growing.
Use pictures of specimens of mangroves or a natural mangrove environment close to the school. You should either prepare to visit mangroves or have some pictures of typical mangroves. It is preferable to have both, for a lasting impression.
Mangroves are big trees that can live in the shallow sea water near the shore. Their roots grow in the mud or sand and are under water at high tide. Some people want to cut down the mangroves to use the wood or to get rid of mosquitoes or to clean trees from the shore. Some people do not like mangrove swamps because they cannot walk through them easily. Why should you keep mangroves?
1. They are very interesting plants. Many years ago they lived in the forest but they learned to live in shallow sea water and they developed special parts to do this. Some mangroves have roots that grow up through the mud to get air. Some mangroves have tall stilt roots for holding onto rocky land. Some mangrove seeds grow into small plants while still attached to the tree, and others form a long root that spears into the mud when it falls. Can they see anything else that is special about mangroves?
2. Mangroves hold the mud together and can make new land. If you kill all the mangroves, the mud will be washed into the sea. Many animals live in the mud and are part of the food chain. Many small fish live among the mangroves where they can hide. When these fish grow bigger, they swim into the sea.
3. When mangrove leaves die they fall directly into the sea. These leaves act as a fertilizer.
4. Mangroves have been part of the scenery of the country for a long time. You should not destroy your natural environment but keep it for the next generation to enjoy and learn from.
Visit a mangrove swamp. How many different kinds of animals can they find living in the mangrove trees and in the mud? Dig a deep hole in the mud. Can they smell a gas produced by anaerobic bacteria living in the airless mud? [Hydrogen sulfide.] Can you recognize Red Mangrove (Rhizophora) which possesses silt roots for absorption from the muddy surface? Which of them possesses breathing roots to keep the plant well aerated? [White mangrove, Avicennia.] Taste the leaves of the two plants. Which of them tastes more salty? [Avicennia leaves because they have salt glands on the upper leaf. The lenticels are concentrated on the upper part of the breathing roots or pneumatophores.]
5.33 Collect rocks
Be able to make a collection of the different types of rocks near the school.
Use rock types from different locations, boxes for the rocks, a hammer and a magnifying glasses. Before the lesson collect different types or rocks from your area. Try to include rocks from cliff faces, streams, the sea shore. Also tell the children to bring rocks from home before you teach this lesson.
The three main types of rocks are as follows:
1.1 Igneous rocks are formed from volcanoes. The rocks have cooled from very hot liquid rock. You can see whole crystals in them.
1.2 Sedimentary rocks are formed form particles of other rocks carried into rivers, lakes and the sea and then squeezed together. You can usually see the layers in the rock. Coral reef limestone are also classified as sedimentary rocks.
1.3 Metamorphic rocks were once igneous or sedimentary rocks but have been squeezed and heated again.
Do you know where the main rocks are found and their uses in your country?
1. Show the collection of rocks. Divide the rocks into those obtained from:
1.1 rivers, rounded pebbles, pieces from the edge of the river,
1.2 Sea shore, pieces of limestone, rounded stones,
1.3. Deep in the soil, stones,
1.4 Cliff faces, pieces of rock.
2. Wash the stones. Divide the children into two groups:
2.1 Have crystals, they shine when you turn the rock. These are igneous rocks from volcanoes.
2.2 Do not have crystals, usually have layers. These are sedimentary rocks formed at the bottom of lakes and the sea.
3. Look at the igneous rocks. Are the crystals darker or lighter than the rest of the rock? How big are the crystals?
4. Look at the sedimentary rocks. Can you see the layers? Are all the particles the same size How big are they? Limestone may contain shells. If you put some acid on limestone, it forms bubbles of carbon dioxide gas.
5. Make a display of their rock collection. Label it: igneous, metamorphic, sedimentary, where found, description of crystals, colours, layers.
Extra Activity
You can try to name the rocks you find:
Basalt:.heavy, dark rock, with very small crystals, some have green colour
Andesite: light coloured, with very small crystals
Limestone: looks dirty, no layers, fizzes in acid
Mudstone: sedimentary with fine particles, layered, easily broken
Sandstone:.sedimentary, separate sand grains can be seen
Conglomerate: sedimentary, has mixture of rounded stones and smaller particles.
5.34 Soil profiles
See diagram: 6.26
Be able to collect samples of different kinds of soils and what you see in them.
Use a sharp spade to dig the soil profiles and glass jars or pieces of glass. To dig a soil profile, find a flat area free of stones. Dig down vertically on three sides of a square. Dig the fourth side on a slope to make a wedge, then lift up the soil. The top few centimetres of soil are dark in colour because rotten plants and animals form a black sticky substance called humus. The topsoil is a layer containing the humus and most of the plant roots. Below it is the subsoil that contains mostly sand, stones and clay and some big tap roots. Below that is solid rock. The subsoil and topsoil may have formed from these rocks or the soil may have been dumped on the rocks by a river or water washing down. For his lesson see how many kinds of soil profiles you can collect:
1.1 Loam soil is a good garden soil found in river valleys. It may be black or red with much humus in the topsoil. Soil from a hill will have less topsoil than soil from a river valley.
1.2 Sandy soil is found just behind a beach or near the bend in a running river. It does not have much humus and dries out easily.
1.3 Clay soil is hard to dig in dry weather and very sticky in wet weather. It takes a long time to dry out and when it does it forms cracks. It usually has a red to brown colour.
1.4 Mangrove soils and poorly drained soils have a grey colour and often a funny smell.
1. Show how to dig a soil profile.
2. Collect different soil profiles. Measure the depth of topsoil and subsoil, note the colours and record where it was found.
3. Describe where different kinds of soil are found and why they are found there. What kinds of plants are growing on them Are soils good for gardens
Extra Activity
Dig soil profiles in a new garden, old garden, in a forest and on a steep slope. What differences do you see? Make a table and record your observations.
5.35 Fertilizer trial
Be able to set up a fertilizer trial to test whether fertilizer makes crops grow better.
You will need: Piece of land already dug, wooden pegs. Ask an agricultural officer for advice on which fertilizer to use for a trial. Use corn seeds or pineapple suckers or other planting material.
1. It is important to do experiments in agriculture. One kind of experiment is the fertilizer trial. The fertilizer trial is designed to try out different kinds of fertilizer in different amounts to see if fertilizer makes crops grow better.
2. Show how to mark out with wooden pegs the corners A. B. C. D and the mid points I, II, III, IV. The rows should all be the same size. The seeds or cuttings should be all planted the same distance apart in the rows.
3. Fertilizer is applied to the experiment plots A and D. No fertilizer is applied to plots B and C called control.
4. Draw the trial in an exercise book, write down the date.
5. Compare the crops in A and D with plots B and C plots. Does the fertilizer improve the crop yield?
Extra Activity
Set up a long-term fertilizer trial using tree crops. The plant nutrients are divided into:
1. Primary Plant Nutrients. They are nitrogen N, phosphorus P, and potassium K. (Potash is potassium oxide). One or more of these usually limits the yield of a crop, i.e. if there were more of this plant nutrient in the soil, the yield would be greater. These are the most important plant nutrients. They make from 2-6% of the dry weight of plants.
2. Secondary Plant Nutrients. They are sulfur S, iron Fe, calcium Ca and Magnesium Mg. These are needed in smaller amounts than the primary plant nutrients for normal growth. There is usually enough of these in the soil for good crop yields.
3. The micronutrients (sometimes called trace elements) are boron B, chlorine Cl, cobalt Co, copper Cu, manganese Mn, molybdenum Mo and zinc Zn. These are needed in very tiny amounts for the normal growth of some plants. If a soil does not have enough of a particular plant nutrient, e.g. nitrogen, you say that the soil is deficient in nitrogen. The only sure way to find out whether a soil is deficient in any plant nutrients is to ask a field officer of the Department of Agriculture to send some soil to a laboratory for chemical testing. However, you can tell if the soil is deficient in plant nutrients by examining your crop plants carefully. If a plant does not look healthy because there is not enough plant nutrient you say that it shows deficiency symptoms.
5.35.1 Deficiency symptoms:
1. Nitrogen N
The plants are small with few leaves that are pale green or yellow. The lower leaves look burnt and die early.
2. Phosphorus P
The plants are small and do not grow well. The leaves are a blue-green colour and are usually purple underneath. The lower leaves die early. They take a long time to produce fruit that are small and badly shaped.
3. Potassium (potash) K
The plants have small main shoots but many side shoots. The leaves have dead white areas on the leaf edges and later die.
4. Sulfur S: The plants are small with pale green upper leaves.
5. Calcium Ca
The plants are small with unusually shaped leaves. The shoot tips may die.
6. Magnesium Mg
The leaves have green veins but are pale yellow between.
7. Iron Fe
The younger leaves look yellow. the lack of healthy green colour in the leaves is called chlorosis and this may be due to a deficiency in one or more plant nutrients.
5.36 Cover crops
See diagram 6.65.4: Centro, Siratro, Puero
Be able to name which plants are suitable for cover crops or green manure and explain how they improve the soil.
You will need: Actual specimens of common plants used for cover crops and green manure. Before the lesson obtain diagrams or specimens of the different plants used and find a place in a garden or plantation nearby where plants are growing. You should ask an agricultural officer to show you how to prepare these seeds or cuttings for planting. Some should be inoculated with a special Rhizobium mixture before planting.
1. Draw a diagram of a bed of soil on the chalk board. Hold your arm above it.
What would my arm protect the soil from? [Sunlight, rain.]
Why should you protect the soil from sunlight? [If the soil is too hot: 1.1 Humus is lost, 1.2 Some seeds cannot germinate, 1.3 Water is lost from the soil.]
Why should you protect soil from rain? [Heavy raindrops make the soil splash up then get washed away.]
2. What can you use to protect the soil? Can you use sheets of iron? [No.] Can you use trees? [Yes, but when the trees grow big they will use most of the light and water so you can't grow other crops.] You use plants that do not grow high but cover all the ground with lots of leaves. You use legumes called Puero, Centro and Calopogonium. They are called legumes.
3. Legumes will: 3.1. Lower soil temperature and evaporation of water, 3.2 Protect soil from splash erosion but let water trickle down into the soil
3.3. Shade the weeds so they cannot grow, 3.4 Add humus and nitrogen fertilizer to the soil when the leaves die.
Can plants cause problems? [Yes, they can grow all over young coconuts, so clear a circle around each palm.]
4. If you are not using land for some time, such as during the school holidays, you can protect the soil and keep weeds out by planting legumes. However, clearing plants is hard work. If you plant an upright legume such as cow pea or mung bean, you can easily dig them into the soil. This is called green manuring. About 3-6 weeks after digging, the plants rot in the soil and the plant foods will be available for their next crop.
5. Show the legume plants and let the children feel the soil under a cover crop.
Extra Activity
Sowing a of green manure. Note that Centro has hard seeds that take a long time to germinate unless you treat them with boiling water. Puero and Calopogonium grow well in shade under leaves. You cannot dig in green manure crops under tree crops because it would damage the roots. Other good legumes are Hetero and Siratro that produce good grains for cattle and Stylo that is good at smothering weeds.
5.37 Rain on slopes 1
See diagram: 24.4.5
Be able to describe what happens when water falls on different slopes.
You will need: 1.1 One to four jam tins with holes punched in the bottom, 1.2 a soil ridge that is flat on top, has one side sloping steeply and the other side sloping gradually, 1.3. spades. Teach this lesson outside in the garden.
1. Show to how to make two ridges that are flat on top. One ridge has steep sides and the other has gradual sloping sides. There should be no plants or stones on the ridge, only fine soil.
2. Give each group a tin with holes in the bottom. Show how to fill the tin with water and make artificial rain.
3. Make rain on the gradual slope. Tell the children what happens. [Some water just soaks into the soil, some water runs down the slope and carries some soil down making a gully.]
4. Make rain on the steep slope. Explain what happens. [Much soil is carried down the slope to make a big gully.]
5 . Where should you make gardens? [On flat ground or else the soil will be washed away.]
Extra Activity
Do the same but cover the soil with grass. Grass stops the soil from being carried away.
5.37.1 Rain on slopes 2
Be able to explain what happens when rain falls on different soils and different slopes.
Use a tin with holes punched in the bottom, different types of land, and soil in two boxes. Practice the recommended activities of making "rain" well ahead of the lesson. Observe slopes and erosion.
1. Let the children practice making "rain" using tins.
2. Shake the rain on a slope covered in grass. What happens to the soil? [Nothing, it is not washed away.]
3. Shake the rain on sloping soil containing grass, leaves and sticks. What happens to the soil? [Some of it is washed down.]
4. Shake the rain on a slope of fine soil. What happens to the soil? [Most of the fine soil is washed away.]
5. Put the boxes of soil on slopes and shake the rain on them. What do you see? [More soil is washed down by the rain on the steep slope.]
6. When soil is washed away, this is called erosion. Erosion can be controlled by: 6.1 Keeping soil covered, 6.2 Not digging sloping soil, 6.3. Contour banks across slopes.
Extra Activity
How village people try to stop erosion in their gardens.
5.38 Mulch garden soil
See 6.9.14: Composting
Be able to mulch garden soil
Use a sloping garden bed. Cover half with mulch and leave the other half not covered. After about one month you should see the following differences: Feel the bare soil and the soil under the mulch. What differences do you see and feel? Are there any weeds under the mulch? Mulching is a thick layer of leaves, dry grass, or husks over the soil. It controls weeds by shading the students from sunlight. It absorbs and stores rainfall and lessens evaporation from the soil. Mulching protects the soil from the splash erosion of heavy rain drops. Mulching should not touch the stems of plants if the mulch may contain pests and diseases. Mulching must be replaced as it rots into the soil. Dry grass mulch or dry compost which is not rotten may take nitrogen plant nutrient out of the soil.
Mulched Soil Not Mulched Soil
Cooler soil Warmer soil
Damper soil Dryer soil
Less soil erosion More soil erosion
Darker coloured topsoil (more organic matter) Lighter coloured topsoil (less organic matter)
Fewer weeds (but mulch itself may contain weed seeds) More weeds
1. Mulch is chopped grass, weeds, leaves and other plants which acts as a blanket layer over garden soil. Mulch is not mixed into the soil but as it rots it enters the soil. As the mulch slowly rots into the soil new plant material should be added on top of the mulch. The garden should always be completely covered with 5 cm of mulch leaving no bare patches on the soil. The mulch should not touch the stems of crop plants because some pests and diseases may be in the mulch which could attack the plants. You can also use black plastic. The cover of dead plants is called mulch.
2. The advantages of mulching garden beds are as follows: 2.1. It controls weeds because the mulch stops light getting to their leaves. 2.2. It stops rainfall from washing away the soil. 2.3. It stores water which the plant can use in the dry season. 2.4. It stops loss of water from the soil into the air because the mulch is like a blanket over the garden bed. 2.5. The mulch rots slowly into the soil to improve the soil structure.
3. Disadvantages of mulching garden beds are as follows: 3.1 It requires more work to collect, cut and put plant material on the soil. 3.2 The work is often not done properly leaving bare patches. 3.3 When the bottom layer of the mulch rots it may take some nitrogen plant nutrient from the soil. 3.4 Insect pests and disease may live in infected plants used for mulch.
4. Before mulching school gardens always ask an agricultural officer whether it is safe to use mulch with crop plants.
5.39 Make clay pots
Be able to make a pot from sand and clay.
Use fresh sand and different types of clay, banana fibre, round stones, fuel wood. About a week before the lesson, collect the same amount of red clay and washed sand. Mix them in equal parts by pounding with a wide stick. Wrap it in banana leaves to keep it moist.
1. Explain that this method of making pots is very old and is still is in some parts of the world.
2. Give each group a lump of damp clay. Divide it into four smaller pieces. Flatten each lump with a round stone.
3. Twist the banana fibre to make a hoop for a stand.
4. Mould one piece over a stone to make the bowl shape. Put this on the hoop. Add flat pieces to build up the walls, keeping the stone inside. Cut the lip smooth with a coconut fibre and smooth the edge with wet fingers, take the stone out. Write your name in the side with a small stick.
5. Leave the pot to dry for 1-4 weeks.
Extra Activity
Firing the pot: Get lots of little softwood sticks. Put the pot on top of some, then build a house of sticks all around the pot. Set fire to the house of sticks. Encourage the children to visit different locations where pots are made from clay.
5.40 Make potash from ash
Be able to obtain potash from wood ash.
Use lots of white wood ash from burning large pieces of wood until only the soft ash is left. Glass jars or bottles. Filter paper or any soft paper or cotton wool. Filter funnel empty coconut shell with a small hole in it, burners and burner stands or a small fire.
1. What you got when you burnt wood. [Carbon.] How you do you make ash? [By burning wood in a very hot fire.]
2. Put the ash in a beaker or jar so that it is half full. Put some water in and stir up the ash and water very well. Filter the liquid from the jar into another jar or bottle. Put some filtered liquid on a tin lid. Heat the liquid so that it evaporates. What is left? [Some white substance.]
3. What does the white substance taste like? [Salty.] Where does the white substance come from? [The wood ash.] The wood ash contains something like salt called potash. Potash is a very good fertilizer for the gardens.
4. What kind of substance you found in the wood lesson. [Carbon.] Where does the wood get the salty substance from? [From the soil.]
5. If the people near their school get salt from ash.
Extra Activity
How you can test whether potash is a good fertilizer or not. [Fertilizer trial.]
Sentence Completion: Wood burns to form [carbon] and [potash]. Trees get [potash] from the soil.
5.41 Keep water clean
Be able to explain how to keep water clean for humans, animals and plants.
Use sample of pure drinking and polluted water, examples of purifying processes. Before the lesson visit a local source of drinking water or a river and the seashore. Note where the water is clean. Use samples of good drinking water and smelly polluted water that is unfit for drinking. Bring some rubbish found in a river or on the seashore.
1. Show the good samples of good drinking water and water unfit for drinking. Tell them to look at the samples, smell them and tell you the difference. Why do you need clean water? [Dirty water can make us sick.] Explain that dirty water can contain bacteria that make us sick. Bacteria are so small that you cannot see them with your naked eyes. You need a microscope to see them.
2. How can you be sure that water is clean and will not make us sick?
2.1. Boil water for babies.
2.2. Drink rainwater.
2.3. Drink clean water from wells or rivers.
2.4. Drink clean water from treated sources.
3. How you can you make clean water dirty:
3.1 Throwing rubbish or dead animals in the river.
3.2 People putting their faeces or urine in the river. Toilets must be 20 metres from the river otherwise bacteria from sick people can get into the water.
3.3 Chemicals such as insecticides and weedicides can wash into the river from sprayed crops. Soil can wash into the river to make it muddy.
4. How you can keep rivers clean:
4.1 Bury all rubbish.
4.2 Build toilets at least 20 m from the river and at least one metre deep.
4.3 Do not let agricultural chemicals wash into rivers. Bury unused chemicals.
4.4 Use contour banks to stop soil washing into rivers.
4.5 Do plants and animals in the rivers and sea need clean water? [Yes.] How can dirty water hurt them? Disease and chemicals can kill them. Muddy water and rubbish stop them getting light. Muddy water can kill coral. Plastic rubbish can kill some fish if they eat it.
Extra Activity
1. Visit a pig latrine. Is it 20 metres from a river, houses, pig yards, wells? Is it more than one metre deep? Does it have a cover? Are there any flies around it?
2. Visit a river. Is there any rubbish in it? Is muddy water caused by garden soil washing into it? Can chemicals get into it?
3. Visit the seashore. Is the water muddy? Can animals and plants live in the muddy water? Collect the flotsam washed up on the beach. How did it get there? Does it contain plastics? Plastics do not rot quickly and remain rubbish for a long time.
5.42 Heated air expands
See diagram 20.1.1: Heated air expands
Be able to describe what happens when a bottle is heated and then cooled. Can explain that air expands when heated and contracts when cooled?
Use a bottle, plastic tube from ball pen, burner, glass jar. Be careful! This experiment is dangerous if you heat the bottle too much. First do the demonstration in a preparation room before doing it in front of children. Strict adherence to instructions is very essential here if accidents are to be avoided.
Method: Demonstration preferred
1. Give out the materials and tell the children to push the ball pen tube into the hole in the cork, push the cork into the mouth of the bottle so that no air can leak out around the side of the cork, hold the neck of the bottle with a piece of rag or paper and tip the bottle so that the end of the tube is about three cm under the level of the water in the tin. eat the bottle gently with the burner for a few minutes and watch what happens. [Bubbles come out of the tube in the water.]
2. Stop heating the bottle. Put out the burner flame. Keep the end of the tube under the water and watch what happens as the bottle cools down. [Water is sucked into the tube.]
Extra Activity
Explain why it is dangerous to heat closed bottles or gas cylinders because when gases are heated you expand. If expansion occurs very quickly this is called an explosion.
Sentence Completion: When the air is heated it [expands]. When air is cooled it [contracts].
5.43 Burn to make carbon
Be able to show that all living things contain carbon.
Use a candle or burner, old torch battery from a radio, paper, pencil, dry leaves, insects, sugar, food, tin lids, iron nails, tongs or a holder to hold nails in the fire. In this lesson you will burn a variety of materials that are alive or were once alive and in each case you will show that when the burning is completed only carbon is left. Carbon is an element represented by the symbol C. Oxygen is represented with O. If carbon is heated to a very high temperature, it can form the gas carbon dioxide or CO. So if you heat the substances in this experiment to high temperatures you would not have any carbon left, it would all have turned into carbon dioxide gas. Break open the battery and take out the black rod in the middle. Dig a hole outside where there is good topsoil containing plenty of black humus.
1. Give out the candle or burner, tongs and things to be burned. Hold a tin lid in the candle flame. Cool the lid then wipe off the black stuff called soot. Explain that this black stuff is called carbon. Put some carbon on your fingers.
2. Make a pencil mark on paper then rub your finger on it. The black mark on your finger is carbon.
3. Show the black rod in the centre of the battery. It is carbon.
4. Burn paper, an insect, piece of meat or sweet potato. What happens to them? [They become black.] What is the black stuff? [Carbon.]
5. Heat up some sugar on a tin lid. What happens to the sugar? [It burns to form carbon.]
6. Take the children outside to the hole. How is the topsoil different from the subsoil? [It is darker.] What is in the topsoil? [Rotten plants and animals.] Why is it black? [The rotten plants and animals become carbon.] Explain that the substance from rotten plants and animals that contain carbon is called humus.
Extra Activity
1. Take a piece of burnt wood, it is called charcoal. Heat it until it glows red. Why does it get smaller? [The carbon is changed into carbon dioxide gas.] Relate this to what happens in a charcoal pressing iron and when used for cooking locally.
2. Burn some feathers or hair. Carbon is formed but there is also a strong small. The smell comes from another substance called sulfur S, which burns to form the gas sulfur dioxide, SO2.