Function of Rhizobium nodules on roots of legumes

School Science Lessons
(Foodgardens3)
2025-08-01

Composting Plant fertilizers
Contents
9.1.0 Composting, humus
9.2.0 Plant fertilizers
9.3.0 Plant growth regulators
9.4.0 Plant nutrients from plant ash

9.1.0 Composting, humus
Composting (websites)
9.1.1 Carbon / nitrogen ratio of compost
9.1.2 Compost and composting
9.1.3 Compost inspection
9.1.4 Humus from composting
9.1.5 Organic materials for composting
9.1.6 Three methods of composting
9.1.7 Worm farms for composting
9.1.8 Smart worm farm

9.2.0 Plant fertilizers
9.2.1 Chemical plant fertilizers, plant fertilizer trial
6.38 Chemical fertilizers (Primary)
9.2.2 Fertilizing with plant fertilizers
9.2.3 Grade formula of artificial plant fertilizers, blended fertilizers
9.2.4 Gypsum plant fertilizer, Tests for gypsum added to the soil
9.2.5 IBDU plant fertilizer
9.2.6 Liquid ammonia and anhydrous ammonia plant fertilizer
9.2.7 Liquid manure plant fertilizer
9.2.8 Mixed or compound plant fertilizers
9.2.9 Muriate of potash, KCl, plant fertilizer
9.2.10 Organic gardening plant fertilizers
9.2.11 Seaweed extract plant fertilizers
9.2.12 Straight plant fertilizers, simple plant fertilizers, NPKS
9.2.13 Straight plant fertilizers and mixed plant fertilizers

9.3.0 Plant growth regulators
9.3.1 Abscisic acid, (ABA) 9.3.2 Auxins
9.3.4 Cytokinins
9.3.4 Daminozide
9.3.5 Ethylene gas. Abscission
9.3.6 Gibberellins
9.3.7 Naphthalene acetic acid

9.4.0 Plant nutrients from plant ash
See diagram: 6.65.1: Soil nutrients cycle 1
See diagram: 6.65.2: Soil nutrients cycle 2
See diagram: 6.65.3 Nitrogen cycle
Collect some white ash from burnt wood and bring it to the classroom.
The black ash is carbon.
Show the students the white ash you have collected. Let them taste some.
It tastes a bit salty.
The ash contains plant nutrients.
Show the students a bag of fertilizer let them read the names written on the bag.
Do not let the students taste the fertilizer from the bags.
Plant nutrients are chemicals that plants take in from the soil.
Some people call them "plant foods".
These chemicals are needed by the plant to keep it alive, to make food, and make the plant body.
If there are not enough plant nutrients in the soil, the plant will be weak, grow slowly, have yellow or brown leaves, and may die.
The most important plant nutrients are as follows:
1. Nitrogen for plenty of strong green leaves
2. Phosphorus for root growth and making fruit
3. Potash (potassium oxide) for healthy plants
Other important plant nutrients are as follows:
4. Sulfur and iron for green leaves
5. Magnesium and calcium for healthy plants
There are other plant nutrients needed in very small amounts, which may be important for some plants, e.g. manganese, boron.
Most plant nutrients originally come from the rocks that formed the soil.
Other plant nutrients in the soil have come from plants that have died then rotted in the soil.
If a soil does not have enough of any plant nutrient, e.g. potash, it is said to be deficient in potash.

9.1.1 Carbon / nitrogen ratio of compost
The organic material must have a suitable carbon / nitrogen ratio.
The bacteria and fungi that make the compost need certain amounts of both carbon and nitrogen nutrients.
If there is too much carbon and not enough nitrogen they will breakdown the material slowly, and the compost made may take nitrogen nutrient out of the soil.
, This loss of nitrogen nutrient is called "nitrogen draw down".
If there is not enough carbon and too much nitrogen much the nitrogen will be lost as ammonia gas.
So a compost heap should contain a mixture of high nitrogen material and low nitrogen material.
Sawdust, rags and paper have very low amounts of nitrogen and should not be used, unless they have been left out in the rain for a long time.
Adding urea or sulfate can increase the nitrogen in the compost.
Do not add lime to compost heaps, because it increases the loss of nitrogen as ammonia gas.
How much nitrogen in composting materials:
Very high nitrogen: chicken and pig manure, urine
High nitrogen: deep litter, fish scraps.
About right nitrogen: waste food, fruit and vegetable peelings, seaweed.
Low nitrogen:, cut grass, weeds, crop residues.
Very low nitrogen:, leaves, sawdust, rags, paper.
Composting may decrease the nitrogen plant nutrient if the compost is not made properly and there is too much carbon and not enough nitrogen in it.

Approximate values of the Carbon / Nitrogen ratio, [C / N ratios]
The ideal ratio is 20-30 parts of carbon to one part of nitrogen.
Material with too much carbon has a slow decomposition and seems to just stays there, e.g. sawdust.
Material with too much nitrogen has a quick but smelly decomposition.
The excess nitrogen may be converted to ammonia which dissipates into the air, e.g. wet green grass clippings.
List of C / N ratios: Sawdust < 500:1, Paper 170:1, Straw 100:1, Leaves < 80:1, Bagasse (sugar cane residue) 50:1, Seaweed 25:1,
Horse manure 25:1, Legume or grass hay 25:1, Rotted manure 20:1, Grass clippings 20:1, Leafy green weeds 20:1
Food waste 15:1, Humus l0:1, Poultry manure 7:l, Blood and bone manure (commercial product): 7:l, Fish waste 5:1.

9.1.2 Compost and composting
Compost is decomposed organic matter, including leaves, twigs, grass and kitchen scraps, but not meat.
When compost is ready for use in the garden, it is dark and soil-like, with none of the original ingredients distinguishable.
Although is us broken down, it could decompose further in later years.
Composting
1. Before teaching this lesson, ask a field officer from the Ministry of Agriculture about compost heaps.
In some places, the Department of Agriculture does not approve compost heaps, because they can be home for insect pests, e.g. the rhinoceros beetles that attack coconut.
Composting speeds the natural processes of rotting under controlled conditions using organic material, micro-organisms, moisture and oxygen.
This rotting process provides plant nutrients for the crops in the gardens.
When an animal or plant dies, bacteria and fungi breakdown the chemicals in them into simpler chemicals and gases are given off.
This process is called rotting or decomposition.
Bacteria and fungi can convert these simpler chemicals to complex organic compounds, e.g. humus, that can return to the soil as plant nutrients and be used by plants again.
Composting is a natural way of fertilizing, but composting may bring weed seeds and pests into the soil.
2. When preparing for composting the headmaster must decide on a school policy that ALL waste materials should be saved for the compost heaps.
In the kitchen, peelings and food scraps are all saved and kept separate from rubbish, e.g. tins and boxes.
A few bashed iron tins may add iron plant nutrient to the compost or be used to trap air in the compost heap.
No student is allowed to burn heaps of dead leaves, cut grass, or weeds, because all this material must be taken to the compost heap each day.
Two students are appointed to look after the compost heaps every day during school maintenance time.
3. Select a well drained area of soil fairly near the kitchen and kitchen gardens, but remember that most compost heaps smell a bit.
Dig up the soil to loosen it.
You will need a shelter with a roof of leaves which will protect the compost from the sun and heavy rain but allow some water to drip through.
You may need to put up a fence to keep animals away.
4. The bottom layer of the compost heap should be coarse material, e.g. plant stems, placed on the soil.
This allows air to move up into the heap and also allows earthworms to come up into the heap from the soil.
Most people then build up a heap in layers of high nitrogen and low nitrogen material:
first soil then corn stalks,
then sweet potato peelings,
then cut grass then kitchen scraps,
then cut weeds,
then old bean plants,
then pig manure,
then dead leaves,
then cut grass.
The heap should be about one metre x one metre in area and one metre high.
Some people add a top layer of five cm of soil or you cover the heap with old bags or black plastic to keep off flies and keep in bad smells.
If the material is chopped up before adding to the heap, the compost will be made more quickly and will be better for the garden.
There are some compost making machines that chop the plant material.
Do not add paper, rags, sawdust, tea leaves, or pesticides to the compost heap.
Do not add tufts of grass with the soil sticking to the roots, this will make the compost heap hard to turn and will keep out the air.
5. The compost heap should be sprinkled with water to give the right amount of moisture.
To test for this, take a handful of compost from inside the heap and squeeze it, a few drops of water should come out.
The heap is too dry if you cannot squeeze out water and there is a lot of greyish dust from fungus.
The heap is too wet if the compost is sloppy and has a bad smell.
6. To make good compost the heap must be turned over with a fork to mix all the materials together and let in the air.
The heap will become quite hot due to the activity of the bacteria and fungi.
Turning the compost will also kill weak seeds and insect pest.
If the temperature of the heap rises above 60^oC the bacteria and fungi) may die but the temperature may be kept down by more turning or making smaller heaps.
Dry grass mulch or dry compost, which is not rotten, may take nitrogen plant nutrient out of the soil.

9.1.3 Compost inspection
Examine the heap every week to see what happens to the material in the compost heap until dark coloured, crumbly, odourless compost is formed.
The compost is then ready to be put in the garden.
If they have not already planted the garden, placing the compost in the soil at the level of the plant roots is best.
Do not let compost touch the stems of plants.
1. Moisture: Below 40% moisture decomposition does not occur.
Above 60% moisture you reduce airflow and the compost heap becomes anaerobic.
The best moisture content is 55% moisture so that the compost feels damp like a squeezed sponge.
You can sprinkle the compost heap with water to give the right moisture content.
To test for this, take out a handful of compost from inside the heap and squeeze it.
A few drops of water should come out.
The heap is too dry if you cannot squeeze out water and there is much greyish dust from fungus.
The heap is too wet if the compost is sloppy or soggy and has a bad smell.
2. Temperature: After 2 to 3 days the bacteria and fungi generate heat and the temperature rises to 55^oC to 60^oC.
Bigger heaps get hotter than smaller heaps.
If the temperature of the heap rises above 60^oC the bacteria and fungi may die.
To make good compost, you must turn over the heap with a fork to mix all the materials together and let in the air.
The heap will become quite hot due to the activity of the bacteria and fungi.
Turning the compost will also kill weed seeds and insect pests.
However, the temperature can be kept lower by more turning or making smaller heaps.
3. pH: The pH of plant material is originally slightly acidic from the pH of the cell sap.
During fermentation in the compost heap the acidity increases and the pH drops.
When the compost heap becomes hot due to fermentation, ammonia is produced, the pH rises and the compost heap becomes alkaline.
The conversion of ammonia to protein and buffering action of humus results in a neutral pH.
Do not add lime to the compost heap, because ammonia will be lost.
4. Bacteria and fungi: At first the acid producing bacteria and fungi decompose the sugars, starches and amino acids.
Later, high temperature bacteria decompose proteins, fats and hemicelluloses.
The high temperature fungus (Actinomyces) can decompose cellulose to give a grey white colour from the white spores.
The high temperature in the compost heap kills weeds and parasites.
Most carbon is converted to carbon dioxide and is lost as gas such that the dry weight and volume of the compost heap may reduce by about 50%.

9.1.4 Humus from composting
1. Humus is dark organic matter that is the product of decompose pant or animal material.
Soil bacteria and fungi turn plant organic matter into a dark form of organic matter called humus that has a complicated chemical composition.
Humus includes humic acids, fulvic acids and miscellaneous dark organic compounds called humin.
Humic acids are dark brown to black complex aromatic molecules linked together by amino acids, amino sugars, peptides and aliphatic compounds.
Fulvic acids are yellow brown aromatic compounds linked to aliphatic compounds.
Natural grassland compost is mainly humic acids and natural forest compost is mainly fulvic acids.
Composting puts plant nutrients in the soil that the plants can use easily, improves the soil structure, and allows the soil to store more water.
Also, it is a cheap way of fertilizing the soil.
Soil organic matter includes decomposing plants, animals and animal waste products and products of this decomposing process.
Humus is the fully decomposed organic matter.
Organic matter is a source of plant nutrients.
When broken down, organic matter can hold on to water and nutrients, and stop nutrients from being leached away.
Organic matter improves soil structure.
Organic colloids bind individual mineral particles together into soil aggregates.
They allow more water to enter a clay soil and improve the water holding capacity of a sandy soil.
Crop residues and trash from previous crops retained on the surface of the soil help to control soil erosion.
Loss of organic matter is caused by continuous cropping, removal of vegetation, e.g. hay, burning crop stubble, too much cultivation.
2. Organic matter can be added to the soil by:
adding animal manure,
growing a green manure crop and adding cow pea, mung bean, buckwheat, millet, soybean, fava bean, fenugreek, lupins, woolly pod vetch.
resting an area of soil from cropping, e.g. crop rotation.
Rotate crops with a pasture phase to allow both build up of surface cover and an increase in soil organism numbers.
Soil organisms are responsible for the breakdown and final decay of organic matter.
The larger organisms, e.g. earthworms, eat organic matter and so speed up the breakdown process.
They also make tunnels through soil by which water and air can enter.
Soil bacteria and fungi may use each other's waste products so that nutrients are passed around and made available to plants.
Decomposers breakdown dead plant and animal material to simple substances that can be used as nutrients by living plants.
Nitrifying bacteria convert ammonium produced during decomposition into nitrates in the soil.
Nitrogen-fixing organisms that convert nitrogen in the soil air into nitrates include Rhizobium nodules on the roots of legumes and blue-green algae in wet soils.
However, some denitrifying bacteria in wet soils convert nitrates back into nitrogen gas and so make nitrogenous substances unavailable to plants.

9.1.5 Organic materials for composting
Collect plant and animal material, e.g. animal manure, fish scraps, food scraps, fallen leaves, cut grass and weeds, washed seaweed.
Do not use paper, rags, sawdust, wood, diseased plants, strong chemicals, insecticides, human wastes, i.e. urine, faeces, "night soil".
Do not use tufts of grass with the soil sticking to the roots, because this will make the compost heap hard to turn and will keep out the air.
To increase the speed of making compost, use "compost starters" that contain the needed bacteria, but these products are usually expensive.

9.1.6 Three methods of composting
1. Heap on the ground
Make compost heaps about 2 m × 2 m long and ×1 m high.
Build the compost heap by making layers of dead leaves, black soil, and some manure or other nitrogen containing substances.
Do this again so you have many thin layers one on top of the other.
Then water the compost heap to make it damp.
Then cover it with dead coconut leaves to keep the hot sun from making it dry.
After five weeks, turn the compost layers over onto another place.
Mix up all the layers.
Then water it again and cover it with coconut leaves.
After another five weeks, do this again.
In about three months the compost will be ready to use.
If it has been a dry time, it may take a little longer to be ready.
If you put meat scraps or dead animals in the compost heap, they will attract wild animals and birds and cause extra smells.
Some bacteria and fungi live better in the air and some live better without air.
Those that like air can produce compost quickly in heaps above the ground, but some nitrogen is lost as ammonia gas.
The bottom layer of the compost heap should be coarse material, e.g. plant stems, placed on the soil.
This allows air to move up into the heap and allows earthworms to come up into the heap from the soil.
Build up a heap in layers of high nitrogen then low nitrogen material, for example: 1. soil, 2. corn stalks, 3. sweet potato peelings, 4. cut grass, 5. kitchen scraps, 6. cut weeds, 7. old bean plants, 8. pig manure, 9. dead leaves, 10. cut grass.
Some people add a top layer of 5 cm of soil or they cover the heap with old bags or black plastic.
This keeps off flies and keeps in bad smells.
If you chop up the material before adding to the heap you will make the compost more quickly and it will be better for the garden.
Some compost making machines chop the plant material.
You make the best compost in a heap that you turn over every three days for three weeks.
However, most people are too lazy to do this and use the bin method.
2. Bin method
Bins are walled heaps on the ground.
Build bin walls in the shape of the letter E with galvanized iron, wooden boards or chicken wire.
A chicken wire floor can let air in the bottom of the compost heap.
Another method is to cut the bins out of the side of a hill.
This provides three earth walls for each bin and a front door can be made of boards.
Fill the first bin with layers of material and cover with soil.
This may take about a week. One week later you fork the heap in the first bin into the second bin.
Use the fork to throw the material up lightly and let it fall into the second bin.
Cover the heap in the second bin lightly with soil.
Four weeks later turn the contents of the second bin into the third bin and cover with soil.
After another four weeks, the compost should be ready to put in the soil of the garden.
Start the compost heap in one compartment and every two weeks use a spade to turn all the compost into the other compartment.
In this way you regularly turn the compost and you have a neat storage system.
Concentrate green grass in a pit and seal it from the air, so the anaerobic bacteria decompose it to mainly lactic acid and acetic acid to produce pickled grass called silage, with pH 4-5.
Compost pits are not satisfactory, because there is no air for the aerobic bacteria.
3. Drum method
Cut the bottom out of an oil drum, or make a four sides bottomless bin using galvanized iron.
Put two logs on the ground, then make a platform out of pig wire or make a frame and attach chicken wire to it.
Stand the drum on the platform.
Plant material is added to the drum that can be used just like a garbage tin.
You will need a lid to keep in bad smells.
A plastic compost bin is a neater way of storing the composting, but it may smell, because of lack of oxygen.
You can use a small rake to try to turn the compost in the bin if it becomes smelly.
If you put meat scraps in the compost then the metal drum or plastic compost bin will stop animals making a mess in the garden.
Bacteria that do not like air can produce compost more slowly in pits below the ground or in bins, but the compost has a bad smell.

9.1.7 Worm farms for composting
See: Composting websites
1. A worm farm minimizes food waste by turning organic kitchen waste into liquid fertilizer and worm castings, the organic material digested by worms.
After about two months rich, dark worm castings will be building up and worm juice will start to accumulate at the bottom of the worm farm.
Worm castings, called vermicast, and compost are the best soil conditioners.
Castings should be dug into recently watered soil, or watered in when added.
If added in spring or summer, the area should be mulched straight after adding the castings.
They can be added to any area of the garden, including vegetable beds.
The worm castings fertilize the soil to encourage strong plant growth and healthier soil.
A handful of worm castings added to a watering can, stirred, and used straight away makes a great compost to be applied to the vegetable garden.
Worm juice, worm farm liquid, is the liquid that drains out of the worm farm and is said to be the richest liquid fertilizer known.
It is also worth collecting and spreading around the garden, although it is not as rich as the castings themselves.
When using worm juice, it is best to dilute it at least ten parts water to one part worm juice until it is the colour of weak tea.
2. Worms do not like the heat or direct sun so choose a cool shady spot inside or outside.
Worms like temperatures from 15^oC to 25^oC, so place the worm farm in a cool environment, out of hot sunlight and rain.
A worm farm should be double insulated to help in maintaining an even temperature.
Purchase a worm farm or make the worm farm out of recycled plastic, polystyrene vegetable boxes or wood, but treated wood can leach chemicals.
To prepare the worm farm for worms, the worms will need a bed inside their box.
It should be made out of good quality soil, leaves and shredded paper.
The worm bed should be around 15 cm deep.
Add a little water to the worm bed, because it needs to be kept moist, but not wet.
Remember to make sure the worms have enough bedding and that you keep the worm farm damp, covered and cool.
If you notice pests like slugs and vinegar flies once the farm is up and running, dust the top with lime and check you have not added too much food.
3. Buy the worms from commercial worm growers or the local nursery.
The common types are: Tiger, Indian Blue and Red Wriggle.
Worms are usually available by the thousand and you will need between 1, 000 and 2, 000 worms to start with, then they will multiply over time.
Settle the worms in by gently spreading them over the surface and watch them burrow into their new bed.
Th species of worms sold at a commercial worm farm include:
Tigers, (Eisenia fetida)
Reds, (Eisenia andrei)
Blues, (Perionyx excavatus) / (Spenceralia)
Gardeners Friend or Cod Worms (Amynthus)
European Night Crawlers or Catchall Crawlers, (Eisenia hortensis) or (Dendrobaena veneta)
This company includes up to 5 species of worms in its compost worms mix.
They do this because some species do better in warmer weather, while other species do better in colder weather.
4. Feed the worms
Worms do not have teeth, but they have an organ called a prostomium used for prying food apart.
They have mouths that slurp down food, a gizzard like a chicken that grinds the food and an intestine.
Worms are better able to eat food that has been cut into smaller pieces or liquidized.
Worms enjoy a variety of food and can eat their own body weight each day.
Only feed your worms when all of the previous food has been consumed.
Any left-overs will turn anaerobic causing bad odours, souring your soil and killing your worms as there is no oxygen for them to breathe.
Slowly increase the food as the population of your worm farm increases.
It is better to underfeed your worms than over-feed them.
Before feeding, fluff up the top 5 - 10 cm of soil with your gloved hands to allow air flow, prevent compaction and reduce odours.
Feed the worm farm every seven to ten days or when the previous food has been consumed.
Worms can consume kitchen greens, vegetable peelings, horse or cow manure,
tea bags and coffee grounds (staples and tags removed from tea bags), crushed eggshells,
small amounts of moistened and shredded paper, and cardboard, e.g. shredded egg cartons, contents of vacuum cleaner dust bags.
Chop up their food as small as possible so the worms will get through it faster.
Add the kitchen waste regularly in small amounts and in one place at a time.
Cover new food with a light cover of their bedding material or a handful of soil or compost.
For hard fruits and vegetables cut into small and thin pieces.
For soft pieces of fruit cut up and place face down.
However, excessive application feeding of fruit will increase the acidity (pH level) of the worm farm due to high sugar content.
Grind egg shells and cereals.
A regular sprinkle of oatmeal helps with protein levels.
Feed the worms once a week and only when they have almost finished their last meal or it will start to rot.
Do not feed the worms butter, cheese, meat, fish, fat, bones, citrus peel, onion, garlic, bread, potatoes, oils, salted food, pickled food, fresh grass clippings, sawdust.
Meat and dairy products attract vermin, flies and maggots.
Pineapple can kill the worms.
Worms need a pH level of between 5.5 and 7.5.
Worms do not live or breed well in acidic conditions that can be created by some fruits with a high sugar content or a diet high in fruit.
Use a simple pH soil testing kit once a month to learn and monitor the pH level in the worm farm.
Add baking soda or dolomite lime watered in to help raise the pH level and reduce acidity in the worm farm.
Dolomite lime is similar to garden lime, but contains more magnesium.
The contents of the worm farm must remain moist.
If the contents are too dry, the worms will perish.
If the contents are too wet, the worms will drown.
Most foods used in worm farm has a high moisture content.
Dry food such as paper will be soaked in water before applying.
When applying water, do it slowly and gently so it can percolate through the soil and collect valuable minerals.
A slow application will also provide least disturbance to the worms.
For a worm farm holding two litres of liquid, once a week drain and collect the liquid, and mix it at a ratio of 1:1 with rainwater to create the liquid fertilizer.
Replace the two litres of moisture with rain water using the process outlined above in the moisture section.
For best results, the harvested liquid should be used as soon as possible after harvest, as it contains living organisms beneficial to your plants.
Worm juice that is stored will lose its potency and benefits very quickly.
5. Harvest worm liquid and castings
If the worm farm captures worm liquid, empty the tray regularly using the tap.
To harvest the worm castings, move the worms' bedding to one side of the farm, add fresh bedding to the empty side; then wait a few days.
Most of the worms will migrate over to the fresh bedding.
Then you can take out the old bedding and use it on the garden.
It is okay to transfer some worms into the garden when you empty the old bedding.
You will also be transferring worm eggs, which will hatch in the garden and improve the soil.
Use the castings to improve soil quality and for fertilizing around plants.
You can also add a sprinkle of worm castings onto pot plants.
Dilute the liquid fertilizer.
A good handful in a nine litre bucket of water stirred really well can then be watered onto the plants.
If you have a backyard, build a compost heap or bin to make use of the remainder of the food scraps as well as the garden waste.
This means that they cannot generate their own body heat.
A worm farm is easier to work with if it is at waist height.
Empty the contents of your worm farm onto wet newspaper in full sunlight.
The worms will quickly burrow down to the newspaper to avoid the sun/warmth.
Wait for two minutes then start to scoop off the layers slowly, so work towards the base leaving a thin layer for the worms to remain in.
Place the harvested soil into a buck and cover with a moist towel to stop it from drying out.
Castings should be used soon, because they contain living organisms that will be beneficial to your plants.
Remove 50 per cent of the worm population and replace the polystyrene bits on the bottom, and cover with five cm of gravel and sand.
Prepare a mixture of mainly manure, vermiculite and palagonite and fill the container up to within 5 centimetres below the air holes.
6. Worm problems
If you are going on holidays, worms can survive for 3 to 4 weeks.
Oatmeal will last longer than any other food and will not affect the pH level.
If a worm farm is too wet, remove three handfuls of soil (minus the worms) and replace with three handfuls of vermiculite and cow manure.
If the worm farm is smelling, check the pH level.
Overfeedinq is a common cause of bad smell, so remove uneaten food and add some soil and potting mix.
If the worms are trying to escape the worm farm, check the pH level, check for overfeeding, and check for exposure to heavy rain.
If ants invade the worm farm it may be may be too dry, so add water.
To control ants, raise the worm farm off the ground and smear Vaseline on the base.
If flies, maggots, and cockroaches enter the worm farm, they are attracted to rotting food, so do not overfeed and ensure that all food is consumed and that the worm farm is not too wet.

9.1.8 Smart worm farm
The wonders of worms for campus kindergarten children.
University of Queensland Campus Kindergarten children have made some new animal friends lately thanks to their smart worm farm, and environmental education.
The farm is part of research initiatives, which explore various ways of using "the Internet of Things" technologies, (a concept of connecting any device to the internet).
The project involved making a "smart" worm farm that is sustainable as well as functional.
The farm's key features include an automated hydration system, temperature and moisture sensors, an infrared (IR) camera a web app, and the farm runs on solar power.
The hydration system is connected to a tap via a hose and sprays water into the farm to make the farm more self-sufficient and keeps track of water use.
Data sensors are used for the watering system, and are also useful for ensuring that the farm provides an optimum environment for the worms.
The farm's IR camera snaps photos every hour, allowing the children to keep track of their new friends and learn about what the worms do down in the soil.
Worms are pretty sustainability savvy, because they eat most food waste and process it into nutrient-rich plant food, and worm castings are excellent for plant health.
The feed the worms food scraps and use the farm compost in their own Campus Kindergarten veggie garden.
These activities give them valuable insight into caring for the environment, recycling and reducing food waste.
The children are also responsible for looking after and harvesting the veggie garden, which will eventually be used for kindergarten cooking activities.
Children are hands on, they love the feel of the worms in their hands, but they ask is how worms see underground and what they actually do in the soil.
With the camera, the children can observe the worms and have a better understanding of how the worms live under the soil.
All of this helps inform the children's understanding of the environment and the importance of sustainable practice, as well as building other key life skills.
Their ability to take ownership of the worm farm through feeding the worms, measuring how much the worms have eaten,
and observing them through the camera helps them develop their problem-solving, curiosity, imagination and confidence.

9.2.1 Chemical plant fertilizers, plant fertilizer trial
1. Chemical fertilizers are made in factories.
Some are made from naturally occurring minerals, and are later ground to a powder and with chemicals, e.g. ground rock phosphates and superphosphate.
Other fertilizers are chemicals in chemical factories, e.g. sulfate of potash (potassium sulfate).
2. Some people think that students should not be learning about imported fertilizers.
Many tropical soils are lacking in certain plant nutrients, e.g. potash, and use of a small amount of these fertilizers can greatly increase the yield of the food crops.
Imported fertilizers are costly, but if they are used according to the recommendations of the Department of Agriculture, and are stored properly, they should pay for themselves in the increased value of the crop yield.
3. Do some fertilizer trials.
Then you can make your own decision about whether it is cost effective to buy and use imported fertilizers.
A good design for a fertilizer trial is as follows:
| Block 1 | Block 3 |
| Block 2 | Block 4 |
In each block plant 20 cuttings of potato.
Blocks 1 and 4 are experimental blocks.
Put one teaspoon full of fertilizer in the soil around each cutting.
Blocks 2 and 3 are control blocks, so do not use any fertilizer.
Harvest each block separately and weigh the potato.
Compare the weight of potato from Blocks 1 and 4 with the weight from Blocks 2 and 3.
Compare the value of the harvests if they were sold.
It pays to use fertilizer if the use of fertilizers can at least double the yield, i.e. weight of blocks (1 + 4) / weight of blocks (2 + 3) / 2.
4. Use fertilizer to make a profit.
Profit = (returns from Blocks 1 and 4) to (returns from Blocks 2 and 3) to cost of fertilizer used.
Cost of fertilizer in bags = (cost of fertilizer + freight) × (weight of fertilizer used / weight of whole bag of fertilizer)
5. Read the description of contents on a bag of fertilizer:
The name of the factory that made it, e.g. CFL Consolidated Fertilizers Limited,
The weight of the fertilizer, e.g. 50 kg,
The grade formula, e.g. NPK 12:4:19.
This means that 100 grams of the fertilizer contains 12 grams of nitrogen, 4 grams of phosphorus and 19 grams of potassium.

9.2.2 Fertilizing with plant fertilizers
Adding fertilizers by broadcasting, banding, top-dressing, side-dressing
The 4 methods of adding fertilizer to the soil:
1. Broadcasting
The fertilizer is spread over the surface of the soil by hand or by machine.
It should then be dug into the soil using a hoe or plough, because, if left on the surface, nitrogen plant nutrient may be lost as ammonia gas.
Fertilizer dug into the soil about 2 weeks before the crop is sown is called a base-dressing.
2. Banding
The fertilizer is placed below the surface of the soil by hand or by machine.
A furrow is dug between the rows of seeds at a depth of about 2 cm deeper than the seeds, the soil is then turned to cover the band of fertilizer.
Banding is done at about the same time as the seed is sown.
3. Top-dressing
The fertilizer is spread after the crop has been sown.
This is usually done with nitrogen fertilizer to provide extra plant nutrient at certain times to make more shoots and leaves.
Nitrogen plant nutrient may be easily washed out of the soil.
Add some of the fertilizer by banding at sowing time and add the rest by top-dressing when the shoots and leaves are growing.
4. Side-dressing
The fertilizer is placed between the rows by banding or placed under the plants and watered in after the crop has been growing for some time.
This is done for maize (corn), vine crops and tree crops to increase the yield of fruit.

9.2.3 Grade formula of artificial fertilizers, blended fertilizers
A fertilizer containing 13% N, 13% P and 21% K, then 100 grams of the fertilizer would contain 13 g N, 13 g P and 21 g K, the grade formula is NPK =13:13:21.
Other examples of the grade formula of artificial fertilizers:
Muriate of potash (NPK = 0:0:50), KCl, contains potassium and chlorine.
Superphosphate (NPK = 9:0:0),
Sulfate of ammonia (NPK = 21:0:0),
Urea (NPK = 46:0:0).
The term "potash" applied to mixed fertilizers refers to "K2O equivalent", but not to K2O itself, because it is not in a mixed fertilizer.
1. The contents of fertilizers are shown by a grade formula that uses the chemical symbols of the primary plant nutrients NPK.
This is used in two ways.
The old way listed the contents of potassium and phosphorus as their oxides.
2. Previous formula:
100 g fertilizer contains 13 g Nitrogen, 13 g Phosphorus oxide and 21 g Potash (Potassium oxide).
The fertilizer would be shown as: NPK = 13:13:21.
3. Current formula:
The current formula lists the contents as the elements nitrogen, phosphorus and potassium.
If the fertilizer contains 13% Nitrogen N 13%, Phosphorus P 21%, and Potassium K. 100 grams of the fertilizer would contain 13 g nitrogen, 13 g phosphorus and 21 g potassium.
The fertilizer is shown as NPK =13:13:21.
Examples of the NPK grade formula of fertilizers:
1. Muriate of potash | 0 N | 0 P | 5 K |
2. Superphosphate | 0 N | 9 P | 0 K |
3. Sulfate of ammonia | 21 N | 0 P | 0 K |
4. Triple superphosphate | 0 N | 20 P | 0 K |
5. Urea | 46 N | 0 P | 0 K |

9.2.4 Gypsum plant fertilizer
Tests for gypsum added to the soil
Gypsum, CaSO4·2H2O, may improve the structure of these soils: Slippery and sticky when wet, slump and get muddy during rain, form a crust on drying, and allow only slow entry of water.
Also, gypsum may benefit soils that do not break into anything smaller than large clods during digging.
To test whether a soil may benefit from gypsum, drop a 5 mm diameter crumb of dry soil aggregate into a beaker of deionized water.
Place a similar sample of the soil in the palm of one hand, add deionized water and knead the soil until all of the lumps have been broken up.
Squeeze some kneaded soil into an aggregate about 5 mm in diameter and drop it into a second beaker of water.
Observe the beaker for an hour and again after 24 hours.
Some aggregates remain unchanged, even after 24 hours.
Some aggregates fall apart during the first hour, but the smaller aggregates so formed remain where they fall.
Other aggregates slowly disperse into the water, whether they fall apart or not.
A surrounding "halo" of clay particles forms around the aggregate then spreads to form a cloudiness in the water.
Gypsum will not improve the structure of a soil where the aggregates remain unchanged or fall apart without dispersion.
The more cloudy the water, and the more rapidly the cloudiness develops, the greater the benefit of adding gypsum to the soil, and the more gypsum will be needed.
Use 0.5 - 1 kg of gypsum per square metre.
Beside improving the structure of the soil, gypsum is a good source of calcium and does not change the pH of the soil.
Gypsum reducing the likelihood of blossom end rot, and improves the structure and workability of most clay and saline (sodic) soils.
Gypsum does not alter the soil pH.

9.2.5 IBDU plant fertilizer
Some compound fertilisers are "slow release" fertilizers, e.g. IBDU, which slowly releases urea into the soil as it dissolves in the soil water.
IBDU, isobutylidenediurea, (CH)2CHCH{NHC(O)NH2}2
Another slow release fertilizer is "Osmocote", which slowly releases an NPK mixture into the soil.
4. Some fertilizers have high concentrations of plant nutrients and are called high analysis fertilizers, e.g. triple superphosphate.
5. Some fertilizers are made in the factory as granules or pellets, to give plants the correct mixture of plant nutrients, so are thus better than mixtures.

9.2.6 Liquid ammonia and anhydrous ammonia plant fertilizer
Liquid ammonia, anhydrous is ammonia gas in liquid form.
It is the cheapest source of ammonia fertilizer, but must be stored under high pressure and injected into the soil under pressure to dissolve in soil water.
It is a dangerous chemical that must be stored and handled under high pressure, requiring specially designed and well maintained equipment.
To ensure their safety, workers must be educated about the procedures and personal protective equipment required to safely handle this product.

9.2.7 Liquid manure plant fertilizer
Animal manure can be hoed into the surface of the soil where it will act as a mulch and fertilize the soil.
However, if you mix the manure with lots of dry grass it may take nitrogen plant nutrient out of the soil.
Some animal manure such as chicken manure or fresh pig manure may burn small plants if put directly in the soil.
It is best to put animal manure on the compost heap.
You can use animal manure directly on small plants as liquid manure.
Hang a sack inside a drum filled with water and put the fresh manure into the sack.
Nutrients will dissolve into the water in the drum.
Use this to water around the young plants.
You may have to dilute 1 part of manure water with 3 parts of pure water.
This is a good way of using new manure, but it is smelly.

9.2.8 Mixed or compound plant fertilizers
They have many different compositions, for example:
| 12% N, 4% P, 19% K, 10% S (high in potassium and sulfur) | 12% N, 14% P, 10% K, 3% S (high in phosphorus) |.
Osmocote is made with many different compositions, but IBDU contains 33% Nitrogen.
Only certain forms of nitrogen fertilizer are suitable for controlled release in the tropics, because most dump their nitrogen.
The estimated lasting period of 0.7 to 2.6 mm granules of IBDU depends on pH, water holding capacity of the soil and temperature.

9.2.9 Muriate of potash, KCl, plant fertilizer
Muriate of potash fertilizer (potassium chloride), in the soil, adds to the soil potassium ions, K⁺ and chloride ions, Cl^-.
These ions become attached to the clay particles and organic matter particles in the soil.
However, if soil is too acid or too alkaline, the large number of H⁺ions or OH^- ions will interfere with attachment of fertilizer ions to soil particles.
They may cause the fertilizer ions to be held too strongly to the soil particles.
If this happens, the nutrient ions cannot be used by the roots of plants and you say that the nutrients are unavailable to the plants.
Potassium chloride is highly soluble and its high salt index may disrupt osmotic gradients in the rhizosphere, harming soil bacteria.
An application of 100 kg / hectare of muriate of potash produces about 20 ppm of chloride in the soil solution to a depth of 75 mm.
Although chloride can be easily washed out of the soil, farmers are using alternatives to KCl, e.g. K2SO4, K2O, K2CO3 and mono potassium phosphate.

9.2.10 Organic gardening plant fertilizers
"What is organic gardening?" adapted from Brisbane Organic Growers Inc.
"Gardening without the use of artificial fertilizers and toxic chemicals" is probably the simplest definition, but also the least satisfying.
Organic gardeners do not just leave their gardens to nature; they use all the methods, techniques and products at their disposal to work with nature.
1. Stop using chemicals.
Safely dispose of all your chemicals, fertilizers and pesticides so that you are not tempted to use them.
2. Care for the soil, think of the soil in your garden as a living environment in which earthworms and beneficial bacteria convert organic material and inorganic soil minerals into plant food.
3. Encourage nature.
The most effective agents operating to control insect pests are those that occur in nature, the parasites, predators and diseases of the pests.

9.2.11 Seaweed extract plant fertilizers
On islands in the South Pacific the common opinion is that the best fertilizer is obtained by dragging seaweed, mostly kelp, onto the land, washing all the salt off it, then burying it in the garden.
Liquid seaweed extracts, e.g. "Seasol", "Marinure", "Maxicrop", "Algistim", may benefit plants not from their mineral nutrients, but possibly from organic substances included in the extracts.
The benefits of such extracts may be as follows:
1. increased resistance to fungal disease and insects,
2. higher yields,
3. deeper root penetration and increased nutrient uptake.
The advertising for Seasol Liquid Seaweed Extract may include claims that it is a "soil revitalizer, growth stimulant and plant tonic, not a fertilizer".

9.2.13 Plant fertilizers, straight fertilizers and mixed fertilizers
1. Simple or straight fertilizers contain only one of the main plant nutrients and usually some other plant nutrient.
Single superphosphate contains mainly phosphorus and it also contains some sulfur and calcium.
2. Mixed fertilizers contain a mixture of simple fertilizers so that nitrogen, phosphorus and potassium may all be present and other plant nutrients.
These fertilizers can be mixed before putting them in the soil or they can be bought already mixed, e.g. "Thrive" and "Zest".
3. Compound (composite) fertilizers contain N, P and K in various forms of chemicals, e.g. ammonium phosphate nitrate.
They also contain other plant nutrients.

9.3.00 Plant growth regulators
Plant growth regulators is a term that includes auxins, gibberellins, cytokinins, ethylene generators, growth inhibitors (to stop growth and promote flower production by shortening internodes), and growth retardants (to slow growth).
Plant growth regulators, called plant hormones, phytohormones, plant growth substances, but the term "plant hormone" is not approved by chemists.

9.3.1 Abscisic acid, (ABA)
Abscisic acid, C15H20O4, has the following functions:
1. Stimulates the closure of stomates during water stress.
2. Inhibits shoot growth.
3. Induces seeds to synthesize storage proteins.
4. Inhibits the effects of gibberellins.
5. Induces and maintains dormancy.
6. Induces responses to wounding.

9.3.2 Auxins
Auxins Experiment
See diagram 9.1.7: Auxin experiment
Put oat, barley or wheat grains in a flat dish containing tap water.
The next day, sow them in a pot.
When the seedlings are 3 cm high, cut off 10 mm from the tips of the two thirds of the shoots.
Leave one third of the seedlings not treated as a control.
Dissolve 1 g of gelatine, with heating, in 20 mL demineralized water.
Use this solution to stick back the shoot tips on half the cut seedlings.
Note any further growth.
The seedlings without a shoot tip stop growing.
The seedlings with the shoot tips stuck on again continue to grow almost as much as the control seedlings.
The growth substance, auxin, diffuses out of the replaced tips through the gelatine into the cut end, allowing the plant to continue to grow.
Under the influence of light, substances form in plants that, in specific concentrations, trigger cell division and cause elongation.
These growth substances (auxins) are found especially on buds and root tips.
1. Compounds are called auxins, if synthesized by plants and have similar activity to indole-3-acetic acid, C10H9NO2, (IAA).
Indole-3-acetic acid, is a monocarboxylic acid, a plant hormone, occurs in (Humulus lupulus), and in (Balansia epichloe).
Indol-3-acetic acid was the first auxin to be isolated from plants, is the most abundant, and so it is the basic auxin.
It is an isomeric acetic acid derivative of indole and important plant "hormone" (heteroauxin) that controls plant growth.
2. Auxins stimulate cell elongation, cell division in the cambium, differentiation of phloem and xylem, root initiation on stem cuttings, growth of flower parts, fruit setting, production of ethylene, and suppress growth of lateral buds and delay fruit ripening.
3. Auxins were discovered by Dutch botanist Fritz Went (1903-1990) who in 1928 isolated a plant growth substances by placing agar blocks under oat (Avena) coleoptile tips, removing them and placing them on decapitated oat stems that then resumed growth.
The "(Avena) curvature test" is based on the fact that the curvatures of the coleoptiles is proportional to the amount of growth substance in the agar.
4. An auxin is the active ingredient in a commercial root formation compound used to stimulate root formation in cuttings used for vegetative propagation, e.g. indole-3-butyric acid, C12H13NO2 (IBA)
("Rootex-L, hormone rooting liquid").
5. Auxins cause the following responses:
Stem bends toward a light source (phototropism),
Root grows downward in response to gravity (geotropism),
Adventitious roots form,
Apical meristem is dominant over lateral meristems,
Flower formation, fruit set and fruit growth.
6. The four auxins synthesized by plants are as follows:
Indole-3-acetic acid, indole acetic acid, IAA,
4-Chloroindole-3-acetic acid,
Phenylacetic acid,
Indolebutyric acid, indole-3-butyric acid, IBA, stimulated root growth.
7. Five of the many synthetic auxins are as follows:
2,4-Dichlorophenoxyacetic acid, 2,4-D, herbicide,
α-Naphthalene acetic acid, α-NAA, active constituent of commercial rooting powders,
2-Methoxy-3,6-dichlorobenzoic acid, dicamba, herbicide,
4-Amino-3,5,6-trichloropicolinic acid, picloram, herbicide,
2,4,5-Trichlorophenoxyacetic acid, 2,4,5-T, herbicide.
8. Auxins functions
Stimulates cell elongation, cell division, differentiation of phloem and xylem, root initiation on stem cuttings, lateral root development, growth of flower parts, production of ethylene.
Affects phototropism
Apical bud suppresses growth of lateral buds
Delays leaf senescence
Affects leaf and fruit abscission by ethylene stimulation.
Induces fruit setting and growth, and delays fruit ripening.

9.3.3 Cytokinins
Cytokinins, stimulate cell division, shoot initiation, bud formation, growth of lateral buds, leaf expansion.
The hundreds of cytokins include the natural compounds adenine and zeatin, and the synthetic compounds kinetin and benzyladenine.
The response will vary depending on the type of cytokinin and plant species.

9.3.4 Daminozide
Daminozide, C6H12N2O3, HO2CCH2CH2CONHNCH3)2, called "Alar".
It controls the vegetative and reproductive growth of orchard and enhances shorter and more erect peanut vines.
However, the use of "Alar" for food production in now banned in USA.
Commercial: Daminozide, butanedioic acid, "Alar", B-Nine, Alar, Kylar, SADH, B-995, aminozide, b-9, Cycocel, "Arest".

9.3.5 Ethylene gas, Abscission
Ethylene gas, CH2, stimulates fruit ripening, break of dormancy, shoot and root growth and differentiation (triple response) leaf and fruit abscission.
Abscission is the natural separation of a plant part, e.g. leaf, fruit, flower, seed, from the plant, leaving an abscission layer of cork cells to prevent water loss.
Deciduous plants lose all their leaves by abscission before winter, but evergreen plants lose their older leaves continually.

9.3.6 Gibberellins
Gibberellins, are tetracyclic diterpene acids, plant hormones that stimulate elongation of the stem, flowering, enzyme induction.
Gibberellins stimulate cell division, flowering in response to long days, production of a-amylase in germinating cereal grains,
Also, stimulate maleness in dioecious flowers (sex expression), release of dormancy, and induce germination in parthenocarpic (seedless) fruit
They affect senescence delay in leaves and citrus fruits.
There are more than 70 isolated gibberellins called GA1, GA2, GA3.
Gibberellic acid is the most widely studied plant growth regulators.
Gibberellin A1 C19H24O6, a C19-gibberellin, from Gibberella fujikuroi, lactone, a gibberellin monocarboxylic acid.
Gibberellin A4 C19H24O5, a C19-gibberellin, from Gibberella fujikuroi, lactone, a gibberellin monocarboxylic acid.
However, active gibberellins show many physiological effects, each depending on the type of gibberellin present and the species of plant.
Gibberellic acid, C19H22O6 (GA3) plant growth hormone, Toxic if ingested

9.3.7 Naphthalene acetic acid, (NAA)
Naphthalene acetic acid, C12H10O2, stimulates root growth and slows respiration.
Purchase: 1-Naphthaleneacetic acid, plant cell culture tested, BioReagent, 95%, crystalline, α-Naphthaleneacetic acid, 1-Naphthylacetic acid.

9.5.0 Commercial soil pH test kit
Testing soil pH, (Bunnings)
1. For the best growth of plants it is essential that the acidity (measured by pH) of the potting mix or soil is suitable for the plants you want to grow.
Most soils are either slightly acid or slightly alkaline.
A few soils are neutral (between acid and alkaline).
Some soils are very acid and some are very alkaline.
Neutral soils have a pH of 7.
Acid soils have pH values < 7.
Alkaline soils have pH > 7.
Plant growth is affected by soil pH.
Few plants grow well in soils with pH values below 4.5.
Plants from very acid soils grow best in soils of pH 4.5 to about pH 6, but do not grow well on neutral and alkaline soils.
Most other plants grow best in soils of pH values 6 to 7.
Plants from alkaline soils will grow on slightly acid soils, but they will also grow well on alkaline soils.
Most plants grow well in potting mixes when the pH of the mix is in the range 5.5 to 6.5.
Plants from very acid soils prefer a potting mix with a pH in the range 4.5 to 5.5.
2. Plants adapted to acid soils are often unable to get enough of essential nutrients iron and manganese from alkaline soils.
Their young leaves show yellowing (chlorosis), and growth is poor.
Severe essential nutrients deficiency leads to plant death.
Plants adapted to alkaline and slightly acid soils can be harmed by the amounts of dissolved aluminium and manganese present in very acid soils, because they probably cannot take up enough calcium.
Chlorosis Iron deficiency in soil
3. Raise soil pH by adding agricultural lime or dolomite.
A 1:1 mixture of the two may be best.
Lime / dolomite (g / m²), To raise pH of the top 10 cm about 1 pH unit.
Table 9.2.6
Soil type | Lime / dolomite | 100 (g / m²)
Sands | 100 g / m² |
Loam | 200 g / m² |
Clay soils | 300 to 400 g / m² |
Organic soils |600 g / m² |
4. Lower the pH of slightly alkaline soils (pH below 7.5), with agricultural sulfur.
Sulfur (g / m²) To lower pH of the top 10 cm by about 1 pH unit.
Table 9.2.7
Soil type | Sulfur |
Sands | 25 g / m² |
Loam | 50 to 70 g / m² |
Clays | 100 g / m² |
The large amounts of solid lime often present in alkaline soils with pH values higher than about 7.5, make it almost impossible to make these soils acid.
4. Change potting mix pH.
The mix must be moist enough to use for potting.
Raise pH with dolomite.
Add 1 to 1.5 g/L of mix to raise pH by about one unit.
Lower pH with sulfur.
Add 0.3 g/L to lower pH by about one unit.
Check the pH again after two weeks storage and add more as needed.
The pH of mix in pots should be checked every few months, because most fertilizers produce acidity.
Raise pH with a suspension of hydrated lime (builders' lime).
Suspend 5g (one heaped teaspoon) in a litre of water.
Pour the suspension onto the mix in the pot.
Use 200 mL for each litre of the mix.
(A 130 mm pot contains about 1 litre of mix.)
Pot the plants again if the pH of the mix is below 4.5.
Lower pH with a solution containing 2 g of iron sulfate per litre of water.
Apply 200 mL per litre of mix and within two minutes heavily water the pot to remove excess salt.
Wait for one week, check mix pH and add more iron sulfate if needed.
Preferred pH ranges
4.1 Soils of pH 4.5 to 6 potting mixes of pH 4.5 to 5.5: Camellia, Rhododendrons, Azalea, Gardenia, Erica, Macadamia, Juniper, Spruce, Japanese Maple
4.2 Soils of pH 5.8 to 7.5 potting mixes of pH 5.3 to 6.5: Most vegetables, bedding plants, commonly grown shrubs and trees.
4.3 Soils of pH 7 and higher potting mixes of pH 6 to 6.7: Many cacti, succulents and plants native to arid areas.
Grow roses and citrus that have been grafted onto rootstocks that tolerate these soils.
5. Directions for using the colour chart for soil pH
Careful sampling is essential.
For a garden bed, take at least 5 samples from holes dug in different parts of the bed.
Each sample is to extend from the surface to a depth of 10 cm.
Test each sample separately.
For farm paddocks, take at least 20 samples from each area.
Mix samples together thoroughly and test as one sample.
For bought and home made potting mix, thoroughly mix the bulk lot.
For mix in a pot, first knock the root ball from the pot.
Remove a wedge of mix representing the whole depth of the root ball.
Mix thoroughly.
For a mix in large tubs, dig down the side of the root ball as deeply as is possible.
Thoroughly mix the sample removed.
6. Measure pH
Place a level teaspoon of mixed soil or potting mix on the test plate.
Add 3 to 5 drops of indicator liquid and stir with the rod provided.
Dust the paste with the white powder provided.
Wait one minute.
Read from the colour card the pH value of the colour nearest to that of the sample.
The test kit contains one bottle of pH dye indicator and one bottle of barium sulfate solution.
The test kit is manufactured in Australia by Mantic Pty. Ltd, 30 Jonah Drive, Cavan, South Australia 5094, Australia.

Preface
Before teaching this project, discuss the content of the lessons with a field officer of the Ministry of Agriculture, and get advice on planting material, planting distances, site for planting, approved mulch, composting, and control of pests and diseases.
Use only the procedures, agricultural chemicals and insecticides recommended by the local field officer of the Ministry of Agriculture.