https://johnelfick.github.io/school-science-lessons/foodgardens/Foodgardens1.html#12.0H anchor occurs multiple times School Science Lessons

2026-04-26

Agriculture

Please send comments to: jwelfick@gmail.com
Contents
School Food Gardens
9.4.0 Agriculture chemicals
13.0 Allelopathy
Allium species
Artichoke
5.5 Australian native foods
Avocado
Banana Project
Beetroot
Breadfruit Project
Canola
Cassava Project
Citrus
12.0 Citrus growing, by Sandra Nanka
Chicken Project
Chicken Project
Chilli Project
Cocoa Project 1
Cocoa Pests
Cocon Project 1
Cocon Pests
9.2.2 Companion planting
Composting
Cover crops Primary
Crop care
1.9 Crop rotation
Duck Project
Eggplant
Goat Project
Herbs
Hybrids, The first hybrid
9.2.3 Interplanting
Jackfruit
5.0 Legumes
8.0 Maize
Mango
6.28 Mulch saves water, Primary
Mushrooms
Mustard
Olive
9.0 Onion
Papaya Project
Pasture grass
6.0 Peas
Pesticides
Pig Project
Pigeon pea
Pineapple Project
Plant fertilizers
10.0 Planting
Pumpkin
7.0 Rhizobium
Seeds
11.0 Soils
Soya bean
Sprouts and microgreens
Sweet potato Project
Taro Project
Tomato
Vegetative reproduction
Wheat
Yam Project

5.0 Legumes
Legumes
Bean Classification of a common bean
Broad bean, (Vicia faba), Fabaceae
9.6.5 Epigeal germination of bean
9.6.11 Hypogeal germination, broad bean, pea, wheat
9.3.5 Growth of radicle, zone of elongation, broad bean root
9.3.7 Growth of first internode, runner bean seedlings
Jack bean, (Canavalia ensiformis), Fabaceae
Jequirity bean, (Abrus precatorius), Fabaceae
Lablab bean, (Lablab purpureus), Fabaceae

6.0 Peas
Pea, (Pisum sativum L.). 1753, (Lathyrus oleraceus), nowadays
9.1.6 Energy from peanuts
9.1.8 Heat energy from respiration of peas
Pea
9.1.13 Respiration of soaked peas over mercury
9.1.21 Tests for respiration of soaked peas
7.8.7, Prepare bean curd
"Beans"
9.6, Classification of a common bean
9.3.13, Root hairs of germinating bean plant
3.9.3, Soybean oil
Vigna species

7.0 Rhizobium
Rhizobium in root nodules of legumes
Rhizobium
Apigeninglucoside
4.3.14 Nitrogen-fixing bacteria
Legheamoglobin
6.9.11 Legumes for the soil
6.12.3 Nitrogen deficiency in soils
8.5.19 Rhizobium bacteria
5.2.21 Rhizobium inoculation
9.3.9 Rhizobium
4.3.18 Root nodules
6.2.2 Soil nitrogen bacteria
Apigeninglucoside
4.3.14 Nitrogen-fixing bacteria
Legheamoglobin

8.0 Maize
Maize, (Zea mays), "corn", Native American corn, sweet corn, mealy, vegetable, corn oil, corn silk herb
Maize
Baby powder
Baking powder
Boiled vegetables
Cellophane
Psoralen
Carotenes
Cryptoxanthin
Cytochromes
DIMBOA
Germinate maize grain Primary
Harzianopyridone
Rubisco
Sitosterol
Tryptamine Zeaxanthin
Flint corn, (Zea mays subsp. mays), [used for popcorn], Poaceae
Dried herb sold as purple corn seed powder.
9.17.1.2 Adding fertilizers
19.3.3 Boiling vegetables
9.185 Conduction of water and salts through the stems
9.183 Conduction of water in plants
Cooking fats
Corn oill
Corn oil
5.5.1.0 Corn products
Cornmeal glucose
Cornmeal agar
Cornstarch
Electrorheological fluid
9.3.6 Enzyme activity during germination
Faidherbia
Food allergies
1.10 Food crop families
9.5.1.2 Fruit
9.80 Monocotyledon stem, maize
9.1.3 Monocotyledons
Osmosis
9.5.3: Plants need mineral salts
Popcorn
Shear-thickening
9.1.2b Smuts
9.9.18.2 Soil-less culture solutions
Starch, cornstarch
Starch, cornstarch
Stir-thickening
Superheating in a microwave oven
Yoghurt

9.0 Onion
Onion, (Allium cepa)
Onion
Onion
9.1.12 Disinfectants
9.6.13 Mitosis in cells of onion root tip
9.1.11 Onion leaf scale cells
#9.3.6 Plasmolysis in onion epidermis
2.5.8 Stain onion epidermis

10.0 Planting
10.1 Planting
10.2 Planting pots
10.3 Planting bare rooted trees
10.4 Planting guide
10.5 Planting guide from the Moon
Planting methods

11.0 Soils
Soils 1
Soils 2
Soils 3
Soil pH test kit

12.0 Citrus growing, by Sandra Nanka
Citrus do best in a sunny position, this ensures good fruit production.
Soil should be well-drained, the roots should not sit in water.
If more than one tree is planted allow 2 to 3 m minimum between trees.
Add compost to the soil to add body to sandy soils and break up clay soils.
Dig a hole twice the size of the root ball.
Pop the tree while it is still in its bag/pot into a container of water with seaweed solution.
Remove the tree from the pot and place it in the hole.
Fill with soil leaving no air pockets and water in well.
Mulch around the tree to help keep moisture in and the area close to the tree weed and grass free.
Fertilise during early spring, summer and autumn.
Spread the fertiliser just within the drip line.
Use organic extra or aged poultry manure.
Avoid fertilising while they are in flower, because it can cause the fruit to drop.
Water twice a week for the first month after planting, then once a week or fortnight for the first year.
When the trees are established, only water during dry periods and when fruits are developing.
Soil types will determine the frequency of watering, sandy soils will require more water than clay soils.
Prune lightly once a year after fruiting.
Remove old or dead wood and any unwanted growth or branches touching the soil.
Prune to maintain the height and shape you are after.
Always prune any shoots/suckers that are growing around or below the bud union or graft.
Remove flowers from the tree for at least the first year to let the energy go into making a strong tree.
Leaf miner and scale insects can be controlled with Eco oil.
To control gall wasp, cut off any swollen branches and burn or bag the affected branches.
Dwarf Citrus are regular citrus varieties grafted onto smaller tree rootstock, usually Flying Dragon Rootstock.
The 'flying dragon' rootstock is root disease resistant as well as cold tolerant.
Dwarf citrus will grow between 1.5 m to 2 m.
The fruit is the same size and quality as regular fruit trees.
They are ideal for small gardens, courtyards, decks or balconies.

10.1 Planting
The problem of poor germination is usually caused by sowing seeds too deeply, or over-watering or under-watering.
If the seed is planted too deeply, the tiny developing plant exhausts the food supply in the endosperm before the shoot and leaves have broken through and it dies.
The general rule is to plant a seed at a depth that equals twice its width.
Water newly-sown seeds with a mixture of one fifth of a teaspoon of Epsom salts in a litre of water to aid the germination process.
The magnesium in the salts will help stimulate the enzymes that make the food in the endosperm more readily available to the young seedling.
Small seeds should be only lightly covered with soil, but larger seeds will be planted at a greater depth.
The surface of the soil dries out more quickly than it does a few millimetres deeper.
Small seeds that are surface-sown should be kept moist after planting.
Larger seeds should be given a good soaking at planting time and then watered again only after they break through the ground.
If you water the larger seeds too much, they will rot in the moist soil.
The seed of many vegetables and flowering annuals are F1 hybrids, where the plant breeders have combined two strains each with desirable characteristics.
However, F1 hybrids usually do not set seed or the seeds are not viable.
Experiment
Plant tomato seeds
To select tomato seed for planting, squeeze the pulp and the seeds on absorbent paper, e.g. a paper towel, and spread it evenly over the paper.
Remove as much pulp as possible and lay the remainder in the sun for two weeks to dry the germination inhibiting enzymes.
Lay the paper towel with seeds uppermost on seed raising mix and lightly cover with fine seed mix.
Water lightly until the seedlings emerge.

10.2 Planting pots
1. Planting into the ground
Cultivate soil before planting.
Dig hole twice the width of the container.
Remove plant from the container and place into the hole so the soil level is the same as the surrounding ground.
Fill hole firmly and water in well even if the soil is moist.
2. Watering potted plants
Rocks or gravel placed in the bottom raising the water table inside the pot because it hinders drainage and may cause root rot.
1. Test for whether potted plant needs water.
* Use the finger to check the moisture level in the potting soil.
Stick the finger into the potting soil.
If the tip of the finger does not feel moist, it is not time to water the potting soil.
* Leaves will be drooping, turn brown or yellow in colour, or even fall off if the plant is not receiving sufficient water.
However, these problems can occur with overwatering, stress on the plant, pests, and diseases infecting the plant.
* Check the weight of the pot before and after watering.
If it feels lighter than after the previous watering, it is time to water the plant.
* A moisture meter gives an accurate measurement of the moisture in the potting soil.
Push it deep into the soil and let it stay for a few seconds.
Take it out of the soil and let it stand for a few seconds before checking the readings.
3. Water for potted plants
The best water for potted plants is free from chemicals, minerals, and impurities.
Rainwater and snow will give the purest form of water, but you need to collect such water and from a clean place.
In cold countries, snow from the sidewalk might have been sprinkled with salt or pets might have urinated on the snow.
Distilled water and deionized water is free from chemicals and impurities but expensive.
Cooking water used to boil eggs and vegetables, is free from chemicals and rich in nutrients.
Most gardeners use is tap water, but it could contain chemicals like chlorine or fluoride that are harmful to the plants.
Keeping the tap water in a container for 24 hours before use to allow dissipation of most of the chemicals.
Tap water may be hard water that will harm some potted plants.
After a few months, flush out the minerals from the potting soil with rainwater or deionized water.
3 Time for watering potted plants
The best time to water potted plants is in the morning before the sun rises, to give the roots time to absorb the moisture.
After the sun rises, excess water on the plant will evaporate.
This prevents a humid and moist condition forming on the plant that can cause fungal diseases.
Evening watering should only onto the soil and not wet the leaves, which will favour parasitic fungus, e.g. powdery mildew.
4. Method of watering potted plants
* If watering from the top, keep watering until water flows out from the drainage holes at the bottom.
Leave 5 cm of space between the top of the soil and the top of the pot, to allow filling the pot up to the top with water.
If bubbles through the drainage holes appear after watering, there are air pockets, so continue the watering until air bubbles are seen no longer.
The disadvantage of watering a plant from the bottom is that the salts may accumulate on the top of the potting soil.
You will need to water the potted plant from the top once a month just to flush out these excess amounts of salts.
* If watering from the bottom, use a container wider than the pot so you can place it in the container.
Once you know that the potted plant needs watering, fill the saucer with water till until it is halfway full.
Place the potted plant inside the saucer for 10 minutes so the potting soil and roots can soak up the moisture from the drainage holes at the bottom.
Stick the finger 1-2 inches into the potting soil and check if the moisture has reached a sufficient portion of the soil.
If the tip of the finger still feels dry, keep the potted plant in the saucer with water for another 20 minutes.
When the soil has enough moisture for the plant, take the pot out of the saucer.
4. Avoid overwatering
* Check the drainage holes at the bottom.
* Avoid frequent watering.
Water the plant only when the plant needs it by the surface of the potting soil.
If the surface appears dry, you can put the finger 1-2 inches into the potting soil and check for moisture.
Give the potted plant a good watering only if there is a lack of moisture.
The lack of air will cause the roots to drown and creates an anaerobic environment suitable for fungus to grow and cause root rot.
The root ball taken from the plant will have brown, soggy, and slimy roots, and may have a noticeable smell.
Leaves that are wilting or turning yellow may be a sign of overwatering or underwatering.
In some plants overwatering cause blisters on the leaves.
5. How to save an overwatered potted plant
Take the potted plant away from sunlight to a cool place indoors so that the leaves at the top of the plant do not dry out.
Tap the sides of the pot to allow air to flow and dry the roots.
Remove the root ball by place the hand on the base of the plant just above the soil and shake the pot with the other hand until the root ball comes out.
Place the root ball on top of a pile of dry newspapers.
Use the fingers to break up the soil from the roots and remove the soil.
Cut off the diseased and damaged leaves, branches, stem, and roots.
Place the plant in a new pot with fresh and clean potting soil.
Do not water the plant as soon as it is placed it in the fresh potting soil and do not add fertilizer, but avoid watering the potting soil for a few days.
6. Use a bottle drip system for automatic watering
Make drainage holes in the top of the plastic bottle cap and fill the plastic bottle with water.
Invert the bottle and stick the top into the potting soil, but not near the base of the plant.
Attach short glass tubes to the holes in the plastic bottle cap so that the added water goes deep into the potting soil.
The water will slowly drip through the glass tubes and will be available to the potted plant for many days.

10.3 Planting bare rooted plants
Based on "Bare Rooted Plants", Gardening Australia program, Australian Broadcasting Corporation, Broadcast Sat 30 Jul 2005 at 12:00am.
Deciduous trees can be purchased as potted plants or bare rooted plants.
Bare-rooted plants are sold in winter when they are dormant, because this gives them the best chance of being replanted or transplanted successfully.
During winter, trees and shrubs that have been field grown are dug up when they're dormant, and sold, ready for planting.
You can buy nearly all deciduous plants bare rooted - everything from fruit trees to roses and ornamentals.
Bare rooted plants are grown from seed in a plant nursery, then budded or grafted and then shaped for planting in the garden.
It takes about two years to produce most of the trees.
In Australia, bare-rooted plants are available in winter - June, July and August.
After August it's too late because they start to shoot and then transplanting becomes a problem.
Plant the tree soon after receipt and don't leave it lying in the sun while you are are digging.
Prune the tree after planting, because when the trees are dug, the roots are pruned, and for a balanced tree the tops should be pruned to match the root size.
Cut branches to about 30 centimetres from the main trunk, and to a bud.
To encourage a nice branching habit, remove the leader.
When you're selecting a bare rooted plant, try to ensure there is no obvious physical damage and look for a good, even branch structure.
If it's grafted, or budded, watch for any growth emerging from the base, just remove it because that's the root stock reappearing.
Before planting, remove any diseased, or even damaged, roots.
Dig a hole with a wide diameter, but at a depth so you can plant the tree at the same level as when it was originally in the ground.
Look closely at the base of the stem and notice any slight change in colour - that is where it was in the ground.
The bud or graft should be is about 10 centimetres above the ground.
Spread the roots out in a natural position and mound a pile of soil at the base to help support the root system.
Then backfill with good soil and wiggle the tree as you go.
Add water to remove any air pockets.
Loosely stake the tree until it is established.
Do not fertilise until the tree starts growing in spring.
Bare root fruit trees, Daleys Fruit Trees

10.4 Planting guide
Crop Planting depth (cm) How planted Distance between plants Distance between rows Time to harvest (weeks)
Amaranthus, sprinkle, direct planting, thin to 15 cm between plants, 15 cm between rows, 6 weeks to harvest
Banana, 45 cm deep, suckers, 200 cm between plants, 200 cm between rows, 40 weeks to harvest
Basella, 5 cm deep, direct planting, thin to 30 cm between plants, 30 cm between rows, 5 weeks to harvest
Bean, 5 cm deep, direct planting, 15 cm between plants, 45 cm between rows, 10 weeks to harvest
Beetroot, 2 cm deep, direct planting, thin to 15 cm between plants, 30 cm between rows, 10 weeks to harvest
Broccoli, nursery, 45 cm between plants, 45 cm between rows, 14 weeks to harvest
Cabbage, nursery, 45 cm between plants, 60 cm between rows, 10 weeks to harvest
Capsicum, nursery, 45 cm between plants, 45 cm between rows, 10 weeks to harvest
Carrot, 1 cm deep, direct planting, thin to 5 cm between plants, 30 cm between rows, 12 weeks to harvest
Cassava, 10 cm deep, cuttings, 100 cm between plants, 100 cm between rows, 30 weeks to harvest
Cauliflower, nursery, 45 cm between plants, 60 cm between rows, 20 weeks to harvest
Celery, nursery, 15 cm between plants, 60 cm between rows, 20 weeks to harvest
Chinese cabbage, nursery, 30 cm between plants, 45 cm between rows, 10 weeks to harvest
Chilli, 10 cm deep, nursery, 75 cm between plants, 150 cm between rows, 20 weeks to harvest
Choko, 5 cm deep, fruit, 30 cm between plants, 100 cm between rows, 12 weeks to harvest
Comfrey, 20 cm deep, cuttings, 75 cm between plants, 100 cm between rows, 50 weeks to harvest
Cowpea, 5 cm deep, direct planting, 15 cm between plants, 45 cm between rows, 10 weeks to harvest
Cucumber, 2 cm deep, thin to 30 cm between plants, 60 cm between rows, 10 weeks to harvest
Eggplant, nursery, 60 cm between plants, 60 cm between rows, 12 weeks to harvest
Ginger, 5 cm deep, rhizome, 15 cm between plants, 45 cm between rows, 30 weeks to harvest
Haricot bean, 5 cm deep, direct planting, 15 cm between plants, 45 cm between rows, 10 weeks to harvest
Hibiscus cabbage, 10 cm deep, cuttings 60 cm between plants, 100 cm between rows, 10 weeks to harvest
Kohlrabi, nursery, 15 cm between plants, 45 cm between rows, 10 weeks to harvest
Lettuce, nursery, 30 cm between plants, 30 cm between rows, 8 weeks to harvest
Maize, 2 cm deep, direct planting, 15 cm between plants, 60 cm between rows, 15 weeks to harvest
Marrow, 5 cm deep, direct planting, 100 cm between plants, 200 cm between rows, 12 weeks to harvest
Melon, 5 cm deep, direct planting, 100 cm between plants, 200 cm between rows, 12 weeks to harvest
Mung bean, 2 cm deep, direct planting, 15 cm between plants, 45 cm between rows, 9 weeks to harvest
Okra, 5 cm deep, direct planting, 30 cm between plants, 75 cm between rows, 10 weeks to harvest
Onion, 5 cm deep, direct planting, thin to 10 cm between plants, 30 cm between rows, 15 weeks to harvest
Parsley, 1 cm deep, direct planting, 15 cm between plants, 45 cm between rows, 12 weeks to harvest
Parsnip, 1 cm deep, direct planting, 15 cm between plants, 45 cm between rows, 20 weeks to harvest
Papaya, transplant 200 cm between plants, 200 cm between rows, 16 weeks to harvest
Peanut, 2 cm deep, direct planting, 30 cm between plants, 30 cm between rows, 15 weeks to harvest
Peas, 5 cm deep, direct planting, 5 cm between plants, 45 cm between rows, 10 weeks to harvest
Pigeon pea, 5 cm deep, direct planting, 60 cm between plants, 100 cm between rows, 24 weeks to harvest
Pineapple, shoots / slips, 30 cm between plants, 60 cm between rows, 60 weeks to harvest
Pit pit, Saccharum, 20 cm deep, cuttings 100 cm between plants, 100 cm between rows, 8 weeks to harvest
Pumpkin, 2 cm deep, direct planting, 100 cm between plants, 200 cm between rows, 15 weeks to harvest
Purslane, sprinkle direct planting, 15 cm between plants, 45 cm between rows, 6 weeks to harvest
Radish, transplant, 25 cm between plants, 25 cm between rows, 16 weeks to harvest
Rhubarb, 2 cm deep, seed / crowns 45 cm between plants, 45 cm between rows, 5 weeks to harvest
Silver beet, nursery, 15 cm between plants, 30 cm between rows, 10 weeks to harvest
Snake bean, 5 cm deep, direct planting, 15 cm between plants, 100 cm between rows, 8 weeks to harvest
Snake gourd, 5 cm deep, direct planting, 30 cm between plants, 100 cm between rows, 8 weeks to harvest
Sorghum, direct planting, 15 cm between plants, 30 cm between rows, 15 weeks to harvest
Soya bean, direct planting, 15 cm between plants, 60 cm between rows, 12 weeks to harvest
Spinach, nursery, 15 cm between plants, 30 cm between rows, 8 weeks to harvest
Spring onion, 10 cm deep, direct planting, thin to 5 cm between plants, 30 cm between rows, 12 weeks to harvest
Sugar cane, cuttings, 100 cm between plants, 150 cm between rows, 50 weeks to harvest
Sunflower, 5 cm deep, direct planting, 45 cm between plants, 45 cm between rows, 16 weeks to harvest
Sweet potato 10 cm deep, cuttings 45 cm between plants, 75 cm between rows, 14 weeks to harvest
Tannia, 10 cm deep, corms, 100 cm between plants, 100 cm between rows, 120 weeks to harvest
Taro, 20 cm deep, tops, tubers, 60 cm between plants, 100 cm between rows, 80 weeks to harvest
Tomato, nursery, 60 cm between plants, 60 cm between rows, 14 weeks to harvest
Turmeric, 5 cm deep, rhizome, 15 cm between plants, 30 cm between rows, 35 weeks to harvest
Watercress, 2 cm deep, root cuttings, 15 cm between plants, 15 cm between rows, 10 weeks to harvest
Winged bean, 2 cm deep, direct planting, 15 cm between plants, 15 cm between rows, 12 weeks to harvest
Yam, 10 cm deep, tuber cuttings, 100 cm between plants, 100 cm between rows, 40 weeks to harvest
Zucchini, 5 cm deep, direct planting, 100 cm between plants, 100 cm between rows, 8 weeks to harvest

10.5 Planting guide from the Moon
The Moon's gravitational pull affects the movement of water on the Earth.
Tides are at their fullest during a full moon and their lowest during a new moon.
The moon also affects the surface tension of moisture in the soil and the flow of water through plants.
Sap moves more vigorously during the waxing phase as the moon grows to full, and slows down as the moon wanes towards the new moon.
* 1st Quarter Phase: The New Moon (dark moon) is increasing in light, a waxing moon.
The first quarter phase starts 12 hours after the exact New Moon and finishes 12 hours before the First quarter moon.
Water in the Earth is starting to be drawn up at this time, the tides start increasing in height, and moisture is increasing in the soil.
Increased sap flow produces new growth more quickly.
The best time for planting leafy annuals such as basil, parsley, coriander, dill and rocket, applying liquid fertilisers, pruning and grafting.
* 2nd Quarter Phase: The moon is still waxing, now showing more than half of its visible surface as light.
The 2nd quarter phase starts 12 hours after the first quarter moon and runs through to 12 hours before the exact full moon.
When closer to the full moon, the pull on the earth is increasing and the tides are reaching much higher levels.
The moisture in the soil is increasing and the sap in the plants is increasing.
The best time to plant fruiting/flowering annuals, e.g. tomatoes, beans, chillies, red clover, chamomile, and applying liquid fertilisers, pruning and grafting.
* 3rd Quarter Phase: The full moon has passed and will now decrease in light on its surface, a waning moon.
It runs from 12 hours after the exact full moon until 12 hours before the third quarter moon.
The tides have turned and will now start to decrease in height.
There is still moisture in the earth and the sap is still high although the flow is drawing down.
This focusses the energy towards the roots, which is more suited to root crops and perennials, plants that live longer than two years.
The best time to plant root vegetables and perennials such as beetroot, carrots, onions, licorice, turmeric, ginger, rosemary, sage, thyme and oregano.
Take cuttings and divide plants, apply solid fertiliser and harvest for storage.
* 4th Quarter Phase: More than half of the visible surface of the moon is now in darkness.
Starts 12 hours after the third quarter moon and runs through to 12 hours before the exact new moon The tides will soon be at their lowest and the sap in plants has slowed.
This phase is viewed as low in vitality and planting is not recommended now, so do not do any planting during this time.
The best time to do mowing, weeding, composting, mulching and insect control, apply solid fertilisers and prune to restrain growth.

13.0 Allelopathy
Phytochemicals are chemicals produced by plants, and some can affect our health, but they are not essential nutrients.
They include carotenoids, flavonoids, isothionates, phytosterols and the many other chemicals.
A plant does not manufacture phytochemicals to improve its own health or our health, but to protect themselves from danger from herbivores and microbial attack.
This interference mechanism is called allelopathy a term invented by Austrian researcher Hans Molish, (1856-1937)
(Greek alleon 'mutual', and pathos 'harm'), i.e. "mutual suffering".
The name refers to the chemicals washed out into the soil from fallen leaves of a defending plant.
Hans Molish knew that what he called allelopathy had long been known.
In 26 BCE, the Roman author Varro, wrote about the harmful effects of walnut trees on nearby growing species.
Varo did not know that he was writing about the phenolic organic compound juglone, C10H6O3, secreted by the roots of the black walnut (Juglans nigra).
Most people are aware of the effects of too much of the amine capsaicin, C18H27NO3, from chillies.
This chemical may restrict ingestion from herbivores and could be considered as a form of aerial allelopathy.
The two forms of soil allelopathy:
1. Leaves from the defensive plant fall down, rot, and leave active allelochemicals in the soil below the plant.
2. The roots of the defensive plant actively secrete allelopathic chemicals into the soil.
For example, the extracts, essential oil, leachates, residues, and rhizosphere soil of (Lantana camara) suppress the germination and growth of other plant species.
Several allelochemicals, such as phenolic compounds, sesquiterpenes, triterpenes, and a flavonoid, have been identified.
They have been released into the rhizosphere soil under the canopy during the decomposition residues and from the living plant parts of (Lantana camara).
The released allelochemicals suppress the regeneration process of indigenous plant species by decreasing their germination and seedling growth and increasing their mortality.
Recent researchers in plant-derived allelochemicals have suggested that they could be used for natural weed killers and in the selection of crops for mixed interplanting and crop rotations.
Use of the natural allelochemicals would give us biological weed control and we could get rid of the chemical weedicides, e.g. glyphosate, C3H8NO5P.
Researchers knew that Greek oregano, (Origanum vulgare ssp. hirtum), and rosemary, (Rosmarinus officinalis), were allelopathic plants.
So they used their essential oils for control of weeds and volunteer wheat species, and so reducing environmental damage and health hazards from chemical inputs.
The recent new interest in native Australian food plants, has lead to research about the history of aboriginals using native plants for medicinal purposes.
The Australian native bottlebrush (Callistemon citrinus) has been used to develop a broad-spectrum maize weed herbicide, Callisto®, now sold as Syngenta 2005.
Callisto® has more effective weed control than existing herbicides, with excellent crop safety and a good environmental profile (Syngenta 2005).
Also, Stinking gidgee wattle (Acacia cambagei), which grows in north-west Queensland, has almost no other species growing nearby.
This occurs, not because of its unpleasant smell after rain, but because it is excreting allelochemicals into the soil.
These allelochemicals could be used to control pastoral weed, e. g. annual ryegrass, (Lolium rigidum).
The giant ragweed, (Ambrosia trifida), is an allelopathic weed which reduces productivity of arable lands.
Allelopathy is the basis of some of the practices used in companion planting, whereby some plants like each other.
Some people call allelopathy: "non-companion planting"!, From Western Australia Department of Primary Industries and Regional Development: "Uncontrolled heavy weed growth during the summer fallow period in can reduce the yield of the subsequent crop by reducing crop emergence due to the physical and/or allelopathic interference at seeding time".
From Brisbane City Council, Weed Identification Tool: "Golden rod, (Solidago altissima), Asteraceae, weedy plant is a strong competitor in part to alleleopathic compounds, (chemicals that suppress the growth of other plants), it produces, and in the garden and grasslands, it can become weedy.
Some allelopathic weeds from "Weeds Australia".
Creeping Yellowcress, (Rorippa sylvestris), contains the anthocyanin hirsutin, C18H17O7, in its roots, which inhibits germination and growth of some crops.
Spotted Knapweed, (Centaurea stoebe subsp. australis), exudes a toxin from its roots that inhibits the growth and germination of surrounding vegetation by chemical suppression of competitors, known as allelopathy.
Tree-of-heaven, (Ailanthus altissimaIt), inhibits post-disturbance succession by other plants by creating a relatively toxic soil environment.
Indian toothcup, (Rotala indica), is a serious weed of rice in Afghanistan, Japan, Korea, Philippines, Taiwan and US, but not in Australia.
Certain Indian toothcup plants, or extracts from them, are able to suppress the growth of weeds in rice paddies, through allelopathy by the release of chemicals.
There is no agreed list of allelopathic plants, but the following are often mentioned: black mustard, cabbage, broccoli, rapeseed. Wild aster (Aster subulatus), maize, French marigold (Tagetes patula), Garlic mustard weed (Alliaria petiolata), and Johnson grass (Sorghhum halepense).
Allelochemicals not only suppress weeds, but also promote underground microbial activities.
Crop cultivars with allelopathic potentials can be grown to suppress weeds under field conditions.
Further, several types of allelopathic plants can be intercropped with other crops to smother weeds.
The common duckweed, (Lemna minor), changes the water chemistry to favour harmful algae and bacteria which attack other floating plants.
How do you use or prevent allelopathy in the herb garden?
1. Good crop hygiene
After harvest, remove all crop residues, including all the roots, and compost them or use them as mulch under fruit trees to suppress weed growth.
2. Control allelopathic weeds
Do not let Couch Grass, quackgrass (Agropyron repens), Yellow nutgrass, Mullumbimby couch. (Cyperus esculentus), Ragweed, (Ambrosia artemisiifolia) etc. grow in or near the garden beds.
3. Use crop rotation to prevent the build up of allelopathic chemicals.
In a study to evaluate the allelopathic effects of radish, (Raphanus sativus L.) on bread wheat, (Triticum aesitivum L.), wild oat (Avena fatua) and wild barley, (Hordeum spontaneum). in 5 kg pots, all plant species were shown to be sensitive to radish root extract.
It suppress seed germination, radicle growth, seedling emergence, and seedling growth.
At the cellular level, it caused oxidative stress, protein modifications, cell damage and cell death.
"Allelopathic effects of (Cassia fistula L.) on germination and seedlings growth of Raphanus sativus L".
However, there is no quick answer as to whether spaces around plants are caused by alleopathy.