Lesson 3: Healthy soil; Composting

Lesson 3 – Part A

WHAT IS ORGANIC GARDENING?

Organic gardeners and farmers recycle organic waste into top quality plant food. Organic fertilisers are better for the health of plants and the environment.

Organic gardeners and farmers stay away from using chemical poisons to kill pests and diseases because these poisons also kill good insects. Some poisons are even strong enough to kill birds that eat insects that have been sprayed with them! Some of these poisons get into the sap of plants we eat and can't be washed from our food. Avoiding these poisons is better for us and for the environment.

The most important difference between organic gardening and gardening that uses man-made chemicals is that organic gardeners and farmers work on building healthy soil because they know that when soil is healthy, plants become healthy, and are able to protect themselves from pests and diseases. Then poisons aren't necessary!

WHAT MAKES SOIL HEALTHY?

The best way to make garden soil healthy is to keep some recycled organic waste in the top 10 cm of soil. This is often called "adding organic matter"
Keep garden soil within a suitable acid/alkaline (sour/ sweet) range for growing your vegetables and fruits (You will learn how to do this in a future lesson)
Use only organic allowed fertilisers
Protect the soil by covering it with mulch or cover crops
Practice sensible crop rotation that includes growing 'green manures'

Organic waste that has been recycled through compost bins or worm farms reduces to a dark brown, sweet-smelling material that contains all the minerals that plants, animals and humans need for good health.

Compost is packed full of helpful bacteria, fungi and other tiny soil creatures that do amazing work in helping to keep plants healthy. These are called soil microorganisms, which means 'very, very tiny living things'. Most microorganisms can only be seen through a microscope.

Some bacteria and fungi are good, and some are bad for us. Most of them are harmless. Good bacteria help our bodies to digest our food. Good bacteria also help to make some foods like yoghurt, sour cream and cheese. Good bacteria make some vitamins inside our bodies, and others protect us from bad bacteria that cause diseases. Mushrooms are a type of good fungus that most of us know. Other good fungi make our bread and buns light and soft. We all need the help of good bacteria and fungi, and so does the garden.

Compost provides food for earthworms that increase the depth of topsoil by leaving worm manure plant food along their deep tunnels.

Compost provides food and a home for the many helpful bacteria and fungi that help protect soil from diseases.

Compost also contains a lot of humus. Humus [hue-muss] is the part of compost that can't be eaten or digested by microorganisms or earthworms. It is a natural way to store carbon in soil for very long periods of time. Humus is able to do many other important things in organic soils.

Humus allows soil to hold more moisture by acting as a giant sponge.

Some helpful bacteria in humus make a 'glue' that is able to hold soil particles in a way that improves the flow of water and air through soil. This glue helps to improve the structure of soil so that plant roots grow more easily. Strong roots help plants to resist the effects of drought and storms.

Humus and the minerals that plants need are electrically charged (similar to the effect of rubbing a blown-up balloon on your hair which makes your hair stick to the balloon). The electric charge is quite weak, but strong enough for humus to hold all the plant food minerals close to plant roots and stop them washing away in heavy rain.

Humus is also able to stop plants from soaking up too much of the minerals they only need very tiny amounts of, and to stop plants from taking in poisonous metals from soil so that they do not end up in our food.

Humus in compost provides a home for helpful fungi that stick like hairs to the roots of plants, helping them to soak up the water and minerals they need. The scientific name of this special group of fungi is mycorrhiza [my-core-rise-a], which simply means 'fungus-roots'.

Humus acts like insulation padding for plant roots so that they stay cooler in summer and warmer in winter. When roots are protected by humus, plants are less stressed by very cold winters or hot, dry weather.

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Lesson 3 – Part B

MAKING COMPOST

Vegetable gardens and orchards need more humus than the rest of the garden because we keep taking away the soil minerals that plants soak up when we harvest the food we grow.

All organic waste will break down into humus but, if we leave it to nature to make humus, it can take years for that to happen.

When we make compost we are simply speeding up humus making by turning the compost bin into a compost factory.

The first step in making compost is done by very tiny creatures called aerobic bacteria. Aerobic [air-robe-ic] means that, like us, these bacteria need oxygen from the air to live. They also need water and nitrogen to do their work. So the organic waste we put into our compost factory must contain enough nitrogen for these bacteria to break down all the organic waste. Organic waste that is green and manures from animals that eat grass all contain
nitrogen.

Aerobic bacteria are very fast workers if they have everything they need, and compost can be ready to use in your garden in about 7 weeks! While they are working, they make the organic waste very warm, and this is called 'hot' composting. The heat these bacteria make kills off weed seeds and bad bacteria and fungi.

To make sure that aerobic bacteria have enough oxygen from air to keep working all through the factory, the waste has to be turned over with a spade or garden fork often to mix air through all parts of the factory.

If air is not mixed through the compost factory the waste will start to pack down into a thick pad. When the factory has run out of air, anaerobic [an-air-robe-ic] bacteria will take over breaking down the organic waste because anaerobic bacteria do not need oxygen to live. The problem with anaerobic bacteria is that they work very slowly and make a lot of smelly gases while they are working.

After aerobic bacteria have finished their work, your compost factory will cool down and creatures that would be killed by the heat will move into the factory to finish making compost. You may see slaters, earwigs and millipedes eating the organic waste. If the bottom of your compost factory sits on soil, earthworms can move into the factory to feed and leave worm manure, which is excellent plant food.

Earthworms eat recycled organic waste. They do not like fresh organic waste. They become big and healthy in organic soil that has lots of humus, and grow much larger than worm-farm worms. You can see how big these two earthworms are next to a fifty-cent piece.

How do you know when your compost is ready? It’s ready to use on your garden when you can't recognise anything that was put into the factory, except maybe for some pieces of crushed egg shell.

To make good compost you need a good mix of things that contain nitrogen and things that contain carbon (carbohydrates).

FUELS FOR YOUR COMPOST FACTORY

GOOD FUELS

Manure from animals that eat grass (lots of nitrogen)
Chicken manure (lots of nitrogen)
Weeds without seed heads (nitrogen and carbon)
Lawn cuttings that have wilted (nitrogen and carbon)
Green prunings – shredded (nitrogen and carbon)
Raw vegetables and fruit – chopped for fast break down (nitrogen and carbon)
Uncooked kitchen waste – including tea bags and coffee grounds (nitrogen and carbon)
Old plants – chopped for fast break down (nitrogen and carbon)
Bedding straw or wood shavings for animals that eat grass or seeds (nitrogen and carbon)
Straw and hay (carbon)
Cardboard boxes and egg cartons (carbon)

USE IN SMALL AMOUNTS

Newspaper and waste paper – separate sheets crumpled or roughly shredded (carbon)
Woody prunings – shredded (carbon)
Seaweed – well-washed (help factory work faster)
Herbs – comfrey, yarrow and chamomile (help factory work faster)
Egg shells – crumbled (keep compost smelling earthy)

DO NOT ADD

Plastic or foil containers and wrapping
Fruit or vegetables that has been attacked by fruit fly or codling moth
Plants with diseases
Grey water