Nourishment
What happens to the rubbish in your home? Do you put it in the waste bin so it is taken to the tip or do you take it to a recycling station? At the recycling station you can put the paper, metal, glass and plastic from your rubbish into separate bins. The bins are then taken away so each material can be used again. Recycling our rubbish is a vital way for us to help the Earth. We have only just started to do it. Plants have been doing it for millions of years.

When you watch the leaves fall from the trees in autumn you are seeing the beginning of a huge recycling programme. At first nothing much may seem to happen and you can have great fun kicking up the huge drifts of yellow and brown leaves that gather in parks and along pavements. As autumn turns to winter the leaves form a dark brown soggy, slippy mass on the streets and are swept away onto soil. It is here that the recycling really begins.

The soil contains thousands of animals that feed on the dead leaves. Some, like earthworms, are large and easy to see while others, like the springtail, are tiny. In fact you may only be aware that springtails are in the soil when they jump into the air as you move the dead leaves. The soil animals are not the only feeders in the soil. There are billions of microbes too. These living things are so small that a quarter of a million of them will easily fit on this full stop.

As the living things feed on the leaves, they break them down into smaller and smaller pieces. Eventually the pieces become so small that they cannot be broken into anything smaller. These pieces are the substances, which are used to make all parts of the plant. They are called soil nourishment, nutrients or minerals. Without them, plants cannot survive. In the soil, the minerals do not go to waste.

As the dead leaves are broken down by soil animals and microbes, they form a substance called humus. It coats the grains of soil and sticks them together to form lumps that we call crumbs. The humus forms a spongy coating on the soil crumbs. As water passes through the soil the humus soaks up some of it and holds in on the soil crumbs. The minerals in the humus dissolve in the soil water and wait for the next stage in the recycling programme.

When the spring comes plants send out their roots into the soil. The roots search through the soil for water and minerals. Near the tips of the roots are tiny white hairs. They grow between the soil crumbs and suck the water and minerals out of the humus. The water and minerals flow through the root hairs into the centre of the root. There are very thin long pipes in the centre of the root and they carry the water and minerals along to the top of the root. Here, the water and minerals move into more pipes. These pipes are in the stem and take the water and minerals up into the leaf ready for the final stage in the recycling programme.

The leaf is like no other living thing. It is a place where food is made using sunlight, air and water. The food that is made here is sugar but it can be turned into other foods. Some of the minerals help the plant to make many of these other foods. These foods are called proteins and are used for building other parts of the plant. Some minerals also have special tasks to do in the life of the plant. They help the leaves to stay green or help the roots and seeds to grow. Through the summer the minerals help to keep the plant alive but when winter arrives most of them are thrown away again to be recycled in the soil for the following year.

Next time you see a brown, dead leaf don't think it will go to waste. Next year it may form part of a new green leaf, a new white root or the yellow or red petal of a new flower.

Are other parts of plants recycled besides leaves?
Yes. All parts of a plant can be recycled. Many trees only lose their leaves in the autumn because they have stems covered in bark to keep them warm through the winter. Other plants without bark must lose the whole of their shoots in the autumn if they are to survive. That is why you see many plants in gardens and parks dying back in the autumn. All the parts of the shoot, such as the stem and dead flowers, are broken down to form humus. Some plants, which are called annual plants, die off completely and even their roots are turned into humus.

What happens to the plants that have died back? Have they died too?
No. They survive underground as roots bulbs or corms. In the spring they sprout new leaves and grow new shoots.

If a plant dies off completely, where do the new plants come from?
They come from the seeds that the plant has made. The seeds stay in the soil and can survive the winter there. In spring the seeds sprout and new generation of plants begins to grow.

Can tree trunks form humus?
Yes, they can, but they take a very long time. First the wood has to rot down into small flakes which fall onto the soil. When this happens, the minerals in the wood can be recycled like the minerals in other parts of the plant.

Does it only take the autumn to break down the leaves for humus?
No. Some parts of the leaves break down more easily than others and their minerals can be released into the soil quickly. Tougher parts take longer. They may take two or three years. The speed at which the leaves break down depends on the warmth of the soil and the number of living things in the soil which help break down the leaves.

Do animals have minerals in them?
Yes, they do. They acquire the minerals from the food they eat. For example, we need a mineral called calcium to make our teeth and bones grow. We can get this mineral from milk. The cow that provided the milk produced the calcium from the grass leaves that it ate.

Can the minerals in animals form humus?
Yes, they can. Animals produce solid and liquid wastes. Both kinds of waste contain minerals so whereever an animal leaves its wastes, the minerals in
them will find their way into the soil. When an animal dies, its body is broken up by animals and microbes in the soil and the minerals are released to be recycled again.

Can more nourishment be added to a soil?
Yes, it can. Gardeners have many ways of adding nourishment to the soil. They may make a compost heap from kitchen scraps and dead plants from the garden. They may buy manure or fertiliser to add extra minerals to the soil. The manure not only adds minerals but helps to build up the humus in the soil so that the soil can hold onto water too.

Why do people put wood chips on the soil?
These are put on the soil to stop weeds growing. They also form a covering, which protects the soil from the rain and helps to keep the soil warm. In time, the wood chips break down just like other plant parts and the minerals in them pass into the soil for recycling.

Why do some plants feed on insects?
Insectivorous plants grow on soil that lacks nourishment. They feed on insects to get the minerals they need. There are three ways that plants try to catch insects. They may have sticky leaves like the sundew, or have leaves which make a trap, like the Venus flytrap, or they may have leaves that make a container, which holds an insect-digesting liquid like a pitcher plant.