Nitrogen is very important for all plant life! Animals eat plants.

When plants and animals die, they decompose (rot) and the nitrogen returns to the soil. Microbes also break down animal waste so that it can be used by plants again (manure).

http://www.bbc.co.uk/schools/gcsebitesize/science/21c/food/farmingrev4.shtml

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When crops are harvested (taken for food), the elements (e.g. nitrogen) are taken away instead of

being returned to the soil by dying and rotting.

If the elements are not replaced (put back), the next crops will not grow

well.

Many different chemicals are used to make plants and animals grow faster

Intensive farmers use artificial fertilizers to put elements nitrogen, phosphorus, potassium back into the soil.

It is easier to use than manure and smaller quantities are needed, because it contains more of the elements.

Artificial fertilizers are spread on the ground or sprayed on the crops.

Problems: They do not just disappear but stay in the plants that we eat, so our food

is contaminated with chemicals. Soil used to grow the plants will also be contaminated and have

chemicals in it for a very long time. Animals eat the grass , which has had chemicals sprayed on to it, so the chemicals get into their blood and therefore the meat that we eat. Chemicals run off the land into rivers and kill plants and fish.

Artificial fertilizers are banned in Organic farming. Organic farmers use animal manure, compost and human sewage,

(which has been heated to destroy any harmful microbes) to make their crops grow.

‘Green manure’ is grown – plants are grown, then ploughed in and left to rot. Worms, insects and bacteria underground are always working on making the soil good. By using a process called CROP ROTATION (changing the crop grown each year), the farmer can keep a good soil for many years.

It is illegal to sell produce as organic if it hasn’t been produced that way.

Farmers must keep to National Standards. Artificial chemicals are banned. Artificial fertilizers and pesticides in the

soil have to be below a certain level. Animals must be allowed to move freely,

given organic feed but no artificial hormones.

Pests e.g. aphids, are insects that eat crops.

Diseases e.g. potato blight, can kill crops.

Pests and diseases can mean that the yield from the crop is small – but pests and diseases can usually be controlled.

aphids

Potato blight

The crops are sprayed with man-made chemicals to get rid of pests (pesticides or insecticides) and diseases (fungicides)– this means bigger yields and plants that look good.

Other chemicals (herbicides) are used to kill weeds (plants not wanted).

But the chemicals stay on the plants and could be eaten by humans as well as the pests.

Organic farmers are not allowed to use man-made chemicals for this.

Farmers introduce natural predators e.g. ladybirds to eat aphids (biological control).

Hedges and grass are left around fields to encourage other natural predators e.g. birds. Crop rotation prevents diseases of a particular crop building up. Natural pesticides may be used. Pest and disease-resistant (stronger) varieties of plants are planted.

Organic farming

Fewer workers neededFewer

blemishes on crops

Produce is cheaper Large numbers of

animals kept in ideal conditions

Bigger yields from land available

Antibiotics use keeps animals

healthy

Use of hormones increases

meat production

Soil structure is better

Less harmful to

environment

More birds and insects

Animals lead happier

lives

No harmful chemicals – healthier?

Man-made chemicals

used

Chemicals stay in soil

Organic farming

Natural predators destroyed

Chemicals wash into

rivers

Animals live in crowded

conditionsSmaller yields

Hedgerow habitats

destroyed

More blemishes on crops

More expensive

More farm workers needed