What does NPK stand for?

nitrogen, phosphorus, potassium. The three nutrients that crops need most.

Which chemical kills weeds?

herbicide. Weeds are plants, and "herb" means plant.

Which is an organic fertiliser?

manure. It comes from animals and decomposes in the soil.

Which is a benefit of organic fertilisers?

they improve the structure of the soil. Organic matter helps soil to hold water and air.

What is biological control?

using a natural enemy to reduce a pest. A predator does the job of the pesticide.

Which is a limitation of biological control?

the pest is reduced but not completely removed. The predator needs some prey left to survive.

Fertilisers and pest control · Cambridge IGCSE Environmental Management

In plain words

Every harvest carries nutrients away from the field, and every crop is a free meal for something. So farmers do two things: they put nutrients back, and they fight whatever is eating the crop. Both can be done with chemicals or with nature.

9 things to know

A fertiliser replaces the nutrients that crops take from the soil.
Inorganic fertilisers are manufactured. NPK fertilisers supply nitrogen (N), phosphorus (P) and potassium (K) in known amounts. They dissolve quickly, so they act fast, and they are easy to store and spread.
Inorganic fertilisers are costly, they do nothing for the structure of the soil, and they are easily washed out into rivers.
Organic fertilisers come from living things. Crop residue is the stalks and leaves left after harvest. Manure is animal dung. Mulch is a layer of organic material, such as straw, spread on the surface.
Organic fertilisers release nutrients slowly as they decompose, and they improve soil structure and help the soil hold water. They are cheap. They are also bulky, slow to act, and of unknown strength.
A pest is an organism that damages a crop. Pesticides are chemicals that kill pests. Insecticides kill insects, herbicides kill weeds, and fungicides kill fungi.
Chemical control is fast and effective. It can also kill harmless and helpful species, pests can become resistant, the chemicals can get into water and food chains, and it must be paid for again and again.
Biological control uses a natural enemy of the pest, such as a predator, to keep its numbers down. No chemicals are used, pests do not become resistant, and it lasts.
Biological control is slower, it reduces the pest without wiping it out, and the control species may fail to survive or become a pest itself.

Worked example

Aphids are eating a crop in a greenhouse. Compare spraying insecticide with releasing ladybirds, which eat aphids.

Insecticide kills most aphids within hours, but it may kill useful insects too, and the aphids may become resistant.
Ladybirds take longer and never remove every aphid, but they keep working with no chemicals on the food.
A greenhouse is closed, so the ladybirds stay where they are needed. Biological control suits it well.

Tips and tricks

Weeds count as pests. They compete with the crop for light, water, nutrients and space.
Herbicide: weeds. Insecticide: insects. Fungicide: fungi. Pesticide is the name for all three.

6 questions, about 2 minutes.

It lands in your notebook with its questions as flashcards.

Fertilisers and pest control: 6 questions and answers

These are the quiz’s questions. Do the quiz first, then come back here for the ones that got you.

What does NPK stand for?
- nitrate, protein, carbon
- nitrogen, phosphorus, potassium (the answer)
- nitrogen, pH, calcium
- nutrients, pesticide, compost
The three nutrients that crops need most.
Which chemical kills weeds?
- herbicide (the answer)
- fungicide
- insecticide
- fertiliser
Weeds are plants, and "herb" means plant.
Which is an organic fertiliser?
- NPK granules
- insecticide
- herbicide
- manure (the answer)
It comes from animals and decomposes in the soil.
Which is a benefit of organic fertilisers?
- they act within hours
- they improve the structure of the soil (the answer)
- the amounts of nutrients are exactly known
- they take up very little space
Organic matter helps soil to hold water and air.
What is biological control?
- spraying crops with chemicals
- growing crops in a greenhouse
- using a natural enemy to reduce a pest (the answer)
- changing the genes of a crop
A predator does the job of the pesticide.
Which is a limitation of biological control?Stretch
- it leaves chemicals on food
- pests become resistant to it
- it has to be reapplied every week
- the pest is reduced but not completely removed (the answer)
The predator needs some prey left to survive.

6 questions

Tap an answer and you’ll see straight away whether it’s right, and why.

Worksheet

3 questions, 8 marks. Write your answers on paper, then check them.

Fertilisers and pest control

Cambridge IGCSE Environmental Management 0680 · 8 marks · papermunch.org

Name ______________________________ Date ______________

State two benefits of inorganic fertilisers.[2]
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Any two: the amounts of nutrients are known; they act quickly; they are easy to store, transport and spread.
I got this one
Name three organic fertilisers.[3]
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Crop residue, manure and mulch.
I got this one
Describe biological control and give two of its benefits.[3]
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A natural enemy of the pest, such as a predator, is used to reduce its numbers. Benefits, any two: no chemicals are used; pests do not become resistant; it is long lasting; it targets only the pest.
I got this one

Answers: Fertilisers and pest control

1. Any two: the amounts of nutrients are known; they act quickly; they are easy to store, transport and spread.
2. Crop residue, manure and mulch.
3. A natural enemy of the pest, such as a predator, is used to reduce its numbers. Benefits, any two: no chemicals are used; pests do not become resistant; it is long lasting; it targets only the pest.