Key Stage 4 –
Nitrogen recycling
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Pupil worksheet
Why do we need nitrogen?
Plants need nitrogen-containing compounds to make vital molecules like amino
acids, DNA and chlorophyll. Without a source of nitrogen they would not grow and we would have no food.
You would think that this is not a problem because we are surrounded by
nitrogen - the air is made up of around 78% nitrogen gas. But, this is not in a form
that plants can use. They rely on bacteria to convert the nitrogen in the air into
compounds that they can absorb through their roots.
Nitrogen is moved around the environment as it moves from one organism to the
next as part of different compounds. This movement is called the nitrogen cycle.
Your task
You are a nitrogen atom. You will play a game in a group and go on a journey
around the environment. You will then use this to build up your version of the
nitrogen cycle and answer some questions to check your understanding.
Playing the game
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Get into a group of 3-4.
You will need a set of 9 cards, a counter and passport each, a dice and a clock.
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Spread the cards on the desk. Each choose a place to start and place on your
counter.
Put a tick on your passport to show where you are.
Take it in turns to roll the dice and follow the instructions on the card which
tells you where to move next. Remember to tick your passport each time if
you are in a new compound.
The winner is the first person to complete their passport.
Build a cycle
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The nitrogen cycle is a diagram, which shows the movement of nitrogen
around the environment. Work in your group and use the cards to create your
own nitrogen cycle on a piece of A3 paper. Add arrows to show the
movement of nitrogen.
Check your understanding
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Work alone to answer these questions about the nitrogen cycle.
1. Design a table, which shows the names of the four types of bacteria in the
nitrogen cycle and their function.
2. Which type of bacteria are seen as being detrimental to food production?
Explain why.
3. Some farmers use crop rotation. They will grow legumes and after harvest
let the rest of the plant rot down into the soil. Next year they will plant
another crop on this field. Explain how this technique will help improve
the growth of crops.
4. Is it possible to get nitrogen-fixing bacteria to live in the roots of other
crops like wheat? Explain how this will help to increase food production.
Key Stage 4 – Nitrogen recycling
Cards 1
Nitrogen gas (N2) in the
atmosphere
1 or 2: Get converted to nitrate in a
fertiliser via the Haber-Bosch process.
3 or 4: Get taken up by nitrogen-fixing
bacteria in a root nodule of a pea plant
and converted to amino acid in plant
5 or 6: Converted to ammonium by
nitrogen fixing bacteria in the soil.
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Ammonium (NH4+) in the soil
Nitrate (NO3-) in the soil
Even number: Converted to nitrate in the
soil by nitrifying bacteria.
1 or 2: Get taken up by plant roots and
converted to amino acids in the plant.
Odd number: Get taken up by plant roots
and converted to amino acids in the plant.
3 or 4: Converted to nitrogen gas by
denitrifying bacteria and enter the
atmosphere.
5 or 6: Get leached into a pond when it
rains.
Key Stage 4 - Nitrogen recycling
Cards 2
Amino acid in an animal
Nitrogen compound in waste
Even number: You get excreted as a nitrogen
compound in waste.
Even number: Decomposers (bacteria and
fungi) convert you into an ammonium
compound in the soil.
Even number: Get eaten by an animal and
converted into amino acids in the animal.
Odd number: The animal you are in dies and
you become a nitrogen compound in dead
material.
Odd number: You are collected and made
into a fertiliser.
Odd number: The plant you are in dies and
you become a nitrogen compound in dead
material.
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Amino acid in a plant
Key Stage 4 – Nitrogen recycling
Cards 3
Nitrogen compound in dead
material
Nitrate (NO3-) in fertiliser
Even number: Decomposers (bacteria and
fungi) convert you into an ammonium
compound in the soil.
Even number: Converted to nitrogen gas
by denitrifying bacteria and enter the
atmosphere.
Odd number: You are collected and made
into a fertiliser.
Odd number: Get leached into a pond by
the rain.
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Nitrate (NO3-) in a pond
Even number: Converted to nitrogen gas
by denitrifying bacteria and enter the
atmosphere.
Odd number: Get taken up by algae in the
water and converted to amino acids in the
plant.
Key Stage 4 – Nitrogen recycling
Passports
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