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How Fertilisers Help Plants

In this worksheet, students will look at what fertilisers are and how they can be used to help plant growth.

'How Fertilisers Help Plants' worksheet

Key stage:  KS 3

Curriculum topic:  Biology: Structure and Function of Living Organisms

Curriculum subtopic:  Nutrition and Digestion: Plants

Difficulty level:  

Worksheet Overview

QUESTION 1 of 10

The main elements found in living organisms are carbon (C), nitrogen (N), oxygen (O2) and hydrogen (H2). These elements can combine in different ways to produce a variety of different compounds, all with a different use. 

 

As we know, plants make their own food through a process called photosynthesis in which they use the sunlight to change water (H2O) and carbon dioxide (CO2) into glucose and oxygen.

 

Diagram of photosynthesis
 

 

H2O and CO2, however, only contain hydrogen, oxygen and carbon which means that plants must get the nitrogen and other elements that they need from another source.  The source of these nutrients is the soil.  

Nitrogen, phosphorous and potassium (NPK) are the essential elements for healthy plant growth.  As shown in the diagram above, these nutrients are found in the soil and are taken in through the roots of plants as dissolved compounds.

 

Have a look at why these minerals are vital to healthy plant growth (and therefore, to us!):

 

  Essential   element  Use    Sign when plant is lacking this element
Nitrogen (N) Making protein and DNA Smaller than normal leaves and shoots and brown leaves
Phosphorus (P) Making important plant chemicals Yellow spots on leaves
Potassium (K) Needed for chemical reactions Poor growth and purple leaves

 

The Nutrient Problem

 

plant fertilizer sacks

 

Once a plant dies and begins to decompose, all of the absorbed nutrients are then returned to the soil for other plants to use. This is known as the nutrient cycle.

 

The problems occurs, however, when it comes to harvesting crops.  Many plants are grown by farmers to be used and sold.  When the plants are removed from the soil, so are the nutrients, causing problems for future crops planted in the same soil.  

 

The Solution

Farmers often use chemicals called fertilisers to provide the soil with the essential elements needed for plant growth.

 

Natural fertilsers such as manure and compost (rotten plant matter) are often used as they have no negative effects on the environment.

 

Compost bin

 

The increasing demand for food, however, has resulted in the use of ARTIFICIAL FERTILISERS.  Artificial fertilisers are made by the chemical industry and contain ammonium, nitrate, phosphate and potassium compounds. To be effective, a fertiliser must be soluble in water so it can absorbed by the plant roots.

 

The Effect of Fertilisers on the Environment

 

The use of artificial fertilisers can have many negative effects on the environment. Fertilisers often dissolve in the rainwater and get washed away into rivers and streams, which can lead to several problems including:

 

  • The depletion of several marine species and
  • the contamination of drinking water.

 

Once you are happy with all this information, carry on into the activity itself.

Type the word in the answer box below which completes this sentence:

 

The four main elements that make up all living organisms are oxygen, nitrogen, hydrogen and _____________.

Which of the following elements are essential elements for plant growth?

 

Tick THREE answers.

Nitrogen

Helium

Calcium

Potassium

Phosphorus

Manganese

Which essential element is needed to make proteins and DNA? 

Nitrogen

Phosphorus

Potassium

How do the three essential elements get into the plant to be used for chemical processes?  

through the leaves

through the stem

through the flower

through the roots

Purple leaves on a plant indicates a deficiency in which of the three essential elements?

nitrogen

potassium

phosphorus

Which two of the following would be classed as a natural fertiliser?

manure

miracle grow

ammonium phosphate

compost

growmore

Which three of the following could be used as a chemical in artificial fertilisers? 

Ammonium Nitrate

Aluminium Oxide

Ammonium Phosphate

Potassium Nitrate

Which word completes the following sentence?

 

It is essential that all fertilisers are ____________.

soluble

insoluble

Which of the following are negative effects of the use of fertilisers?

 

Tick three boxes.

They can leak into rivers and streams and contaminate drinking water.

They can leak into rivers and streams and kill plant life.

They can leak into rivers and streams and cause a depletion in marine species.

They can cause in increase in plant growth.

They can cause an increase in potassium compounds in the soil.

  • Question 1

Type the word in the answer box below which completes this sentence:

 

The four main elements that make up all living organisms are oxygen, nitrogen, hydrogen and _____________.

CORRECT ANSWER
carbon
EDDIE SAYS
You could describe yourself as a "carbon-based life-form" as the principal element of which you are made is carbon. Those carbon atoms in your structure all come from the food you eat. They are then built into your body.
  • Question 2

Which of the following elements are essential elements for plant growth?

 

Tick THREE answers.

CORRECT ANSWER
Nitrogen
Potassium
Phosphorus
EDDIE SAYS
The essential elements for plant growth are nitrogen, phosphorus and potassium (NPK).
  • Question 3

Which essential element is needed to make proteins and DNA? 

CORRECT ANSWER
Nitrogen
EDDIE SAYS
So, if you consider your body as mainly composed of proteins, and your instruction set as being built in your DNA, and if you realise that both of these need nitrogen atoms, then the fact that plants have the ability to extract these from the environment and build them into digestible molecules is fairly amazing.
  • Question 4

How do the three essential elements get into the plant to be used for chemical processes?  

CORRECT ANSWER
through the roots
EDDIE SAYS
These elements are absorbed by plants through their roots. Fortunately they come in water soluble form, which means that as the plant absorbs water through its root hairs and into the roots, the vital minerals enter the plant with the water from the soil.
  • Question 5

Purple leaves on a plant indicates a deficiency in which of the three essential elements?

CORRECT ANSWER
potassium
EDDIE SAYS
Purple leaves indicate a deficiency in potassium.
  • Question 6

Which two of the following would be classed as a natural fertiliser?

CORRECT ANSWER
manure
compost
EDDIE SAYS
Manure and compost are the only two naturally occurring fertilisers. The others on the list all need to be processed or created artificially.
  • Question 7

Which three of the following could be used as a chemical in artificial fertilisers? 

CORRECT ANSWER
Ammonium Nitrate
Ammonium Phosphate
Potassium Nitrate
EDDIE SAYS
Fertilisers must contain at least one of the three essential elements:
Ammonium nitrate - contains nitrogen
Ammonium phosphate - contains nitrogen and phosphorus
Potassium nitrate - contains potassium and nitrogen
  • Question 8

Which word completes the following sentence?

 

It is essential that all fertilisers are ____________.

CORRECT ANSWER
soluble
EDDIE SAYS
Fertilisers must be soluble so they can dissolve in the soil and get absorbed by the roots.
  • Question 9

Which of the following are negative effects of the use of fertilisers?

 

Tick three boxes.

CORRECT ANSWER
They can leak into rivers and streams and contaminate drinking water.
They can leak into rivers and streams and cause a depletion in marine species.
They can cause in increase in plant growth.
EDDIE SAYS
The washing of artificial fertilisers into rivers has and does cause a number of serious problems, not least the direct pollution which kills animal life. One, perhaps unexpected, side-effect is extraordinary growth of algae and plants in rivers, These choke the waterways, the ones growing on the surface block the light for those growing on the river bed and it often means the loss of biodiversity.
---- OR ----

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