Growing Plants: Soil Culture
Students’ Sheet
Introduction
As you can probably guess, growing plants in soil is
called soil culture. There are various types of soil and
most contain nutrients essential for healthy growth.
However, sometimes there aren’t enough nutrients
and so people use fertilisers to add them to the soil.
Nutrients are often represented by the symbols of the
key element. The three primary elements are:
nitrogen, N
phosphorus, P
potassium, K
Nutrients are not ‘plant food’
Food stores energy which is
transferred to energy stores in
your body when you eat.
Fertilisers are often said to be
‘plant food’, but they aren’t. They
contain nutrients essential for
plant growth, but they do not store
energy that can be transferred to
plants. Plants get their energy
from the Sun, not nutrients.
Compounds of other essential elements are also
needed, but in smaller quantities.
But nutrients are not the elements themselves. They are compounds soluble in water whose
particles are made from the element’s atoms. These particles may be molecules or ions.
Solutions of compounds are absorbed through a plant’s roots.
Atoms, elements and compounds



Atoms are the simplest particles from which are matter is made
Elements are substances made from just one type of atom. There are about 100
elements.
Compounds are substances made from atoms of two or more elements
Here are two examples of a nutrient.
Potassium sulfate, K2SO4
The chemical formula tells you that one formula unit is made from 2 potassium atoms, 1 sulfur
atom and 4 oxygen atoms.
Ammonium nitrate, NH4NO3
The chemical formula tells you that one formula unit is made from 2 nitrogen atoms, 4 hydrogen
atoms and 3 oxygen atoms.
Protocol
This protocol can be used to investigate the effects of nutrients on the growth of seedlings
produced from germinated seeds.
1. Pour enough solution being investigated into the water container so that the wick dips into it
and stays moist at all times.
2. Fill the small container (with the wick in place) to within 1 cm of the top with soil. Add two
seeds and cover them with another 2-3 mm depth of soil and firm it gently.
Science & Plants for Schools: www.saps.org.uk
Growing Plants: Soil Culture: p. 1
3. Place the small container on the
water container so that its wick
dipping into nutrient solution. Water
the surface of the soil with 5 cm3 of
the solution being investigated.
seeds
4. Leave in a bright place for five
weeks (if you use a light bank,
three weeks would be long
enough).
soil
5. If both seeds germinate, remove
the weakest looking seedling, being
careful not to disturb the one that is
left to grow.
nutrient
solution
wick
6. Keep a record of the seedling’s growth, observing one or twice a week. You could, for
example, record when leaves appear and the appearance of the seedling, including the
colour of the leaves, and measure the height of the seedling.
7. After five weeks, remove the seedling, shake it gently to remove any soil sticking to its roots
and weigh it. Record its mass.
Investigation
Work in a group of five to investigate the effects of the three primary nutrients. Each member of
the group will be given the necessary equipment together with:

some radish seeds (you may be given other types to investigate)

soil containing little or no nutrients

one of these five solutions (a different one for each member of the group):
Solution
N
P
K
1



2


x
3

x

4
x


5
x
x
x
 present, x not present

small container with a wick to allow watering from below

water container and lid, with a slot cut in the lid for the wick to pass through and dip into the
nutrient solution.
Each member of the group should use the protocol to determine the effect of the solution they
were given on the growth of the seedlings. You can compare your results with those of others in
your group and then with those of other groups.
Science & Plants for Schools: www.saps.org.uk
Growing Plants: Soil Culture: p. 2