Growing Plants: Water Culture
Students’ Sheet
Introduction
If you haven’t used it yet, read the introduction to the sheet Soil Culture.
It’s commonplace to grow plants in soil. Nutrients they need are dissolved in water that surround
the soil particles and are absorbed through the plant’s roots. Hydroponics (water culture) –
growing plants in water rather than soil – is a relatively new technique. There are benefits over
soil culture, but also disadvantages.
Three important nutrients are: nitrogen, phosphorus and potassium, NPK. The elements are not
used. Instead, compounds such as potassium nitrate, ammonium sulfate and calcium phosphate
are dissolved in water.
You can use the protocol outlined below to investigate the effects of these nutrients on the growth
of seedlings by hydroponics.
Protocol
1. Pour the solution being investigated into a boiling tube, to 1 cm from its top.
2. Use the aluminium foil to make a short cone with a hole at its bottom to fit into the neck of the
boiling tube with some overlap (diagram A). Squash the overlapping foil to fold it in place
(diagram B).
A
B
C
3. Being careful not to damage it, push the root of the seedling gently through the hole in the
bottom of the aluminium cone so that it is immersed in the solution being investigated. If
necessary to could use put some loose cotton wool into the cone to support the seedling.
4. Put the boiling tube in a rack alongside with others that it will be compared with. Place the
rack in a bright light and leave it to grow for a few weeks. Every day or two top up the boiling
tube with the solution being investigated.
5. 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.
6. After five weeks, remove the seedling, dab it dry with absorbent paper and weigh it. Record
its mass.
Science & Plants for Schools: www.saps.org.uk
Growing Plants: Water Culture: p. 1
Investigation
Work in a group of five. Each member of the group will be given:

some seedlings (they might be mung beans, barley or some other plant – your teacher will
tell you)

a boiling tube

a piece of aluminium foil

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
Each member of the group should use the protocol to determine the effect of the solution they
were given on the growth of seedlings. The group can compare its results with those of other
groups.
Science & Plants for Schools: www.saps.org.uk
Growing Plants: Water Culture: p. 2