This is a system of growing crops where compost and soil is replaced with a water solution or substrate like rock wool.

The use of hydroponics allows more control of the root system and  plant growth by controlling the amount of nutrients and water the plants (and roots) receive.

As the amount of land for growing food is reduced in the future, we will need use intensive growing systems such as hydroponics to increase food production. Edible food crops were produced hydroponically by astronauts on board the International Space Station for the first time in 2015.

Other crops may be grown hydroponically, such as strawberries and cut flowers, for example tulips and chrysanthemums. These production systems are designed to enable the fruit or flowers to be harvested efficiently.

There are two types of hydroponics:

• Plants grown in substrates such as coir, rockwool and pumice
• Plants grown in a solution hydroponic system. This includes nutrient film technique (NFT) and deep water culture (DWC)

In all hydroponic growing systems the health of the root system depends on sufficient air spaces in the substrate or oxygen content of the solution.

Hydroponic crops are grown under cover, either in a glasshouse or polytunnel. It is possible to extend the growing season with the use of extra heat and light.

Computers are used in glasshouses or polytunnels to check how much heat, light, water and nutrients the crop requires;  they continuously measure the pH solution and strength of the feed solution through electrical conductivity.

The liquid feed must contain all the key growing elements (N.P.K, plus trace elements of Fe and Mg) at the correct ratio for that specific crop to grow well. This is delivered to the plants via a drip irrigation system and samples of the feed are taken every two weeks for laboratory analysis. The picture below shows one variation of a computer system that controls the nutrients and watering.

The use of LED lighting is increasing in the horticultural world. It is possible to design a 'light recipe' providing the correct wavelength requirements for a specific crop. This provides possibilities for intensive plant and crop production in the future in spaces such as disused tunnels underground. The LED lights in this image show a mix of blue red and green. These are being used as in-canopy lights which help leaves and fruit grow and develop lower in the crop canopy.

Hydroponics are an exciting way to grow plants, especially vegetables. There are many different types and sizes of hydroponic systems that can be used, some that fit on the windowsill to some so big they need a greenhouse. You can even build vertical hydroponic systems that can be used to create green walls.

Step-by-step guide

1. Fill a 100 litre container with clean, fresh water​

2. Add high potash water soluble fertilizer to the tank as per the manufacturer's instructions. Stir this in well to increase the amount of oxygen in the water

3. Draw around the base of the aquatic pots on to the plastic or polystyrene lid, allowing 15cm from hole to hole

4. Cut the holes in the plastic or polystyrene lid and make sure the pots fit snugly in each hole. Place one plant in each 8cm aquatic pot

5. Insert the aquatic pots into the holes in the lid and ensure the base of each pot is in contact with the water

6. Place the system in a warm, light place with good air circulation

7. Lift the lid every two days to check for new root growth from the aquatic pots and top up with water. Add more fertilizer every two weeks

8. Measure the width of each plant every two days and record the results

9. Harvest the plants once the leaves start to touch the neighbouring plant