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Part 4i. Methods of increasing food production and improving sustainability

4i. Using hydroponics to grow vegetables, salad materials, crops

Doc Brown's Biology exam study revision notes

There are various sections to work through, after 1 they can be read and studied in any order.

Sub-index of notes on how to increase food production

Sub-index of notes on ALL aspects of food security

4(i) Hydroponics - growing plants without soil in a large shed with artificial light or a large greenhouse - the whole environment is carefully monitored and controlled


Many of the factors discussed in (h) about a greenhouse obviously apply here too.

The growing conditions in hydroponics can be rigorously controlled.

Instead of using soil, plants are grown with their roots 'dangling' into a nutrient solution.

The water contains the best balance of dissolved mineral ions and can be individually formulated for a particular plant.

The plants must be supported in some way - e.g. a frame with holes, through the plants grow.

The growth medium doesn't have to be water, it can be course particles of mineral or fibres e.g. gravel, rock wool or brown fibres from coconuts and watered with the nutrient solution.

The plants are grown in a large greenhouse/shed to protect the crops from the weather.

Even the floor can be painted white to reflect more light onto the plants!

Two features to maximise light absorption by the plants:

The glass panels used have a low iron content to ensure maximum transmission of visible light.

The metal frames supporting the glass panels are made as thin as possible to maximise the 'window' area.

Artificial light can be used increase rate of photosynthesis.

Hydroponics is an excellent example of applying modern technology to agriculture-horticulture

Computer systems can electronically control the conditions to optimise plant growth.

Temperature can be continuously monitored and controlled using a thermostat system.

Nutrient concentrations can be monitored and adjusted when necessary and unused minerals can be recycled and the concentrations adjusted for maximum growth.

There is also no polluting run-off into the surrounding land or waterways.

Light intensity is monitored and special lighting systems are used to increase the length of 'daylight', but can also be timed to switch off for shorter periods to allow plants to transport glucose around the plant.

The external weather conditions can be monitored and vents and blinds can be adjusted to control the internal conditions of the glasshouse/greenhouse.

Advantages of hydroponic horticulture to maximise growth and maximise yields

Its easier to control pests and diseases.

Nutrient levels can be accurately controlled e.g. the concentrations in the hydroponic water.

Hydroponics can be used where plants cannot be grown in soil - either there is no soil or it is so infertile and devoid of nutrients for plants to grow.

It can be used if the climate is unsuitable e.g. areas of very low rainfall - but you still need a water supply.

Examples of the use of hydroponic plant culture

Large scale glasshouses (big greenhouses!) are used to cultivate tomatoes and lettuce and other salad crops on big commercial scale.

Disadvantages of hydroponics

Large quantities of artificial fertilisers must be used.

The capital cost to set up a 'hydroponic farm' is high.

If a disease enters the system (e.g. big glasshouse) it can spread quickly from plant to plant causing major damage to crops.


Overall, large scale greenhouses and hydroponics units are good methods of 'factory farming' plants and biological methods of pest control are quite successful, see section (d).

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