Introduction
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).
