Growing plants in nutrient solution
By Dr Adnan Younis & Atif Riaz
Hydroponics is the most intensive technology for growing
plants in nutrient solutions (water containing fertilizers)
with or without the use of an artificial medium to provide
mechanical support. Food for plants are dissolved in water
and fed directly to roots.
absorb essential mineral nutrients as inorganic ions in
water. In natural conditions, soil acts as a mineral
nutrient reservoir but the soil itself is not essential to
When mineral nutrients in soil dissolve in water, plant
roots are able to absorb them. When the required mineral
nutrients are introduced into a plantís water supply
artificially, soil is no longer required for the plant to
thrive. Almost any terrestrial plant will grow with
hydroponics, but some will do better than others.
Hydroponics is also a standard technique in biology research
and teaching and a popular hobby. There has been an
increasing interest in the use of hydroponics or soilless
techniques for the production of greenhouse horticultural
crops but there is little commercial value because of it
being more expensive than the traditional agriculture.
The two main types of hydroponics are solution culture and
medium culture. Solution culture does not use a solid medium
for roots, just the nutrient solution. The three main types
of solution culture are static solution culture, continuous
flow solution culture, and aeroponics.
The medium culture method has a solid medium for roots and
is named for the type of medium, e.g., sand, gravel, or
rockwool culture. There are two main variations for each
medium, sub-irrigation and top irrigation. For all
techniques, most hydroponics reservoirs are now built of
plastic but other materials have been used including
concrete, glass, metal and wood. The containers should
exclude light to prevent algae growth in nutrient solution.
The principle advantages of hydroponics include high-density
planting, maximum crop yield, crop production where no
suitable soil exists, freedom from the constraints of
ambient temperatures and seasonality, more efficient use of
water and fertilizers, minimal use of land area, and
suitability for mechanized production and disease control.
A major advantage of hydroponics, as compared with culture
of plants in soil, is the isolation of the crop from the
underlying soil which may have problems associated with
disease, salinity, or poor structure and drainage. The
costly and time-consuming tasks of soil sterilization and
cultivation are unnecessary in hydroponics systems, and a
rapid turnover of crops is readily achieved.
In this system no soil is required and chances of soil borne
diseases are virtually eliminated. The problems due to weeds
are virtually eliminated with less or no use of pesticides.
Edible crops are not contaminated with soil. Water use can
be substantially less than with outdoor irrigation of
soil-grown crops. Solution culture hydroponics does not
require disposal of a solid medium or sterilization and
re-use of a solid medium. Solution culture hydroponics
allows greater control over the root-zone environment than
soil culture. In solution culture hydroponics, plant roots
can be seen. This system is considered high-tech and
futuristic and so appeals to many people. Hydroponics is
excellent for plant teaching and research.
The principal disadvantage of hydroponics, relative to
conventional open-field agriculture is the high cost of
capital and energy inputs, especially if the structure is
artificially heated and cooled by fan and pad systems.
A high degree of competence in plant science and engineering
skills are required for successful operation. This system
usually requires more and more frequent maintenance than
geoponics. If timers or electric pumps fail, or the system
clogs or springs a leak plants can die very quickly in
Because of its significantly higher costs, successful
applications of hydroponics technology are limited to crops
of high economic value in specific regions and often at
specific times of the year, when comparable open-field crops
are not readily available.
A weakness in any number of technical or economic links
snaps this complex chain. Deficiencies in practical
management or scientific and engineering support results in
low yields of nutrient-deficient and unattractive crops;
plant diseases; insect infestation; summer overheating;
winter chilling; under-capitalization; and indifferent cost
accounting, all of which, separately or together, have
caused hydroponics businesses to fail. There is no margin
for poor management or mistakes.
Hydroponics has been exaggerated as miraculous. There are
many widely held misconceptions regarding hydroponics, and
the following facts should be noted:
Hydroponics will not always produce greater crop yields than
with good quality soil; plants cannot be spaced closer
together than soil-grown crops under the same environmental
conditions; produce will not necessarily be more nutritious
or delicious than soil-grown produce.
With hydroponics, capital costs are several orders of
magnitude higher than those for open-field crops, and the
types of food crops feasible for hydroponics are severely
limited by potential economic return. Agronomic crops are
A decade ago, it was calculated that the highest market
prices ever paid would have to increase by a factor of five
for hydroponics agronomy to cover the cost. Since then,
hydroponics costs have more than doubled, while crop
commodity prices have remained constant. Repeated pricing
studies have shown that only high-quality garden type
vegetables like tomato, cucumber, potato, sweet peppers,
melon, and specialty lettuce can cover costs or give a
return in hydroponics systems.
As the consumer becomes increasingly aware of quality
differences, especially the high quality of tomatoes,
cucumbers, and leafy vegetables coming from hydroponics, the
demand will increase. This, along with the increased
emphasis on eating more vegetables for dietary and health
reasons, will surely help the hydroponics industry.
Courtesy: The Dawn