There are many excellent works, one can point out,
which sufficiently presents the early work, that was done with the
hydroponics (soilless) culture of plants. Woodward in 1699 made the
earliest use of water culture method without any solid material.
During the 1700s, several workers attempted to find out, what caused
plants to grow. Later on in 1800s, Sachs and Knop in Germany conducted
experiments, which helped to determine that certain essential elements
were contributors to plant growth. Out of this early research proved
the basic for preparing and managing the nutrient solution for growing
plants. It was during the hundred years period from 1850 to the mid
l900s, that all the currently recognized essential elements required
by plants all over the world were discovered.
The word "Hydroponics" is a term commonly
used in describing solution culture, water culture, liquid culture,
chemical culture, aqua culture, vermiculiculture soilless culture or
any of a variety of invented names. In the scientific field, it is
used as a general term for growing plants without soil, whether water,
sand, gravel, or any other inert material. These techniques may be
divided into several categories, such as with and without root
supporting media and static aerated or following nutrient solution
with or without its reuse. Sand or gravel culture, the nutrients
solution either periodically flooding the growing bed or vessel of
dripped through it, is still widely used technique. However, the water
culture method was developed in 1929 by Prof. W.F. Gericke of
University of California Researcher, who demonstrated on a
semi-commercial basis that plants could be grown to maturity without
any soil. No other aspect of plant production has caught the fancy of
the public than soilless growing normally thought of the public as
hydroponics. Popularized in the 1930's by various books and writings
on the object, hydroponics become a widely and frequently used
technique for growing plants and vegetables in various countries of
the world. However, this soil less culture procedure is not well
suited, where precise control of the nutrient elements is desired. In
1930, there was a renewed interest in hydroponics. These most
significant researches being done on soilless culture, primarily
hydroponics, was being conducted at the Environmental Research
Laboratory, Tucson, Arizona, USA and at the Glasshouse Crops Research
Institute, Littlehampton, England. Later on, it was adapted in many
other countries of the world. There are several factors, which control
the growing of plants in soilless culture. These factors are control
of pH, chemicals to be used in nutrient elements, electrical
conductivity of the nutrients solution and temperature of the nutrient
solution, and aeration of solution.
There are large barren areas (highly saline, sandy
and gravelly areas) in Thar deserts, Thal and Cholistan, in the
provinces of Sindh and Punjab, where normal agriculture is not
feasible due to absence of good quality soil and enough sweet
irrigation water. In such areas, hydroponic culture has proved an
alternative for raising fresh vegetable crops. In this system, instead
of soil, gravel or sand serves as the supporting medium and nutrient
solution containing N, P, K, Ca, Mg, S, Fe, Mn, Zn, Cu, B, Mo, and Cl
serve as plant food and due to the recycling of irrigation water,
there is manifold saving on irrigation water. It may even be possible
to use underground brackish water under hydroponics system.
Hydroponics use in Pakistan: As in due course
of time, Pakistan may have to make use of its barren lands to meet the
food requirement of its rapid growing population, it is considered
worthwhile to explore the feasibility of growing fresh vegetables,
using the local materials and with necessary modifications of the
nutrient solution suited to our conditions.
Techniques and methods: At the first instance,
for the experimental purpose, gravel and desert sands collected from
Thar desert and Thana Bulla Khan were treated with 4% formaldehyde
solution and washed thoroughly with tap water for several days prior
to sowing vegetable seeds. Depending upon the seasons (Rabi and Kharif)
various crops e.g. tomato (cvs. Fantastic, Roma VF, T-10, Summer
Giant, Bountry, Marglobe, Marmande, Money maker etc), pepper
(California wonder), bean, lettuce, watermelon, muskmelon, cucumber
and kakri of different varieties, groundnut, garden pea, (American
wonder), cotton, bajra, cauliflower (Chin Ka Moti), potato (atom Aloe-DRM),
okra, sugarcane etc. were grown in desert sand and gravel media.
Proper distance between rows and plants were maintained. All these
crops were grown in 4 beds of glasshouse (38 sq.m each in area) and 8
beds of open pothouse (a 11.38 sq.m each in area), filled with gravel
and desert sand. Regular spray of insecticides were made on different
crops against white flies, aphids, powdery mildew etc. Hoagland
nutrient solutions stocked in four different tanks of 1000 gallon
capacity of concentrations (ppm) of N 182, P 120, K 160, Mg 50, Ca
300, S 64, B 0.5, Mn 0.5, Cu 0.5, Zn 0.09 Mo 0.3 and Fe 5 were
irrigated to the each bed. The concentration of soluble salts and pH
of the solution were checked regularly. The pH of the solution was
maintained between 6.5 to 7.0 using H2 SO4. Optimum levels of
nutrients in the tanks were maintained by analyzing the irrigated
nutrient solutions.
Crop growth conditions: The growth of all the
crops was generally better in the open pot house as compared to glass
house with the exception of tomato and pepper plants, which were badly
affected in pot house (i.e. tomato and pepper) due to viral
infections, but grew well in glass house without any viral and white
flies attack. It was generally observed that desert sand was proved to
be a better medium for crop growth as compared to gravel. This may be
due to likely more retention of water in the desert sand than gravel.
Cucumber, kakri, watermelon and muskmelon varieties available in
Pakistan are not suited to glass house condition, as these crops
require cross fertilization by insects and lack of cross fertilization
in glass house due to close system adversely affected the pollination
or flower formation and fruit setting. Groundnut is not suited at
hydroponics system.
Results: It was observed from the present
results that all the tomato varieties tested hydroponically thrived
best in gravel beds under glasshouse conditions, producing an average
of 40 tons fruit yield per hectare. Due to severe viral infection, all
fields grown tomatoes were destroyed in the vicinity of Tandojam. The
open bed tomatoes suffered this a lot. Pepper growth was satisfactory
in glasshouse. At the later stage of growth, the attack of spider mite
and powdery mildew reduced its yields, yet it produced 15.6 tons per
hectare. In the open beds, lettuce grew very well in desert sand and
gave an average yield of 36.5 tons per hectare. In coarse gravel, the
yield was 16 tons per hectare. Snake melon (kakri), grew well in
desert sand of open pot house and produced an average yield of 24.66
tons fruit per hectare, while gravel medium produced only 11.16 tons
per hectare. Potato produced yield of 10.38 tons per hectare in gravel
bed under glasshouse condition. Cucumber produced an average yield of
34.11 tons fruit per hectare in desert sand and 12.35 tons in gravel
bed in open pot house. Cauliflower produced an average fruit yield of
17.4 tons per hectare. Crops like bajra, bean, potato and garden peas
grew well in gravel as well as in desert sand. With the increasing
knowledge of better production techniques and growth control in
soilless culture over that of soil; the yields and quality of crops
have increased considerably. The growers, however, are generally
required to have more technical knowledge in order to produce the high
yields.
Hydroponics use in other countries: Hydroponics
workers in Sadiyat greenhouse Dubai (1970-71) grew vegetable crops and
obtained yield as tons/acre/crop: cabbage (31), cucumber (102), egg
plant (107), lettuce (25), okra (23), tomato (71), and turnips (70).
Similarly, workers in USA (Florida State) obtained yield of these
vegetables by growing in the field as tons/acre/crop: cabbage (12),
cucumber (12), eggplant (8.3), lettuce (10.5), okra (5), tomato (30),
and turnips (10). Yields of 200 mt/ha of tomato have been obtained in
greenhouse hydroponic culture in a 9 to 10 months period depending on
the plant populations. This can be calculated as 10 to 15 kg of tomato
fruit/plant. Production costs for hydroponic tomatoes of high quality
can range from $0.80/kg. Yields of more than 100 mt/ha of field grown
tomatoes have been produced in Florida (USA) in a 4 to 5 month period.
There may be areas of the world where hydroponics may be the only
systems that kind be used to grow successfully food crops, which are
important in human diets. The desert reasons of the world may be such
places, where hydroponics has important application. The successfully
commercialization of hydroponics is still and open question and it has
gained popularity due to successful production of vegetables.
Advantages: (i) Crops can be grown in
localities where normal cultivation is difficult or impracticable e.g.
in arid area of saline or shallow soil. This opens up new regions for
settlement. (ii) Nutrient solution is homogeneous, thus relatively
easy to sample, test and readjust. (iii) Both nutrient solution and
supporting media are contained in beds filled with gravel or sand,
which can be sterilized to prevent root diseases in crops. (iv)
Seepage can be stopped and surface evaporation be minimized so that
less water is required for optimum yields. (v) Watering can be
automatically controlled, thus reducing labour costs. (vi) Average
yields are higher and cultivation is easy.
Disadvantages: (i) Initially, the construction
of glasshouse and their structures are expensive. (ii) The design of
equipment and operation requires a great deal of technical knowledge.
(iii) Even with automatic operation of the hydroponic system a
constant supervision is necessary. (iv) Some diseases are problem one
and even under the uniform conditions of hydroponic gardening may
spread quite rapidly. (v) Production costs for establishing and
maintaining a hydroponic system are higher than for other more
conventional growing techniques. Therefore, hydroponic growing has to
be limited to high cash crops. It takes greater skill on the part of
the grower to manage a hydroponic system and the margin of error is
quite narrow. Small misjudgments in procedures can result in
significant crop losses. The current systems that have been most
widely used with relatively good success are the various bag culture
techniques, using an organic root supporting media, such as sphagnum
peat moss or an inert substrate like perlite, with nutrient solution
being dripped into the bag.
There may be areas of the world, i.e. countries in
Middle East, Arizona state in USA, many African countries and arid
areas. Where hydroponics may be the only system that can be used to
grow successfully vegetable crops, which are important in human diets.
The desert regions of the world may be such places, where hydroponics
has important application.
Conclusion: The research works conducted for
over ten years in gravel and desert sands at Nuclear Institute of
Agriculture, Tandojam, Sindh have shown that the hydroponic system
using local materials is feasible under our conditions. However, a
number of drawbacks such as non-availability of seeds suited to
glasshouse conditions, steady electricity supply to run the electric
motors, and protection from insects and diseases, pose difficulties.
It has been established under the present experimental conductions,
that different crops can be grown in coarse gravel and desert sands of
Thar and other barren areas of the country in open and glass house
beds, provided all the necessary facilities are available. In the open
hydroponic system successful cultivation is possible if effective
viral infection control measures become available. Hydroponics system
is very profitable and valuable for growing crops in desert sand and
gravel media. However, there are certain advantages and disadvantages
of the system.
