What is Hydroponics ?-

Hydroponics is a standard technique in Biology and research . It is a method of growing plants by placing roots in nutrient solutions instead of soils , under controlled environmental conditions. In the densely populated country where amount of cultivable land is less or absent, Hydroponics can be a suitable technique in those areas.Hydroponics reduces the want for land because vegetables,fruits,etc. can be produced at roof or yard of the house ,poly tunnel,net house etc. Vegetables, fruits, flowers can be produced throughout the year using hydroponic technique. Horticulture center of BARI, Bangladesh, makes a success to produce Capsicum , Lettuce, Tomato , Cucumber , Strawberry etc. through Hydroponics.

History of Hydroponics in Brief

Fig:Floating garden in Babylon

The word "Hydroponics" was first coined by Dr.W.F.Gericke in 1936 to describe the cultivation of edible and ornamental plants grows in a solution of water and dissolved in nutrients. Hydroponics is the combination of two words- 'Hydro' and 'Ponics' which come from Greek word 'Hydor' meaning water and 'Ponein'meaning 'to work',respectively. So,  literally Hydroponics mean working water. Many civilization have utilized hydroponic growing techniques throughout history.Hanging gardens of Babylon and the floating gardens of the Aztecs of Mexico and those of the  Chinese are two of the earliest examples of Hydroponics. In 1969,John Woodward published his water culture experiments. He found that plants in less pure water sources grew better than plants in distilled water. By 1842, a list of nine element believed to be essential to plant growth had been made out and the discovery of German botanist,Julius Von Sachs and Wilhelm Knop, in the years from 1859- 1865,resulted in a development of technique of soilless cultivation growth of terrestrial plants in mineral nutrient solution without soil which was known as solution culture . It quickly became a standard research and teaching technique . Solution culture is now considered a type of Hydroponics where there is no inert medium.Throughout the last century , scientists and horticulturists experimented with different method of Hydroponics. One reason to experiment with Hydroponics was the need for growing fresh produce in non arable areas of the world. During the second world war, troops stationed on non arable island in the pacific were supplied with fresh produce which was grown in locally established Hydroponic system systems. Later in the century,Hydroponics was integrated into the space programs in the U.S.A . In 1978 , Hydroponics Pioneer,Dr.Howard Rosh published 1st edition of his book:"Hydroponics Food Production".This book provides 3 part base nutrient formula that is still a major component of today's Hydroponic gardening.In Bangladesh, Hydroponic culture was first introduced by A.K.M.Selim Reza Mallik ,Senior Scientific Officer,BARI.

Advantages of Hydroponics

*No need of arable land in case of hydroponics makes the production year round or out of season.

*Since it is a soil less cultivation method,so that soil borne and nematode borne diseases are absent.

*Insect attack is less, therefore production of insecticide free fruits and vegetables is possible.

*Hydroponics may potentially produce much higher crop yields and also crop with excellent quality.

*Hydroponics can be used in places wherein ground agriculture or gardening area are not possible.

*Hydroponic gardening also offers a several benefits to our environment.Hydroponic gardening uses considerably less water than soil gardening because of the constant reuse of the nutrient solutions.There is no need to apply Pesticides as a result water pollution does not occur.Since hydroponic systems use no topsoil, so topsoil erosion is not ever an issue.

Seedling Production Through Hydroponics

Due to seedling production through hydroponics ,

sponge block is used.Normally, sponge is cut into 30cm x 30cm sizes. This sponge is cut into dot sizes with  2.5cm x 2.5cm sizes and 1cm cut is given at the middle of each square into which only one seed is sown.Before sowing of seeds, seeds should be treated with Calcium and Sodium hypochloride. After sowing of seeds, sponge is placed in a small tray. 5-8cm water is kept in this tray as it easily floats on water. After 2-3 days of seed germination 5-10ml nutrient solution is given one time and after 10-12days of seed germination, 10-12ml nutrient solution is given daily upto transplanting of seedlings.

The time of transplanting seedlings and pH value vary with species to species.e.g.

Crop name    ------Seedling age (weeks)------------pH value

Tomato          ------      3-4                     -----------   5.5 -6.5

Lettuce          ------      2-3                     -----------    6.0-6.5

Capsicum      ------       4-5                    -----------     6.0-6.5

Strawberry    ------      2-3(stolon cutting)----------      5.5-6.5

Cucumber     ------       2-3                    -----------      5.8-6.0

Cabbage       ------      4-5                     -----------       6.5-7.5

Amount of Chemical Element and Procedure to Make Nutrient Solution

To make nutrient solution , required amount of chemical element is given below:

Name of the chemical element            ------------------------------    Amount

Potassium di hydrogen phosphate       ------------------------------    270 g

Potassium nitrate                                ------------------------------    580 g

Nitrocalcite                                        ------------------------------    1000 g

Epsom salt                                         ------------------------------    510 g

EDTA Iron                                         ------------------------------    80 g

Phomic or Monoclinic tetrahydrate      ------------------------------  6.10g

Boric acid                                           -----------------------------   1.80 g

Blue vitriol                                          -----------------------------     0.40g

Ammonium hepta molybdate              ------------------------------    0.38 g

White vitriol                                        -----------------------------    0.44 g

Procedure : Care should be taken to make solution A and solution B. At first stock solution A is prepared. Appropriate amount of Nitrocalcite and EDTA Iron should be dissolved in 10 litres of water and thus stock solution A is prepared . Remaining chemical nutrients should be mixed together in 10 litres of water and thus stock solution B is prepared.To prepare 1000 litres nutrient solution , at first 1000 litre water is taken to a tank. Then 10 litre solution from stock solution A is added to tank water and  mixture is prepared by stirring the solution into water with a non metallic spoon. Then 10 litre solution from stock solution B is taken to the tank and stock solution B should be mixed well with a non metallic spoon.Thus nutrient solution necessary to the plant is prepared.

Two Common Systems In Hydroponics

Plants grown in non circulating system

*Non circulating system: In this method ,tray, plastic bucket or bottles etc. can be used. Before sowing of seedlings , the bottle should be filled with nutrient solution . If seedlings are sown in bottle or bucket then 3-4 holes should be kept for aeration.

 *Circulation System: In this method ,tray made of galvanizing iron is placed on a stand which is connected to a tank with the help of a plastic pipe .From this tank,nutrient solution is provided to the tray with the help of a pipe. The cork sheet which is above the tray, is given holes according to the distance required by the plant.For example,spacings for Lettuce,Tomato,Strawberry are 20cm x 20cm,50cm x 40cm,30cm x 30cm respectively.

pH meter and EC meter

 Seedlings with appropriate age with sponge is placed into the hole.After sowing of seedlings , circulation of nutrient solutions from the tank to the tray through the pump is conducted at least 8-10 hours daily to enhance the supply of oxygen to the plants.At least 6-8cm water should be ensured in the tray.Normally , nutrient solution should be added to the tray after 12-15days intervals.pH should be maintained between 5.8-6.5. If the value of pH is above 7, then deficiency symptoms due to the lack  of Iron,Manganese,Molybdenum, and other micronutrients,are observed. In this case ,pH should be adjusted by adding Hydrochloric acid or Phosphoric acid or Nitric acid. Again, if pH remains below 5.8, then pH should be adjusted by adding NaOH or KOH. EC of nutrient element in solution should be kept between 1.5-2.5ds/m. If the value of EC remains above 2.5ds/m, then distilled water should be added.Monitoring the value of pH and EC with the help of pH and EC meter should be done every morning and evening.

Points to be Followed for Hydroponics

*The value of EC and pH should be maintained between 1.5-2.5ds/m and 5.8-6.5,respectively.Sudden change of pH and EC of nutrient solution should be avoided.

*knowledge about nutrient deficiency symptom should be obtained.

*Temperature of nutrient solution should be maintained between 25degree to 35degree Celcius.

*Oxygen supply to the nutrient solution should be enhanced because due to Oxygen deficiency, plant root is damaged and yield is drastically reduced.(Left picture shows plant roots due to circulating system and right picture shows roots due to non circulating system.)

*Sufficient light should be ensured and disease free seedlings should be used.Diseased plants should be uprooted.

*Insect mite attack such as aphid,leaf miner,thrips,and mite attack may be observed.Necessary steps should be taken to prevent them.Daily monitoring should be done.

Limitations in Hydroponic Culture

*Nutrient solution preparation,measurement of pH and EC and identification of deficiency symptoms and necessary steps to treat the diseased plant require high technical skill and experience.

*Cultural practice in net house or glass house is costly.Even yield may be reduced if there is high temperature in net house or glass house.

*All plant species can not be grown through hydroponics.

Discussion about Hydroponics

Fig:Crop production through Hydroponics

Population growth,deforestation,construction of houses,buildings,roads etc.,reduction of arable land is increasing day by day in Bangladesh. Meet up the demand for food of increased population is not possible being only dependent on limited amount of arable land.To get recovery from future food crisis,we should not depend only on arable land. So,we have to utilize unused  space and fallow land, and in this case Hydroponics is the appropriate solution.