HYDROPONICS: A SOILLESS AGRICULTURE
DR. S.M. ALAM
July 26 - Aug 1, 2010
There are many deserts in the country. Thar in the province of Sindh, Thal and Cholistan in the province of Punjab, Kharan and Chagi in the province of Bolachistan are ideal places where hydroponics system can be established. These are totally barren (highly saline, sandy and gravelly areas), where normal agriculture is not feasible due to absence of good quality soils and enough irrigation water. In such areas, hydroponics 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 that serves as plant food and due to recycling of irrigation water.
Hydroponics is a technique for growing mostly vegetable crops using nutrient solutions instead of soil. It is a soilless culture. Researchers discovered in 19th century that plants absorb mineral nutrients as inorganic ions from water. In a natural conditions, soil acts as a mineral nutrient reservoir but the soil itself is not essential to plant growth. When mineral nutrients in the soil dissolve in water, plant roots are able to absorb them. When the required mineral nutrients are introduced into plants, 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. It is very easy to do. Hydroponics is also a standard technique in biology research and teaching and a popular hobby.
The word hydroponics is a term commonly used in describing solution culture, water culture, liquid culture, chemical culture, aqua culture, vermiculite culture, perlite culture, and soilless culture. It is used as a general term for growing plants without soil, weather water, sand, gravel or any other inert material.
Prof WF Gericke of University of California developed the water culture method in 1929. He demonstrated on a semi-commercial basis that plants could be grown to maturity without any soil. No other aspects of plants production has caught the fancy of the public than soilless growing, normally thought of public as hydroponics. Popularised in 1930's by various books and writing on the subject, hydroponics become widely and frequently used techniques for growing plants and vegetables in various countries of the world. The most significant research done on soilless culture primarily hydroponics was conducted at the Environmental Research Laboratory, Tuscon, Arizona, USA, and the Glasshouse Crops Research Institute, England.
To run a hydroponics culture, there is a need of several plant nutrient salts. The commonly-used different combinations of major salts are ammonium sulphate, potassium nitrate, calcium nitrate, potassium dihydrogen phosphate, magnesium sulphate.
As in due course of time Pakistan may have to make the use of barren lands to meet the foods requirement of its growing population. It is worthwhile to explore the feasibility of growing fresh vegetables using local material with necessary modifications of the nutrient solutions suited to climate conditions.
Three decades ago, experiments were carried out hydroponically in Sindh using desert sands and gravel materials with the application of modified Hoagland nutrient solution. The vegetable crops like tomatoes, chillies, lettuce, pea, cauliflower, pepper, melon, muskmelon, cucumber, kakri, and potato were grown in desert sand and gravel beds solution. All the proper steps were maintained and the Hoagland nutrient solutions were supplied regularly.
The growth of all the crops were better. Tomato produced about 40 tons fruit/ha, pepper produced about 15.6 tons/ha, and lettuce 36.5 tons/ha. The yields of kakri in sand bed and gravel bed were 34.11 and 12.35 tons/ha respectively. The cauliflower produce was 17.4 tons/ha. This shows that hydroponics system is very profitable and valuable for growing crops in desert sand and gravel media.
Hydroponically, various experiments have been conducted in different countries of the world and they have found remarkable results of such experiments. The workers in Sadiyat greenhouse, Dubai 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 as tons/acre/crop: cabbage (12), cucumber (12), lettuce (10.5), okra (5), tomato (30),and turnips (10). Yields of more than 100 tons/ha of field grown tomatoes have been produced in Florida (USA) in 4 to 5 months period.
The largest commercial hydroponics facility in the world is Euro fresh farms in Arizona, which sold 125 million pounds of tomatoes in 2005. Euro fresh has 256 acres under glass and represents about a third of the commercial hydroponics greenhouse area in the US. There are certain advantages and disadvantages of the system.
i) Hydroponics is often the best crop production method in remote areas that lack suitable soil. Crops can be grown in locality where normal cultivation is difficult or impracticable.
ii) Nutrient solution is homogenous, thus relatively easy to sample, test and readjust.
iii) Seepage can be stopped and surface evaporation be minimised so that less water is required for optimum yields
iv) Solution culture hydroponics does not require disposal of solid medium or sterilisation and reuse of a solid medium. Solution culture hydroponics allows greater control over the root zone environment than soil culture.
v) Soil borne diseases are virtually eliminated. Weeds are virtually eliminated.
vi) Many hydroponics systems give the plants more nutrition while at the same time using less energy and space.
vii) It provides the plant with balanced nutrition because the essential nutrients are dissolved into the water-soluble nutrient solution.
i) Initially the construction of green house and their structures are very expensive.
ii) The design of equipment and operation requires a great deal of technical knowledge.
iii) Even with automatic operation of the hydroponics system a constant supervision is necessary.
iv) If timers or electric pumps fail or the system clogs, plants can die very quickly in many kinds of hydroponics system.