THE hydroponics is a method of growing plants using mineral nutrients solution instead of soil. In other words, it is a soil-less culture. Plant physiologists in the 19th century discovered that plants absorb mineral nutrients as inorganic ions in water. In a natural condition, soil acts as a mineral nutrient reservoir, but it itself is not essential for plant growth.

When mineral nutrients in the soil dissolve in water, plant roots are able to absorb them. When the required mineral nutrients are artificially dissolved in water, soil is no more required for the plant to thrive. Almost any terrestrial plant will grow with hydroponics, but some will do better than others. It is an easy method. Hydroponics is also a standard technique in biological research and teaching and a popular hobby.

The word hydroponics is commonly used in describing solution culture, water culture, liquid culture, chemical culture, aqua culture and soil-less culture. In scientific field, it is used as a general term for growing plants without soil.

The water culture method was developed in 1929 by Professor W. F. Gericke of the University of California. He demonstrated on a semi-commercial basis that plants can be grown to maturity without any soil. No other aspects of plants production have caught the fancy of the public than soil-less growing.

Popularised in 1930s by various books and writings on the subject, the hydroponics became widely and frequently used technique for growing plants and vegetables in various countries. The most significant research being done on hydroponics was being carried out at the Environmental Research Laboratory, Tuscan, Arizona, in the United States, and the Glasshouse Crops Research Institute, Little Hampton, England.

To run the hydroponics culture, several plant nutrient salts are needed. The commonly-used different combinations of major salts are ammonium sulphate, potassium nitrate, calcium nitrate, potassium dihydrogen phosphate and magnesium sulphate. From these salts, plants absorb Ca++ (calcium), K+ (potassium), NO3- (nitrate), NH4- (ammonium), Mg++ (magnesium), SO4- (sulphate) and H2PO4- (phosphate). Similarly, micronutrients salts such as ferrous sulphate, manganese sulphate, copper sulphate, zinc sulphate, boric acid, molybdic trioxide etc. are typically added to hydroponics solutions to supply essential elements and among them are Fe (iron), Mn (manganese), Cu (copper), Zn (zinc), B (boron) and Mo (molybdenum). Chelating agents are sometimes used to keep Fe soluble. Such nutrient solutions were established by Arnon and Hoagland and are widely used throughout the world in hydroponics system and the solution is called Hoagland Nutrient Solution. There is an utmost need to maintain the pH of the nutrient solution normally at 6.5 for the normal growth of plants.

Scope of hydroponics: There are many desert areas in the country like Thar in Sindh, Thal and Cholistan in Punjab, Kharan and Chagi in Bolochistan, where hydroponics system can be established. 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 containing N, P, K, Ca, Mg, S, Fe, Mn, Zn, Cu, B, Mo and Cl serve as plant food and due to recycling of irrigation water there is manifold saving on irrigation water. Underground brackish water can also be used in hydroponics system.

Over time, the country may have to make use of barren lands to meet the food requirement of its growing population, it is considered worthwhile to explore the feasibility of growing fresh vegetables using local material with necessary modifications of the nutrient solutions suited to our conditions.

About three decades back experiments were carried out in hydroponics in Sindh using desert sands and gravel with the application of modified Hoagland nutrient. The vegetable crops like tomatoes, chilly, lettuce. pea, cauliflower, pepper, melon, muskmelon, cucumber and potato were grown in desert sand and gravel beds solution, All proper steps were maintained and the Hoagland nutrient solutions were supplied regularly.

Crop growth conditions: All crops grew better under hydroponics system. Tomato produce obtained was about 40 tons/ha; pepper about 15.6 tons/ha, lettuce produce obtained was 36.5 tons/ha, cucumber yielded 34.11 and 12.35 tons/ha. 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.

Experiments carried out in hydroponics in different countries had remarkable results. The workers in Sadiyat greenhouse, Dubai, grew vegetables crops and obtained the following yield as tons/acre/crop: cabbage 31, cucumber 102, egg plant 107, lettuce 25, okra 23, tomato 71, and turnips 70.

The world’s largest commercial hydroponics facility in the Eurofresh Farms in Willcox, Arizona, sold 125 million pounds of tomatoes in 2005. The Eurofresh has 256 acres under glass and represents about a third of the commercial hydroponics greenhouse area in the US.

Hydroponics saves an incredible amount of water. However, there are certain advantages and disadvantages of the system.

Advantages: 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. Nutrient solution is homogenous, thus relatively easy to sample, test and readjust. Seepage can be stopped and surface evaporation minimised so that less water is required for optimum yields. Solution culture hydroponics does not require disposal of solid medium or sterilisation and reuse of a solid medium. Hydroponics allows greater control over the root zone environment than soil culture. Over and under-watering is prevented. Soil-borne diseases are virtually eliminated.

Weeds are virtually eliminated. Many hydroponics systems give the plants more nutrition while at the same time using less energy and space. It provides the plant with balanced nutrition because the essential nutrients are dissolved in water-soluble nutrients.

Disadvantages: Initially the construction of greenhouse and their structures are very expensive.

The design of equipment and operation requires a great deal of technical knowledge. Even with automatic operation of the hydroponics system a constant supervision is necessary. If timers or electric pumps fail or the system clogs, plants can die very quickly in many kinds of hydroponics systems.