Kathy Poon 6S 28

Hydroponics

Hydroponics is a method of cultivating plants in nutrient solution, with or without the use of an artificial medium for mechanical support. No soil is used in hydroponics culture as compared with traditional planting methods. In some cases, the plants are supported by inert media such as gravel, perlite, rockwool and vermiculite.

A primary nutrient solution usually contains potassium nitrate, calcium nitrate, potassium hydrogenphosphate and magnesium sulphate in distilled water. A small amount of fungicide is usually added to prevent the growth of moulds in the solution. The formula of nutrient solution varies according to the variety of the crop, the stage of crop growth, and the parts of the crop to be harvested as well as environmental factors including temperature, day-length and humidity. For example, a chemical called potassium hydrogenphosphate contained the element P and K weighting in 263.00 grams, potassium nitrate containing N and K weighting 583.00 in grams, etc.

Nowadays, there are a variety of hydroponics systems currently in use in different parts of the world. They can be categorized by the medium that the roots submerge in, or by the way nutrient solution flows in the system. The most commonly used hydroponics systems are the Liquid culture and aggregate culture and Open system and closed system.

The liquid culture method is the simplest to set up on a small scale. The roots are hanging into the solution directly. Without an inert medium, the plant body is usually held on a piece of Styrofoam placed over the nutrient solution. This method is suitable for short plants such as lettuce and spinach. For taller plants such as tomatoes and cucumbers, they may b hung loosely with strings for support. In aggregate culture, the plant roots grow into an inert medium and are irrigated with complete nutrient solution held in separate tank. In both methods, the solution must be aerated for aerobic respiration of the root cells.

In an open hydroponics system, the nutrient solution is distributed from a reservoir to the plant, and the excess solution is drained away as waste. On the contrary, the excess solution in a closed system is collected and reused, forming a closed loop of solution flow.

There are many benefits of hydroponics. Hydroponics methods are usually practiced in association with greenhouses. The method, although expensive, is implemented worldwide for commercial purposes because of many reasons.

Firstly, crops are grown under entirely controlled environment in greenhouses. The yield of crops increase, and the quality of crops is improved because the factors contributing to their growth can be controlled within optimal levels.

Secondly, the effects of climatic changes are minimized in sheltered environment. Growing seasons therefore can be extended. The problems of pests and diseases can be kept under control. And the unit cost of crops may be reduced as a result of high planting densities, shortened growing seasons and the use of continuous, automated production methods. The use of water and nutrients become more efficient in closed hydroponics systems. Leaching of nutrients is prevented and wastage as well as pollution problems are minimized.

Thirdly, farming can be conducted in areas where the soil or the climate is not suitable for growing crops, such as the Persian Gulf and the Arab oil-producing states which are located at the edge of deserts. With specific treatments, hydroponically grown crops can be made more attractive and tastier.