SPECIFICALLY cultivation of plants in water is termed as hydroponics but generally speaking the term is used for cultivation of plants in a medium other than soil. These substrates are of two types, organic and inorganic. Organic ones include peat moss, coconut fibre, straw bales, grapes residue, etc., while inorganic are perlite, vermiculite, rockwool, and sand etc.
Cultivation of plants on such substrates has become inevitable in the wake of increased macro and micro nutrient deficiency, prevailing water shortage, water logging, salinity and erosion. Under these conditions, hydroponics cultivation is preferred as it offers to realise optimum potential of plant growth and cultivation of commercial plants.
Presently hydroponics is an important growing technique in glasshouse and green houses in the Netherlands, Belgium, France, Turkey, New Zealand and Spain. Area under hydroponics is on increase, while share of soil cultivation is on decrease in many European countries.
The crops grown by hydroponics have a sizable volume of market within the country as well as abroad. Tomato is grown in thousand of tones around the world. Moreover, different types of tomatoes, including beefsteak, cluster, cherry etc. are produced by hydroponics. However, the seeds must be hybrid in nature to get the optimum yield. The crop can be obtained all round the year.
Among others, the two most important types of hydroponics include solution and medium culture. The former is further sub-divided into static solution culture, continuous flow solution culture and aeroponics. In case of static solution culture, plants are grown in containers such as buckets containing the nutrient solution. The size of the container depends upon root system whether tape root or fibrous root system. However, more than one plant can be grown in one container. The success of this technique depends upon how softly the solution is aerated. One way to enhance aeration is to keep solution level lower. Nutrient solution is changed after fixed intervals. Maintaining suitable salt concentration and level of nutrient solution, electrical conductivity meter is mostly employed.
In a continuous flow solution culture, continuous flow of nutrient solution is maintained along a path or channel. The roots of growing plants are kept into the flowing nutrient solution. Continuous flow solution culture has advantage over static solution culture in the sense that more number of plants can be handled in it as it is easier to adjust pH and nutrient levels compared to later one.
Aeroponics is another technique where roots are exposed to mist or fog of nutrient solution and remain suspended in a dark closed chamber. However, plants requiring high aeration are normally cultivated as aeroponics because these may not be able to receive required level of oxygen under static or continuous flow solution culture.
The medium culture is named according to nature and type of the medium used as substrate. For example, vermiculite culture, rock wool culture and the gravel culture etc., are mostly used as solid medium. Such a medium has large number of airspaces and contain shallow level of nutrient solution. In case of such medium, nutrient solution is replaced after a specific interval.
It is believed that the low cost and availability of the substrate, the high unit yield, no or little insect, pest and disease attack, absence of weeds infestation, freedom from soil borne diseases, low cost of crop production, clean crop production and economic convenience of cultures will determine a great expansion of this technique all around the world. For instance, China has developed systems such as Eco-organic type soil less culture that includes; coal cinder, peat moss, vermiculite, coir, sawdust, perlite, sand, rice husk etc.
Substrates for hydroponics crops are available at low cost. For instance, various parts of the coconut palm like the coconut husk, fibre from the husk, wood chips from the trunk and dried fronds can be used as growing media to raise many greenhouse crops. Coconut fibre is especially regarded excellent for high yields of tomato and other crops. The inorganic substrate, polyurethane ether foam is used globally.
Hydroponics is normally practiced in glass and green houses. The greenhouse structures depend on availability of capital. These structures are constructed to control climatic condition mainly including light, temperature, air circulation, humidity etc. for proper growth and development of the crops.
Hydroponics is a water-efficient technique. The rainwater can efficiently be collected in a reservoir and used for growing hydroponics crops. Thus the technique drastically saves the water and it is a practical technique for getting higher and quality yield of a number of crops.
The arrangement of irrigation can be manipulated by applying mist system; drip irrigation and also the controlled cooling pad system to maintain the requisite humidity in the greenhouse. In greenhouse production, the introduction of supplemental carbon dioxide inside the plant growing environment is made to enhance the crop growth.
Macro plant nutrients such as nitrogen, phosphorus, potassium, calcium, magnesium and micro nutrients viz. zinc, sulphur, iron, cupper, molybdenum, manganese, nickel etc. are acquired from the reliable source. In addition, a suitable temperature is maintained to overcome the critical moments in plants to avoid the risk of high mortality under adverse climatic conditions.
In Pakistan, the use of hydroponics for crop production is not promoted. This may be due to lack of knowledge and awareness among the farming community. Need is to promote hydroponics at commercial level to realise its potential. It is suggested that work on hydroponics at university level can change the face of agriculture sector in crop production technology. To promote intensive cultivation for increasing per acre yield is only possible if innovative technology of hydroponics is introduced and induced deep into the farmers community.