Hydroponics is a method of growing plants without using soil. In this methods plants are grown in a water based, nutrient rich solution. It does not require soil and hence the root system is supported using an inert medium such as perlite, rock wool, clay pellets, peat moss, or vermiculite. The basic principle behind hydroponics is to allow the plants roots to come in direct contact with the nutrient solution, while also having access to oxygen that is essential for proper growth.
Hydroponic vegetables are grown in soilless media under the controlled environment of greenhouses at commercial levels. It is preferably practiced on saline & waterlogged soils, deserted lands, along the road-sides, in the home gardens, on the roof-tops, backyards and balconies. Thus it can be also grown by land-less people.
Soilless agriculture was started by the English researchers during 1620. Present day experiences, suggest hydroponics as an alternative mode of farming with great potential for high yields in the different regions of the country. In view of high yields, better quality, environmental friendly products, suitability for small land holders and availability of favorable climatic conditions in Pakistan, hydroponics is the most appropriate alternative for poverty reduction and food security.
Benefits of Hydroponic System:
The major advantages of soilless agriculture over conventional agriculture are the efficient use of resources, higher density planting and efficient nutrition regulation leading to better yields per acre. Plants grow faster because even a small root system will provide the plant exactly what it needs and the plant will focus more on growing upstairs instead of expanding the root system downstairs.
The biggest advantage of hydroponics is the increased rate of growth. With the proper setup, plants will mature up to 25% faster and produce up to 30% more than the same plants grown by conventional method. This system uses less water than soil based plants because the system is enclosed, which results in less evaporation. Hydroponics is considered better for the environment as it reduces waste and pollution due to soil runoff.
The soilless agriculture is gaining popularity because it uses sterile media free of diseases that are associated with the soil systems. The hydroponic system has an attraction of reduced labor and it allows to grow more plants in a limited space. Nutritional value of the product is also better and greater yields are achieved in the soilless agriculture.
Greenhouses are designed to capture sufficient amount of light during day time. Designers usually select materials, which allow easier penetration of light. Generally the materials preferred for this purpose are transparent such as polyethylene, glass, fiber glass, tempered glass, wire nut cloth etc. Proper orientation is carefully selected to harvest maximum light. Light uniformity is another matter for hydroponic houses since the cloudy weathers decreases light availability. Generally the plants are happy with 25,000 lux to 30,000 lux intensity.
Temperature required for hydroponic greenhouse ranges from 22 oC to 28 oC. This range may vary slightly with the crops. During hot summer days, green net is opened 1 to 2 ft. below the ceiling in order to reduce light penetration and to produce cooling effect. The greenhouses are provided with vents to ensure ambient temperature. Normally shade cloths are spread over the plants to minimize the temperature effects.
During hot summer days shading of greenhouses is necessary. Green cloth is spread around the windows or walls to reduce light penetration and thus keep inside cool. It can be done by using blinds inside and outside and use of shade netting inside the unit. The outside blinds are most effective as they prevent the sun rays from entering into the shed where the inside blinds stop the sun rays when they have entered. During winters these shade cloths are rolled up to invite more light for plant growth.
Greenhouses are cooled by pumping out inside air mechanically. Exhaust fans are fixed on one side wall opposite to cooling pads or Virus net on the other side. When the fans are put on, the temperature goes down rapidly. Humidity also reduces as fans operate. The system can be automated depending on the temperature and humidity levels that are to be regulated with the exhaust fans. Temperature beyond the limits can damage the plants if they persist for few hours. For controlling temperature, cooling effects may be created by spraying water over the plants or misting that reduce temperatures.
The favorable humidity in the greenhouse is 50%, however, the humidity may go as high as 70% without serious adverse effects. The humidity in the greenhouse is monitored using digital meters. For increasing the humidity, small trays with stone bits are filled with water to cover the stones and left between the plant rows. As the water evaporates it will increase the air humidity. Similarly if the marble or stone chips are placed under the plant trays the chips may absorb water and reduce the humidity.
For humidity reduction doors, roof and side vents may be opened using automated or manual openers. Regulation of humidity is prompted through exhaust fans. During the rainy days humidity is a serious issue, any ventilation activity can bring in all the moisture from outside. In the rainy season higher humidity inside the shed minimize the flower pollination as the flowers don’t blossom and the bumble bee doesn’t come out either.
Hydroponic greenhouses should not be ventilated by opening the doors and other vents as this allow the insect pests to enter the shed and damage the crop. Ventilation should be done by using fans that are 5 to 6 ft. high to draw air through and over the plants. Humidity encourages mold and fungus growth whereas the low humidity causes dehydration of plants, so ambient humidity must be maintained.