Hydroponics is a way of growing vegetables, herbs, citrus and flowers without soil. The growing medium is air, water, or a specific mixture that includes perlite, vermiculite, gravel, rockwool and coconut fibers. Hydroponic growing methods offer increased yields across the board for any type of crop. For example, tomatoes that are grown in an acre of soil will yield a five to ten ton crop. The same amount of tomatoes grown in a hydroponic greenhouse will yield from 60 to 300 tons.
Hydroponic systems in greenhouses vary based on the types of plants the growers are cultivating. The NFT, Nutrient Film Technique is one way to grow herbs and other leafy vegetables or flowers. The NFT system in a greenhouse works with rows of food grade PVC growing trays, each with removable lids that have a row of holes where the plants are placed. The roots of the plants dangle in the air beneath the tray with the tips of the roots resting in a flow of nutrient water in the base of the tray. The nutrient water is piped into one end of each of the rows, flows over the roots and then back out again at the opposite end of the row. The trays are generally suspended in the greenhouse on a system of galvanized steel pipes, though some greenhouse growers prefer tables. A holding tank for nutrients and water may be separate or combined, depending on the hydroponic system the grower selects.
Some hydroponic greenhouses may choose the ebb and flow technique, which is set up the same way as the NFT, with suspended trays and pipes at either end of the trays, one flowing in and one flowing out. In this case, a growing medium, typically gravel, is used inside the trays and nutrient water is pumped in periodically during the day. Hydroponic greenhouses also work with automated systems for testing the pH and nutrient levels within each growing tray. The amount of nutrient water the plants receive is automatically controlled based on predetermined levels. Automation is one of the keys to successful hydroponic greenhouse production.
All plants need the proper amount of light, whether they are growing hydroponically or in soil. Many greenhouses enjoy an abundance of natural sunlight, which includes the necessary blend of blue and red light for optimum plant growth. However, the fast growing hydroponic plants need supplemental light during the winter months to maintain productive growing levels. The addition of metal halide, high pressure sodium or LED grow lights in a hydroponic greenhouse works with the natural light to offer adequate levels of red or blue light so that the crops will flourish.