hydroponic systems
Though the history of hydroponics goes back to the Hanging Gardens of Babylon , around 500 BC , this soilless plant growing technique was advanced by a number of distinguished individuals , including Francis Bacon and Wilhelm Knop . In 1929 , a man named William Gericke at UC Berkeley created a more modern example : water culture hydroponics . This hydroponic method goes without growing media at all , simply immersing root systems into water with nutrients and added oxygen .
UNDERSTANDING WATER CULTURE SYSTEMS
Recirculating deep water culture ( RDWC ), static solution culture , and deep water culture ( DWC ) are all hydroponic systems classified as water culture . Within the RDWC group , there are a few primary recirculating systems : nutrient film technique ( NFT ), top feeding , and underflow RDWC systems . Static solution and DWC systems are similar to each other , but differ in key ways . Standard DWC uses a mesh pot to contain the roots and aggressive aeration of the nutrient water , but static solution does not require these techniques . Basic static solution systems are mostly used by hobbyists growing plants that do fine with minimal oxygen in the water — take the beta fish in a tank with a peace lily as an example . When the nutrient water can be recirculated and shared between larger quantities of plants , it is conveniently possible to control nutrient and oxygen levels for the whole crop . If each grow bucket is separate from the others for the crop , on the other hand , maintenance can be cumbersome , especially when there are a large number of plants . In standard DWC , each grow bucket is separate . This is primarily why more deep water systems are set up as RDWC . Nutrient film technique is an RDWC method where the tubing , channel , or trays holding the nutrient water is sloped at about a 2.5 per cent drop , and the water is pumped at a moderate rate of around 0.3 gallons per minute so that water runs across the roots at a very slight depth . Obviously , the feed rate and slope would be adjusted according to the thickness of the roots . This still leaves us with top feeding and underflow recirculating systems , as well as NFT systems , to look at . In a top feeding system , such as bubbleponics ,
the recirculated nutrient and oxygenated water is initially fed to the top of the root system . This is most often done with seedlings and younger plants whose roots do not yet extend deeply and , therefore , there is a desire to have the heaviest concentration of oxygen at the surface . As these plants mature , the roots will grow and search for additional water and nutrient . Usually within a couple weeks , they will become large enough to reach the reservoir and gain access to that larger source , so top feeding would be less advantageous . Often , there is a desire to recirculate
“ OFTEN , THERE IS A DESIRE TO RECIRCULATE NUTRIENT WATER , THOUGH THE INPUT IS NOT NEEDED AT THE TOP AS WITH MORE MATURE PLANTS .”
nutrient water , though the input is not needed at the top as with more mature plants . The water is then infused at the bottom of the grow pots . This is known as underflow systems . There are several ways to connect this oxygen-rich water to multiple mesh pots . The size of the mesh pots holding a plant ’ s roots will determine whether that pot can be placed in a four-inch PVC tube or require a grow bucket . The large PVC tube can be used as the underflow connector with no need for a bucket when the smaller mesh pot size is sufficient for the type of plant to be grown .
46 Maximum Yield USA | February 2017