A hydroponic system should be designed to fulfill the specific requirements of plants with the most reliable and efficient method(s) of nutrient delivery. The three major plant-requirements that a hydroponic system must satisfy are:
Hydroponic systems can be either active or passive. An active system includes a mechanical means for recirculating the nutrient solution while a passive system relies on capillary action/absorption and/or the force of gravity to replenish roots with nutrient. Besides being generally more efficient, and thus more productive, a nice feature of active systems is the ease at which they may be implemented within an automated greenhouse. Just as a simple fan can be connected to a thermostat to control exhaust, a timer may be connected to the pump(s) of an active system to cycle on and off as necessary. If this system was designed properly, a large nutrient reservoir could feed the crop for a couple of weeks before needing a refill. In this scenario, as long as the system is reliable, the garden will continue to thrive indefinitely and unsupervised.
For a hydroponic system to be considered reliable, we must insure that the three major plant requirements are met on a consistent basis. Efficiency is just as important because it will define your operating expenses and in some cases prevent disrupting the environment. The best way to build a reliable, efficient system is through intelligent engineering combined with practical experience. Although the feats of modern engineers are quite incredible these days, sometimes complex problems are solved with even more complex solutions. I believe that the most fundamental solutions are the most reliable. KISS - Keep It Simple Stupid - (US military dictum). Live by the KISS rule and rest easy at night!
Now let's take a look at some of the active hydroponic techniques currently in use today. One of the earliest records of people using hydroponics describes the floating gardens of the Mexican Aztecs. These gardens were crafted similar to naturally occurring ponds, complete with water lilies and hyacinths. In nature, these plants obtain water and nutrition directly from the pond in a bioponic environment. Waste products from fish, birds and other animals provide a rich blend of organic nutrients for the plants to thrive upon and fresh water falls from the sky in the form of precipitation to replenish that transpired by plants and lost to evaporation. In the ancient water garden, aeration and circulation was provided by the action of falling rain or running water. When the rain stopped falling or the stream ran dry, these gardens would become stagnated and eventually dry up without human intervention. For this reason, people built sophisticated irrigation systems consisting of troughs.
A second ancient method of hydroponics is sand or gravel culture. This method is still used today in the middle east where sand is quite abundant, and the lack of arable land leaves few alternatives. Although sand can be used as a growing medium with great success, it has poor aeration qualities due to the small interstitial spaces between the grains. Remember when choosing a soilfree medium for hydroponics to look for good water holding capacity and good drainage qualities as well. This combination will ensure that your choice of mediums will allow the roots to feed, exhaust CO2 and ingest Oxygen properly. Provided proper nutrient and water circulation is met, you'd be surprised at what mediums plants can grow in. I once grew a plant in the styrofoam peanuts used to protect shipments and we've all seen weeds growing from the cracks in cement sidewalks.
More recent research has shown the importance oxygen plays in the root zone. Oxygen is necessary for the plant to perform respiration, which provides the energy needed for the uptake of water and nutrient ions. Studies have proven that increased absorption of oxygen by the roots results in healthier, faster growing, and larger crops. With the results of this research being released to the industry, new methods have been designed to exploit this phenomenon.
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