By definition, hydroponics is a method of growing plants in a water-based, nutrient-rich solution. In the hydroponic system, no solid substrate is used except for sowing, such as vegetables grown with polyurethane sponges. In a hydroponic system, the roots of the plant are continuously or intermittently immersed in a nutrient solution. Automatic hydroponic systems are usually a closed loop in terms of nutrient supply: the solution is circulated continuously or intermittently from the supply pool for days or weeks. Hydroponics is a highly rigorous and demanding system that requires more production knowledge, experience, technical skills and financial investment than many other greenhouse production systems. 1. Nutrient film technology of hydroponic system Nutrient Film Technology (NFT) is a hydroponic system in which plant roots are suspended in a circulating nutrient solution in thin films or shallow channels (also known as trenches, troughs, or drains). Typically, channels are located on slopes so that nutrient solution can be fed and drained at one end, collected in a return line at the other end and returned to the storage tank. The only solid medium used in this system is a small piece of medium for sowing seeds to start plants, which is necessary to prevent seeds from floating during the early stages of plant growth. All plant nutrient needs are met by a nutrient solution that is flushed through the plant's root system. 2. Crops suitable for NFT hydroponic system technology Crops suitable for NFT systems are grown in small pots or plugs, rock wool cubes or foam cubes and placed in channels after a large root system has formed. It is important that the breeding unit does not contribute peat moss or other loose material that would clog the system. After two to three weeks, the plants are transplanted into an NFT system, which usually consists of multiple parallel channels. NFTs are a very popular and successful way to grow lettuce, basil, and other leafy greens and herbs. 3. Channel design of hydroponic system Attention needs to be paid to proper access slope and return to the sump system. The slope of the channel is 1.2% to 3.0%, and the nutrient solution is applied at the elevated end, allowing the solution to flow down the channel, keeping the roots completely moist. The bottom of the channel must be flat and not curved to maintain shallow water flow. Usually running along the middle of the channel is a small V-shaped channel, so the solution will run along the center of the channel. Another aspect of shape is the width of the channel. The width needs to take into account the size of the root mat of the mature crop that is intended to be grown in the channel. 4. Flow of hydroponic system The solution drains from the header into the channel. The solution flows down the channel by gravity and discharges at the lower end to a large water collection tube that directs the solution back to the storage tank. As a general guide, the flow rate for each channel should be 15.8 gallons/hour (1 liter/minute). A lower water flow is recommended for crops such as lettuce, and a higher water flow is recommended for fruits and vegetables. It is also possible to distinguish between young crops (7.9 gallons/hour, 0.5 liters/min) and the required inflow rates for mature crops, with an upper limit of 31.7 gallons/hour (2 liters/minute).
