In hydroponic gardening there is no soil used, so the plants get all their food and nutrients from a solution of water and nutrients mixed by the gardener. This film will teach about these nutrients
Most nutrients are supplied in a concentrated form in either a “grow” or ”bloom” formulation, each used at different stages of plant growth. Additionally, each formulation is supplied in two bottles marked A and B. The two should never be mixed together in their concentrated form. Young plants require a weaker nutrient solution, while more mature plants require a stronger solution. Nutrient strength is measured in cF, or Conductivity Factor. The more nutrients or salts in the water, the higher the conductivity. A cF metre has two electrical probes that are used to measure the current between them when it's inserted into water. To decide how strong to make your nutrient solution, you first need to take a background reading of the water without nutrients added. For example, some tap water has a fairly high cF reading of 5, which means it has quite a lot of mineral content already in it. If you're using a nutrient concentrate for mature plants, for which the maximum cF of the solution should be between 18 and 23. So if you take into account the fact that the water is already 5 cF, you should mix the solution at the upper end of the scale, at about 23 cF. If you've mixed a solution that is too strong, you can always add more water to dilute it. Remember that over-fertilising plants can be just as bad as under-fertilising them. Other additives to put in your nutrient solution include a plant booster and tonic, which also adds beneficial bacteria to the water, as well as a blend of hormones and vitamins to assist root development.
Once you have mixed your nutrient solution, you need to check the pH level of the water, for which you should always use a calibrated pH metre. Start by taking some pH calibrating solution and putting it into a clean container. Put the end of the pH metre into the solution, and let it stand for about 15 seconds. When used at a room temperature of 25 degrees celsius, the solution will give an accurate reading of pH 7. Use a small screwdriver to change the screw adjustment on the back of the metre, and turn it until the metre reads exactly 7. Now discard the calibrating solution – don't reuse it. Your metre should now give you accurate readings. The ideal pH level you should aim for is between 5.8 and 6.3, but a slight variance on either side of this is OK. If the pH level is too high, add a small amount of phosphoric acid to the water to bring it down. The acid needs to be handled carefully, as it can be quite dangerous. Follow the instructions on the bottle. The pH of your solution will change daily, usually going up. It's best not to correct the pH level every day though, as this can result in too much phosphoric acid in the solution. Instead, let the pH level drift for two or three days before readjusting.