Normally plants get their nutrients from the soil. However, in hydroponics, we do not have any nutrient-rich soil. Instead we have an inert medium like hydroton, perlite, or rockwool that provides support for the root structure. We then bathe the roots in a nutrient-rich solution. The roots absorb all their required nutrients from this solution.
Nutrients are divided into two categories: macronutrients and micronutrients. Macronutrients are those that plants need in large amounts, including carbon, phosphorous, hydrogen, nitrogen, oxygen, sulfur, potassium, magnesium, and calcium. Micronutrients are needed in tiny amounts but are essential. These include zinc, nickel, boron, copper, iron, manganese, molybdenum, boron, and chlorine.
Without these essential elements, plants are unable to complete the life cycle. For hydroponic gardeners, this means that without proper nutrients they cannot produce fruit or vegetables or that what they do produce would be sub-par.
Elements play a vital role in the composition of the plant’s structure as well as any flowering or fruit it may produce. A concoction of the nutrients and needed for many different plant varieties are available for purchase. Then, simply add distilled or purified water.
Since the nutrients and minerals are already dissolved in water it is much easier for the roots to absorb. This results in a more efficient nutrient uptake by the roots and an overall better plant growth.
By carefully monitoring and adjusting the nutrient solution we can provide plants with the exact nutrients they need. Any nutrient deficiencies can be corrected quickly by adding the appropriate mineral to the solution.
You can either buy a pre-made nutrient solution, or you can formulate your own. Commercial farms generally mix their own as it can much cheaper to buy in bulk the individual chemical compounds.
Store bought solutions usually come in two separate bottles, one for macronutrients and one for micronutrients. They are separated because some elements are incompatible with each other when concentrated. For hobby hydroponics, the part A and part B solutions are usually the best options. They are simple to mix and only require a few materials: a container to mix them in, a dedicated measuring cup, and a stirrer. It is super important to be sure all the directions are read before mixing any chemical compounds.
Depending on the type of system, for example, with an Ebb and Flow setup, it is best to mix the nutrient solution in very large quantities. It can store enough nutrient solution to replenish the reservoir for weeks. For smaller systems, it is perfectly okay to mix a solution on an as-needed basis.
After mixing the solution, let it sit for a few minutes and settle, then check the pH and adjust as necessary. Starting off with a perfect pH will make it easier to maintain. Drops of pH Up or pH Down can quickly adjust the solution, but there are pH stable solutions as well.
Roots do not absorb nutrients as efficiently if the pH is too high or too low. Extreme pH levels can even kill your plant. This is where pH Up and pH Down come into play. These additives either raise, or lower the pH respectively.
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In closed hydroponics systems, the nutrient solution is recirculated and elements which are not absorbed in high quantities by plants (such as sodium, chloride, fluoride etc.) or released by the plant, build up in the hydroponic nutrient solution. In this case, testing the hydroponic nutrient solution frequently will help you decide on the timing for replacing the nutrient solution or dilute it with fresh water.
The electrical conductivity is a measure of the total salts dissolved in the hydroponic nutrient solution. Note that the EC reading doesn’t provide you with information regarding the exact mineral content of the nutrient solution. When we add nutrients (salts) to water we increase conductive potential for current through water and so increase the EC value.
By achieving a positive spiral of EC build-up in a plant, the plant also becomes more capable of absorbing water and retaining it. Because of this the plant doesn’t allow its water to evaporate very easily so it won’t lose the water that it has absorbed too soon. With plants that are too soft the intensity of the lighting will have to be reduced.