Are you really sure you are using hydroponic fertilizers correctly in your cultivation ? The fertilizers used in soilless plant cultivation are completely different from those you would use when growing in soil.

Hydroponics is among the most innovative and effective indoor growing techniques. This system allows you to have greater control over the development cycle of your plants. However, provided you know how to keep the 3 fundamental factors in balance, namely light , humidity and nourishment .

Fertilization in a hydroponic culture is vital, because it is necessary to replace and dose those micro and macro nutrients that the plants would normally absorb from the soil in which they are planted.

That's why we thought we'd create an in-depth guide to help you understand how to feed your plants well and obtain healthy, strong and lush crops.

Article summary:

Hydroponic fertilization how to use them

Depending on the technique you adopt (soil, hydroponics, aeroponics) and the cultivation substrate you choose (expanded clay, coconut fibre, rockwool, perlite etc...), a specific fertilizer must be used.

This is especially true in hydroponics and aeroponics where the cultivation substrate - i.e. the substance where sowing takes place and the root system of the plants develops - is inert , i.e. it does not contain the same nutrients found in normal soil or potting soil.

Therefore it needs to be constantly watered with a nutrient solution that has the most correct combination to ensure you get the best possible yields, both in terms of quality and quantity.

Hydroponic nutrients come in many different shapes and types. It is important that they are

  1. Suitable for the type of cultivation and substrate used;
  2. Complete , i.e. they provide all the trace elements necessary for the plant to grow;
  3. In soluble form , so as to be better assimilated.

In hydroponic cultivation, since the water is totally or almost completely devoid of nutritional elements, fertilizers must be added in a well-balanced form and in a correct ratio to satisfy the phenological stage of the plant (vegetative state, flowering, fruiting).

The fertilizer is dissolved in a water-based nutrient solution, which is why it is necessary for it to be a water-soluble fertilizer for hydroponics , so that the substances can be absorbed directly by the roots of the plants.

Organic fertilizers for the soil should be avoided , as in addition to often being too dense and lumpy to work with pumps and irrigation systems, they also undergo strong variations in acidity and tend to rot if in contact with water and air in systems with recirculation, or worse on rock wool.

What we would like to underline is that the correct use of fertilizers for hydroponics is certainly very important for this type of technique. But at the basis of a healthy and fruitful hydroponic culture, the correct pH and EC (TDS) levels in the nutrient solution are also crucial .

Only a well-balanced solution of EC and pH allows for the rapid absorption of nutrients and success in cultivation. Very superficially we could say that a pH between 5.5 and 6.5 is a correct value for almost all your indoor cultivations with flowering and fruit plants.

As regards the EC (tds) , which measures the quantity of fertilizer in the nutrient solution, the value varies depending on the plant species grown. However, a level between 0.8 and 1.8 is the most appropriate depending on the growth or flowering phases.

The nutrient solution - which naturally tends to consume and decrease as the days pass - can be topped up gradually, always rigorously stabilizing the pH and EC levels. However, it is a good idea to empty the tank, clean it if possible, and add new solution every 7-10 days maximum.

We have not forgotten another very important aspect in fertilization: water .

Being the basis for the nutrient solution it is important that it is of good or acceptable quality .

Water that is too hard or calcareous certainly requires correction with products based on phosphoric, nitric or potassium acid in order to maintain the correct pH levels.

Often, however, it happens that we have excessively saline water, therefore it is important to check the percentage of Total Dissolved Solids (TDS) which must not exceed levels of 200-350 mg/l , otherwise it will be necessary to filter the water with a special reverse osmosis filter .

But what are the best fertilizers for hydroponics ? Continue reading the next paragraph to find out.

Read also our guide : " EC in Hydroponic Cultivation ".

Which nutrients are suitable for hydro culture

Choosing the right fertilizer is fundamental when approaching hydroponics, because it is from this that plants absorb all the essential nutrients. In hydroponic cultivation, as with any substrate, the addition of micro and macro elements allows the plant to absorb the substances necessary for correct development.

The 3 main elements also called macro elements that your plants need are:

  1. Nitrogen (N);
  2. Phosphorus (P);
  3. Potassium(K).

These elements must be balanced correctly and the percentage must necessarily vary depending on the growth or flowering phases.

Nitrogen (N) stimulates chlorophyll photosynthesis , increasing the vegetal development of branches, leaves and stems of the plant. Therefore it is an element suitable for the vegetative phase of the plant, not the potassium (K) necessary for the development of the roots in this phase.

For plants, potassium (K) is of fundamental importance for correct growth as it is a fundamental element of numerous biological processes, such as the function of sugar synthesis, on which the organoleptic properties of plants and therefore aroma and flavor depend . of flowers and fruits.

Potassium also regulates leaf transpiration by stimulating the opening of the stomata, which are superficial glands necessary to eliminate excess water vapour.

Phosphorus (P) is a necessary element for the flowering phase. These elements are linked to the formation and development of roots, branches and above all flowers and to the structure of shoots. For this reason, during the flowering phase it is customary to provide fertilizers with a higher percentage of phosphorus, in order to produce abundant and quality yields.

Then there are secondary nutritional elements (called micro elements ) which are equally important to the plant in different phases of its development, but not as essential as the three primary ones. Some of these elements are:

  • Calcium (Ca);
  • Iron (Fe);
  • Magnesium (Mg);
  • Sulfur (S);
  • Boron (B);
  • Molybdenum (Mo).

Small quantities of these elements are added to the nutrient solution in hydroponics, in order to provide the plants with the full range of minerals it needs.

Hydroponic nutrients wich is the best choice

Plants require different percentages of Nitrogen (N), Phosphorus (P) and Potassium (K) depending on whether they are in the vegetative or flowering phase.

Most organic fertilizers for hydroponics are marketed by growth phase and have the exact concentration on the label, so you can't go wrong.

For example, a package of nutrient solution labeled NPK 20-20-20 will contain 20% Nitrogen, Potassium and Phosphorus. The remaining percentage refers to the micronutrients present.

The relationship between the 3 macroelements varies depending on the phase of a plant's development cycle. During vegetative growth the nitrogen content must be higher than that of potassium and phosphorus. On the contrary, when it comes to flowering they will have to increase potassium and phosphorus, and decrease the amount of nitrogen.

All the advantages of using fertilizer for hydroponics

The hydroponic cultivation technique is widely used and appreciated above all for the many advantages it offers:

  • Versatility, economy and simplicity of the system;
  • Good final yields;
  • Absence of diseases and parasites;
  • No seasonality constraints;
  • Speed ​​and explosive growth of plants.

Likewise, the use of fertilizer is also particularly advantageous in hydroponic cultivation.

First of all, the main advantage is that of being able to effectively and precisely control the nutrient solution to be administered to the plants, guaranteeing them the right quantity of macro and micro elements. This goes hand in hand with a flexibility in fertilizer management in hydroponic systems that is absent in soil cultivation.

We have already said it in the previous paragraphs, but we repeat it anyway because it is important: correct use of fertilizer is the starting point for successful hydroponic cultivation.

This means respecting dosages and administration times, nourishing the plants adequately for the development phase they are in and, above all, paying attention to nutritional imbalances and deficiencies .

In hydroponic cultivation, almost all the problems related to nutritional deficiencies or imbalances that occur on plants are caused by the incorrect use of fertilizers.

Let's take a species of flowering light cannabis as an example: poor fertilization could weaken the plant, whereas excessive fertilization could even burn the entire plant system and in some cases lead to the death of the plant itself.

No less important for correct fertigation and for the absorption of nutritional elements is the accuracy with which the EC and pH values ​​are kept stable. Let's see why in the next paragraph.

Importance of ec and ph control in hydroponics when using fertilizers

Another common cause of incorrect fertigation is pH fluctuation . pH is the unit of measurement that allows you to check the acidity or alkalinity of the nutrient solution. Nutrients are absorbed more easily when the pH is at a value considered optimal.

On the contrary, a pH that is too alkaline or too acidic prevents the complete absorption of some micro and macro elements vital for the growth and health of plants which can therefore manifest nutritional deficiencies.

In a hydroponic system, plants will absorb nutrients best with a pH range of 5.5 to 6.5, with the optimum value being around 5.7 .

The oscillation of electrical conductivity (EC) can also have a negative impact, compromising the yield of a crop.

Electroconductivity determines the salinity of the nutrient solution and, therefore, the concentration of the fertilizers inside. The higher this value, the greater the ability to conduct electric current.

If the EC value is high it means that the plant is absorbing more water, if it is low it means that it is absorbing more minerals. This is why it should be kept in balance and varied according to the needs of the plant. Generally speaking, optimal values ​​are:

  • 0.6-1.0 in the germination phase;
  • 1.0-2.0 in the growth and first flowering phase;
  • 0.6-1.0 in final flowering.

What does all this make you understand? That the use of EC testers and pH testers - even cheap ones - is essential, and you want to undertake hydroponic cultivation. Only these tools can help you control the substrate values ​​and ensure that they are suitable for the development of your plants.

Visit the Grow Shop Italia website and discover our offer of the best organic fertilizers to start growing hydroponically now.