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Hydroponics - Optimal growing conditions

Hydroponics - Working with water

The term hydroponics derives from the Greek words for water (hydro) and work (ponos) - "working with water".

In a hydroponic system plant roots do not grow in soil, but in nutrient-enriched water. Hydroponics is a good method for growing plants, vegetables and herbs - indoor and outdoor.

It has many advantages over the classical cultivation in soil and is particularly suitable for urban gardening on balcony, roofs or indoor.

What do plants need to grow?

Principle of active water culture | hydroponics

Compared to the cultivation in soil, the plants get everything they need to grow through the nutrient solution, delivered directly to the roots. Nutrients do not have to be dissolved out of the earth by pouring. This also saves the plant energy because it simply gets to the nutrients. The nutrient solution must have a certain temperature and be enriched with oxygen. Such a controllable hydroponic system provides optimal plant growth, is resource-saving, less labor-intensive and significantly more productive than cultivation in soil.

Influencing parameters in hydroponic plant cultivation

If you study plant cultivation literature more intensively, regardless of the method of cultivation, the subject seems very complex and complicated. This is certainly the case in commercial cultivation.

Understanding the basic relationships and influencing factors on the growth behaviour of plants and using available systems for the hydroponic cultivation of plants will make cultivation much easier and feasible for everyone. The success is quickly evident.

Light - at least 8 - 10 hours a day

Also in hydroponic cultivation light is essential for plant growth. It is ideal when sunlight is available. If not, energy-saving but nevertheless powerful LED (light emitting diode) lamps can help. There are special plant LEDs with optimum wavelength ranges available for this purpose.

Oxygen O2

The plants need oxygen in its rhizomes for growth. A high content of dissolved oxygen in the water improves the absorption of fertilizers into the plant. If there is sufficient oxygen, the nutrient content can be reduced, but the plants still grow quickly.

Water / Nutrients - Electrical Conductivity EC

Water is an important element for plant growth and provides the plant with moisture, necessary for metabolic processes. It also carries nutrients and contains dissolved oxygen. Important properties of water are its hardness, salt content, pH value and alkalinity. The proportion of dissolved minerals is checked by measuring electrical conductivity (EC), expressed in µS/cm, sometimes also in mS/cm (1000 µS/cm = 1 mS/cm).

The appropriate nutrient selection and dosage are important. In order to avoid under- or overfertilization, the nutrient content is checked by measuring the electrical conductivity (EC). The higher the salt content, the higher the conductivity.

Soft water - approx. 0 - 140 µS/cm
Hard water - > 840 µS/cm

Depending on the hardness of the water, water already contains a certain amount of dissolved nutrients. The missing nutrients are added using hydroponic fertilizers. At the beginning of growth and in the final phase less nutrients are needed.

A conductivity between approx. 1000 - 2000 µS/cm covers almost all needs. As an average guideline we consider 1500 µS/cm as a functioning value (empirical values). However, it is always important to observe the plants.

Manufacturers of hydroponic fertilizers provide information on dosage and conductivity values, depending on the growing stage.

Carbon dioxide CO2

CO2 is an important component in the growth process of plants. It is advantageous that CO2 is absorbed and processed by photosynthesis under the impact of light. The oxygen O2, which is important for us, is released.

The gas exchange takes place at stomata, mostly on the undersides of leaves. If it is too hot or the roots too dry, the stomata close and the metabolism of the plants slows down. This is where hydroponic cultivation systems have their advantages. As the root area is always supplied with water, the metabolism is not slowed down. If sufficient CO2 is available, the plants can grow unhindered.

Temperature 18 – 25°C

Temperature can only be influenced to a certain extent. Knowing the influence of temperature on growth processes is important. As the water temperature rises, the dissolved oxygen content decreases - from 0 - 30°C it is halved in the water. As the temperature rises, however, the metabolic activity increases at the same time, and the plants actually need more oxygen.

Favourable growth conditions exist in the range of 18 - 25 °C, but growth also takes place below or above this temperature. This applies to water as well as to the ambient climate. 

pH value for hydroponics - approx. pH 6.2

The acidity (pH value) of the water influences the supply of nutrients to the plants. In a pH range of 5.5 - 6.5, the most diverse nutrients can be absorbed best by the roots, which is independent of the cultivation method. The pH value should be measured and adjusted to create favourable growing conditions.


In photosynthesis, high-energy biomolecules (carbohydrates) are produced from low-energy substances (H2O and CO2) through light energy. This requires light-absorbing dyes such as chlorophyll, that transform light energy into the chemical energy required for this conversion process.