In the Lensli Academy we regularly inform you about practical situations that we encounter in the sector, we talk about insights gained in practice, we give you cultivation tips and we share our knowledge about other interesting substrate-related matters.

With the increasing use of raw materials other than peat, we increasingly encounter nitrogen fixation in cultivation, also known as nitrogen immobilization or nitrogen fixation. This can often be recognized on the plant by a lighter color of the leaves and reduced growth. This is often unmistakably reflected in analyses.

Many raw materials (temporarily) remove nitrogen from the nutrient solution. Consider, for example, wood fiber, bark products and the Basic BioMix. But before we go into this in more detail, let's first ask the question:

Why is sufficient available nitrogen so important for the plant?

Nitrogen is an essential element for the growth and development of plants. It is part of proteins, enzymes, chlorophyll and DNA. Plants can absorb nitrogen from the substrate in the form of nitrate (NO3-) or ammonium (NH4+). The substrate may contain nitrogen from organic or inorganic sources.

Did you know that no less than 70% of the available nitrogen is incorporated into the chlorophyll of the plant?

Nitrogen fixation is the process by which nitrogen is converted from an available form (nitrate or ammonium) to an unavailable form (organically bound nitrogen). This process can take place by microorganisms living in the substrate, such as bacteria or fungi. They use nitrogen as a nutrient source for their own growth and metabolism.
Nitrogen fixation can have both positive and negative effects on the substrate and the plant. On the one hand, it can contribute to the improvement of the organic matter and the structure of the substrate, and to the suppression of pathogens. On the other hand, it can lead to a shortage of nitrogen for the plant, reducing growth and quality.

The extent and speed of nitrogen fixation depends on several factors, such as:

• The composition and moisture content of the substrate;
• The amount and form of nitrogen added;
• The temperature and pH of the substrate;
• The activity and diversity of the microorganisms;
• The age and origin of raw materials.

As a grower you can deal with this by taking a number of measures, such as:

• Choosing a suitable substrate that meets the requirements for water and air balance, nutrients and pH;
• Regularly checking and analyzing the substrate for nitrogen content and other parameters, by means of a soil (soil) analysis. Of course we can support you with this.
• Adjusting watering and fertilization to the needs of the plant and the properties of the substrate;
• In collaboration with the substrate supplier, compensate part of the immobilization with fertilizers at the start.

By taking the above measures you can achieve an optimal balance between the available nitrogen in the substrate in relation to the fertilization strategy you use.

When starting, ask your Lensli substrate specialist how much nitrogen is needed in the substrate to start with a good balance. Here is a calculation model in collaboration with the RHP about this developed.  For more information about nitrogen you can also visit the RHP website: Focus on nutritional elements: nitrogen – RHP.

Do you have questions or would you like to know more about this subject? Please contact your Lensli account manager or our Substrates Technical Product Manager Nick Vollmer by email n.vollmer@lensli.com or telephone +31 (6) 51269415.

We are happy to talk to you.