Nitrogen (N) Deficiency

A nitrogen deficiency is manifested by slow plant growth and subsequently by yellowing to a pale yellow. Unfortunately, these symptoms may also be caused by a range of other negative influences (for example, stagnant water, soil diseases or nematodes, etc.).

So how can you recognise when it is truly a nitrogen deficiency?

• First, the older leaves begin to turn yellow-green – from the top down
• Over time, the yellowing reaches the lower part of the leaf and begins to spread into the veins as well
• Next, growth stops and the affected leaves fall off
• Purple / reddish stem
  

Nitrogen deficiency can be recognised by the yellow (yellowish) leaves of the plant: if the roots’ absorption of this element is limited, chlorophyll (important for photosynthesis) disappears from the leaves. This happens first in the older leaves, at the lower part of the plant. The plant extracts nitrogen from these leaves and transports it to the young leaves and other areas where it is needed for further plant growth. Eventually, growth of the plant stops and the leaves fall off. In some plants (for example, cabbage), the leaves change colour to purple instead of yellow. Due to nitrogen deficiency, the plants and their fruits are considerably smaller. A plant with a nitrogen deficiency is much more susceptible to damage from diseases and insects. Unfortunately, these symptoms may also be caused by a number of other negative influences (for example, stagnant water, soil diseases and also nematodes).

Cause of the deficiency

Nitrogen deficiency can have several causes:

- Excess potassium, zinc and manganese in the soil or substrate.
- Too many chlorides in the soil
- The soil or substrate contains too little nitrogen
- Too high a pH level in the root zone (around the roots)
- Dysfunction of the root system caused by damage, disease or low soil temperatures
- Nitrogen is easily soluble and therefore easily leaches from the soil – which can cause its deficiency

How can nitrogen deficiency be prevented?

Usually, nitrogen deficiency does not appear immediately and you need to wait for the symptoms. During intense stress or growth, the plant is more susceptible to deficiencies. It is certainly worth making sure that you are using the correct fertilisers. Better fertilisers contain more than a sufficient amount of nitrogen and are therefore able to provide the plant with proper nutrition throughout its growth.

By using basic nutrients, which contain all the essential NPK components (Nitrogen N, Phosphorus P and Potassium K), you reduce the likelihood of nitrogen deficiency occurring. Always keep in mind that abiotic factors (such as temperature, light intensity, acidity, humidity and wind strength) can also have a significant effect on element deficiencies.

How can you deal with an element deficiency?

If you notice yellowing leaves on the plants, the situation can be addressed by applying a fertiliser with a high nitrogen content. Nutrients can also be applied extra-root (directly to the leaf) by using foliar fertilisers.

What function does nitrogen serve in the plant?

Nitrogen is absolutely essential for the plant. The plant needs nitrogen to form chlorophyll, which is indispensable in the process of photosynthesis. Nitrogen forms part of amino acids, from which proteins are subsequently formed, and these are necessary for all processes in plants. In general, it can therefore be said that nitrogen supports growth of plants, ensures higher quality of plant leaves and fruits, and further contributes to a larger harvest volume.