How do you recognize a nitrogen deficiency in plants?

A nitrogen deficiency in plants occurs when the plant is insufficiently able to absorb nitrogen from the substrate. Because nitrogen simply washes away through rain, over-watering of the plants can easily cause a nitrogen shortage.


Nitrogen is indicated by the symbol 'N' and makes up about 78% of the earth’s atmosphere. However, the nitrogen in the atmosphere cannot be directly absorbed by plants.

Nitrogen is an element that is vital for the functioning of the plant and is an important building block of proteins, chlorophyll, vitamins, hormones and DNA. In addition, it is involved in many enzymatic processes. A nitrogen deficiency in plants is directly reflected in a reduced plant metabolism and therefore a reduced growth.

Functions of nitrogen

Nitrogen can enter into a compound with different substances, but for the plant it is especially easy to absorb in the forms of nitrate (NO3-) and ammonium (NH4+). The plant therefore mainly absorbs these forms of nitrogen through the roots.

During the vegetative phase (the growth phase) of the plant, nitrogen plays an important role for cell division and the production of biomass. The production of leaves in particular requires a lot of nitrogen. Nitrogen is used in the construction of all proteins and enzymes of an organism.

Nitrogen is especially important for photosynthesis. Plants need nitrogen for the production of chlorophyll. Photosynthesis cannot take place without chlorophyll and therefore no energy can be produced. There is no growth without energy. In photosynthesis plants convert carbon dioxide (CO2) and water (H2O) into glucose and oxygen (O2).

How do you recognize the symptoms of a nitrogen deficiency?

The symptoms of a nitrogen deficiency are striking, because as soon as there is a shortage of nitrogen, the edges of the oldest leaves turn yellow, because less chlorophyll is produced. Later, these leaves turn brown because of the lack of chlorophyll and they curl up, after which the leaves eventually die off.

Since nitrogen plays such an important role in the growth of the plant, all basic nutrients contain nitrogen in order to provide a basic need, so that a nitrogen shortage hardly ever occurs.

Some growers fear a shortage and give too much nitrogen. The result is that the plant indeed grows faster. A consequence, however, is that the plant makes more cell elongation and gets large cells with a lot of protein, but thin cell walls. The plant then becomes dark green and limp and becomes more sensitive to diseases.

Causes of a nitrogen deficiency

A nitrogen deficiency can have several causes, but hardly occurs when using quality plant nutrition and a good substrate. The most common causes are

- a too low ratio to potassium, zinc and manganese in the substrate or food.

- too little nitrogen available in the substrate. This is more common with an ‘open structure’, because the nutrient water simply washes away the present nitrogen.

- Too high pH in the root environment.

- Certain plant diseases like fusarium piggyback on the transport system in the plant and thus affect plant health.