Deficiencies and excesses of nitrogen

Nitrogen (N):

Nitrogen as a nutrient is an important mobile element which is directly involved in the development of marijuana plants during all their life cycle. Depending on the stage of life at which these plants are, they need higher or lower amounts of nitrogen.

This element allows marijuana plants to produce proteins, amino acids, enzymes, chlorophyll, alkaloids and nucleic acids. It is the main cause of growth of the stem, leaves and branches, as well as being directly related to the plant's vegetative vigour.

It can be found in different forms: organic, ammonium and nitrate. The basic difference between these forms lies in the rate of absorption of nitrogen by the plant, being ammonium the fastest one and therefore the form that can cause an excess of this nutrient more easily.

On the other hand, nitrogen in the form of nitrate is readily absorbed by the plant, although the process is slower. It is for this reason that you can find a mix of both forms in nitrogen-based liquid fertilizers, to balance the nitrogen uptake of the plants and thus avoid an excess or deficiency of this nutrient in your plants.

If plants dont's have a sufficient amount of nitrogen available, they will suffer the lack - deficiency - of it; however, if nitrogen levels are kept too high, your plants will be over-fertilised.

Fertilisers can be of two types: mineral or organic. The mineral form is more rapidly absorbed by plants, for it doesn't need to be pre-processed by the micro bacterial life that lives in symbiosis with the soil in order to be absorbed by plants.

An optimum level of nitrogen in plants will result in:

• Vegetative vigor.
• Bright green leaves because of chlorophyll production.
• Increase in the number of leaves, size of the stem, fruits and seeds.
• Increased resistance of plants against fungi.
• Increased resistance against insects.
• Increased resistance to frost and hail.

Deficiency of nitrogen in marijuana plants

When cannabis plants aren't receiving a balanced nutrition and lack this element, abnormalities appear in their development, which can be seen in the plants' morphology and are often called deficiencies.

• The plant's growth is much slower.
• The leaves gradually turn yellow starting from the lower parts of the plant. Chlorosis begins at the leaf tips and moves towards the centre.
• The plants aren't strong enough to cope with pests, diseases and hailstorms.
• Flowering and seed production noticeably decreases.
• Great defoliation after serious chlorosis.
• The lack of nutrient moves bottom-up, affecting the younger leaves at a later stage.

To solve the problem as soon as possible you must add a nitrogen-enriched fertilizer to the nutrient solution so the plants have optimal levels of this nutrient available after a few days of watering.

It's worth noting that, when plants have these deficiencies, their yielding potential decreases, so it is important to maintain a balanced nutrition - until the flushing stage just before harvest - for a top quality harvest and the best possible yield.

Excess of nitrogen in marijuana plants:

By contrast, excess nitrogen in marijuana plants can also cause trouble, reducing their yield and flower quality. Nitrogen overfeeding can be noticed when the following symptoms appear:

• Excessive foliage growth.
• Weak stems.
• Delayed ripening of fruits, being less sweet.
• Claw-shaped leaves facing down.
• Poor bud combustion.
• Bright green leaves.
• Little resistance to pests in general.

To solve this, wash the plant roots using triple the capacity of the pot of water and low levels of EC. Test the EC (water conductivity) to find out the salt saturation in the substrate, and if the case is extreme, don't stop washing the roots until the nutrient levels in the substrate are the same than the water we are using for flushing.

There are products specifically designed to dilute salts and help washing the soil for a quicker recovery.

How does cannabis recover from excess nitrogen

Cannabis, as mentioned above, is capable of showing its health through its look, so it is easy to find out the health state of our plants by carefully observing their leaves, colour, shape, etc.

Whether the plant has been over-fed or if it has suffered a lack of nitrogen, cannabis always takes a few days to recover. The speed of recovery will always depend on the degree of deficiency or excess suffered by the plant, so early detection will always allow a better recovery of the plant in a shorter period of time.

Depending on the substrate and fertilisers used, plants may recover slower or faster. In hydroponic systems, the speed of recovery is much faster than in crops grown in soil with organic fertilisers. As mentioned at the beginning of this post, the form in which these nutrients are dispensed greatly determines the absorption speed.

During the growth phase and in the event of a light over-fertilisation, you will need to reduce or eliminate the fertilizer for growth used in your nutrient solution.

If you are using marijuana additives, you can keep on using them normally as they contain no nutrients, only elements that make the plant metabolize the excess nutrients and produce more leaves, branches...in short, they allow the plant to use all the available nutrients correctly.

During the flowering phase, if you over-fertilise your plants you will need to act according to the stage of the crop. If it happens during the first two weeks after the photoperiod change, you should do as you would during the growth phase, since the plants still grow almost until the 3rd week, which is when buds begin to develop.

However, if the plant is already starting to bloom, excess nitrogen is not very common, but if this is the case, remove the fertiliser used and add a PK-based fertiliser, which contains no extra nitrogen. In this way, your plants can continue to produce buds whatever the stage they are while the excess nitrogen is eliminated. If the over-fertilization is heavier, you can wash the roots previously to clean the substrate from the excess nutrients. After this, water thoroughly with the right amount of PK.