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.

Nitrogen process

Nitrogen process

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.

Nitrogen deficiency

Nitrogen deficiency

  • 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:

Claw-shaped leaves

Claw-shaped leaves

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.

Deficiency of nitrogen progress

Deficiency of nitrogen progress

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.

Plant recovering from nitrogen deficiency

Plant recovering from nitrogen deficiency

10 Comments


10 comments on “Deficiencies and excesses of nitrogen

  1. ronald gard

    Too much steer manure was put at the bottom of my plants they are suffering from too much nitrogen they have been in the ground for a month can anything be added to the soil to reduce the nitrogen

    1. Dani Alchimia

      Hi Ronald,

      You can use other plants like squash, cabbage, broccoli and corn which use lots of nitrogen to grow and act as sponges of this element. Using dry mulch also helps to reduce nitrogen. You can also add wood chips to the soil.

      Hope it helped!

  2. Janet eschmamm

    My husband put way to much cow shit water in my plants and in3 days they went from strong green healthy georgous plants to Brown wilty sad looking plants. They are way to big to flush the roots. Please help me makes me want to cry when I look at them.

  3. Janet eschmamm

    What can I do for my plants they have way to much nitrogen wilting leaves turned brown and are curling. They are way to big to flush the roots.. Put way to much cow shit water to them. They were very healthy plants . I don’t want to lose them. What can I do

    1. Dani Alchimia

      Hi Janet,

      You can try to water your plants with water+enzymes, they’ll help to break down accumulations of nutrients. I know some people plant other vegetables to “clean” the soil from excess nutrients, like roses,corn, lettuce, tomatoes, squash, cucumbers, mustard and cabbage (corn and mustard are fast to start). Still, you should really flush them with enzymes no matter how big they are, simply use more water!!

      I’ve also found some poeple add wood chips to the soil to lock up excess nitrogen.

      Hope it helped!

  4. H.M. Hari

    I have small kitchen garden and have been facing sever problem. Bottle gourd and ridge plants which quite look quite healthy setting female flowers in very large numbers but not a single fruit is maturing. All are turning brown and subsequently falling off. What is the reason and what should I do in order to retain fruits.

    1. Tim Alchimia

      Hi, thanks for your question. Sorry to hear about your plant problems. Are you saying the flowers turn brown and fall off before fruiting? It sounds to me like the female flowers aren’t being pollinated. Are you seeing any male flowers appear? Cucurbit male flowers are usually on a longer, slender upright stalk. An easy solution to ensure fecundation would be to hand-pollinate the plants yourself using a small brush or cotton bud to apply the male pollen to the stigma of the female flowers.

      It could be that your garden isn’t being visited by pollinating insects, so a good idea to encourage them is to plant a variety of flowers that will attract bees, butterflies etc.

      Al the best!

  5. Darrin Fulghum

    Can harvested flowers contain too much nitrates to affect it or is it more likely poor drying/curing ??? My grow partner used a higher than normal nitrogen fertilizer this year. Now after harvest he says the buds are full of nitrates and when smoking them we are giving ourselves nitrate poisoning..
    Is any of this true??? Am I in danger?? If true can it be removed??

    1. Tim Alchimia

      Hi, I’m not sure about nitrate poisoning, I’ve never heard of that before, I know that weed that has too much nitrogen fertiliser at harvest time can be very harsh and unpleasant to smoke, because of high levels of chlorophyll caused by too much fertiliser. However I don’t think the flowers themselves will have a high nitrate content, I’d be really surprised if you were actually poisoning yourselves. If you want to be sure about your health then maybe find a lab that can test the flowers for nitrate content.

      The best thing to do would be to leave the weed to cure properly over a few months, which ought to reduce the levels of chlorophyll and other harsh tasting compounds. If that doesn’t work then personally I’d make hash with the flowers, by separating the resin from the plant material you can sidestep that awful flavour caused by too much nitrogen fertiliser.

      Next time you grow, remember that more fertiliser does not necessarily mean more buds, and if you want really tasty weed, just use much less fertiliser than the recommended amount.

      Good luck, I hope it ends up tasting better.

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