Nitrogen Deficiency in Cannabis Plants

Nitrogen deficiency in cannabis plants is one of the most common problems a grower will come across. It will begin by displaying yellow leaves at the bottom of your plant. This yellowing will continue to make its way up the plant, and slow down growth. 

Nitrogen is a very important nutrient for plant growth. It is used at different levels throughout the life cycle of a cannabis plant. It is very soluble, and can easily be washed out of your medium. 

Because of these two factors, a nitrogen deficiency can arise quickly, and may go unnoticed for a while before it is diagnosed. 

In this guide we will cover every aspect of nitrogen deficiency in cannabis plants. The cause and effects, the best ways to treat a nitrogen deficiency, and how you can prevent the problem arising again in the future. 

First off we should begin by explaining what a nitrogen deficiency is. 

What is Nitrogen Deficiency in Cannabis Plants

A nitrogen deficiency in a cannabis plant is when the level of nitrogen available to the plant is too low. Because the available nitrogen is below what the plant needs, it will not be able to grow to its full potential. 

Cannabis plants use nitrogen for many things. It is used for making stems, leaves and branches of a cannabis plant, but also makes essential proteins that the plant needs to function. 

The demand for nitrogen increases throughout the vegetative stage of plant growth. But, cannabis plants will use less of it during the flowering stage. Because the demand for nitrogen is higher during “veg”, deficiencies are more common. This is the time you are most likely to see a nitrogen deficiency. 

What Causes Nitrogen Deficiency in Cannabis Plants

The cause of nitrogen deficiency in cannabis plants is usually one of three things:

1: Not Enough Nitrogen Available to the Plant

A cannabis plant will take all of its nitrogen from the medium ( Soil/ Coco/ Hydro). If the level of nitrogen in the medium is too low, the plant will not have access to enough, and a deficiency will arise. This can happen because the plants are using more nitrogen than you are giving them.

In some cases, especially when growing organically, microbes and other life forms in the soil can use the nitrogen up before the plants do. You need to be able to spot the signs of nitrogen deficiencies and excess. This way you can find the right balance for your plant.

2: PH Imbalances in Your Plants Medium

If the pH of the medium your cannabis plants are living in is not within the correct range, your plants will not be able to eat. 

As you can see from these 2 charts, certain nutrients are “locked out” when the pH is not within range.

Sometimes there are plenty of nutrients available in the medium, but the plants are not able to use it due to pH problems. As you can see, if the pH of the medium is too acidic, nitrogen will be locked out and the plant will not be able to use it. This can cause a deficiency regardless of how much nitrogen is in the medium.

3: Over Watering and Flushing Out the Nitrogen

If you are watering your plants a lot, and seeing a lot of run off, then you may be washing away all of the nitrogen too. Nitrogen will dissolve easily into water, and must be replaced often, especially when the plant is in “veg”. 

Not only does a cannabis plant use a lot of nitrogen, but it is easily washed out of the medium. Along with pH imbalances there are a few common causes of nitrogen deficiency in cannabis plants. 

A nitrogen deficiency is one of the most common deficiencies you will get on your cannabis plants. But it is also one of the easiest to diagnose and fix. There are a few tell tale signs of nitrogen deficiency that will help you easily diagnose the problem. 

What Does Nitrogen Deficiency in Cannabis Plants Look Like

Nitrogen deficiency in cannabis plants will first display as yellowing (Chlorosis) of the older leaves, at the bottom of the plant. As the deficiency gets worse, the yellowing will move further up the plant, and growth will be slowed down.

Here is a list of symptoms of nitrogen deficiency in cannabis plants:

1: Plant will grow slower and shorter
2: Lower/ older leaves will turn yellow
3: Leaves become slightly droopy
4: Tips of yellowing leaves curl
5: Leaves falling off the bottom of the plant

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As you can see, the most common thing to look out for are yellowing leaves at the bottom of the plant. These symptoms can also be confused with potassium deficiency, as this causes yellow leaves too. But, a potassium deficiency will display yellow leaves, with purple stems. Nitrogen deficiency will not show purple stems, but more display signs of chlorosis in the leaves. 

Why Does Nitrogen Deficiency Lead to Chlorosis 

Chlorosis in cannabis plants is when leaves turn very yellow. This is caused by a lack of chlorophyll in the plant matter. 

Chlorophyll is a green pigment in plants that captures light and gives the plants its green colour. It is a major factor in photosynthesis.  A large part of the chlorophyll molecule is made out of nitrogen:

“The chlorophyll molecule consists of a central magnesium atom surrounded by a nitrogen-containing structure called a porphyrin ring; attached to the ring is a long carbon–hydrogen side chain, known as a phytol chain”

Brittanica.com

So you see, when there is not enough nitrogen available to your cannabis plants, they can not make enough chlorophyll. With a reduction in chlorophyll, comes a reduction in the green pigment. This is why a nitrogen deficiency in cannabis plants can be identified by yellowing leaves. 

How Does Nitrogen Deficiency Affect Cannabis Plants

Because nitrogen is used in so many different ways by a cannabis plant, when a deficiency starts, it will cause a lot of problems. Once the plant is starving for nitrogen, it will start moving it from the lower leaves, to the new growth. This is where it is needed the most. 

But this can not go on for long. It will not take long for your plant to start losing leaves and losing lustre over the whole plant. 

Your plants will slow down on the production of chlorophyll, which in turn slows the whole digestive process. A nitrogen deficiency in a cannabis plant can cause your plants to stop eating all together. Without nitrogen, there is no chlorophyll. Without chlorophyll, there is no photosynthesis.

Cannabis plants with a nitrogen deficiency will grow much slower, and shorter than plants that are fed correctly. It is important to make sure your plant is getting the right amount of nitrogen at all times. 

How to Treat Nitrogen Deficiency in Cannabis Plants 

The most likely cause of a nitrogen deficiency is going to be a lack of nitrogen available in the medium. This is an easy fix if you’re growing with salt based nutrients. Simply raise the amount of A & B you’re giving to your plants. 

You should raise the EC/ TDS/ PPM of your nutrient solution slowly, and be careful not to over feed. 0.2 EC rise is plenty. Feed your plant a little more and wait 24 hours to see the results. Usually in hydroponic mediums, you will see changes within 24 hours. 

It is a good idea to check the pH of the medium too. You can do this by testing the reservoir of your hydro setup, or by testing the run off after you have fed your plants. If the pH is not within the correct range, then make sure that is adjusted before you increase the feed. 

How to Treat Nitrogen Deficiency in Cannabis Plants Grown in Soil

Growing cannabis in soil can differ from hydroponics. If you are growing in soil using salt based nutrients, then you can just increase the EC a little and feed your plant more. This should deliver more nitrogen to your plants. 

On the other hand, if you have a nitrogen deficiency and you’re growing cannabis organically, then you will need an organic solution to the problem 

• Alfalfa Meal: Contains nitrogen, but also contains phosphorus and potassium so be careful not to over feed. Alfalfa meal also encourages beneficial microbes to thrive. 
• Animal Manure: Grazing animal manure is best and can be an excellent source of nitrogen. If you’re using manure, it should be well composted before use as it can burn your plants! 
• Blood Meal: Blood meal is heavy in nitrogen. It is easily dissolved into water and fed to your plants. But of course be careful, too much can cause damage to your plants, increase the feed gradually. 
• Compost: Though you can’t be sure exactly what is in your compost, it can be used to top dress your plants to increase the amount of nutrients in the soil. There will be plenty of fresh nitrogen available in compost. But it will contain other nutrients, so be careful not to over feed!
• Fish Meal: A source of nitrogen made from fish oil. Using fish oil is fast acting, and can be mixed with your water. This means you can feed it directly to your plant and see quick results. 

Can Overwatering Cause Nitrogen Deficiency

Nitrogen is very easily soluble in water. Every time you add water to the medium, the nitrogen will dissolve into it. If you get a lot of run off when you water your plants, you could be washing out a lot of nitrogen that the plant needs. 

This isn’t so much of a problem for hydroponics and coco growers, as feed is always available in the medium. But growing in soil can be a little more tricky. 

Some soil growers will feed their plants once, and then only give them water on the next one or two feeds. This can cause nitrogen deficiency, as the plants are not only using the nitrogen in the medium, but it is also being washed away. Be careful of how much run off you get when you grow in soil. You do not want to wash the nitrogen away. 

To Summarise:

Keep a close eye on any changes to the lower leaves on your plant. Look out for the symptoms explained above. If you suspect a nitrogen deficiency in your cannabis plants, then you can always ask for help in our cannabis growers forum. 

It is a common problem most growers have. It is all part of learning how to grow weed. Easy to fix, but be very careful not to go too far and over feed. 

It is easier to fix an under fed plant, than it is to fix an over fed one! Thanks for reading Percys Growers!