What is Nitrogen Deficiency and How to Fix It?

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Added 14 March 2022

Are the lower leaves on your cannabis plant turning yellow and wilting? Unless the plant is nearing the end of its life cycle, it's probably a sign of nitrogen deficiency. Or, another sort of nutrient deficiency, but we will discuss that in this article. 

Nitrogen is vital for your plant's growth, and a lack of it can spell trouble for your plant. But thankfully, this is one of the most common issues growers face and one of the easiest to fix. 

This article teaches what nitrogen deficiency is and how to fix it.

Nitrogen and Cannabis

nitrogen deficiency

Whether you are growing cannabis or chilies in your backyard, your plant is going to need a lot of nitrogen through its growth stage or the vegetative stage.

Nitrogen is one of the primary macronutrients. And nitrogen (N) is the first element you see in fertilizer bags, when described as NPK, with the other two being phosphorus (P) and potassium (K). So, nitrogen is an essential nutrient for your cannabis plant that helps it grow and thrive, and it does so in many ways.

Nitrogen is an essential part of your plant's chlorophyll, making photosynthesis possible. So, without nitrogen, your plant cannot produce energy and sugars, leading to stunted growth.

It is also crucial for amino acid production — the building blocks of proteins that allow the cells to develop and enable biochemical reactions. 

Even the plant's DNA relies on nitrogen, a crucial nucleic acid component. So, nitrogen is vital for the plant's growth and reproduction processes.

As you can see, without nitrogen, your plant can't grow stems and leaves properly. Once a healthy plant becomes deficient in nitrogen, the branches and buds also don't develop adequately. Overall, the plant becomes very weak and struggles to reproduce. 

Symptoms of Nitrogen Deficiency

Nitrogen deficiency in cannabisImage credit - Mikumiku 

Sometimes, this nitrogen fails to reach the plant properly. This can be due to various reasons, as discussed below, but it can cause many health problems for the plant. Here is what nitrogen deficiency looks like in cannabis.

Initially, the tip of the leaves start losing their colors — they start turning pale yellow. This discoloration then starts spreading inward on the leaves. Once the color has spread all over the leaf, the leaf begins to turn brown and wrinkles up. Eventually, it falls off.

Sometimes, the leaves may also appear lime green and eventually turn yellow. They may look pale like something's amiss. For a beginner, it may be difficult to spot the symptoms at first because you won't see any unusual spots on the leaves apart from a slightly yellowish color. However, it won't be a problem once you've grown several plants. In addition, you may not identify the problem if you rarely take a look at the plants without the lights on. Artificial lighting, including HIDs and LEDs, can make it hard to identify problems. Therefore, make it a habit to observe the plants for a few minutes with no lighting. 

Once you spot the discoloration, you'll have enough time to act unless the plant is almost dead, but it's rare. Since nitrogen is a mobile nutrient, the deficiency symptoms begin in the lower leaves first, gradually moving up if the issue is not fixed, affecting the newer, higher leaves.

Mobile nutrients are those that travel from one place to another. Thus, if there's a nitrogen deficiency in young leaves, nitrogen can travel from the lower or older leaves to the younger ones. The leaves at the top or young leaves get adequate nitrogen from the light to aid photosynthesis. However, if the young leaves lack nitrogen, they tend to "borrow" it from older leaves. The older leaves will then turn yellow and drop off. Eventually, even the younger leaves will struggle and drop off when they don't get nitrogen. 

Lack of nitrogen hampers the plant's ability to grow, so you may also see other symptoms accompanying leaf discoloration. Your plant's growth will slow down, and it will become more prone to pests, mold, and other diseases.

In addition, the plants will grow very short and lack vigor. Since there's a lack of protein, the plants will struggle to flower. In short, the plants will display stunted growth. If you don't fix the problem soon, the buds will become dormant and stop development. 

Final blooming stage

In this image, you'll see that the buds are mature but there are signs of nitrogen deficiency. Note that your plant may naturally show signs of nitrogen deficiency during the flowering stage and harvest. In such cases, you don't need to worry. Plants stop absorbing as much nitrogen during the end of their growth cycle to focus their energy on bud development. Too much nitrogen at this time can delay the bloom and harvest. This is why most bloom fertilizers come with low nitrogen amounts.

On the contrary, if you see the leaves on the higher tier discoloring first, it is not a sign of nitrogen deficiency. It's a symptom of other forms of deficiency. Remember, it's nitrogen deficiency only if it starts with older leaves and spreads to the top or if the entire plant appears lime green or yellow. 

We have mentioned that it's easy to fix nitrogen deficiency; however, if you notice that the leaves are dropping rapidly with the yellowing spreading to the top, you'll have to act fast. For example, if you see the problem occurring during the vegetative phase, you'll need to be quick since the plant needs more nitrogen at that point. Also, you'll have more time to fix this issue if you're growing photoperiod plants. For autoflowers, however, you'll need to be super quick since they follow an internal clock and start flowering within 4-6 weeks after germination. This means that you may have a small window with most autoflowers. 

In short, chlorophyll — the green pigment — contains nitrogen. Therefore, the cannabis plant needs nitrogen to remain green and healthy — a lack of nitrogen forces the plant to become chlorotic or yellow. Once the chlorophyll reduces, the yellow pigments become more distinct, showing a deficiency. So, if the plant has enough nitrogen in the soil or other media, it will remain healthy. If not, it turns yellow and will eventually die when uncontrolled. The lower leaves transporting the nitrogen to the new leaves will undergo chlorosis, whereas the younger ones will look green. 

Possibilities of Other Deficiencies

As mentioned above, you can confuse nitrogen deficiencies with other issues such as:

Iron deficiency

Iron deficiency

Like nitrogen, iron is also an essential element for the plant's growth. Now, as you already know, nitrogen deficiencies show up at the bottom and then travel to the older leaves. 

Iron, like nitrogen, is also involved in chlorophyll synthesis. And, just like the plant stops development without nitrogen, it will do the same with an iron deficiency. Therefore, iron deficiency will also display yellow leaves because the plant cannot produce chlorophyll. 

However, the main difference is that while nitrogen deficiencies start at the bottom, iron deficiencies will affect the younger leaves. Thus, new shoots will appear yellow. In addition, iron spreads very slowly, so you have time to fix it, but the shoots will stop growing and eventually become white if uncontrolled. 

Light burn

light burn

Although cannabis plants need adequate light for photosynthesis, too much light can stress them out. Abd the symptoms can be very similar to a nitrogen deficiency where the plants become yellow with brown patches. 

However, as you know already, nitrogen deficiency affects the bottom and then travels to the top. On the other hand, light burn causes the younger leaves to turn yellow. In addition, leaves become weak and fall off easily when the plant suffers from a nutrient deficiency, but they do not do that when affected by light burn. They will look crispy and yellowish-brown, no doubt, but you will not be able to pluck them easily. 

So, if you notice that the tops are turning yellow, it could be light burn or iron deficiency. The next step is to check the pH. If the pH is in the correct range, but the tops are still yellow and crisp, it could be light burn.

Sulfur deficiency

Sulfur deficiency

Like nitrogen, sulfur (or sulphur) also plays a significant role in synthesizing chlorophyll. In addition, sulfur is responsible for metabolizing nitrogen, so a nitrogen deficiency usually accompanies a sulfur deficiency. Thus, your plant can be suffering from both nitrogen and sulfur. 

And since both deficiencies are similar, it's slightly tricky to identify the exact cause. Like nitrogen, a sulfur deficiency will also cause yellowing. However, the younger leaves will be affected first in most cases. A sulfur deficiency is rare, and the symptoms show up late, so it may be challenging to spot them. Apart from yellowing, the leaf's undersides may turn red or orange. The leaf's veins will begin to turn yellow at first, and you may also notice the stems turning purple. 

If you're unable to diagnose the exact cause, you will have to flush the medium with pH-balanced water and feed the plants with your regular nutrients again to fix the issue. 

Causes of Nitrogen Deficiency

Nitrogen deficiency

Nitrogen deficiency is common in cannabis, especially for new growers. It is caused due to several reasons, such as the following:

  • Low nitrogen amounts in the nutrient solution or soil
  • Improper pH levels in the medium or solution
  • Damaged or unhealthy root systems that inhibit nitrogen absorption
  • Excess chloride, zinc, potassium, or manganese in the nutrient solution or grow medium, which inhibits nitrogen consumption

These issues are common for novice growers, but tackling them is easy. Read on to find out.

Solutions to Nitrogen Deficiency

Fortunately, nitrogen deficiency is easy to fix. All you have to do is feed your plant the right amount of nitrogen, and it will recover within a week. Below are a few ways to give your plant adequate nitrogen.

Check the pH

Before feeding the plant with nitrogen-rich ferts, check whether the pH is appropriate. The plant can sometimes exhibit symptoms of a nitrogen deficiency if the pH in the root zone is very low. Due to this imbalance, the plant will not absorb adequate nitrogen, or most nutrients, even if they are present in the soil. 

If you're growing in soil, the plant will do well if the pH ranges between 6 to 7. On the other hand, if you're using hydroponic mediums, the pH can range from 5.5 to 6.5. 

You could mistake a pH imbalance for a nutrient deficiency and try to fix it, which is common among new growers. However, you may worsen the problem if you don't check the pH first. 

Flush the soil or growing medium with enough water if you notice a pH imbalance. Then, let the plant rest a bit and feed it with your regular nutrient solution so the plant can recover. 

If the pH is not the issue, you can try other methods described below. 

Using Growth Fertilizer

The best way to fix nitrogen deficiency in plants is to feed them with growth fertilizers containing adequate nitrogen levels. You can buy these fertilizers in almost every gardening store, and they are pretty cheap, too.

Use water-soluble fertilizers as they are easy to use and act quickly. In addition, they reach the root directly so your plant can absorb them immediately, speeding up the recovery.

If in doubt, go for a regular grow booster. For example, if the manufacturer sells nutrients as Part A and Part B, use the part that's supposed to be used in the vegetative stage. The NPK numbers will display the amount of nitrogen the fertilizer contains. Thus, if the numbers are 3-2-1, it has more nitrogen. 

That said, be cautious before using random fertilizers to provide any nutrient because it can cause an imbalance and even a nutrient lockout at times. It's best to prevent the issue rather than treat it, so go for a brand that contains appropriate nutrients in the first place. 

If you've used organic products to grow your cannabis, you may be looking for organic nitrogen sources. In such cases, use either blood meal or worm castings to provide nitrogen. Let's take a look at them.

Worm Castings

Worm castings are organic — it is essentially earthworm poop, rich in soil minerals, including nitrogen. Not surprising considering how earthworms spend their lives in the soil. It is the most reliable organic fertilizer for beginners, too.

To give your plant worm casting, you can make worm tea. Here's how to do that:

  1. Fill a few containers (bottles or buckets) with water.
  2. Leave the containers open for at least a day so the chlorine and other impurities clear off. 
  3. Then, take an old but clean sock and fill it with worm casting. Mix about 3 to 4 tablespoons of worm casting for each liter of water.
  4. Place the sock in the water container for a few days.
  5. Once the water has turned dark brown, it is ready.

Then, feed this water (or tea!) once to give your plant a boost. Following this, ensure you use the correct nutrient solution (with enough nitrogen) to avoid deficiency in the future. 

Also, avoid storing the tea for too long as it goes bad quickly.

You can also use worm casting as a top dressing on the soil. Mulch the soil with half to one inch of worm casting, followed by watering the plant. Do this once a month to ensure adequate nitrogen in the root zone.

Blood Meal

Another organic fertilizer rich in nitrogen is blood meal, aka animal blood. This fertilizer has been growers' go-to choice for centuries, and rightly so.

You can purchase blood meal in the form of dry powder, and they have naturally high nitrogen levels, which it releases quickly into the root zone.

Even here, you can add blood meal in a water solution or directly to the soil. 

Here's how you can make blood meal tea:

  1. Fill a water bottle or container with water to blood meal ratio of 9:1.
  2. Mix the solution well and let it stand for some hours.
  3. Then, keep mixing it every couple of hours and open the lid for some time to let the gas out.
  4. Let the solution mix properly for two days until no solid chunks are left in the container.
  5. Then, mix this with regular water in a 1:9 ratio.

The tea is ready. Feed it to your plant once a week until your plant has recovered fully.

On the other hand, you can even mix the blood meal directly into the soil. You only need to add a little — about one cup for every 20 sq. ft. — on the upper layer of the soil. You only need to add a little because it tends to stay in the soil for too long.

However, blood meal does have some drawbacks. First, it can turn your soil or grow medium too acidic, which is bad for the roots and the plant. So, we recommend keeping an eye on the pH levels every day and adjusting accordingly.

Plus, it has a lot of nitrogen, so you must use it carefully, per the manufacturer's instructions. Too much nitrogen, or nitrogen burn, can be bad for your plant — it can delay the flowering process or even kill the plant entirely. In addition, it can cause nitrogen toxicity that makes the leaves appear like claws. As a result, they will look extraordinarily green but in an unhealthy way. If this happens, flush the plant to remove the excess nitrogen. 

Other similar organic fertilizers are cottonseed meal and bat guano. Regardless of which fertilizer you use, always ensure that you use the correct quantity as recommended by the manufacturer.

You can even talk to other growers growing the same strain as you to know how your plant would react to the fertilizers.

Summary: What is Nitrogen Deficiency and How to Fix It?

Nitrogen deficiency is easy to fix, and by using the solutions mentioned above, you can heal your plant in a short while because your plant absorbs nitrogen quickly. If you do everything correctly, your plant may start growing normally within just a week. 

The leaves may recover and turn green again for some plants, but the leaves may not recover at all for others. However, this is normal. The plant will grow new leaves again — no need to worry. Give your plant enough nutrients and take good care of it, and this won't affect the yield.

Always check whether your plant is actually suffering from a nitrogen deficiency or something else. Generally, an imbalance of pH can mimic other issues and confuse you. If the pH at the root zone tends to be low, the plant can develop some issues. Therefore, always check the pH before attempting to treat deficiencies. 

Your plants may be suffering from a nitrogen deficiency if the lower leaves turn yellow or pale at the beginning. It will then spread to the top of the plant. The plant can also appear lime-green. Eventually, the yellowed leaves may develop dark patches with the leaves softening. They may also appear crispy if it has a severe deficiency. 

Nitrogen is an important element that aids in photosynthesis. Once the younger leaves sense a lack of nitrogen, the older leaves transport their nitrogen to them, leaving them with a deficiency. Since the plant will prioritize its younger leaves, the older leaves will fall off due to a lack of nitrogen. 

If the symptoms occur when the plant is at the end of its life cycle, you won't have to do anything since it's normal. However, if the plant exhibits these symptoms during its vegetative or growing phase, you will have to fix the issue. 

You can fix nitrogen deficiencies using both organic and inorganic fertilizers. However, organic products, like manure, for instance, will take a long time compared to water-soluble nutrient solutions that fix the problem quickly. 

In addition, other deficiencies like iron and sulfur can make it look like the plant is suffering from a nitrogen deficiency. However, always look for the root of the problem. For instance, nitrogen starts at the bottom and travels to the top whereas iron and sulfur deficiencies affect the new shoots first. 


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A good read. Had this problem 2 years ago. Worm casting was a life saver
Un artículo indispensable para cualquier cultivador. Muy útil😎
nice article, bravo :D
Nice info 👍🏼. Thanks