Nitrogen Deficiency In Cannabis Plants

Nitrogen deficiency in cannabis is one of the most common problems growers face with marijuana. Nitrogen is an essential nutrient for plant growth and you must supply it from the start using a good soil.

It’s normal for your plant to drop some of its older leaves every so often. But if you are losing too many, especially if the plant is small, we have a problem.

Nitrogen Deficiency Colors And Symptoms

cannabis-nitrogen-deficiency-color-chartNitrogen deficiency begins with the loss of color in the tip of the leaf.

This loss of color will start moving inwards, leaving the leaf completely pale. The leaf will then start to brown and wrinkle, until it finally falls off the plant.

This symptom begins in the lowest and oldest leaves. If you don’t fix the problem quickly, it will “move up” through the plant to increasingly higher and newer leaves.

You should keep in mind that once you detect nitrogen deficiency, the plant’s ability to develop has already been affected. In turn, the plant becomes less resistant against pests, cold, and disease.

If you continue seeing these symptoms after applying the solutions I discuss below, then your plant is not lacking nitrogen, and you must find out what the true problem is as quickly as possible.

Leaf ColorSymptoms
They start with yellow spots between veinsWith the yellowing their growth slows down
They turn completely yellow and pale yellowThey start to wrinkle and the tips dry
They begin to fall day by day

Nitrogen Deficiency Pictures

Do these look like your plants? If not, compare with pictures of other cannabis leaf symptoms and how-to guides.

The Importance Of Nitrogen

Nitrogen is one an essential nutrient for cannabis, most important during vegetative stage.

If your plant shows advanced signs during vegetative stage—growth period—development will slow down and it won’t be able to grow to its full potential.

Since nitrogen is a major component of chlorophyll, by which plants use sunlight for their correct growth and development. It also plays a big part in proteins, allowing for cell development and biochemical reactions that make plants thrive.

Needless to say, if your plant is facing a nitrogen deficiency you have to do something about it as soon as possible, else your it will become weak and much more vulnerable to pest and disease.

During Flowering Stage

It’s completely normal for your plant to experience a mild nitrogen deficiency entering or during flowering.

flowering-cannabis-close-to-harvest

This is a good sign, since marijuana needs lower levels of nitrogen as it forms its buds, and too much of it could significantly detract from your harvest. Flowering fertilizers come with very low nitrogen levels for this very reason.

Although, it doesn’t have to be forced super low. A severe nitrogen deficiency can be detrimental at any stage, as nitrogen is linked to many vital functions.

Don’t Worry If You’re Close to Harvest!

Lots of leaves will begin discoloring on turn complete yellow when you’re close to harvest. Ideally your plants will begin to consume everything they’ve got in order to make those buds as powerful as possible. 

How To Fix Nitrogen Deficiency?

A nitrogen deficiency is one of the simplest deficiencies to fix. Below are a few ways — both simple and more complex — to fix a nitrogen deficiency. But first, I clarify some things.

If you have already been using fertilizers or if you are sure that your soil has sufficient nutrients, the problem is likely to be an unfavorable pH variation in your substrate or irrigation water. I have more information on this problem in the sections below.

If the leaves that are turning yellow are the newest or the tallest, or if the yellow patterns they show are different from the above photos, then it is a deficiency of another nutrient or a bigger problem.

Growth Fertilizer

Using a high nitrogen, water soluble growth fertilizer is the best way to resolve a nitrogen deficiency, as it goes directly to the roots. The roots absorb the fertilizer quickly, and in a few days the leaves will recover their original color.

These fertilizers can be bought in any nursery, and almost any plant food will contain nitrogen.

There are two types of these fertilizer, mineral and organic. Organic fertilizer improves the characteristics of the soil by providing nutrients, while mineral contains chemical elements that are absorbed faster and are cheaper and more precise.

Worm Castings

Worm castings are an organic fertilizer made up of earthworm droppings, which recycle organic material from the soil. Worm castings are the best option for beginners and the most reliable for everyone

Castings should be mandatory in every grower’s soil. They provide substances that promote cannabis growth, more than any other natural product.

If your soil doesn’t have worm castings, or not enough, the easiest way to feed your plants is making worm tea. If you want to see other ways check my guide on worm castings.

How To Make Worm Tea

worm-castings-teaYou’ll be steeping the castings in the water, like you would with a tea.

  1. Fill a bunch of containers with water, and leave those open for at least 24 hours, so it’ll get clean of chlorine and other substances.
  2. Find a porous fabric, like an old sock, an old t-shirt or a pillowcase you don’t need.  
  3. Now, for every liter of water add 3-4 tablespoons of worm castings inside the fabric, and close it by tying knots in it.
  4. Once again let it stand in an open container for 2 to 3 days.
  5. The water will turn into a dark brown tea when it’s ready.

You can now use this tea to water your plants and give them all the benefits that worm castings bring to the soil.

PS: If you strain it, you can also use it as a foliar application.

Blood Meal

blood-meal-nitrogen-fertilizerBlood meal is fertilizer full of organic nitrogen that comes from animal blood, and has been widely used for the cultivation of food for ages.

I recommend blood meal only for those who are used to fertilizing since it can turn the soil too acidic or create nutrient burn very easily.

Before adding blood meal, I would strongly encourage you to test your levels of pH, and to keep monitoring it after fertilizing. You don’t want your soil getting too acidic.

Check my guide on blood meal, specially if you’re growing outdoors, as there are precautions to have (like animals digging for it).

How To Apply Blood Meal

Mixing Blood Meal And Water

If you have your cannabis plants in pots, you would definitely want to add the blood meal via watering, as you don’t want to overdo it and the amount of soil in a pot in very limited.

  1. Fill a bottle to 10% of its capacity with blood meal.
  2. Fill the rest with standing water.
  3. Mix well and let stand for a while.
  4. Mix again from time to time and open the lid to let out the gases that are created.
  5. Wait a day or two until there are no solids in the bottle.
  6. Mix the contents of the bottle again with standing water, at the rate of 1 part of solution for every 10 parts of water. (10% and 90%)

With this new double-diluted solution you can now fertilize your plants.

Adding Blood Meal To The Soil

You can mix blood meal directly into the top inches of the soil, being really careful not to hurt any root while removing the soil.

The good thing about blood meal is that you only need to add a little. It will stay on the soil for a really long time, and your cannabis plants will keep benefiting from it.

As a rule of thumb the rate of blood meal you want to use is one cup for every twenty square feet of soil.

How Often To Add Blood Meal?

When mixed with water blood meal is quick to act, I would suggest watering with it  once a week as long as your plants need nitrogen. (If they’re green and healthy, nitrogen is going fine!)

In soil, it will slowly break down with time. And since blood meal is water soluble it can still can act fast to correct nitrogen deficiencies. Once applied, blood meal can feed your plants for 6-8 weeks after a single application.

Your Own Urine As Fertilizer

The main thing you should know is that urine must be mixed with carbon-rich materials for bacteria to work it’s magic.

The nitrogen in urine is in the form of urea, creatine, and ammonia. The aerobic bacteria convert it into nitrates so nitrogen will be available to your plant.

In soil there’s no problems, but in hydro setups there may not be enough bacteria culture to breakdown the urea and ammonia.

Using Urine In Soil

urine-fertilizer-high-nitrogenFor soil and containers with good drainage.

First, remember that irrigation water should always be left to stand on an open container. For at least 24 hours, to clean it of chlorine and other elements.

The safest ratio is 1 part of urine per 10 parts of water (1:10).

How To Make Watered Down Urine?
  1. Add pee in a plastic container.
  2. Now add 10 times more water. For example, if you put 1 liter of urine, you dilute in 10 liters of water. If 100 millilitres then 1 liter.
  3. Now remove a small layer of soil. Taking care not to damage the roots.
  4. Add the diluted urine as you would normally add water.
  5. Refill the layer of soil.
  6. Water once again with plain water. Just enough to get run off.

And that’s it. Although there’s few more things that you should know:

  • Removing the soil allows you to avoid bad odors and make better use of nitrogen, by achieving less ammonia generation.
  • The run off helps to prevent mineral build up in the roots.
  • For younger plants start with a ratio of 1:20 or 1:30 and work your way up.
  • Don’t fertilize seedlings.

Using Urine In Hydroponics

I wouldn’t recommend it for hydro. It will be less effective, and worse, it’s going to smell.

But if you really want you, this user form the forum Rollitup explains how it’s done:

“About 8 ounces (1cup) for every 3 gall or reservoir water has been effective. But make sure to adjust according to your conditions and plant needs.”

“So it will be a good idea to drip your res water through a porous material that can support a bacteria culture such as lava rocks, ceramic bio filter material, foam, sponge. It is up to you; it does not need to be fancy just able to support beneficial bacteria.”

How Often To Fertilize With Urine?

Once or twice a week, depending on how much you water your plants, should be enough.

Try reading your plants, check their colors, and even check how they stand. Is she big and proud? Or is she shy and droopy? If she looks great, then lay off a little.

Wrong pH

ph-meter-example

If your plants have enough nutrients after providing them with good soil and fertilizing them correctly, make sure you don’t end up with the wrong pH levels. If you applied the solutions listed above and your plant fails to recover after 7-10 days, you may have a pH problem.

In this case, nitrogen and other nutrients are present and available to your plant, but it cannot absorb it correctly. Nutrient burn is a common cause of pH problems.

Before continuing, you should check that both your soil and the irrigation water have a pH in the range of 5.8 to 6.8.

🕓 Watch For Recovery

After applying one of these solutions soon enough you’ll see healthier leaves getting their green color back.

Most affected leaves won’t recover from the nitrogen deficiency, they’ll just wilt and die, but that’s okay. New growth will come healthier than ever, and replace those old leaves.

Hopefully you have no pH problems and can easily solve the deficiency.

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Santiago Pardo
Santiago Pardo
I live to help out cannabis growers have a greater experience with their crop, and not lose their mind over the many aspects of growing marijuana.

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