Nitrogen deficiency in cannabis plants

How To Spot & Correct Nitrogen Deficiency in Cannabis Plants


Are your leaves looking a little yellow? Have you been really successful planting cannabis at home, but lately your plants seem to be struggling?

Then nitrogen deficiency in cannabis plants may be causing you all this trouble. Whether you’re an experienced grower or a rookie home gardener, diagnosing the lack of a macronutrient, such as nitrogen, phosphorus, or potassium is never an easy task, but solving this issue is necessary for the well-being of your girls. So, what causes this issue and how can you add nitrogen to soil?

Nitrogen deficiency in cannabis plants
Yellowing leafs can be a sign of nitrogen deficiency

(N) Nitrogen: Necessary for the formation of amino acids, coenzymes and chlorophyll.

Macronutrient: Absorbed in large quantities from the growing media or the nutrient solution. Macronutrients are the best-known and recognized constituents of plant food and their potency is identified as N-P-K ratings, printed on all commercially available plant food containers.

What makes nitrogen for cannabis so important, anyway?

Some interesting facts about nitrogen are necessary to truly understand why this macronutrient is such a key resource in your cannabis grow.

Anyone who enjoys growing should know about the importance of nitrogen in healthy soil, particularly since it’s a fairly abundant nutrient found in both plants and animals. In fact, it one of the components of nucleic acid that forms DNA, which means it’s basically one of the most fundamental ingredients that makes up the genetic identity of all plant life on the planet.

Nitrogen is also an essential element of amino acids in plant structures so it’s an important element in the production of proteins as well. In fact, the nitrogen found in plants affects the distribution of dry matter, within which, has a direct influence on root growth and leaf development. And if that wasn’t enough, all growers should know that cannabis relies on nitrogen in order to create chlorophyll, the pigment that turns plants so vibrantly green and shiny.

Thus far, nitrogen is pretty important for plants, right?

Most abundant elements on earth

Once the the “clone” stage is done and the root system can support further growth, the “vegetative” stage begins.

Because growth during this period is primarily focused on the stems, branches and foliage, plants need large amounts of nitrogen for is the production of chlorophyll. The most substantial growth over the lifecycle of the plant occurs in the vegetative stage, and will continue unless interrupted by a change in the environment or lack of water and nutrients.

The bigger the plant the more nitrogen it needs

So, let’s see what happens when we take things one step further. A key fact about nitrogen is that plants demand more and more of this macronutrient as they grow. The bigger a plant gets, the more nitrogen it needs in order to remain healthy.

This means that to meet the nutritional needs of your grow, you have to make sure that your cannabis plants have enough nitrogen to digest as they evolve. So, in short, nitrogen is a necessity.

So, what causes nitrogen deficiency in weed plants?

Cannabis nitrogen deficiency is the direct result of unhealthy soil. Plain and simple.

1. Too much organic matter

If you add organic matter with high levels of carbon to your soil, then a lot of the nitrogen in your soil will be used by soil organisms to break down that carbon. This means less nutritious nitrogen-based food for your plants.

The same thing happens when there is too much sand in the soil, the organic matter is not sufficiently decomposed, or it rains a lot (for outdoor growers). There simply won’t be not enough bio-available nitrogen for your cannabis to keep growing.

2. Not enough biology

In other cases, there is not enough biology (living organisms) in the soil to transform nitrogen found in the atmosphere or inorganic materials into forms that the cannabis plant can digest.

The lesson here is to be super careful about what you do to your soil. If you treat your soil poorly, it’ll be your plants that suffer the consequences.

3. Waterlogging

Waterlogging is another main cause of nitrogen deficiency in plants. When there’s too much water in your soil, the bacteria living in that soil will begin to turn nitrate (the plant-available form of nitrogen) into nitrogen gas, which is then lost into the atmosphere.

Similarly, if you use chlorinated water on your grow, you run the risk of turning nitrate into nitrogen gas and of depriving your plants of the quantities of nitrogen that they need and deserve. In fact, chloride in high concentrations can be toxic to your plants, which is another reason to avoid this kind of soil maltreatment at all costs.

4. Other elements interfering

Other elements in your soil, such as potassium, zinc, and manganese, can also affect the levels of nitrogen available. Sudden growth spurts can also put additional stress on the plant and result in nitrogen deficiency.

In short, there are a number of reasons why nitrogen may be lacking in your grow. The important thing is to be able to measure nitrogen levels and then take the necessary steps forward in order to rectify the problem.

Nitrogen deficiency in cannabis plants (1)

How can I tell if my soil is lacking nitrogen?

Luckily, nitrogen deficiency symptoms in weed plants is pretty easy to spot, so any dedicated cannabis grower should be able to tell whether his or her plants need more nitrogen fairly quickly.

As chlorophyll disappears, leaves cup upwards and they lose their vibrant color. They begin to look pale and yellow starting at the bottom of the plant and gradually moving upwards.

Another clear sign is that nitrogen-lacking cannabis plants simply stop growing. Flowers, branches, and leaves are reduced and they lay dormant. Some of the worst cases of nitrogen deficiency in plants can be identified in the development of tiny purple spots on leaves, stems, and branches.

The leaves in the lower part of the cannabis plant may start to turn yellow and even begin to drop off. If the upper section of the plant also starts to turn pale, then you can be sure that it’s time for you to do something.

Addressing this issue is especially important during the vegging stage of the process, as it is at this moment when marijuana needs nitrogen the most. Some growers even say that plants suffering from nitrogen deficiency are, in effect, “starving”, leaving the plants more susceptible to complex issues, such as the attack of insects and the spread of diseases. 

So, if you’re interested in learning how to add nitrogen to your soil, then it’s a good idea to first test it with fertilizer test strips or similar products to make sure that you are making the right move. If it is not in fact nitrogen deficiency that is causing your poor cannabis plants to suffer, you want to avoid supplying it with too many supplements that could hurt her.

fertilizer test strips
Fertilizer test strips

Adding nitrogen to soil

In order to battle nitrogen deficiency effectively, it’s a good idea to turn your attention to the appropriate use of a nitrogen-rich fertilizer.

If you’re a newbie grower, then you should know that fertilizers are determined by their NPK ratio, meaning their nitrogen (N), phosphorus (P), and potassium (K) content. Nitrogen-deficient soils need a high nitrogen fertilizer, which means the product you buy should have a high first number. Those products that offer a slow-release form of nitrogen are also a good choice, as they prevent nitrogen-caused burning and prompt an even growth.

Can you have too much nitrogen in the soil?

Yes! Nitrogen deficiency happens when you plant is lacking nitrogen. nitrogen toxicity, on the other hand, is when there is too much nitrogen available for your plants.

Nitrogen toxicity results in overly vigorous growth, dark green leaves and delayed fruit ripening. Plants may also become more susceptible to pests.

Be proactive with a microbial inoculant

Nitrogen is available all around us. We just need to learn how to harness its powers and help cannabis plants take as much of it as they need. As we learned, the secret to this is having healthy soil that benefits the plant.

One way to achieve this is to increase soil diversity through microbes, as they help the plant improve their nutrient uptake.

What is a microbe, you ask?

Just like us humans need microbes in our guts in order to breakdown food, fight off decease and live healthy lives, plants need microorganisms in the soil to help transform nitrogen into something they can digest. Microorganisms help plants by improving their uptake of macronutrients and even out chemical imbalances in the soil.

Try our shelf-stable ferment of full-spectrum microbes called Amplify. Combine it with a high nitrogen fertilizer to grow big, healthy cannabis plants that don’t turn yellow while you’re not looking. More about what soil microbes do for cannabis plants can be found here.

Amplify bottles

Learn how to spot and fix cannabis nutrient deficiencies

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