Nitrogen: A Plant’s Go-To Element

By Rich Hamilton
Published: March 22, 2022 | Last updated: March 22, 2022 05:25:56
Key Takeaways

If there’s one thing healthy plants need, it’s nitrogen. No element supports more plant processes than this macronutrient. But be careful, as too much of a good thing can be very harmful.

Plants, like animals, need some important nutrient elements to keep them healthy. The growth and development of a plant’s leaves, roots, and fruits depends on the availability of essential nutrients like nitrogen. These elements support and enhance the plant's biological processes including growth, absorption, transportation, and excretion.


These nutrient elements are broken down into several groups based upon the quantity in which the plants need them: macronutrients, secondary macronutrients, and micronutrients. The macronutrients are nitrogen (N), phosphorus (P), and potassium (K), otherwise known as NPK.

When you look at a bottle of plant nutrients designed for indoor growing, you will normally see three numbers on every bottle, this is known as the N-P-K ratio. This ratio tells you how much of each macronutrient is contained within the bottle. A bottle that says 1-2-3, for example, would indicate that it contains that particular percentage mix of each of the macronutrients. Plants require macronutrients throughout their whole lifecycle, albeit in different quantities, and so you will find NPK ratios vary depending on what nutrients you are buying and what phase the plant is in.


The Many Roles of Nitrogen

Nitrogen is commonly viewed as the most essential of all the macronutrients and as such, is required by the plant in the largest amounts. This is because nitrogen supports many processes that occur inside the plant throughout all stages of its lifecycle. It is a fundamental component of many plant structures and their internal and external metabolic processes.

So, why is nitrogen so important? Let’s break it all down and have a look at the role of this essential element, starting with what nitrogen actually is.

Nitrogen in its most natural and purest form exists as a colorless, odorless gas. It is one of the building blocks of life that is essential for all plants and animals to survive. Nitrogen is needed for growth, reproduction, and for creating amino acids that make up proteins. It is also found in cells where it is contained within nucleic acids that hold the information for creating new life.


Nitrogen can also be chemically reacted with other compounds such as ammonia, nitric acid, organic nitrates, and cyanides to form unique compounds with totally different chemical and physical properties.

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Since plants cannot use nitrogen in its gaseous form, uptake occurs via water-based nitrogen forms such as ammonium and nitrates that can be easily absorbed by the roots. This process is achievable in the natural environment thanks to the “nitrogen cycle” that sees nitrogen in the atmosphere converted into a soluble form that is available for uptake by the plant.

The nitrogen cycle is the process where natural nitrogen gas is converted into soluble nitrates which are then taken up by plants and used to make proteins. Animals eat plants for nutrition and so nitrogen from the plant's proteins becomes proteins in the animal. The ongoing decomposition of faeces, urine, and bodies of animals then results in nitrogen being returned to the soil as ammonium ions, which nitrifying bacteria then converts into nitrates for plants to absorb. Finally, in the cycle, denitrifying bacteria in the soil break down nitrates and return nitrogen gas to the atmosphere.

When it comes to growing indoors, however, we can’t rely on the nitrogen cycle and instead plant-soluble nitrogen can only be made through chemical nitrogen fixation, such as from nitrogen fertilizers. Nitrate nitrogen is the most common form for plant fertilizers as it is easily taken up by the plant and has good soil retention, unlike ammonium nitrogen, which requires more oxygen for it to be metabolized in plant roots.

So, now we know what nitrogen is and how it is taken up, let’s have a look at the many roles that it plays in the health and development of your plants.

Nitrogen: An Essential Element

Nitrogen is an essential element of all the amino acids in plant structures, which are the building blocks of plant proteins.

Proteins are vital for every conceivable process in the plant to take place. Proteins stimulate growth, promote fruit development, and assist with the growth and development of vital plant tissues and cells. Nitrogen is a component of nucleic acid that forms DNA and helps transfer certain crop traits and characteristics that aid in plant survival. It also helps hold the genetic code in a plant’s nucleus.

Nitrogen is an important ingredient in chlorophyll, the green chemical required for photosynthesis and likewise is fundamental to the process of photosynthesis as a whole. Plants with sufficient nitrogen will experience higher rates of photosynthesis and have bigger, faster, and stronger plant growth and development.

Nitrogen also maintains and optimizes root system performance. When roots have enough nitrogen, they perform to their fullest potential, absorbing more water, more nutrients, and grow faster.

nitrogen deficiencyAn example of nitrogen deficiency.

Nitrogen Deficiency in Indoor Environments

There are several reasons why your plants may suffer with a nitrogen deficiency when growing in an indoor environment. It could be simply that you’re underfeeding them and there is not enough nitrogen available, or that whatever nitrogen there is has leached out of the medium due to its soluble nature. Overfeeding of other nutrients could also be your problem as it could see the pH of your medium rising too high, which in turn can prevent your plant’s roots from being able to adequately take up what they need. Potassium, zinc, manganese, and chloride specifically, can all block nitrogen from being taken up if they are present in the medium in too high a concentration. Even if your feeding regime is spot on, you could still suffer with a nitrogen deficiency if the root system of the plant is dysfunctional, which can be caused by damage, disease, or a low temperature in your growing medium.

A nitrogen deficiency can be typically identified by pale green or yellowing leaves, usually starting with the lower leaves as they are lacking the nitrogen to make chlorophyll. Poor growth of the plant and fruits, which is caused by a reduction in proteins is another symptom, as plants suffering with a nitrogen deficiency will be smaller than average and so will their fruits. Plants with a nitrogen deficiency are also more susceptible to disease and pest infestation.

Growing in a hydroponic system or coco can reduce the possibility of a nitrogen deficiency. If you do still experience one, however, then the best course of action is to slowly increase your nutrient feed in strength by one milliliter at a time and monitor your plants until you reach a level that sees the leaves turn a rich green again. You can use an additional nitrogen booster or alternatively, a foliar feed that will absorb the nitrogen directly through the leaf, correcting the problem more quickly. Do not feed via the roots and use a foliar spray, however, as you could end up with the opposite problem — too much nitrogen (nitrogen toxicity), that is equally, if not worse than, a deficiency.

nitrogen excessAn example of nitrogen excess.

Signs of Nitrogen Toxicity

Symptoms of nitrogen toxicity include dark green leaves, curling leaf tips, clawing or turning down randomly around the plant, yellowing of leaves, slow growth and nutrient burn, which can be identified by the very tips of each leaf yellowing and then turning brown.

Plants need more or less nitrogen throughout their lifecycle with many needing more in veg than in flower. This is why you should always use the specific nutrient feed required, for the specific plant you are growing, at the right stages of the lifecycle, whether that is propagation, veg, or flower.

To treat nitrogen toxicity, you should monitor your pH and EC levels and decrease your feed ratios by 1ml at a time until any new signs of toxicity have ceased. Leaves that have badly clawed or yellowed/browned will probably die and fall off, but if tackled in time, the rest of your plant should survive. Flushing your plants with clean fresh water is another great solution; this is because nitrogen can be very soluble and easily leached out of your medium and away from your plant’s roots. Take your pH/EC readings regularly until the levels have come back within ideal range and your plants look like they are on the road to recovery.

Your plants need a mix of all macro and micronutrients to grow and develop to their full potential and problems can occur if any of those nutrients are missing from the mix, no matter how small.

Nitrogen, however, is the most abundant element in our atmosphere and is needed in such large quantities (10-60 grams per kilogram of plant mass, to be exact) and assists with plant health in so many ways that it is rightly considered to be the most important component for supporting plant growth.

Nitrogen is a crucially fundamental component for all life, including humans. It is an important part of many cells and processes such as amino acids, proteins, and even our DNA, with neither plant nor animal being able to survive or exist without it.

Nitrogen therefore warrants careful application and monitoring when it comes to your plants. When mismanaged, it can lead to severe environmental problems and sometimes, total crop failure.

If you can manage and monitor your nitrogen levels efficiently, it should have a knock-on effect in how you manage the rest of your plant’s nutrition, which will inevitably lead you to getting the biggest and best results possible.


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Written by Rich Hamilton | Writer, Consultant, Author of The Growers Guide

Profile Picture of Rich Hamilton

Rich Hamilton has been in the hydroponics industry for more than 20 years, working originally as a general manager in a hydroponics retail outlet before becoming an account manager at Century Growsystems. He enjoys working on a daily basis with shop owners, manufacturers, distributors, and end users to develop premium products.

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