Bountiful crop yields start with rich and fertile soils, but we can’t just leave it all up to nature. We must regularly replenish any missing nutrients since farming gradually depletes land fertility.

If you are interested in crop nutrition, you probably already know that nitrogen (N) is one of the three fundamental macronutrients for plant health. Alongside phosphate and potassium, plants need nitrogen for photosynthesis, cell division, and protein synthesis, among other functions.

So, if you are asking yourself “What is a nitrogen fertilizer, and do my crops need it?” this guide is for you. Let’s go!

nitrogen molecule

What Is Nitrogen Fertilizer?

Nitrogen fertilizers are one of the most widespread products used in agriculture worldwide as an essential nitrogen source for plant growth. Some common types of nitrogen fertilizers include urea (CH4N2O), ammonia (NH3), ammonium (NH4), sodium nitrate (NaNO3), and sodium chloride (NaCl).

When choosing between fertilizers with nitrogen, you have to decide whether to go organic or synthetic. The latter option was the only one farmers had until very recent history.

For ages, humanity farmed according to nature’s rhythms, mainly using manure and compost to increase their harvest yields. Despite being healthy for our planet, these are not very efficient fertilizers. Over time, nitrogen changes into different chemical forms that plants and animals can use. That is why farming used to be much less efficient before fertilizers helped speed up the process. It takes a while for organic matter to decompose and for the nitrogen cycle to replenish itself.

The mass production of synthetic nitrogen fertilizers for plants didn’t start until the dawn of the 20th century. It was German scientist Fritz Haber who made a groundbreaking discovery that changed history forever. He came up with a method of synthesizing ammonia from hydrogen and nitrogen gas, an invention for which he was awarded the Nobel Prize in chemistry.

Since then, the Haber–Poch process has been known as one of the biggest breakthroughs in large-scale fertilizer manufacturing. Now, thanks to Haber’s invention, it is estimated that nearly half of Earth’s population eats food produced with the help of nitrogen fertilizers.

Types of Chemical Nitrogen Fertilizers for Crops

We already mentioned that nitrogen-based fertilizers typically come in one of four forms. These are classified as single nutrient or “straight” fertilizers because they provide only one macronutrient, but some can be combined with other elements to create a compound product. Most farmers prefer using NPK fertilizers as they are a more holistic nutrient management solution.

Each form has its own unique properties that determine the best time, place, and method of application. Let’s take a look at them separately so that you can better understand what makes them different from each other.

Ammonia (NH3) and Ammonium (NH4)

We kick off our list of nitrogen fertilizer examples with ammonia and ammonium, as it’s easier to explain them alongside each other.

Ammonia is a gas that’s produced using the Haber–Poch process. It is the foundation of all mass-produced nitrogen-based fertilizers. It has plenty of industrial applications, too, and you may recognize it by its distinct pungent smell.

These fertilizers work best in soil pH that is not too acidic or alkaline. Just be careful not to overuse them, as they can be volatile and may lower the soil’s pH over time, making it more acidic.

There are plenty of product variations in this group, so we’ll give you a brief overview of some of the more prominent ones:

  • Anhydrous ammonia is packed with 82% nitrogen, making it one of the strongest fertilizers out there. It’s mostly used after harvest to prepare the field for the next season. If you’ve ever seen a pill-shaped white tank being towed near a field, it most likely contains anhydrous ammonia. This fertilizer is applied as a pressurized liquid, which reacts and turns into ammonium in the soil. Anhydrous ammonia, however, is dangerous and requires professional handling with protective equipment and following strict safety measures.
  • Adding water to anhydrous ammonia results in aqua ammonia. Yes, dissolving reduces the nitrogen content but makes the product much safer to handle. Aqueous ammonia has a 20–25% N content and is usually used in irrigation.
  • Ammonium-containing fertilizers release ammonium ions (NH4+) in the soil, which plants can directly absorb or convert into nitrate through the so-called nitrification process. It’s best to choose one of these products if you’re dealing with slightly acidic to neutral soils. Ammonium sulfate (NH42SO4), for instance, is perfect as a fall plow-down and spring pre-plant treatment. Ammonium chloride (NH4Cl) is another alternative that has about 24–26% N content.

Urea (CH4N2O)

Urea is a diamide of carbonic acid that is used to manufacture plastics, pharmaceuticals, animal feed supplements, and, of course, fertilizers. Despite its diverse applications, over 90% of the manufactured urea goes to the agriculture sector. In fact, the demand for this product is so high, that statistics show that it’s the most widely used nitrogen-rich fertilizer globally.

Urea was actually the first organic compound that humans managed to synthesize using inorganic matter. It’s considered a neutral and quick-acting fertilizer. Many growers use it to encourage green leafy foliage and would typically apply it during the sowing, flowering, or fruit stages.

Main characteristics:

  • Urea has the highest N content (46%) out of all solid nitrogen fertilizers. This is why you might see it being referred to as 46-0-0.
  • Its high concentration makes it one of the most cost-effective nitrogen sources for farmers.
  • Thanks to its neutral pH, it’s suitable for almost all soil types.
  • Plants cannot directly absorb this kind of fertilizer; it needs to break down first. Once applied to soil, it rapidly transforms into ammonium bicarbonate within 48 hours.
  • Handle this fertilizer type with care. Otherwise, improper management can lead to significant losses in the form of ammonia gas.

Ammonium nitrate (AN)

Ammonium nitrate is a chemical compound composed of ammonium ions (NH4+) and nitrate ions (NO3-). It comes with an NPK rating of 34-0-0, which is impressive, although it’s not as concentrated as urea. But it does have an advantage—AN is more stable, and thus it doesn’t leach into the atmosphere as quickly.

However, the demand for ammonium nitrate has fluctuated a bit over the past few years. By 2022, global AN production had dropped to 47.9 metric tonnes in comparison to its peak of 49.36 metric tonnes in 2020. This is a notable decline, but there’s a reasonable explanation for it.

Besides the fact that it’s not the best nitrogen fertilizer out there, there have been numerous tragic accidents involving the misuse of this chemical combination. Several countries are phasing out ammonium nitrate in consumer applications because they’re worried about it being mishandled. 

Until the demand completely subsides though, there’s still a place for this source of nitrogen in fertilizers. AN is particularly effective in increasing yields in crops such as blueberries, maize, and tea plants. You’ll see it most often in the form of crystalline powder or white beads that can be applied in neutral to slightly alkaline soils.

It’s also worth mentioning one of its most popular variations, calcium ammonium nitrate (CAN). This is a compound granular fertilizer that packs a punch with 25% to 28% N content. European farmers, in particular, use it extensively since it works well with the old continent’s acidic soils and chilly climate. There’s another perk, too: CAN fertilizer has one of the lowest carbon footprints compared to other products with a similar nutrient profile.

Organic Nitrogen Fertilizers

Now let’s briefly go over some of the most potent organic high-nitrogen sources for plants. We have to clarify that by “organic” we simply mean a fertilizer that contains the element of carbon, not necessarily a certified product. We’ll focus on N fertilizers that you can essentially DIY at home if you have the right supplies.

  • Blood meal takes the crown as the most bio-accessible source of nitrogen for plants. It comes in powdered form and it’s made of dried animal blood. On average, it has about 12% to 13% N content and comes at a relatively low cost, too. Watch out though, because using blood meal on your fields might attract carnivores who can smell its scent.
  • Feather meal contains up to 14% nitrogen, the highest amount of any organic fertilizer. Hydrolyzed feathers are an excellent source of slow-release nitrogen. The only downside to mention is that feather meal is not very soluble in water.
  • Opt for fish emulsion if you’re looking for a compound plant feed. Alongside nearly 5% nitrogen, this liquid fertilizer also contains phosphorus, potassium, and several helpful micronutrients. As a potential drawback, it has a strong fishy smell, but many products on the market are deodorized.
  • While not as high in nitrogen as the above examples, seaweed fertilizers provide a broad spectrum of essential nutrients for plants. Algae are also known to improve stress resistance and enhance the presence of beneficial soil microorganisms.

 

hand holding fertilizer close to soil and growing seedlings

Pros and Cons of Nitrogen Fertilizers

The effects of nitrogen on plants are well-known and researched. In the past few decades, however, manufacturers have focused less on the quantity of food we produce and more on how we can continue at this pace sustainably.

The excessive use of nitrogen fertilizers in agriculture is a huge subject of debate. Let’s take a look at both the advantages and disadvantages so that you can get a clearer picture:

Pros:

  • Nitrogen is arguably the most important nutrient that plants need. It’s necessary for the formation of amino acids, proteins, chlorophyll, and nucleic acids.
  • Synthetic nitrogen fertilizers are responsible for almost half of the food we eat worldwide.
  • A well-balanced liquid nitrogen fertilizer applied as a foliar spray can help plants develop a healthy, lush leaf mass.
  • Applying small doses of it several times during the growth cycle can shorten the time it takes for crops to reach maturity. This allows for earlier harvests and potentially a second planting during the same season.
  • It can drastically increase the quantity and quality of yields, depending on the type of crop and the condition of the soil. This means we don’t have to tear down forests and grasslands to make room for more farmland.

Cons:

  • Nitrogen makes up the majority of Earth’s atmosphere. However, it cannot be directly taken up by plants in gaseous form. It’s also not a resource that replenishes itself, so we have to use it sparingly.
  • Even if you are trying to cure a deficiency, be careful not to go overboard with nitrogen. Too much of it can lead to excessive vegetative growth at the expense of fruit and grain production.
  • Many agriculturalists and manufacturers are concerned with controlling nitrate pollution. The Haber–Poch process uses too much fossil fuels and produces greenhouse gas emissions. We can expect to see even more stringent regulations that address the environmental impact of these production methods.
  • The development of low-carbon footprint synthetic fertilizers is still in its infancy. Very few companies are actively working on renewable ammonia, and certainly not at the rates that can replace the energy-intensive manufacturing process anytime soon.

Signs of Nitrogen Deficiency in Plants

It’s not that difficult to tell when plants suffer from nitrogen deficiency. There’s no way to tell if your soil is deficient without testing it, but you’ll be able to tell if your crops are underperforming. You’ll notice several physical changes, specifically in the shape and color of the stems and leaves.

However, the signs of deficiency vary depending on the current growth stage of your plants. Here’s what you need to look out for:

  • You may notice stunted growth and rapidly spreading roots early on in a plant’s lifecycle. This forage response is not uncommon, as the plant attempts to scour the soil for more nitrogen. This, however, results in weak and thin stems that fail to produce shoots.
  • During the flowering stage, deficient plants tend to have small blooms. Stems are frail and fragile, prone to breakage and lodging. Pale and yellowing foliage (chlorosis) is another indicator. This points to a lack of chlorophyll, which is what gives leaves their lively green color.
  • Nitrogen deficiency during the fruiting period shows in the color, size, and setting rate of plants. All of these might be delayed because nitrogen is needed for proper reproductive growth. At this point, you might also start to see some premature shedding, as the plant struggles to maintain its older foliage.

We have to note that some signs, for instance, yellowing, can be indicative of other nutrient deficiencies. There’s also a chance that your crops may be having the opposite problem—N toxicity. Both issues have similar effects, but excess nitrogen usually produces darker foliage, stiff stems, and weak roots, so it’s a good idea to watch out for those.

How to Apply Nitrogen Fertilizer

Now that you know all the common signs of N deficiency, let’s see what you can do to combat these issues.

If you’re not sure what is causing your crops to underperform, we advise you to perform a soil test. Take soil samples at different depths, depending on how deep the roots go. You need to subtract the measured nitrogen amount based on the test from the nutrient demand of the specific plant.

Keep in mind that nitrogen fertilizer application rates depend on many other factors, too: the crop’s growth stage, soil quality, climate and weather conditions, and so on. A well-timed high-performance fertilizer will support your plants with the right nutrients when they need them the most.

As a general rule of thumb, it’s best to use a nitrogen treatment at times of intense growth. For example, in flower bud differentiation the development of new shoots slows down and the nitrogen in leaves decreases. This is the perfect time for a quick spray with diluted urea.

Always aim to place the fertilizer close to the root zone or in areas where rain can carry it there. Deep application is especially important in fields prone to erosion. Otherwise, nitrogen is prone to sticking to the topsoil. Cultivation techniques matter, too. The more you can minimize tillage and surface drainage, the less you’ll have to worry about nitrogen losses or soil structure damage.

Choosing the most effective nitrogen fertilizer requires the right know-how. That’s where Vaki Chim comes in—we are a leading European manufacturer with over two decades of industry experience.

Our Grow Plant line of premium fertilizers is formulated to help your crops reach their fullest potential. Find a local distributor near you and join our mission to create more sustainable food supply chains!

Conclusion

It’s safe to say that nitrogen fertilizer consumption and crop yields are directly correlated. The surplus of food we are used to is recent history and we have fertilizers to thank for it. But while nitrogen is arguably the most important nutrient that plants need, the environment pays the price for our excessive farming practices. Until the fertilizer industry finds a viable alternative to the above-mentioned forms of nitrogen, the food on our plates will come with a hidden cost.

FAQ

What fertilizer is high in nitrogen?

Urea contains 46% N on a weight basis, making it the most nitrogen-rich dry fertilizer. It’s one of the most popular fertilizers in the world because it’s strong, inexpensive, and easy to transport. Other than that, anhydrous ammonia is known to contain the most nitrogen per unit (82%). However, it has much greater safety risks and requires the use of more specialized equipment.

How to add nitrogen to soil?

The best technique is to mix the fertilizer in the soil itself. This way, the right amount of nitrogen becomes accessible to the plant roots and is less likely to leach. Nitrogen tends to get stuck in dry topsoils and crops are not able to make use of it.

When should I use nitrogen fertilizer?

Apply nitrogen right before or during the late vegetative and early reproductive stages. If you notice any issues with growing plants, you can start an early treatment to fix nitrogen deficiency symptoms. Try a controlled-release fertilizer to increase the soil nitrogen available to plants over an extended time period.

Which plants like nitrogen fertilizer?

Leafy greens, flowering plants, tomatoes, and corn usually have a big appetite for nitrogen and respond well to N fertilizer. Maize, wheat, and rice also benefit from a nitrogen boost during the early growth stages.

Sources:

https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/nitrogen-fertilizer

https://www.sciencedirect.com/science/article/abs/pii/S1750583615301079

https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/urea-fertilizer

https://www.statista.com/statistics/1287049/global-ammonium-nitrate-production/

https://insights.thyssenkrupp-uhde.com/story/ammonium-nitrate-fertilizer-and-why-it-is-the-preferred-choice-of-european-farmers/

https://minerva.jrc.ec.europa.eu/en/shorturl/minerva/ammonium_nitrate_fertilizer_production_and_storage

https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/nitrogen-deficiency

https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/ammonium-nitrate

https://carnegiescience.edu/green-fertilizers-could-revolutionize-agriculture-and-increase-food-security

https://www.sciencedirect.com/science/article/pii/S0304423821009626

Article by:

Krasimir Bozhurin

Krasimir Bozhurin is the Sales Director at Vaki-Chim LTD. With over a decade of experience in the trade of fertilizers, preparations, and seeds, he has developed extensive expertise in the cultivation of perennial fruit plantations and cereal crops.