What Does Ammonium Nitrate Do In Fertilizer

Ammonium nitrate is a common ingredient in fertilizers. It is a good source of nitrogen, which is essential for plant growth. 

Ammonium nitrate is a white crystalline solid that is highly soluble in water. It is hygroscopic, which means that it absorbs water from the air. This can cause the fertilizer to cake and become difficult to apply. 

handful of ammonium nitrate fertilizer

Because of hygroscopic, ammonium nitrate in fertilizer is often coated with a polymer that dissolves slowly when in contact with water. It not only stops the fertilizer from caking, but it also slows down the release of nutrients.

Ammonium nitrate is a popular choice for fertilizer because it is a good nitrogen source and relatively inexpensive.

Is Ammonium Nitrate Natural or Synthetic?

It was once mined as a natural mineral (niter) in the deserts of Chile, but it is no longer available except as a man-made compound. Ammonium Nitrate is a synthetic ionic salt.

How is Ammonium Nitrate Made?

Ammonium nitrate is made possible using the Haber process. Applying high pressure (200 times atmospheric pressure) and temperature (400 degrees C (780 F) alongside a specific iron catalyst enables the fixing of nitrogen from the air to form ammonia (NH3) by reaction with hydrogen.

The ammonia is then oxidated to produce a range of nitrogen oxides (some are waste products others are used for other purposes), one of which, NO2, is dissolved in water to form nitric acid (HNO3). 

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Ammonium chemical species
Some of the common ammonium chemical products.

Ammonium nitrate is then easy to make: an acid-base reaction between ammonia and nitric acid produces water-soluble ammonium nitrate, which is dried and formed into pellets ready for transport. 

Although stated to be an inexpensive product, it takes a lot of energy to run compressors to increase pressure and raise the reactor’s temperature.  

making ammonium nitrate fertilizer

Why Ammonium Nitrate is a Commonly Used Fertilizer

Here are some of the benefits of using ammonium nitrate fertilizer:

  • Provides nitrogen, which is essential for plant growth
  • Relatively Inexpensive
  • Easy to apply

Here are some of the drawbacks of using ammonium nitrate fertilizer:

  • Can be explosive if mixed with combustible materials
  • Hygroscopic, which can cause the fertilizer to cake and become difficult to apply
  • Can contaminate water and soil if not applied properly
bags of ammonium nitrate fertilizer ready to be transported

Ammonium nitrate fertilizer can be a valuable tool for farmers and gardeners. However, using it carefully and following the safety precautions listed above is important.

As you can see, it has benefits, but using it safely in the environment is up to humans aware of the risks.

I’m sure you’ve heard of the dead zone in the Gulf of Mexico. Nitrogen and phosphorus runoff from farm fields is partially responsible. 

gulf of Mexico dead zone
Photo Credit: USGS

Even gardening or lawn misuse can cause small-scale problems in nearby waterbodies and cause algae blooms.


How Do Plants Use Ammonium Nitrate?

Because ammonium nitrate is very soluble in water, the nitrogen released in solution is in a form that moves readily with soil water to the roots, where it’s immediately available for plant uptake.

It works quickly to green up plants and help them grow, but it also continues to flow with the water away from the root zone. 

I have more issues with the fact that the plants prefer quick meals (nature will always take shortcuts to save energy). However, when they do, the soil life that works symbiotically with plants to provide them with nitrogen is ignored and dies or moves away.

But to the plants’ chagrin, their little bacteria and fungal friends are long gone when the quick-acting ammonium nitrate fertilizer is used up. 

Ammonium Nitrate Toxic to the Environment

Ammonium nitrate can be toxic to the environment. It is a highly soluble salt that can contaminate water and soil. 

It can also release harmful gases into the air, such as ammonia and nitrogen oxides.

Here are some of the potential environmental impacts of ammonium nitrate:

  • Water pollution: Ammonium nitrate can contaminate water supplies, making them unsafe for drinking, swimming, and fishing. It can also cause algae blooms, which can deplete oxygen levels in the water and kill fish and other aquatic life.
  • Soil pollution: Ammonium nitrate can contaminate soil, making it difficult for plants to grow. It can also leach into groundwater, contaminating drinking water supplies.
  • Air pollution: Ammonium nitrate can release harmful gases into the air, such as ammonia and nitrogen oxides. These gases can cause respiratory problems in people and animals and contribute to smog and acid rain.

If you are using ammonium nitrate, following the manufacturer’s instructions for safe handling and disposal is important. You should also avoid spilling ammonium nitrate on the ground or in waterways.

rain run off of fertilizer after storm

Here are some tips for minimizing the environmental impact of ammonium nitrate:

  • Use only the amount of ammonium nitrate that is needed.
  • Do not mix ammonium nitrate with other chemicals.
  • Store ammonium nitrate in a cool, dry place.
  • Dispose of ammonium nitrate properly, according to the manufacturer’s instructions.

Following these tips can help protect the environment and ensure that ammonium nitrate is used safely.

Here are some additional information about the environmental impacts of ammonium nitrate:

  • Ammonium nitrate can contribute to eutrophication, a condition where excessive nutrients in the water cause algae to bloom. This can lead to the death of fish and other aquatic life.
  • Ammonium nitrate can also contribute to acid rain, caused by releasing nitrogen oxides into the atmosphere. Acid rain can damage trees, crops, and other plants and pollute water supplies.
  • Ammonium nitrate can also contribute to smog, a type of air pollution that can cause respiratory problems in people and animals.

It is important to note that the environmental impacts of ammonium nitrate can vary depending on the specific conditions. For example, the amount of ammonium nitrate released into the environment can affect the severity of the environmental impacts.

Additionally, the type of environment affected can also affect the severity of the environmental impacts. For example, ammonium nitrate is more likely to contaminate water supplies in areas with a lot of rainfall.

Using Fertilizers with Ammonium Nitrate in the Home on Microgreens

Many of the environmental problems listed above are larger-scale issues that concern farm-scale operations.

The amount of ammonium nitrate used to grow microgreens, either by adding granular pellets or using potting mixes that contain synthetic fertilizer, will not harm the environment and most likely will not add toxicity to our food.

At least, that is what the marketing plan tells us. 

potting mix with fertilizer

However, some people have issues with using synthetic fertilizers to grow their food. 

There are a lot of reasons not to use synthetic fertilizers.

  • Fear of uptake into the food
  • Amount of energy used to produce it
  • The impact that larger-scale use has on the environment
  • Organic food labeling regulations
  • Don’t want to add to the profits of companies that do not fit in with their moral beliefs of gardening or food production

My Personal Views on Synthetic Fertilizer Use Indoors & Outdoors

I’m a pragmatist. So, I try to do my best with the funds and resources I have available to me at the present.

If I can afford natural amendments and they are available, I will choose to use those products first.

I will feed the life in the soil with natural products so they can provide my garden plants with the nutrients and minerals they need so the healthy plants can provide the sugars that the soil life needs to keep the cycle going.

However, if I need the garden to produce so I can survive, I would use low concentrations of synthetic fertilizer to nurse the plants back to health and work harder to produce compost to feed the soil life so they are there when the plants are healthy enough to trade sugars for nutrients and minerals.

A stop-gap approach.

Would I use Miracle-Gro Potting Mix to grow microgreens since it contains synthetic fertilizers?

Only if that is all I could find, and I needed it to grow my weekly microgreens. It would be only short-term until I could get a potting mix with only natural ingredients.

I would use a grow media without any additives before I used a potting mix that contains synthetics and deal with the lower yield of microgreens.

For all of the reasons stated above for not using synthetics. However, I’m not too worried about chemical uptake in the food or the theory of organic principles per se.

It’s more about using natural products from smaller companies when possible and not feeding the multi-national, multi-billion dollar business monopolies. 

That said, I have no problems with people using any particular product. We all have choices and reasons for what we do.

I feel I am responsible for sharing my knowledge and thoughts with others so they can think more about their choices. It’s not my place, or anyone’s, to judge another for something as insignificant as an 8-quart bag of potting mix.

So, in short. I won’t use any potting mix with synthetics if I have a non-synthetic alternative that fits within my budget. 

The Home Microgreens Potting Mix is an all natural potting mix that contains no synthetic chemicals. It grows microgreens as well as any potting mix containing fertilizers or not. It is available in the Home Microgreens Store.

Unless noted, stock images by Depositphotos


  • Todd

    Todd is the founder of Home Microgreens & the Home Microgreens store. He also writes for several other websites, including MyViewFromTheWoods.com. Todd worked at a large farm market, garden & nursery center for 20 years. Somehow he snuck off to become a geologist and professor before coming back to his senses to write & lecture about microgreens and gardening. When not at the computer, he can be found in the garden, trout stream, or mountain trail with his new Springer Spaniel Caden.

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