Demystifying the Nitrogen Cycle

Most growers – from backyard vegetable gardeners to large-scale producers – understand that nitrogen is essential for plant health. Many people, however, don’t understand the nitrogen cycle, how it works, or why it is so important. Instead of letting natural processes take over, they use nitrogen-based fertilizers to improve their harvest.

It sounds mysterious, but the nitrogen cycle is nature’s way of converting nitrogen from the air and surrounding soil into a useful substance for plants, microbes and other organisms. If you have a healthy soil structure, the nitrogen cycle will be self-sustaining – you won’t need to rely on chemical fertilizers. Let us show you how the nitrogen cycle works, and what you can do to make sure you have all the right bacteria in your soil.

How Does Nitrogen Fixation Work?

Nitrogen fixation is the first step of the process. During this phase, nitrogen is “fixed” into the soil from the air, where it is converted into ammonia and nitrates. There are only two ways for nitrogen to enter the soil: lightning strikes and nitrogen fixing bacteria. Lightning strikes are relatively rare, and a single strike only affects a very small area. Nitrogen fixing bacteria are responsible for the vast majority of nitrogen fixation and conversion, which is why great soil health with plenty of soil bacteria is so essential.

The Assimilation Phase

During this stage, plants take advantage of the nitrogen compounds fixed into the soil. Plants absorb the ammonia and nitrates through their root systems, using them to create chlorophyll and amino acids.

It’s the amino acid production that makes nitrogen so essential for plant health. Plants use amino acids to create proteins, which are crucial for healthy growth. Proteins are also necessary to help plants produce enzymes and hormones that help them flower, bear fruit, fight disease and more.

The Decay Process

The nitrogen cycle partially starts over as plants and animals die or create waste. Dead plant and animal material along with animal waste contains organic nitrogen that plants absorbed from the soil or animals ingested by eating nitrogen-rich plants. As these materials decay, soil bacteria and fungus convert the nitrogen into ammonia so that plants can use it again. This process is called “ammonification” or “mineralization.”

Carefully Balancing Nitrification

The beauty of healthy soil is that it has an incredibly diverse colony of bacteria and microbes. Throughout the nitrogen cycle, different types of bacteria are responsible for fixing nitrogen or converting it from decaying matter. The nitrification process is no different – another type of bacteria uses some of the ammonia from the decay process to create nitrite.

However, too much nitrite is a bad thing because it is toxic to plants. That means that yet another type of bacteria needs to be present in the soil to convert nitrites into nitrates, which are an essential plant nutrient.

Completing the Cycle: Denitrification

Denitrification is the final step of the nitrogen cycle. In this process, certain kinds of bacteria use nitrogen instead of oxygen to breath, releasing the nitrogen back into the atmosphere. Denitrification happens in oxygen-deprived soil, waterlogged soil and soil that has heavy concentrations nitrogen. Carbon from decaying plant and animal matter speeds the denitrification process, which helps to bring balance back to nitrogen-rich soil quickly.

Jump-Start Your Garden’s Nitrogen Cycle

The nitrogen fixing bacteria that make the nitrogen cycle go round will provide your plants with all the organic nitrogen they need. If your soil seems to be underperforming, we recommend inoculating it with a culture of sustainable bacteria rather than resorting to inorganic alternatives.

Not only will your plants grow healthier and stronger, but you may notice some other benefits as well. Soils with a healthy bacterial colony tend to increase water retention, and they’ll help plants resist diseases and fungal infections like powdery mildew. You may even discover that fruits and vegetables – in addition to being bigger and more numerous – taste better too!


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