Rebalancing the nitrogen relationship: how microbes can help.

In the great balancing act of life on Earth, plants have long been helping to breathe for the entire planet. Through photosynthesis, plants take in carbon dioxide from the air. They release oxygen and turn sunlight into sugars. These sugars feed entire ecosystems. In return, during respiration, they consume oxygen and break down some of those sugars to fuel their growth. This dance — photosynthesis and respiration — contributes to the rhythm of life for nearly every living thing.

But there’s another gas in the atmosphere that’s just as critical to life, and far more difficult for plants to access: nitrogen.

A breath of free nitrogen — But not for plants.

Nitrogen makes up about 78% of the air. Yet plants, despite being masters of air-breathing photosynthesis, can’t use atmospheric nitrogen (N₂) directly. That’s because N₂ is a triple-bonded molecule — incredibly stable and chemically inert. For nitrogen to be used by plants, it must be “fixed” into “reactive” forms like ammonium (NH₄⁺) or nitrate (NO₃⁻), which can then be absorbed by roots and incorporated into amino acids, nucleic acids, and chlorophyll.

Nitrogen isn’t just important — it’s essential. It forms the core of the proteins that build plant tissue, the enzymes that drive metabolism, and the genetic material that enables inheritance. Without nitrogen, there is no growth. No greening. No life.

This vital need led to one of the most important evolutionary partnerships in history: between plants and nitrogen-fixing microorganisms.

Microbial partnerships: How tiny living things bring atmospheric nitrogen down to earth.

Some microbes — notably certain species of Rhizobium, Mesorhizobium, Bradyrhizobium, Azospirillum, Azotobacter, and Pantoea — possess an enzyme called nitrogenase, which can break the bonds of atmospheric N₂ and convert it into usable forms. This is no small feat. Nitrogenase is a fragile enzyme, easily inhibited by oxygen and requiring a lot of energy. But the microbes have good reason to make this investment: for those living in or near plant roots, the relationship is mutually beneficial. The plant offers carbon-rich exudates; the microbe provides nitrogen that the crop host so badly needs.

In legumes like soybeans and alfalfa, this relationship is famously visible in the form of root nodules filled with symbiotic Rhizobium bacteria. But all crops: even non-legumes like wheat, corn, tomatoes, berries, and fruit trees, benefit from free-living nitrogen-fixers in the rhizosphere. It is one of the reasons that cultivating a healthy soil is so important. In this thin layer of soil surrounding plant roots (the “rhizosphere”), microbe-plant interactions are most intense, and when functioning properly, this region is like a nutrient factory for plants. 

The synthetic shortcut: How humans learned to fix nitrogen ourselves

Humans aren’t perfect, but we are a clever species. In the early 20th century, two German chemists — Fritz Haber and Carl Bosch — developed a process to industrially fix nitrogen from the air, combining it with hydrogen under high heat and pressure to make ammonia. This invention changed everything.

The Haber-Bosch process enabled the mass production of nitrogen fertilizers — and with them, a revolution in agriculture. Global crop yields skyrocketed. Famine became less frequent. It’s estimated that synthetic nitrogen now feeds about half the world’s population. Millions of lives have been saved because of this. But this success came with unintended consequences.

The hidden costs of synthetic nitrogen.

For growers, nitrogen has always been a blessing — a visible, reliable push for crop growth. But as time has passed, we’ve begun to see the cracks in the system. We now know that excessive nitrogen use leads to:

Soil degradation: Perhaps less obvious, but just as serious — repeated use of synthetic nitrogen without biological balance can suppress microbial diversity, lower organic matter, and contribute to acidification. 

Nutrient leaching: Especially in sandy or compacted soils, nitrate leaches below the root zone, entering groundwater and contributing to nitrate contamination.

Algal blooms: Runoff from nitrogen-heavy fields feeds aquatic algae, choking waterways and creating “dead zones” in lakes and coastal areas.

Nitrous oxide emissions: A potent greenhouse gas, N₂O is released when microbes break down excess nitrogen, contributing to climate change.

While none of this sounds good, I think it is important to note that no one purposely chose these consequences. We have all been lured by the idea of inexpensive and abundant food, which has placed enormous pressure on growers to produce and produce cheaply. I grow weary of the commentary that positions farmers as somehow environmentally irresponsible, when in fact they are in closer touch with the land than the vast majority of us. We all have a better understanding now of the costs of overuse than we did back in Haber and Bosch’s days. In addition, even if there weren’t environmental consequences to nitrogen– we need to take note that even from the grower and crop perspectives, too much nitrogen isn’t always a good thing.

The crop health consequences:

Overuse of nitrogen can:

Cause excessive vegetative growth, making crops more prone to lodging (falling over) and less focused on reproductive development leading to delayed flowering and reduced fruit set. 

Destroy the fertility of the soil over time. Leading to reduced yields, increased inputs, and reduced profitability.

Reduce the production of secondary metabolites — the compounds that help plants defend against pests and pathogens and enhance the quality, taste, and value of produce. 

Disrupt microbial symbioses, including with beneficial fungi like mycorrhizae and nitrogen-fixing bacteria.

Increase vulnerability to pests and diseases, as overly lush tissue can be more attractive to insects and softer for fungal entry.

Reintroducing balance: Managing the relationship with N, microbially.

Nature has already solved the atmospheric nitrogen challenge. And increasingly, growers are turning to the original solution: microbial nitrogen fixation. Modern biological products use carefully selected strains of nitrogen-fixing microbes — either free-living or root-associated — to bring back the nuanced, efficient nitrogen delivery that plants evolved with. Instead of applying nitrogen in large synthetic doses, these microbes deliver it in small, more continuous quantities, right where it’s needed.

Using a strategy of less fertilizer and more microbial health supports more balanced vegetative and reproductive growth; protects the existing microbial life in the soil; reduces fertilizer costs for growers; and enhances crop resilience to environmental stress. When plants get nitrogen through microbes, it’s not a flood, in which most of the N gets away and wastes critical farmer dollars. When plants get nitrogen from microbes, it is a smaller, steadier stream. How much total Nitrogen is fixed by microbes in association with microbes varies widely depending on the crop, the microbe, and the environment (For a comprehensive review of the biological nitrogen fixation topic see Ladha, Peoples et al., 2022) But what we do know is this: biological nitrogen fixation is a much different supply structure: moderate in nature, and continuously mediated by a mutually beneficial relationship.

Meet the microbes: Some well-known nitrogen-fixing bacteria

A number of microbial species are used in modern nitrogen-fixing formulations. These include: Azotobacter chroococcum which is a free-living soil bacterium that fixes nitrogen and also produces growth-promoting hormones; Paenibacillus polymyxa which is a nitrogen-fixer that also solubilizes phosphorus and produces antifungal compounds; Bacillus megaterium which is not a primary nitrogen-fixer, but enhances uptake of fixed nitrogen and solubilizes phosphorus; Gluconacetobacter diazotrophicus which is an endophytic nitrogen fixer originally isolated from sugarcane, now used in many crops. But there are also others.

A symbiotic relationship: The nitrogen-fixing consortium in Komens

At Impello, we have Komens — a living nitrogen management system built from a blend of nitrogen-fixing and nutrient-supporting microbes. Komens is a partnership of two nitrogen-fixing bacteria. One, a free-living rhizosphere species, Azospirillum brasilense which nutritionally supports rooting, and fixes and facilitates nitrogen uptake. Another, Pantoea dispersa, can be free-living or endophytic, and in addition to N-fixation, also aids in the solubilization of phosphorus, another crucial nutrient for crop health.

Together, these microbes form a symbiotic team that: fixes nitrogen consistently throughout the season, enhances nutrient cycling, improves microbial diversity in the rhizosphere, and supports overall plant vigor and yield. Importantly, Komens is compatible with most existing fertility programs and can be applied via drip, drench, or in-furrow applications. For some practical recommendations about how to begin to have a more balanced relationship with nitrogen, see our guide here. 

Coming full circle: The air is still full of plant food

Nitrogen is still everywhere — 78% of the air — and the solution to unlocking it doesn’t require breaking the nitrogen cycle. It just asks us to look back to the soil, and to the partnerships plants evolved over millennia. Microbes like those in Komens help reestablish the ancient balance between atmosphere, soil, and plant. They deliver nitrogen with precision, protecting yield potential and the environment at the same time. For growers facing rising input costs and environmental pressure, microbial nitrogen fixation offers a way forward: one rooted in biology, grounded in data, and designed for long-term resilience.