The Nitrogen Cycle

This is a collection of three pieces on nitrogen, legumes, and soy originally written for the Digestable newsletter:


Last Tuesday, 2,750 tons of ammonium nitrate in a waterfront warehouse in Beirut exploded, killing over 160 people, injuring thousands more, and leaving 300,000 people without homes.  There’s been some great reporting tying this explosion to previous ammonium nitrate explosions near Galveston and Waco, TX in 1947 and 2013, Tianjinin 2015, North Korea in 2004, and even the Oklahoma City bombing in 1995. In these stories, the explosions are normally blamed on mismanagement of the facility or malicious intentions and ammonium nitrate is characterized as a “harmless” and even benevolent fertilizer that only explodes when exposed to “intense stresses heat and pressure,” but that’s not quite the case.

Nitrogen makes up about 75% of our atmosphere and is a key nutrient that plants need to grow, but in a classic water water everywhere but not a drop to drink situation, plants can’t absorb nitrogen from the atmosphere, they need to get it from the soil.  The story is often told that humans did all these weird and wacky things to help our plant friends out: humans poop out lots of nitrogen so farmers in Japan filled their veggie carts with poop from the city to take back to their farms, birds poop out lots of nitrogen so the U.S. government passed the lovely neocolonial Guano Islands Act to harvest guano from bird poop covered islands in the Pacific (and expand the nation’s global military presence).  Then our hero, Fritz Haber came along and said “Stoppt den Blödsinn!“ (he was German) “I figured out how to synthesize nitrogen from the atmosphere for our plant friends!”

Unfortunately, painting Haber like a Prometheus to plantkind is… just inaccurate.  The real reason he was doing this research in the first place was because it was WWI and Germany was cut off from purchasing saltpeter (potassium nitrate) from Chile to make bombs.  The short version of why explosions work is that the nitrate in ammonium and potassium nitrate is a molecule made up of one nitrogen atom and three oxygen atoms.  Fire needs oxygen to burn and those three concentrated oxygen atoms hanging out with the nitrogen can turn a small spark into a really big one. Bad boy Fritz learned how to synthesize nitrogen to make ammonium nitrate which allowed the Germans to keep killing lots of people.  That’s right, the initial purpose of Fritz Haber’s Nobel Peace Prize winning invention was what? To blow big holes in cities.

But it doesn’t end there, because the Haber-Bosch process was used to manufacture fertilizer.  It was used to manufacture a LOT of fertilizer – so much fertilizer that 50% of the nitrogen in your body and the body of every human on Earth, was probably synthesized using the Haber-Bosch process.  A harbinger of spring familiar to anyone who has lived in rural anywhere is a pick-up truck hauling a tank of pressurized anhydrous ammonia gas ready to be sprayed on a farmer’s fields. Literally it’s so ubiquitous that one of the first images I found in my search was this toy version of the scene.  

A pick-up truck hauls a tank of anhydrous ammonia gas.
A "Farm Country" branded toy of a four wheel drive pick-up truck hauling a tank of anhydrous ammonia gas

But the readiness and availability of nitrogen fertilizer coupled with pressure on farmers from the industrial agriculture system to produce higher yields leads to the sorry statistic that the average farmer uses twice the nitrogen fertilizer than their crops can actually use.  Suddenly, this nutrient which used to be a limiting factor for plant growth is so abundant that the plants don’t know what to do with it so when it rains, all that excess nitrogen (and phosphorous which I haven’t mentioned here but it plays a role too) runs off downstream into lakes and rivers.  When it gets there, algae gobble it up and multiply, often drastically changing the character of the body of water and choking out the other fish and plants that thrived in a lower nutrient environment.  A well-known instance of these aquatic explosions is the dead zone in the Gulf of Mexico, where excess nutrients from farms across the entire Mississippi watershed emptying into the Gulf regularly creates such a huge explosion of algae that these tiny plants use up all the oxygen in the water across an area that at times has been as large as the state of New Jersey.

The catastrophe in Beirut is a terrible atrocity but it is one of a string of explosions that together make up a much larger collective tragedy.  Industrial explosions of ammonium nitrate stretch back to midcentury, ammonium nitrate bombs have been dropped on cities since the second world war, and explosions of killing life occur annually and seasonally in our planet’s lakes, rivers, and oceans.  The simple process of synthesizing nitrogen from the air using heat (generated by fossil fuels of course), pressure, and a metal catalyst has fundamentally changed so many things about our world and come at innumerable cost.  But maybe the way forward is just as simple, maybe it’s smooth to the touch, maybe it’s small enough to fit in the palm of your hand.


So earlier I promised you all an answer to the nitrogen problem that involves a small smooth round object and then I just disappeared like all the oxygen in the Mississippi delta after an algae bloom.  I’m sorry for leaving you all hanging but I’m back with the answer! 

While you were reading about the extreme lengths humans have gone to in order to get nitrogen from the air to the ground you probably wondered if there’s way to fix nitrogen that doesn’t involve colonizing islands in the Pacific or using tons of fossil energy to synthesize highly explosive fertilizers.  You were absolutely right to wonder this, after all the human race wasn’t living under constant famine before the Haber-Bosch process was invented – and plants certainly do a good job growing on their own without the help of highly specialized human assistance.  So what’s the one weird trick to fix nitrogen that corporate ag companies and chemical manufacturers don’t want you to know? 



(please clap)

Something to know about me is that I have a mental “environmentalism” bingo board that is always in the back of my mind.  The entire bingo board is one big space that says “Legumes have root nodules that host symbiotic nitrogen fixing bacteria.” To break this statement down, legumes (a.k.a. beans and other friends) have little growths on their roots that serve as cozy homes for friendly bacteria that can turn nitrogen from the air into soil nitrogen for plants to eat.  Whether you’re talking about ecology, food history, climate science, farming, environmental policy, or any related fields, this fact is bound to come up eventually and whenever it does I bounce up and down in my chair like the excitable child I am and then post it to the meme page I created to celebrate the phenomenon.  

Maybe I’m a bit overzealous in my celebration of rhizobial bacteria, but I do believe it’s one of the most important environmental concepts.  Think about it, not only do plants use chlorophyll to literally make food from sunlight, they’re able to harness the magic of symbiosis to take this notoriously hard to find nutrient and focus it right at their roots.  Not only that, but legumes fix enough nitrogen to not only feed themselves, but all the plants around them that can’t fix their own nitrogen.  If you’ve been searching for a model of how to be a good neighbor, look no further.

Civilizations around the planet have been effectively harnessing this leguminous superpower for most of human history (shout-out to the three sisters).  Staying at my parents’ house on Dakota land in rural Minnesota reminds me that the vestiges of this knowledge are even visible in the fields of the U.S. industrial agricultural system through the standard crop rotation of growing corn one year and soybeans the next.  (those are soybeans in the photo)

But this gesture at ecological awareness within the industrial agriculture system doesn’t really cut it.  Corn is a notoriously hungry crop. It’s not corn’s fault, the plant is a tropical grass that we keep insistently planting in less nutrient rich temperate landscapes where soybeans can’t fix enough nitrogen to satisfy it.  On top of that, the intense cycle of deeply tilling soil every year and leaving fields without any vegetation to hold the soil down for half the year means that all that nitrogen the soybeans worked to fix escapes back into the atmosphere or washes away as the soil erodes.  That’s why farmers spray tanks of ammonia gas and cow manure on their fields every year, because the rigid factory-like agricultural system prevents these plants from working together the way they evolved to do.

So industrial agriculture sucks. Duh. But farmers and other plant people have been implementing some very cool ways to put this plant-knowledge back into the system! There’s intercropping, planting crops that play nice together next to one another like in the three sisters tradition.  Instead of corn having to survive off the leftover nitrogen from last year’s soy, the legume is right there fixing nitrogen in real time for everyone to eat.  This method also helps reduce pests because if a bug really likes to eat corn, it’s harder for it to hop from corn plant to corn plant if there are squash and beans planted in between.  Then there’s strip tilling, where instead of tilling the whole field, you only till the strip where you’re planting seeds.  Similarly, no-till farming uses machines that dig a little hole exactly where the seed is planted and the rest of the soil remains undisturbed.  Reducing tilling keeps those lovely hard-won nutrients from escaping the soil and prevents soil erosion. 

And then there’s my favorite, cover crops! This is where you plant a small, low to the ground crop over the winter or among the seeds of your main crop to hold the soil in place and prevent erosion.  Some of the most popular cover crops are clover and alfalfa which are (wait for it) LEGUMES! So when you plant clover over the winter, you not only keep your soil in place and sequester a little more carbon dioxide, you also fix more nitrogen in the soil!  Some cover crops, like alfalfa and rye, can even be harvested and sold, providing an extra financial incentive for farmers.  If we were able to remove the legislative and economic hurdles that safeguard the current agro-industrial complex and implement these practices on a national scale, it would mean an actual green revolution for our food system, climate, and global ecology.  We would be able to grow more and better food with less fertilizer and pesticides, restore countless eutrophied lakes and rivers, and begin to rebalance our planet’s nitrogen and carbon cycles.

In the city of Beirut following the ammonium nitrate explosion, people are behaving like beans.  Like the neighborhood mutual aid organizations that formed during COVID lockdown and the collecting of resources, expertise, and power happening at Black Lives Matter occupations and demonstrations, neighbors focus on the things at their disposal and what they can generate to fill everyone’s needs.  In the face of these tragedies, people form root nodules, spaces to share resources and form coalitions and ask our governments and systems to support us the way we support one another.  


I took an environmental ethics class in undergrad from a discombobulated wrinkly-shirted prof with some slightly unhinged teaching methods. His classes were seen as easy A’s since students were able to choose their own grade and readings were mostly optional as his lectures were made up of tangents unrelated to any assigned readings. I’m all for unconventional teaching methods and self-directed learning, but with how competitive tenured university positions are, I can’t disentangle this semi-successful experimental teaching style with the privilege of being a white man – especially at a college that has only elevated three women of color to the rank of full professor.

This all came to a head when, in a lecture supposedly about animal ethics, the aforementioned professor asked the class why they think “women” are more likely to be vegetarian than “men.” Brainy dudes love to ask this question, the ethics prof actually asked it two different times during the term. I also had another prof ask it in a lecture on Brazillian history this past term as well, provoking an anecdote from a fellow student about how difficult it is for him to be a heterosexual male vegetarian and to have waiters give him the wrong plate when he’s at a restaurant with a non-vegetarian woman. To me, the answer is obviously socialization – that women learn empathy while men are taught competition and domination. But for cis-dudes who have never been asked to interrogate their own beliefs or behaviors, it becomes this mythical question: what is it about women that makes them prone to vegetarianism?

In the ethics class, one of the jocks in the back row tried to formulate an answer. “Maybe it has something to do with the fact that women’s bodies are better at processing the estrogen in soy.” As a Big Queer Nerd sitting in the front row, I was already infuriated by the question itself, but the answer that vegetarianism = soy = estrogen = women sent me into a seething rage that continues to smoulder in my gut microbiome this very day.

One more anecdote before we dig into it: It’s 2018 and I’m at a Rockefeller owned farm in the Hudson Valley. I had had a lovely time so far, slept in a big bed and pooped in their indoor composting toilet (another Rockefeller venture), toured their on-farm mill and bakery, and later we were to visit a beautiful dairy/wedding venue – also pioneered by the oiliest of oil families. The farmer was taking my coworkers and I through their grain fields – heritage wheat and barley varieties interseeded with tallgrass prairie and given long rotations with soy (to fix nitrogen remember) and fallow prairie to rebuild organic matter. Truly a dream.

We were just finishing up at the grain silos where barley and soy was stored for animal feed when my gowanus-mom coworker, god bless, asked about giving her kids tofu. Apparently she had heard something about it not being good for them. The farmer, and this is a person who is deeply invested in regenerative agriculture and sustainable foodways, responds by saying that though he sells soy as feed to animals he would never give his kids unfermented soy, only fermented products like tempeh, because “the estrogen will mess with their hormones.”

Folks, listen to me when I say this: eating soy is not going to influence your hormones. Men are so afraid they’re going to grow boobs or that their balls are going to fall off and it’s just not going to happen. If eating soy was going to significantly influence your hormone levels we wouldn’t have trans folks fighting for the legalization and legitimization of hormone therapies – you could just switch up your diet.

The science behind the fear is that soy and its derivatives contain “phytoestrogen,” a plant hormone that is similar but not the same as estrogen. Animal hormone receptors can pick up and respond to phytoestrogens, but not always in the same way as estrogen, and the studies that strike fear into men’s hearts are mostly ones conducted on lab rats where they are fed diets consisting entirely of soy or have derivative phytoestrogens injected into them. These studies tell us important things about dietary hormone uptake, but to extrapolate them to the tofu in your fridge is not how science works. Also, jokes on you farmer guy because fermented soy products are actually higher in phytoestrogens.

This white masculine insecurity is also pervasive in conservative internet circles, where emasculated men (read: anyone outside the proudboy-white-nationalist-meninist ecosystem) is referred to as a “soy boy” – inferring that they’ve been feminized by their soymilk flat white (see also: the rise of almond milk, oat milk, and whey protein supplements). Not only is this fear of soy rooted in sexism and transphobia, it also reflects the racist portrayal of asian men as feminine and impotent. Soy cannot be bad for you if it’s been a dietary staple for a kabillion years – unless the people for whom soy is a staple are themselves seen as backward and emasculated.

This complex of sexualized and racialized attitudes form the dietary requirements of masculinity. Vegetarianism = soy = Asia = emasculation = estrogen = women. The framing of the question “why are more women than men vegetarian” and men’s attempts to answer it, reveals the real answer and the real question: 

Why are men less likely to be vegetarian? Because they are afraid. They’re afraid of excommunication from the boys club, of acknowledging privilege, of giving up the only way they’ve ever learned to move through the world. 

So reject masculinity and eat soy with wild abandon (unless you’re allergic)! Feel the phytoestrogens coursing through your blood infusing you with feminine energy! Not only does the plant play an important role in agroecosystems it has one of the best coefficients of digestion (more of it is nutritionally available) of any food meaning that if you’re looking for protein, soy is better than meat. Take that, men.

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