WHY Decomposition Uses Nitrogen (or, What I Learned Today #2)

A couple of weeks ago I wrote about what happens when sawdust decomposes. But the account was incomplete, and I am here today to rectify that error. Call me honest, call me obsessive; I’m going to set the record straight, sawdust-wise.

I wrote then that sawdust makes a lousy lawn fertilizer because it requires so much nitrogen to decompose, and it contains very little. So far, so good. But when I wrote that “it requires nitrogen to break down, and it’ll make use of whatever it can lay its sawdusty little paws on,” I misspoke.

I know what you’re thinking: sawdust does not have paws. But that’s not where I’m headed. No, what’s at stake here is not anatomy, but agency. It’s a mistake to refer to sawdust as making use of nitrogen or to suggest that sawdust “gets” nitrogen whether with paws, hands, or any other part of its being.

It’s a mistake, in a sense, even to refer to sawdust (or anything else) as decomposing, as if this were something that it did all by itself. In fact, of course, something decomposes it. And not just one something; lots of somethings. These somethings are called—brace yourself—decomposers.

When you toss a wilted lettuce leaf onto the compost pile, the micro-organisms there, recognizing a good thing when they see it, go into overdrive and start reproducing madly. (There’s no accounting for what turns people on.) And of course, they all have to eat. (There goes your leaf.) And–and here's the crux–they all require nitrogen.

The air we breathe, the air that permeates the soil, is almost 80% nitrogen. All living things need it—it makes up about 4% of plant mineral content and 3% of yours, being part of proteins, amino acids, and nucleic acids. Just try building a protein without nitrogen. Come on, I dare you.

Yet no plants or animals can make use of atmospheric nitrogen. Go figure. Even the leguminous plants that “fix” nitrogen from the air need the help of very specific bacteria. (Why? What evolutionary advantage can there be in the complicated chemistry that in fact makes nitrogen available to us?)

The decomposers—worms, micro-organisms galore—also need nitrogen. And most of them, like us, need it in soluble compounds, not in the pure, gaseous form that is so plentiful. So when these madly multiplying micro-organisms multiply madly, going hog-wild in the compost heap over a leaf of wilted lettuce, they use whatever nitrogen they can find. Lettuce, of course, even when wilted, contains plenty. But sawdust doesn't have much, which is why a pile of sawdust next to the garage will be there a lot longer than a pile of leaves: there isn’t enough nitrogen to support a big population of decomposers.

So it isn’t the sawdust that requires nitrogen: it’s the decomposers. They do the work. They’re the neglected, ignored, side-lined, overlooked workers of the soil—and in my previous post, I perpetuated this discrimination.

In my defense, I would point out that the fault lies at least partly in the language. If  “decompose” were a transitive verb (X decomposes Y) none of this would have happened. The language itself discriminates, inviting us to ignore the process by which the work of decomposition occurs, and to undervalue the myriad millions who do that work.

Well, I for one refuse to participate any longer in this travesty. No longer will I overlook these, the down-trodden of the world. I intend to celebrate their unsung lives. This post is just the beginning.

Who will join me? Who will step forwards, proud and free, to restore to these tiny toilers the dignity they deserve?