A worm's eye view of nitrogen
What you see here is approximately what the roots of my green bean plants looked like when I pulled them up this morning: covered in tiny white nodules. What could they be? They look like tiny egg sacks. Or perhaps a terrible root disease. In fact, they are little bundles of nitrogen, created by certain species of bacteria.
Life on earth could not exist as we know it without nitrogen. Nitrogen is the very stuff of amino acids, the building blocks of protein. Nitrogen is essential to RNA and DNA. Without it, we would collapse into a smudge on the ground. Nitrogen constitutes approximately 80 percent of the air we breath. But in order for it to be taken up into the food chain where we and other life forms can use it, it must be “fixed” into something soluble. Here’s where some very special breeds of bacteria enter the picture.
Working in concert with certain plants, especially those in the legume family, these bacteria perform a minor miracle, extracting nitrogen from air in the soil and “fixing” it into something the plants can take up through their roots. The nitrogen is packed into the little nodules that form on the roots of beans and clovers and other leguminous plants. This is why clovers and vetches and other plants in this family are (or were) so popular with farmers as a cover crop to plant on fields that needed a boost of nitrogen. That’s the basis of organic farming.
The bacteria accomplish their nitrogen fixing feat with the aid of an enzyme called nitrogenase. Not that you should stay up nights worrying about it, but the world’s entire supply of nitrogenase would probably fit in a common garden bucket. This is one problem better left to nature.
But humans got tired of waiting for bacteria to make nitrogen. Around the turn of the 20th Century, a couple of German scientists invented a process for making nitrogen artificially. The process requires lots of pressure and heat and uses natural gas as a feed stock. Most of this nation’s corn is fertilized using nitrogen in the form of anhydrous ammonia made using the German process. Because modern fertilizer depends on fossil fuel, and because artificial nitrogen tends to run off the soil and pollute rivers and streams, it’s fair to wonder whether this kind of farming is really sustainable.
Good thing those bacteria are still on the job. We may really need them again some day. A good reason, maybe, to take care of our soil.
We are engaging the concerns of a hungry planet--slowly--right here in our kitchen garden in the District of Columbia, one mile from the White House.
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