Nitrogen

Air. We couldn’t live without it, since it contains oxygen. But most of the air seems to be pretty useless to us. When you inhale -- you fill four fifths of your lungs with nitrogen. Nitrogen atoms come -- just like hydrogen and oxygen -- in pairs.

We write it as N-two. Actually, there are plenty of things in our body that need nitrogen atoms to function: The muscles, skin, blood, even the DNA… It’s just that … we can’t use nitrogen atoms directly from the air. Plants need nitrogen atoms too. But they can’t get it from the air either. What is it about gaseous nitrogen that makes it so hard to use?

It has to do with the strong bond between the nitrogen atoms, which makes the molecule very stable. We say that nitrogen gas is inert, which means that it’s unwilling to react with other substances. This property is something we can use when we are packaging food! By replacing the air with pure nitrogen, the food lasts much longer. The nitrogen atoms that our bodies need, we get through our food.

But how did the nitrogen get in the food itself, if neither plants nor animals can get it from the air? Well, it’s due to bacteria that live in the soil and in some plants. These bacteria usually bind nitrogen in two forms: … either with hydrogen: in an ammonium ion … … or with oxygen: in a nitrate ion. When the nitrogen is bound, or fixed in those forms -- only then can the plants use it … … and the nitrogen can continue upward in the food chain. So it’s thanks to these bacteria that our bodies can get the nitrogen they need.

But most plants we grow for food need more nitrogen than these bacteria can produce -– or our plants would grow much slower. One way of adding more nitrogen, is with manure: droppings from animals. But natural manure is not enough for the amount of food we want to grow. That’s why we produce fertilizer, through a chemical process that can also bind gaseous nitrogen from the air. These nitrogen compounds that we spread on our fields eventually soak down into streams and lakes and can make them overgrown.

That’s why we have to control how much fertilizer is used. To produce enough food for the earth’s population, we need to add extra nitrogen to our fields. Whether it is fixed naturally by bacteria, or synthetically in a factory, the plants need nitrogen to grow. The nitrogen in the air isn’t as pointless as it may first appear. It’s really as essential as the oxygen.