Corn. Where does our food come from?

These days, most people might think corn, the ubiquitous grain that provides the bulk of feed for our livestock; most of the sweetener for our soft drinks and snacks; and a large amount of our cooking fat.

But where does the corn — and other staple crops — come from? The answer to that question lies beneath our feet. Healthy soil is our food system’s bottom line. Without it, food crops won’t grow.

Farming, especially on today’s industrial scale, is tough on soil, draining essential nutrients. The most critical nutrient is nitrogen, the building block of plants. A lot of energy and money have been spent figuring out how to replace it in the soil.

In the past 50 years, led by the United States, global agriculture has come to rely increasingly on a cheap, synthetic form of nitrogen produced in fertilizer factories that are powered by natural gas and other fossil fuels.

Before World War II, when the fertilizer industry was in its infancy, farmers used very little synthetic nitrogen. By 1964, U.S. farmers were applying about 4.3 million tons annually. In 2007, the last year for which the U.S. Department of Agriculture has figures, farmers dropped 5.7 million tons on the nation’s corn crop alone. We now know that the undeniable benefits of synthetic nitrogen come with serious costs, both to the environment and to public health.

In this special Grist series, we’ll be looking at where synthetic nitrogen comes from and what our reliance on it is doing to our health and to the health of our waterways and climate. We’ll also be looking at ways in which synthetic nitrogen can be used more wisely — and, as much as possible, phased out.

The question of where our food comes from will take us on a journey from the farm out to the fertilizer factory — and even farther, to the globe’s finite and far-flung natural gas deposits. And more important than where synthetic nitrogen comes from is where it will take us.

As with anything fueling a system that feeds a nation of 300 million, there are no easy answers to the nitrogen dilemma. But we will pose the hard questions — and try to generate debate about a critical ecological issue that remains obscure and little-discussed.

Check out the first piece in the series: “The dark side of nitrogen.”