A Dangerous Fixation
Synthetic nitrogen was born 100 years ago; it’s why half of us are alive.
The lack of farm-level data on yields, timing, rate, and amount of nitrogen application, indigenous soil nitrogen, and other important variables is a key factor holding back improvements in nitrogen-use efficiency. “It’s surprising how little data there is,” says Kenneth Cassman, a professor of agronomy at the University of Nebraska–Lincoln. “We have some idea, but it’s not good enough when we have to double food production and reduce environmental impact all in the next 30 years” to meet anticipated demand from a growing global population.
The small fraction of applied nitrogen that gets taken up by crops is one source of inefficiency. But we are profligate even with the nitrogen that actually makes it into the plant. Last month, the United Nations Environment Program released a study detailing some of the compounding sources of inefficiency. For example, worldwide about 80 percent of nitrogen harvested in crops and grass goes to feed livestock instead of feeding people directly. Much of that nitrogen winds up in their manure and then gases off as it sits in giant open lagoons near intensive animal production centers or when it is spread onto fields without being properly mixed into the soil. And according to the U.N. Food and Agriculture Organization, a whopping one-third of all food produced globally is wasted—discarded by consumers or lost or spoiled before reaching the market.
The UNEP study authors propose a “20:20 for 2020” target of improving nitrogen use efficiency by 20 percent and reducing overall nitrogen use by 20 million tons each year. They also suggest that consumers in developed countries become “demitarians” by reducing their meat consumption by half, since meat-based diets are much less nitrogen-efficient than plant-based diets.
But “all of the demand for increased livestock products is coming from India, China, Africa,” Cassman says, so reduced consumption of meat in richer countries “doesn’t make much difference for projections of food supply and demand.” Indeed, 80 percent of the global increase in consumption of nitrogen fertilizers between 2000 and 2009 came from India and China.
Cutting back on agricultural production is not much of an option in a world where the population is expected to reach 9.2 billion (and possibly as high as 10.5 billion) by midcentury.
While feeding 10 billion people will require synthetic fertilizers, bequeathing them a livable climate and cleaner air and water will require much more judicious use of applied nitrogen. “The solution is to provide tools so we can actually measure what farmers’ nitrogen use is,” Cassman says. “Every farmer should know what their nitrogen fertilizer efficiency is in a fairly robust way.”
Such information could help policymakers design better incentives to encourage more farmers to adopt promising techniques for reducing nitrogen loss, such as conservation tillage (using little or no plowing), soil erosion control, planting winter cover crops, and more precise management of the timing, rate, and volume of fertilizer application. Davidson points to efforts to limit farming near streams and in 100-year flood plains as other steps that can make a dent in the problems associated with nitrogen runoff.
“In the past 40 years [American farmers] have massively improved nitrogen efficiency without really trying a lot,” Cassman says. “In the next 30 years I guarantee they can do at least as well, if not better, if they just have confidence they can do it. All we’re talking about is trying to accelerate it through better decision-making and promulgation of research.”
He proposes setting up information-sharing systems and incentive-based programs that would reward farmers who improve their own nitrogen efficiency, say, 1 percent every year. “It would take the onus off of penalties, make it like a sport like track or swimming where you’re competing against yourself. They would buy into it, lower costs, and improve their profitability.”
After a century of nitrogen fixation, it’s hard to even imagine a world without it. And sheer demographic momentum means we will continue to rely on it until the next Carl Bosch comes along to upend the rules of agriculture.
While Oppau’s legacy today reaches into every corner of the globe—and our bodies—the facility itself didn’t last that long. In 1921, workers discovered that 4,500 tons of ammonium nitrate stored in a warehouse had hardened during a period of wet weather into an unusable mass. So, to loosen it up, they drilled holes in it, stuck some dynamite in, and lit the fuse. The resulting blast killed more than 500 people (including those workers), destroyed 80 percent of the homes in the town, and ripped the roofs off of homes 15 miles away.
It’s difficult to blame them, though, since no one knew at the time about the fertilizer’s explosive properties. And they were keen to not let such a valuable resource go to waste.
Jonathan Mingle is currently at work on a book about black carbon pollution.