When Fritz Haber first showed the world how to fix nitrogen from thin air, the results were earth-shattering. Synthetic fertilizer fueled the green revolution and set off a population bomb. Now, 100 years later, we need another soil fertility breakthrough—one without the ecological casualties.
By James McWilliams
Every now and then, an innovation comes along that fundamentally redefines the way humans live. Some curious tinkerer has a breakthrough and harnesses fire, steals electricity from the sky, or compresses steam to power an engine. Or, as a German chemist named Fritz Haber did on July 3, 1909, reaches into thin air, turns nitrogen gas into a solid, and—with the help of colleague Carl Bosch—pressurizes it into a substance that changes the way we feed ourselves.
The Haber-Bosch process, as this innovation came to be called, “fixed” nitrogen. Initially, this fixed nitrogen was an ingredient of war. When nitrogen reacts with hydrogen, the result is ammonia. Ammonia yields nitric acid, which gives munitions an explosive lift. Not only was this development essential to German interests during World War I (especially after the British blocked access to Chilean nitrate mines), it also helped make 1918 the deadliest year of the ordeal.
What killed people during war, however, nourished them during peace. Along with phosphorus and potassium, nitrogen ranks as one of the most critical nutrients for nurturing plant growth. The Haber-Bosch process made it possible to synthesize nitrogen into nutrient-dense fertilizer on an industrial scale. The result was skyrocketing crop yields throughout the twentieth century. These increases were impressive enough, in the words of environmental scientist Vaclav Smil, “to detonate the population explosion.”
This isn’t hyperbole. Due primarily to Haber’s innovation, global food production sent the population from 1.6 billion to 6 billion in less than a century. Synthetic fertilizer not only fueled this growth, it sustained it—feeding the world a steady and relatively cheap supply of wheat, corn, and rice. Today, a century after the Haber-Bosch process was established, this method of synthesizing nitrogen fertilizer (although now more energy-efficient) remains essentially unchanged. Without fertilizer, Smil writes, “about two-fifths of the world population would not be around.”
Yet Haber-Bosch has been saddled with a conundrum—as is often the case with paradigm-shifting technologies. The advent of synthetic fertilizer was a dream come true in terms of yield but has proven over time to be an ongoing environmental nightmare, primarily because of nutrient runoff into sensitive aquatic ecosystems.
The next 100 years of food production will demand more fertilizer than ever before. The problem is that, given the considerable problems with its current usage, fertilizer cannot proceed on the same course it has taken over the past century. What’s needed is another breakthrough. This time around, though, it may be a matter of breaking through long-held ideological barriers that divide organic farming and conventional agriculture, rather than reinventing the wheel.
Before Haber-Bosch, fertilizing crops was a relatively ad hoc affair. For roughly ten thousand years prior to 1909, farmers obtained nitrogen and other plant nutrients through a variety of catch-as-catch-can methods. They relied on animal manure (“dung”); they planted near rivers to capture silt; they included nitrogen-fixing legumes in the crop rotation; they churned plant waste into the soil (“green manure”); and they used human feces (“night soil”). By the nineteenth century, wealthier farmers purchased various nutrients from companies that were vigorously stripping the earth of mineral deposits throughout South America. Given this array of options, every farmer was his own soil manager.
Whatever sources the preindustrial farmer exploited, the common denominator was that they came from earthy processes considered to be natural. These natural processes aimed to build rich and healthy humus—soil endowed with stable, nutrient-retaining, organic matter. But stable soil meant stable yields. Systematic yield increases were nonexistent before the advent of synthetic inputs. Producing more food on less land isn’t a goal that’s necessarily on nature’s agenda. For commercial farmers seeking to reach broader markets as agricultural land became more expensive, this posed a problem—farmers were just as interested in profit as anyone else.
Haber and Bosch’s primary accomplishment was to empower agriculture to bypass nature. Rather than slowly constructing a secure layer of humus that fathers could pass on to sons, commercial farmers began importing packaged nutrients designed to breathe temporary nutritional life into otherwise exhausted soil. A wide range of mostly organic byproducts, most of them produced on the farm, thus yielded to a handful of industrially synthesized inputs—all of them imported from a chemical company. Farms evolved into factories.
Numerically speaking, the benefits of this transition were stunning. Average per-acre corn yield rose from 25 bushels in 1926 to 170 in 2006. As for wheat, 14 bushels per acre was standard in 1918; yet 80 years later, 49 bushels wasn’t unheard-of. Because of nitrogen fertilizer, the U.S. became the world’s breadbasket, exporting more grain than any other nation on earth. So enthusiastic was the adoption of synthetic fertilizer that those who used it were said to be practicing “conventional” agriculture. Never before was so much food being produced on so little land. To this day, density of production continues to be modern agriculture’s defining feature. Synthetic fertilizer is its engine. And for that, many people hate the stuff.
This hatred also has a history. The leading voices against synthetic fertilizer have traditionally come from the organic sector. In An Agricultural Testament, published in 1940, English botanist Sir Albert Howard began the impassioned project of promoting organic agriculture as a responsible alternative to conventional production. As Howard saw it, increasing dependence on synthetic fertilizer destroyed not only the farmer’s independence but also his soil, the precious substrate that Howard called agriculture’s “foundation stone.” Subsequent research has proven Howard right. While synthetic fertilizer has allowed remarkable yield increases, nitrogen fertilizer has slowly leached natural fertility out of the soil while compacting much of our agricultural land into the consistency of a parking lot.
The problems associated with synthetic fertilizer hardly end there. Nutrient runoff from synthetic fertilizer has poured so much unabsorbed nitrogen and phosphorus into the Gulf of Mexico that a hypoxic “dead zone” the size of New Jersey (or at least Rhode Island) has formed there. To make one ton of ammonia fertilizer, 33,500 cubic feet of natural gas is required; this means that five percent of the world’s natural gas is used for fertilizer production. Nitrogen runoff can escape into the atmosphere as nitrous oxide, a greenhouse gas that’s 300 times more powerful than carbon dioxide. Most recently, there’s been talk of “peak phosphorus,” much of which is mined from hills in Morocco. Even staunch advocates of synthetic fertilizer, such as Tom Bruulsema, director of the International Plant Nutrition Institute, admit that the current usage of fertilizer is not “indefinitely sustainable.”
Jeff Moyer couldn’t agree more. Moyer is farm director for the Rodale Institute, a nonprofit dedicated to organic methods, and former head of the USDA’s National Organic Standards Board. When he considers the future of fertilizer, his thoughts turn to composted manure, cover crops, legumes, and other natural supplements that reduce the soil’s “leakiness” while enhancing its capacity to retain carbon, nitrogen, phosphorus, and potassium as well as other micronutrients. In the spirit of Albert Howard, Moyer worships humus. Rodale’s mission, he explains, is to endorse agricultural practices that will “change the microbiology of soil,” regenerating beaten-down and acidified land into a “drought-proof” and nutrient-rich version of Howard’s “foundation stone.”
Considerable research supports Moyer’s faith in the power of compost. Increasing organic material in the soil dramatically improves its moisture-holding capacity. Compost not only contains a plethora of plant nutrients but also moderates soil pH levels to render those nutrients optimally available. (Synthetic fertilizer acidifies and salinates the soil.) Soil enhanced with compost attracts beneficial insects, worms, and microorganisms—often called the “microherd”—that aerate soil while potentially reducing the need for chemical pesticides.
Moyer’s organic option is a bold rejection of the Haber-Bosch process, and clearly it has a lot going for it. But there’s a catch—several of them—to an all-organic approach. First and foremost, there’s yield. When it comes to the production of essential row crops grown with organic fertilizer, yields drop substantially. A recent study relying on USDA data from over 14,000 farms revealed that organic yields were 40 percent lower for winter wheat, 29 percent lower for corn, 34 percent lower for soy, 58 percent lower for sorghum, and 41 percent lower for rice. (1) With 2 billion people expected to join the planet within the next 40 years, these numbers are, to say the least, problematic for the prospects of exclusive organic fertilization.
A related drawback is that compost refuses to “spoon feed” nutrients to match the needs of plants. Compost releases nitrogen at a steadily sluggish rate, but crops initially need very little nitrogen and then require a sharp burst when they enter the “grain fill” phase. Because the organic conversion process fails to conform to this quirky cycle of demand, excessive amounts of compost must be added after the crops start growing. Conventional growers, however, can select specialized fertilizers that “spoon-feed” nutrients precisely when the crop needs them. Compost simply acts on its own terms.
Using compost results in runoff, and not just nitrogen runoff. The attempt to meet nitrogen requirements with repeated applications of organic compost also means inadvertently adding excessive levels of phosphorus, which can be particularly damaging to aquatic ecosystems. According to Tanya Brouwers of the Organic Agriculture Centre of Canada, “A budget based on providing all the N for crops with manure will inevitably lead to soil phosphorus excesses.” When I asked Ross Penhallegon, a horticulturalist at Oregon State University and author of Values of Organic Fertilizers, to compare the nutrient runoff rates for organic and conventional systems, he laughed—noting that his organic friends hated to be reminded of his answer: “There’s no difference. They’re both the same.”
A final problem with compost involves something we rarely associate with organic methods: greenhouse-gas emissions. Advocates of organic agriculture rightfully praise the ability of organic soil to sequester carbon. Rarely mentioned, however, is the fact that agriculture generates less than two percent of carbon dioxide emissions. By contrast, it accounts for one-third of methane and 80 percent of nitrous oxide emissions. Methane and nitrous oxide are exponentially more powerful than carbon dioxide. They are also both particularly problematic when it comes to organic fertilizer. The composting process releases almost three percent of its carbon in the form of methane, whereas excessive amounts of applied nitrogen lead to higher rates of nitrous oxide output than in well-managed conventional systems.
Surveying this evidence, Steve Savage, a Stanford-trained biologist with a PhD in plant science, explains, “When you combine that with the amount of manure needed to fertilize a crop, you end up with a ‘carbon footprint’ that is three to eight times as large as if you delivered the same amount of nitrogen with synthetic fertilizers like urea.” In agriculture, nothing is as straightforward as we’d like it to be. Or, as Penhallegon says, “It’s never ‘us versus them.’”
Of course, these drawbacks are by no means deal-breakers for organic agriculture. They simply suggest that, if organic methods are going to play a meaningful role in fertilizer’s future, organic standards will have to incorporate conventional methods and vice-versa. This hybrid proposal will likely send shivers down the spines of both conventional and organic proponents. But they should relax, because it’s not nearly as heretical as it sounds.
Several recent studies have demonstrated that combining organic and conventional fertilizers can enhance soil fertility while improving yield. One study applied equal amounts of composted chicken manure and conventional fertilizer to corn fields in Bangladesh and saw yields increase by a factor of five. (2) Another found that “combined organic and inorganic fertilization enhances organic matter in soils and increases yield of sweet maize.” (3) These may not be earth-shattering discoveries, but they speak optimistically about the potential of hybrid systems.
Researchers at McGill University and the University of Minnesota recently published in Nature an article suggesting that a multivaried approach to nourishing crops is on the verge of becoming a mainstream practice. The authors write, “By combining organic and conventional practices in a way that maximizes food production and social good while minimizing adverse environmental impact, we can create a truly sustainable food system.” (4)
Agriculture, for its part, doesn’t tolerate a whole lot of magical thinking. So even if the world wanted to convert to organic fertilizer, drawbacks notwithstanding, we couldn’t—at least not in time to confront the impending boom in caloric demand. Today in the U.S., organic produce is harvested from 0.5 percent of all agricultural land. That’s point-five. This figure means a lot of things, but for the future of fertilizer it means that we’ll continue to rely heavily—almost exclusively—on synthetic fertilizers. The future of fertilizer thus not only centers on the kinds of fertilizers we now use, but also on how judiciously we use them. The good news on this score is that there’s considerable room for improvement when it comes to how we apply synthetic fertilizers to global cropland.
Between 20 and 60 percent of the nitrogen housed in synthetic fertilizers is typically lost to runoff or volatilization (the process whereby nitrogen is vaporized into ammonia). Ross Penhallegon, the Oregon State horticulturalist, insists that this number will be dramatically reduced as we become “extremely good at what we’re doing.” The way to become “extremely good” at fertilizer conservation, according to Tom Bruulsema of the International Plant Nutrition Institute, is by honoring the “Four Rs”—fertilizing at the right time, right place, right source, and right rate.
Granted, all this might sound like gimmicky ag-jargon. However, in a funny way, the Four Rs approach returns farmers to the days before synthetic fertilizer, when every farmer acted as his own soil manager and no two farms were treated alike. Every field—and even specified regions within the same field—can, with the tools of precision agriculture, be evaluated and treated in terms of its unique nutrient profile. Areas needing excess nitrogen or phosphorus would get precisely that amount of nitrogen or phosphorus—no more, no less.
The first step toward agricultural micromanagement is tweaking the physical properties of the fertilizer itself. Polymer-coated “controlled-release” fertilizers, first pioneered in the 1970s, are finally becoming cost-effective. They spoon-feed nutrients at a pace that matches a particular plant’s demands. And this means that nitrogen doesn’t sit idly in the soil—more goes into the plant, and less runs off into rivers and lakes or escapes as nitrous oxide. Controlled-release fertilizers have the potential to lessen nitrous oxide emissions by 30 percent while decreasing runoff by as much as 50 percent, according to Alan Blaylock, Manager of Agronomy for Agrium Advanced Technologies.
Such savings can be further maximized by paying closer attention to water. Farmers have typically used “center-pivot irrigation”—a one-size-fits-all watering regimen that washes truckloads of nitrogen fertilizer into aquatic habitats. New technologies, however, now allow farmers to practice “variable-rate irrigation.” After mapping the topography of his cropland (including every slope gradation and pooling area) down to the square meter, a farmer uploads the data to software that connects with a global positioning device and orchestrates a symphony of sprinklers, instructing them when to turn on and off to achieve optimal water dispersal. Less water equals less runoff.
Finally, geneticists are looking at the fertilizer problem from the plant’s perspective. Plant breeders are selecting for genetic traits that enable corn plants to absorb more nitrogen more effectively. Some are even looking at ancient corn—the form of corn that thrived as a wild grass—to pinpoint the genes responsible for the “root architecture” that was once able to suck ample nutrients from nitrogen-poor soil.
And then there’s the elephant in the room. When it comes to the future of fertilizer, that elephant is corn—well, corn and soy but especially corn. Most nitrogen fertilizer in the U.S. goes directly to the production of corn. The majority of that corn goes to feed cows who in turn degrade the environment through overgrazing, methane emission, and the defilement of aquatic ecosystems.
Furthering the needless waste of this wholesale conversion from plant to animal flesh is the fact only about 40 percent of each animal is edible—we don’t eat bones. Thus 60 percent of the nitrogen that manages to make its way into the corn feed ends up having nothing to do with human caloric intake. Add to this perverse cycle the fact that it takes about 140 pounds of nitrogen to grow an acre of corn, but closer to 60 pounds to grow an acre of kale—a crop that, alas, people eat.
And that brings us to the Big Rub. If commercial agriculture exploited the Haber-Bosch process to grow a diverse array of food for people to eat rather than a narrow array of food for livestock to eat, we would not have anything close to a fertilizer crisis. Nor would we have an agriculture-related emissions crisis. Or, for that matter, a water crisis.
Of course, we are not going to see a massive conversion to a plant-based system of agriculture designed to radically foreshorten the distance between fertilization and human consumption. But what we might see, what we will have to see if we want healthy soils and enough to eat, is an approach to fertilization that judiciously blends the wisdom of the organic past with the advancements of the conventional future. And that would be a game-changer every bit as earth-shattering as Haber-Bosch. That would be our breakthrough.
James McWilliams is an associate professor of history at Texas State University, San Marcos, and author of Just Food: Where Locavores Get It Wrong and How We Can Truly Eat Responsibly.
Hossain, N., M.G. Kibria and K.T. Osman. 2012. Journal of Pharmacy and Biological Sciences 3(2):38–43.
Efthimiadou, A. et al. 2010. Australian Journal of Crop Science 4(9):722–729.
Seufert, V., N. Ramankutty and J.A. Foley. 2012. Nature doi:10.1038/nature11069.
5. Ausubel, J.H., I.K. Wernick and P.E. Waggoner 2012. Population and
Development Review 38 (Supplement).
6. Ray, D.K. et al. 2012. Nature Communications doi:10.1038/ncomms2296.
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