National Geographic : 2013 May
Fertilized World 111 stuff—just seven pounds per acre on average. Alternative sources, such as manure or legume crops, are scarce as well. Many in Africa’s rural villages have fallen into a set of vicious circles. Fearing hunger, they concentrate on crops like rice or corn that deliver maximum calories but that tend to strip nutrients from the soil. Depleted land delivers increasingly poor harvests, leaving farmers too financially strapped to afford fertilizer, from whatever source. And since there is little de- mand for commercial fertilizer, no one makes it locally, so it’s imported and expensive. According to many experts, African soils are being mined. The natural reservoirs of fertil- ity—nutrients stored in the organic matter of decomposing roots and leaves from previous centuries—are shrinking as farming extracts more nitrogen, phosphorus, and potassium every year than it replaces. This leaves the land progressively less able to feed the people who depend on it—“a scenario for disaster over the long run,” according to the World Bank. The average grain yield in sub-Saharan Af- rica is about 900 pounds per acre, just one-fifth the average in China. Nearly everyone who’s looked at the situation agrees: African farmers need more nitrogen to improve their harvests and their lives. But there’s a raging, bitter debate over where they should get it. Some, like Jeffrey Sachs at Columbia Univer- sity’s Earth Institute, believe that increasing agri- cultural production demands more commercial fertilizer, and if poor African farmers can’t afford it, then wealthier nations should provide it. In 80 villages across ten different African countries, Sachs’s Millennium Villages Project passes out bags of improved seeds and fertilizer. And the project’s having a big impact, according to its own data. In the millennium villages of Tan- zania, Kenya, and Malawi, grain production doubled almost immediately. In 2006 the government of Malawi started providing cheap fertilizer to about half the na- tion’s farmers. Production of corn doubled— although good rains get much of the credit. These programs, however, are haunted by doubts about the future. Fertilizer subsidies were tried in many African countries during the 1970s and 1980s but fell out of favor because they were expensive and plagued by corruption. Malawi’s current subsidy program is already in trouble: The government is running out of money to pay for it. “Africa cannot afford massive amounts of fertilizer,” says Sieglinde Snapp, a crop scientist at Michigan State University. A more sustain- able approach, she says, is greater reliance on nitrogen-fixing plants. Thousands of farm fami- lies in Malawi have begun growing nitrogen- adding pigeon peas and peanuts on their land, replacing some of their corn. It’s part of a ten- year-old experiment begun by local hospitals, farmers, and agricultural researchers. Because peas made the soil more fertile, the next season’s corn harvest was larger—more than making up for the fact that less land was be- ing planted with corn. “Less corn is more corn,” says Snapp. Plus that bonus crop of pigeon peas provided more nutritious, protein-rich meals. “But it didn’t happen overnight,” says Snapp. “It took education on how to use the legumes. It was 20 years of work, with a hospital involved. People changed their recipes.” Snapp’s observation—that acquiring and con- serving nitrogen in the future will take consid- erable know-how and patience—is echoed by many people engaged in this worldwide quest. Asked what Chinese agriculture needs most, soil scientist Zhu Zhaoliang responds quickly, “More scale”—meaning larger, more skillfully managed farms. Ron Rosmann, in Iowa, explains that farming without added nitrogen “takes more management, more labor, more attention to detail. We’re kind of fanatics.” A century ago, when chemist Fritz Haber first learned how to capture nitrogen from the air, synthetic fertilizer seemed like an easy shortcut out of scarcity, delivering a limitless supply of agriculture’s most important nutrient. Yet new limits on nitrogen are appearing. This time the innovations that save us—and our planet—may not be invented in a chemistry laboratory. In- stead they may come from farmers and fields in every corner of the world. j everyone agrees: African farmers need more nitrogen. but there’s a raging, bitter debate over where to get it.