Throughout the history of agriculture, farmers have been trying to figure out what nutrients plants need and how to get the nutrients to them. In the last quarter of the 20th century, the nutrients became available and relatively affordable in the developed world. The fertilizer industry in the U.S. and other wealthy countries has matured. Here the question is now – how much fertilizer is enough, and how much is too much?

In contrast, the question in the developing world is – how do we get enough fertilizer to support growing populations? Developing countries like India and China have become the largest producers and consumers of fertilizer. The U.S. is third. The poorest countries, like most of Africa, are begging the rich countries for fertilizer to stave off hunger in their people.

Demand for fertilizer has more than doubled between 1970 and today in the developing world, while in rich countries, farmers have been growing more food with less fertilizer from about 1990 on. In the U.S. farmers produced 74 percent more corn in 2005 than they did in 1980, but they used only 3 percent more nitrogen and 20 percent less phosphate and 24 percent less potash.

All living things need nutrients. Before history was recorded, some early farmer discovered that plants grew better on land that had been enriched by animal manure. Ancient Egyptians are known to have added ashes from burned weeds to soil. Greek and Roman manuscripts show that they knew about manure as well as crop rotation systems where legumes, like alfalfa, will replenish the soil after years of depletion by wheat or corn.

But it wasn’t until the 20th century that scientists understood the chemical reactions that take place inside plant cells. Today’s farmers know that nitrogen is used by plants to synthesize proteins, nucleic acids and hormones. Phosphorus and potassium are used as raw materials for nucleic acids and other proteins. These are the most important nutrients in modern fertilizers. Scientists also know there are a host of other nutrients needed as well – calcium, magnesium, sulfur, iron, chlorine, copper, manganese, zinc, molybdenum and boron.

Scientists know that one pound of modern fertilizer has more of the major nutrients than 100 pounds of manure. Vaclav Smil, a professor at the University of Manitoba, calculates that without nitrogen fertilizer, there would be insufficient food for 40 percent of the world’s population, at least based on today’s diets.

Today, most of the nitrogen in fertilizer is made through a chemical process that uses natural gas to extract nitrogen from the air around us. While air is plentiful, natural gas is not. The price fluctuations of the late 2000s made fertilizer prices soar and then crash.

Farmers in the U.S. and Europe have responded to the fluctuations by learning how to apply only enough fertilizer at only the right time so that most of it is absorbed by the plants. Many farmers will employ soil testing services that tell them exactly how much nutrient is needed for the plants that the farmer is planting. It used to be that farmers would do one test for, say, an 80-acre field. Today, farmers will use Global Positioning System (GPS) data to take samples on every 2.5-acre grid within that field. Then, they’ll feed the results into a GPS enabled fertilizer application system to put on only enough fertilizer for the plants to use.

Precision application is becoming more important because putting too much fertilizer on means that the excess just washes off into streams, lakes and the ocean or leaches down through the soil layers until it hits groundwater. That both wastes money and creates pollution.

Fertilizer runoff has created “dead zones” in the world’s oceans where nitrogen-rich nutrients feed huge algae “blooms.” When the algae dies, it sucks up the oxygen dissolved in the ocean and that section of ocean dies. In 2008, the journal Science reported that the number of marine dead zones around the world has doubled almost every 10 years since the 1960s. In the Gulf of Mexico, the dead zone covers a swath of ocean nearly the size of Massachusetts, and it has doubled in size in the last 20 years. Other zones have developed in the Chesapeake Bay, the Baltic Sea, coastal China and the Pacific Northwest. In Norway, the lobster fishery in the Kattegat Sea has collapsed.

To avoid wasting fertilizer, U.S. farmers like Troy Otte (left) use soil testing services to guide their fertilizer applications. “With fertilizer right now you want to be pretty exact,” he says. “It’s not the ballgame of 30 years ago. We’re making sure that we’re putting on what the plants need.” Troy tests his soil every year. “Now we’ve got into the grid sampling in which every two-and-a-half acres will be a separate sample.”

Chris Ziegler (right) farms outside of Waco, Nebraska, and says testing makes good economic sense
. “We’re cutting our nitrogen rates down by up to 40 percent,” he says. “Nitrogen has really taken off as an input, price-wise. It would be about four times more expensive [now] as when I came back [into farming] in ’95… [After] cash rent, fertility inputs per acre would be the next most expensive thing that you’re putting out there.”

In Africa, the problem is not too much fertilizer it’s too little. Subsistence farmers in places like Africa and Southeast Asia can’t afford to buy the chemicals and there aren’t enough animals to produce manure. People are going hungry.

In the African nation of Malawi, for instance, international aid organizations in 1998 started giving farmers “starter packs” of grain seed and fertilizer, enough to grow about one-quarter of an acre of healthy plants. That was only about 15 percent of the size of a typical family plot in the country, but it produced a bumper crop of corn. Then the donors got worried that giving away fertilizer would not be “sustainable,” so they cut back on their donations. Farmers who had learned the value of fertilizers tried to adapt, but agriculture in the country collapsed. Emergency grain supplies had to be imported from the West. Many still starved.

In 2008, increased worldwide demand for fertilizer drove up prices, and the recession slashed incomes for most subsistence farmers in places like Vietnam. Malnutrition soared.

“Putting fertilizer on the ground on a one-acre plot can, in typical cases, raise an extra ton of output,” says Jeffrey D. Sachs of Columbia University. “That’s the difference between life and death.”

Written by Bill Ganzel, the Ganzel Group. First published in 2009. A partial bibliography of sources is here.

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