By Brendan Borrell
juny 18, 2009
Heavy use of fertilizers causes environmental problems in the United States and China, but a global team of scientists is prescribing more use of fertilizers for sub-Saharan Africa
Although overuse of fertilizer has caused environmental damage around the world, some scientists are calling for an increase in its application in African agriculture.
In a paper published today in Science, a group of 16 researchers from the United States, Brazil and China want to provide more subsidies for fertilizer use to enrich poor quality soil in Africa, while decreasing fertilizer use in other parts of the world. “The situation in Africa is totally different from where China is now or where the United States and Europe are,” says lead author Peter Vitousek, an ecologist at Stanford University.
Their commentary came out of a workshop at the Aspen Global Change Institute last year, sponsored by NASA and several nonprofits. The researchers point out the “nutrient imbalance” between corn growers in northern China, who are using 1296 pounds (588 kilograms) of nitrogen fertilizer per hectare every year compared with 15.7 pounds (7 kilograms) per hectare in Kenya.
Amb 500 pounds (227 kilograms) of China’s nitrogen input going to waste every year on each hectare of land, the researchers say it could halve fertilizer use with no decline in its impressive corn yields. Kenya, per contra, is losing 114 pounds (52 kilograms) of nitrogen per hectare per year, meaning that soil fertility is on the decline, trapping farmers in a cycle of land degradation and poverty.
Of course, asking China to cut its use of fertilizer use isn’t likely to upset environmentalists, Vitousek says. Human fertilizer use has doubled the amount of nitrogen and phosphorous entering rivers. Agricultural runoff pollutes freshwater streams, leading to the kind of unchecked algae blooms that have smothered marine ecosystems in the “dead zone” at the mouth of the Mississippi River.
That’s why controversy will likely stem from the scientists’ call to increase subsidies for fertilizer use in Africa. Vitousek’s colleagues in the environmental community, who he declined to name, have already approached him and said, “I understand there’s a move to introduce fertilizer in African agriculture . . . Haven’t we learned anything?”
But there are concerns from the policy side as well. Ephraim Nkonya, an agricultural economist at the International Food Policy Research Institute, says that increasing fertilizer subsidies is not going to solve Africa’s food problems and they may in fact aggravate them. He points out that 35 percent of Zambia’s agricultural budget goes to fertilizer. Nkonya, a Tanzanian, says the problem is that the subsidies often end up in the hands of the “rich” and “well-connected” rather than poor farmers.
Nkonya says that getting fertilizer to the right people is only a small part of the puzzle. He recommends using organic soil fertility management by adding manure to the soil and alternating corn crops with beans, which fix nitrogen from the atmosphere and make it available to crops. These practices, he says, "are quite environmentally friendly and at the same time they increase yields.”