Sustainable Food

The Fertilizer Divide

by Natasha Chart

categories: Climate, Community Development, Distribution, Farm Economics, Livestock, Policy

Published July 01, 2009 @ 12:19PM PT

While plant breeding has done its part, and irrigation a lion's share, in bringing global crop productivity up over this last century, synthetic and mineral fertilizers sealed the deal.

Plants need more than nitrogen, phosphorus and potassium (N-P-K), but an abundance of those three key, limiting nutrients will get them growing well, usually even if there are micronutrient deficiencies. So the prominent N-P-K listings on fertilizer bags are generally most crucial, and arguably the most critical of these is nitrogen.

While the Green Revolution is attributed in large part to hybrid crop varieties, these do poorly when not supplied with the abundant irrigation and nutrient resources provided through the industrial agriculture system. As much as the biotech industry claims to be overcoming these input requirements, they have yet to do so, and hope is not a plan.

Industrial agriculture uses fertilizer synthesized from natural gas, which is running into price and availability constraints similar to that found with other fossil fuels. Further, using nitrogen fertilizer in excess of what can be absorbed by plants and organisms residing in the soil are a significant source of water pollution and the formation of nitrous oxides, which are powerful greenhouse gases.

Now, a new study has quantified the global fertilizer use divide, with the not-too-surprising findings that industrialized countries use too much and African agriculture may be in need of a lot more. From the press release:

... A co-author, F.S. Zhang of China Agriculture University, and colleagues recently conducted a study in two intensive agricultural regions of northern China in which fertilizer use is excessive. Their results showed that farmers there use about 525 pounds of nitrogen fertilizer per acre (588 kilograms per hectare) annually — releasing about 200 pounds of excess nitrogen per acre (227 kilograms per hectare) into the environment. Mr. Zhang and his co-workers also demonstrated that use of nitrogen fertilizer could be halved without loss of yield or grain quality, reducing nitrogen losses by more than 50 percent in the process.

At the other extreme are the poorer countries of sub-Saharan Africa, like Kenya and Malawi. In a 2004 study in western Kenya, a co-author, Pedro Sanchez, and colleagues found that farmers used only about 6 pounds of nitrogen fertilizer per acre (7 kilograms per hectare) — little more than 1 percent of the total used by Chinese farmers. And unlike China’s soil, cultivated soil in Kenya suffered an annual net loss of 46 pounds of nitrogen per acre (52 kilograms per hectare) removed from the field by harvests.

“Africa is a totally different situation than China,” said Mr. Sanchez, director of tropical agriculture at the Earth Institute at Columbia University. “Unlike most regions of the world, crop yields have not increased substantially in sub-Saharan Africa. Nitrogen inputs are inadequate to maintain soil fertility and to feed people. So it’s not a matter of nutrient pollution but nutrient depletion.”

[Study authors note that farmers in the European Union and United States have both seen dramatic improvements in fertilizer use efficiency in recent decades.]

... Since 1995, the imbalance of nutrients–particularly phosphorus–has decreased in the Midwestern United States, in part because better farming techniques have increased yields. Statistics show that from 2003 to 2005, annual corn yields in parts of the Midwestern United States and north China were almost the same, even though Chinese farmers used six times more nitrogen fertilizer than their American counterparts and generated nearly 23 times the amount of excess nitrogen.

“U.S. farmers are managing fertilizer more efficiently now,” said the co-author Rosamond Naylor, director of Stanford’s Program on Food Security and the Environment. However, environmental problems have not disappeared. “The dead zone in the Gulf of Mexico persists due to continued fertilizer runoff and animal waste from increased livestock production,” said Ms. Naylor, a professor of environmental Earth system science and senior fellow at Stanford’s Woods Institute and Freeman Spogli Institute for International Studies. ...

There is concern within the environmental and policy communities that calling for increased fertilizer use and subsidies in Africa, as the authors do, could either replicate the hazards of US agricultural pollution or end up further reinforcing class inequality in areas where subsidies often benefit the already well-off the most.

Considering how little fertilizer is used in Africa, a modest increase there would probably be more than offset by the substantial decreases that Chinese agriculturalists could make, if they were inclined to be more efficient in their use of inputs. Though, as you might expect, I'd be much more in favor of encouraging polyculture farming practices that were mixed with animal husbandry and the use of animal waste as fertilizer.

The main problem in US agriculture is that the animals have been so separated from crop growing areas, given so many drugs and strange foods, and their waste so concentrated, that their manure is toxic. Particularly with cattle, who've also been fed such an unnatural diet that they're host to far more bacteria, such as E. coli O157:H7, that are dangerous to humans, that their manure is a biohazard in ways that grass fed cattle's waste is not.

A program to subsidize low income African farmsteads in securing small flocks of goats, sheep or chickens, depending on their access to land, might be a better, more self-replicating way to get them the needed soil nutrients. With chickens and animals like goats and sheep that can be milked, this also provides a farm family with extra protein during the animals' lifetimes. It's a solution that would require a little more creativity and human resources, but would probably have more stable long-term costs than a solution dependent on the global market for fossil fuels.

Because while it would be silly to deny that they need help, all types of help are not created equally.

(Photo credit: Lukas on Flickr, from a One Acre Fund project in Kenya, where a woman demonstrates adding small doses of fertilizer directly to the planting hole.)