Spring 2010

Cover Story

A world map shows global "greenness," a measure scientists use to study vegetation patterns in forest and croplands. Darker areas reflect denser, healthier plant life.

Seen in color on a world map, agricultural yields are telling. When it comes to corn, for instance, the American Midwest blazes brick red, a powerhouse of agricultural output. By comparison, most of the corn-growing tracts across Africa, Asia, South America and the former Soviet Union are yellow, a color that means these lands yield less than half the grain that Midwestern farms do.

There are other maps for other crops—all revealing significant yield gaps that add up to a disheartening atlas of hunger and poverty. But inside the yellow zones, many of the farms have the potential to produce much more—and in the near future, we’re going to need them to do just that.

“There’s not enough virgin farmland out there to meet the growing demand for food, so we’re going to have to increase production on the farms we have,” says CALS agronomist Josh Posner, who studies cropping systems in tropical countries. “It’s critical, however, that we do it in a sustainable way.”

The last significant uptick in global crop yields came during the Green Revolution of the 1950s, ‘60s and ‘70s. An international cohort of researchers, led by the late Nobel laureate Norman Borlaug, led a push to develop higher-yielding varieties of wheat and rice that dramatically boosted yields in Mexico, India, Pakistan and parts of Asia. The project helped turn Mexico into a net exporter of wheat and doubled wheat production in India and Pakistan. But the new crop varieties required irrigation and significant doses of chemical fertilizers and pesticides, which has made yield gains difficult to sustain.

“The Green Revolution model of breeding crops that respond to higher and higher levels of petrochemical inputs was very successful,” says Posner, “but it is increasingly being questioned as we learn more about the environmental impact of these systems and the rising costs of inputs make their economic logic questionable.”

So while the yield maps call out for a new Green Revolution, Posner says this time it has to be different kind of revolution. Instead of breeding crop varieties that depend on expensive and environmentally taxing chemical inputs for their yield gains, he says the focus should be on applying biology-based approaches to improve productivity, enhance soil quality and manage pests. That means developing more minimum-tillage systems, planting more cover crops and designing improved crop rotation systems. It also means breeding crops for factors beyond yield, including enhanced nutritional quality and for efficient use of limited resources.

“The future of food production in the tropics will include a mosaic of different farming systems,” he says. “However, there’s little incentive for the private sector to develop these systems, so the challenge of leading this greener Green Revolution really falls to the agricultural colleges of the world.”

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