Have crop yields peaked?

Unlike other efforts to estimate yield potential, the Global Yield Gap Atlas uses a bottom-up approach.

Feeding a world population of 9 billion people that is estimated by 2050 could be harder than first thought if the conclusions of a report released last week come true.

Researchers at the University of Nebraska-Lincoln note that yield gains are, in fact, decreasing, which will make meeting global food demands harder. The research team, which reported its findings in Nature Communications, believe about 30% of the major global cereal crops -- rice, wheat and corn -- may have hit their maximum possible yields in farmers' fields.

The team, which includes Kenneth Cassman and Patricio Grassini of the UNL Agronomy and Horticulture Department, and Kent Eskridge, statistics, studied past yield trends in the countries with the greatest cereal production, and they offer evidence against projected linear crop yield increases.

The researchers point to a popular idea that corn yields can rise to 300 bushels per acre, on average, by 2030, but point out that to achieve that goal, producers would have to push yields up 3.6% per year. "This rate is four times greater than the rate of increase in U.S. [corn] yield from 1965 to 2011," the researchers said.

Unlike other efforts to estimate yield potential, the team’s Global Yield Gap Atlas uses a bottom-up approach. Working with colleagues at Wageningen University in the Netherlands, the team is recruiting agronomists worldwide to identify key agricultural areas and collect data about local conditions and farming methods. These data are then scaled to the national, regional and global levels.

They also are developing the necessary methodology, such as accurately converting short-term weather data into long-term patterns and scaling up local yield estimates. All information and methodologies are shared on the new public website, www.yieldgap.org .

“The beauty of this project is that it is a global project but with local relevance,” said Grassini. The atlas will estimate global yield trends and food security and also help individual countries identify production potential to better strategize resource allocations and trade opportunities.

Agricultural economist Justin van Wart brings a large-scale perspective to the project. His doctoral work for Cassman included developing methods to scale local data to regional and global levels. Now, as a postdoctoral fellow, the Nebraska native finds himself in a new country almost every month, presenting his methods and helping to build collaborations.

“It’s amazing to work with internationally renowned agronomists,” van Wart said. “It’s kind of surreal to be shaking hands and talking directly with the person whose paper I was highlighting for a report just a few months ago.”

With a $2 million grant from the Bill & Melinda Gates Foundation, the team is working in India, Bangladesh and 10 Sub-Saharan African countries. Grassini also has developed collaborations in Argentina and Brazil with funds from the University of Nebraska’s Robert B. Daugherty Water for Food Institute.

Securing food for the future requires accurate information and decades of planning, said Cassman, who also chairs the Independent Science and Partnership Council, which advises the Consultative Group on International Agricultural Research, or CGIAR, on the scientific merit of global research projects. “We need to do a better job than we have in the past, and that’s what the Global Yield Gap Atlas will do.”

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