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Are Corn and Soybean Trend Yields Increasing at a Faster Rate?

tour c
Scott Irwin Scott Irwin
Laurence J. Norton Professor
of Agricultural Marketing
Department of Agricultural
and Consumer Economics
217-333-6087;
sirwin@illinois.edu

Some argue that trend yields for corn and soybeans in the U.S. have increased at a faster rate since the mid- 1990s due to more rapid development and adoption of new technology, particularly in the form of improved seed genetics. This research examines state average yield and weather data for Illinois, Indiana, and Iowa over 1960-2006. Modeling results suggest that increasing yields since the mid-1990s are better explained by favorable growing season weather conditions in the Corn Belt rather than an increased rate of technology development or adoption. Technology may currently be developing and adopted at a faster rate than in the past and could eventually result in an accelerated trend increase in corn and soybean yields, but the effects were not yet observed through 2006. For now, the long-term linear trend is likely still the best forecast of expected yield prior to the growing season.

Authors: Mike Tannura, Scott Irwin, and Darrel Good