Are U.S. Corn and Soybeans Becoming More Drought Tolerant?

Tian Yu, Bruce A. Babcock
October 2009  [09-WP 500]

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Suggested citation:

Yu, T. and B.A. Babcock. 2009. "Are U.S. Corn and Soybeans Becoming More Drought Tolerant?" Working paper 09-WP 500. Center for Agricultural and Rural Development, Iowa State University.


An objective drought index that measures the dry and hot conditions adversely affecting crop yields is used in a regression analysis to test whether corn and soybeans have become more drought tolerant. Results indicate that corn yield losses, whether measured in quantity terms or as a percentage of mean yield, have decreased. The null hypothesis that the absolute level of soybean yield losses due to drought has not changed cannot be rejected. But yield losses in percentage terms have decreased over time. Because drought is the primary cause of yield loss in the U.S. crop insurance program and because U.S. crop insurance rates assume that percentage of yield losses are constant over time, these results indicate that U.S. crop insurance rates in the Corn Belt are too high.

Keywords: corn, crop insurance rates, drought tolerance, soybean, yield risk