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Greater Sensitivity to Drought Accompanies Maize Yield Increase in the U.S. Midwest

Science  02 May 2014:
Vol. 344, Issue 6183, pp. 516-519
DOI: 10.1126/science.1251423

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Predicting Responses to Drought

The U.S. Corn Belt accounts for a sizeable portion of the world's maize growth. Various influences have increased yields over the years. Lobell et al. (p. 516; see the Perspective by Ort and Long) now show that sensitivity to drought has been increasing as well. It seems that as plants have been bred for increased yield under ideal conditions, the plants become more sensitive to non-ideal conditions. A key factor may be the planting density. Although today's maize varieties are more robust to crowding and the farmer can get more plants in per field, this same crowding takes a toll when water resources are limited.

Abstract

A key question for climate change adaptation is whether existing cropping systems can become less sensitive to climate variations. We use a field-level data set on maize and soybean yields in the central United States for 1995 through 2012 to examine changes in drought sensitivity. Although yields have increased in absolute value under all levels of stress for both crops, the sensitivity of maize yields to drought stress associated with high vapor pressure deficits has increased. The greater sensitivity has occurred despite cultivar improvements and increased carbon dioxide and reflects the agronomic trend toward higher sowing densities. The results suggest that agronomic changes tend to translate improved drought tolerance of plants to higher average yields but not to decreasing drought sensitivity of yields at the field scale.

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