Recent advances in understanding the role of the El Nino- Southern Oscillation (ENSO) in climate variability present opportunities for improving efficiency in agricultural production. We investigated the relationships between ENSO, climate and maize yields in the U.S. cornbelt, using both observed data and crop simulations. Using a time-series of sea-surface temperature anomalies (SSTA) from the NINO3 region of the Pacific Ocean and historical records of temperature and precipitation spatially averaged across 51 mid-western climate divisions from 1950 to 1995, we ran linear correlation tests at three different lags. Northern hemisphere wintertime SSTAs were significantly correlated with air temperature at the 95% level of confidence in both the previous (r = -0.32) and following (r = 0.41) summer, but had opposite signs. Correlations with precipitation were significant only in the summer preceding the ENSO event (r = 0.31). Detrended maize yield for the same area and time period was also significantly related to SSTAs in the winter after harvest, with a correlation coefficient of 0.39, indicating that ENSO accounts for approximate to 15% of interannual maize yield variability in the cornbelt. Crop growth simulations at seven sites across the region suggest that water stress in July and August is the primary cause of lowered corn yield in La Nina years, but shortened grainfill period due to higher temperatures is also important. The benefits of El Nino-related rainfall and cooler temperatures are less pronounced than the negative impacts of warmer and dryer La Ninas. However, advance warning of both ENSO phases may present opportunities for improved crop management in the cornbelt. Copyright (C) 1999 Royal Meteorological Society.
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