Midwestern Corn Yield and Weather in Relation to Extremes of the Southern Oscillation

Abstract

Weather and crop yields in the Midwest have exhibited wide fluctuations during the past 10 yr. Sea surface temperatures (SST, El.Nino and its counterpart, La Nina) have been related to or blamed for these weather abnormalities via teleconnections. Yield, weather, and El Nino related (southern oscillation index - SO) data beginning in 1900 were assembled to determine if significant relationships could be ascertained. Midwestern weather and corn (Zea mays L.) yield data were coded relative to the SO. The SO groupings were 0.8 (La Nina like, high phase), and in between. Yields were grouped >10% or <10% relative to expected, or in between. Corn yields exhibited wide variation when the SO was in between, indicating that weather factors other than SO influenced corn yield during those oceanic conditions. However, when summer SO was in the high phase (low phase), there was a statistical tendency for corn yields to be lower (higher) than expected, respectively for all Corn Belt states studied, except Missouri The low (high) phase of the SO is generally related to El Nino (La Nina). During the low (high) phase of the SO, much of the Corn Belt received more (less) rainfall in July, August, and September. At the same time, high temperatures-or heat stress-were generally lower (higher) during the low (high) phase of the SO. Both high (but not excessive) precipitation and lower temperatures are associated with good corn yield. If El Nino forecasts improve as is expected, Midwestern corn yield forecasts should similarly improve.