Effects of Climate Variability on Corn Yield in Eastern South Dakota (1950-2012)

Weather and climate have had major influences on crop production in the Corn Belt region of the United States during the past century. Characterizing climate impacts on corn yield is therefore a continued effort aimed at improving the technologies and management strategies of farming. South Dakota is one of the major corning producing states in the United State, with a place in the top ten corn producing states and accounting for 535.3 million bushels of corn in 2012. In this study, the effect of growing season climate conditions (June, July, and August (JJA) total rainfall and July maximum air temperatures) on corn yield in Eastern South Dakota were examined using long term (1950 – 2012) data set. The study also investigated the trend and variability of corn yield at long term (1950 – 2012) and decadal (50’s, 60’s, 70’s, 80’s, 90’s, and 00’s) time scales, and the impact of irrigation and drought on corn yield at county level over the study period. County level corn yields were obtained from the United States Department of Agriculture-National Agricultural Statistics Services (USDA – NASS) website and climate data from National Weather Service Cooperatives (NWS COOP) stations. Results of the study showed that June, July, and August (JJA) total rainfall was positively correlated with corn yield. However, too much rainfall was found to limit corn yield as negative correlations were observed in the 90’s which turned out to be the wettest decade. July maximum air temperatures above 30°C (86°F) were found to suppress corn yield. These results suggested a nonlinear relationship between corn yield and the climate variables. Yield gap between irrigated and non-irrigated fields were highest in dryer counties in central and western parts of Eastern South Dakota. Drought was confirmed to negatively impact corn yield as most counties experienced over 20% drop in yield in 2012 due to the drought condition. Even though these results pointed to primary meteorological factors influencing corn yield, some questions remain including better adaptions to environmental stresses by newer corn hybrids