Crop production is dependent on soil fertility, precipitation, temperature regimes, inputs such as fertilizers and irrigation, and management decisions such as planting date and hybrid selection. Several recent studies have revealed the effects of climate change on agricultural yields, highlighting how recent temperature trends during the growing season may have contributed to previous yield increases in the U.S. However, the recent 2007 IPCC 4th assessment highlighted how agriculture could be severely impacted by continued global warming without adaptation. Improvements and changes in technology and farm management (e.g., hybrid selection and planting date) may serve as adaptive measures that may partially or completely offset the unfavorable effects of climate change on crops. In contrast, other improvements in management such as irrigation across the Great Plains have placed crop production on a precariously high shelf to fall down from if water shortages occur. Consequently, a complicated picture is created when climate and management are considered together as important controls on productivity. In this presentation, I will synthesize the results of recent findings and use a retrospective analysis to illustrate how changing climate, irrigation, and crop planting dates have impacted agricultural productivity across the U.S. Corn Belt states over the last several decades. More specifically, I will use a case study performed for the state of Wisconsin to show how recent climate change and variability has already impacted corn and soybean yields, and hypothesize how projected climate changes may affect crop yields in the near future across the region.

Results/Conclusions

There are several key conclusions that will be illustrated as part of this work. First, irrigation has led to 50% increases in yields across the Great Plains compared to rainfed crops, and has also significantly reduced interannual variability. Crop yields in the Corn Belt appear to benefit from cooler and wetter growing conditions during July and August, and extended growing season length across the more northern regions appear to help support higher productivity. Planting dates of the key crops (corn and soybeans) have generally become earlier by about two weeks since the late 1970s, and have potentially contributed to corn yield increases of between 20-50% during this same period across several states.