The 2017 growing season for much of Iowa so far has been characterized by low rainfall and high temperatures. This has generated concerns about water stress and yield reductions. In particular, 2017 maximum temperatures are 2-6 percent above average and precipitation 4-75 percent below average (equivalent to 0.3 to 5 inches deficit) from June 1 to July 15 (Figure 1). Radiation is 5-15 percent above average across Iowa. Minimum temperatures and growing degree days (GDD) are below average in northern parts of Iowa and above average in the central and southern parts of Iowa. The 2017 weather pattern is not much different from the 2016 weather with the exception of rainfall during the 1st and 2nd week of July. High minimum temperatures are being experienced in July of 2016 whereas both minimum and maximum temperatures moderated in July of 2016. In terms of heat stress, 22 days out of the 45 days from the June 1 to July 15 period had maximum temperatures above 86oF in 2017. Heat stress becomes very important above 96oF as it negatively affects several crop morphological and physiological processes.
Iowa State University
Archontoulis, Sotirios and Licht, Mark A., "Evaluation of the 2017 Growing Season So Far" (2017). Integrated Crop Management News. 2438.
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