Agronomy Talk

Agronomy Update

How Stressed Did Your Corn Get?

Published on Wednesday, July 20, 2016

The stressful growing conditions we experienced over the last month are in the rear view and we are wrapping up what has been an ideal period of weather during pollination. But many are wondering how does drought and extreme heat (similar to what we’ve experienced) affect corn during its vegetative growth stages? For the sake of being objective, let’s take a look at a reliable resource to determine how critical the hot, dry conditions were to your area. Below are the weekly maps published by the University of Nebraska- Lincoln. You can also find them here.


June 14, 2016

June 21, 2016

June 28, 2016

July 12, 2016

After looking at these maps, it is clear that we had an extended period of dry weather throughout the vegetative growth stages of our corn. Add in the stress due to excessive heat (temperatures over 86 degrees are stressful for corn) and we have an atypical period of weather that is bound to have impacted our crop. If you look carefully, you may see differences across different parts of Iowa, especially on more drought prone soils. In these areas I have seen shorter plant heights and reduced leaf area. However, the development of the corn plant has not been slowed but, in fact, the phenology or crop staging is tracking ahead. This translates to less leaf area to harness sunlight as well as fewer days to photosynthesize and produce grain. 

We all know Iowa weather is erratic, so quantifying this information is a tall order. According to a modeling project called the Forecasting and Assessment of Cropping Systems (FACTS) at Iowa State University, it is possible we could see a yield reduction of approximately 24 percent in parts of southeast Iowa compared to the historical average. Iowa State University’s FACTS indicates that the average for all six sites across the state is an 8 percent reduction in yield as compared to the historical average. Nevertheless, a lot of growing season still remains and I believe we are coming off a better than average pollination with a promising weather forecast heading in to grain fill.






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Greg Shepherd

Greg Shepherd

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