Average recommended planting dates for corn in Iowa lie between April 12 and May 18 in order to achieve 98-100 percent yield potential, but this varies a bit on the specific location (Abendroth and Elmore, 2010). Currently, Iowa soil temperatures range from approximately 57-63°F (Iowa Environmental Mesonet, 2013). While these temperatures are often considered good for planting because 50°F is the temperature necessary for corn seed germination, the weather forecasted is not ideal for a corn seed to germinate and begin emergence. According to NOAA, Story County highs May 2 and 3, 2013, will be in the low 40s°F with lows in the mid 30s with potential rain, sleet and snow. Last year, on April 26, Iowa soil temperatures ranged from 58-64°F; however, by April 29 soil temperatures dropped to 49-53°F across the state. This swing in temperatures, coupled with rain at that time, resulted in many reports of lower relative yields for corn planted between April 22-26 than corn planted later. Fluctuations in soil temperatures are related to deformed mesocotyl growth, which can result in “corkscrewed corn” (Nielsen, 2012).
Iowa State University
Pierson, Warren L. and Elmore, Roger W., "Weather Forecast Delays Corn Planting, but Late Planting Does Not Foretell Lower Yields" (2013). Integrated Crop Management News. 70.
Figure 1. Deviation from Iowa corn 30–year yield trend compared to percent of corn acres planted by April 30. 1993 was removed as an outlier with 0 percent of acres planted by April 30 and a yield deviating from trend line by -39 percent.
20130502-PiersonW-WeatherForecastDelays-Figure2.pdf (220 kB)
Figure 2. Deviation from Iowa corn 30–year yield trend compared to percent of corn acres planted by May 15. 1993 was removed as an outlier with 7 percent of acres planted by April 30 and a yield deviating from trend line by -39 percent.
20130502-PiersonW-WeatherForecastDelays-Figure3.pdf (218 kB)
Figure 3. Deviation from Iowa corn 30–year yield trend compared to percent of corn acres planted by May 15.
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