Short corn and variable growth in 2013
Soil temperatures this year fell below normal during the five weeks when most of Iowa’s corn was planted and considerably below what we experienced in 2012 (Figure 2). We speculate that abnormally cool 2013 soil temperatures affected corn internode elongation and thus resulted in shorter corn plants, especially those planted from April through mid- to late- May.
In addition, within field variations in plant heights seen in fields this year may be due to uneven residue distribution across the field. Differing residue levels alters both soil temperatures and soil moisture affecting corn growth and development. Other factors may affect within-field plant height variations as well.
Plant height itself is not necessarily a good indicator of corn yields if light interception is near complete at silking. As mentioned above though, if upper canopy leaf areas are reduced by the cool temperatures this spring, grain yield will be reduced. However, yield potential in 2013 is likely compromised by the delayed planting and possibly cool and wet soil conditions experienced early in the growing season. An early frost will be detrimental.
Cool, wet weather this spring reduced corn plant heights and increased variability of plant heights across fields. Shorter plants are not necessarily lower yielding. Whether corn is knee-high or elephant-eye high by the 4th of July is less important than whether the crop intercepts near maximum light at silking and the timing of the first major fall frost.