Elmore ran this "audience participation" exercise with the remaining five groups of people gathered at the field day—with bags of ear corn labeled Groups 2, 3, 4, 5 and 6. These were all the same hybrid, but planted at different dates. Group 1 was planted April 29, Group 2 planted May 8, Group 3 was May 13, Group 4 was May 23. Group 5 was planted in early June and Group 6 was June 18.
You can use this system to figure the odds of the corn in your fields reaching maturity before first killing frost
THE BOTTOM LINE: You can figure the odds of the corn in your fields making it safely to first frost. In the example exercise Elmore conducted with us at the ISU field day, our Group 1 corn should make it to frost OK. Same goes for the Group 2, Group 3 and Group 4 corn—assuming the average date of the first killing frost in 2013 comes no earlier than normal.
However, the ears in Group 5 and Group 6 aren't going to make it—unless frost occurs later than normal, Elmore noted.
Physiological maturity (R6 stage of growth) is the point when maximum kernel dry matter occurs—normally around 35% grain moisture, says Elmore. That's when corn is safe from frost; corn doesn't put any more dry matter or "yield" into those kernels once the corn reaches maturity. And contrary to what some people think, says Elmore, kernels do not lose dry matter after they've reached physiological maturity.
The critical issue for this whole 2013 growing season will be the timing of the first killing frost (28 degrees F) this fall. "A later-than-normal frost encourages a longer kernel-fill period and higher yields," notes Elmore. "And what happens if there's an early frost? Well, let's hope it doesn't happen!"