2009, 2010 Set the Outer Boundaries on Corn Maturity

The lines are so far out on either side they're almost 'outliers'.

Published on: Dec 20, 2010

In the world of graphs and statistics, a number in a plot of numbers, say from a yield trial, that is so far off the chart that it's obvious something was wacky with that number is called an 'outlier.' The early precision farming engineers who studied how yield monitors work are very familiar with outliers. Every once in a while a number, at least in the early days, would come across the file that was supposedly a correct reading, but which was way off the charts. If there's only a few of those, normally statisticians throw them out of the data set and note in the footnotes or margins somewhere that there were a few outliers on either side of the curve.

All this is to say that the graph of corn maturity running into August, September and October for the Midwest over the past five years has an average curve, right up and across the middle of the graph, and one so far right it's almost off the chart, and one so far left it's almost off the chart. The far right one represents 2009, when corn literally didn't black layer until very late September or early October. The far left one is 2010, where corn black layered in late August or very early September, roughly a month apart.

Only one other year, 2004, approaches being as fast in maturity as 2010. Some would call 2010 and 2009 the extremes of what's possible, if not outliers. Some wise, old researchers say they like to have a good year and a bad year on the extremes in two years of research- then they know everything else is in the middle. Then 2009 and 2010 should be a researcher's delight, especially if what they were doing was at all related to when corn matures.

Bob Nielsen, Purdue University corn specialist, showed the graph to certified crop advisers form across the Midwest last week. He noted that it was strictly a heat response. Growing degree days ran weeks behind in 2009, and weeks ahead in 2010. Corn maturity responds strictly to growing degree days, unlike soybeans, where the length of the night is a factor in affecting when flowering starts.

In years like 2009, black layer maturity moisture was likely at the upper end of the 25 to 40% range given for moisture content at maturity, Nielsen says. This year, it was at 25%.

He was able to clear up one myth, however. Some have proposed in the past that there are conditions where corn never black layers, such as in a real late season like 2009, after hail hits or during a frost. "That's not true," Nielsen says. "It always produces a black layer. What the layer is are the placenta cells from the embryo that form together and close the kernel so no more starch can enter. Whether conditions are good or bad, there will always be a black layer."