Checking pollination success using the shake test may not be as accurate in determining the history of what happened in the field as counting the rings and size of rings on a tree stump in determining the history of the tree, but it can still be revealing. Odds are there will be some unusual patterns if you do the shake test on ears shortly after you think pollination has occurred. Wherever silks stay attached to the ear, fertilization of the ovule didn't happen. A kernel won't form there.
Bob Nielsen, Purdue University Extension corn specialist, uses the test to get a quick indication of whether pollination was successful or not. He's recommending that you spend some time in your fields this week, performing the simple test in a number of locations, to get an idea of what you can expect later on this season.
Here's an example we found ourselves. The field we visited was planted in early May on somewhat poorly drained ground. In this type of year, that's the ground that gets hard on the surface quickly. It is easy to compact, and soil compaction will show up this year since it's been so dry, especially in corn fields.
Many of the four-foot stalks were tasseling, but only some had ear shoots. Perhaps a third to a half had shoots. Odds are the other half won't have ears, unless the weekend relief that just occurred came in time while pollination was still happening. That's doubtful.
At any rate, we pulled an ear from one of the stalks that did produce a shoot and silks, and appeared to pollinate. When we unrolled the silk husks gently, and then did the silk test, we found an unusual pattern. There was an inch or so of silks on the butt end, then no silks, then more silks at the tip end.
Is there a possible explanation? Yes, here's one. The field started trying to pollinate just after the Fourth of July, when it reached 106 degrees in that area on Saturday, July 7. Then the temperature dropped 15 degrees. It didn't rain but it did cool off.Ears begin fertilizing and forming kernels at the butt and move up the ear. It's possible that as the ear started to pollinate, it was just too hot and those kernels at the butt didn't get fertilized. Then as it cooled off and pollen was still available, fertilization occurred in the middle part of the ear. It remains to be seen whether the tip kernels will pollinate or not.