College of Agriculture

Grain Crops Extension

Dry Weather and Corn Yield Losses
Chad Lee, Extension Agronomist, Plant and Soil Sciences

We started off with a really good growing season but now some corn leaves are rolling and farmers want to know how much damage is done. Over the last month, most of Kentucky is about 2 to 3 inches behind on precipitation.

Most of the corn in Kentucky is pollinated. Lack of water will hurt seed fill at this point, but ear length, row number and seed number have already been determined. It is possible for a few ovules to abort. Timely rains will help seed development go well and this corn has a good chance of making good yields.

If corn is pollinating during the dry spell, then poor pollination is a concern. The dry conditions accompanied by the hot weather causes silks to dry out quickly and prevent pollen from nicking the silks. The saving grace this season was that some of the mornings were relatively cool and pollen drop is usually heavier in the mornings and evenings. If pollination is poor, then recovery is difficult and yields could be severely hurt in these fields.

You can do a simple test to determine if pollination is complete for an ear. Remove the ear from the stalk. Gently cut the husks with a sharp knife. Make an incision the length of the ear. Turn the ear over and make a second cut the length of the ear. Try to cut only the husks and not the ear. Gently pull the husks away from the ear, being very careful not to remove silks. Then grab the ear by the shank and gently shake the ear. Silks should fall away if pollination has already occurred. Silks should stay attached if pollination has not occurred. This test may take some practice so check several ears.

Some of the late planted corn is approaching pollination. These corn plants could have smaller ears by having shorter row lengths and fewer rows per ear. Even with smaller ear size, the corn could rebound if we get rain for pollination and seed fill.

The million dollar question is how much yield is lost from the dry weather. The answer varies from field to field, but overall we still have potential to have trendline yields.

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