As farmers begin another year’s task of planting their corn crops into fields across the state, timeliness can play a big role toward optimizing their production.

It is important to get an early start on planting corn in order to reach the maximum yield potential and to be finished prior to May 10, when yields generally begin to decline, said Jim Herbek, grain crops specialist with the University of Kentucky College of Agriculture.

The most critical factor to planting corn is soil temperature, and since corn will not germinate below 50 degrees, it is risky to plant when soil has not reached this mark, he said. Generally, soils in Kentucky should be above that level in the west by mid to late March while in central Kentucky they generally are at that level by April 1. In eastern Kentucky , they reach that level by April 10.

Yet planting too late can mean yield reductions.

There is an ongoing research project at the University of Kentucky Research and EducationCenter in Princeton to update planting date information for Kentucky . There are five planting dates being studied beginning in early April and going into mid June, Herbek said.

Based on the average yields from four years’ data, corn should be planted by May 10 to attain optimal yield potential. Historically, research has shown farmers can expect a 1 percent per day yield loss for corn planted after that date.

The ongoing study at Princeton also is reviewing the economic yield benefits from using Bt corn hybrids, one that is resistant to corn borers, in late planted fields. Study data have shown a yield advantage in fields planted in mid to late May and even more yield advantage in corn planted into June, he said. More corn borer damage and lodging were associated with the non Bt hybrids in these later planting dates than with the Bt hybrids. No economic yield advantage was shown in April planted fields.

“Based on current corn planting dates, it appears corn should be planted by early May to ensure optimal yield potential and that Bt hybrids should strongly be considered for corn that is planted in mid May or later,” he said.

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