Agronomist: Too Dry for Successful Pollination

July 5, 2012 05:28 AM

University of Illinois crop sciences professor Emerson Nafziger says water stress and loss of yield potential continues to gain momentum as the crop across the state pollinates. And in southeast Illinois, some fields are dead.

"The fact that lack of water for growth is causing tassels to struggle to emerge may have negative consequences for pollination," notes Nafziger. "Pollen is shed as relative humidity drops, so exposed tassel branches usually start to shed 2 to 3 hours after sunrise. If the tassel is wrapped inside two leaves, relative humidity stays high longer, delaying pollen shed by as much as several hours."

"In some fields, more pollen is being shed in early afternoon than in the normal mid-morning period," said Nafziger. "The problem comes when the temperature is above 90 degrees when the most pollen was being shed. At such temperatures, silks are often not as receptive as they would have been at 70 to 75 degrees earlier in the day."

Even in fields showing silks and tassels, fertilizing kernels and keeping them going until grainfill begins may not be fully successful in the drier fields. Moreover, as large areas of the state suffer from lack of rain, the number of kernels fertilized may end up being considerably larger than the number that survive to fill and produce yield. "We remain optimistic that kernel numbers will be OK in many fields, but in the past two years we have had a great deal of kernel abortion, and there is every reason to believe that this will recur in 2012," Nafziger said.

"It’s highly likely that there will be fewer than normal numbers of kernels by the time kernel filling starts several weeks from now," Nafziger predicted.

Many producers are trying to guess how much corn yield potential has already been lost. In the majority of fields -- those that are pollinating now or that will be pollinating in the next week under conditions of at least moderate stress -- the first yield potential estimates will have to wait until it is possible to count kernel numbers and get some idea of grainfilling conditions at stage R3 (roasting ear) during the last third of July.

"I wish we could be more optimistic," said Nafziger. "The start to the growing season was outstanding, and most producers ‘did everything right’ to establish good yield potential. There’s not much we can do other than accept that the weather is beyond our control."

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