There is not a lot of good news for the 2012 Illinois corn crop, but there has been recent rainfall in some places, and 46 percent of the crop was silking by July 1, far earlier than normal. Silks are abundant, and leaf color remains good in fields where plants have had enough water to get to a height of 5 feet or more.
“The early start to pollination is a very positive development, and the fact that even in dry areas the root system has managed to find enough water to get to this point bodes well,” said University of Illinois crop sciences professor Emerson Nafziger.
Unfortunately, the serious problem of water stress and loss of yield potential continues to gain importance. “As we continue without rain over most of the state, we expect this only to worsen,” he predicted.
The worst news is that there’s little hope for some fields, especially in southeastern Illinois. “The plants in some fields are dead. If they are alive but past the pollination stage with very short plants and no kernels, or they have lost most or all of their green color, there’s no chance that they can come back,” Nafziger explained.
Only 26 percent of the crop was rated good-excellent on July 1. Barely 10 percent of the acreage has adequate topsoil moisture. Temperatures remain high, and warm nights continue to push GDD accumulations above normal, although the statewide GDD accumulation since May 1 is only 135 above average.
The fact that lack of water for growth is causing tassels to struggle to emerge may have negative consequences for pollination. 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.”
“We also expect that silk numbers may lag due to water shortages,” he continued. “If plants are struggling to take up enough water to push tassels out above the leaves, we can expect silks to struggle as well, at least those that emerge late.”
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.