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Silks Must Come Out on Time

Silks Must Come Out on Time
Drought stress can delay silk emergence.

This may be a year when corn specialists and researchers learn a lot. Unfortunately, some of what they learn may relate to what happens to silk emergence and fertilization of corn kernels under unusually hot, very stressful conditions.

Timing will be everything as the pollination process unfolds. Many times, corn would be ending or past the critical phase by now. However, this year, most fields are reaching pollination at best. And they're doing it in the middle of the biggest heat outbreak in Indiana in two decades.

Actually, that last heat outbreak this severe was in 1988. Corn yields were way down that year, but 1988 was different. The heat was not accompanied with humidity, notes Ken Scheeringa, of the Indiana state climate office, and the heat was worse earlier in the season, such as in June. There was actually a break starting in late July that year. However, since the spring was very dry, crops were planted and already pollinating or pollinated before the drought ended.

This time, it was wet early, and now corn is showing signs of stress. What happens will depend on which days corn pollinates. If you catch a break and temperatures are hot, but hot at 88, not 98, pollen shed may be more normal.

The question is whether silks will be there. They tend to emerge late if there is drought stress, notes Bon Nielsen, Purdue University corn specialist. And silks only stay fertile for about 10 days. When they first emerge, they are more receptive to pollen. Being receptive to pollen grains which will lead to fertilization decreases as the silks grow older.

There have been years in the past when silks emerged late. What you tend to get is irregular kernel set, since all pollen isn't released at the same time. When it's most severe, most of the pollen grains have been released before most silks emerge. That can produce ears with kernels missing. Sometimes you can track weather changes b looking at cobs where kernel set isn't complete, and determining what the weather was like when that part of the ear was pollinated.

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