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Drought puts pollination in jeopardy

Agriculture.com Staff 07/02/2012 @ 2:23pm

This year’s corn needs rain and needs it soon.
 
The next couple weeks are critical for corn pollination, because silk growth and tassel pollen-shed must be in sync to create corn kernels. That coordination relies on water.
 
“Silks are at least 99 percent water, and they use it as the driving force to elongate from inside the husk until they emerge outside the husks, or about 10 inches,” said William Wiebold, professor of plant sciences in the University of Missouri College of Agriculture, Food and Natural Resources. “If the pollen sheds from the tassel and the silks aren’t there, no kernels are produced.”
 
Silk growth is only half of the critical pollination process. If the pollen does reach the silk, a tube created by the pollen grain must be able to grow down the silk to where the kernel will be, Wiebold said. There has to be enough water to keep the corn silk wet enough for the pollen tube to grow through its entire length to reach the ear.
 
This coordination process, colloquially called nick, is so important that if dry, hot conditions prevent it, you could see a 30-40 percent yield loss, Wiebold said.
 
A typical ear will have 12 to 14 rows, each with 35 to 40 potential kernels, he said. Lose just three kernels per row and that’s a substantial yield loss.
 
The lack of rain is having other negative effects on corn. Normally, corn tasseling occurs when plants are 7, maybe 8 feet tall, Wiebold said. Water pushes that growth.
 
“There are reports coming from throughout the state that corn is tasseling at 5 1/2 to 6 feet tall,” Wiebold said. “That’s a couple of feet shorter than normal, and it’s because there’s wasn’t enough water to increase plant cell size.”
 
Corn leaf blades are coming in smaller for the same reason. All these stresses put this season’s corn yield in question.
 
“Probably the next two weeks will really determine what our yield will be,” Wiebold said. “Some places that had rain, like northwest Missouri, will see less yield loss. Places like St. Charles County and along the rivers, which have deeper soils with good water-holding capacity, should also experience less yield loss.”
 
Places that have seen little rain, have claypan soils or have compacted soils will experience large yield losses if rain doesn’t come soon. A heavy yield hit in the Corn Belt could send ripples through the futures market.
 
“The Chicago futures market will start calling around to the states to see what the weather is like,” Wiebold said. “It’s really important and it can drive the market price that farmers will receive.”
 
Less corn produced would mean higher prices, putting pressure on livestock producers who feed corn. At the end of this food chain, consumers could see sticker shock for meat and dairy products.

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From an Ohio Guide 07/03/2012 @ 7:42pm From the two weeks before through the two weeks following pollination, corn is very sensitive to drought, however, and dry soils during this period may cause serious yield losses. Most of these losses result from pollination failure, and the most common cause is the failure of silks to emerge from the end of the ear. When this happens, the silks do not receive pollen; thus, the kernels are not fertilized and will not develop. Drought later in grainfill has a less serious effect on yield, though root function may decrease and kernels may abort or not fill completely. Table 4-2: Effects of Drought on Corn Yield During Several Stages of Growth.* Stage of Development Percent Yield Reduction Early vegetative 5 to 10 Tassel emergence 10 to 25 Silk emergence, pollen shedding 40 to 50 Blister 30 to 40 Dough 20 to 30 * After four consecutive days of visible leaf wilting. Source: Claassen, M. M., and R. H. Shaw. 1970. Water deficit effects on corn. II. Grain components. Agron. J. 62:652-655.

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