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How does high water affect the young 2007 corn crop?

Agriculture.com Staff 05/10/2007 @ 9:02am

Heavy rains in the Midwest have river levels -- some at or near where they were during the flood of 1993 -- turning some fields, planted or not, into swamps.

For those corn farmers who have been able to get the 2007 crop planted, they now may face the dangers that high water can bring. This could mean either yield reduction or plant death. How can you gauge crop flood damage, and what are some ways to protect from it?

The storm system that swept through the Plains and Midwest last weekend brought enormous rainfall amounts. In northeast Kansas, southeast Nebraska and northwest Missouri, rain gauges showed anywhere from eight to 13 inches of rain from Saturday to Monday.

"It's been since 1993 since we had that much," Ken McCauley, a White Cloud, Kansas, corn farmer and current National Corn Growers Association president tells Agriculture Online. "Saturday night, it just rained all night. We had places around here that had 11 or 12 inches, and just west of here, in one area, it was around 13."

McCauley adds that Missouri River levels in his area on Tuesday were approaching 30 feet, with some areas at or above where they were during the 1993 flood. "It's really bad," he says. "People were emptying their bins out like mad -- they thought they were going to get closed in. It's just a lot of water."

HIGH WATER'S EFFECTS ON YOUNG CORN
These rising tides can have an array of effects -- from slight yield drag to total plant death -- on a newly planted corn crop. The damage potential is especially high early on in the plant's growth cycle and with warmer temperatures, according to University of Wisconsin corn agronomist Joe Lauer.

"Within about 48 hours, the oxygen supply in a flooded soil is depleted. Without oxygen, the growing point cannot respire and critical functions are impaired," Lauer says. "If temperatures are warm during flooding (greater than 77 degrees Fahrenheit) plants may not survive 24 hours. Cooler temperatures prolong survival. If flooding in corn is less than 48 hours, crop injury should be limited."

But, with continued exposure to water, which blocks oxygen from the seeds and plant tissue, plant respiration can be blocked. If over prolonged periods, this can be fatal to young corn plants.

"It is relatively easy for oxygen to diffuse into soil when pores are filled by air, but oxygen does not easily diffuse in water so the main constraint to oxygen movement is the thin water film surrounding root hairs. This boundary is magnified in flood/pond conditions," according to Lauer. "Roots are injured if the soil remains waterlogged. Continued poor aeration causes cell death and even death of roots."

Once water recedes, both in the short and long terms, damage to the crop can be easily observed. "To confirm plant survival, check the color of the growing point. It should be white to cream colored, while a darkening and/or softening usually precedes plant death. Also look for new leaf growth three to five days after water drains from the field. Once the growing point is above the water level, the chances of survival improve greatly," says Lauer. "Even if flooding doesn't kill plants, it may have a long-term negative impact on crop performance. Excess moisture during the early vegetative stages retards root development. As a result, plants may be subject to greater injury later during a dry summer because root systems are not sufficiently developed to contact available subsoil water."

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