NEWS
Rain, Rain, Go Away
Emily Unglesbee DTN Staff Reporter
Mon Jun 22, 2015 12:07 PM CDT
(Page 1 of 2)

ST. LOUIS (DTN) -- Scott Meadows' northwestern Missouri fields haven't been this wet in nearly 20 years.

Cutline: Heavy, persistent rainfalls in much of the Midwest have endangered some corn and soybean crops this year. (DTN photo by Pamela Smith)

"We're just trying to survive right now," the Mound City, Missouri, farmer told DTN. "It's been raining nearly every day."

Meadows' region saw between 9 and 10 inches of rain in May -- twice the monthly average -- and the skies haven't let up yet in June, either. He managed to finish planting most of his soybeans around June 10, a full month behind normal. Now he is eyeing his waterlogged fields with concern, as patches of yellow and stunted plants dot his corn fields and young soybeans struggle to get a start.

Many Midwest farmers are facing flooded and saturated fields, which put corn and soybean plants at risk for plant death, poor crop development and disease this year, agronomists told DTN. Missouri and Michigan farmers are facing more than 50% surplus topsoil moisture, while fields in Illinois and Indiana log in around 40%, according to the most recent USDA crop progress reports.

Short of concocting anti-rain dances, growers' best option now is to strap on their mud boots and head into the fields to assess crop survival and condition and evaluate the need for future nitrogen applications, agronomists said.

ASSESSING THE DAMAGE IN CORN

For corn plants, three factors will drive potential crop damage: the plants' developmental stage, the duration of the ponding or soil saturation and the air temperature, Ohio State University agronomist Peter Thomison explained.

"After plants reach the 6-leaf collar stage, they are pretty safe from long-term flood injury," he said. "When a plant is younger than that, it's more vulnerable, especially if it has emerged only shortly before."

Plants younger than V6 still have their growing point below ground and can only survive two to four days in saturated soils, he added. When air temperatures near 80 degrees, corn respires faster, so the flooded plants use up their available oxygen too quickly and crop damage worsens.

"They start declining very rapidly," Thomison explained. "The carbon dioxide that builds up in saturated soil is toxic to the roots, and as the plants begin to shut down, they become more susceptible to rotting."

When a field dries out enough to scout, growers can pull up plants and cut open the growing point to assess its chances of survival. Firm, white tissue means the plant is still alive and well; mushy brown tissue means the plant is likely to either die or be unproductive, Thomison said.

Even when flooded corn plants survive, they can face an uphill battle the rest of the season. Excessive rainfall in the early vegetative stages produces shallow root systems that are ill-equipped to feed the plant in the hotter, drier days of late summer, Thomison said.

Because root systems are very sensitive to temperature, roots that take up residence in the top few inches of the soil can also suffer from overheating, which limits their function. Too-shallow roots can also cause plants to topple over during wind events later in the season.

Finally, the soils around young corn plants that have not yet established a canopy are more vulnerable to pounding rainfalls and can crust over when they finally dry out, Thomison added.

Going forward, corn growers should be on the lookout for diseases that thrive in flooded fields, such as crazy top, pythium, and corn smut, he warned.

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