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Corn+Soybean Digest

Waterlogged Soybeans

Whether it's overflow from something as mighty as the Mississippi River or water from an isolated deluge on two or three farms, growers face tough decisions in determining whether or not to replant waterlogged soybeans.

Growers like Todd and Lynn Allen and their son John don't have much choice when the Mississippi turns their “Island 40” farm north of West Memphis, AR, into a lake.

“We often have to replant some fields,” says John, whose family took on government regulators to try and turn back floodwaters several hundred miles upstream.

But most growers facing underwater fields shouldn't automatically reload the planter hoppers with seed, says Stephen Kyei-Boahen, soybean researcher at the Mississippi State University Delta Research and Extension Center in Stoneville.

He says replanting decisions should be made based on the stage of plant growth when the floods occurred, plant density after the flood, replanting time, the varieties to be planted, weather conditions during the growing season and the cost of replanting.

“Soybeans can tolerate flooding for a short period with little injury observed or yield loss,” says Curtis Tingle, University of Arkansas Extension soybean specialist.

In Boahen's flood research at Stoneville, his team, which includes researcher Lingxiao Zhang, looked at the effects of flooding on common soybean varieties at two growth stages for various lengths of time. In one test, the researchers observed how pre-emergence soybeans flooded for 18 hours and 24 hours progressed through harvest.

In addition, Boahen flooded plants at the first leaf for 24 hours and 48 hours on plants at the first leaf stage. Then, at the third leaf stage, plants were counted in each test area. Plant height was also measured at the full pod stage.

“At harvesttime, we randomly selected 10 plants from each plot,” he says. “We then counted the number of pods per plant and number of seeds per pod, and determined the weight of 100 seeds at 13% moisture.”

Results of the tests indicated seeds that had not yet germinated were impacted most from the flooding.

“Once plants germinated and emerged, flooding had less effect on them,” says Boahen, noting that all varieties in the tests responded similarly to the flood conditions.

“We found that flooding before emergence reduced plant height, but plant height was not affected much by flooding at the first leaf stage,” he says. “Flooded plants had lower yields, but the differences were not significant. That's an indication that the plants recovered to some extent by producing more pods to compensate for a lower plant population.”

Todd Allen, whose farm sees flooding four out of every 10 years, knows that flooded beans can make some recovery. But his family takes no chances.

“If plants are underwater more than 24 hours, we feel they're stunted too much to recover,” he says. “Even after the waters subside, the soil is still saturated for another week. The plants will usually die from lack of oxygen to the soil.”

The Allens plant about 3,000 acres of soybeans each year. No-till soybeans are drilled into 7½-in. rows. They begin with Group IVs because of the strong yields varieties in that maturity level have produced. After May, they finish normal planting with Group Vs.

Most floods on their land come in March or April, usually after snow melts and early spring rain from northern states flow into the big river. But late flooding sometimes occurs in early summer.

“It's really unpredictable,” says John Allen. “In 2004 we received ‘lower water flooding’ that covered the lower portions of our fields. So we had to replant parts of the crop in the same fields. For early flooding, we can come back with Group IVs. But for late flooding, we come back with Vs.”

Replanting takes place up to July 15 if needed. “Most of Arkansas sees a half-bushel drop in yields for every day replanting takes place after June 15,” says Todd Allen. “But with our productive land, we can go until July 1 without losing yield. And we still plant until well into July to try and salvage a flood situation.”

The Allens don't grow corn. But for those whose cornfields flooded out, whether by a river, stream or just too much rain, University of Arkansas' Tingle urges precautions before replanting fields in soybeans.

“Since soybeans can be planted later in the season than most crops, many producers consider this option,” he says. “But remember, the No. 1 factor that could limit this practice will be the herbicide program used. Many of the herbicides used in corn, primarily those that are soil-applied, have specific re-crop restrictions.”

Controlling The Flood Gates

Many times it's not if farmland bordering the Mississippi River will flood, it's when. That is a price some growers pay for premium soils near the river.

After a completely unexpected, yet man-made surge in the mighty Mississip' flooded virtually every acre of the Allen farm north of West Memphis, AR, Lynn Allen started a mission to cut through the red-tape wrapped federal bureaucracy that had jurisdiction over flood gates several miles upstream.

It was in June 1998. There was no excessive upper Midwest rainfall, in a year more generally known for drought than drenching downpours. Still, after Lynn heard the local Army Corps of Engineers report that the river would flood substantially, there was immediate panic.

“There had been no forecast of this happening,” says Lynn, whose husband, Todd, and son, John, farm with her on land known as “Island 40,” located inside the river levee. “I called my husband and we agreed if that happens, we'd lose hundreds of acres of soybeans.”

She began her quest for an answer to why this was happening. “I was redirected to at least 10 people at the Corps of Engineers in Memphis (TN),” she says. “No one had an answer. I finally learned that the jump in the river (levels) was being caused by the opening of flood gates at Lake Barkley Dam and Kentucky Dam (in western Kentucky).” A series of lakes in that area were developed initially for regional flood control to generate electricity and for recreation. Those waters wound up in the Ohio River, much of which feeds into the Mississippi. The program was good for that region, but bad for farmers along the big river downstream in Missouri, Arkansas, Tennessee, Mississippi and Louisiana.

Lynn's goal was to stop the flooding from happening, or to at least obtain warning of flood waters far enough in advance for disaster planning. She contacted her Arkansas congressman, U.S. Rep. Marion Berry, himself a farmer. She also kept leaning on the Corps of Engineers and eventually was able to set up meetings with the agency's officials.

“We were surprised when we were told that no one had brought up this subject of flooding to the Corps,” she says, noting that other rivers-edge growers also got involved in the water fight.

Berry says the Mississippi River and Tributaries Project (MR&T), in which the Ohio flows into the Mississippi, was established in 1928. “It remains an engineering masterpiece,” he says.

He says Lynn's persistence in the flood situation helped solve some of the excess river flow problems.

“Had she not been able to present it in such a coherent way, I don't know if many of us could have figured it out,” he says. “She did a very responsible thing. They (the Corps) changed the operating plan and modified it to where water is being released differently. Water is released earlier in the year so growers can plant after the water subsides.”

Results of the vigorous campaign now enable the Allens and others to have a link to the Kentucky waterway. They know when any flooding will take place. There is also a much better line of communication among growers and government agencies.

Now, if flooding caused by quick striking gully washers could just be controlled.

“The Corps rules forbid building up levies on your farm,” says John Allen. “You just have to set back and let it go. That's the risk of farming here.”

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