4 Tips for Managing Flooded Fields
Last spring was the wettest in 100 years across much of the Midwest, just two years after major flooding in 2011. Coincidence?
No, wet springs are a confirmed trend. Excessive rainfall events have increased by 30% over the last 50 years, and most of those come in the spring, says Peter Motavalli, crop specialist at the University of Missouri.
“We deal with saturated or waterlogged fields or parts of fields every year,” he says. He poses this question: What can you do to better manage wet soils?
The University of Missouri (MU) has a unique research location with the ability to simulate flooded soils. Motavalli and Kelly Nelson, research agronomist at the university’s Greenley experiment farm, conducted a 2013 flooding simulation research trial. Flooding simulations on newly emerged corn included:
- One day
- Three days
- Seven days
The plots were partially submerged in 2 inches of water in mid-June.
One thing the researchers found was that three days of flooding vanished large amounts of nitrogen (N). This clipped yields between 10 and 30 bushels per acre.
“We put rescue N on after the flood and, somewhat surprisingly, had no real response to the rescue treatment,” says Motavalli. “But it didn’t rain much after we put the rescue N down.”
Still, he says, this work does show that corn has a tremendous tolerance for saturated soils. Even the corn that was flooded for seven days rebounded with yields within about 20 to 25 bushels per acre of unflooded fields.
“Corn has many adaptive traits,” Motavalli says. “As lower roots die in saturated soils, it will form surface roots to get oxygen. The stems will enlarge, and air channels will form in the roots to get air into the ground. Then you’ll see rapid root regrowth after the flooding.”
There are four tips to help your crops better cope with very wet conditions. Motavalli thinks you should learn about them, as it looks like the wet-spring pattern will continue.
1. Hybrid Selection
While there is much publicity about drought-tolerant hybrids, there’s been little research on breeding corn for flood tolerance, he says.
“We screened some cultivars to see if there were differences, and we found some,” he says. “We took two of the flood-tolerant hybrids to the field in our flood plots.”
Results are mixed. After seven days of flooding, one of the flood-tolerant hybrids had higher yields than the control hybrid, Motavalli says, by about 20 bushels per acre.
This system involves tilling narrow strips of soil where the corn rows will be planted. Residue and soil are left undisturbed between the 6- to 9-inch-wide strips, which are residue-free. The system is a compromise with no-till.
“Full no-till can result in wetter, cooler soils,” says Motavalli. “In strip-tillage, the strip dries and warms up faster, and you get better germination and seed emergence. If we plant 24,000 to 26,000 seeds per acre, we get 2,000 to 3,000 more plants per acre with strip-till compared to no-till.”
3. Managed Subsurface Drainage
This is a relatively new system of tile drainage. In a normal system, tile lines run free with no control of water discharge from a field.
In the managed system, slider baffles at the tile outlet control water flow. When they are in place, water flow from the field is restricted; when they are removed, it’s unrestricted.
“In the spring when we have lots of water, we take the sliders out to get as much water as possible out of the field,” says Motavalli. “When it’s dry, we close them to conserve water.”
It results in reduced nitrate loss by about half, he says. “Subsurface soil drainage gives lots of advantages and a typical yield response of 25% to 35%,” he says. “We see nearly double that response from corn with the managed system.”
4. Precision Agriculture
Often in a very wet spring, the entire field is not impacted. Rather, flooding occurs in zones. Precision ag lets you manage those areas as needed.
For instance, polymer-coated urea fertilizer slowly releases N as temperatures warm. If you apply N in potential wet spots of a field, it stays there through a flood episode, then it releases later.
“In a practical situation, I see applying regular urea in areas not prone to flooding, and flood zones would get the coated product,” says Motavalli.
Some tests have shown that the yield impact of the polymer-coated seed can be as high as 20 bushels per acre in corn.