Early spring flooding across much of the western Corn Belt was widespread and damaging. At the ninth annual Nebraska Grazing Conference Aug. 12-14 in Kearney, Neb., the 170 participants included many who had suffered flood damage to pastures and farmland or were working with those who had.
University of Nebraska-Lincoln Extension forage and crop residue specialist, Daren Redfearn, addressed what has been and remains an overwhelming situation for many. He covered the challenges of managing sand deposits after the flood in the conference’s opening session.
At the time of the March flood, few perennial plants had broken winter dormancy.
“The major obstacle from this event was sand deposits of varying depths, along with erosion and crop residues left on acres and acres of grazing land and cropland,” Redfearn said. “The amount of sand remaining after the water receded was not expected and the depth in some areas prevented removal to enhance forage and pasture production and slowed recovery.”
The sheer magnitude of the flooding was unprecedented and those impacted had no decision-making or management guidelines to draw from, he noted. As the spring went on, new programs and modifications to conservation programs were explored, but producers and specialists were dealing with many unknowns.
“With a few exceptions, perennial grasses and legumes are more flood-tolerant than annual grasses and legumes, with recovery dependent on forage species, plant growth stage and length of flooding,” Redfearn explained.
In areas where sand deposits were less than two inches, most perennial forages were able to produce new shoots and tillers, and light tillage or spreading could be used if needed. But deeper deposits suffocated those grasses and resulted in substantial stand loss, he noted. “Sand deeper than 8 inches is a bit of a ‘No Man’s Land,’” Redfearn said. “No one has been around this type of devastation in this lifetime.”
Mechanical removal of the sand is a possibility, but depending on the depth could be cost prohibitive, noted Redfearn. Revegetation might be an option on heavier sand deposits if they can be stabilized and organic matter can be added to bring pastures back into production.
“Revegetating heavy sand deposits may require two years for sand stabilization and improving soil organic matter before planting perennial grasses during the third year,” he said. “A suitable cover crop, such as oats or other cool-season annuals, to stabilize the sand deposits and add organic matter.
“When revegetating flood-damaged pasture, especially those with heavy sand deposits, it is important to consider perennial forages that are adapted to sandy soils.”
One mixture suggested by Redfearn included smooth bromegrass blended with intermediate wheatgrass.
“This could be seeded in April or late August (if moisture is available). Oats may also help reduce weed competition during establishment,” he added.
Some suitable warm-season perennial grass mixtures adapted to sandy sites might be sand bluestem, sand lovegrass, prairie sandreed, little bluestem, switchgrass and Indiangrass planted in early May or during the dormant season. Again, planting oats to help reduce weed competition is also recommended.
“Forage plant response to a flood event is complex,” Redfearn noted. “Every stand will respond differently depending on the degree and duration of the flooding, the forage species present, stand age, pasture health and vigor, fertility level, stage of plant development at the time of flooding, and temperature.”
Researchers this summer have noted that perennial forage plants that were dormant or semi-dormant during the early spring floods had a reduced likelihood of flood damage.
“Generally, flood events are more common during late winter to early spring,” according to Redfearn. “These early season floods provide warm-season grasses a recovery advantage.”
Floods with standing water can be more harmful, he said, and likely lethal, than plants flooded by moving water.
“Severe damage is less likely for plants that have leaves and stems protruding from the water,” he explained. “During a flood event, oxygen uptake by plant roots is eliminated, or at least severely restricted. Living plant roots, even with dormant top growth, still require oxygen to remain healthy.”
The length of flooding will have huge impact on how grasses and legumes will recover. The specialist noted that native warm-season grasses have the greatest variation with Indiangrass tolerant of flooding for only three to four days and eastern gamagrass tolerant of flooding up to five to six week. Switchgrass, he added, has greater flood tolerance than big bluestem.
Smooth bromegrass can withstand over three weeks of flooding, while reed canarygrass and timothy can withstand six weeks or more when still dormant. Most perennial cool-season grasses can tolerate more than three weeks, with orchardgrass, Kentucky bluegrass, and tall fescue capable of tolerating flooded conditions for up to two weeks.
Alfalfa, on the other hand, is not very tolerant to flooding, but can withstand one to two weeks, he said.
The take home from the 2019 floods, according to Redfearn is the old adage, “Patience is a virtue.”
“Most perennial forages are resilient and can recover from flooding under good conditions,” he said. “Recovery depends on the survival and growth of existing plants. Pastures and forage that are well-managed often are the first to recover following an extreme weather event, including flooding.”
For those seeking additional information, Redfearn noted a good place to start is the website flood.unl.edu, which contains a lot of information developed over the last six months.
Barb Bierman Batie can be reached at email@example.com.